【作者】 蒋太明；

【导师】 魏朝富； 谢德体；

【作者基本信息】 西南大学 ， 农业资源利用， 2007， 博士

【摘要】 如何提高降雨的资源化水平，用好有限的水资源，降低农业生产的需水量和耗水量已成为一个国际性的课题。土壤水分是作物生长、植被恢复以及生态环境建设的主要限制性因素。近年来，随着各种新方法、新技术的应用，农业生态系统水分运移模型，农田水分优化管理与调控技术等方面取得了大量的研究成果。但是，这些研究成果主要集中在半干旱、半湿润气候带的华北平原和黄土高原，而在南方季节性干旱地区，尤其是西南喀斯特地区此类的系统研究工作较少。地处西南地区的贵州，碳酸盐类岩石分布面积大、范围广，是我国水土流失最严重的地区之一，季节性干旱问题突出，严重制约了农业生产的可持续发展。黄壤是贵州主要的农业土壤类型，占贵州国土面积的41.9％，占全国黄壤面积的25.3％，在全国具有典型代表性。为此，本研究选择具有喀斯特山区典型代表性的修文县久长镇为试验区，以黄壤为供试土壤，开展喀斯特山区坡地水分动态及其影响因素的研究，为贵州山区开展集雨抗旱技术示范与推广提供了科学依据。试验研究以为贵州喀斯特山区季节性干旱问题的解决提供科学依据为出发点，围绕坡地黄壤水分时空变异规律，在6.5度、9.5度和16度坡耕地上，按10.0m×4.0m的规格设置试验小区，以裸地为对照，设置了玉米—小麦套作、蔬菜—蔬菜连作两种作物种植方式，于2001年6月～2003年7月期间，采集坡地径流数据66次、共594个，每10天采取0～10cm、10～20cm、20～40cm、40～60cm土层土样，每20天采取60～80cm、80～100cm土层土壤样品进行含水量测定，获得76批次、共3420个土壤水分数据。按照不同坡度、不同作物种植方式分别对径流与土壤水分数据进行分类整理，采用常规数据统计和互谱相关分析、小波分析等方法对黄壤水分的空间变异进行了探讨，完成了贵州喀斯特山区黄壤的持水性能、降水转化、水分动态及其影响因素等相关内容的探讨。主要研究成果如下：（1）黄壤质地粘重，持水力强，比水容量小，有效水范围极窄，易于发生干旱。黄壤剖面中粒径＜0.01mm的物理性粘粒含量691.7～880.5g·kg^-1，粒径＜0.001mm的细粘粒占物理性粘粒的44％以上，为重粘土。黄壤20～40cm土层的粘粒含量最高，不利于降雨入渗。黄壤粘粒含量与田间持水量、凋萎系数和有效水分含量显著正相关；砂粒、粉粒、容重与田间持水量、凋萎系数和有效水分含量呈显著负相关。当土水势由-2.5～-10kPa段降至-10～-30kPa段，再降至-100～-300kPa段时，黄壤比水容量由10^-1数量级降至10^-2数量级，再降至10^-3数量级。当土壤水吸力S小于100kPa时，土壤含水率下降很快，土壤水分释放快，量大；当吸力S大于100kPa时，土壤水分释放缓慢，量小。黄壤0～20cm土层田间持水量高至282.2g·kg^-1，凋萎系数也高达250.0g·kg^-1以上，有效水范围仅30～50g·kg^-1，是黄壤易于干旱的主要原因。0～100cm土体黄壤总库容为5515.3 m³·hm^-2；贮水库容达4094.1 m³·hm^-2，占总库容的74.23％；通透库容仅1421.26 m³·hm^-2，占总库容的25.77％，不利于土壤水分的上、下运行；有效水库容只287.1m³·hm^-2，占贮水库容的比例仅9.69％，易于发生干旱；无效水库容占贮水库容的比例高达90.31％，对作物供水价值不大。（2）常规种植方式下黄壤地表径流量大，降雨资源化效率低。贵州喀斯特山区黄壤径流与降雨在时间上同步，5～8月径流高峰期，频率高，变幅大；3～4月和9～11月平缓，频率低，变幅小。对降雨的接纳始于3月，3～4月中旬的降雨接纳较少；4月下旬～6月降雨接纳频率高，数量大；7月降雨接纳频率低，单次接纳量较大；8月降雨较多，接纳量不大；9月降雨接纳偏少；10月降雨接纳频率高，接纳量小；11月～次年2月，基本没有降雨接纳。4～10月是坡地黄壤增加深层土壤降雨入渗和提高降雨资源化水平的关键时期。黄壤坡地径流（R_s）和“土壤—植物”系统对降雨（P）的接纳（P_e）表现为P=P_e+R_s的数量关系，径流量随降雨量的增大而加速增加，表现为R_s=-a+bP-cP²+dP³的函数关系；降雨接纳量在初期随降雨增大而升高，当降雨到达一定量时，降雨接纳数量逐步降低，表现为P_e=a+bP+cP²-dP³的函数关系。6.5度、9.5度和16度黄壤坡地年产流降雨占年降雨量的72％。裸地的年径流量占年产流降雨量的42.4％，“土壤—植物”系统对产流降雨的58.6％；常规种植方式下的径流系数为31.8％，降雨接纳系数为68.2％，作物种植一定程度上提高了“土壤—植物”系统对降雨的接纳比例。（3）黄壤水分的季节分配及在剖面上的分布差异大。黄壤水分随时间变化而呈有节律的周期性摇荡，周期30～60d。黄壤水分的季节性分配不协调，春季为土壤水分强烈上升蒸发期，土壤水分分布层下移现象明显，水分贮量处于负相位，不利于浅根系作物的水分供应；夏、秋季为土壤水分恢复补充期，降水补充较多，土壤水分分布层明显上移，水分贮量处于正相位；冬季为土壤水分缓慢蒸发补充期，土壤水分蒸发散失较缓慢，土壤水分分布层仍有下移的现象，水分贮量在正、负相位间交替变化。由于黄壤有效水范围极窄，在夏、秋季也常常受到干旱的影响。黄壤剖面相邻层次间具有相似的变点分布及周期性特点，层次间水分的上、下运行因果关系明晰。20cm深度是黄壤水分垂直变异的“拐点”，黄壤含水量在20～40cm土层急剧增高，40～100cm土层水分贮量处于一个较高且稳定的状态。黄壤水分变异系数cv随土层（h）加深而减小，表现为cv=0.5197h^0.4894的函数关系。因此，根据水分变异系数cv可将黄壤剖面划分为：0～20cm为水分活跃层（cv＞0.0876）、20～60cm土层为水分次活跃层（0.0876≥cv≥0.0665）、60～100cm土层为水分相对稳定层（cv＜0.0665）。其中：活跃层是土壤与大气进行水分转化的通道与界面，次活跃层是相对稳定层和活跃层之间的水分传输通道，相对稳定层是土、气界面水分转化的库，三个层次间的水分差异较大，具有较强的水势梯度。黄壤水分活跃层含水率250～400g·kg^-1，次活跃层含水率400～500g·kg^-1，相对稳定层的含水率在500g·kg^-1以上，维持较稳定的土壤水分正梯度剖面构型，水分活跃层水分含量相对较低。（4）坡度和作物种植是黄壤坡地降雨转化及水分保蓄的重要影响因素。在贵州喀斯特山区，随坡度增大，黄壤地表径流量增加，产流降雨量的资源化水平降低。坡度是黄壤水分剖面垂直变异的主要因素，除水分活跃层外，20～100cm土层内的各土层水分含量表现出9.5度＞16度＞6.5度的趋势。菜—菜和裸地方式下水分活跃层的水分含量表现出9.5度＞6.5度＞16度的趋势，6.5度与16度间的水分差异达到了0.01的极显著水平，在玉—麦种植方式下这种差异又消失了。6.5度坡地黄壤粘粒含量过高，严重地制约了6.5度坡地上黄壤的降水入渗。排除土壤粘粒过高所带来黄壤水分异常的6.5度坡耕地后，9.5度坡地黄壤较一致地保持着高于16度坡耕地的水分含量。黄壤水分的时间动态变异主要受制于降水，0～40cm土层尤为明显。玉—麦、菜—菜种植方式对降雨的转化效率随季节更替而相互交替变化。与裸地相比，作物种植增加了坡地黄壤的降雨转化效率。不同作物种植方式下，黄壤水分时间动态与降水保持着较一致的规律性，0～100cm土体，特别是0～20cm土层，其水分与降水在时间上的演变节点基本保持在相同或相近的位置。作物种植在增加降雨入渗的同时，也加大了对土壤水分的蒸腾损耗，一定程度上增加了黄壤水分的变异程度与频率，这种影响随土壤深度的增加而衰减，使相对稳定层的水分含量能够维持在较高含量水平。在高含水量时，玉—麦方式对活跃层黄壤水分变异的效应大于菜—菜方式；裸地方式的水分消耗低，土壤水分含量高。总之，贵州山区坡地黄壤质地极粘重，持水能力强，比水容量小，有效水范围极窄，水分上、下运行困难，耕层水分含量有限，是黄壤易于发生季节性干旱的根本原因。黄壤坡地常规农耕系统的径流系数高，降雨接纳与转化量低，春季是水分贮量的低值时段，黄壤水库的周年均衡供水能力差。坡度对径流具有正效应，对降雨资源化和土壤水分含量都具有负效应；降雨时作物种植增加了降雨接纳量，其余时间则加大了对土壤水分的消耗，一定程度上作物种植加剧了土壤水分的数量变异。因此，在贵州山区坡地黄壤上实施集雨工程建设，大力推行工程、农艺、生物、化控等措施相结合的集雨增效旱作农业技术，提高降雨转化效率，增强土壤水库在农田水分调蓄上的作用是十分必要的。更多还原

【Abstract】 It has become an international topic how to improve the utilization of rainfall and limited water resources, to reduce the water requirement and consumption by agriculture. Soil moisture is a vital factor for crop growth, vegetation recovery and ecological construction. Recently, with the application of new technologies and methods, researchers in China have made great achievements in the fields of modeling water transport in agro-ecosystem, optimizing and regulating field water in agriculture and so on. However, most of the research was carried out in north China plain and the loess plateau, the semiarid zone of China. They are seldom applied in the areas of southern China with seasonal drought, especially in the karst region of southwestern China. Located in the southwest, Guizhou karst mountain area is one of the areas with most serious soil erosion and water shortage, In this region, seasonal drought is frequent, and seriously limits the sustainable development of agriculture. Yellow soil （Xanthozem）, which accounts for 41.9% of the total land area of Guizhou and 25.3% of the total yellow soil of China, is a major soil type for agriculture in Guizhou. In this research, a typical karst mountain area of Jiuchang Town, XiuWen County is selected as an experimental area, where the yellow soil is used to analyze the soil moisture dynamics and their environmental factors. The research provides a scientific basis for demonstrating and spreading of anti-drought technologies.The study focused on providing scientific basis for solving the seasonal drought problem in karst area of Guizhou. According to the spatio-temporal variation of soil moisture in yellow soil, three patterns of land utilization were considered involving corn-wheat intercropping pattern, vegetable-vegetable successive cropping pattern and bared land （check） on three slopes of 6.5°, 9.5°and 16°in the investigation. The experimental plot is 10.0m in length and 4.0 m in width. 594 data for runoff in 66 times and 3420 data for soil moisture in 76 times were collected from June, 2001 to July, 2003. The soil moisture in layers of 0-10cm, 10-20cm, 20-40cm, 40-60cm was measured at an interval of 10 days, and those from layers of 60-80cm, 80-100cm with an interval of 20 days, respectively. All the data were categorized by cropping patterns and gradients and analyzed by methods of the traditional statistics, cross-spectral analysis and wavelet analysis to investigate the spatio-temporal variation of yellow soil moisture. The water holding capacity of yellow soil, precipitation transport on sloping land, soil moisture dynamics and its affecting factors had been discussed in this paper. The main achievements of this study are as follows:1. Yellow soil is easily attacked by seasonal drought due to its heavy texture, high water holding capacity, low specific water capacity, and narrow range of the available soil moisture.In yellow soil, the physical clay particle （<0.01mm） totals up to 691.7-880.5g·kg^-1, of which the extremely clayey particle （<0.001mm） accounts for more than 44%. The clay content is the highest in the layer of 20-40 cm of yellow soil profile, which goes against infiltration. The water-holding capacity of yellow soil is related to contents of clay fractions with the size <0.001mm and <0.01mm in yellow soil profile. There is a significant positive correlation between clay content and field capacity, wilting coefficient and available soil moisture, a negative correlation between sand content, silt content, bulk density and field capacity, wilting coefficient, the content of available soil moisture.The specific water capacity decreases to the scale of 10～（-2） from 10～（-1）, and to scale of 10～（-3） from 10～（-2） when the water potential decreases from -2.5～-10kPa to -10～-30kPa, and then to -100～-300kPa. The yellow soil water content decreases very quickly and the soil water discharges rapidly with a large amount when the suction is less than 100kPa. As the suction exceeds 100kPa, soil water releases slowly with a less amount. In 0-20cm layer of yellow soil the field water holding capacity is as high as 282.2g·kg^-1, with a wilting coefficient more than 250.0 g·kg^-1 and the range of the available soil moisture is only 3-5 g·kg^-1. This is the reason that yellow soil is frequently influenced by seasonal droughts.The total soil reservoir capacities in 0-100cm layer of yellow soil is 5515.3 m³·hm^-2, in which 4094.1 m3·hm^-2 is the water-storage capacity and 1421.26 m³·hm^-2 is the transmission volumetric capacity, making up 74.23% and 25.77% of the total volumetric capacities, respectively. The available water capacity is only 287.1m³·hm^-2, accounting for 9.69% of the water-storage volumetric capacity and therefore it is the reason that yellow soil is easily attacked by seasonal drought. The unavailable water volumetric capacity of yellow soil takes up 90.31% of the water-storage volumetric capacity, which is useless for crops.2. High surface runoff leads to low utilization of rainfall on yellow soil slopes under traditional cropping patterns in karst mountain areas of Guizhou.The surface runoff on yellow soil slopes coincides with the rainfall reception of soil-plant system. Surface runoff appears frequently and changes dramatically from May to August of the runoff peak time; then gently from March to April and also from September to November. The rainfall reception of soil-plant system on yellow soil slopes begins from March, having a low volume from the middle 10 days of March to the middle 10 days of April, and then a great amount of rainfall reception from the last ten days of April to June. The frequency of rain reception is low in July and amount of reception is considerable. It rains frequently in August, and the rainfall reception is limited. It rains infrequently in September. It rains frequently and the rainfall reception is a bit less in October. It seldom rains from November to February of the coming year and there is hardly any rain to infiltrate. It is the key period from April to October to increase deep soil infiltration and improve the rainfall utilization.The relationship of surface runoff （R_s）, the rainfall （P） and the rainfall reception （P_e） on yellow soil slopes could be determined as P = P_e + R_s in quantity. The surface runoff increases rapidly with an acceleration as the rainfall increases. Therefore, the formula for surface runoff with rainfall could be simulated as R_s=-a+bP-cP²+dP³. The rainfall reception increases with the increasing rainfall at the very beginning, later it increases with declining speed, and then decline as the rainfall reaches 70-80 mm. Thus, the equation for the rainfall reception with rainfall could be simulated as P_e=a+a.+bP+cP²-dP³. The rainfall, which causes surface runoff, takes up as high as 72% of the annual precipitation. The runoff from bare land, accounts for 42.4% of the annual rainfall, while the other 58.6% is taken up by soil-plant system. The surface runoff accounts for 31.8% of the rainfall and this leads to a rainfall reception coefficient of no more than 68.2% on yellow soil slopes under traditional cropping patterns. Although the runoff on yellow soil slopes under traditional cropping patterns is smaller than that on the bared land, the runoff coefficient is still high and the utilization of rainfall on yellow soil slopes under traditional cropping patterns needs to be improved, In addition, there is a positive correlation between gradient and runoff and negative correlation between gradient and rainfall reception.3. There is large difference of yellow soil moisture within seasonal distribution and vertical profile.The variation of yellow soil moisture with time tends to be an oscillation of wave with a rhythm of 30-60 days. The water content of yellow soil varies from season to season. Spring is the season with high evaporation leading to soil moisture moving downward clearly, and the soil moisture is at the negative phase, which is disadvantageous to shallow root crops. Summer and Autumn are the accumulation stage of soil moisture from infiltration of rainfall and the soil water moving downward, at this stage the soil water content is at positive phase. Winter is the low evaporation and accumulation stage of soil moisture and the soil water content alternates between positive and negative phases. Due to its narrow available soil water, yellow soil is likely disturbed by seasonal drought in spite of a much high value of soil moisture in summer and autumn, however.There is a similar distribution of inflexion and periodical characteristics between the adjacent layers in yellow soil profile. The causality between layers is obvious. The Variance coefficient （cv） of soil moisture, which is related to depth （h） of yellow soil, could be simulated as cv=0.5197h^-0.4894. The 0-20cm depth is the water active layer with a water content of 250-400 g·kg^-1, which is the channel and interface for water transmission between soil and atmosphere. The 20-60cm depth is the water sub-active layer with a water content of 400-500 g·kg^-1, a transition zone between water active layer and the relatively steady layer and also a channel for water transportation. The 60-100cm depth is the relatively steady layer with a water content of more than 550 g·kg^-1, where the soil water is relatively stabilized, which is the water storage bank for water transformation between soil and atmosphere.4. Slope and cropping are important factors in utilization of rainfall and maintenance of yellow soil moisture.In karst mountainous areas of Guizhou, the surface runoff on yellow soil slopes increases with the increasing gradient, which reduces the utilization of rainfall by soil-plant system. The gradient is also a key factor to vertical variation water content in the profile of yellow soil on the sloping land. Except of the water active layer from 0 to 20cm in profile of yellow soil, water content of the layers within 20-100cm shows the same trend: 9.5°> 16°> 6.5°. Since the physical clay content of yellow soil on 6.5°slope is 100g·kg^-1, much higher than that on 9.5°and 16°slopes, the infiltration and transformation of rainfall by soil-plant system on the 6.5°slope is seriously limited. It is the main reason that the soil water content on 6.5°is less than that on 16°.To the exclusion of the abnormality that occurs on the 6.5°slope, the yellow soil on the 9.5°slope always has a priority in soil moisture maintenance compared with the yellow soil on 16°slope. The variation of yellow soil moisture is up to the rain event in temporal dimension, especially 0-40cm layer.With the seasonal changes, the efficiency for rainfall utilization by soil-plant system alters between corn-wheat and vegetable-vegetable cropping patterns. The crop plantation enhanced the rainfall utilization in comparison with the bare land pattern. The inflexions of yellow soil water variations from 0 to 100 cm depths, especially within the layer of 0-20cm, are nearly in the same location or close to in the temporal dimension. The evapo-transpiration of soil-plant system is enhanced while the infiltration is improved by crops growing. Thus, the frequency and extent of yellow soil moisture variation accelerates considerably by crops growing. However, the influence by crops growing attenuates with the depth, which enables a stable and high content of soil water in the relatively steady layer. When soil contains much water, the moisture variation in 0-20 cm depth of yellow soil under the corn-wheat pattern is much greater than that under the vegetable-vegetable pattern. The bared land holds quite a high soil water content in the 0-100 depth because of limited influence by vegetation evapotranspiration, etc..In summary, it can be seen from all above that the yellow soil in karst mountain areas of Guizhou has an extremely clayey texture, which leads to a strong water-holding capacity, a limited specific water capacity, an extremely narrow range of available soil moisture, an obstacle for water movement upward and downward and a limitation of available soil water in top soil. It is the reason that the yellow soil in karst mountain areas of Guizhou is easily to be attacked by seasonal drought. The runoff coefficient of yellow soil slopes is high under the traditional cropping patterns and the rainfall utilization rate needs to be enhanced. The limited water storage of yellow soil in Spring unbalanced the supply of soil water through a year. Gradient has a positive effect on runoff, and a negative effect on utilization of rainfall and soil moisture content. Crop plantation increases the reception of rainfall during raining period, while increases the soil moisture consumption during the non-raining period. At a certain extent, crop plantation increases the variation of soil water content. Therefore, it is necessary to take an action to start the engineering construction for available rainfall collection and extend the drying farming technologies combined with agricultural, biological measure as well as the measures for soil and water conversation as to maximize the utilization of rainfall and optimize the effect of soil reservoir on the field water supply.更多还原