磷对中亚热带森林细根分解的影响及作用机制

项目名称： 磷对中亚热带森林细根分解的影响及作用机制

项目编号： No.31270584

项目类型： 面上项目

立项/批准年度： 2013

项目学科： 农业科学

项目作者： 林成芳

作者单位： 福建师范大学

项目金额： 81万元

中文摘要： N有效性调控温带生态系统碳的光合吸收和分解损失。在土壤风化严重、P有效性低的热带亚热带地区，凋落物分解调控机制尚不明确,影响准确预测全球环境变化情景下生态系统碳循环。本项目基于前期研究结果，选取两片树种相似、土壤P有效性有显著差异，由花岗岩和石灰岩发育的天然林为样地；选取米槠(高P)和杉木(低P)细根，并把米槠+杉木细根混合，构成底物N/P比梯度。野外采用网袋法测定分解过程凋落物干重、有机碳组分损失和N、P养分释放速率；比较同种细根在不同林分，不同细根在相同林分的分解速率，验证底物或土壤Ｐ有效性控制细根分解的假说；通过外源P添加和施石灰，验证P有效性提高对低P底物和低P土壤的分解促进作用更强的假说。室内把不同细根进行培养，验证细根混合使N、P养分均衡而促进分解，添加P促进低N/P比细根分解加速的假说。测定分解过程降解纤维素和木质素的微生物和胞外酶活性，揭示P对中亚热带细根分解的调控机制。

中文关键词： 磷有效性；森林；细根；分解；酶活性

英文摘要： Many studies have shown that nitrogen (N) availability directly controls terrestrial C uptake and losses in mid and high-latitude ecosystems. Highly weathered soil is widespread in tropics and other low-latitude ecosystems. However, it is still not clear whether phosphorus (P) is the dominant control of litter decomposition in this low soil P availability area. Based on our previous researches, we choose two natural evergreen broadleaved stands with similar tree species composition and significant different soil P availability, which have developed on granite and limestone, respectively. Fine root litters of Castanopsis carlesii (high P concentration) and Cunninghamia lanceolata (low P concentration) are collected, then the two roots and their mixture form high, middle and low P concentration gradient. Part of collected fine roots are buried in both stands for decomposition in the field by means of litter-bag method. The dry mass loss, nutrient release rates and dynamics of different organic carbon fractions are assayed in the leaf litter decomposition process. By comparing the mass loss rates for the three roots in the same stand and the same roots in the different stand, we test our hypothesis that roots with higher P concentration decompose faster on the same soil and the same roots in the lower P availabilit

英文关键词： phosphorous availability；forest；fine root；decomposition；enzyme activity