旱区覆膜畦灌对土壤作物系统水热运移规律的影响研究

Plastic film mulching directly affects the hydrothermal conditions of soil and crop and the physiological and ecological processes of crop leaves. The previous studies focus on the effects of plastic film mulching on the hydrothermal status of root zone soil and crop canopy, but lack the effects of plastic film mulching on the coupling processes of stomatal conductance and photosynthetic and transpiration, and can not fully and profoundly understand the response process and law of soil and crop system to the changes of water and heat under plastic film mulching condition. This study focuses on the stomatal conductance-photosynthesis-transpiration process of crop leaves, explores the effects of plastic film mulching with different optical characteristics on the water and heat transfer law of root zone soil and field near-surface and crop canopy, answers whether plastic film mulching induces the adaptable regulation of stomatal conductance, and reveals the regulation mechanism of the stomatal conductance and photosynthetic and transpiration coupling process through plastic film mulching. The formula for calculating stomatal conductance and net photosynthetic rate will be established based on the soil-canopy environmental factors under the farmland mulched with plastic film conditions, and the actual evapotranspiration formula will be established to calculate the farmland evapotranspiration under the farmland mulched with the plastic film of different optical characteristics conditions. The expected results of this study will further deepen the research and understanding of the coupling of mulch-covered farmland-scale bio-environmental effects, which will be of important guiding significance for improving the use efficiency of farmland hydrothermal resources.

地膜覆盖直接影响到农田土壤与作物水热条件以及叶片生理生态过程。前期研究多集中于地膜覆盖对根区土壤和作物冠层水热状况的影响，但缺乏对叶片气孔导度与光合−蒸腾耦合过程影响的深入研究，并未能全面深刻地认识土壤-作物系统对覆膜条件下水热改变的整体响应过程与规律。本项目以叶片气孔导度−光合−蒸腾过程为核心，探究不同光学特性地膜覆盖对根区土壤-农田近地表-作物冠层水热运移规律的影响，回答地膜覆盖是否引起叶片气孔导度的适应性调节，揭示覆膜对叶片气孔导度-光合-蒸腾耦合过程的调节机理，建立基于覆膜土壤-作物冠层环境因子的气孔导度与净光合速率计算公式及考虑不同光学特性地膜覆盖的农田蒸散发计算公式。预期结果将进一步深化地膜覆盖农田尺度生物环境效应耦合的研究和认识，对提高农田水热资源利用效率具有重要指导意义。

农田水热环境是影响作物生长发育的关键因子，地膜覆盖对农田水热环境有重要的调控作用。但覆膜对土壤作物系统作物生长及光合过程的内在调节机理尚不明确。本项目通过田间、室内试验和模拟研究，阐明了覆膜和灌溉对土壤作物系统水热的变化规律，揭示不同灌溉与覆膜情况下的土壤蒸发、作物蒸散变化规律，明晰了叶片光合特性及变化规律，建立气孔导度修正模型并进行修正模型的适用性评价。主要成果如下：（1）覆膜处理促进了土壤水分干湿变化，覆膜和灌溉增加了冠层相对湿度，提高了土壤含水率。覆膜显著提高了土壤温度，冠层温度随冠层高度逐渐增加，覆膜显著降低了冠层温度。（2）覆膜和灌溉增加了灌浆后籽粒优势粒、中间粒、弱势粒单粒重和单粒体积。玉米吐丝后籽粒灌浆过程符合logistic方程模型，模拟R2值均高于0.95。覆膜处理显著提高了籽粒灌浆速率和活跃灌浆阶段持续时间。覆膜和灌溉显著促进作物生长提高作物生产力。（3）覆膜条件下亏缺灌溉导致的光合速率降低主要是由于叶片的气孔限制，而不覆膜处理（充分灌溉和亏缺灌溉）导致的光合速率降低主要是由于叶片的非气孔限制。充分灌溉和亏缺灌溉下不覆膜处理叶片光合作用的气孔限制到非气孔限制的转变主要在灌溉14天后。（4）引入水分函数或叶气温差修正函数后，BWB、BBL和USO模型模拟精度均有明显提高，其中水分函数修正的模型模拟精度优于叶气温差修正。引入修正因子后，修正函数的R2和E1分别提高5.8–90.6%和6.5–145.4%，RMSE和RE分别降低3.5–67.9% and 4.8–65.6%。引入修正因子后，气孔导度模拟值均在实测值95%的置信区间范围内。（5）DSSAT和SPACSYS能够较好地模拟地膜覆盖下玉米的产量。SPACSYS和DSSAT在气候变化下物候期提前，生殖生长期缩短。覆膜是干旱农业系统应长期采取的农业措施。

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