中亚热带木本植物各器官凋落物分解特性

Decomposition of above and belowground organ litters of mid-subtropical woody plants

植物因资源条件的差异形成不同的生态对策以获取养分进行代谢,具有不同的植物功能性状,从而可把植物凋落物分解特性与生态对策联系起来。为探究中亚热带地区木本植物凋落物分解特性与生态对策的关系,选取两种生态系统中的植物物种的地上、地下各器官凋落物(包括细根、粗根、细枝和叶片),采用分解袋法在两种土壤基质中(砂岩与石灰岩)进行为期2a(凋落叶片为1a)的分解实验,同时进行交叉实验。分解1a及2a的各器官凋落物间分解常数的关系采取Pearson相关性分析,并用SMA进行线性回归,结果表明植物各器官凋落物间的分解具有正相关关系,且分解1a后的细根与粗根、细根与细枝及分解2a后的细根与粗根呈现出显著正相关;而比较常绿植物及落叶植物凋落物在两种土壤基质和两种物种来源分解1a后的差异,除枝条外落叶植物凋落物的分解常数都大于常绿植物,在0.05置信水平上呈现出显著差异性。植物各器官凋落物间的分解具有一致性,不同生活型植物的各器官间的分解速率在不同物种来源或不同土壤基质中都表现出相似的差异。

Litter and its decomposition are important processes of carbon and nutrient cycles and substantially affect forest regeneration and species diversity of soil microorganisms. Interspecific variation in decomposition of litter derived from various organs, such as foliar litter, roots, and woody debris, has been increasingly researched in the past decade. In addition, plant functional traits are widely utilized to predict such variation in plant litter decomposition. Due to the difference of resource conditions in different ecosystems, plants form different ecological strategies for nutrient acquisition and metabolization and thereby vary in plant functional traits. Previous studies have shown that plant litter decomposability is correlated with ecological strategy in several ecosystems. In the long process of nutrient and carbon exchange and recycling, plants coordinate the traits of the above and belowground organs to adapt to climate and soil conditions of the growth region. However, the consequences of such coordination for correlation between different organs＇ litter decomposability across species is less known. Therefore, our aim is to investigate the relationship between litter decomposability and ecological strategy in subtropical areas. We analyze the litter decomposition constant （K） of above and belowground organs after one year and two years of incubation by using the litter-bag method. We collected litter materials from various plant tissues （foliar litter, twigs, fine roots and coarse roots） from two contrasting sites, one being a limestone area that has low soil nutrient and moisture content, and the other a sandstone area dominated by evergreen board-leaved forest. Each organ types of the same species were collected from more than three of trees. Then we placed these litters, in litterbags, to decompose in two kinds of incubation substrate （limestone and sandstone） in a common site （106~24＇E, 29~ 49＇N） for two years of decay. Litter bags with roots materials were placed at 15 cm depth in the soil, twigs and foliar litter were placed on the surface of the soil. All litter bags in the buried bed were non-overlapping. Mass loss over one and two years of incubation was fitted with the negative exponential function of Olson to calculate litter decomposability （K）. Our results show that litter decomposability is differs significantly between across organs. Decomposability of coarse roots and fine roots is greater than that of foliar litter, and twigs decompose slowest. Litter decomposability of different organs is positively correlated across species, i.e. species with high foliar litter decomposability also show relatively high decomposability of other organs. Moreover, a comparison of decomposability of plants of two life forms that were incubated in two substrates in the two collection areas, shows that litter from deciduous plants decomposes significantly faster （P〈 0.05 ） than that of evergreen plant across all organs （except for fine twigs）. The differences in decomposability of plant organs of deciduous plants and evergreen plants were constant across incubation substrates and sampling areas. Our findings show that the strategy by which plants use resources and the litter decomposability of their different organs are linked through plant functional traits. This improves our understanding of the relationships among plants, soil, and litter.