宁夏引黄灌区土壤盐碱化对气候变暖响应机制研究

The salinization of soil in arid and semiarid region has been one of the most critical environmental problems nowadays. The area of salinization soil which is affected by global climate change is projected to enlarging. Research on soil salinization its driving mechanism is one of important topics of land degradation and global change for prediction and prevention of salinization of land. However, the effects of climate warming on soil salinization, with respect to water-salt flow or salinization mechanism are not as well documented or understood. We hypothesized that climate warming exerts significant control over soil water-salt flow through soil surface evaporation, plant transpiration, groundwater table, and other soil physical, chemical and biological properties. In this project, we will investigate spatial-temporal variation of soil water-salt flow and its influencing factors through field experiments. Four years of long-term field experiments using the method of field simulation calescence experiment by infrared radiant heater will conduct in Yellow River Irrigation Area of Ningxia china. Our objectives are to 1) address long-term effects of climate warming on soil salinization 2) ascertain the influence and mechanism of climate warming on water- salt flow. This project will provide scientific basis for further clarification of effect of climate warming on occurrence and development of soil salinization in arid and semiarid region, and provide reference basis for the decision-making section to tackle climate change.

干旱半干旱地区的土壤盐碱化已经成为当前最危急的环境问题之一，受全球气候变化的影响进一步加剧的趋势，研究气候变暖背景下的土壤盐碱化发生机制对于土地盐碱化预测与防治具有重要科学意义。本项目紧密围绕“土壤盐碱化如何响应气候变化”这一关键科学问题，以宁夏引黄灌区典型农田土壤为研究对象，采用红外线辐射器野外增温模拟试验的方法，重点开展大气模拟温度增加对不同地下埋深土壤水分含量、盐分含量及水盐运动时空变化规律的影响，分析长期增温试验下不同地下水埋深土壤水盐运移规律与土壤理化性质、地面蒸发、植物生长和蒸腾、地下水埋深和矿化度等因素相互作用，探明气候变暖对土壤水盐影响与驱动机制，为进一步阐明气候变暖对干旱半干区土壤盐碱化发生发展提供科学依据，也为决策部门应对气候变化提供理论参考依据。

土壤水盐运移是土壤盐碱化发生的根本机制，探究干旱半干旱地区气候变暖与地下水埋深、土壤质地、作物种植及人为灌排等因素交互调控的土壤水盐运移是评估气候变化加剧土壤盐碱化的关键。本项目针对气候变暖调控干旱半干旱地区土壤水盐运移的机制问题，采用红外线辐射器增温模拟气候变暖的方法，开展了模拟大气温度增加对不同地下埋深土壤水分含量、盐分含量及水盐运动及作物生长发育的影响研究。在宁夏平罗县宁夏大学盐碱地改良试验站的研究表明：（1）温度增加0.5-2.0℃，0-30cm耕层土壤平均电导率春季提高12.6%-166.8%、夏季提高37.0%-113.2%；秋季提高2.3%-125.0%，冬季提高 77.3%-139.6%，冬春季土壤电导率随温度增加的幅度大于夏秋季；（2）当增温0.5-2.0℃，春、夏、秋、冬四季0-30cm层土壤平均含水率分别降低9.27%-32.65%、8.73%-35.31%、3.04%-26.77%、8.62%-24.44%；（3）K+、Na+、Mg2+、SO42-、Cl-离子向0-30cm土层聚集是土壤盐化加剧重要原因，其机理是增温导致土壤水分蒸发加快，溶解度较大是K+、Na+、Mg2+、SO42-、Cl-离子随水移动到表层土壤的量就越大；（4）温度增加0.5-2.0℃，引黄灌区冬季最大冻土层深度降低12.4%-54.4%，地表干土层厚度增加72.2%-355.6%。（5）随着温度升高，盐碱地种植的春小麦、大豆作物生育期分别缩短5-22天和4-24天。（6）温度升高0.5℃-1.0℃有利于拔节期前春小麦对N、P、K 养分的吸收，但拔节期后增温超过1.0℃ 以上都会对N、P、K 养分吸收产生显著负作用，导致使生育后期干物质的累积量减少，千粒重、穗粒数等降低，并最终导致产量和品质的下降。（7）增温0～2.0℃虽然有利于大豆干物质累积、提高不同器官氮磷钾含量和植株累积量，但是单株结荚数量随着增温梯度的增加而显著降低，最终导致大豆产量、收获系数和氮磷钾利用效率降低。本研究结果为干旱半干旱区土壤盐碱化防治及其应对气候变化提供理论参考依据。