Knowledge Resource Center for Ecological Environment in Arid Area
| 放牧对内蒙古针茅草原物种多样性和生物量的影响——尺度依赖性、格局和机制 | |
| 其他题名 | Effects of grazing on species diversity and biomass of Stipa steppes in Inner Mongolia —— scale dependence, patterns and mechanisms |
| 王扬 | |
| 出版年 | 2016 |
| 学位类型 | 博士 |
| 导师 | 白永飞 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 有研究表明，长期过度放牧是导致我国北方温带草原生物多样性和生态系统功能（如，地上、地下生物量）降低的主要原因。然而，草原生态系统的物种多样性和生物量的变化还受群落类型、气候、土壤、空间尺度等因素的影响，放牧与这些因子之间可能存在着复杂的交互作用，共同决定了物种多样性和生物量对放牧的响应方式及变化轨迹。在局地尺度上放牧引起的物种多样性降低在不同群落间存在着差异，从群落结构和利用历史角度分析差异产生的原因，有助于认识放牧对草原植物多样性的影响机制，进而为草原生物多样性的保护提供理论依据。另外，从区域水平上评估放牧对物种多样性和生态系统功能的影响，以及放牧与气候和土壤因素之间的交互作用，有助于揭示在当前土地利用状况下，我国北方草原物种多样性和生态系统功能的变化规律，为退化草原的恢复与合理利用提供科学依据。在局地尺度上，本研究依托中国科学院内蒙古草原生态系统定位研究站在锡林河流域设置的六个不同围封年限的成对禁牧和放牧对照样地，采用种-面积曲线模型分解的方法，结合物种功能性状分析，研究了不同群落中放牧引起物种多样性降低的尺度依赖性及其机制。在区域尺度上，以内蒙古草原四类地带性分布的针茅草原(贝加尔针茅草原、大针茅草原、克氏针茅草原和小针茅草原)为研究对象，基于四类针茅草原226个样地的野外调查数据，采用冗余分析(Redundancy Analysis, RDA)和方差分解的方法，系统地分析了放牧、气候（年平均降水、年平均气温、≥10℃积温、干燥度和相对湿度）和土壤（容重和pH）因素对不同针茅草原物种多样性、地上和地下生物量及其分配的影响。取得的主要研究结果和结论如下：1. 沿不同的空间尺度（取样面积），长期过度放牧均显著地降低了草原群落的物种多样性，且多样性降低的程度与放牧时间的长短有关，放牧时间越长，物种多样性降低的程度就越高(p=0.0372, R2=0.70)。物种多样性的减少主要是由稀有种的数量变化引起，而稀有种的减少除了受其自身较少的多度影响外，还与植物的功能性状有关。但不同功能性状在引起物种多样性降低中所起的作用不同，且其作用随群落类型的不同而不同。放牧引起的物种多样性降低具有显著的尺度依赖性。通过种-面积曲线的模型分解发现，放牧主要通过引起物种数的降低和改变物种的多度分布，影响种-面积曲线的斜率，进而影响群落物种多样性变化的尺度依赖性。物种种库的大小可能是引起不同群落间尺度依赖性差异的主要原因(p=0.0326, R2=0.72)。2. 内蒙古四类针茅草原的物种多样性存在着显著的差异，从草甸草原（贝加尔针茅草原）到典型草原（克氏针茅草原、大针茅草原）和荒漠草原（小针茅草原），物种多样性逐渐降低。气候因素，特别是降水量，是影响针茅草原物种多样性大尺度空间分布格局的主要因子，年平均降水量、干燥度和相对湿度分别解释了物种多样性变异的19%、21%和22%。总体上，放牧降低了草原群落的物种多样性，但对典型草原物种多样性的影响要大于草甸草原和荒漠草原。大针茅草原中，放牧与气候因子之间存在显著的交互作用。3. 降水量是影响群落地上生物量的主要气候因子。从贝加尔针茅草原到大针茅草原、克氏针茅草原、小针茅草原，群落地上生物量逐渐降低，分别为156.25±11.38、127.50±8.38、95.02±6.43和46.16±4.04 g m-2。同地上生物量相比，贝加尔针茅草原、大针茅草原和克氏针茅草原的地下生物量主要受≥10℃积温的影响，而小针茅荒漠草原的地下生物量主要受水分的影响。放牧显著降低了针茅草原的地上生物量，但放牧对地上生物量的影响与气候因子之间存在显著的交互作用，即放牧强度也受到气候因素的制约。各类针茅草原的地下生物量在不同利用强度之间无显著的差异(p>0.1)。土壤因子对群落地上和地下生物量的影响与群落类型有关，且通过与气候因子的交互作用共同影响群落的地上和地下生物量。气候和放牧是影响针茅草原群落地下/地上生物量比的主要因素。随着干燥度的增加，从贝加尔针茅草原到大针茅草原、克氏针茅草原和小针茅草原，群落地下/地上生物量比逐渐增加，分别为8.63±1.66、11.28±2.18、14.31±1.79和17.69±1.66。同时，随着放牧强度的增加，各类针茅草原的地下/地上生物量比呈增加的趋势，尤其是典型草原中的大针茅草原(p=0.0172)和克氏针茅草原(p<0.0001)。 |
| 英文摘要 | Many studies demonstrate that long-term overgrazing has resulted in widespread declines in biodiversity and ecosystem functioning (e.g. above- and below-ground biomass) in arid and semiarid grasslands in northern China. However, it remains less clear that how grazing effects on biodiversity and ecosystem functionning are influenced by vegetation type, climate, soil environment, spatial scale, and particularly the complex interactions between grazing and these biotic and abiotic factors. At local scales, grazing effects on species diversity have been proven to be often context- and scale-dependent. Therefore, it is critical to understand how grazing effects on plant diversity are mediated by changes in community structure and land-use history and to identify mechanisms underlying the scale-dependent changes in species diversity. At regional scales, it is of fundamental importance to evaluate how grazing, climate factors, and soil properties interactively affect species diversity and ecosystem function under the current grassland use regimes. These studies will have important implications for restoring biodiversity and ecosystem functioning and for improving grassland management practices in northern China.At local scales, six paired ungrazed and grazed plots at the Inner Mongolia Grassland Ecosystem Research Station (IMGERS), the Chinese Academy of Sciences, were chosen to examine the scale-dependence of grazing-induced species loss and the underpining mechanisms. Species-area relationship (SAR) decomposition approaches and plant functional traits analysis were used to assess the relative contribution of four potential mechanisms, including changes in overall species richness, total number of individuals, species abundance distribution, and species aggregation. At large scales, the effects of grazing and interactions of grazing with other biotic and abiotic factors on species richness and biomass production were evaluated based on data from 226 field sites of four Stipa steppes (S. baicalensis, S. grandis, S. krylovii and S. klemenzii) across the Inner Mongolia grassland. Redundancy analysis and variance partitioning approaches were used to examine how grazing, climate (mean annual precipitation, mean annual temperature, ≥10℃ accumulated temperature, aridity, and relative humidity) and soil environment (bulk density and pH) interactively influence species diversity and biomass production across the four Stipa steppes in Inner Mongolia. Key findings are summarized as following:1. Long-term extensive grazing significantly decreased species diversity at all spatial scales. The magnitude of grazing-induced reduction in species richness increased over time (p=0.0372, R2=0.70). The reduction in species richness was mainly caused by the loss of grazing-sensitive rare species, triggered by both abundance and functional based mechanisms. Plant functional traits differed in their effects on species loss and the effective traits often vary among communities. The grazing-induced reduction in species richness was scale-dependent across all communities. Results from SAR decomposition model showed that decrease in overall species richness and changes in species abundance distribution were two dominant mechanisms controlling the sacle-dependent responses of speciess richness to grazing. Species pool size in ungrazed community had a positive effect on sacle-dependent responses of speciess richness to grazing (p=0.0326, R2=0.72).2. Plant species diversity differed substantially among different vegetation types in the Inner Monglia grassland. Plant diversity decreased from meadow steppe (S. baicalensis steppe) to typical steppe (S. grandis and S. krylovii steppes) and to desert steppe (S. klemenzii steppe). Climate factors, particularly precipitation, was the key driver controlling large-scale patterns of plant species diversity of Stipa steppes across the Inner Mongolia grassland. Mean annual precipitation, aridity and relative humidity respectively explained 19%, 21% and 22% of the total variance in species diversity. In general, grazing decreased species diversity across different steppes, especially in the typical steppe communities. The interactive effects of grazing with climate factors on species diversity were also significant for typical steppe (S. grandis steppe, p=0.0394).3. Aboveground biomass decreased from S. baicalensis steppe (156.25±11.38 g m-2) to S. grandis (127.50±8.38 g m-2), S. krylovii steppe (95.02±6.43 g m-2) and S. klemenzii steppe (46.16±4.04 g m-2), and was driven mainly by mean annual precipitation. However, the ≥10℃ accumulated temperature was found to be a key climate factor controlling the regional-scale patterns of belowground biomass of S. baicalensis, S. grandis and S. krylovii steppes, except for S. klemenzii steppe, which was primarily controlled by precipitation. Grazing significantly decreased aboveground biomass across all Stipa steppes and the effects of grazing with climate factors were also significantly for most Stipa steppes. No significant effect of grazing on belowground biomass was found among the four Stipa steppes (p>0.05). The effects of soil factors on biomass production were context-dependent and interacted with climate factors. At the regional scale, climate factors and grazing had significant effects on belowground to aboveground biomass ratio. With increasing aridity, the belowground to aboveground biomass ratio increased from S. baicalensis steppe to S. Grandis steppe, S. krylovii steppe, and to S. klemenzii steppe. Grazing increased belowground to aboveground biomass ratio in all Stipa steppes, especially for S. grandis steppe (p=0.0172) and S. krylovii steppe (p<0.0001). |
| 中文关键词 | 种-面积曲线 ; 种库 ; 物种多度分布 ; 植物功能性状 ; 地下/地上生物量比 |
| 英文关键词 | species-area curve species pool species abundance distribution plant functional traits belowground to aboveground biomass ratio |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 生态学 |
| 来源机构 | 中国科学院植物研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287820 |
| 推荐引用方式 GB/T 7714 | 王扬. 放牧对内蒙古针茅草原物种多样性和生物量的影响——尺度依赖性、格局和机制[D]. 中国科学院大学,2016. |
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