金沙江干热河谷植物叶片元素含量在地表凋落物周转中的作用

Abstract

叶片的化学计量学特征在植物响应环境变化,决定植物的生后效应中具有重要的偶联作用。为了阐明植物叶片生源要素含量对凋落物周转的影响,分析了金沙江干热河谷萨瓦纳草地生态系统植物叶片的化学计量学特征与凋落物周转时间的关系。结果显示:凋落物周转受到多重生源要素及其交互作用的影响,其中K与凋落物周转时间存在显著的正相关关系,而S、Mn、Mg元素具有负关系,表明K可能抑制凋落物的分解,而S、Mn、Mg元素可能会促进凋落物分解。在物种水平上K、S、Mn分别与凋落物周转时间存在显著的相关性, K、S组合解释了16.93%的凋落物周转时间变异;样方水平上,K、S、Mn、Mg分别与凋落物周转时间具有显著相关性,虽然N对凋落物的周转时间影响不显著,但当N与K及其交互作用对凋落物周转时间解释了37.42%的变异。其它元素组合也可在不同程度上解释了凋落物周转时间的变异。多元要素的互作效应表明元素间可能存在拮抗和协同效应,凋落物分解过程中可能受到多重分解者的共同作用,而不同分解者会受到不同的元素限制。未来的研究应当注重N、P以外的元素在生物地球化学循环中的作用。;Leaf elemental stoichiometry has an important role in linking plant response to environmental changes and its afterlife effect. Plant leaf stoichiometry can change dramatically across environment gradients such as grazing, moisture and soil fertilities and consequently affect ecosystem function (e.g. nutrient cycle) in turn. Although concentrations of elements in leaves have already be known to have their effects on litter decomposability, the effects of multiple elements were less studied, especially other elements besides C, N, P. Since there are coordinated decomposition rates of different organs, it can be hypothesized that leaf stoichiometry could capture the variation of litter turnover time and therefore feedback to ecosystem function. To explore the effects of biogenic element concentration in leaves on litter turnover, biomass and litter aboveground were collected from 38 plots in a savanna grassland (E101 °35 '-102 °06 ', N25 °23 '-26 °06 ') which situated at the arid-hot valley of Jinsha river. Biomass and litter were classified into species before weighting. Litter turnover time was calculated as the fresh biomass : litter pool ratio. The most important biogenic element (i.e. N, P, K, Ca, Mg, S, Mn, Cu, Fe and Zn) concentrations in leaves were measured. The relationships between these element concentrations in leaves and litter turnover time were analyzed. The results showed that litter turnover may be affected by multiple elemental concentrations in leaves. K has a significantly positive relationship with litter turnover time while S, Mn and Mg were negatively related to litter turnover time which indicated K might inhibit litter decomposition while S, Mn and Mg might promote it. Contrary to previous studies, neither N nor P was significantly related to litter turnover time. K, S and Mn were related to litter turnover time significantly at species level respectively. K and S jointly explained 16.93% variation at species level. K, S, Mg and Mn were related to litter turnover time significantly at plot level respectively. Although N had no significant effect on litter turnover time alone, K-N and their interaction explained 37.42% variation at plot level. This combination explained 18.37% more variation than K-N additive effect. It was followed by K-Mn combination which explained 36.64% variation at plot level. Other elemental combinations could also significantly explained variation of litter turnover time to some extent. K was positively related to litter turnover time although it was positively related to Mn and Mg which were in turn negatively related to litter turnover time. The results here suggest that K might be the only element that inhibits litter decomposability in this dry and hot area. The mismatch of elemental effects on litter turnover time between at species level and at plot level might result from element transfer in litters or their complementary effects in decomposer's growth. The interactions of multiple elements indicated that there might be synergic and antagonistic effects between elements and suggested that litter turnover time would be affected by multiple decomposers which may be limited by different elements. The results here suggest that future studies should make attentions on other elements besides N and P to explore their roles in biogeochemistry processes.