Unit of Research Plant Biodiversity and Ecosystems in Arid Environments, University of Sfax, Sfax, Tunisia.
School of Civil and Environmental Engineering, Yonsei University, Seoul, 03722, South Korea.
Microb Ecol. 2019 Jan;77(1):201-216. doi: 10.1007/s00248-018-1219-8. Epub 2018 Jun 19.
Arid ecosystems constitute 41% of land's surface and play an important role in global carbon cycle. In particular, biological soil crusts (BSC) are known to be a hotspot of carbon fixation as well as mineralization in arid ecosystems. However, little information is available on carbon decomposition and microbes in BSC and key controlling variables for microbial activities in arid ecosystems. The current study, carried out in South Mediterranean arid ecosystem, aimed to evaluate the effects of intact and removed cyanobacteria/lichen crusts on soil properties, soil enzyme activities, and microbial abundances (bacteria and fungi). We compared five different treatments (bare soil, soil with intact cyanobacteria, soil with cyanobacteria removed, soil with intact lichens, and soil with lichens removed) in four different soil layers (0-5, 5-10, 10-15, and 15-20 cm). Regardless of soil treatments, activities of hydrolases and water content increased with increasing soil depth. The presence of lichens increased significantly hydrolase activities, which appeared to be associated with greater organic matter, nitrogen, and water contents. However, phenol oxidase was mainly controlled by pH and oxygen availability. Neither fungal nor bacterial abundance exhibited a significant correlation with enzyme activities suggesting that soil enzyme activities are mainly controlled by edaphic and environmental conditions rather than source microbes. Interestingly, the presence of lichens reduced the abundance of bacteria of which mechanism is still to be investigated.
干旱生态系统占陆地表面的 41%，在全球碳循环中发挥着重要作用。特别是生物土壤结皮（BSC），被认为是干旱生态系统中碳固定和矿化的热点。然而，关于 BSC 中的碳分解和微生物以及干旱生态系统中微生物活性的关键控制变量的信息很少。本研究在南地中海干旱生态系统中进行，旨在评估完整和去除蓝藻/地衣结皮对土壤性质、土壤酶活性和微生物丰度（细菌和真菌）的影响。我们在四个不同的土壤层（0-5、5-10、10-15 和 15-20 cm）中比较了五种不同的处理（裸土、含有完整蓝藻的土壤、去除蓝藻的土壤、含有完整地衣的土壤和去除地衣的土壤）。无论土壤处理如何，水解酶和含水量的活性随着土壤深度的增加而增加。地衣的存在显著增加了水解酶的活性，这似乎与更多的有机质、氮和水分含量有关。然而，多酚氧化酶主要受 pH 值和氧气供应的控制。真菌和细菌丰度均与酶活性无显著相关性，表明土壤酶活性主要受土壤和环境条件的控制，而不是源微生物。有趣的是，地衣的存在减少了细菌的丰度，其机制仍有待研究。
