罕山土壤微生物群落组成对植被类型的响应

选取分布在中国东北部地区的阔叶林-针叶林-亚高山草甸这一明显的植被垂直带谱来研究植被类型对土壤微生物群落组成的影响。选取5种植被类型-山杨(Populus davidiana)(1250—1300 m),山杨(P.davidiana)与白桦(Betula platyphylla)的混交林(1370—1550 m),白桦(B.platyphylla)(1550—1720 m),落叶松(Larix principis-rupprechtii)(1840—1890 m),亚高山草甸(1900—1951 m),采用磷脂脂肪酸(Phopholipid Fatty Acids,PLFAs)分析方法测定不同植被类型下的土壤微生物群落组成。分别采用主成分分析(Principal Components Analysis,PCA)以及冗余分析(Redundancy Analysis,RDA)来解释单种特征PLFAs的分异以及土壤理化指标与微生物PLFAs指标间的相关性。结果表明不同植被类型下土壤有机碳(SOC)对土壤微生物PLFAs总量,各类群(真菌(f)、细菌(b)、革兰氏阳性菌(G+)、革兰氏阴性菌(G-))生物量以及群落结构影响显著;土壤微生物PLFAs总量及各类群的生物量随土层加深总体上表现降低趋势,G+/G-和f/b分别随土层加深总体上表现升高趋势。不同植被类型下,阔叶混交林土壤PLFAs总量及各类群生物量总体上最高;针叶林比阔叶林下的f/b和G+/G-高;亚高山草甸下低的p H值对有机碳的可利用性有一定的抑制作用,导致f/b和G+/G-的值相对较高。总之,不同植被类型下SOC对土壤微生物群落组成的影响最为显著,而较低的p H对有机碳的可利用性有一定的抑制作用;真菌对植被类型的变化比细菌更敏感,而细菌更易受可利用性养分和p H变异的影响,这对预测不同林型下的土壤微生物群落组成有重要的启示作用。

Response of soil microbial community composition to vegetation types

There is no unifying conclusion among the considerable studies of soil microbial community composition under different vegetation types. We selected a distinct vertical vegetation distribution belt consisting of broad-leaved forests, coniferous forests, and subalpine meadows to study the effect of vegetation types on soil microbial community composition. Soil samples were collected at three different depths (0-5cm, 5-10cm, 10-20cm) from sites of five vegetation types. These sites were distinguished by their dominating vegetation: poplar (Populus davidiana) (1250-1300m), poplar (P. davidiana) mixed with birth (Betula platyphylla) (1370-1550m), birth (B. platyphylla) (1550-1720m), larch (Larix principis-rupprechtii) (1840-1890m) and subalpine meadow (1890-1951m). Soil microbial community compositions under the various vegetation types were determined by phospholipid fatty acid (PLFA) analysis. Ordination of individual PLFA signatures and correlations among soil properties and soil microbial PLFA indicators were analyzed by principal components analysis (PCA) and redundancy analysis (RDA), respectively. The results indicated that total PLFA contents of soil microbial community, biomasses of four main microbial taxa (fungi (f), bacteria (b), gram-positive bacteria (G+), gram-negative bacteria (G-)), and microbial community structure were significantly affected (P < 0.05) by soil organic carbon (SOC) under all vegetations; PLFA contents of total microbial community and main taxa generally decreased as soil depth increased, while G+/G-and f/b increased with soil depth. Among different vegetations, total PLFA contents and main taxa biomass under mixed broad-leaved forests were the highest; f/b and G+/G-under coniferous forests were higher than those under broad-leaved forests; the availability of SOC under subalpine meadows was constrained on some level by the low pH value, which led to a relatively high f/b and G+/G-. In conclusion, the effect of SOC on soil microbial community composition was the most significant of all soil parameters under all vegetation types, though the availability of SOC could be constrained by relatively low pH values on some level; fungi was more sensitive to the changes of vegetation types while bacteria was more sensitive to the variability of nutrient availability and pH. This conclusion could have a significant impact on forecasting soil microbial community composition under different vegetations.