Divergent Responses of Plant Communities under Increased Land-Use Intensity in Oasis-Desert Ecotones of Tarim Basin

Abstract

The conversion of oasis-desert ecotones for agricultural use is a recent and ongoing trend. To evaluate the impacts of different land-use types and disturbance intensities (distance from farmland) on ecotonal vegetation, we investigated the plant community structure and growth of dominant species in an oasis-desert ecotone in the southern Taklimakan Desert. We established six 100 × 100 m plots, each associated with a particular land-use type in two respective locations: farmland margins and peripheral desert. Twelve and five species, respectively, were recorded at these two sites, with the latter containing fewer annual species. Species richness in the ecotone corresponded to the size of the investigated area. Plant coverage was generally two to eight times higher in the farmland margins than in peripheral desert areas. The species richness, plant coverage, and diversity indices at the two sites varied according to the land-use type. An increased distance from farmland corresponded to changes in the community structure for some land-use types, whereas in most instances, species richness differed by only one species within 100 m of farmland. Plant density and coverage were relatively higher in subplots located 0–20 m away from farmland than in other subplots, although these differences were nonsignificant. Whereas land-use types affected some of the growth indices of the dominant species Alhagi sparsifolia, we observed few significant distance effects. These results indicate that plant community structures and the growth of dominant species vary with landscape heterogeneity or land-use type. The distance effects are dependent on the land-use type. Over a short time period, irrigation is beneficial for the establishment of annual plants around farmland, but it is not beneficial for perennial plants that use ground water. However, further assessments of the long-term effects of agricultural activities on plant community structures, especially on dominant shrubs, are needed.