绿洲农田生态系统生态化学计量特征及其对养分限制的指示

Ecological stoichiometry, which balances multiple elements and integrates different scales from individuals to ecosystems, has greatly advanced our understanding of ecological. The ecological stoichiometric properties of carbon (C), nitrogen (N) and phosphorus (P) are the important performances of ecosystem process and function, and are powerful indicators of diverse ecological processes. Studies on ecological stoichiometric properties and theirs driving mechanism become one of hot topics of biogeochemical cycle and global change．Taking the farmland ecosystem of Aksu oasis of the upper reaches of Tarim River as test object, this reseach will reveal ecological stoichiometric properties of typical crops (wheat, maize and cotton)and soil. The different organs (leaf, stem, root and fruit) of typical crops and soil samples will be collected at different growth stage, and C, N and P contents and C:N:P stoichiometry will be monitored. Based on the pot and field experiments in with N and P fertilizer additions, the homeostasis of typical crops will be indicated by exponent (reciprocal of the regulation coefficient) of the power function of crop nutrient against soil nutrient concentrations.. We will analyze influence of environment (other soil physical, chemical and biological factors, and groundwater) and human activity (cropping and fertilizing) to the ecological stoichiometric properties. The relationship with growth rate of crops and C, N and P will be discussed with fertilizer additions,and the growth rate hypothesis (GRH) will be tested. We will determine the limited nutrient and its criterion, which will be used to assess the advantages or disadvantages of current fertilizers system, and pursue fertilizer treatments suitable for crops. This study attempts to reveal ecological stoichiometric properties of oasis agroecosystem and theirs driving mechanism in oasis, utilized ecological stoichiometric properties to considering limited nutrient, and can be beneficial for adding research fields of land ecological stoichiometry. Our findings can offer reference for future field studies on ecological stoichiometry in arid land. Scientific basis are provided for deepening reasearch on strategies of nurient utilization of crops, supporting the optimized management of oasis farmland ecosystem, stabilizing and improving of ecological security of agriculture.

碳（C）、氮（N）、磷（P）生态化学计量特征是生态系统过程及其功能的重要体现。以塔里木河上游阿克苏绿洲农田生态系统为对象，系统研究小麦、玉米、棉花等典型作物不同生长期叶、茎、根、果实等器官与土壤C、N、P生态化学计量特征；结合室内和野外施肥控制实验，计算内稳性指数，比较作物内稳性差异；探讨水盐胁迫下环境因子和耕作、施肥等农业活动对生态化学计量特征的影响；分析施肥作用下作物生长速率与C、N、P的关系，验证生长速率假说，确定作物限制元素类型和临界点，评价现有施肥模式，探求适宜区域农田生态系统需求的NP施肥配比。研究旨在全面揭示绿洲农田生态系统生态化学计量特征及驱动因素，实现生态化学计量特征在绿洲农田生态系统限制性养分判断中的应用，进一步拓展陆地生态化学计量学的研究领域，深入作物-土壤系统养分利用策略研究，促进干旱区绿洲农田生态系统的优化管理，维护区域农业生态安全。

开展农田生态化学计量学研究有助于解决作物-土壤系统养分供求平衡中的问题，为准确评估系统生产力及其功能变化提供依据。塔里木河上游阿克苏绿洲属于典型的生态脆弱带，在人类大规模的“富营养化”农业活动下，农田对外源物质利用效率低下，土地生产能力下降，作物及土壤的元素循环发生改变。以阿克苏绿洲农田生态系统为对象，研究了小麦、玉米、棉花等典型作物与土壤生态化学计量特征及作物内稳性；分别从内因（生育期、器官）和外因（土壤环境、耕作年限）讨论了主要作物生态化学计量特征与影响因素的关系；结合野外施肥控制试验，比较棉花内稳性差异，分析施肥作用下棉花生长速率与C、N、P的关系，验证生长速率假说，确定作物限制元素和临界点。结果表明：小麦C、N含量在叶片中最高、P含量在麦穗中最高，玉米C、N和P含量分别在苞叶、叶片和穗中最高，棉花C含量在叶片中最高、N和P含量均在蕾中最高。作物土壤元素含量及计量比均较低于全国水平。三种作物在生长过程中生态化学计量特征受生育期和器官单因素以及两因素交互影响程度各不相同。在作物与土壤生态化学计量特征之间关系上，小麦C和N含量与土壤P含量表现为显著正相关，玉米P含量与土壤P含量存在极显著正相关，棉花N含量与土壤C、N和P含量、P含量与土壤C含量表现出极显著正相关。不同连作年限棉花各元素含量均呈现出先增高后降低的趋势，连作15年时较高、5年时较低。施肥控制试验表明，棉花N、P元素内稳性指数分别在1.02-5.28、1.01-4.55范围内，其生长速率与N:P、C:P间均存在负相关关系，符合生长速率假说，受N和P共同限制。研究全面揭示了绿洲农田生态系统生态化学计量特征及驱动因素，实现了生态化学计量特征在绿洲农田生态系统限制性养分判断中的应用，为深入作物-土壤系统养分利用策略研究、促进干旱区绿洲农田生态系统的优化管理和维护区域农业生态安全提供了重要的科学依据。