江河源区高寒草甸土地退化及恢复重建对植被及土壤种子库的影响

NWIPB OpenIR

	江河源区高寒草甸土地退化及恢复重建对植被及土壤种子库的影响
其他题名	The effects of soil degradation and rehabilitation on vegetation and soil seed bank of alpine meadow in the source region of Yangtze and Yellow Rivers
	李世雄
学位类型	博士
导师	王启基
	2009-06-02
学位授予单位	中国科学院西北高原生物研究所
学位授予地点	西北高原生物研究所
关键词	江河源区高寒草甸土地退化植被特征土壤种子库土壤c n 恢复与重建
摘要	本研究以江河源区退化高寒草甸为研究对象, 综合运用植物生态学、恢复生态学、土壤学等多学科理论，通过野外调查和室内试验及数据统计分析,研究了土地退化和恢复重建对高寒草甸植物群落特征、土壤种子库、土壤理化性状及碳、氮储量的影响，为退化高寒草甸恢复提供基础资料。研究主要结果如下：江河源区高寒草甸呈全面退化的趋势。超载过牧不仅使草地初级生产力下降，而且使草场质量变劣，优良牧草减少，毒杂草增加。由于优势植物资源位的变化，使植物群落结构和外貌发生变化，草场植被向退化演替方向进行。随着退化程度的加剧，以克隆繁殖为主的优势种莎草类植物，其优势度明显降低，尤其在退化严重的“黑土滩”上几乎消失。轻度退化高寒草甸实施围栏封育和施肥3年后，植被群落物种丰富度和多样性提高，地上生物量显著提高，优良牧草的比例增加。不同演替阶段植物群落的物种丰富度、多样性指数、均匀度指数依次为轻度退化草地>中度退化草地>重度退化草地。植物群落地上生物量及地下生物量也为轻度退化草地>中度退化草地>重度退化草地。在极度退化的高寒草甸建植人工草地可明显的增加植被覆盖，显著地提高地上生物量。高寒草甸土地退化及恢复重建处理土壤种子库物种组成较小，其中轻度退化草地封育施肥处理在返青最高，有23种；混播草地植被种子成熟前最低，仅为5种。土壤种子库的大小在6284.5±2910.3-720.0±256.8粒/m2之间。高寒草甸各个处理土壤种子库在三个取样时间（植被返青前、种子成熟前和枯黄期）均有种子萌发，种子萌发数量为返青前>枯黄期>种子成熟期前。高寒草甸各个处理土壤种子库密度在0-5cm 土层显著高于5-10cm 层，其中在返青期前和枯黄期各处理0-5cm 层均显著高于5-10cm 层。种子密度在垂直分布上呈现出由表层土壤向深层逐层减少的变化规律。封育和施肥措施提高了轻度退化草地的种子库Marga1ef 丰富度和Shannon-wienner指数。高寒草甸土地退化和恢复重建各处理土壤种子库与地上植被的相似性均较低，平均为42.25%。高寒草甸典型类型莎草类和禾草类在轻度封育、轻度封育施肥、轻度退化草地及中度退化草地土壤种子库中出现，而在重度和极重度退化草地中基本消失。土壤种子库为轻、中度退化高寒草甸经过围栏封育、施肥等措施在短时间内得到恢复提供了基础。封育与施肥措施可显著提高轻度退化草地0-20cm 层土壤碳，氮浓度及储量。退化草地碳氮浓度依次为轻度草地>中度草地>重度草地，但差异不显著；恢复重建后人工草地处理高于对照（极重度退化草地‘黑土滩’）。0-20cm 层土壤碳储量轻度和中度退化草地显著高于重度退化草地；人工恢复处理中，混播草地显著高于单播草地，二者均显著高于对照。0-20cm 层土壤氮储量轻度退化>中度退化草地>重度退化草地，但差异不显著（p>0.05）；两种人工恢复处理碳氮储量均显著高于对照。随着土层的加深，土壤碳氮浓度及储量逐渐减小。相对于轻度退化封育施肥处理，高寒草甸由于土地退化而造成的土壤（0-20cm层）碳、氮丢失量分别为6144.0 g m-2和308.8 g m-2，即高寒草甸土地退化导致0-20 cm土壤层中56.3%的土壤有机碳和29.9%的氮流失。与天然原生嵩草草甸相比较，人工恢复重建草地的土壤物理化学特性的改善不是特别明显，但与未恢复状态相比较，草地恢复和重建可以增加生物量及地表覆盖度，部分的改善土壤理化学特性。根据本研究结果结合以往的研究提出了退化高寒草甸的综合治理模式。
其他摘要	The effects of soil degradation and restoration, as well as rehabilitation on vegetation, soil seed bank of alpine meadow in source region of Yangtze and Yellow Rivers were studied by investigating vegetation and soil seed bank. Soil carbon and nitrogen of the different alpine meadow were also evaluated. The experiment was conducted at center of Qinghai-Tibetan Plateau with three degraded alpine meadows: the lightly, moderate and severely degraded lands (LD, MD and SD) and two restoration treatments of the lightly degraded land, i.e. the lightly degraded land with enclosure (LDE) and the lightly degraded land with enclosure and fertilization (LDEF), as well as three rehabilitation treatments in overly degraded land: single seeds treatment (SSF), mixed seeds treatment (MSF) and control (CK). The results showed as follows: Alpine meadow showed a direction of serious grassland degradation. Overgrazing has resulted in a serious grassland degradation characterized by reduced above-ground plant biomass, loss of the hard turf layer leading to exposure of subsoil and an increase in the prevalence of toxic plants. With the picking up of degradation extent, the important value of the dominant species sedges which reproduced by clone, were drop in different degraded lands, especially disappeared in the overly degraded land. The species numbers and diversity of plant, as well as above-ground biomass in LD were increased with the measures of enclosure and fertilization after 3 years. The species richness, diversity (Shannon-Wiener index) and evenness (Pielou index), as well as aboveground and root biomass ranked as LD>MD>SD. The above-ground biomass and plant cover were largely increased in severely degraded alpine meadow under the rehabilitation of vegetation measure. The compositions of soil seed bank in all of investigated alpine meadow were small. 23 species which were the largest species number in alpine meadow were found in LDEF treatment, and only 5 species in MS treatment. The size of soil seed bank of alpine meadow was altered from 6284.5±2910.3 to 720.0±256.8 seeds per square meter. Seeds were found in soil seed bank of alpine meadow in all three sample time: i.e. before green up stage, before seed maturity stage and withering stage. The seeds number ranked as before green up stage>withering stage> before seed maturity stage. Seeds density of soil seed bank of alpine meadow in 0-5 cm soil depth were larger than in 5-10 cm in all treatments and the significant difference of seeds number between 0-5 cm to 5-10 cm soil depth were found in soil seed bank sampled before green up stage and withering stage. Seeds number of soil seed bank declined form top soil layer to deeper layer. Marga1ef richness Shannon-wienner index of soil seed bank in LD were improved with enclosure and fertilization measures. Similarities of soil seed bank and vegetation were low in all alpine meadow treatments, and the average coefficient of similarity was 42.25%. The typical species such as sedge and grass were found in LDE, LDEF, LD and MD, and loosed in SD and CK. Soil seed bank provide a germplasm base for restoration of LD and MD in a short time with enclosure and fertilization measures. The carbon and nitrogen concentration and content in 0-20 cm soil layer were improved in LD with enclosure and fertilization measures. The carbon and nitrogen concentration in degraded land ranked as LD>MD>SD. The carbon and nitrogen concentration in 0-20 cm soil layer was higher in two the rehabilitation treatments than that in CK. The carbon content in 0-20 cm soil layer was higher in LD and MD than that in SD. In rehabilitation treatments, the carbon content in 0-20 cm soil layer was highest in MS and lowest in CK. The nitrogen content in 0-20 cm soil layer in degraded land ranked as LD>MD>SD. The nitrogen content in 0-20 cm soil layer was higher in two the rehabilitation treatments than that in CK. The carbon and nitrogen concentration and content declined form top soil layer to deeper layer. The loss of total carbon and nitrogen content of unit area of soil depths 0-20 cm after degradation from LDEF to SD were 6144.0 g m-2 and 308.8 g m-2, i.e. 56.3% and 29.9% of the total carbon and nitrogen content of unit area of soil depths 0-20 cm in LDEF were lost, respectively. No significant improvements of the physical and chemical properties of soil were found in the overly degraded land compared to natural alpine meadow with rehabilitation measure, while the above-ground biomass and plant cover of the overly degraded land were increased with rehabilitation measure. The synthetical measures of restoration and rehabilitation for degraded alpine meadow were suggested.
页数	94
语种	中文
文献类型	学位论文
条目标识符	http://210.75.249.4/handle/363003/3088
专题	中国科学院西北高原生物研究所
推荐引用方式 GB/T 7714	李世雄. 江河源区高寒草甸土地退化及恢复重建对植被及土壤种子库的影响[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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