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Biogeomorphology and biological soil crusts: a symbiotic research relationship

Biogéomorphologie et croûtes cryptogamiques : relations symbiotiques de la recherche
Casey Duane Allen
p. 347-358

Résumés

Constituées de nombreux lichens, mousses, algues ou cyanobactéries, les croûtes cryptogamiques (CC) constituent un écosystème microbien essentiel dans les régions arides et semi-arides. Leur structure et leur fonction ont fait l’objet de nombreuses recherches mais peu ont pris en compte leurs caractéristiques spatiales. La biogéomorphologie, en tant que discipline étudiant les interactions entre les formes de terrain et le vivant, permet de pallier sensiblement ce manque. Cet article se propose de souligner les apports cruciaux de la biogéomorphologie dans le domaine des CC et les pistes restant à explorer. Pour ce faire, sont rappelés les concepts de base des CC, la méthodologie d’étude habituelle issue des recherches écologiques et la manière dont la biogéomorphologie pourrait faire évoluer cette approche traditionnelle. Ensuite, après avoir rappelé l’apport de la télédétection pour la connaissance des CC, l’article montre comment la biogéomorphologie via sa contribution à la connaissance de la météorisation peut devenir une discipline fondamentale dans l’amélioration de la connaissance des CC.

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Notes de la rédaction

Article soumis le 23 novembre 2009, accepté le 24 août 2010

Texte intégral

Introduction

1For much of Earth's early history, the terrestrial surface hosted little more than the primitive plant life of algae, fungi, cyanobacteria (blue-green algae), and perhaps lichens (Budyko and Ronov, 1979; Berner, 1994; Berner and Kothavala, 2001). Found predominantly in arid and semi-arid regions, today’s analog of biological soil crusts (BSCs) contain various species of these same organisms. Interactions between BSC organisms and calcium-containing minerals were key to the habitability of Earth, as they led to the draw-down of carbon dioxide (Brady and Caroll, 1994; Berner, 1995). Mesozoic development of higher order land plants led to further reduction in carbon dioxide (Drever, 1994), and Miocene development of the Himalaya Mountains and the further evolution of plant life with C4 photosynthetic pathways reduced carbon dioxide enough to let earth cross over into the Pleistocene glacial condition (Molnar et al., 1993). Given their potential importance to early Earth and relatively unknown importance to global cycling related to today’s Earth - and while more studies related to cause and effect between landform and plants are being conducted (Bornyasz et al., 2005) - it is perhaps surprising that little research exists to answer a fundamental question of exactly how BSCs respond to disturbance in different geographic (spatial) contexts. BSCs are known to exist in nearly every arid and semiarid ecosystem in the world, and even in microclimates of some temperate regions; only evergreen rainforests climatic region lacks BSCs (Büdel, 2003). Yet BSC research, as an interdisciplinary field of study, is unable to articulate clear connections between spatial controls - specifically landform type and effects of BSC components on weathering rates - and initial responses to disturbance.

2This problem could be addressed at an infrastructural level in the field of biogeomorphology. In a 2002 special issue of Geomorphology, a review of biogeomorphology by L.A. Naylor et al. (2002) identified key research needs similar to those deficiencies facing BSC-related research described by J. Belnap and O.L. Lange (2003). These include: (i) expanding research to variable spatial and temporal scales; (ii) creating new approaches for modeling and devising assessment techniques that will link bioprocesses across the system; (iii) implementing a more holistic approach to studying biota-landform relationships; (iv) exploring the effects of multiple processes in shaping landforms; (v) bridging the disparity between short time scale biotic processes and longer scale landform processes and development; (vi) utilising new theoretical advances in geosciences. To help satisfy these deficiencies, L.A. Naylor et al. (2002) proposed an interactive and dynamic three-fold spectrum of how biota and geomorphology interact. This spectrum consists of “bioconstruction”, how biota construct or deconstruct landforms; “bioerosion”, how biota help or hinder landform erosion; and “bioprotection”, how biota protect and/or fail to protect landforms. One significant way to connect this biogeomorphological research triumvirate rests in the oft-overlooked, but extremely important science of weathering. While weathering studies abound in geomorphological research, few studies apply weathering science to BSC-related research. The overarching framework of this review takes guidance from this three-fold conceptual structure of identifying potential linkages of spatial aspects across landforms, while also taking into account the broader role of soil crusts in general (both biological and chemical) as noted by H.A. Viles (2008), and addressing identified gaps in the BSC literature related to spatial dynamics (Belnap and Lange, 2003). Indeed, as discussed in this article, perhaps weathering science is the missing piece - the “glue” - that connects biogeomorphology to BSC and BSC-related research agendas.

3Though it seeks to examine the overall important role biogeomorphology can play in regards to BSC research, this review paper supports a more specifically-focused agenda, arguing not only for using biogeomorphological techniques to study BSCs, but also advocating for studying the biogeomorphology of BSCs themselves. To that end, the first section focuses on how BSCs are studied from the traditional ecological point of view, and how the discipline of biogeomorphology stands ready to engage in and expand the usual techniques used in BSC research (i.e., those research endeavors with an inherent ecological focus). Next, after a brief overview of remote sensing (RS) as an assessment method, insight is offered into past and current RS-BSC research efforts, and how RS can be used to gain a better understanding of BSC biogeomorphology. Then, before concluding, the article offers a brief overview (because there is so little related research) of the anticipated significance BSC research can have on narrowing the present gap in BSC-related research agendas through the disciplines of biogeomorphology and weathering, including it potential for carbon sequestration.

Soil crusts studied with an ecological focus

4Found in every major arid/semi-arid biome in the world, biological soil crusts (BSCs) can account for up to 70% of the ground cover in some of these areas (fig. 1). Despite their inherent presence in desert biomes, BSC research tends to focus on three research questions: (i) Composition, i.e. what kinds of creatures live in the BSC; (ii) Nitrogen fixation, i.e. how BSCs fix atmospheric nitrogen in the soil to promote higher plant growth; and (iii) Disturbance recovery, i.e. how BSCs recover from disturbance, primarily focusing on recovery from grazing. This section demonstrates that the literature on BSCs is remarkably rich with ecological insights, focusing on processes and nutrient cycling (particularly nitrogen), creating an ecologically-important symbiotic soil-plant-atmosphere relationship (Rychert and Skujins, 1974; Harper and Pendleton, 1993; Brady and Weil, 2008). Some of this literature also focuses on BSCs’ roll in reducing soil erosion by binding “loose” soils together and aiding in water retention and dispersion (MacGregor and Johnson, 1971). Meant as no criticism to the researchers focusing first on an understanding of these processes, the relationships of BSCs with respect to landform distribution, (micro)climate, and weathering have not been aggressively pursued (Belnap and Lange, 2003). The discipline of biogeomorphology can fill two specific gaps in BSC-related literature. First, BSC-related studies include a lack of comparative landform-climate studies “specifically” over large areas, “without” using ground cover and/or soil texture as surrogates (e.g., expanding study areas to larger than single landform-sizes, such as a dune field or catchment basin). Second, studies that relate BSCs to weathering rates, mechanisms, forms, and processes are few and far between.

Fig. 1 – Biological soil crusts as dominant ground cover in an arid, badlands-topography biome, Grand Staircase-Escalante National Monument, UT (USA).
Fig. 1 Les croûtes cryptogamiques comme couverture dominante des sols au sein d’un biome aride et à topographie ravinée, Grand Staircase-Escalante National Monument, Utah (Etats-Unis).

Fig. 1 – Biological soil crusts as dominant ground cover in an arid, badlands-topography biome, Grand Staircase-Escalante National Monument, UT (USA).Fig. 1 – Les croûtes cryptogamiques comme couverture dominante des sols au sein d’un biome aride et à topographie ravinée, Grand Staircase-Escalante National Monument, Utah (Etats-Unis).

Photo by author
Photographie de l’auteur.

5A fundamental ecological function of BSCs in the landscape rests in stabilizing desert surfaces (Belnap and Gillette, 1998; Yair, 2003), yet BSC integrity is compromised by even the smallest disturbance (e.g., a human footprint) and devastated even more by larger events (e.g., off-road vehicle). J. Belnap and D.A. Gillette (1998), for example, discovered that BSCs have significantly higher threshold friction velocities than bare soil and disturbed BSCs. Indeed, not only do BSCs hold fragile desert soil together, but they also play a key role in preventing deflation of fine particulates into the atmosphere. In valleys dominated by an urban heat island that traps fine particulates and decreases air quality, understanding BSCs through a biogeomorphological lens can play an integral role in the management of arid and semi-arid region cities.

6Important human impact studies on soil crusts (Cole, 1990; Belnap, 1993, 1995, 1996) note that valuable fiber connections were easily broken during dry seasons. These studies also found that recovery time for disturbed soil crusts takes anywhere from six weeks for initial cyanobacterial growth to 20 years or more for larger ecosystem-essential lichen and moss growth, putting to rest the previously-accepted view of soil crust communities taking centuries to recover. Yet while most human disturbances do not kill BSC microorganisms directly, water must be available for repair mechanisms to function, something lacking in the arid and semi-arid BSC habitats (Belnap, 1993; Belnap and Lange, 2003). In order to obtain recovery data, these studies, and subsequent later studies (Belnap and Gillette, 1998; Belnap et al., 2004), focused specifically on recovery rates for soil crusts over longer temporal scales (e.g., more than one year) and further, only focused on microorganism recovery, paying no attention to the type of landform where recovery was measured, nor to the effects of BSC microclimate or seasonal precipitation regimes (key components of biogeomorphological research).

7BSCs can also assist in monitoring long-term ecological research. Because most mature crusts contain not only cyanobacteria and algae but also mosses and lichens, BSCs represent natural long-term storage systems of carbon in arid/semi-arid regions. Yet if left undisturbed, BSCs maintain extremely long life spans lasting centuries (Belnap and Lange, 2003) and have been found to, since early environments, contribute greatly to the ecosystem (Chacon-Baca et al., 2002; Beraldi-Campesi et al., 2004; Beraldi-Campesi and Cevallos-Ferriz, 2005). Understanding BSC resilience and recovery among landforms near desert cities, and the affect BSCs have on local arid and semi-arid ecosystems, may also lead to effective models for carbon sequestration in these settings. Soil organic carbon (SOC) plays a considerable role in the global carbon cycle, containing more than triple the amount of organic C found in living biomass and atmospheric CO2 (Lal, 2004b). Increasing SOC storage by a mere 5% could decrease atmospheric CO2 as much as 16% (Baldock, 2007). While C sequestration in soil remains a slow process, it may represent an efficient natural strategy to offset increased atmospheric CO2 brought on by fossil fuel emissions (Baldock, 2007). Some estimates suggest sequestration rates of up to 150 Pg CO2-C over the next century are possible if predictive accuracy can be increased (Houghton, 1995; Lal et al., 1998; Lal, 2004a). Representing “natural” long-term storage facilities for carbon in arid regions - especially relative to their mass - most mature BSCs contain not only basic carbon producers such as cyanobacteria and algae, but also carbon-rich producers such as mosses and lichens (fig. 2). The avenue of BSCs as carbon sequestration sites has been only explored slightly (Beymer and Klopatek, 1991; Evans and Belnap, 1999; Evans and Lange, 2001), and research into carbon sequestration “specifically” could prove beneficial, as BSCs are suspected to have a significant C draw-down potential, especially relative to their mass and composition, and specifically in conjunction with potential soil organic carbon drawdown from soil in general (Jeffries et al., 1989; Beymer and Klopatek, 1991; Jeffries et al., 1993 a and b; Palmqvist et al., 1994; Palmqvist, 1995; Ziegler and Lüttge, 1998; Lange, 2000; Palmqvist, 2000; Belnap et al., 2003a; Evans and Lange, 2003; Baldock, 2007).

Fig. 2 – Lichen- and moss-dominated BSC, near Zion National Park, UT (USA).
Fig. 2 Croûtes cryptogamiques à lichens et mousses, à proximité du Parc national de Zion, Utah (Etats-Unis).

Fig. 2 – Lichen- and moss-dominated BSC, near Zion National Park, UT (USA).Fig. 2 – Croûtes cryptogamiques à lichens et mousses, à proximité du Parc national de Zion, Utah (Etats-Unis).

It is thought that these types of BSCs may play an important role in the global carbon cycle - especially relative to their mass and relationship with potential SOC drawdown in conjunction with soils - including perhaps unidentified carbon sequestration sites. Photo by author.
Il est pensable que ce type de CC puisse jouer un rôle important dans le cycle global du carbone - en regard de leur masse et de leurs liens avec la chute du carbone organique des sols – incluant peut-être des sites de séquestration du carbone encore inconnus. Photographie de l’auteur.

8Besides the enormous amounts of BSC studies relating to human disturbances and nitrogen fixation capabilities of soil crusts and the limited studies relating specifically to BSC-related carbon cycling and sequestration, a great deal of research also focuses on soil crust composition and taxonomy (Cameron et al., 1965; Follmann, 1965; Cameron et al., 1966; Forest and Weston, 1966; Soriano, 1983; Belnap and Gardner, 1993; Bouza and Del Valle, 1993; Flechtner et al., 1998; Maya etal., 2002; Redfield et al., 2002). Researchers recognize four types of crusts based on visual morphology and potential evapotranspiration (PET): smooth, rugose (fig. 3), pinnacled (fig. 4), and rolling. Per J. Belnap and O.L. Lange (2003, p. 180) “smooth crusts occur in hyperarid and arid hot deserts with the highest PET; rugose crusts… in hot, arid deserts with slightly lower PET… occurring where soil freezing does not occur”. Pinnacled crusts, however, occur in arid and semi arid cold deserts where soil freezing does occur, and “lower PET supports a higher biomass of mosses and lichens than hot deserts”. Found in “even colder semiarid and cool and cold deserts, where soils freeze…” rolling crusts have an even lower PET that “…supports a larger biomass of lichens, mosses, and vascular plants than found in less moist deserts” (ibid.).

Fig. 3 – Rugose biological soil crust, McDowell Mountain Regional Park, Sonora Desert, AZ (USA).
Fig. 3 Croûte cryptogamique rugueuse, Parc régional de la McDowell Mountain, Désert du Sonora, Arizona (Etats-Unis).

Fig. 3 – Rugose biological soil crust, McDowell Mountain Regional Park, Sonora Desert, AZ (USA).Fig. 3 – Croûte cryptogamique rugueuse, Parc régional de la McDowell Mountain, Désert du Sonora, Arizona (Etats-Unis).

Photo by author
Photographie de l’auteur.

Fig. 4 – Pinnacled BSC, near Zion National Park, UT (USA).
Fig. 4 Croûte cryptogamique à pinacles, à proximité du Parc national de Zion, Utah (Etats-Unis).

Fig. 4 – Pinnacled BSC, near Zion National Park, UT (USA). Fig. 4 – Croûte cryptogamique à pinacles, à proximité du Parc national de Zion, Utah (Etats-Unis).

Photo by author.
Photographie de l’auteur.

9While taxonomic endeavors give researchers a common vernacular, the specific morphological names were generated from, mainly, climatic characteristics, regimes, and/or biomes. This climate-based morphological classification lends itself well to on-the-ground classification over small areas, but may not be applicable to larger-area studies, as most BSC climate-related studies focus “specifically” on microclimate and influences on smaller, local ecosystems, rather than generating an expanded, more holistic view or model (cf. the many local-based climate studies such as: L.C. Pearson and D.B. Lawrence, 1965; A. Goudie, 1972; G.J. Kidron, 1992; G.J. Kidron et al., 1995 a and b; G.J. Kidron and A. Yair, 1997; B. Sundberg et al., 1999; G.J. Kidron et al., 2000; M. Veste et al., 2001 a and b; C.D. Allen, 2005; S.L. Ustin et al., 2009). Large spatial area BSC assessments would be a valuable addition to potential BSC-related research agendas such as assessing climate change. Lichens, as a species, remain very susceptible to atmospheric disturbances, and may be able to aid researchers studying anthropogenic climate change factors, though using lichens in this manner is only in its infant stage and has not yet been fully investigated (Theodore Crusberg, personal communication, January 2009). Nevertheless, these areas of potential research represent shortcomings in BSC-related research that the discipline of biogeomorphology might be able to address.

10Regardless of type or classification however, BSC communities remain an important part of arid region sustainability today. They are an essential first step to producing and protecting arable soils in the fragile desert ecosystem (Belnap, 1995; Belnap and Lange, 2003; Belnap et al., 2004). The delicate microorganisms that comprise BSCs live a tenuous existence subject to the uncertainties of climate, dispersal, animals, and humans (Cole, 1990; Belnap and Lange, 2003). Disturbances of any kind increase the damage to and destruction of BSCs (Cole, 1990; Belnap et al., 1994), especially in the unprotected and increasingly-touristed arid regions of North and Latin America (Maya et al., 2002; Rosentreter and Belnap, 2003). Thus, future BSC research needs that can be addressed by biogeomorphic research techniques and principles rest in the dual problems of: (i) developing better understanding of large-area spatial dynamics of BSCs (e.g., across landforms, across biomes); and (ii) developing better understanding of biogeomorphic circumstances BSCs need to initiate their disturbance recovery. Furthermore, research challenges faced in the field of biogeomorphology are similar to those faced in BSC-related research (i.e., small area research focused on a limited set of questions). In short, because they can be monitored, studied, and modeled in fine detail “and” across larger areas, BSCs are uniquely positioned to address deficiencies in both BSC-related and biogeomorphology arenas. One important BSC assessment and monitoring technique that may make a solid contribution to this arena - especially when studied using a biogeomorphologic focus - is remote sensing.

Remote sensing and BSCs

11At its most basic, remote sensing (RS) is used to detect or infer the properties of a substance without being in direct physical contact. RS tools measure the electromagnetic (EM) energy flow from surface phenomena in and across different regions of the wavelength spectrum. Energy can be emitted from an object due to its temperature or reflectance from a natural (e.g., sun) or artificial (e.g., radar) source. Energy reflected from surfaces varies as a function of wavelength. When it comes to soil, the most important factor affecting reflectance is the soil mineralogy (e.g., iron oxides, clay minerals, carbonates), though soil reflectance, soil-water content, organic matter content, soil texture, and soil roughness are also factors (Karnieli et al., 2003). Remotely sensed images combine different spectra channels to create specific indices to assess percent of “cover” and accompanying biophysical condition. The most widely used index for these purposes is the Normalized Difference Vegetation Index (NDVI). The NDVI values range from -1 to +1, with denser and/or healthier vegetation having higher positive values. A.R. Huete et al. (1984), however, note that in arid regions, exposed soils have a significant effect on NDVI values. Still, vegetation indices generated via satellite-borne sensors usually consist of measurements in a few channels, resulting in a coarse spectral resolution (referred to as broad-band, multispectral sensors, e.g., Landsat TM). Yet E. Zaady et al. (2007) successfully used the NDVI in conjunction with the Brightness Index (BI) to monitor BSC succession and regeneration rates over long periods (years) and correlated findings with slope aspect (i.e., difference of BSC spatial distribution between north- and south-facing slopes). This technique could prove useful in the biogeomorphological arena.

12In contrast to broad-band multispectral sensors, hyperspectral RS measures EM reflectance in hundreds of continuous narrow-bands (e.g., the Airborne Visible and Infra-Red Imaging Spectrometer (AVRIS) operated by NASA/JPL; Green et al., 1998). The ability to determine and identify absorption features in a reflectance spectrum that arise from chemical bonds present in the surface materials gives hyperspectral RS a sizeable advantage over multispectral RS. This has specific implications for BSC-related spatial studies, because hyperspectral imaging can more easily discriminate between shape and wavelength position of absorption features instead of merely sensing the differential reflectance level in two channels. Yet multispectral and hyperspectral imaging are generally used in non-BSC research arenas such as geologic mapping (Lillesand and Keifer, 2002), environmental studies (Swayze et al., 2000), vegetation cover identification (Martin et al., 1998; Roberts et al., 1998), and vegetation biochemical composition (Kokaly and Clark, 1999). For small area assessments, such as small plots of BSCs on differing landforms however, hyperspectral imaging remains relatively expensive to conduct, while multispectral imaging offers limited coverage, although Landsat TM has been used to successfully distinguish BSCs from bare ground (Wessels and van Vuuren, 1986). Less expensive and more conducive to on-the-ground fieldwork, a hand-held spectroradiometer offers coverage over most of the EM spectrum necessary to assess BSC biogeomorphology, but would only be feasible over smaller areas as well. Even capturing BSC communities on differing landforms and/or across biomes and climatic regimes using repeat digital photography from the ground can prove useful (Bowker et al., 2008), as BSCs are more active over short-time scales than formerly thought (Belnap et al., 2006), but this requires a longer timeframe. At a more general remote sensing level, A. Karnieli et al. (2003) outline how differing forms of RS, such as spacecraft versus aircraft, might be used in conjunction with more traditional in situ and laboratory techniques to quantify not only BSCs, but also higher plants and bare soils, using examples from Israel, the Colorado Plateau, and the rangelands of Southeastern Idaho. Globally speaking, BSC spectra have similar signatures even when species composition vary, and thus can be distinguished from other ground components, allowing for mapping based solely on RS data (Karnieli et al., 2003).

13Overall, RS provides an opportunity to expand in situ BSC and BSC-related studies, cutting-down on the costs, time, and energy used in ground truthing. Large areal assessments are important to understanding spatial dynamics of BSCs across the larger ecosystem (Belnap and Lange, 2003). Yet even though BSCs are found in nearly every environment in the world (Büdel, 2003) - and while scientific and research endeavors related to BSCs are growing - very few studies have been conducted on how RS can enhance the study of BSC spatiality. Of those studies published, according to A. Karnieli et al. (2003), D.C.J. Wessels and D.R.J. van Vuuren (1986) were the first researchers to detect and map BSCs using solely satellite imagery. Their work in the Namib Desert using Landsat TM imagery led to discrimination between lichen covered, bare, and vegetation-covered surfaces. Later, however, Y.M. Zhang et al. (2007) discovered that using Landsat imagery to assess BSC coverage is only workable when BSCs represent more than 33% of the field of view. Aside from these two studies focused on using Landsat TM data, relatively few publications have specifically studied BSCs using some kind of spectral imagery and/or RS - even to map them - although studies such as J. Chen et al. (2005) developed an algorithm-based BSC-specific index for mapping. Other notable BSC-specific RS algorithms include E. Ben-Dor et al. (2003) who measured BSC structure in specific wavelengths and A. Karnieli et al. (1995, 1996, 1997) who used spectral reflectance as a diagnostic tool have proved valuable, and the more advanced BSC-specific Continuum Removal Crust Identification Algorithm (CRCIA) developed by B. Weber et al. (2008) using hyperspectral datasets.

14One characteristic of BSCs that has been noticed - at a basic ground level by C.D. Allen (2005) and on a spectral scale by A. Karnieli and H. Tsoar (1995), A. Karnieli et al. (1996, 1997, 2003), S.B. Fang et al. (2008), and S.L. Ustin et al. (2009) - is that BSC spectral reflectance changes due to precipitation (fig. 5). This change in spectral reflectance apparently alters both the NDVI and the pigment absorption, which can sometimes be misinterpreted in RS analysis (Karnieli et al., 2003; Fang et al., 2008). Further, while distinguishing between individual BSC stands might not be possible using satellite imagery, this apparently does not affect the ability of using high-altitude RS to monitor local or regional changes in BSCs (Ustin et al., 2009). Thus, while high-altitude RS can be used for BSC assessment, there still remains a need for on-the-ground, small-area assessment. For example, after using a BSC-specific algorithm to identify and potentially map BSC stands over large areas, a high-resolution image of a specific stand could be taken closer to the ground, and then post-processed using remote sensing software (e.g., ERDAS Imagine) to determine which specific wave-lengths represent BSCs versus bare ground, rock type, and higher plant life. This type of remotely sensed data could be obtained through the use of “pole cameras”, balloon (or kite) photography, or even low-altitude (aerial) remote controlled vehicles with a still and/or video camera mount, yielding truly rich datasets from which to analyze BSC biogeomorphology.

Fig. 5 – Spectral difference between wet (left) and dry (right) rugose BSC, Snow Canyon State Park, UT (USA).
Fig. 5 Différence spectrale entre des croûtes cryptogamiques rugueuses humide (gauche) et sèche (droite), Snow Canyon State Park, Utah (Etats-Unis).

Fig. 5 – Spectral difference between wet (left) and dry (right) rugose BSC, Snow Canyon State Park, UT (USA). Fig. 5 – Différence spectrale entre des croûtes cryptogamiques rugueuses humide (gauche) et sèche (droite), Snow Canyon State Park, Utah (Etats-Unis).

Real-time video of change in spectral reflectance due to precipitation available here: http://www.youtube.com/​watch?v=1ybZM9MRjxM.
Vidéo en temps réel du changement de la réflectance spectrale dû aux précipitations disponible ici : http:/www.youtube.com/watch?v=1ybZM9MRjxM.

Photo by author.
Photographie de l’auteur.

BSC biogeomorphology and weathering science

15When it comes to BSCs, big picture linkages remain a research deficit, as J. Belnap and O.L. Lange (2003) clearly articulate, and contribute to the need for a better linkage between BSC-related research and the larger conceptual need for a systemic conceptual biogeomorphic framework, as L.A. Naylor et al. (2002) argue. With specific regards to biogeomorphology, BSC research should help fill the gap between the biogeomorphology triumvirate (bioconstruction, bioerosion, and bioprotection; Naylor et al., 2002) by building strong connections through innovative environmental models by assessing spatial effects of human disturbances of BSCs. This in turn would lead to research regarding BSC resiliency, opening new possibilities for ecosystem sustainability research, as suggested in the work of M.A. Bornyasz et al. (2005), and important emerging fields of study related to BSCs, such as geobiology, a field of study that combines earth science and biology and influences environmental decision making and the larger arena of biocomplexity (Naylor et al., 2002; Noffke, 2005), much as BSCs could do if specific landform type, differing climatic regimes (even meta-analyses), and weathering parameters were studied through a biogeomorphological lens. Indeed, when it comes to BSCs and weathering science, few disciplines are better prepared to assess linkages than those trained in biogeomorphology, where the interaction between biota and landform - usually through weathering - comes to the forefront.

16Researchers such as C. Ollier (1974) discuss weathering and landforms in detail and C. Ollier and C. Pain (1996) discuss weathering in the context of soils in general, yet few studies focus specifically on weathering as related to BSCs, though recently C. Ollier and H. Sheth (2008) discuss duricrusts in relation to soil formation (in India) and H. Murakami and S. Ishihara (2008) studied rare earth elements in weathered crusts of China and Japan. Because it focuses on spatial relationships (e.g., the weathering-climate-landform-organisms continuum) biogeomorphology, as a discipline, should stand at the forefront of future BSC research endeavors, especially when it comes to weathering.

17While BSCs have been studied in nearly every environment around the globe, most studies remain ecologically-specific, only taking into account “specific” landform and climate types randomly (for locational overviews, see chapters 2-11 in J. Belnap and O.L. Lange, 2003). Nevertheless, important studies related to local scale BSC landform type and local climate can be found, though they seem to focus on “specific” dune fields and “seasonal” rainfall in the Negev Desert (Kidron and Yair, 1997; Kidron et al., 2002, 2003, 2009), “specific” alluvial fans (Barker et al., 2005) or dunes (Brostoff et al., 2005) in the Mojave Desert, “specific” pediments in the Sonora Desert (Allen, 2005; Beraldi-Campesi et al., 2009), and mostly basin or other “fill” in the Colorado Plateau (Belnap, 1990; Lange et al., 1997; Bowker et al., 2002; Belnap et al., 2003b; Belnap, 2006). Other locations that have received limited study in relation to “local” landform type and climate include: Namib Desert (Goudie, 1972; Lange et al., 1994; Lalley and Viles, 2008), Antarctica (Boyd et al., 1966; Wynn-Williams, 1993; Green and Broady, 2003), and the Atacama (Rundel et al., 1991; Warren-Rhodes et al., 2007). While it may be possible to conduct a meta-analysis of broader landform-climate relations from these studies, no specific model has yet been developed, though such models have been suggested in regards to general biogeomorphic and ecological research (Viles et al., 2008) and more specifically to a biogeomorphic approach to rock weathering (Viles, 1995). Nevertheless, such overarching studies would probably be constrained by comparative time-scales. That is, while studies do exist, they have occurred at disparate timeframes, some in the 1970s, some in the 1980s, some in the 1990s, etc., and correlating “old” data with newer data might pose a problem.

18As epilithic organisms, however, BSCs play an intimate role in weathering processes through bedrock colonization and trapping dust that eventually filters into rock through fissures, where their small size allows for penetration into interstices of sands and silts, especially compared to higher plants (Hunt, 1979). With increased weathering, more Ca-silicates are exposed to carbonic acid, improving porosity and permeability because rock fragments (from weathering) eventually become sedimentary rocks (e.g., limestone and subsequent CO2 storage, sandstone with high silica content; fig. 6). And when it comes to weathering-BSC relationships specifically, studies are fewer, and seem to only account for BSC-weathering related research when consequential to other topical investigations.

Fig. 6 – Rugose BSC as an epilithic organism, weathering sandstone rock, Near Zion National Park, UT (USA).
Fig. 6 Croûte cryptogamique rugueuse épilithique météorisant un grès, à proximité du Parc national de Zion, Utah (Etats-Unis).

Fig. 6 – Rugose BSC as an epilithic organism, weathering sandstone rock, Near Zion National Park, UT (USA). Fig. 6 – Croûte cryptogamique rugueuse épilithique météorisant un grès, à proximité du Parc national de Zion, Utah (Etats-Unis).

This weathering-BSC interaction represents perhaps the most important category of future biogeomorphological research.
Cette interaction entre la CC et la météorisation représente probablement la plus importante des pistes de recherche biogéomorphologique futures.

Photo by author.
Photographie de l’auteur.

19One of the first such studies was performed by N.A. Krasil’nikov (1949), and focused specifically on mountain rocks, though his later study in the same area focused on high-altitude nitrogen fixing potential of microflora (Krasil’nikov, 1956), a notable and continuing research thread still prevalent in BSC-ecological research fields today [see F.L. Pérez (1997) for work in the Andes, and R. Türk and G. Gärtner (2003) for research overview in the Alps]. While many studies continue Krasil’nikov’s nitrogen-fixing studies, BSC-weathering related research in alpine environments remains scant, usually leaving the relationship - if it is noted at all - as a side note (Gold, 1998; Dickson, 2000; Zielke et al., 2002). Studies relating to CO2 and nitrogen fixation in alpine environments abound, but again, these studies neglect to mention the important BSC-weathering connection (Alexander and Schell, 1973; Forman and Dowden, 1977; Wojciechowski and Heimbrook, 1984; Henry and Svoboda, 1986; Chapin, 1996; Liengen and Olsen, 1997; Dickson, 2000; Zielke et al., 2002).

20Contemporary climate-weathering studies relatable to biogeomorphology-BSC research agendas include P.V. Brady et al. (1999) who centered on lichens in relation to silicate weathering, J.D. Brotherson et al. (1985) focusing specifically on plant communities, B. Büdel’s (1999) work in topical environments, R. Chen et al. (2009) who studied mineral components of BSCs, A. Danin’s (1983) work on cyanobacteria weathering limestone, H. Murakami and S. Ishihara (2008)’s study using rare earth elements, and Viles’ broad ecological scope of rock decay (Viles, 1995). Notwithstanding the contribution of these landform-climate and weathering-BSC studies to biogeomorphological-BSC research, these two overarching research foci still represent areas where biogeomorphology can make significant contributions. In fact, H.A. Viles (2008) strongly suggests BSCs may be the key to understanding weathering in arid and semi-arid regions. The path seems clear then for biogeomorphology to take the lead in - or at least pave the way for - future, and very significant, spatially-based BSC research (i.e., broader climate-landform-weathering-BSC relationships).

Conclusion

21A first step in understanding key issues of how biogeomorphology can influence BSC research rests in evaluation of BSC spatial characteristics, specifically landform, climate, and weathering parameters (and, if possible link these across large areas). This article seeks to discuss these research topics in relation to each other generally, and how biogeomorphology might inform them specifically. Because a fundamental ecological function of BSCs in the landscape rests in stabilizing desert surfaces (Belnap and Lange, 2003), it then follows that if particular landforms (at a regional scale instead of the more-studied local scale) are more frequently “used” (e.g., tourism and/or ecotourism) or “invaded” (e.g., urban sprawl) by humans, understanding BSC recovery across landforms, biomes, and seasonality (climate), could enhance their preservation, or at least augment associated land management practices. As cities expand, and begin to sprawl across the landscape, there exists an inherent need for careful preservation and management of the surrounding regions, especially in ecologically fragile biomes. Creating new, widely-applicable spatial dynamic models of BSCs, using the discipline of biogeomorphology as a guide, could alter environmental decision making by, for example, restricting recreational and/or developmental activities on certain types of landforms and/or certain climatic regimes.

22When conducted through a biogeomorphological lens, BSC research will also open new possibilities for resiliency and ecosystem sustainability research (e.g., geobiology). Yet even regardless of potential research outcomes it remains clear that, as a discipline, biogeomorphology stands poised to offer strong contributions to BSC research agendas and could have long-lasting impacts on the field. There exists a fundamental need for researchers who study spatial interactions between landform, biota, and climate - biogeomorphologists - to become involved in and work alongside our more ecologically-trained colleagues (Viles et al., 2008). By becoming more engaged in BSC research, biogeomorphologists can also help narrow already-identified research gaps in this fundamental field of inquiry through their inherent focus on spatiality. Indeed, it is precisely the focus on spatiality that current BSC research lacks, and where biogeomorphology as a discipline remains strongest.

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Bibliographie

Alexander V.A., Schell D.M. (1973) – Seasonal and spatial variation of nitrogen fixation in the Banow Alaska tundra. Arctic Alpine Research 5, 77-88.

Allen C.D. (2005) – Micrometeorology of a smooth and rugose biological soil crust near Coon Bluff, Arizona. Journal of the Arizona-Nevada Academy of Science 38, 21-28.

Baldock J.A. (2007) – Composition and Cycling of Organic Carbon in Soil. In Marschner P., Rengel Z. (Eds): Nutrient Cycling in Terrestrial Ecosystems. Springer, Berlin, 1-35.

Barker D.H., Stark L.R., Zimpfer J.F., McLetchie N.D., Smith S.D. (2005) – Evidence of drought-induced stress on biotic crust moss in the Mojave Desert. Plant Cell and Environment 28, 939-947.

Belnap J. (1990) – Microbiotic crusts: their role in past and present ecosystems. Park Science Resource Management Bulletin 10, 3-4.

Belnap J. (1993) – Recovery rates of cryptobiotic crusts: inoculant use and assessment methods. Great Basin Naturalist 53, 89-95.

Belnap J. (1995) –Surface disturbances: their role in accelerating desertification. Environmental Monitoring and Assessment 37, 39-57.

Belnap J. (1996) Soil surface disturbances in cold deserts: effects on nitrogenase activity in cyanobacterial-lichen soil crusts. Biology and Fertility of Soils 23, 362-367.

Belnap J. (2006) The potential roles of biological soil crusts in dryland hydrologic cycles. Hydrological Processes 20, 3159-3178.

Belnap J., Gardner J.S. (1993) Soil microstructure in soils of the Colorado Plateau: the role of the cyanobacterium Microcoleus vaginatus. Great Basin Naturalist 53, 40-47.

Belnap J., Gillette D.A. (1998) Vulnerability of desert biological soil crusts to wind erosion: the influences of crust development, soil texture, and disturbance. Journal of Arid Environments 39, 133-142.

Belnap J., Lange O.L. (2003) Biological soil crusts: structure, function, and management. Springer-Verlag, Berlin, 503 p.

Belnap J., Harper K.T., Warren S.D. (1994) Surface disturbance of cryptobiotic soil crusts: nitrogenase activity, chlorophyll content, and chlorophyll degradation. Arid Soil Research and Rehabilitation 8, 1-8.

Belnap J., Büdel B., Lange O.L. (2003a) Biological soil crusts: characteristics and distribution. In Belnap J., Lange O.L. (Eds): Biological Soil Crusts: Structure, Function, and Management. Springer, Berlin, 3-30.

Belnap J., Hawkes C.V., Firestone M.K. (2003b) Boundaries in miniature: two examples from soil. BioScience 53, 739-749.

Belnap J., Phillips S.L., Miller M.E. (2004) Response of desert biological soil crusts to alterations in precipitation frequency. Oecologia 141, 306-316.

Belnap J., Phillips S.L., Troxler T. (2006) Soil lichen and moss cover and species richness can be highly dynamic: The effects of invasion by the annual exotic grass Bromus tectorum, precipitation, and temperature on biological soil crusts in SE Utah. Applied Soil Ecology 32, 63-76.

Ben-Dor E., Goldlshleger N., Benyamini Y., Agassi M., Blumberg D.G. (2003) The spectral reflectance properties of soil structural crusts in the 1.2- to 2.5-mu m spectral region. Soil Science Society of America Journal 67, 289-299.

Beraldi-Campesi H., Cevallos-Ferriz S.R.S. (2005) Microfossil diversity in the Tarahumara Formation, Sonora. Revista Mexicana De Ciencias Geologicas 22, 261-271.

Beraldi-Campesi H., Cevallos-Ferriz S.R.S., Chacon-Baca E. (2004) Microfossil algae associated with Cretaceous stromatolites in the Tarahumara Formation, Sonora, Mexico. Cretaceous Research 25, 249-265.

Beraldi-Campesi H., Hartnett H.E., Anbar A., Gordon G.W., Garcia-Pichel F. (2009) Effect of biological soil crusts on soil elemental concentrations: implications for biogeochemistry and as traceable biosignatures of ancient life on land. Geobiology 7, 348-359.

Berner R.A. (1994) 3GEOCARB-II - A revised model of atmospheric CO2 over phanerozoic time. American Journal of Science 294, 56-91.

Berner R.A. (1995) Chemical weathering and its effect on atmospheric CO2 and climate. In White A.F., Brantly S.L. (Eds): Chemical Weathering Rates of Silicate Minerals Chemical Weathering and its Effect on Atmospheric CO2 and Climate. Mineralogical Society of America, 565-583.

Berner R.A., Kothavala Z. (2001) GEOCARB III: A revised model of atmospheric CO2 over phanerozoic time. American Journal of Science 301, 182-204.

Beymer R.J., Klopatek J.M. (1991) Potential contribution of carbon by microphytic crusts in pinyon-juniper woodlands. Arid Soil Research and Rehabilitation 5, 187-198.

Bornyasz M.A., Graham R.C., Allen M.F. (2005) Ectomycorrhizae in a soil-weathered granitic bedrock regolith: Linking matrix resources to plants. Geoderma 126, 141-160.

Bouza P., Del Valle H.F. (1993) Micromorphological, physical, and chemical characteristics of soil crust types of the central Patagonia region, Argentina. Arid Soil Research and Rehabilitation 7, 355-368.

Bowker M., Reed S.C., Belnap J., Phillips S. (2002) Temporal variation in community composition, pigmentation, and Fv /Fm of desert cyanobacterial soil crusts. Microbial Ecology 43, 13-25.

Bowker M.A., Johnson N.C., Belnap J., Koch G.W. (2008) Short-term monitoring of aridland lichen cover and biomass using photography and fatty acids. Journal of Arid Environments 72, 869-878.

Boyd W.L., Staley J.T., Boyd J.W. (1966) Ecology of soil microorganisms in Antarctica. In Tedrow J.C.F. (Ed.): Antarctic Soils and Soil Forming Processes. Antarctic Research Series 8, 125-159.

Brady P.V., Caroll S.A. (1994) Direct effects of CO2 and temperature on silicate weathering: possible implication for climate control. Journal of Geophysical Research 58, 853-1853.

Brady N.C., Weil R.R. (2008) The nature and property of soils. 14th ed. Pearson Prentice Hall, Upper Saddle River, NJ, 960.

Brady P.V., Dorn R.I., Brazel A.J., Clark J., Moore R.B., Glidewell T. (1999) Direct measurement of the combined effects of lichen, rainfall, and temperature on silicate weathering. Geochimica et Cosmochimica Acta 63, 3293-3300.

Brostoff W.N., Sharifi M.R., Rundel P.W. (2005) Photosynthesis of cryptobiotic soil crusts in a seasonally inundated system of pans and dunes in the western Mojave Desert, CA: Field studies. Flora 200, 592-600.

Brotherson J.D., Evenson W.E., Rushforth S.R., Fairchild J., Johansen J.R. (1985) Spatial patterns of plant communities and differential weathering in Navajo National Monument, Arizona. Great Basin Naturalist 45, 1-13.

Büdel B. (1999) Ecology and diversity of rock-inhabiting cyanobacteria in tropical regions. European Journal of Phycology 34, 361-370.

Büdel B. (2003) Synopsis: Comparative Biogeography and Ecology of Soil Crust Biota. In Belnap J., Lange O.L. (Eds): Biological Soil Crusts: Structure, Function, and Management. Springer, Berlin, 141-152.

Budyko M.I., Ronov A.B. (1979) Chemical evolution of the atmosphere in the Phanerozoic. Geochemistry International 16, 1-9.

Cameron R.E., Blank G.B., Gensel D.R., Davies R.W. (1965) Soil studies-desert microflora. X. Soil properties of samples from the Chile Atacama Desert. California Institute of Technology, National Aeronautics and Space Administration, Jet Propulsion Laboratory, Pasadena, CA, 214-222.

Cameron R.E., Gensel D.R., Blank G.B. (1966) Soil studies--desert microflora. XII. Abundance of microflora in soil samples from the Chile Atacama Desert, supportive research and advanced development. National Aeronautics and Space Administration, Jet Propulsion Laboratory, Pasadena, CA, 140-147.

Chacon-Baca E., Beraldi-Campesi H., Cevallos-Ferriz S.R.S., Knoll A.H., Golubic S. (2002) 70 Ma nonmarine diatoms from northern Mexico. Geology 30, 279-281.

Chapin D.M. (1996) Nitrogen mineralization, nitrification, and denitrification in a high arctic lowland ecosystem, Devon Island, N.W.T., Canada. Arctic and Alpine Research 28, 85-92.

Chen J., Zhang M.Y., Wang L., Shimazaki H., Tamura M. (2005) A new index for mapping lichen-dominated biological soil crusts in desert areas. Remote Sensing of Environment 96, 165-175.

Chen R., Zhang Y., Li Y., Wei W., Zhang J., Wu N. (2009) The variation of morphological features and mineralogical components of biological soil crusts in the Gurbantunggut Desert of Northwestern China. Environmental Geology 57, 1135-1143.

Cole D.N. (1990) Trampling disturbance and recovery of cryptogamic soil crusts in Grand Canyon National Park. Great Basin Naturalist 50, 321-325.

Danin A. (1983) Weathering of limestone in Jerusalem by cyanobacteria. Zeitschrift für Geomorphologie 27, 413-421.

Dickson L.G. (2000) Constraints to Nitrogen Fixation by Cryptogamic Crusts in a Polar Desert Ecosystem, Devon Island, N.W.T., Canada. Arctic, Antarctic, and Alpine Research 32, 40-45.

Drever J.I. (1994) The effect of land plants on weathering rates of silicate minerals. Geochimica et Cosmochimica Acta 58, 2325-2332.

Evans R.D., Belnap J. (1999) Long-term consequences of disturbance on nitrogen dynamics in an arid ecosystem. Ecology 80, 150-160.

Evans R.D., Lange O.L. (2001) Biological soil crusts and ecosystem nitrogen and carbon dynamics. In Belnap J., Lange O.L. (Eds): Biological Soil Crusts: Structure, Function, and Management. Springer, Berlin, 263-279.

Evans R.D., Lange O.L. (2003) Biological soil crusts and ecosystem nitrogen and carbon dynamics. In Belnap J., Lange O.L. (Eds): Biological Soil Crusts: Structure, Function, and Management. Springer, Berlin, 263-269.

Fang S.B., Liu H.J., Zhang X.S., Dong M., Liu J.D. (2008) Progress in spectral characteristics of biological soil crust of arid or semiarid region. Spectroscopy and Spectral Analysis 28, 1842-1845.

Flechtner V.R., Johansen J.R., Clark W.H. (1998) Algal composition of microbiotic crusts from the central desert of Baja California, Mexico. The Great Basin Naturalist 58, 295-311.

Follmann G. (1965) Fensterflechten in der Atacamawüste. Naturwissenschaften 14, 434-435.

Forest H.S., Weston C.R. (1966) Blue-green algae from the Atacama desert of northern Chile. Journal of Phycology 2, 163-164.

Forman R.T.T., Dowden D.L. (1977) Nitrogen fixing lichen roles from desert to alpine in the Sangre de Cristo mountains, New Mexico. The Bryologist 80, 561-570.

Gold W.G. (1998) The influence of cryptogamic crusts on the thermal environment and temperature relations of plants in a high arctic polar desert, Devon Island, N.W.T., Canada. Arctic and Alpine Research 30, 108-120.

Goudie A. (1972) Climate, weathering, crust formation, dunes and fluvial features of the central Namib Desert, near Gobabeb, South West Africa. Madoqua 2-1, 15-31.

Green R.O., Eastwood M.L., Sarture C.M., Thomas G.C., Aronsson M., Chippendale B.J., Faust J.A., Pavri B.E., Chovit C.J., Solis M., Olah M.R., Williams O. (1998) Imaging Spectroscopy and the Airborne Visible/Infrared Imaging Spectrometer (AVIRIS) - Remote Sensing of the Environment 65, 227–248.

Green T.G.A., Broady P. (2003) Biological soil crusts of Antarctica. In Belnap, J., Lange, O. L., (eds): Biological Soil Crusts: Structure, Function, and Management. Springer, Berlin, 133-139.

Harper K. T., Pendleton R.L. (1993) Cyanobacteria and cyanolichens: can they enhance availability of essential minerals for higher plants? Great Basin Naturalist 53, 59-72.

Henry G.H.R., Svoboda J. (1986) Dinitrogen fixation (acetylene reduction) in high arctic sedge meadow communities. Arctic and Alpine Research 18, 181-187.

Houghton R.A. (1995) Changes in the Storage of Terrestrial Carbon Since 1850. In Lal R., Kimble J., Levine E., Stewart B.A. (Eds): Soils and Global Change. CRC Press, Boca Raton, 45-65.

Huete A.R., Post D.F., Jackson R.D. (1984) Soil Spectral Effects on 4-Space Vegetation Discrimination. Remote Sensing of Environment 15, 155-165.

Hunt J.M. (1979) Petroleum Geochemistry and Geology. W.H. Freeman and Company, San Francisco, 617.

Jeffries D.L., Link S.O., Klopatek J.M. (1989) CO2 fluxes of cryptogamic crusts in response to resaturation. Bulletin of the Ecological Society of America 70, 156.

Jeffries D.L., Link S.O., Klopatek J.M. (1993a) CO2 fluxes of cryptogamic crusts. I. Response to resaturation. The New Phytologist 125, 163-173.

Jeffries D.L., Link S.O., Klopatek J.M. (1993b) CO2 fluxes of cryptogamic crusts. II. Response to dehydration. The New Phytologist 125, 391-396.

Karnieli A., Tsoar H. (1995) – Satellite spectral reflectance of biogenic crust developed on desert dune sand along the Israel-Egypt border. International Journal of Remote Sensing 16, 369-374.

Karnieli A., Shachak M., Tsoar H., Zaady E., Kaufman Y., Danin A., Porter W. (1996) The effect of microphytes on the spectral reflectance of vegetation in semiarid regions. Remote Sensing of Environment 57, 88-96.

Karnieli A., Kidron G.J., Glaesser C., Ben-Dor E. (1997) Spectral characteristics of cyanobacterial soil crust in the visible, near infrared and short wave infrared (400-2,500 nm) in semiarid environments. In Twelfth International Conference and Workshops on Applied Geologic Remote Sensing, Denver, Colorado, 417-424.

Karnieli A., Kokaly R., West N.E., Clark R.N. (2003) Remote sensing of biological soil crusts. In Belnap J., Lange O.L. (Eds): Biological Soil Crusts: Structure, Function, and Management. Springer-Verlag, Berlin, 431-455.

Kidron G.J. (1992) The impact of the microbial crust upon the relationship of rainfall, runoff and sediment yield at longitudinal dunes in an arid environment. Nizzana, Western Negev, Israel. In The First Israel Geomorphological Conference, Beer Sheva, Israel, 81-82.

Kidron G.J., Yair A. (1997) Rainfall-runoff relationship over encrusted dune surfaces, Nizzana, Western Negev, Israel. Earth Surface Processes and Landforms 22, 1169-1184.

Kidron G.J., Vonshak A., Abeliovich A. (1995a) Five microbiotic crust types in the Nizzana dune field: factors affecting their variability and measurements of their regeneration time. Israeli Geological Society Annual Meeting 62-94.

Kidron G.J., Yair A., Abeliovich A. (1995b) Paleo-climatological implications concerning runoff over encrusted dune slopes in an arid region, Nizzana, Western Negev Desert, Israel. The Second International Symposium on the Geology of the Eastern Mediterranean Region, Jerusalem, Israel, 10.

Kidron G. J., Barzilay E., Sachs E. (2000) Microclimate control upon sand microbiotic crusts, western Negev Desert, Israel. Geomorphology 36, 1-18.

Kidron G.J., Herrnstadt I., Barzilay E. (2002) The role of dew as a moisture source for sand microbiotic crusts in the Negev Desert, Israel. Journal of Arid Environments 52, 517-533.

Kidron G.J., Yair A., Vonshak A., Abeliovich A. (2003) Microbiotic crust control of runoff generation on sand dunes in the Negev Desert. Water Resources Research 39, 1108.

Kidron G.J., Vonshak A., Abeliovich A. (2009) Microbiotic crusts as biomarkers for surface stability and wetness duration in the Negev Desert. Earth Surface Processes and Landforms 34, 1594-1604.

Kokaly R.F., Clark R.N. (1999) Spectroscopic determination of leaf biochemistry using band-depth analysis of absorption features and stepwise multiple linear regression. Remote Sensing of Environment 67, 267-287.

Krasil’nikov N.A. (1949) The role of microorganisms in the weathering of (mountain) rocks. Mikrobiologiya 18, 224-232.

Krasil’nikov N.A. (1956) Microflora of high-altitude rocks and nitrogen-fixing effect. Uspehi. Sovrem. Biol. 412.

Lal R. (2004a) Soil carbon sequestration to mitigate climate change. Geoderma 123, 1-22.

Lal R. (2004b) Agricultural activities and the global carbon cycle. Nutrient Cycling in Agroecosystems 70, 103-116.

Lal R., Kimble K., Follet R., Cole C. (1998) The potential of US cropland to sequester carbon and mitigate the greenhouse effect. Ann Arbor Press, Chelsea, MI, 144.

Lalley J.S., Viles H.A. (2008) Recovery of lichen-dominated soil crusts in a hyper-arid desert. Biodiversity and Conservation, 17, 1-20.

Lange O.L. (2000) Photosynthetic performance of a gelatinous lichen under temperate habitat conditions: long-term monitoring of CO2 exchange of Collema cristatum. Bibliotheca Lichenologica 75, 307-332.

Lange O.L., Meyer A., Zellner H., Heber U. (1994) Photosynthesis and water relations of lichen soil-crusts: Field measurements in the coastal fog zone of the Namib Desert. Functional Ecology 8, 253-264.

Lange O.L., Belnap J., Reichenberger H., Meyer A. (1997) Photosynthesis of green algal soil crust lichens from arid lands in southern Utah, USA: role of water content on light and temperature responses of CO2 exchange. Flora 192, 1-15.

Liengen T., Olsen R.A. (1997) Nitrogen fixation by free-living cyanobacteria from different coastal sites in a high arctic tundra, Spitsbergen. Arctic and Alpine Research 29, 470-477.

Lillesand T.M., Keifer R.W. (2002) Remote Sensing and Image Interpretation. John Wiley and Sons, New York, 736.

MacGregor A.N., Johnson D.E. (1971) Capacity of desert algal crusts to fix atmospheric nitrogen. Soil Science Society of America Proceedings 35, 843-844.

Martin M.E., Newman S.D., Aber J.D., Congalton R.G. (1998) Determining forest species composition using high spectral resolution remote sensing data. Remote Sensing of Environment 65, 249-254.

Maya Y., López-Cortés A., Soeldner A. (2002) Cyanobacterial microbiotic crusts in eroded soils of a tropical dry forest in the Baja California Peninsula, Mexico. Geomicrobiology Journal 19, 505-518.

Molnar P., England P., Martinod J. (1993) Mantle dynamics, uplift of the Tibetan Plateau, and the Indian Monsoon. Review of Geophysics 31, 357-396.

Murakami H., Ishihara S. (2008) REE Mineralization of Weathered Crust and Clay Sediment on Granitic Rocks in the Sanyo Belt, SW Japan and the Southern Jiangxi Province, China. Resource Geology 58, 373-401.

Naylor L.A., Viles H.A., Carter N.E.A. (2002) Biogeomorphology revisited: looking towards the future. Geomorphology 47, 3-14.

Noffke N. (2005) Geobiology - a holistic scientific discipline. Palaeogeography Palaeoclimatology Palaeoecology 219, 1-3.

Ollier C. (1974) Weathering and Landforms. Nelson Thornes Ltd, Cheltenham, 64 p.

Ollier C., Pain C. (1996) Regolith, Soils and Landforms. Wiley, Hoboken, NJ, 326 p.

Ollier C., Sheth H. (2008) The High Deccan duricrusts of India and their significance for the ‘laterite’ issue. Journal of Earth System Science 117, 537-551.

Palmqvist K. (1995) Uptake and fixation of CO2 in lichen photobionts. Symbiosis 18, 95-109.

Palmqvist K. (2000) Carbon economy in lichens. New Phytologist 148, 11-36.

Palmqvist K., Máguas C., Badger M.R., Griffiths H. (1994) Assimilation, accumulation, and isotope discrimination of inorganic carbon in lichens: further evidence for the operation of a CO2 concentrating mechanism in cyanobacterial lichens. Cryptogamic Botany 4, 218-226.

Pearson L.C., Lawrence D.B. (1965) Lichens as microclimate indicators in northwestern Minnesota. The American Midland Naturalist 74, 257-268.

Pérez F.L. (1997) Microbiotic crusts in the high equatorial Andes, and their influence on paramo soils. Catena 31, 173-198.

Redfield E., Barns S. M., Belnap J., Daane L.L., Kuske C.R. (2002) Compariative diversity and composition of cyanobacteria in three prominent soil crusts of the Colorado Plateau. FEMS Microbiology Ecology 40, 55-63.

Roberts D.A., Gardner M., Church R., Ustin S., Scheer G., Green R.O. (1998) Mapping chaparral in the Santa Monica Mountains using multiple endmember spectral mixture models. Remote Sensing of Environment 65, 267-279.

Rosentreter R., Belnap J. (2003) Biological soil crusts of North America. In Belnap J., Lange O.L. (Eds): Biological Soil Crusts: Structure, Function, and Management. Springer, Berlin, 31-50.

Rundel P.W., Dillon M.O., Palma B., Mooney H.A., Gulmon S.L., Ehleringer J.R. (1991) The phytogeography and ecology of the coastal Atacama and Peruvian deserts. Aliso 11, 1-50.

Rychert R.C., Skujins J. (1974) Nitrogen fixation by blue-green algae-lichen crusts in the Great Basin Desert. Soil Science Society of America Proceedings 38, 768-771.

Soriano A. (1983) Deserts and semi-deserts of Patagonia. In Ecosystems of the World 5, Temperate Deserts and Semi-deserts. N.E. West Amsterdam, Elsevier, 423-460.

Sundberg B., Ekblad A., Näsholm T., Palmqvist K. (1999) Lichen respiration in relation to active time, temperature, nitrogen and ergosterol concentrations. Functional Ecology 13, 119-125.

Swayze G.A., Smith K.S., Clark R.N., Sutley S.J., Pearson R.M., Vance J.S., Hageman P.L., Briggs P.H., Meier A.L., Singelton M.J., Roth S. (2000) Using imaging spectroscopy to map acidic mine waste. Environmental Science & Technology 34, 47-54.

Türk R., Gärtner G. (2003) Biological soil crusts of the subalpine, alpine and Nival areas in the Alps. In Belnap J., Lange O.L. (Eds): Biological Soil Crusts: Structure, Function, and Management. Springer, Berlin, 67-73.

Ustin S.L., Valko, P.G., Kefauver S.C., Santos M.J., Zimpfer J.F., Smith S.D. (2009) Remote sensing of biological soil crust under simulated climate change manipulations in the Mojave Desert. Remote Sensing of Environment 113, 317-328.

Veste M., Littmann T., Breckle S.W., Yair A. (2001a) The role of biological soil crusts on desert sand dunes in the northwestern Negev, Israel. In Breckle S.W., Veste M., Wucherer W. (Eds): Sustainable Land Use in Deserts. Springer, Berlin, 357-367.

Veste M., Littmann T., Friedrich H., Breckle S.W. (2001b) Microclimatic boundary conditions for activity of soil lichen crusts in sand dunes of the north-western Negev desert, Israel. Flora 196, 465-474.

Viles H. (1995) Ecological perspectives on rock surface weathering: Towards a conceptual model. Geomorphology 13, 21-35.

Viles H.A. (2008) Understanding dryland landscape dynamics: do biological crusts hold the key? Geography Compass 2, 899-919.

Viles H.A., Naylor L.A., Carter N.E.A., Chaput D. (2008) Biogeomorphological disturbance regimes: progress in linking ecological and geomorphological systems. Earth Surface Processes and Landforms 33, 1419-1435.

Warren-Rhodes K.A., Dungan J.L., Piatek J., Stubbs K., Gomez-Silva B., Chen Y., McKay C.P. (2007) Ecology and spatial pattern of cyanobacterial community island patches in the Atacama Desert, Chile. Journal of Geophysical Research-Biogeosciences 112, G04S15.

Weber B., Olehowski C., Knerr T., Hill J., Deutschewitz K., Wessels D.C.J., Eitel B., Büdel B. (2008) A new approach for mapping of Biological Soil Crusts in semidesert areas with hyperspectral imagery. Remote Sensing of Environment 112, 2187-2201.

Wessels D.C.J., van Vuuren D.R.J. (1986) Landsat imagery--its possible use in mapping the distribution of major lichen communities in the Namib Desert, South West Africa. Madoqua 14, 369-373.

Wojciechowski M.F., Heimbrook M.E. (1984) Dinitrogen fixation in alpine tundra, Niwot Ridge, Front Range, Colorado. Arctic and Alpine Research 16, 1-10.

Wynn-Williams D.D. (1993) Soil crust microbes as indicators of environmental change in Antarctica. In Guerrero R., Pedrós Alió C., (Eds): Trends in Microbial Ecology. Spanish Society for Microbiology, Barcelona, 105-108.

Yair A. (2003) Effects of Biological Soil Crusts on Water Redistribution in the Negev Desert, Israel: a Case Study in Longitudinal Dunes. In Belnap J., Lange O.L. (Eds): Biological Soil Crusts: Structure, Function, and Management. Springer, Berlin, 141-152.

Zaady E., Karnieli A., Shachak M. (2007) Applying a field spectroscopy technique for assessing successional trends of biological soil crusts in a semi-arid environment. Journal of Arid Environments 70, 463-477.

Zhang Y.M., Chen J., Wang L., Wang X.Q., Gu Z.H. (2007) The spatial distribution patterns of biological soil crusts in the Gurbantunggut Desert, Northern Xinjiang, China. Journal of Arid Environments 68, 599-610.

Ziegler H., Lüttge U. (1998) Carbon isotope discrimination in cyanobacteria of rocks of inselbergs and soils of savannas in the neotropics. Botanica Acta 111, 212-215.

Zielke M., Ekker A.S., Olsen R.A., Spjelkavik S., Solheim B. (2002) The influence of abiotic factors on biological nitrogen fixation in different types of vegetation in the high Arctic, Svalbard. Arctic, Antarctic, and Alpine Research 34, 293-299.

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Annexe

Version abrégée en français

A partir d’une recension de la bibliographie, cet article dresse le bilan des connexions entre la biogéomorphologie et l’étude des croûtes cryptogamiques (CC). Constituées de nombreux lichens, mousses, algues ou cyanobactéries, les croûtes cryptogamiques constituent un écosystème microbien essentiel dans les régions arides et semi-arides et, dans de nombreux cas, y couvrent le sol de façon dominante (Belnap et Lange 2003 ; fig. 1). Les CC jouent également un rôle clé dans l’analyse des changements écologiques à long terme, et plus spécifiquement dans le registre du stockage du gaz carbonique (fig. 2). Leur structure et leur fonction ont fait l’objet de nombreuses recherches et une classification morphologique a même été proposée (fig. 3 et fig. 4) mais peu de travaux ont pris en compte leurs caractéristiques spatiales. La biogéomorphologie, en tant que discipline étudiant les interactions entre les formes de terrain et le vivant, permet de pallier sensiblement cette carence apparente. En retour, cela permettrait de réduire les insuffisances de la discipline soulignées par L.A. Naylor et al. (2002), parce que les CC permettent de tester le modèle holistique bioérosion/bioprotection/bioconstruction proposé par ces auteurs.

Bien que l’objectif principal de cet article soit d’examiner le rôle important que la biogéomorphologie joue en termes de recherches spécifiques sur les CC, cet exposé synoptique se concentre plus spécifiquement sur les techniques biogéomorphologiques qui pourraient être employées pour étudier non seulement les CC mais aussi la biogéomorphologie des CC elle-même (un aspect totalement inédit à ce jour). L’article présente tout d’abord les concepts de base définissant les CC, la méthodologie d’étude habituelle issue des recherches écologiques et de quelles manières la biogéomorphologie pourrait faire évoluer cette approche traditionnelle. Ensuite, après une présentation rapide des concepts de la télédétection appliquée aux études environnementales, une analyse complète des recherches sur les CC par télédétection est proposée, soulignant une fois encore de quelle manière la biogéomorphologie pourrait contribuer à cet axe de recherche sur les CC. Cette section inclut l’examen des techniques de télédétection passées et présentes, ainsi que des méthodes de télédétection « basiques » (e.g., la vision humaine ; fig. 5) ou plus avancés (e.g., les algorithmes spécifiques employés pour déterminer les types d’espèces par imagerie satellitale). L’article détaille ensuite la manière dont la biogéomorphologie qui se place en première ligne sur le front de la recherche sur les CC pourrait contribuer au comblement de lacunes par l’incorporation de son savoir sur la météorisation (fig. 6). Faire appel à la météorisation pour étudier les CC représente une voie novatrice qui n’a pas encore été entièrement exploitée par la biogéomorphologie ou par la recherche sur les CC. Pourtant, cet axe de développement recèle un fort potentiel heuristique. L’article défend l’idée que la météorisation superficielle peut être le chaînon manquant reliant les recherches connectées aux CC avec la biogéomorphologie, et représente l’un des domaines de la biogéomorphologie qui, bien que fondamental, est souvent négligé en tant que sujet principal de recherches (ce qui n’est d’ailleurs pas spécifique aux recherches sur les CC). Ce rôle fondamental dévolue à la météorisation est justifié par sa capacité à faire des sauts scalaires, un manque commun à la recherche sur les CC (Belnap et Lange, 2003) et à la biogéomorphologie (Naylor et al., 2002).

De plus, parce que la biogéomorphologie est une discipline concernée par les propriétés spatiales telles que la géométrie du relief, le climat et les modalités de la météorisation (avec la capacité de les relier à travers de grands espaces), elle représente un « champ » naturel pour les recherches sur les CC. Au moyen d’une analyse approfondie de la littérature, cet article suggère que la biogéomorphologie peut offrir à la recherche sur les CC de nouveaux modèles, méthodes, approches, et techniques qui développeront davantage le domaine de recherche, tout en contribuant simultanément à l’extension de l’espace d’étude de la biogéomorphologie. Par exemple, puisque les régions urbaines continuent à s’étendre au détriment des terres non cultivées, les modèles dynamiques spatiaux des CC élaborés par la biogéomorphologie peuvent avoir une influence sur les politiques environnementales. En fin de compte, indépendamment des résultats potentiels des recherches consacrées aux CC, la biogéomorphologie, en intégrant la spatialisation des processus et la météorisation, demeure un moteur puissant de la recherche environnementale, dont les CC ne sont qu’un aspect.

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Table des illustrations

Titre Fig. 1 – Biological soil crusts as dominant ground cover in an arid, badlands-topography biome, Grand Staircase-Escalante National Monument, UT (USA).Fig. 1 Les croûtes cryptogamiques comme couverture dominante des sols au sein d’un biome aride et à topographie ravinée, Grand Staircase-Escalante National Monument, Utah (Etats-Unis).
Crédits Photo by authorPhotographie de l’auteur.
URL http://geomorphologie.revues.org/docannexe/image/8071/img-1.jpg
Fichier image/jpeg, 1,2M
Titre Fig. 2 – Lichen- and moss-dominated BSC, near Zion National Park, UT (USA).Fig. 2 Croûtes cryptogamiques à lichens et mousses, à proximité du Parc national de Zion, Utah (Etats-Unis).
Légende It is thought that these types of BSCs may play an important role in the global carbon cycle - especially relative to their mass and relationship with potential SOC drawdown in conjunction with soils - including perhaps unidentified carbon sequestration sites. Photo by author.Il est pensable que ce type de CC puisse jouer un rôle important dans le cycle global du carbone - en regard de leur masse et de leurs liens avec la chute du carbone organique des sols – incluant peut-être des sites de séquestration du carbone encore inconnus. Photographie de l’auteur.
URL http://geomorphologie.revues.org/docannexe/image/8071/img-2.jpg
Fichier image/jpeg, 932k
Titre Fig. 3 – Rugose biological soil crust, McDowell Mountain Regional Park, Sonora Desert, AZ (USA).Fig. 3 Croûte cryptogamique rugueuse, Parc régional de la McDowell Mountain, Désert du Sonora, Arizona (Etats-Unis).
Crédits Photo by authorPhotographie de l’auteur.
URL http://geomorphologie.revues.org/docannexe/image/8071/img-3.jpg
Fichier image/jpeg, 984k
Titre Fig. 4 – Pinnacled BSC, near Zion National Park, UT (USA). Fig. 4 Croûte cryptogamique à pinacles, à proximité du Parc national de Zion, Utah (Etats-Unis).
Légende Photo by author.Photographie de l’auteur.
URL http://geomorphologie.revues.org/docannexe/image/8071/img-4.jpg
Fichier image/jpeg, 820k
Titre Fig. 5 – Spectral difference between wet (left) and dry (right) rugose BSC, Snow Canyon State Park, UT (USA). Fig. 5 Différence spectrale entre des croûtes cryptogamiques rugueuses humide (gauche) et sèche (droite), Snow Canyon State Park, Utah (Etats-Unis).
Légende Real-time video of change in spectral reflectance due to precipitation available here: http://www.youtube.com/​watch?v=1ybZM9MRjxM.Vidéo en temps réel du changement de la réflectance spectrale dû aux précipitations disponible ici : http:/www.youtube.com/watch?v=1ybZM9MRjxM.
URL http://geomorphologie.revues.org/docannexe/image/8071/img-5.jpg
Fichier image/jpeg, 936k
Titre Fig. 6 – Rugose BSC as an epilithic organism, weathering sandstone rock, Near Zion National Park, UT (USA). Fig. 6 Croûte cryptogamique rugueuse épilithique météorisant un grès, à proximité du Parc national de Zion, Utah (Etats-Unis).
Légende This weathering-BSC interaction represents perhaps the most important category of future biogeomorphological research.Cette interaction entre la CC et la météorisation représente probablement la plus importante des pistes de recherche biogéomorphologique futures.
URL http://geomorphologie.revues.org/docannexe/image/8071/img-6.jpg
Fichier image/jpeg, 828k
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Pour citer cet article

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Casey Duane Allen, « Biogeomorphology and biological soil crusts: a symbiotic research relationship », Géomorphologie : relief, processus, environnement, vol. 16 - n° 4 | 2010, 347-358.

Référence électronique

Casey Duane Allen, « Biogeomorphology and biological soil crusts: a symbiotic research relationship », Géomorphologie : relief, processus, environnement [En ligne], vol. 16 - n° 4 | 2010, mis en ligne le 01 décembre 2012, consulté le 24 novembre 2017. URL : http://geomorphologie.revues.org/8071 ; DOI : 10.4000/geomorphologie.8071

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Auteur

Casey Duane Allen

University of Colorado Denver - PO Box 173364 - CB 172 - Denver - CO 80217-3364 (casey.allen@ucdenver.edu)

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© Groupe français de géomorphologie

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