The Role of Nonphotosynthetic Microbes in the Recovery of Biological Soil Crusts in the Gurbantunggut Desert, Northwestern China

Abstract

The mechanisms regulating the recovery of biological soil crusts (BSCs) due to the presence of nonphotosynthetic microbes were investigated using a soil scalping technique. Microscopic examinations identified the “glue” and “rope” action of bacteria and fungi at the initial stages of recovery of BSCs prior to the appearance of cyanobacteria. Extracellular polymeric substances (EPS) excreted by bacteria principally contained glucose and mannose. The optimum conditions for EPS production included the availability of glucose as the carbon source, the presence of CaCO ₃ (2 g/L), KH ₂ PO ₄ (0.3 g/L), and MgSO ₄ (0.1 g/L), a pH of 7 and incubation at 37°C for 72 h. Crust-forming tests in the laboratory and in the field demonstrated that inoculation of bare sand with oligotrophic bacteria was effective in accelerating the recovery of BSCs. The number of nonphotosynthetic microbes (especially actinomycetes and fungi) recorded in both the crust layer (0–2 cm) and subsurface layer (2–5 cm) was higher after 3 years than after 1 year. Microbial spatial variability of BSCs was related to nutrient status, especially available N.

Keywords:

• developmental BSCs
• extracellular polymeric substances
• Gurbantunggut Desert
• nonphotosynthetic microbes
• nutrient status

We gratefully acknowledge two anonymous reviewers for their valuable comments on the manuscript. We would like to thank the National Research Station of Fukang Desert Ecosystem. The authors gratefully acknowledge Zhang Binchang Zhou Xiaobing, and Wei Meili for their assistance in field sampling and laboratory work. This work was supported by the National Basic Research Program (No. 2009CB825104), the Key Knowledge Innovation Project of the Chinese Academy of Sciences (No. KZCX2-YW-336), the National Natural Science Foundation of China (No. 40901123), and the Xinjiang Province Science Foundation for Youths (No. 2009211B31).

Notes

Data are reported as means ± SD for each of the same physiochemical property presented in Table 2. Means within the same row indicated with different lowercase letters are significantly different (p <0.01) (n = 36).

∗∗Correlation is significant at the 0.01 level (2-tailed).

∗Correlation is significant at the 0.05 level (2-tailed).