Chang Chenhui, Wu Fuzhong, Yang Wanqin, Xu Zhenfeng, Cao Rui, He Wei, Tan Bo, Justine Meta Francis
Long-term Research Station of Alpine Forest Ecosystems, Institute of Ecology & Forestry, Sichuan Agricultural University, Chengdu, PR China.
Collaborative Innovation Center of Ecological Security in the Upper Reaches of Yangtze River, 8 Chengdu, China.
PLoS One. 2017 Aug 7;12(8):e0182576. doi: 10.1371/journal.pone.0182576. eCollection 2017.
Little information has been available on the shifts in the microbial community in decaying fallen logs during critical periods in cold forests. Minjiang fir (Abies faxoniana) fallen logs in decay classes I-V were in situ incubated on the forest floor of an alpine forest in the eastern Tibet Plateau. The microbial community was investigated during the seasonal snow cover period (SP), snow thawing period (TP), early growing season (EG) and late growing season (LG) using Phosphorous Lipid Fatty Acid (PLFA) analysis. Total microbial biomass and microbial diversity in fallen logs were much more affected by critical period than decay class, whereas decay class had a stronger effect on microbial diversity than on microbial biomass. Abundant microbial biomass and microbial diversity in logs even without the cover of snow were observed in winter, which could not be linked to thermal insulation by snow cover. The freshly decayed logs functioned as an excellent buffer of environmental variation for microbial organisms during the sharp fluctuations in temperature in winter. We also found distinct decay patterns along with seasonality for heartwood, sapwood and bark, which requires further detailed research. Gram- bacteria mainly dominated the shifts in microbial community composition from SP to EG, while fungi and Gram+ bacteria mainly dominated it from SP to TP. Based on previous work and the present study, we conclude that fallen logs on the forest floor alter ecological processes by influencing microbial communities on woody debris and beneath the soil and litter. Our study also emphasizes the need to maintain a number of fallen logs, especially fresh ones, on the forest floor.
关于寒冷森林关键时期腐烂倒木中微生物群落的变化，目前可用信息较少。在青藏高原东部的一片高山森林林地上，对处于I - V腐烂等级的岷江冷杉（Abies faxoniana）倒木进行了原位培养。在季节性积雪期（SP）、融雪期（TP）、生长季早期（EG）和生长季晚期（LG），采用磷脂脂肪酸（PLFA）分析方法对微生物群落进行了调查。倒木中的总微生物生物量和微生物多样性受关键时期的影响远大于腐烂等级，而腐烂等级对微生物多样性的影响比对微生物生物量的影响更强。冬季，即使没有积雪覆盖，倒木中也存在丰富的微生物生物量和微生物多样性，这与积雪的保温作用无关。在冬季温度急剧波动期间，新腐烂的倒木为微生物提供了极佳的环境变化缓冲。我们还发现，心材、边材和树皮的腐烂模式随季节变化各异，这需要进一步详细研究。从SP到EG，革兰氏阴性菌在微生物群落组成变化中占主导地位，而从SP到TP，真菌和革兰氏阳性菌占主导地位。基于之前的研究和本研究，我们得出结论，森林地面上的倒木通过影响木质残体以及土壤和凋落物之下的微生物群落来改变生态过程。我们的研究还强调了在森林地面保留一定数量倒木的必要性，尤其是新鲜倒木。
