高山森林三种细根分解初期微生物生物量动态

为了解川西高山森林凋落物分解过程的微生物生物量特征,采用凋落物分解袋法,测定了粗枝云杉(Picea asperata)、岷江冷杉(Abies faxoniana)和红桦(Betula albosinensi)细根分解几个关键时期微生物生物量碳(MBC)、氮(MBN)和磷(MBP)的动态特征。3个树种细根分解过程中的MBC均表现为在土壤深冻期下降至全年最低点后缓慢上升,至土壤融冻中期再次下降,到生长季节增长的趋势。然而,粗枝云杉与岷江冷杉细根分解过程中的MBC最大值出现在生长季节末期,红桦细根分解过程中的MBC最大值出现在土壤冻结初期。3个树种细根分解过程中的MBN表现出相似的动态规律:土壤深冻期急剧下降至全年最低,随后在冻融季节无显著变化,生长季节明显增加,到生长季节末期达到全年最大值。另外,粗枝云杉和岷江冷杉细根分解过程中MBP均随着分解的进行呈现增加趋势,而红桦细根分解过程中的MBP在土壤融冻末期出现最大值,在生长季节中期出现另一峰值,生长季节末期明显下降。这些结果表明冬季细根分解过程中仍存在一定的土壤微生物,但受到细根质量、温度及其驱动的环境因子的深刻影响。

Dynamics of soil microbial biomass during early fine roots decomposition of three species in alpine region

Microorganism plays an essential role in the decomposition of litter and senesced fine root, as a consequence of which more and more attentions have been paid to the microbial biomass dynamics in litter and soil in the past two decades. Moreover, increasingly studies have also demonstrated that lots of litter mass lost in cold winter in the seasonal freeze-thaw area. However, little information has been available on the dynamics of microbial biomass during litter decomposition in wintertime, far less for fine roots decomposition. In order to character the dynamics of microbial biomass during fine roots decomposition in a alpine forest over the growing season and freeze-thaw season, microbial biomass carbon (MBC), nitrogen (MBN) and phosphorus (MBP) were measured using the litterbag method from November 11, 2009 to November 11, 2010. The fine roots of spruce (Picea asperata), fir (Abies faxoniana) and birch (Betula albosinensi) were selected which are three representative tree species in the alpine and subalpine forest of Western China. Microbial biomass C(MBC) displayed a sharp decline tendency before the soil frozen as soil temperature decreased, and significantly increased utile to soil thawing, but continually declined as temperature increased after the middle stage of soil thawing, and then a increased tendency was observed. However, the changed time of MBC was different in the fine root decomposition of different species. The peak values of MBC during the decomposition of spruce and fir fine roots were observed in the late stage of growing season, but which of birch was detected in the early stage of soil frozen. MBN displayed the similar dynamics pattern during the fine roots decomposition for all three species, which rapidly decreased until soil completely frozen, and showed little changes during the whole freeze-thaw season, but obviously increased to a peak value in the later stage of growing season. In addition, MBP during the decomposition of spruce and fir fine roots were increased as the decomposition proceeded, although which of birch displayed its maximum value in the later stage of soil thawing, another peak value in the middle stage of growing season, and then obviously declined in the later stage of growing season. The results indicated that large quantities microorganisms could be available even in winter, which could do great contributions to the litter decomposition. Nevertheless, the microbial biomass could be significantly affected by fine root quality, temperature and other climate conditions.