湖滨带典型植物群落生态化学计量学对洱海水位-水质的响应

Lakeside zone is the important intermediate place for material exchange between lake and terrestrial ecosystems, and it is also the ultimate barrier to intercept N, P and other pollutants into the Erhai Lake. Stability of plant community in lakeside zone affects its ability to purify N, P and other pollutants, but the nearshore water level - water quality changes in the Erhai Lake influence the stability of plant community in lakeside zone. Ecological stoichiometry is the important method to study the stability of plant community structure and function in lakeside zone, but studies on the response mechanism of ecological stoichiometry characteristics of plant communities to water level - water quality interactions in lakeside zone are few. The project will take the typical plant communities of lakeside zone as the research object by the simulation control tests of water level - water quality and the situ monitoring. Ecological stoichiometry characteristics of typical plant communities in lakeside zone under the water level - water quality interactions of the Erhai Lake will be studied. The restrictive key factors related to water quality and water level affecting ecological stoichiometry of typical plant communities in lakeside zone will be chosen. The response mechanism of ecological stoichiometry characteristics of plant communities to water level - water quality interactions in lakeside zone will be revealed. The results will provide strong technical support for improving water quality, regulating water level, choosing the high homeostasis species and their compositions of the stable community for adapting the different changes of water level – water quality in lakeside zone in the Erhai Lake.

湖滨带是湖泊-陆地生态系统物质交换过程中最重要的中间场所，也是拦截处理入洱海氮磷等污染物的最后屏障。湖滨带植物群落的稳定性影响着其对氮磷等污染物的净化能力，而其稳定性又受洱海近岸水质-水位变化的影响。生态化学计量学为研究湖滨带植物群落结构、功能的稳定性提供了重要方法，但目前湖滨带植物群落生态化学计量学对洱海水位-水质互作用的响应机制研究较少。本项目拟以洱海湖滨带典型植物群落为研究对象，通过原位监测和水位-水质模拟控制试验，研究洱海水质-水位互作用下湖滨带典型植物群落生态化学计量学特征，筛选出与水质、水位相关的影响湖滨带典型植物群落生态化学计量学的限制性关键因子，揭示湖滨带典型植物群落生态化学计量学对洱海水位-水质的响应机制。本研究可为改善洱海水质、调控洱海水位和筛选适应不同水位-水质变化的洱海湖滨带高内稳性物种及其组成的稳定性群落提供强有力的技术支撑。

湖滨带是拦截氮磷等入湖污染物的最后屏障，湖滨带植物群落的稳定性影响着其对氮磷等污染物的净化能力。基于植物生态化学计量学原理，本项目通过对洱海湖滨带植物群落的调研及长期观测，以挺水植物群落（茭草）、浮叶植物群落（菱角）和沉水植物群落（微齿眼子菜）为研究对象，选择海西蔬菜种植区、海北稻蒜轮作区和海东面山区为典型湖滨带区域，研究了洱海湖滨带典型植物群落的生态化学计量特征，筛选出影响植物群落生态化学计量学的限制性关键因子，评价了植物群落生态化学计量的内稳性。结果表明：典型植物群落生态化学计量特征呈现物种、区域和生长季节性差异，挺水植物的C:N和C:P显著高于沉水和浮叶植物。洱海湖滨带沉水、挺水和浮叶植物平均N（25.99 g/kg）、P（3.12 g/kg）含量及N:P（8.9）远高于中国主要湖库和湿地相应植物N（15.74 g/kg）、P（2.13 g/kg）含量和N:P（5.7），且N:P＜10，说明洱海湖滨带植物生长是磷过剩而氮缺乏，处于氮限制的状况，就环境因子与植物群落的C、N、P及其比值的相关分析结果也正说明这一观点。RDA分析表明水中的TN、沉积物中的速效养分（IN和AP）、SOC、TN、TP显著影响着洱海湖滨带不同植物群落的生态化学计量特征。沉水植物和浮叶植物HN指数明显高于HP，而挺水植物正相反。沉水植物的HN高于浮叶和挺水植物，挺水植物的HP高于浮叶和沉水植物，说明挺水植物地上部N含量更易受到沉积物和水中氮浓度的影响，而沉水植物P更易受到环境中磷浓度的影响。本研究结果可为筛选适应洱海湖滨带高内稳性物种及其组成的稳定性群落提供强有力的技术支撑。