NWIPB OpenIR
黄河源区高寒草甸退化的生态学过程及其驱动力分析
Alternative TitleAanalysis of ecological process and driving forces of alpine meadow degradation in headwater region of the Yellow River
乔有明
Subtype博士
Thesis Advisor王启基
2009-06-02
Degree Grantor中国科学院西北高原生物研究所
Place of Conferral西北高原生物研究所
Keyword高寒草甸 演替 黄河源区 主成分分析 驱动力
Abstract黄河源区位于青藏高原中东部的三江源自然保护区的核心区,是我国和东南亚国家生态系统安全和区域可持续发展的生态屏障。随着人类活动干扰和气候变化对青藏高原的影响,导致该区生态系统平衡失调,草地退化日趋严重。由于黄河源区生态系统的特殊性和植被、土壤、气候因子和人类活动之间相互作用的复杂性,对于高寒草甸退化的机制和驱动力还缺乏系统的研究。本项研究旨在通过对黄河源区退化高寒草甸的植物群落特征和土壤特征调查,揭示植物和土壤养分对土地退化的响应;对源区人口及牲畜数量和国内生产总值,气候变化特点等因子的分析,量化人为干扰因子和自然因子的贡献率以及各因子之间的数量关系;以及对草地退化驱动力分析以及原生草地植被封育、人工草地、半人工草地的自然演替变化规律的研究,为高寒草甸退化草地恢复与重建提供科学依据。 本研究采用常规的生态学野外调查、土壤实验室分析、气象资料的整理,主成分分析和多元回归分析等方法,通过对黄河源区植被、土壤、人为干扰因子和主要气象因子变化以及草地退化的生态学过程和驱动力分析,得到以下主要结论: 1. 不同退化演替阶段高寒草甸群落的物种组成有明显的不同。重度退化草地的指示种主要是细叶亚菊(Ajania tenuifolia)、兰石草(Lancea tibetica)、西伯利亚蓼(Polygonum sibiricum)、高原毛茛(Ranunculus tanguticus)和紫花地丁(Viola yedoensis)等,它们的指示值显著高于其它物种(P<0.01),而且均为杂类草。中度退化高寒草甸的指示植物有阿尔泰狗哇花(Heteropappus altaicus)、矮嵩草(Kobresia humilis)、黑边假龙胆(Gentianella azurea)和毛茛(Ranunculus japonicus)等。随着高寒草甸退化程度加重,原生植被的优势种逐渐减少,优势度降低,草地间的相似性指数减小。 群落物种丰富度指数随退化程度的加深而减少,依次为轻度退化草地>中度退化草地>重度退化;不同退化草地间Shannon-Weiner多样性指数差异极显著,大小顺序为轻度退化>中度退化>重度退化;物种均匀度指数由高到低依次为轻度退化>中度退化>重度退化。 多样性和均匀性指数与草甸质量盖度指数之间关系的可以分别用二次方程式进行描述,当高寒草甸的草地质量指数在15%以下时,多样性和均匀性指数均较低,介于15%~45%之间时两者都很高,大于45%后,有下降的趋势;物种丰富度与草甸质量盖度指数之间的关系可用三次方程式进行描述。当莎草和禾类草所占盖度大于20%时,物种丰富度和草甸质量指数之间没有明显的相关关系。 2.随着退化程度的加剧,土壤容重在各层均呈现增加的趋势。轻度退化草地的土壤含水量明显高于重度退化草地土壤含水量。土壤平均有机碳含量(0~30cm)由高到低表现为:轻度退化>中度退化>重度退化;在0~10cm土层,随着退化程度的增加,土壤有机碳含量逐渐减少,其中轻度退化与中度退化和重度退化高寒草甸间差异极显著(P<0.01),10 cm以下各土层有机碳含量不存在差异极显著性(P>0.05)。土壤全氮含量与有机碳含量的变化规律基本相似,0~30cm土体平均土壤全氮含量由高到低表现为:轻度退化>重度退化>中度退化>人工草地。所有草甸不同土层的C/N比较接近。 3.黄河源区四县53年间将近增加了7万人,呈直线增加趋势,每年增加人口的速度为2.05%,即平均每年大约净增加1350人左右;源区各县牲畜数量经历了前期的迅速增长和后期的缓慢下降过程,从60年代初的84.75万头至70年代末的287.55万头,到2005年的149万头。 4.黄河源区的年平均气温近50年来总体呈上升趋势,各县的平均增温情况不同,玛多县的温度增速平均达0.0321℃/年,玛沁县的温度增速最小,为0.0216℃/年,甘德和达日两县的平均温度增速相近居于前两者之间,分别是0.0266℃/年和0.0276℃/年。源区4县多年降水量无明显的变化趋势,均在多年平均值上下波动。源区的蒸发量总体上没有明显的增加或降低的趋势,但20世纪70年代末、80年代初,源区四县的蒸发量呈现了下降趋势。1984年后各县的蒸发量开呈现上升的趋势。平均风速在20世纪80年代前波动上升,80年代后呈现波动下降态势。玛多、达日和玛沁的日照时数呈现线性增加趋势,以玛多县的最为明显,甘德县的日照时数无明显的变化趋势。 5.主成分分析提取的各县主成分累积贡献率均在75%以上,人为因子均在第一主成分内。对黄河源区四县的合并数据分析,共提取了3个主成分,累积贡献率达到了83.21%,其中第一主成分贡献率达43.08%,主要因子载荷的大小顺序依次为人口数量>牲畜总数>国内生产总值>平均风速。第二主成分的贡献率为22.74%主要影响因子是年降水量和年蒸发量。第三主成分贡献率之和为17.40%,显著影响因子是年均气温和日照时数。表明人为因素是源区植被退化的主导因素,超载过牧直接了导致草地退化。 通过多元回归分析得到了反映各县及整个地区退化与驱动因子之间关系的多元线性方程,但每个因子被提取的频率不同,所提取各因子对退化面积增加的相对重要性不同。在5个方程中,人为因子被提取了10次,而自然因子只被提取了6次;人口数量在玛沁、甘德、达日和整个地区的4个方程中均处于最大的位置,牲畜数量在玛多县是最重要的因子,人为因素均被证明是各地草地退化的最重要因子。合并数据的四元线性回归方程中有人口数量和牲畜数量两人为因子,年蒸发量和年平均风速两个自然因子。入选变量对退化面积增加的相对重要性大小顺序是人口数量(0.7958)> 平均蒸发量(0.1694)>牲畜数量(0.0874)>平均风速(0.0792)。 6.原始封育草甸的土壤含水量远高于人工混播草地的,原始高寒草甸涵养水源能力最强,退化草地的水源涵养能力最差(P<0.01);演替时间短的人工草地,在生长旺季由于土壤水分蒸发和植物蒸腾作用会导致土壤水分的下降。封育原生草甸、人工混播草地、半人工补播草地和退化草地群落的土壤容重、不同功能群地上部分的含碳量和全氮含量,以及土壤有机碳和全氮含量因演替时间长短不同而异。土壤根系含碳量也受演替时间长短影响,但含氮量的规律比较明显,以退化草地的最高,原生封育草地的最低。人工混播草地土壤有机碳和全氮比原生封育草地有明显降低(P<0.01)。 7. 制定科学的放牧制度,控制牲畜数量,减轻对草地的长期压力,草地以休养生息的机会,是促进轻度退化草地植被自然恢复的最有效途径;人工补播是中度退化草地生态恢复的主要措施;人工草地建植是重度和极度退化草地生态恢复的主要手段;加强草地管理与监测是保障。
Other AbstractThe headwater region of the Yellow River is located at the core area of the Three River Natural Reserve, which is in the central-eastern part of the Qinghai-Tibet plateau. The region serves as a protective eco-screen of both China and Southeast Asia. The ecosystem of the region has been experiencing severe deterioration as results of human disturbance in past decades. Duo to the distinctiveness of the alpine meadow ecosystem and the complexity of interactions among vegetation, soil, climatic and human activities, the research on mechanism and driving force of the alpine meadow degradation in the region is still not enough. The objectives of the study were to: 1) reveal the responses of vegetation and soil to degradation by investigating community characteristics and soil physic-chemical properties; 2) quantify the contributions of human factors and natural factors and the relationship among the factors by analyzing the variation of each factor in past decades; 3) understand the succession of fenced undegraded meadow, artificial pasture, semi-artificial pasture and degraded meadow, and to 4) provide suggestions for restoration and rehabilitation of the degraded rangeland in the region. The conventional field investigations of ecology study, soil physic-chemical analysis method in lab and reduction of meteorological data were used. By using Principal Component Analysis and Multiple Regression, the ecological process and driving forces of alpine meadow degradation in the region were analyzed. The main conclusions are as follows: 1. There are significant differences in species composition of different degradation stages. The indicative species in severely degraded meadow include Ajania tenuifolia, Lancea tibetica, Polygonum sibiricum, Ranunculus tanguticus and Viola yedoensis,and their indicative values are significantly higher than those of others(P<0.05),and all these plants are fobs. In moderately degraded meadow, Heteropappus altaicus, Kobresia humilis, Gentianella azurea and Ranunculus japonicus are major indicative species. The number of dominant species decreases and their dominances decline. The similarities among communities reduced. The richness, diversity and evenness indices decline with the aggravation of degradation, and all of them follow the order lightly degraded > moderately degraded > severely degraded. The relationships between meadow quality cover index (MQCI) and diversity, evenness can be best presented by quadratic equations. The diversity and evenness are low when the MQCIs are less than 15% and greater than 45%, and reach to high when MQCI in the middle of 15% and 45%. The relationship between MQCI and richness index can be best presented by a cubic equation, and no apparent trend can be found when MQCI is greater than 20%. 2. Soil bulk density shows increasing trend with degradation level in different soil layers. The soil water content in lightly degraded meadow is significantly higher than that of severely degraded meadow. Soil organic carbon content (0~30cm) is in the order of lightly degraded > moderately degraded > severely degraded. There are significant organic carbon content differences between lightly degraded and moderately degraded, and severely degraded in the top 10cm soil. Soil total nitrogen content has similar pattern with organic carbon. There is no obvious C/N ratio difference among soil layers and degradation levels. 3. The population in the headwater region presents a linear increase and increased by 70,000. The annual population increase rate is 2.05%, equals to 1350 person per year. The livestock number increased sharply during 1960’s and 1970’s (from 84.75×104 to 287.55×104 ), and has been declining since 1980’s. The number was 149×104in 2005. 4. The annual mean air temperature exhibited an increasing trend in the region. The increasing rate in Maduo, Maqin, Gande and Dari was 0.0321℃/a,0.0216℃/a,0.0266℃/a and 0.0276℃/a, respectively. Both precipitation and evaporation had no obvious trend in past 50 years in the study area. However, evaporation showed a declining at the end of 1970’s and early 1980’s, and a increasing since 1984. The annual wind speed presented uptrend before 1980’s and downward trend since then. Sunshine hours in Maduo, Maqin, and Dari exhibited linear increasing trend, but that of Gande has no trend. 5. All accumulative proportion of extractred principle component was greater than 75% and all human factors in different counties were extracted to the first principle component. Three principle components were extracted from the pooled data of the Maduo, Maqin, Gande and Dari and the accumulative proportion was 83.21%. The contribution of the first principle component was 43.08% and the main affecting factors were in the order of population > livestock number > GDP > mean wind velocity. The contribution of the second principle component was 22.74% and annual precipitation and annual evaporation were the significant factors. Average annual temperature and sunshine hour were in the third principle component, which accounts for 17.40% of the total contribution. Human activities are the leading causes of vegetation degradation in the region and overgrazing directly resulted in the consequences. The relationship between degradation and influential factors for each county can be reflected by a multiple regression equation. Both the relative importance of each factor to the increase of degradation area and the times of each factor be extracted vary with different counties. Human factors were extracted for 10 times and natural factors were 6 times in 5 equations. Population and livestock number are the most important factors that drive the meadow degradation. There are four factors that were selected in the multiple regresson equation of the pooled data of the Maduo, Maqin, Gande and Dari, and their relative importance in the order of population(0.7958) > annual evaporation (0.1694)> livestock number(0.0874) > mean wind velocity (0.0792)。 6. Soil water content in fenced undegraded meadow is greater than that of artificial pasture. Water holding capacity in degraded meadow is significant lower than that of undegraded meadow. Because of evaporation, transpiration and need of plants growth, the soil water content in short-time successive artificial pasture is significant lower than other’s. Soil bulk density, concentrations of carbon and nitrogen in above-ground fraction of different functional groups, soil organic carbon and total nitrogen change with succession duration. Carbon concentration in roots has similar pattern with that of above-ground. Nitrogen concentration in roots of degraded meadow is significantly higher than that of enclosed meadow. Both soil organic carbon and total nitrogen in artificial pasture are significantly lower than those of fenced undegraded meadow. 7. The most effective way for lightly degraded alpine meadow is to reduce livestock number and to rest the rangeland. Seeding moderately degraded meadow is a good way of restoration. Establishment of artificial vegetation is recommended for severely degraded meadow. Only enhance grassland managemen and monitoring can these measures be guanranteed
Pages139
Language中文
Document Type学位论文
Identifierhttp://210.75.249.4/handle/363003/3218
Collection中国科学院西北高原生物研究所
Recommended Citation
GB/T 7714
乔有明. 黄河源区高寒草甸退化的生态学过程及其驱动力分析[D]. 西北高原生物研究所. 中国科学院西北高原生物研究所,2009.
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