Boundaries in Miniature: Two Examples from Soil

Belnap, Jayne; Hawkes, Christine V.; Firestone, Mary K.

doi:10.1641/0006-3568(2003)053[0739:bimtef]2.0.co;2

Cited by 115 publications

(76 citation statements)

References 42 publications

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“…This shift toward an early successional state has critical implications for ecosystem processes and functioning, as early successional biocrusts fix less carbon and nitrogen (11,24,55,56) and lose more carbon and nitrogen via leaching (25). Rapid moss mortality in response to watering treatments was associated with decreased concentrations of ammonium (NH 4 + ) and increased concentrations of nitrate (NO 3 − ), suggesting a strong influence of biocrust composition on local nitrogen processes (35).…”

Section: Discussionmentioning

confidence: 99%

“…The role biocrusts play in soil stability is also a topic of significant public interest, due to the human health and safety issues associated with increasing dust storms. Because different components of the biocrust community (i.e., mosses versus lichens) play different roles in the functioning of drylands (8,10,56,65,66), understanding the factors that control the composition of biocrust communities will be essential to predictions of future dryland function. In addition, because drylands may dominate the interannual variability in global atmospheric CO 2 concentrations (67, 68), state transitions in dryland structure could have effects beyond arid and semiarid systems.…”

Section: Discussionmentioning

confidence: 99%

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Climate change and physical disturbance cause similar community shifts in biological soil crusts

Ferrenberg

Reed

Belnap

2015

Proc. Natl. Acad. Sci. U.S.A.

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260

226

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Biological soil crusts (biocrusts)-communities of mosses, lichens, cyanobacteria, and heterotrophs living at the soil surface-are fundamental components of drylands worldwide, and destruction of biocrusts dramatically alters biogeochemical processes, hydrology, surface energy balance, and vegetation cover. Although there has been long-standing concern over impacts of physical disturbances on biocrusts (e.g., trampling by livestock, damage from vehicles), there is increasing concern over the potential for climate change to alter biocrust community structure. Using long-term data from the Colorado Plateau, we examined the effects of 10 y of experimental warming and altered precipitation (in full-factorial design) on biocrust communities and compared the effects of altered climate with those of long-term physical disturbance (>10 y of replicated human trampling). Surprisingly, altered climate and physical disturbance treatments had similar effects on biocrust community structure. Warming, altered precipitation frequency [an increase of small (1.2 mm) summer rainfall events], and physical disturbance from trampling all promoted early successional community states marked by dramatic declines in moss cover and increases in cyanobacteria cover, with more variable effects on lichens. Although the pace of community change varied significantly among treatments, our results suggest that multiple aspects of climate change will affect biocrusts to the same degree as physical disturbance. This is particularly disconcerting in the context of warming, as temperatures for drylands are projected to increase beyond those imposed as treatments in our study.alternate states | biocrusts | community structure | secondary succession | warming

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Climate change and physical disturbance cause similar community shifts in biological soil crusts

Ferrenberg

Reed

Belnap

2015

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

260

226

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“…There was a strong relationship between the magnitude of the standard deviation of SOC at the interface between genetic horizons and the difference in SOC in the layer above and the layer below the interface (R 2 = 0.99; data not shown). This suggests that the increase in SOC variability at the boundary between genetic horizons is a function of the magnitude of the contrast between SOC on either side of the boundary (Belnap et al 2003). These observations have implications for developing a sampling strategy because the choice of sample increments in relation to the horizon boundaries will influence the variation in SOC concentration observed at depth.…”

Section: Variability Of Soc Concentration and Bulk Density With Depthmentioning

confidence: 98%

“…In terms of system properties, the boundaries between soil horizons are locations where the rates or magnitudes of ecological transfers (e.g., energy or C flow) change abruptly in relation to those within the horizons (Weins et al 1985;Belnap et al 2003). The variability in SOC usually changes with depth through the profile and much of this variability is a consequence of the characteristics of the soil horizons in the soil profile (e.g., their permeability and thickness, the degree to which SOC concentration differs between horizons).…”

mentioning

confidence: 99%

Assessment of the lateral and vertical variability of soil organic carbon

VandenBygaart¹,

Gregorich²,

Angers³

et al. 2007

Can. J. Soil. Sci.

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Accurate predictions of changes in soil organic matter are difficult, at least in part, because of the lack of precision in measurements of soil organic carbon (SOC). This lack of precision is mostly due to the spatial variability in SOC that occurs with depth through the profile and laterally across the soil surface. The objective of this study was to assess the lateral and vertical variability of SOC in several pedologically distinct agricultural soils across Canada. Our goal was to determine the effect of different sampling methods on the precision of SOC measurements, namely: the effect of sampling either by fixed depth or by genetic soil horizon, the influence of compositing samples from different depth increments, and the number of cores required for a minimum detectable difference. Soils were sampled in increments down to 60 cm using a 4 × 3 m grid at six sites: two each from Ontario (Gleysol and Melanic Brunisol), Quebec (Humic Gleysol and Humo Ferric Podzol) and Saskatchewan (Dark Brown Chernozem). At four of the six sites, sampling by genetic soil horizon appeared to increase the precision of SOC measurements, but only when the surface 30 cm of the soil profile was considered. At the other two sites (soil types: Gleysol and Melanic Brunisol) sampling by fixed depth increments was more effective for increasing the precision of SOC measurements than sampling by genetic horizon. The effect of compositing samples from different depth increments had little influence on the precision of SOC measurements for all six soil types. These results suggest that sampling more than two depth increments per soil core has limited advantages for increasing statistical power to detect change in SOC. The high background SOC levels in the Gleysol soil would require a large number of soil cores in order to detect a small change in SOC such as that which would occur in a typical monitoring project. The Chernozem soils had lower spatial variability in SOC than the soil types in eastern Canada. Determining a statistically significant change in SOC of 5 Mg ha-1 would be difficult with the sampling design used in this study. Key words: Soil organic carbon, statistical power, sampling design, coefficient of variation, spatial variability, Canada

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“…In addition, BSCs contribute to surface organic matter pools and alter soil fertility by N fixation. These soil surface communities are a dominant component of many arid ecosystems and, in undisturbed areas, can make up .70% of living cover across the landscape (Belnap et al 2003).…”

Section: Introductionmentioning

confidence: 99%

Untangling the biological contributions to soil stability in semiarid shrublands

Chaudhary

Bowker

O'Dell³

et al. 2009

Ecological Applications

161

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Abstract. Communities of plants, biological soil crusts (BSCs), and arbuscular mycorrhizal (AM) fungi are known to influence soil stability individually, but their relative contributions, interactions, and combined effects are not well understood, particularly in arid and semiarid ecosystems. In a landscape-scale field study we quantified plant, BSC, and AM fungal communities at 216 locations along a gradient of soil stability levels in southern Utah, USA. We used multivariate modeling to examine the relative influences of plants, BSCs, and AM fungi on surface and subsurface stability in a semiarid shrubland landscape. Models were found to be congruent with the data and explained 35% of the variation in surface stability and 54% of the variation in subsurface stability. The results support several tentative conclusions. While BSCs, plants, and AM fungi all contribute to surface stability, only plants and AM fungi contribute to subsurface stability. In both surface and subsurface models, the strongest contributions to soil stability are made by biological components of the system. Biological soil crust cover was found to have the strongest direct effect on surface soil stability (0.60; controlling for other factors). Surprisingly, AM fungi appeared to influence surface soil stability (0.37), even though they are not generally considered to exist in the top few millimeters of the soil. In the subsurface model, plant cover appeared to have the strongest direct influence on soil stability (0.42); in both models, results indicate that plant cover influences soil stability both directly (controlling for other factors) and indirectly through influences on other organisms. Soil organic matter was not found to have a direct contribution to surface or subsurface stability in this system. The relative influence of AM fungi on soil stability in these semiarid shrublands was similar to that reported for a mesic tallgrass prairie. Estimates of effects that BSCs, plants, and AM fungi have on soil stability in these models are used to suggest the relative amounts of resources that erosion control practitioners should devote to promoting these communities. This study highlights the need for system approaches in combating erosion, soil degradation, and arid-land desertification.

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Boundaries in Miniature: Two Examples from Soil

Cited by 115 publications

References 42 publications

Climate change and physical disturbance cause similar community shifts in biological soil crusts

Climate change and physical disturbance cause similar community shifts in biological soil crusts

Assessment of the lateral and vertical variability of soil organic carbon

Untangling the biological contributions to soil stability in semiarid shrublands

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