Steppe grasslands are distributed over vast areas in arid and semiarid regions of Eurasia. However, steppe grasslands face desertification or degradation caused by human over‐activity. In the last decades, steppe regions have seen increased areas of crop cultivation and subsequent abandonment due to inappropriate agricultural management. Land degradation of abandoned croplands has become a common problem in the Inner Mongolia Autonomous Region, China. A field survey was conducted in the Xilingol steppe, and vegetation was classified into three groups. Based on comparisons of species composition and soil characters, group 1 represents steppe grassland, group 2 represents abandoned croplands and group 3 represents yardangs. The typical indicator species of steppe, abandoned croplands and yardangs are Leymus chinensis, Cleistogenes squarrosa and Elymus dahuricus, respectively. Abandoned croplands are exposed to wind and rain, resulting in soil erosion, which not only increases coarse sand content but also decreases total carbon and total nitrogen in the soil. We found that soil condition is an important factor affecting the early stages of secondary succession in abandoned croplands and that farming in typical steppes might contribute to land degradation. We concluded that abandoned croplands can be converted to yardangs by erosion. The extension of yardangs might then lead to desertification in steppe regions. Land managers should be aware that farming in typical steppes is associated with a risk of desertification. The degree of degradation of steppe can be measured by monitoring these indicator species.
We determined how the vegetation and spatial heterogeneity (spatial variation) in species richness and species composition in salinized grasslands are affected by soil salinity level, and whether the Grime's hypothesis regarding species richness is accepted, to understand vegetation on salinized soil. To address these questions, we surveyed three grassland sites in Inner Mongolia. All sites had been degraded heavily by livestock grazing, and had different salinity levels: heavy (electrical conductivity 1.18–8.15 dS m−1), intermediate (0.38–0.70 dS m−1) and non‐salinized (0.07–0.20 dS m−1). We set 50 square quadrats (0.25 m2 per quadrat), divided into four sub‐quadrats (0.0625 m2 each), along two 25 m transects in each site, and recorded all plant species in each sub‐quadrat. The species richness of the sites per 0.25 m2 was in the order: intermediate salinity > non‐salinized > heavy salinity. At the heavy and intermediate sites, the spatial heterogeneity of vegetation per sub‐quadrat was higher than expected from a random pattern, but not at the non‐salinized site. At the heavily salinized site, the spatial patterns of two halophytes with the highest occurrences drove the high spatial heterogeneity in species richness. In contrast, at the non‐salinized site, two low‐level halophytes with the highest occurrences determined the random pattern. The intermediate salinity site, where high‐ and low‐level halophytes could coexist in accordance with small‐scale spatial changes in salinity, had the highest species richness with relatively high spatial heterogeneity (which accepted the Grime's hypothesis). Our working hypothesis for remediating vegetation and soil in salinized grasslands is to inhibit grazing, and to grow species that accumulate organic matter in soil. For this, halophyte species with large spatial heterogeneity/body size would be effective.
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