山地旱作枣园细根分布格局及其土壤水分生态效应

发布时间：2018-07-24 12:52

【摘要】：红枣林是黄土丘陵区退耕还林(草)工程实施以来一种重要的生态经济林,兼具生产和服务功能,截至到2010年,仅黄土高原榆林地区已有红枣林面积达6.67万hm2。土壤水分一直是限制当地红枣产业持续健康发展的关键因子,准确探明红枣林土壤水分动态、耗水特征以及由此产生的水分生态效应对于红枣林管理有重要指导意义。细根是红枣林吸收水分和养分的重要器官,红枣林细根的空间分布特征反映其吸收利用土壤资源的能力,是影响其生产力及稳定性高低的重要因素。红枣林生命周期一般可分为幼年期、初果期、盛果期和衰老期四个年龄阶段,在各个阶段细根具有不同的分布格局,同样对土壤水分亏缺状况的响应程度和反馈方式也存在差异性。针对黄土丘陵区退耕还林(草)工程能否持续发展的迫切需求以及当地干旱缺水的客观事实,以陕北退耕还林后形成的不同树龄旱作红枣林为研究对象,通过定位监测、调查取样、数理统计和室内模拟相结合的方法对红枣林土壤水分动态、红枣林细根空间分布及其与土壤水分关系、红枣林蒸腾及蒸散发规律等进行了研究,并利用HYDRUS-1D模型分析了红枣林土壤水分的参数敏感性和根系经验分布函数的适用性,以提高HYDRUS-1D模型红枣林土壤水分模拟效率和精度。主要取得了以下结论:(1)旱作红枣林土壤水分研究表明:深层土壤含水量随红枣林树龄增加,呈减少趋势。2014平水年红枣林土壤水分随生育期变化整体呈上升趋势;2015干旱年红枣林土壤水分随生育期变化整体呈下降趋势。各树龄红枣林0~0.6 m土层土壤水分波动较大;0.6~1.8 m土层干旱年时形成季节性低湿层(土壤含水量田间持水率60%);1.8~3.0 m土层土壤水分呈常年低湿状态。持续干旱条件下,前期(雨后7天)2龄、6龄红枣林土壤水分损失率显著高于10龄、15龄红枣林土壤水分损失率,后期(雨后18天)2龄、6龄红枣林土壤水分损失率增速缓和,而10龄、15龄红枣林土壤水分损失率呈显著上升趋势。综上建议干旱年时红枣林在开花坐果期和果实膨大期因增加水分管理措施以有效降低枣树自身奢侈性耗水和非生产性耗水,实现红枣林可持续发展。(2)旱作红枣林细根研究表明:随着红枣林树龄增大,细根根长密度增加,比根长减小;2龄枣树细根主要分布于径向1.5 m以内和垂向1.6 m以上,10龄、15龄枣树细根分布超过径向1.5 m和垂向3 m以上,并在株间形成根系高密度区,6龄枣树细根径向分布范围大于2龄,垂向分布与10龄和15龄接近;不同树龄枣林细根根长密度均随土层深度增加而减小,且主要集中在0~0.6 m土层中;随着树龄增加,细根根长密度径向分布无差异(10龄和15龄)。不同树龄枣树径向0.5 m处土壤水分均值和1.5 m处土壤水分均值均存在显著差异(p0.05),且离树干越远,土壤含水量越高。各树龄红枣林细根根长密度(不包括2龄)、比根长均与土壤含水量呈显著线性相关(p0.05),前者斜率随树龄的增大而增大;后者斜率随树龄增加而减少。(3)旱作红枣林蒸腾耗水规律与土壤水分生态效应研究表明:枣树液流速率日间呈单峰型变化趋势,阴天液流速率整体均低于晴天时液流速率,且液流速率呈不规则波动。枣树生育期蒸腾变化大致可分为:萌芽展叶期缓慢增加、开花坐果期迅速增加、果实膨大期高耗水阶段和果实成熟期蒸腾回落阶段;受降雨量影响,平水年生育期红枣林蒸腾耗水量显著高于干旱年蒸腾耗水量(p0.05),表明土壤水分增加促进枣树蒸腾,土壤水分亏缺抑制枣树蒸腾。枣树蒸腾量和株间蒸发量占红枣林总耗水量比例随生育期进行呈不规则变化。平水年生育期内降雨量满足10龄红枣林耗水需求,但干旱年土壤水分亏缺现象严重,并在一定程度上延缓了10龄红枣林生长发育。平水年红枣林生育期耗水量随树龄增加呈上升趋势;干旱年6龄以上红枣林耗水量随树龄增加呈下降趋势。如何将耗水量控制在生育期内多年平均降雨量线(360.1 mm)以下是旱作红枣林健康持续发展的关键。在降雨少、雨量小的萌芽展叶期和开花坐果期,红枣林主要吸收利用中层和深层土壤水(0.6~2.0 m),在降雨充沛的果实膨大期和果实成熟期主要吸收利用根系密集层土壤水(0.2~0.6 m),整个生育期内对表层土壤水(0~0.2m)的使用较少,因此提高0.2~0.6 m土层土壤含水量是当前旱作红枣林水分管理重点。红枣林内外土壤含水量存在显著差异,旱作红枣林在持续干旱情况下主要对1.4 m以下土层土壤水分产生影响。(4)旱作红枣林土壤水分模型模拟结果表明:旱作枣园30~50 cm土层水分易受土壤水分运动参数、气象参数和枣树生长指标影响;表层10 cm处土壤水分主要受表层土壤饱和含水量、孔径指数、土壤饱和导水率和降雨量影响;深层土壤水分(90 cm土层)主要受气温、总光照辐射通量、叶面积指数、根系深度、树高等影响影响。线性根系分布函数可近似反映红枣林根系实际分布情况,且参数简单易获取,具有一定的实用性。HYDRUS-1D模型对6龄、10龄、15龄红枣林各土层含水量模拟值和实测值均方根误差RMSE处于0.05~0.016,相对误差RE均在0.05以下,决定系数R2均在0.6以上,说明Hydrus对不同树龄旱作红枣林土壤水分具有良好的模拟精度。
[Abstract]:Red date forest is an important eco economic forest since the project of returning farmland to forest (grass) in the loess hilly region. By 2010, the area of the red jujube forest in Yulin area of the Loess Plateau has reached 66 thousand and 700 hm2. soil moisture, which has been the key factor restricting the sustainable and healthy development of the local red date industry. The soil water dynamics, water consumption characteristics and the resulting water ecological effect have important guiding significance for the management of the red date forest. The fine root is an important organ for the absorption of water and nutrients in the red date forest. The spatial distribution characteristics of the fine root of the red date forest reflect its ability to absorb and utilize the soil resources, which is important to influence its productivity and stability. The life cycle of the red jujube forest can be divided into four stages in the early stage, in the early fruit period, in the fruit period and in the aging period. There are different distribution patterns in the fine roots of each stage, and the response degree and the feedback way of the soil water deficit are also different. With the objective fact of drought and water shortage in the local area, the soil moisture dynamics of the red date forest, the spatial distribution of the fine root of the red date forest, the relationship with the soil moisture, the red date of the red date forest, and the red date of the red date forest were studied by the method of location monitoring, sampling, mathematical statistics and indoor simulation. The forest transpiration and the law of evapotranspiration were studied, and the HYDRUS-1D model was used to analyze the sensitivity of soil moisture and the applicability of the root experience distribution function in the red date forest to improve the efficiency and accuracy of Soil Moisture Simulation in the HYDRUS-1D model. The following conclusion was obtained: (1) the soil moisture of the dry Chinese jujube forest shows that the depth of soil moisture in the red date forest is deep. The soil moisture content of the layer soil increased with the age of the red date forest. The soil moisture content of the red date forest in.2014 flat was increased with the growth period. The soil moisture in the 2015 dry year red date forest decreased with the growth period. The soil moisture in the 0~0.6 m soil layer of each tree age red jujube forest was greatly fluctuated; the formation season of the 0.6~1.8 m soil layer was formed in the dry year. The low wet layer (soil water content of soil water content was 60%), the soil moisture in 1.8~3.0 m soil layer was in a permanent low humidity condition. Under the continuous drought condition, the soil moisture loss rate of the 6 years old red date forest was significantly higher than that of the 10 years, the 6 years old jujube forest soil water loss rate, the 15 age red date forest soil water loss rate, the later period (18 days after rain), and the soil moisture loss rate of the 6 year old jujube forest The soil moisture loss rate of the 10 years old and 15 years old red date forest increased significantly. In a comprehensive study, it is suggested that the jujube forest in the flowering period and the fruit expansion period can effectively reduce the extravagant water consumption and non productive water consumption of jujube trees in the period of flowering and fruit expansion, and realize the sustainable development of the jujube forest. (2) the fine root research table of the dryland jujube forest With the increase of the age of the red jujube trees, the length density of fine root increases and the root length decreases, and the 2 years old date tree root is mainly distributed within 1.5 m and over 1.6 m, 10 years old, and the 15 years old date tree root is more than 1.5 m and more than 3 m, and the high density zone is formed between the plants. The radial distribution of the fine root of the date tree is larger than the 2 age, and the vertical distribution of the fine root of the jujube tree is more than 2. The cloth was close to 10 and 15 years old. The root length density of the root root of different tree ages decreased with the increase of soil depth, and mainly concentrated in the 0~0.6 m soil layer. With the increase of tree age, the radial distribution of the length density of fine root roots was not different (10 and 15 years old). The mean value of soil moisture and the mean value of soil moisture at 1.5 m at the radial 0.5 m of different tree age trees were significant The difference (P0.05), and the farther from the tree trunk, the higher the soil water content. The length density of the root root of the red date forest of each tree age (not including 2 years old), the root length and soil water content showed a significant linear correlation (P0.05). The slope of the former increased with the age of tree age; the slope of the latter decreased with the age of tree age. (3) the law of water consumption and soil water generation in Dryland jujube forest The study of state effect showed that the flow rate of jujube in day showed a single peak change trend, and the liquid flow rate of the cloudy day was lower than that of the clear day, and the liquid flow rate was irregular. The change of the transpiration of the date tree during the growth period could be roughly divided into the following: the gradual increase of the germination period, the rapid increase of the flowering time, the high water consumption stage and the fruit in the period of the fruit expansion. The evapotranspiration was significantly higher than that of the annual evapotranspiration (P0.05), which indicated that the increase of soil moisture promoted the transpiration of jujube trees, and the soil water deficit inhibited the transpiration of jujube trees. The rainfall in the annual growth period met the demand for water consumption in the 10 year old red jujube forest, but the soil water deficit was serious in the drought year, and to a certain extent delayed the growth of the 10 year old red jujube forest growth. The water consumption of the red date forest in the flat water year increased with the increase of the tree age; the water consumption of the red date forest in the dry year 6 years old increased with the age of the tree. It is a declining trend. How to control the water consumption under the average annual rainfall line (360.1 mm) is the key to the healthy and sustained development of the dryland jujube forest. In the period of low rainfall, small rainfall and flowering and fruit setting, the red date forest mainly absorbs and uses the middle and deep soil water (0.6~2.0 m), in the period of heavy rainfall and the period of fruit expansion. The fruit ripening period mainly absorbs and uses the soil water of the root dense layer (0.2~0.6 m), and the use of surface soil water (0~0.2m) is less in the whole growth period. Therefore, increasing the water content of the soil layer of 0.2~0.6 m soil is the key point of water management in the current Dryland jujube forest. There is a significant difference in soil moisture content inside and outside of the red date forest, and the drought of the red jujube forest in the continuous drought situation. The soil moisture content of soil layer under 1.4 m was affected. (4) the simulation results of soil moisture model in dry Chinese jujube forest showed that water content of 30~50 cm soil layer in dry jujube garden was easily affected by soil moisture movement parameters, meteorological parameters and date tree growth index; soil moisture content in surface 10 cm was mainly saturated with water content of surface soil, pore size index and soil satiety. And the influence of water conductivity and rainfall; deep soil moisture (90 cm soil layer) mainly affected by temperature, total light radiation, leaf area index, root depth, tree high influence. Linear root distribution function can reflect the actual distribution of root system of red date forest, and the parameters are simple and easy to obtain, with a certain practical.HYDRUS-1D model to 6 years, 10 The mean square root error RMSE in the soil water content of 15 years old red date forest is 0.05~0.016, the relative error RE is below 0.05, and the determination coefficient R2 is above 0.6. It shows that Hydrus has good simulation precision on soil moisture of different tree age dry red date forest.
【学位授予单位】：西北农林科技大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S665.1;S152.7

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