Knowledge Resource Center for Ecological Environment in Arid Area
| 祁连山青海云杉人工林生态—水文过程研究 | |
| 其他题名 | The Studies on Hydrological and Ecological Processes of the Qinghai Spruce (Picea crassifolia) Plantations in Qilian Mountains |
| 朱喜 | |
| 出版年 | 2018 |
| 学位类型 | 博士 |
| 导师 | 何志斌 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 祁连山是我国干旱区山地的典型代表，为促进山地生态环境建设和发展，国家针对祁连山生态问题，先后实施了多个生态工程项目，祁连山人工林面积有了大幅度的增加。但由于长期以来缺乏科学的理论指导和可持续经营技术，山区人工林体系也出现了土壤旱化、生物多样性降低、系统稳定性差等问题。因此，针对土壤—植被系统水循环过程及其植被调控机理，开展祁连山区青海云杉人工林恢复的生态水文学机理研究对祁连山生态建设具有重要的理论和实践指导意义。本研究针对祁连山生态恢复建设的实际需求及生态水文学研究的热点问题，借助高分辨率遥感技术，采用定位观测、样地调查与室内分析相结合的方法，系统研究了青海云杉人工林物种多样性、林冠截留、蒸腾耗水和土壤水分等动态变化，并结合青海云杉天然林斑块分布与地形因素的关系、林木空间异质性、分布格局以及林龄组成结构在时间尺度上的变化规律，提出青海云杉人工林合理布局模式。主要结论如下：（1）青海云杉人工林群落组成结构及土壤理化性质变化规律。随着人工林的发展（0-45年），林下草本层物种丰富度呈增加的趋势，但生物量却呈显著下降趋势；林下草本层植物主要以圆柱披碱草、青海苜蓿、芨芨草、蒙古蒿、红棕苔草等为主并且随着人工林的发展一些耐阳性的物种逐渐转变成一些耐阴性的物种。随着林龄的增加，林冠郁闭度和叶面积指数逐渐增加，40年左右的青海云杉人工林仅在坡面下边缘形成长势良好的斑块状格局，但并没有通过自疏过程形成异质性较大的林窗。造林还显著的改变了林地的土壤理化性质，随着人工林的发展，林地土壤有机碳、全氮含量均呈现增加的趋势，而土壤pH值及土壤容重呈现降低的趋势。（2）青海云杉人工林林冠截留、蒸腾耗水以及土壤水分动态变化特征。由于郁闭度和叶面积指数较高，青海云杉人工林林冠截留率（40.6±14.8%）大于天然林（35.1±20.7 %），可能会限制人工林林地深层土壤水分的补给。生长季青海云杉人工林日耗水量在0.3~3.1 mm.d-1之间，总耗水量为207.4 mm，占年降水量的46.2%；对比夜间蒸腾量和日蒸腾量，青海云杉人工林夜间蒸腾量占白天32.9%。人工林在30-40年后会出现密度过大、林冠郁闭度和截留率过高等现象，导致土壤水分显著降低（尤其是40-80 cm土层的土壤含水量仅为天然林的60%），但适度的间伐（间伐率20%~40%）能有效缓解土壤旱化并维持人工林系统稳定。在坡面和样线尺度上，不同植被类型不同土层土壤水分均具有良好的时间稳定性特征，时间稳定性样点随着土层深度的增加而增多并且可以较为准确的预测坡面或者样线的平均土壤水分状况。土壤容重、总孔隙度、饱和导水率和植被特征对土壤水分时间稳定性具有重要影响，但其影响程度因不同土层而有所差异，表明干旱区山地森林土壤储水量时间稳定性的复杂性，可能受到土壤、植被、地形以及冻融过程的共同影响。（3）青海云杉人工林建设和抚育管理的理论阈值。青海云杉人工林应布局在坡向N、NE和NW，坡度15~45°之间和海拔2700~3200 m范围；针对半阴坡（NE、NW），应根据坡面面积布设64%左右的人工林斑块即可，而不能规划大面积连片的人工林，否则会造成人力财力的浪费；人工林建设或近自然化改造应以0.25 hm2面积为单元，在≤23 m的尺度上宜构建聚集分布的格局，而在＞23 m尺度上应以随机分布格局为主；处于不同演替阶段的人工林应通过择伐形成不同的林龄组成结构，而择伐的强度及林分密度应根据林木胸径而定，两者呈负指数函数关系。基于生态水文学理论，借助于大量的野外实测数据，本论文较为深入的探讨了祁连山青海云杉人工林恢复的主要生态—水文过程及合理布局模式。研究有助于深化对干旱区山地造林的生态水文学机理的认识，为促进山区人工植被恢复的生态水文过程趋向正向反馈发展积累必要的数据，进一步推动生态水文学理论在山区植被恢复和重建中的推广应用。同时，研究成果可为山区已建成的或者即将种植的人工植被的抚育管理和合理配置提供一定的理论依据。 |
| 英文摘要 | Qilian Mountains are typical representative of the mountain ecosystems in arid regions of Northwest China. To solve the ecological problems of Qilian Mountains, the state has successively implemented several ecological engineering projects, and the area of plantation in Qilian Mountains has increased significantly. Without the scientific guidence and sustainable management technology for a long time, however, soil aridification, biological diversity decline and weak stability of systerm are common problems in artificial forest systems. Based on the water cycle of the soil-vegetation system and the mechanism of vegetation regulation, therefore, research the eco-hydrology mechanism of artificial forests in the Qilian Mountains has important theoretical and practical significance for the ecological construction in arid regions.Aimed at the actual demand of ecological construction in Qilian mountains and the hot topics in eco-hydrology, the species diversity, canopy interception, transpiration water consumption and the soil moisture dynamics of Picea crassifolia plantation has been investigated in this study by the method of combining high resolution remote sensing technology, positioning observation, field investigation and laboratory analysis. In addition, based on the spatial distribution pattern of natural forest patches, the composition and structure of forest age, and the relationship between diameter at breast height and stand density, the theoretical threshold of plantation construction were determined. The main results are as follows:(1) Dynamic changes of the composition structure and soil physical and chemical properties for Picea crassifolia plantations. Afforestation decreased percent cover and aboveground biomass, and increased plant diversity of herbaceous community with plantation development (0-45 years). The herbaceous community was dominated by species in the Elymus cylindricus Honda, Medicago archiducis-nicolai Sirj, Achnatherum splendens Nevski, Artemisia mongolica Nakai, Carex przewalskii Egorova, etc. And some of the photophilous species (shade-intolerant) have gradually turned into some shade-tolerant species as the forest canopy closes. With the increase of forest age, the canopy density and leaf area index increased gradually, about 40 years of plantation was only formed in a well-formed patch pattern on the bottom edge of the slope, but it did not form a forest window with large heterogeneous through the self-thinning process. Afforestation also had significant effects on the soil physical and chemical properties, increasing duration of afforestation was generally associated with lower soil bulk density and pH and with greater soil organic carbon, and total nitrogen.(2) Variation characteristics of the canopy interception, transpiration water consumption and soil moisture dynamics for Picea crassifolia plantations. Due to the highier canopy density and leaf area index in plantation than natural forest, the canopy interception rate of the plantation (40.6±14.8%) is greater than the natural forest (35.1±20.7 %), which may restrict the replenishment of the deep soil moisture in the plantation forest. The daily water consumption of the Picea crassifolia plantation ranged from 0.3 mm d-1 to 3.1 mm d-1. Total water consumption by transpiration was 207.4 mm, it comprised 46.2% of the mean annual precipitation, and the magnitude of the nocturnal water losses was up to 32.9% of daily water losses for Picea crassifolia plantation. High planting density was the main cause of severe soil moisture deficits in the longterm, but it could be mitigated by 20%–40% thinning and maintain the stability of the plantation system. The temporal stability of soil water storage (SWS) within the soil profiles under different vegetation types were strong both on the typical hillslope and sample line scale, and the number of time-stable locations increased with increasing soil depth on both scales, indicating that the SWS intended to be more temporally stable in deeper soil. The selected representative time-stable locations could directly estimate the mean SWSs well on the slope and sample line scale. Soil bulk density, total porosity, saturated soil hydrologic conductivity, and properties of the vegetation affected the temporal stability of SWS. Such effects, however, differed among the different soil layers; this indicated that the temporal stability of SWS in arid mountain forests was complex, and possibly due to the combined influences of soil, plants, and topography at the plot scale.(3) Theoretical threshold of the construction and tending management of the Picea crassifolia plantations. Our results suggested that Picea crassifolia plantations will be effective on the N, NE, and NW slopes, at elevations between 2700 and 3300 m, and on slopes ranging from 15 to 45°. On semi-shady slopes (NE, NW), planted forest patches should occupy 64% of the slope area; a complete slope cover would lead to inefficient use of human and financial resources. Plot area of 0.25 hm2 should be the smallest plot scale for the construction or conversion of nearly-natural Picea crassifolia planted forests. The forest can be arranged in aggregated distribution patterns at the scale less than 23 m, and in random distribution patterns at scales greater than 23 m. For planted forests at advanced stages of succession, different forest age structure can be created by selective logging; the intensity of selective logging can be determined from the negative exponential function relationship between stand density and DBH of Picea crassifolia. Our results provided important references for the development of Picea crassifolia plantations and the conversion of existing plantations.Based on the theory of eco-hydrology and a large number of positioning observation and field survey data, a series of issues concerning the hydrological and ecological processes and the reasonable layout mode of the Picea crassifolia plantations were explored in the middle of the Qilian Mountains, Northwest China. The findings presented in this dissertation add to the knowledge about the eco-hydrology mechanism of mountain afforestation in semi-arid environments. They are of benefit to promote the restoration of artificial vegetation with a positive feedback development in eco-hydrological process. They can also promote the application of the eco-hydrology theory in vegetation restoration and reconstruction areas in the mountains. Moreover, the findings can also provide some theoretical basis for tending management and rational allocation of artificial vegetation that has been built or will be planted in the mountainous areas. |
| 中文关键词 | 祁连山区 ; 青海云杉人工林 ; 生态—水文过程 ; 近自然人工林 ; 理论阈值 |
| 英文关键词 | Qilian Mountains Picea crassifolia plantations Hydrological and ecological process Close-to-nature plantations Theory threshold |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 自然地理学 |
| 来源机构 | 中国科学院西北生态环境资源研究院 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/288147 |
| 推荐引用方式 GB/T 7714 | 朱喜. 祁连山青海云杉人工林生态—水文过程研究[D]. 中国科学院大学,2018. |
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