Changes in soil properties in different land use types in a desert-oasis ecotone, Inner Mongolia, China.

This study aims to examine the changes in soil chemical properties (soil organic matter, SOM; available nitrogen, AN; available phosphorus, AP; available potassium, AK; total nitrogen, TN; total phosphorus, TP and pH) in three depths (i.e. 0-5, 5-10, 10-20 cm) from different land use types of the Green Beach Desert-oasis Ecotone, Inner Mangolia, China. Using soil chemical properties data, comprehensive soil quality index (SQI) was calculated based on principal component analysis (PCA) of variables across different soil depths for different land use types. Results showed that soil properties differed significantly according to land use type. The eight land use types all showed decreases in TN and TP meaning values for these variables fell below those measured from the control plot (bare ground or 'CK'). Farmland and protective forest soils showed higher AK, AN, AP and SOM contents with protective forest soil the higher of the two. This contributed to accumulation of soil nutrients. Soil quality index results showed that the soil quality index of abandoned farmland in 5-10 cm and 10-20 cm soil layer is the highest among the eight types of land, therefore, the 5-10 cm and 10-20 cm soil layers of abandoned farmland could help to optimize soil nutrients. The 0-5 cm layer of the protective forest soil also showed obvious nutrient accumulation. These results provide basic reference data and trends for soil quality assessment in arid, ecologically fragile areas.

Spatial distributions of salt-based ions, a case study from the Hunshandake Sandy Land, China.

Soil water soluble base ion salt-based ion concentrations are critical parameters for estimating soil buffer capacity and vegetation productivity. Ionic content clearly covaries with the distribution of plant communities. Previous studies on salt-based ions in soils focused primarily on ion migration and its relationships with vegetation growth. Few studies have sought to characterize larger scale spatial distribution of salt-based ions or correlation with climatic and plant community characteristics. This study used ion chromatography to analyze the salt-based ion content (Ca2+, Mg2+, Na+ and K+) of surface soils from the Hunshandake sandy lands. Statistical methods were used interpret spatial variation. Results showed that the average content of salt-based ions in Hunshandake sandy land was 86.57 mg/kg. Average values ranked as Ca2+ > Na+ > K+ > Mg2+ but concentrations also exhibited uneven spatial distributions. Horizontal spatial variation in Ca2+, Mg2+ and Na+ ions showed these ions gradually decrease from northwest to southeast. Potassium ions (K+) showed no obvious spatial variation trends. Ions varied significantly across different soil layers but their average concentrations ranked as K+>Na+>Ca2+>Mg2+ (from shallow to deep). The 20-30 cm soil layer contained the highest salt ion concentrations. Of the four base ions, only K+ ions appeared in surface samples. In terms of water soluble base ion available salt-based ions, Ca2+ occurred in the highest concentrations along the north and west side of the study area. K+ ions occurred in the highest concentrations along the south and east sides of the study area. Na+ concentrations did not show a consistent spatial pattern. Statistical analysis detected significant correlations of normalized ion concentration parameters (Ca2+/CECT, K+/CEC, effective water soluble base ion salt-based ions) and the total species number, average species number and total biomass of the plant communities (P <0.05). This study can help inform understanding of soil water transport in sandy areas and provide a reference for interpreting ecosystems in arid regions.

Using sediment grain size characteristics to assess effectiveness of mechanical sand barriers in reducing erosion.

Wind and sand control features are important tools for limiting desertification. Sand barriers are one of the oldest engineering measures used to reduce wind-sand hazards. Their efficacy and exact mechanism by which they work has remained a topic of scientific debate however. Sediment grain-size distributions can help constrain their utility and function. This research analyzed sediment grain size distributions in samples collected from areas around six different types of sand barriers installed along the southeastern margin of the Tengger Desert. Results were compared with sediment from a bare dune area (no barriers) used as a control. The barrier area samples contained high proportions of coarse sand and relatively low proportions of silty sand and very fine sand. Fine and medium sand were present but clay was not. The lower proportions of fine sand and higher proportions of coarse sand relative to bare dunes documented an effective reduction in aeolian transport by the barriers. Samples from the barrier areas also showed poorer sorting relative to bare dune areas. This appeared as lower kurtosis values and wider frequency distribution curves relative to those measured from bare dunes samples. The wider cumulative frequency curves for samples from the barrier areas likely reflects the higher proportion of coarse-grained material. The Straw/1.5 and PLA/1 barrier types hosted greater sediment accumulation than that observed for the other barrier types (Straw/1, PLA/1.5, Mixed/1 and Mixed/1.5). Sediment grain size distributions showed that the base and middle slope areas of the dune experienced deposition, while the top of the dunes experienced erosion. The Straw/1 barrier (straw installed as a 1 × 1 m grid) performed best in terms of installation costs and protective effects for the study area. This study demonstrates how sediment grain size distributions can be used as quantitative proxies for sand barrier performance in reducing desertification.