PJB-2017-594
Impacts of environmental heterogeneity on the distribution pattern of moss crust patches in a temperature desert in Central Asia
xuehua JI
Abstract
Moss crusts are the highest developmental stage of biological soil crusts in arid and semiarid ecosystems worldwide, and they thus represent special biological features and ecological functions compared with algal and lichen crusts. In natural conditions, patches are the elementary unit of moss crusts to perform their ecological functions. However, to date, the quantitative feature, distribution pattern, ecological effect and relationship with environmental factors of moss patches in desert ecosystems remain unclear. In this study, 66 quadrats (1 m � 1 m) in 22 plots were established, and 3303 moss patches and relevant environmental variables were investigated and quantified in the Gurbantunggut Desert, China. Thirty-six patch classes were first defined; next, data were analyzed using univariate and multivariate techniques. Moss crusts accounted for 11.73% of the plot area on average, and the mean moss patch area was 23.43 cm2. Small patches were absolutely dominant, indicating a notably serious fragmentation of moss crusts. Significant density-dependent effects between patch density and size, humped relationships between patch size and moss plant density, and soil water content under moss patches were observed. The overall distribution of moss crusts showed a tendency of moss patch size and moss plant density decreasing from the southeastern part of the desert to the northwestern part, while moss patch density showed the opposite trend. Pearson�s correlation analysis and nonmetric multidimensional scaling analysis consistently demonstrated that the distributions of moss patches were dominantly influenced by non-moss crust coverage, sand particle size, latitude, mean annual precipitation (MAP) and mean annual temperature. Of these parameters, fine sand, high MAP and low latitude were beneficial to the development of moss crusts. Consequently, the factors influencing the distribution pattern of moss crusts are complex and contain the historical factor (e.g., sand particle size), modern climate and natural and human disturbances.
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