我国东部天然林土壤磷形态和有效性的纬度分异格局及其形成机理

Human-induced elevation of atmospheric CO2 concentration and increases in nitrogen (N) deposition have led to a strong imbalance with the supplies of other mineral nutrient elements (mainly of phosphorus (P)), conferring an increasing important role of P availability in the function (e.g. carbon (C) storage) of natural forest ecosystems. The increasing imbalance of C and nutrient supplies is likely to significantly affect the uptake and storage capacities of C of natural forest ecosystems. The impact can differ in different regions, which may, at least partly, depend on the status of soil P availability in the specific region. Therefore, it’s important to learn how and why soil P availability under natural forest reveals regional difference in the context of continuous global changes..This project aims to look into the pattern and mechanism of latitude vairations in the form and availability of P in soil under natural forest in east China. This project will be carried out based on a previous project that has built a database of China forests with mineral soils collected. Thirty six natural forests evenly distributed in the altitude in east China were selected from the database by a strafied random sampling method. Parameters including the total amount, forms (using a sequential chemical extraction method and a 31P-NMR analysis), and biological availability (determined by chemical extraction methods and enzyme hydrolysis assays) of P in the soils will be determined; soil chemical properties related to P availability will also be determined or collected from the database; climate and topography conditons, parent materials and vegetation characteristics will be retrieved from the database or literatures..Based on the comprehensively analysis of these data, this project will clarify the pattern and mechanism of latitude variations in the form and availability of P in soil under natural forest in east China, to enhance our knowledge about the spatial vairations in soil P availability under natural forest in east China and its regulation mechanism. Outcome of this project will be helpful to improve our ability of modelling and predicting the uptake and storage capacities of C of forest ecosystems at a regional or global scale in the context of continuous global changes.

大气CO2浓度升高和N沉降增加正使得天然林生态系统的C和N的供应与P的供应逐渐失衡。这种养分供应失衡对天然林生态系统的C吸收和固持能力具有重要影响，而且这种影响因地区而异，很大程度上取决于土壤养分（如P）有效性的地带性差异。因此，研究天然林生态系统土壤养分有效性的地带性差异及其形成机制，对于认知其C吸存能力的地区差异和养分调控机制具有重要意义。本项目拟在前期研究所建立的全国森林调查数据库和土壤样品库的基础上开展工作。按照分层随机抽样方法，选取我国东部纬度带上的36个天然林作为对象，分析土壤P的总量、形态（化学分级提取和31P-NMR分析）和生物有效性（有效P含量和酶添加培养实验），并将其与样地气候、地形、母岩、植被和相关土壤化学性质结合进行系统分析，以阐明我国东部天然林土壤P形态和有效性的纬度分异格局及其形成机理，为全球变化影响下我国及全球森林生态系统的C吸存能力及其变化研究提供科学基础。

大气CO2浓度升高和氮沉降增加使得天然林生态系统的碳氮供应与磷供应逐渐失衡。研究天然林生态系统土壤磷有效性的地带性差异及其形成机制，对于认知其碳吸存能力的养分调控作用具有重要意义。.本项目选择我国东部纬度带（18.4-40.8oN）上的26个天然林作为对象，分析表层土壤磷的含量和形态（化学分级提取和31P-NMR分析），并将其与样地气候和相关土壤化学性质结合进行系统分析，阐明了我国东部天然林土壤磷形态和有效性的纬度分异格局及其形成机理。主要结果如下：.1. 随着纬度的增加，土壤总磷、有效磷和原生矿物磷含量均有增加的趋势；次生矿物磷、有机磷和残余态磷含量先增加后降低，拐点在30oN左右。.2. 随着纬度的增加，土壤有机磷占土壤总磷的比例先增加后降低，拐点在30oN左右；残余态有机磷占总有机磷的比例逐渐增加。.3. 土壤总磷含量是影响土壤有机磷含量及其占土壤总磷比例的最重要因素，支持生态系统磷营养状况的底物调控假说。.4. 土壤pH是影响土壤磷形态变化的最重要因素。随着土壤pH的增加，残余态有机磷占土壤总有机磷的比例显著增加。.5. 气候（气温和降雨）是土壤磷形态和有效性纬度分异格局的主要决定因子，主要通过影响土壤总磷含量影响土壤有机磷和无机磷的含量，通过影响土壤pH影响土壤有机磷和无机磷的形态。研究结果说明当前不断加剧的全球气候变化将显著影响土壤磷循环过程和供给能力。.本项目还探讨了除磷之外其他土壤元素的纬度分异格局及形成机理。结果表明，随纬度增加，可溶性土壤氮、钙、镁和钾含量显著增加，可溶性土壤铝和铁含量显著降低，可溶性土壤有机碳和锰含量无明显变化。.基于本项目和以往文献报道的全球土壤磷组分数据，本项目还检验和改进了土壤磷循环模型。结果表明，在全球尺度上土壤有机磷矿化和原生矿物磷风化是土壤有效磷的主要来源，固相不稳定土壤无机磷在土壤磷循环过程中起着核心作用。.在本项目资助下，已发表研究论文8篇，其中6篇发表在Global Biogeochemical Cycles和Geoderma等SCI期刊上。