Knowledge Resource Center for Ecological Environment in Arid Area
| 覆膜棉田能量分配解析与蒸散发修订算法 | |
| 其他题名 | Energy partition analyses and modified evapotranspiration algorithms in plastic mulched cotton fields |
| 艾治频 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 杨永辉 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 20世纪60年代以来，地膜覆盖作为主流的农田节水方式，在全球干旱半干旱地区得到了广泛地应用。一方面，地膜覆盖可以提高作物产量、抑制杂草和改善作物品质；另一方面，地膜覆盖极大地改变了地表属性如地表温度、地表水分、地表反射率和表面粗糙度等等。这种由地表属性改变引起的地表能量分配和耗水改变的研究已成为生态水文学的一个重要研究内容。前人的研究多是从水量的角度去揭示地膜覆盖（多指透明膜覆盖）下的实际耗水特征，这对于理解地膜覆盖下的耗水规律提供了很好地参考。本论文旨在从地表能量平衡的角度去量化地膜覆盖对能量平衡各分量和关键参数的影响，建立覆膜条件下蒸散发估算的新方法。本论文紧紧围绕“覆膜条件下能量分配和蒸散发估算”的研究主题，选取西北干旱区阿拉尔绿洲覆膜农田生态系统为研究对象。本论文遵循着“试验”到“模拟”的研究思路。野外试验采用大田和小区相结合的试验方法，大田试验以涡度相关系统为基础，小区试验包括“覆膜不覆膜对比试验”、“不同颜色覆膜对比试验”和“不同覆膜比例对比试验”三部分。在试验观测（能量、水分、作物生长等）和数理分析（能量平衡法、水量平衡法、作物系数法、模型模拟和统计检验等）的基础上，本研究取得的主要结论如下：1、揭示了地膜覆盖对地表能量平衡各分量及能量分配的影响时期和程度。地膜覆盖对能量分配的影响主要发生在叶面积指数小于1的时期。在该时期内，地膜覆盖通过减少净辐射，提高土壤热通量和感热，最终减少潜热。地膜覆盖对净辐射、土壤热通量、感热和潜热的改变分别达-9.4%、33.3%、26.2%和-43.7%。其中，净辐射减少、土壤热通量和感热增加对潜热减少的贡献率分别为40.8%、31.9%和27.3%。地膜覆盖不但改变了能量各分量，而且还改变了地表能量分配的模式。地膜覆盖对地表可获得能量的改变平均达-22%，对土壤热通量占净辐射比例的改变平均达11%；对感热占净辐射比例的改变平均达9%；对潜热占净辐射比例的改变平均达-20%。2、辨析了不同颜色（透明膜、白膜和黑膜）和不同比例覆膜下地表能量分配的差异。黑膜覆盖下净辐射最大，透明膜和白膜覆盖下净辐射分别下降8%和20%。透明膜覆盖下土壤热通量最大，黑膜和白膜覆盖下土壤热通量分别下降14%和22%。黑膜覆盖下感热最大，透明膜和白膜覆盖下感热比较接近。黑膜覆盖下潜热最大，白膜覆盖下最小，这种差异随着叶面积指数增大而减小。覆膜比例变化对土壤热通量和感热的影响要大于净辐射。 3、发展了覆膜条件下地表反射率和土壤热通量估算的新方法。就反射率而言，本研究建立了基于光学传输的适合不同颜色材料的反射率模型，该模型能客观地刻画不同时期反射率的变化特征。就土壤热通量而言，本研究建立了基于净辐射和叶面积指数的估算方法，同时获得了不同颜色覆膜下的经验参数。这些估算方法对于覆膜条件下净辐射和土壤热通量的估算提供了方法参考，尤其是对于无观测资料地区能量平衡的估算和分析。4、弄清了覆膜条件下作物系数的变化特征及驱动因素，建立了覆膜条件下作物系数估算的经验模型。苗期作物系数较小且变化平稳，蕾期后快速增加，在花铃期保持较高水平，最后在吐絮期开始下降。就整个生育期来看，作物系数变化幅度为0.08-1.28，平均值为0.54。由于平流作用的影响，灌溉提高了作物系数，就2013和2014两年平均值而言，增加幅度达29.4%。叶面积指数3和土壤可利用水分0.5可以视为影响棉花作物系数的两个关键阈值。与本研究的结果相比，使用文献记录的作物系数会高估蒸散发比例达24%-64%，这表明不能盲目使用FAO或其他文献中的作物系数，对于特定的耕作管理条件需要进行修订。5、构建了基于Priestley-Taylor模型的覆膜条件下蒸散发估算的新方法。本研究通过蒸散分离，同时考虑覆膜的影响建立了覆膜条件下Priestley-Taylor系数参数化的新方案。结合对反射率和土壤热通量的修订，最终发展了基于Priestley-Taylor模型的覆膜条件下蒸散发估算的新方法。通过验证和应用，发现修订后的模型能很好模拟不同覆膜比例下不同生育期的蒸散量。敏感性分析表明，修订后的Priestley-Taylor系数对叶面积指数的敏感性要大于对空气温度的敏感性。 |
| 英文摘要 | Plastic mulch, as a major water-saving method in croplands, has been widely used in arid and semiarid regions around the world since 1960s. On the one hand, plastic mulch can increase crop yield, suppress weed, and improve crop quality. On the other hand, plastic mulch has substantially modified the surface properties such as surface temperature, surface water, surface reflectance, and roughness length. Studying the modifications in surface energy partition and water consumption induced by these surface properties hsa become an important research content of ecohydrology. Former studies often focused on the characteristics of actual water consumption in terms of water balance, which offered good reference for the understanding of the law of water consumption under plastic mulch (mainly refers to transparent plstic mulch) condition. The objective of this dissertation was to quantify the magnitude of the effects of plastic mulch on each component of energy balance and the key parameters, and to establish new method for the estimation of evapotranspiration under plastic mulch condition.This dissertation closely centered on the theme of energy partition and evapotranspiration estimations under plastic mulch condition, chosen Aler oasis plastic mulched cropland ecosystem that located in northwest China as the study site. The whole research route of this dissertation is from experiment to model. Experiments were conducted in combination with field and plot observations. Field experiments were mainly based on the eddy covariance, and the plot experiment included three parts of “comparison of plastic mulch and non-plastic mulch”, “comparison of different colored plastic mulch”, and “comparison of different mulch fractions”. After combined analyses of field observations (energy components, water components, and crop growth) and mathematical analysis (energy balance, water balance, crop coefficient, model and statistical test), the main conclusions obtained in this dissertation are as follows: 1、Identified the period and magnitude of the effects of plastic mulch on each component of energy balance and energy partition. The effect of plastic mulch on energy partition was mainly at the period when leaf area index (LAI) < 1. During this period, plastic mulch can reduce net radiation (Rn), increase soil heat flux (G) and sensible heat (H), and finally decrease latent heat (λET). Average modifications of Rn, G, H, and λET induced by plastic mulch were -9.4%, 33.3%, 26.2%, and -43.7%, respectively. Where about 40.8% of the reduction in λET was due to a decline in Rn and 31.9% and 27.3% were due to increases in G and H, respectively. Plastic mulch changes not only each component of energy balance, but also the surface energy partition mode. Modifications in surface available energy, surface soil heat flux relative to net radiation, sensible heat relative to net radiation, and latent heat relative to net radiation induced by plastic mulch was averaged -22%, 11%, 9%, and -20% 2、Distinguished the differences in energy partition under different colored (transparent, white, and black) and mulch fraction conditions. Net radiation was the highest under the black plastic mulch, and which decreased by 8% and 20% under transparent and white plastic mulch condition, respectively. Surface soil heat flux was the highest under transparent plastic mulch condition, and which decreased by 14% and 22% under black and white plastic mulch condition, respectively. Sensible heat was the highest under black plastic mulch condition, and which was close between transparent and white plastic mulch condition. Latent heat was the highest under black plastic mulch condition and smallest under white plastic mulch condition. The magnitude of effects of mulch fraction change on soil heat flux and sensible heat were larger than that on net radiation. 3、Developed new methods to estimate surface reflectance and soil heat flux under plastic mulch condition. For surface reflectance, this dissertation developed a new model for surface reflectance based on the transformation of light that can be used for different colored plastic films. The model can curve the variation of surface reflectance at different growing stages. For surface soil heat flux, this dissertation developed a new method incorporating with LAI and net radiation, and also obtained several parameters for different colored plastic films. These developed methods offered a new way to estimate surface reflectance and surface soil heat flux, especially for the analyses of energy balance in regions without observations. 4、Clarified the characteristics and driving factors of crop coefficient and constructed empirical models to estimate crop coefficient (Kc) under plastic mulch condition. Cotton Kc was small and stable at seedling stage, rapidly increased at squaring stage, remained high at flowering and boll-setting stage, and then finally started decreasing at boll opening stage. Daily cotton Kc varied within 0.08?1.28, with an average of 0.54 for the entire cotton growth stage in 2013 and 2014. Due to the effect of advection after irrigation, irrigation significantly increased Kc by an average of 29.4% in 2013 and 2014. The threshold value of 3.0 for LAI and 0.5 for extractable soil water (ESW) were detected. Using documented Kc in the literature could lead to overestimation of evapotranspiration by 24%?64%. This suggested that caution should be exercised in blindly using the FAO or documented Kc values and underscored the necessity of local calibration of Kc for increased accuracy. 5、Established a new method to estimate evapotranspiration under plastic mulch condition on the basis of Priestley–Taylor model. This study developed a new formula for estimating Priestley–Taylor coefficient based on plant physiological limitations and partitioning of evapotranspiration. Combined with the new method developed for estimating surface reflectance and surface soil heat flux, we finally developed a new method to estimate evapotranspiration based on Priestley–Taylor model. The developed model can better estimate the evapotranspiration for different mulch fractions at different growing stages. Sensitivity analysis showed that the modified Priestley–Taylor coefficient was more sensitive to LAI than to air temperature. |
| 中文关键词 | 地膜覆盖 ; 能量平衡 ; 蒸散发 ; Priestley-Taylor模型 ; 棉田 |
| 英文关键词 | Plastic mulch Energy balance Evapotranspiration Priestley-Taylor model Cotton field |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院遗传与发育生物学研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287816 |
| 推荐引用方式 GB/T 7714 | 艾治频. 覆膜棉田能量分配解析与蒸散发修订算法[D]. 中国科学院大学,2016. |
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