新疆绿洲区滴灌制度下农田防护林体系水分利用及遥感模型研究

The 150th regimental farms in XinJiang 8th farming division is known as "sand sea peninsula", it is a typical desert oasis in XinJiang. Its farmland shelterbelts have been playing an important role in ecological protection and agriculture development. However, with the transformation of agricultural irrigation methods, combined with the forest tree species, lead to the interspecific water utilization strategy changed, which will influence the cotton environment and the growth of cotton. Therefore, this project select evapotranspiration (ET) and water use efficiency (WUE) as the test indicators, using fixed point observation and remote sensing model method, synchronous measuring ET and WUE in farmland shelterbelts and cotton field; and then evaluating the interspecific water use relationships and their impacts on cotton productivity quantitatively; In order to further improve the accuracy of the remote sensing simulation on ET and WUE, this project attempting to analyze the error source of the existed remote sensing model and then develop a new assimilation model to calibrate and test and enhance the existed remote sensing model, and minimizing the error of ET and WUE; Finally determine the soil moisture threshold of WUE in cotton become lower, and make full use of drip irrigation to control water in high precision, artificial control water supply of farmland shelterbelts. This project can provide theory basis for formulate technical measures to reduce the influence of struggles over water between farmland shelterbelts and farmland under the current irrigation system in XinJiang; and also the important research to realize water-saving, high-efficient and high-yield in the drip irrigation agricultural in arid oasis region.

素有“沙海半岛”之称的新疆农八师150团是典型的荒漠绿洲，其农田防护林在生态保护和农业发展中有重要作用。然而随着灌溉方式的转变，加之农防林树种配置的影响，导致当前该区农防林体系种间水分利用策略发生改变，影响棉田环境和棉花生长。为此，本项目以蒸散耗水ET、水分利用效率WUE为指标，采用定点观测+遥感模型模拟法，同步测算生育期内林棉种间ET及WUE动态，定量评价当前农防林体系种间水分利用关系及对棉田生产力GPP的影响；为提高ET、WUE遥感模拟精度，采用误差源分析对已有模型检验校正，构建WUE遥感同化模型，将模拟误差最小化；最后根据林棉WUE比值确定棉田WUE降低的土壤水分阈值，可为充分利用滴灌可高精度控水特点，人为控制农防林水分供应提供参考；也可为当前新疆滴灌方式下制定减少“农防林争水”影响的技术措施及农防林节水植被配置调整提供理论依据，是实现新疆绿洲滴灌农业节水高产高效的重要研究内容。

农田防护林在荒漠绿洲区已成为农业生产的绿色生态屏障，但有研究认为防护林会影响农林水分循环，尤其干旱缺水区防护林可能会与农田产生“争水”矛盾”。本研究采用农林同步观测法，结合卫星遥感模型对农田防护林体系林、棉种间耗水量ET及水分利用效率进行了对比分析，结果表明：（1）荒漠绿洲区农田防护林与棉田存在“争水”矛盾，尤其林缘附近棉田受林带“争水胁地”影响更严重；0.1H（H为防护林平均树高）处棉田土壤含水量最低，1H后土壤含水量明显上升，至2H、3H处基本脱离防护林“争水”负效应；（2）农田防护林总耗水量ET明显大于棉田ET。其中农田防护林ET在6月达最大，8月开始逐渐下降；棉花日均耗水量ET从5月棉花生长初期开始逐渐增大，生长后期9月日均耗水量减小；距离防护林越远，棉田ET越大，2H、3H处ET最大；WUE表现为棉田小于林木，0.1H处棉田WUE最小，1H处最大。但关于不同距离处棉田WUE研究仅处于初步探索阶段，后期应进一步完善试验设计，减小误差，同时结合模型对此研究结果进行验证，这也是将来研究重点；（3）基于遥感模型估算的NPPRS、ETRS与实测NPPME、ETME在时间序列上总体趋势基本一致，但在绝对量上遥感模型估算值与实测值误差较大，误差源主要源自卫星遥感地表反照率产品FPAR和NDVI及土壤温度ST，土壤水分SWC等地表实测参数。根据误差源构建的卫星遥感同化模型得出的NPPCom更接近实测NPPME；（4）研究还发现荒漠区农田防护林对其附近的棉田具有一定的脱盐效果，距离防护林越近，脱盐效果越明显，＜0.5H处0~20cm土层脱盐率达3.21%，说明农田防护林对棉田土壤表层及耕层全盐量降低效果明显，可防止次生盐渍化。本项目明确了当前荒漠绿洲区农田防护林与棉田长期共存形成的种间水分关系，实现了对已有WUE卫星遥感估算模型的校正，提高了原遥感模型估算精度。本研究得出的结论可为更好的调节新疆绿洲区农林水分供应，实现旱区农业高效节水提供重要科学依据。