【作者】 张翠萍；

【导师】 万贤崇；

【作者基本信息】 中国林业科学研究院 ， 生态学， 2014， 博士

【摘要】 核桃（Juglans regia L.）-绿豆（Vigna radiata L.）复合间作作为“立体林业”（Stereoforesting）的一种生态经济林营造模式，是太行山区退耕还林工程中推广应用最广泛的生态经济林模式之一。本研究以核桃为研究对象，调查了田间核桃-绿豆复合系统中土壤水肥空间变化规律；通过温室模拟核桃-绿豆间作、养分控制试验，研究固氮植物绿豆和氮、磷元素对核桃苗木水分平衡、光合生理特性和生长的影响；进一步了解核桃苗木养分状况对其水分平衡的影响。为太行山低山丘陵山区的农林复合系统优化经营模式提供理论依据。主要研究结果如下：1、土壤水分研究结果显示：核桃-绿豆复合系统、单作核桃及单作绿豆土壤水分空间变化趋势基本一致。在垂直方向上，随土层深度的增加，土壤含水量增加，40cm土层以下递增幅度减小；在水平方向上，0-20cm土层含水量随距离林带越远含水量越少；20-80cm土层随距离林带越近，土壤含水量越少。三种经营方式垂直变化梯度上存在差异，0-20cm土层含水量单作核桃>核桃-绿豆>单作绿豆，20-80cm土壤含水量则是单作绿豆>核桃-绿豆>单作核桃。土壤养分研究结果显示：核桃-绿豆复合系统与单作绿豆土壤有效氮、速效磷、速效钾和有机质含量均有一定的表聚性。垂直方向上，土壤有效氮除外，其它养分含量均随土层深度增加而降低；在水平方向上，0-20cm土层养分含量随距离林带距离增加，养分含量降低；20-80cm土层养分随距离林带距离增加含量增加；与单作核桃相比，核桃-绿豆复合系统土壤养分含量高于单作核桃。核桃、绿豆对土壤养分需求情况为有效氮>速效磷>有机质>速效钾。2、种植绿豆可以增加土壤氮素含量和核桃茎内氮含量，但对叶和根系中的氮含量影响不明显。种植绿豆显著地增加不施氮素核桃的根系生长、高生长和直径生长，但是种植绿豆非但没有增加正常供氮核桃的生长反而降低了生长。无论种植绿豆与否，不供氮处理降低了核桃的总叶面积，而提高它们的根/冠比。核桃叶片气体交换对各处理的响应和生长有相同的趋势。缺氮显著降低了核桃叶柄在中午的导水率、提高了相应的导水损失率；种植绿豆显著提高不供氮核桃的导水率，降低了其导水损失率。然而，种植绿豆使正常供氮核桃导水率降低、导水损失率加剧。另一方面，绿豆受到间作的竞争压力，其产量和生物量有所下降。3、结果显示：pH与磷素对核桃苗木的影响是两个相互独立的过程，酸性（pH3.0）条件下，核桃苗木根系生物降低、根冠比减小，根系导水率降低，对磷素的吸收利用减小，尽管其正常供磷但各生长指标及生理指标反应与磷胁迫条件下反应相似；但两因素具有一定叠加性，在磷胁迫条件下，酸化（pH3.0）进一步加剧对核桃苗木的损害。各指标具体变化如下：酸化及磷胁迫条件下核桃根系水分导度降低，叶柄木质部结构改变，导管密度降低，木质部导管栓塞程度增加，叶柄导水率下降，植株水分运输效率降低，叶片水势降低，诱导气孔关闭；气孔导度降低，光合作用下降；胁迫条件下，叶绿素荧光参数Fv/Fm、ΦPSⅡ、qP下降NPQ增加，核桃苗木受胁迫环境损害，叶片PSⅡ光合电子传递活性受到抑制，光合能力下降。4、不同氮素水平对核桃苗木生长、水分平衡和光合特性的作用研究结果显示：正常供氮苗木叶面积及叶片气孔增加，促进苗木及根系生长；低氮或者高氮条件下苗木生长指标和生理指标降低。适量氮素增加叶柄导管直径、纹孔径和穿孔径，导管水分运输效率增加；低氮和高氮处理叶柄及根系导管密度均降低，根系导水力降低，叶片水势降低，导水损失率增加；叶片气体交换指标与根系导水率和叶片水势趋势一致。氮素浓度过高核桃苗木叶片Fv/Fm值低于0.8，光合机构遭受一定损害。核桃苗木根压具有周期性变化，不同氮素浓度下最高值均能达到25Kpa以上，足以修复由于强烈蒸腾造成的木质部栓塞。5、不同氮素条件下核桃苗木对干旱胁迫有着不同的应对机制：低氮处理苗木较正常供氮处理叶面积减小，叶片气孔密度增加，叶柄木质部安全性增加，随土壤含水量降低，叶柄及根系导水率降低，叶片气孔导度降低，减少水分损失，叶片光合作用下降，根冠比增加，减少地上部分耗水，调整植株适应干旱胁迫的策略，严重干旱条件，低氮对苗木导水能力和光和能力的促进作用高于正常供氮处理；复水后，苗木水分运输能力迅速恢复，光合能力恢复。高氮处理苗木较正常供氮处理，根冠比降低，栓塞脆弱性增加，水分运输能力降低，地上耗水增加，加剧干旱胁迫的负面效应，随土壤含水量降低，苗木叶柄导水损失率增加，叶片水势降低，气孔导度降低，植株降低叶片水分蒸腾和光合作用应对土壤干旱胁迫；复水后，苗木光合能力降低。正常供应氮素促进苗木根系生长，水分运输能力提高，苗木光合能力最强，耗水最快；在正常供水和轻度干旱条件下，苗木根系增加，导管直径增加，水分运输效率提高，保证植株正常生理活动；极度干旱条件下，苗木根系导水力降低，叶柄导水损失率增加，降低叶片气体交换指标，正常供应氮素促进作用减弱并转向抑制；复水后，苗木补偿效应最为明显。更多还原

【Abstract】 Walnut-mung bean intercropping is one of main agroforestry patterns in hilly region ofTaihang Mountain in China. In this study, spatial distributions of water and nutrients in soilwere investigated in walnut-mung bean intercropping field. A potting experiment wasconducted in a greenhouse to study effects of nitrogen-fixing plant, mung bean, and nitrogenfertilizer on walnut water balance, gas exchange and growth. Moreover, influence of nutrientson walnut water relations was explored through a nutrient control experiment. This study aimsat providing a theoretical basis for understanding the competition and facilitation betweendifferent components in agroforestry systems and improving management model of theagroforestry systems in the Taihang Mountain. The main findings are as follows:1、The spatial distribution of water in soil: The change patterns of soil moisture weresimilar in the walnut and mung bean monocroppings and the walnut–mung bean intercroppingsystems. In vertical direction, soil moisture increased with increasing soil depth, however thevariation magnitude of soil moisture decreased from40to80cm soil layers. In the horizontaldirection, in0-20cm soil layers, the farther the distance was from the forest belt, the lower ofsoil moisture, and in20-80cm soil layers, the closer the distance was from the forest belt, thelower the soil moisture. There was difference in the decline rate of soil moisture in the verticaldirectionin the monocroppings and the intercropping systems. In20-80cm soil layers, the soilmoisture in mung bean monoculture was highest, then was the agroforestry system, and the soilmoisture in walnuts monoculture was lowest. In0-20cm soil layer, the order of soil moisturewas mung bean monoculture the agroforestry system walnut monoculture.The spatial distribution of nutrient in soil: Walnut-mung bean intercropping and mungbean monoculture field had the highest nutrient content in shallow soil layers. In verticaldirection, phosphorus and potassium and soil organic matter content decreased with increasingsoil depth; In horizontal direction, in0-20cm soil layer, the farther the distance was from the forest belt, the lower of soil nutrients; and in20-80cm soil layer, the farther the distance wasfrom the forest belt, the higher the soil nutrients. Soil nutrient content of different layers inagroforestry system were more than walnut monoculture. The requirement of walnut and mungbeans to soil nutrients was available nitrogen> available phosphorus> organic matter>available potassium.2、The study was to explore effects of V. radiata, a nitrogen fixing-crop, on growth, waterbalance and gas exchanges of the intercropping J. regia seedlings and to investigate thehydraulic mechanism involved in photosynthesis and growth. We measured growth, hydrauliccharacteristics, and gas exchanges of J. regia seedlings, analyzed the effects of theintercropping nitrogen fixing V. radiata on xylem anatomic structure, water balance andphotosynthetic characteristics of J. regia seedlings under nitrogen deprivation and abundance.Results showed that under the condition of nitrogen deficiency, the nitrogen fixing V. radiatafacilitated growth of the intercropping J. regia seedlings by improving xylem development,water transport and hydraulic characteristics in high transpiration demand. However, withnitrogen addition, V. radiata plantation inhibited growth of J. regia likely by competing waterand other elements with the intercropping J. regia.3、The growth, hydraulic characteristics, and photosynthetic characteristics of J. regiaseedlings were measured in this study, to explore effects of phosphorous deficient soils withdifferent pH values on growth, water balance and photosynthetic characteristics of J. regiaseedlings. The results showed that: With phosphorous, pH3significantly reduced the P uptakeefficiency and P use efficiency of J. regia seedlings, and had similar reaction with phosphorusstress in the growth and physiological indexes. With phosphorous deficient, pH3increased thepoisoning effect of stress environment on J. regia seedlings. The change of indexes as follows:Under stress conditions the root growth of J. regia seedlings was inhibited, the root area toabsorb water and fertilizer was reduced, the development of petiole xylem was changed, thevessel density decreased, and PLC increased, water transport capacity decreased, inducedstomatal closure. With the stomatal conductance decreased, photosynthesis declined, the phenomenon of photoinhibition of J. regia leaf was induced and photo-oxidative was damaged,Fv/Fm, ΦPSⅡ, qP declined, optical systems starts physiology protection mechanisms, NPQincreased, to reduce photo-oxidative damage, regulated the ability of J. regia seedlings to adaptto environmental, affected the growth of J. regia seedlings.4、This study explored of nitrogen on growth, water balance and photosynthesis of walnutseedlings. The results showed that: leaf area, stomata size and root growth increased undernormal nitrogen supply, while indicators were towards downward trends under high nitrogensupply. Vessel diameter, pit diameter, and perforation diameter of petiole were increased bynitrogen, thus water transport efficiency of vessel was enhanced; While vessel density ofpetiole decreased by both high and low nitrogen, resulting in reducing of leaf water potentialand increasing of water loss rate. Vessel diameter and density were consistent to that of petiole,and root hydraulic conductivity decreased both under high and low nitrogen; While leaf gasexchange and vessel density had the same trend with leaf water potential. Leaf photosyntheticapparatus was damage to a certain degree by high nitrogen treatment and FV/Fmvalue wasbelow0.80. Periodical changes were present in the root pressure of walnut and the maximumvalues could all reach above25Kpa, which was sufficient to repair xylem embolism becauseof strong transpiration.5、Walnut seedlings with different nitrogen concentration conditions response distinctly todrought stress by adopting different coping mechanisms: Low concentration of nitrogentreatment increased root-shoot ratio, leaf stomata density and petioles xylem safety, anddecreased leaf area of seedling. Meanwhile, as soil moisture constant deduced, hydraulicconductivity of petiole and root and stomata conductance were decreased to reduce water loss,furthermore, leaf photosynthesis was also decreased to reduce water consumption fromabover-ground part of plant, which aimed to adjust its strategy of adapting to drought stress.On the other hand, after re-watering treatment, water transporting and photosynthetic ability ofseedlings quickly recovered. Besides, high concentration of nitrogen treatment decreased rootgrowth, root hydraulic conductivity of plant. As soil moisture constant deduced, petiole hydraulic conductivity loss rate was increased, and leaf water potential and were deduced todecrease the leaf transpiration and photosynthesis rate to response to drought stress. However,after re-watering treatment, photosynthetic ability of seedling was decreased. Normal amountsupply of nitrogen promote root growth, water transporting ability, water consumption andphotosynthetic ability of seedlings. Besides, at normal water and mild drought condition,seedling increased root amount, vessel diameter, and water transportation efficiency, to ensurenormal physiological activities. At extreme drought condition, seedling reduced its roothydraulic conductivity and index of leaf gas exchange, also increased petiole hydraulicconductivity loss rate, and adjusted itself to adapt to drought stress. On the one hand, afterre-watering treatment, compensation effect of seedling was most significant.更多还原