黄土区植物生长与土壤水分协同关系及土壤水分有效性评价

发布时间：2018-12-25 14:39

【摘要】：土壤水分有效性是当今生态学、土壤学和植物学科关注的热点,亦是制约旱区陆地生态系统生产力的主要限制因子之一,全球气候变化对区域生态建设和植被功能提升带来了严峻挑战。黄土高原年均降雨量小,且有效的天然降水在年际间变幅大,年内分布不均,常常导致植物生育期内的降雨无法满足植物的正常生长。因此,开展黄土区植物生长与土壤水分协同关系研究对本地区植被恢复可持续发展具有重要理论意义。本研究选取黄土高原地区四种典型植物,分别为乔木—刺槐(Robinia pseudoacacia L.),灌木—紫穗槐(Amorpha fruticosa L.),草本—苜蓿(Medicago sativa L.)及作物—玉米(Zea mays L.),进行了持续的干旱试验(其中刺槐和紫穗槐进行了交替干旱控制试验),监测了土壤水分下降时植物叶水关系、气体交换、荧光参数和土壤呼吸等生理参数的变化,系统的分析了不同类型植物的土壤水分有效性阈值及交替干旱下植物生长策略的响应;同时,通过对黄土高原及秦岭八个地区132个植物样本叶片碳同位素和养分的测定,探讨了区域尺度上植物水分利用效率(WUE)的影响因素,揭示了WUE与植物养分计量比的关系。研究结果为明确区域土壤水分有效性地带性规律提供了重要信息,为该区生态恢复可持续发展提供了理论依据。本研究主要取得以下结论:(1)持续的干旱控制试验研究表明,四种植物叶水关系、气体交换及荧光参数均随着土壤水分下降,可分为三个阶段:先保持稳定,然后随土壤水分的下降快速下降,随后又缓慢下降;气体交换参数对土壤水分的敏感性高于叶片相对含水量及荧光参数,在较低的土壤水分下木本植物表现出较高的气体交换速率;四种植物土壤含水量与植物叶片各生理参数均表现出显著的相关性,土壤水分降低是本研究中导致植物生理参数下降的主要原因;土壤呼吸对土壤水分下降十分敏感,除紫穗槐外,其它三种植物土壤呼吸随土壤水分下降均表现出先快速下降后缓慢下降的趋势。(2)交替干旱对刺槐和紫穗槐生长策略影响的研究表明,干旱胁迫对两种植物生理参数产生了显著影响,且两种植物对干旱胁迫的响应表现出一定的差异。干旱胁迫早期,刺槐的气孔关闭行为可能主要受到脱落酸(ABA)调控,后期转变为水势调控,而紫穗槐可能主要受到水势调控;干旱胁迫引起植物茎粗的收缩,会导致韧皮部功能受损,影响植物光合产物的运输及分配。其次,植物生理参数显著变化时的土壤水分阈值在两次干旱胁迫中表现出一些差异,除地上部呼吸以外,第二次干旱时植物生理参数显著变化时的土壤水分阈值均高于第一次干旱时,荧光参数显著变化时的土壤水分阈值最低,这些变化表明重复干旱可能会加快植物的死亡;由于干旱胁迫导致的叶片脱落,尽管土壤呼吸在复水后迅速恢复,但是植物地上部光合及呼吸在复水后并不能完全恢复;此外,两种植物黎明前叶水势与气体交换参数之间均表现出极强的相关性,且两次干旱中表现出一定的差异;复水后,两种植物叶水势恢复速度快于气体交换参数,蒸腾作用的恢复模式表明两种植物气体交换参数的恢复主要受到水力因素的限制,在刺槐中还可能涉及到非水力因素调控。(3)四种植物的土壤水分有效性研究表明,当土壤含水量大于某一阈值时,土壤水分对植物各生理参数等同有效,而当土壤水分继续下降后,各生理参数土壤水分有效性快速下降;不同的生理参数表现出不同的土壤水分有效性阈值,气体交换参数土壤水分有效性阈值最高,荧光参数土壤水分有效性阈值最低,综合考虑,光合参数适宜于四种植物土壤水分有效性评价,叶片相对含水量对于苜蓿和玉米土壤水分有效性的评价也同样适用;不同植物土壤水分有效性阈值也表现出一定的差异,木本植物土壤水分有效性阈值低于草本植物;此外,交替干旱也显著影响了植物的土壤水分有效性阈值,植物经历干旱后土壤水分有效性阈值提高。(4)区域尺度上植物WUE与年降水显著负相关,不同生活型植物WUE也不相同,草本植物最低;此外,N限制会导致WUE降低。同时研究还表明植物WUE与养分计量比存在相关性,在灌木和乔木植物中,叶片N:P和WUE显著正相关,而在草本植物中,WUE与P和K含量显著负相关;此外,植物WUE与养分计量比的关系还受到养分限制的影响,当植物处于非P限制时,植物WUE与叶片N:P显著正相关,而当植物处于P限制时,植物WUE与叶片K含量显著相关。
[Abstract]:The effectiveness of soil moisture is a hot spot of the present ecology, soil science and plant subject. It is also one of the main limiting factors that restrict the productivity of land ecosystem in the arid region, and the global climate change poses a serious challenge to the regional ecological construction and the improvement of the function of the vegetation. The average annual rainfall of the Loess Plateau is small, and the effective natural precipitation is large in the inter-year period, and the distribution of the natural precipitation is not uniform in the year, and the rainfall in the growth period of the plant is often caused to be unable to meet the normal growth of the plant. Therefore, the study of the relationship between plant growth and soil moisture in the loess area is of great theoretical significance to the sustainable development of vegetation restoration in the region. The four typical plants in the Loess Plateau were selected as Robinia pseudoacacia L., Aphrosia pseudoacacia L., Medicago saativa L. and Zea mays L., respectively. The changes of the physiological parameters such as leaf water, gas exchange, fluorescence parameters and soil respiration were monitored by the continuous drought test (in which the black locust and the Amorpha fruticosa were subjected to the alternating drought control test), and the relationship between the water and the water, the gas exchange, the fluorescence parameters and the respiration of the soil were monitored. The soil moisture availability threshold of different types of plants and the response of the plant growth strategy under the alternating drought were analyzed in the system, and the carbon isotope and nutrient content of 132 plant sample leaves in the Loess Plateau and the eight regions of the Qinling Mountains were determined. The influence factors of plant water use efficiency (WUE) on the regional scale are discussed, and the relationship between WUE and plant nutrient measurement ratio is revealed. The results of the study provide a theoretical basis for the sustainable development of the ecological restoration in the region. The results of this study are as follows: (1) The study of the continuous drought control shows that the water-water relationship, the gas exchange and the fluorescence parameters of the four kinds of plant leaves can be divided into three stages with the decrease of the soil moisture. the sensitivity of the gas exchange parameters to the soil moisture is higher than the relative water content and the fluorescence parameters of the leaves, and the woody plants show higher gas exchange rate at lower soil moisture; The soil water content of the four kinds of plants has a significant correlation with the physiological parameters of the plant leaves. The decrease of soil moisture is the main cause of the decline of the physiological parameters of the plant in the study, and the soil respiration is very sensitive to the decrease of the soil moisture, except for the Amorpha fruticosa, The decrease of soil moisture in the other three kinds of plant soil showed a tendency to decline slowly. (2) The study of the effect of alternating drought on the growth strategies of Robinia pseudoacacia and Amorpha fruticosa indicated that the drought stress had a significant effect on the physiological parameters of the two plants, and the response of the two plants to the drought stress showed a certain difference. In the early stage of drought stress, the stomatal closure behavior of the Robinia pseudoacacia may be mainly controlled by abscisic acid (ABA), the later transition is water potential regulation, and the Amorpha fruticosa may be mainly controlled by the water potential; the drought stress causes the plant stem to shrink, which can lead to the damage of the phloem. and the transportation and distribution of the plant waste products are affected. secondly, the soil moisture threshold value of the plant physiological parameter changes significantly when the physiological parameter of the plant changes significantly, The lowest soil moisture threshold at the time of a significant change in the fluorescence parameters indicates that the repeated drought may accelerate the plant's death; due to the leaf shedding due to drought stress, although the soil respiration recovers rapidly after the complex water, but the photosynthesis and respiration of the aerial part of the plant can not be fully recovered after the complex water; in addition, the water potential and the gas exchange parameters of the two plants have a strong correlation with the gas exchange parameters, and a certain difference is shown in the two drought; after the complex water, The recovery rate of two kinds of plant leaf water potential is faster than that of the gas exchange parameter, and the recovery mode of the transpiration effect indicates that the recovery of the two plant gas exchange parameters is mainly limited by the hydraulic factors, and the non-hydraulic factor control can also be involved in the locust. (3) The study of soil moisture availability of four kinds of plants shows that, when the water content of the soil is greater than a certain threshold, the soil moisture is equivalent to the physiological parameters of the plant, and when the soil moisture continues to fall, the soil moisture content of each physiological parameter is rapidly reduced; Different physiological parameters show different soil moisture availability thresholds, the water availability threshold of the gas exchange parameters is the highest, the water availability threshold of the fluorescence parameters is the lowest, and the comprehensive consideration is that the photosynthetic parameters are suitable for the evaluation of the soil moisture effectiveness of the four plants, the relative water content of the leaves is also applicable to the evaluation of the soil moisture availability of the plant and the corn, the soil moisture availability threshold of different plants also shows a certain difference, and the soil moisture availability threshold of the woody plant is lower than that of the herbage; in addition, The soil moisture availability threshold of the plants was also significantly affected by the alternating drought, and the threshold of soil moisture availability after the plant was subjected to drought was increased. (4) The plant WUE in the regional scale is negatively correlated with the annual precipitation, and the WUE of different living plants is different and the herb is the lowest; in addition, the N limit can lead to the reduction of the WUE. At the same time, the relationship between the plant WUE and the nutrient measurement is also shown, and in the shrub and arbor plants, the leaves N: P and WUE are significantly positively correlated, and in the herbaceous plants, the WUE is negatively correlated with the P and K content; in addition, The relationship between the plant WUE and the nutrient measurement ratio is also affected by the nutrient limitation, and when the plant is in the non-P limit, the plant WUE is significantly positively correlated with the leaf N: P, and when the plant is at the P limit, the plant WUE is obviously related to the content of the leaf K.
【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】：2017
【分类号】：S152.7

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