宁夏罗山4种典型森林群落植物-凋落物-土壤生态化学计量特征

Ecological stoichiometry differences in plant-litter-soil across four typical forests of the Luoshan Mountains in Ningxia

【目的】宁夏罗山是中部干旱带上唯一的生态安全屏障,研究该地区森林群落生态化学计量特征以揭示森林生态系统植被生长发育的主要限制性营养元素,为该地区植被恢复实践中群落的选择和森林经营管理提供理论依据。【方法】选择罗山保护区4种主要的森林群落[青海云杉(Picea crassifolia)纯林、油松(Pinus tabuliformis)纯林、山杨(Populus davidiana)纯林、青海云杉×油松混交林]为研究对象,采取野外样地调查取样,室内测定森林群落乔木优势种植物各器官、凋落物及林地土壤的碳(C)、氮(N)、磷(P)含量,分析比较4种森林群落乔木优势种植物各器官、凋落物、土壤生态化学计量特征及环境因素,植物(各器官平均值)、凋落物和土壤三者化学计量特征的相关性。【结果】(1)乔木优势种植物叶和枝的C含量显著高于根的,叶的N、P含量显著高于枝和根,叶C/N显著低于枝和根;山杨纯林叶和枝的N含量显著高于其他森林群落,而叶的C/N显著低于其他森林群落;油松纯林根的N含量和枝、根的N/P显著低于其他森林群落,而枝和根的C/N显著高于其他森林群落。(2)山杨纯林凋落物N、P含量和N/P显著高于其他森林群落,C/N、C/P显著低于其他森林群落。(3)土壤C、N、P含量,C/N、C/P在不同森林群落间无显著差异,青海云杉纯林土壤N/P显著高于其他森林群落。(4)植物N与凋落物N含量,N/P存在显著正相关关系,两者的C/N则存在显著负相关关系;植物C/N与凋落物C含量存在显著正相关关系,两者的N/P则存在显著负相关关系;土壤C/N、N/P分别与植物P含量、凋落物C/P存在显著正相关关系,凋落物与植物的C/P存在显著负相关关系。植物P含量与土壤pH显著正相关。海拔与凋落物C/N、C/P呈显著正相关,与凋落物N含量、N/P呈显著负相关。土壤N/P与pH显著负相关,与海拔和土壤碱解氮呈显著正相关。土壤C、N、P含量、C/P、N/P与土壤有机质含量呈极显著正相关。【结论】罗山4种主要的森林群落中植物生长发育和凋落物分解的主要限制元素均为N元素,尤其该地区针叶林植被建设中需加强N元素的保护与利用;而山杨纯林生长速率最快且凋落物更易分解,在罗山的植被恢复中应优先选择和保护。

【Objective】The Luoshan Mountains in the Ningxia Hui Auto nomons Region are unique ecological security barriers in the arid zone of central China.Therefore,the stoichiometric characteristics of this areas forest ecosystems were studied to describe the limiting nutrients during vegetation development,to provide a theoretical basis for community selection and forest management in this area.【Method】Spruce(Picea crassifolia)forests,Chinese pine(Pinus tabuliformis)forests,aspen(Populus davidiana)forests,and Picea crassifolia×Pinus tabuliformis mixed forests were examined for carbon(C),nitrogen(N)and phosphorus(P)contents of plant,litter,and soil,and plant-litter-soil ecological stoichiometry correlations were analyzed.【Result】(1)C content of leaves and branches were significantly higher compared with roots,the N and P contents of leaves were significantly higher compared with branches and roots,and leaf C/N was significantly lower compared with branches and roots.Furthermore,leaf and branch N content in Populus davidiana forests were significantly higher,and root N content in Pinus tabuliformis forests were significantly lower,compared with other forests.(2)Litter N,P content,and N/P in Populus davidiana forests were significantly higher,and C/N and C/P were significantly lower,compared with other forests.(3)Soil C,N,P content,C/N,and C/P did not differ significantly among forests,while soil N/P in Picea crassifolia forests was significantly higher than in other forests.(4)Plant N content was significantly positively correlated with litter N content and N/P,and significantly negatively correlated with litter C/N.Plant C/N was significantly positively correlated with litter C content,and strongly negatively correlated with litter N/P.Soil C/N and N/P were significantly positively correlated with plant P content and litter C/P,and significantly negatively correlated with plant C/P.The plant P content was significantly positively correlated with soil pH.Altitude was significantly positively correlated with litter C/N and C/P,and significantly negatively correlated with N content and N/P.Soil N/P was significantly negatively correlated with pH,and significantly positively correlated with altitude and N content.Soil C,N,P content,C/N,and C/P were significantly positively correlated with organic C content.【Conclusion】The plant growth and litter decomposition were both limited by N in the four main forest communities of the Luo Mountains,especially within the coniferous forests.Hence,the protection and use of N elements should be strengthened in these areas.The growth rate is the fastest and litter decomposes more easily in Populus davidiana forests,which are thus candidates for protection and vegetation restoration across the Luoshan Mountains.