组分和生境差异对藏东南原始冷杉林凋落物分解和养分释放特征的影响

Effects of composition and habitat differences on litter decomposition and nutrient release characteristics of Abies georgei var.smithii in southeastern Tibet

以藏东南色季拉山急尖长苞冷杉林凋落物为研究对象,分不同组分(纯叶样、纯枝样和自然样)和不同生境(林内、林外和林缘)进行分解试验,旨在探明组分和生境差异对高寒森林生态系统凋落物分解和养分释放特征的影响。结果表明:凋落物逐月分解速率为纯叶样(2.21%)>自然样(2.17%)>纯枝样(1.70%),林内(2.17%)>林外(1.94%)>林缘(1.93%);同一生境下自然样、纯叶样、纯枝样分解95%所需时间分别为8.96、10.02和13.18年;同一组分不同生境下(林内、林外和林缘)分解95%所需时间分别为8.96、10.01和10.84年;碳(C)和氮(N)过程释放速率均与组分极显著正相关,而磷(P)和钾(K)过程释放速率均与组分极显著负相关;C、N、P和K过程释放速率均与生境显著或极显著正相关;C/N、C/P和N/P在不同生境间均差异极显著;C/N与生境间呈现极显著负相关、C/P与生境无显著相关性、N/P与生境间呈现极显著正相关。不同组分和生境条件对凋落物分解速率和养分释放特征均有显著的影响,且组分和生境影响程度不同。

[Background]Litter decomposition is one of the important links of material cycle and energy flow in forest ecosystem.There are few reports on the litter decomposition and nutrient release of typical natural dark coniferous forests in Tibet.The purpose of this study is to provide basic data and theoretical basis for in-depth understanding of the material cycle process of forest ecosystem in high altitude and cold environment.[Methods]Three types of samples(leaf sample,natural sample,and branch sample)from 3 sample plots(in forest,outside forest and beside forest)were selected in Sejila Mountain,Tibet.The litter of Abies georgei var.smithii forest was collected in December 2016.At the beginning of each month in 2017,3 bags of litters were collected from each sample plot,and the litter retention rate and monthly decomposition rate were calculated.The content of C,N,P,and K was determined by concentrated sulfuric acid-potassium dichromate method,Kjeldahl method,molybdenum blue colorimetric spectrophotometry,flame spectrophotometry.[Results]1)The monthly decomposition rate of litter was leaf sample(2.21%)>natural sample(2.17%)>branch sample(1.70%),and IF(2.17%)>OF(1.94%)>BF(1.93%).2)The decomposition time of 95%of natural sample,leaf sample and branch sample litter in the same habitat with different components was 8.96 years,10.02 years and 13.18 years.3)The decomposition time of 95%of IF,OF,and BF with the same component was 8.96 years,10.01 years and 10.84 years.4)The release rates of C and N were significantly positively correlated with the components,while the release rates of P and K were negatively correlated with the components.5)The release rates of C,N,P and K were significantly or very significantly and positively correlated with the habitat.6)There were significant differences in C/N,C/P and N/P among different habitats.7)There was a very significant negative correlation between C/N and habitat,no significant correlation between C/P and habitat,and an extremely significant positive correlation between N/P and habitat.[Conclusions]Different litter components and habitat conditions have significant effects on litter decomposition rate and nutrient release characteristics,and the effects of components and habitats vary.