Moss patch size and microhabitats influence stoichiometry of moss crusts in a temperate desert, Central Asia

Abstract

Desert mosses, which are important stabilizers in desert ecosystems, are distributed patchily as biological soil crusts in arid lands. Patch size and microhabitats of moss are affected by human activities in deserts, such as grazing, oil exploration, and reclamation. Moss patches as a microecosystem, is a functional unit. It is not clear how patch size of moss influences the stoichiometry of moss and soil. We examined the effects of moss patches of different sizes on moss and soil stoichiometry, and moss growth strategies in different microhabitats. The dominant moss (Syntrichia caninervis Mitt.) of biological soil crusts in the Gurbantunggut Desert was selected to study carbon (C), nitrogen (N), and phosphorus (P) contents in moss patches. Soil inside and under the moss patches was analyzed from open areas and under the canopy of living shrubs. The C, N, and P stoichiometry of the moss and soil, and soil enzyme activities were measured. The effects of patch size on C, N, and P characteristics were microhabitat dependent. Moss N content in above-ground parts, moss C, N, and P contents in below-ground parts, and sucrase activity in soil under moss patches significantly increased with increase in patch size in open areas. Under the canopy of living shrubs, patch size had no significant influence on moss C, N, and P contents, soil nutrient contents, and soil enzyme activities. Patch size effects were stronger for moss and soil C, N, and P characteristics in open areas than those under the canopy of living shrubs. Moss N and P contents in above-ground parts were significantly higher than those in below-ground parts, whereas moss C:N and C:P ratios in above-ground parts were significantly lower than those in below-ground parts. Moss C, N, and P stoichiometry was weakly correlated with soil nutrient contents and enzyme activities. Structural equation modeling showed that the models for C, N, and P cycling differed between open areas and under the canopy of living shrubs. The effects of patch size on the multifunctionality of the moss microecosystem were regulated by microhabitats. Increase in patch size benefits moss growth more in open areas than under the canopy of living shrubs. Shrubs provide a protected environment for moss plants and drive moss growth. Above-ground parts of mosses host more functions essential for growth and photosynthesis than below-ground parts of moss patches in a temperate desert. Patch size accounted for positive effects of moss stoichiometry in open areas. Patch size may influence the ecological function of moss patches. Shrubs dominantly drive moss growth compared with patch size effects.