Water availability and species identity control shrub colonization in abandoned semiarid steppes

Abstract

Highlights• Shrub cover has increased in former agricultural lands worldwide.• Colonization rates are explained by the identity of shrub species.• Species idiosyncratic effects are contingent on water availability.• Abiotic attributes, such as aspect or rock cover, played a lesser role. 1 AbstractThe increase in shrub cover and density is a widespread phenomenon in drylands worldwide. Its causes and consequences are complex and strongly idiosyncratic. Detailed knowledge of the rate of shrub colonization, and its abiotic and biotic drivers is crucial to fully understand and manage these areas. We used a set of aerial photographs (1956, 1978, 1985, 1998 and 2009) describing early, gradual and late recruitment, respectively. Differences in shrub patch colonization rate were related to the identity of patch-forming species, but contingent on water availability. Total increases in shrub patch density were larger when patches were dominated by late colonizer species. Overall shrub patch dynamics was mostly related to the identity of patchforming species and climatic conditions, and to a lesser extent physical factors such as aspect and rock cover. Given the sensitivity of patch-forming species to climatic conditions, new challenges for steppe management will emerge over the next decades. Species able to thrive under harsh conditions may increase their dominance at the expense of species adapted to less demanding conditions.

The use of branch piles to assist in the restoration of degraded semiarid steppes

“…In our study, each branch pile cost 183 euros (USD 225). Considering an average shrub patch density in the studied steppes of 67 patches/ha (Rolo et al ), the total cost of restoring 1 ha would be 12,261 euros (USD 15,075), provided that every pile generates a new patch. This amount is 2.5–6 times higher than costs of planting seeds (2,030–4,852 euros/ha; 2,491–5,953 USD/ha; Cuenca ).…”

Review on: The Role of Improving Soil Carbon Sequestration to Mitigate Global Climatic Change and Optimize Biogeochemical Cycle of Carbon

“…Because of burning fossil fuels, cultivation and draining of grasslands and wetlands, deforestation, and landuse conversions, there has been increased interest in developing methods to sequester atmospheric CO2 (Sundermeier et al 2005;Baker et al 2007;Lal 2009). In agricultural land areas, NT systems have been proposed as an alternative to replace intensive tillage systems such as MP and CP as a way to sequester SOC (Ogle et al 2012).…”

“…In agricultural land areas, NT systems have been proposed as an alternative to replace intensive tillage systems such as MP and CP as a way to sequester SOC (Ogle et al 2012). Several researchers (Liebig et al 2005;Lal et al 1998;Johnson et al 2005;Kumar et al 2012) have recommended that converting from MP or CP systems to NT has a large potential for SOC sequestration, but NT does affect the distribution of SOC within the soil profile (Baker et al 2007;Luo et al 2010;Vanden Bygaart et al 2003;Sundermeier et al 2005;Ogle et al 2012). When NT, CP, and MP are under a non-steady state (Olson 2010) all three tillage systems may fail to sequester a significant amount of SOC.…”

“…Van Oost et al (2007) found that the eroded C gets buried at the bottom of the slope where decomposition rates are slower. According to Baker et al (2007), this difference in SOC distribution can be attributed to different properties of PT vs. NT soils. In general, NT soils are more compacted with greater bulk density, particularly at the soil surface, than recently plowed soils (Kitur et al 1993).…”

“…In general, NT soils are more compacted with greater bulk density, particularly at the soil surface, than recently plowed soils (Kitur et al 1993). Furthermore, crop residues left on the soil in NT causes a decrease in soil temperature early in the growing season, which limits root growth (Baker et al 2007). West and Post (2002) reviewed 137 paired studies, but in the studies considered, SOC concentration was only measured in the top 15 or 30 cm of soil (Baker et al 2007).…”