Characteristics of Soil Environment Variation in Oasis–Desert Ecotone in the Process of Oasis Growth

Cele Oasis on the southern edge of Tarim Basin was used to investigate the impact of human activity on the soil environment of the oasis– desert ecotone during the oasis expansion process. Since farmland is extending into the oasis–desert ecotone during oasis expansion, reclaimed farmland and control plots within the ecotone were investigated. The variations in soil moisture, soil nutrients and soil particle-size distribution of the two plots to a depth range of 0–100 cm were discussed. The soil moisture of each layer in the farmland to a depth of 0–100 cm differed significantly from that in the control plot; the former was generally higher than the latter in the same layer, particularly during the farming period (i.e. April–September). Agricultural soil moisture showed a time-variation rule from multimodal to unimodal with increased depth. Soil moisture of the control plot showed a generally monotonic increasing trend with increased depth; however, for the farmland plot, there was a unimodal increasing trend of initial increase and then a decrease with increased depth. Each layer of the farmland plot had a higher soil nutrient composite index than that of the control plot; however, this improving effect of farmland reclamation on soil nutrient conditions in the oasis–desert ecotone decreased with increased depth. The variation of soil particle-size showed a particular regularity under the influence of cultivation, i.e. silt and clay contents in farmland increased obviously and sand contents decreased.