【作者】 刘江华；

【导师】 刘国彬；

【作者基本信息】 中国科学院研究生院（教育部水土保持与生态环境研究中心） ， 生态学， 2008， 博士

【摘要】 植被是保持水土最积极有效的措施,将人工生态植被的营造与天然植被保护有机结合,促进人工植被向地带性天然植被发展,有效发挥植被的生态服务功能,是黄土高原水土流失区生态恢复的重要途径。本研究以黄土高原大面积栽植的刺槐人工林生态系统为研究对象,系统分析了不同区域刺槐的生长发育特征、刺槐林地的土壤水分养分变化规律、刺槐林下植被的演替及其与环境的关系,探讨了评价植被天然化程度的方法,在此基础上提出了促进人工植被天然化发育的关键技术措施。主要研究结果如下:1.黄土高原显域生境内刺槐的生长和分布主要受降水的影响。低土壤水分条件是刺槐在黄土高原分布和生长的主要限制因素,但不是阻碍黄土高原地带性植被恢复的主要限制因子。刺槐对土壤水分的利用能力很强,其对干旱的适应方式是降低生长速率和高度,严重干旱时,甚至牺牲部分构件(枯梢)。刺槐的生命周期随水分条件的改善而延长。2.刺槐林地土壤肥力恢复速度比撂荒地自然演替快。森林草原区安塞退耕地营造刺槐林后,土壤养分全面恢复,土壤有机质、全氮、碱解氮、全磷、速效磷、速效钾总体上均呈现增长态势。50a与5a刺槐林相比,上述六个指标分别增长了218%、206%、434%、22%、85%和52%;PH值则随刺槐生长年限的增加有逐渐降低的趋势。黄土高原从北至南,土壤有机质、全氮含量呈上升趋势,各地刺槐林均有随林龄增长土壤全氮和有机质逐渐升高的趋势。而土壤pH值的变化规律与前二者相反。3.黄土高原刺槐疏林林下植被不同发育阶段的物种组成与撂荒地植被演替不同阶段基本相似。在森林草原区(安塞)尽管刺槐生长消耗了大量水分,造成深厚的土壤水分低湿层,且很难恢复,但当地地带性植被物种仍能在林下正常生长、演替,能获得与撂荒地相近的生物量。在黄土高塬沟壑区(淳化)刺槐林多为高密度经营,林下植被的发育并未表现出地带性特征,其物种组成和群落结构比较简单。4.对黄土高原刺槐功能性状的测定结果及相关分析表明,不同地域的刺槐在功能性状上并没有明显差异,没有形成适应不同地区气候条件的生态类型,而只是通过调节自身的生长速度,甚至牺牲部分构件来适应环境的变化,尤其是水分条件的变化。铁杆蒿是黄土高原地带性植被的组成成分,其叶性状及其它被测性状之间具有良好的相关性,与大多数环境因子间也建立了密切的相关关系,它通过改变自身的叶面积、比叶面积、叶干物质含量、叶氮磷钾含量、嫩枝干物质含量、茎比密度及植株高度等功能性状来适应不同的气候条件。二者对比,刺槐具有明显的外来物种特征,对黄土高原环境的适应程度比铁杆蒿差。5.利用植被盖度、群落层片结构、物种组成、群落地上部生物量等因子构建了植被天然化发育程度指数的评价方程,即植被天然化程度指数(VNI值),可以定量研究植被天然化程度利用VNI对黄土高原森林草原区南部安塞县不同林龄的刺槐林下植被和不同撂荒年限的退耕地植被进行了天然化程度评价,结果表明,2种类型植被的天然化程度随时间变化的趋势大体一致,但由于刺槐强烈遮荫抑制林下植被生长,刺槐林下植被在幼林期至中龄林阶段的天然化程度有明显的倒退现象。一旦林冠疏开,林下植被迅速发育,其VNI值迅速提高。相关分析结果表明,刺槐林下植被的VNI值与多个环境因子有显著的相关关系。土壤养分条件改善促进植被的天然化。土壤水分条件与VNI值呈负相关,说明刺槐林下植被在严酷的水份条件下仍能维持植被的正向演替,由此推断,在小尺度范围的植被演替可能由当地的气候条件控制,土壤水分的作用不是十分重要。更多还原

【Abstract】 Vegetation restoration is most effective approach on soil and water conservation To combine the benefits of artificial vegetation and natural vegetation and promote the succession process for artificial vegetation naturalization, is an important strategy ecosystem restoration. This paper, aimed at artificial Robinia Pseudoacacia forests, studied on growth characteristics, changes of soil moisture and nutrition succession process of undergrowth, relationship between undergrowth and environmental factors. discussed the methods evaluating vegetation naturalization degree, and a technology to promote the process of vegetation naturalization is also presented. The main results are as follows:1. The distribution and growth of Robinia Pseudoacacia in zonal environment was mainly influenced by precipitation on Loess Plateau. Low soil water content was a main limit factor to the distribution and growth of Robinia Pseudoacacia, but not to the restoration of zonal vegetation. The Robinia Pseudoacacia has very strong ability of water-utilization. Its adaptation strategy for water deficit seems to decrease its growth speed and height. Where it is seriously dry condition, the plant may sacrifice some components (withered tip).2. The rate of soil fertility restoration on Robinia Pseudoacacia woodland was faster than that on abandoned land. After plantation, soil organic matter, total nitrogen, available nitrogen, total phosphorus, available phosphorus and available potassium, were increasing with the growth process . On the contrary, the pH value tended to decrease. Compared with the soil of 5a Robinia Pseudoacacia woodland, six indexes were used to described above of 50a has increased by 218%, 206%, 434%, 22%, 85% and 52% respectively. From southern to northern part on the Loess Plateau, soil organic matter and total N content of tree sites tend to increase with growth age, however, the soil pH tend to decreased.3. Species composition and biomass of Robinia Pseudoacacia woodland undergrowth in different succession stage was similar to that of vegetation in abandoned land. From the results in forestry-grassland region of Ansai site that soil moisture did not hinder the growth and succession of undergrowth, although trees consumed much water in soil, and make soil moisture dryer and dryer.4. 9 kinds of functional traits of Robinia Pseudoacacia and Artemisia gmelinii. were measured, The results showed that almost all functional traits of Robinia Pseudoacacia in different region had not significant difference at same growth stage, which means that Robinia Pseudoacacia did not form new ecotype to adapting the different environment condition, especially to water resources change, and its adaptive strategy to environmental change was to adjust its growth speed, even to lose some of its components. However the Artemisia gmelinii was different from Robinia Pseudoacacia. which had fine correlation with environment factors. It means that the adaptability to environment in the Loess Plateau of Artemisia gmelinii was much better than that of Robinia Pseudoacacia.5 The evaluation model of vegetative naturalization index (VNI) was presented with variables including vegetation coverage, community synusium structure, species composition and aboveground biomass. The result found that VNI may describe the situation of vegetation naturalization in the research. By using of VNI, the vegetation naturalness index of Robinia Pseudoacacia forests undergrowth and vegetation on abandoned land in forest-steppe zone on Loess Plateau. The result showed that the VNI of two types of vegetation tendency of was basically coincident with succession stage. But VNI of undergrowth at later young forest stage and early middle age stage tend to decrease for the density canopy, and VNI of latter basically tended to increase in whole succession process. Once the canopy opened, and the undergrowth could get full sunlight, the succession speed of undergrowth was accelerated, and VNI value was enhanced rapidly. Correlation analysis indicated that VNI value of undergrowth had fine correlation with environmental factors. Favorate soil fertility could improve the process of vegetation naturalization. Soil water content was negatively correlated with VNI, which means that low soil water content did not effect the positive succession of undergrowth.更多还原