Use of carbon isotope analysis to understand semi‐arid erosion dynamics and long‐term semi‐arid land degradation

Abstract

Many semi-arid areas worldwide are becoming degraded, in the form of C 4 grasslands being replaced by C 3 shrublands, which causes an increase in surface runoff and erosion, and altered nutrient cycling, which may affect global biogeochemical cycling. The prevention or control of vegetation transitions is hindered by a lack of understanding of their temporal and spatial dynamics, particularly in terms of interactions between biotic and abiotic processes. This research investigates (1) the effects of soil erosion on the d 13 C values of soil organic matter (SOM) throughout the soil profile and its implications for reconstructing vegetation change using carbon-isotope analysis and (2) the spatial properties of erosion over a grass-shrub transition to increase understanding of biotic-abiotic interactions by using d 13 C signals of eroded material as a sediment tracer. Results demonstrate that the soils over grass-shrub transitions are not in steady state. A complex interplay of factors determines the input of SOM to the surface horizon of the soil and its subsequent retention and turnover through the soil profile. A positive correlation between event runoff and d 13 C signatures of eroded sediment was found in all plots. This indicates that the d 13 C signatures of eroded sediment may provide a means of distinguishing between changes in erosion dynamics over runoff events of different magnitudes and over different vegetation types. The development of this technique using d 13 C signatures of eroded sediment provides a new means of furthering existing understanding of erosion dynamics over vegetation transitions. This is critical in terms of understanding biotic-abiotic feedbacks and the evolution of areas subject to vegetation change in semi-arid environments.

Carbon loss by water erosion in drylands: implications from a study of vegetation change in the south‐west USA

“…The SNWR is located at the northern margin of the Chihuahuan desert and is a transition zone between four major biomes: the Great Plains grassland, the Great Basin cool shrub steppe, the Mogollon Coniferous woodland and the Chihuahuan warm‐temperate semi‐desert. Soil series are shallow and classified as Turney Loams overlying a well‐developed calcium carbonate layer that occurs between 0.25 and 0.45 m below the soil surface (Turnbull et al ., ).…”

Combined use of stable isotopes and fallout radionuclides as soil erosion indicators in a forested mountain site, South Korea

“…δ 13 C) and nitrogen (i.e. δ 15 N) served as useful tools to determine sources and sinks of carbon, nitrogen or sediments (Alewell et al, 2008;Buck and Monger, 1999;Papanicolaou et al, 2003;Schaub and Alewell, 2009;Turnbull et al, 2008;Fox and Papanicolaou, 2007;Jacinthe et al, 2009). They are also useful for process identification and even process quantification (Conen et al, 2007(Conen et al, , 2008.…”

Biotic and Abiotic Changes in Ecosystem Structure over a Shrub-Encroachment Gradient in the Southwestern USA

“…This 91 model was tested by Schlesinger et al (1996), who found that grasslands showed a fine- shrubland. It is also imperative that research into the structure of ecosystem properties 114 over a shrub-encroachment gradient be carried out at appropriate spatial scales.…”