平顶山、长白山、赛罕乌拉森林土壤微生物群落结构分析

The Microbial Community of Three Mountains Pingding, Changbai and Saihanwula Based on the Analysis of Phospholipid Fatty Acids(PLFAs)

土壤微生物是整个生态系统养分和能源循环的关键和动力。土壤的生物多样性比陆地上其他任何生态系统都要丰富，这种丰富的生物多样性导致了对其群落结构和生态功能难以预测。在一系列基于分子微生物学、生物地球化学和生理学的土壤微生物群落结构研究方法中，磷脂脂肪酸技术（PLFA）以磷脂作为分析成分，因其组成和含量在同一种微生物中通常相对稳定、可遗传，且具有仅在活体微生物中存在的特性，所以，PLFA技术可指示特定生物或生物种群的存在和状况，现已被广泛运用于土壤微生物群落结构分析中，监测微生物群落的动态变化。本研究选取了中国东北地区海拔高度达1000 m以上的典型森林生态系统：小兴安岭平顶山、吉林长白山、内蒙赛罕乌拉森林土壤为研究对象，采用PLFA方法，分析了土壤中微生物的生物量和细菌Bacteria、真菌Fungus、革兰氏阳性菌Gram＋Bacteria和革兰氏阴性菌Gram-Bacteria 4种微生物群落结构。在此基础上使用相关分析、主成分分析等统计方法，揭示了土壤微生物群落结构与海拔高度、森林类型及其土壤理化因子的相互关系，为开展森林生态系统生物多样性与元素循环和气候变化的相关研究提供基础资料。研究得出以下结论：（1）对我国平顶山、长白山和赛罕乌拉背景森林中不同植被类型12个土壤样品的现场测定与采样分析，结果表明，土壤总有机碳（TOC）范围为3.15%-16.3%，pH值范围为3.5-4.8，碳氮比（C/N）为12.1-18.4，土壤含水率范围为13.3%-74.5%，采样时土壤温度为8.0-18.8℃。（2）样品的PLFAs总含量代表了土壤微生物总生物量，范围为27.39-237.63μg·g^1。赛罕乌拉土壤中微生物的生物量（PLFAs总量）最高；而平顶山土壤中的细菌含量、真菌含量和革兰氏阳性菌显著高于其余两座山。革兰氏阳性菌与阴性菌的比值在平顶山土壤中最大（4.19），明显高于长白山（3.14）和赛罕乌拉（2.39）；而真菌与细菌比值却与之相反（平顶山0.55、长白山0.69、赛罕乌拉1.05）。（3）利用SPSS软件，对不同微生物群落与环境因子进行相关分析，结果表明：细菌的含量与纬度呈显著正相关，而和土壤C/N呈显著负相关（P＜0.01）；真菌群落总体上与土壤C/N呈现负相关性（P＜0.05）。进一步对细菌群落和代表真菌群落的两个主要PLFAs成分（C18：1ω9、C18：2ω6,9）与土壤碳氮比做相关分析发现：C18：1与土壤碳氮比呈现显著负相关（P＜0.01），而C18：2ω6,9与土壤碳氮比的相关关系并不明显。因此，我们认为单一种类PLFA作为生物标记物随土壤碳氮比变化的灵敏度更高。（4）主成分分析表明：土壤微生物多样性主要受纬度所导致植被类型差异的影响（P＜0.01），且与土壤碳氮比呈负相关、土壤含水率呈正相关（P＜0.05）。

Soil microbes is the key and motivation of nutrient and energy cycling in terrestrial ecosystem. It is hard to evaluate the community structure and ecological functions of soil ecosystem for its abundant diversity. Phospholipid fatty acid （PLFA）, a relatively stable and heritable biomarker of live microorganism, which can be used to indicate the exist and situation of specific organism or population, has been widely used in elucidating the dynamic change of microbial community in soil. The present study evaluated soil microbial biomass, Bacteria, Fungus, Gram＋ Bacteria and Gram- Bacteria composition in typical forest soils of Chinese northeast area （including Pingding Mountain, Changbai Mountain and Saihanwula Mountain） with the analysis of phospholipid fatty acid （PLFA）. Furthermore, we investigated how the forest soil microbial absolute content and distribution change with various environmental factors. The major conclusions are as follows：（1）A total of 12 soil samples of different vegetation types from Pingding Mountain, Changbai Mountain and Saihanwula Mountain background forests were analyzed for PLFAs, C/N, TOC, and pH, following the field test of their environmental factors such as soil temperature and moisture. The results showed that the total organic carbon （TOC） ranged from 3.15%-16.3%, the carbon to nitrogen ratio （C/N） ranged from 12.1-18.4, the pH value ranged from 3.5-4.8, the moisture content ranged from 13.3%-74.5%and the soil temperature while sampling was 8.0-18.8 ℃, respectively. （2）The total PLFAs content represents the biomass of soil microbes, which was in the range of 27.39-237.63 μg·g^-1. Soil microbial biomass in Saihanwula Moutain was highest among the three mountains, while the contents of bacteria, fungi and G＋-bacteria in Pingding Moutain were significantly higher than the other two mountains. The ratio of G＋-bacteria to G--bacteria （G＋/G-） in Pingding Mountain （4.19） was also higher than Changbai Mountain （3.14） and Sahanwula Mountain （2.39）. On the contrary, the ratio of fungi to bacteria （F/B） was totally different from G＋/G-with Saihanwula Moutain （1.05） being the highest, followed by Changbai Mountain （0.69） and Pingding Mountain （0.55）. （3）We examined the correlation between different microbial communities and environmental factors using SPSS software. The results showed that the content of bacteria in forest soil significantly correlated with latitude and C/N （P〈0.01）;fungi were negatively correlated with C/N （P〈0.05） generally. Further correlated analysis between two main PLFAs representing fungi （C18：1ω9、C18：2ω6,9） with C/N demonstrated that C18：1ω9 was significantly correlated with C/N （P〈0.01）, whereas C18：2ω6,9 was not significantly correlated with C/N. Therefore, the single PLFA as biomarker is probably more sensitive to the change of C/N. （4）The principal components analysis indicated that the soil biodiversity was determined by the vegetation types （P〈0.01）, and it was influenced by soil C/N and soil moisture content as well （P〈0.05）.