西藏北部高寒草甸土壤线虫群落特征研究

发布时间：2018-07-04 11:24

本文选题：土壤线虫 + 群落结构　；参考：《南京农业大学》2015年博士论文

【摘要】：土壤线虫广布于各种类型的土壤中,在维持土壤生态系统的稳定性、促进物质循环和能量流动等方面发挥着重要的作用,而且还是理想的环境指示生物,因此,近些年来,有关土壤线虫群落结构特征及影响因素的研究受到重视。然而,到目前为止,有关西藏高原土壤线虫方面的研究极少。在西藏北部地区,草地是面积最大,也是最重要的生态系统类型,其中,高寒草甸类草地广泛分布,具有典型的区域代表性。为了解西藏高原高寒环境下植被对土壤线虫群落的影响,本研究选择的研究区域位于西藏北部那曲地区那曲县(N31 °31′38"～N31°32′02,E 92°04′03″～E92° 04′16″海拔4534 m～4567 m)。在研究区域内选取有代表性的植物群落,分别为委陵菜、高山嵩草、藏北离草为主要建群种的高寒草甸。通过定期和土壤分层采样,应用线虫群落个体密度、种类组成、营养结构及其特征指数,以及生物多样性指数等,分析土壤线虫群落的时空变化特征。此外,选择已实施围栏封育措施3年的高山嵩草型高寒草甸,分别在围栏内外设置样地,通过分析土壤线虫群落及土壤理化性质,在了解线虫群落变化及其与土壤环境之间关系的基础上,探讨自由放牧对藏北高寒草甸的影响,以及围封对高寒草甸恢复的作用,以期为退化草地恢复以及西藏畜牧业发展提供理论依据。主要研究结果如下:(1)从西藏北部高寒草甸3种植物群落的土壤样本中分离得到土壤线虫33038条,分属于2纲6目51科93属,个体密度23～4 109条100g-1干土。(2)土壤线虫个体密度以委陵菜植物群落最低,其次是藏北嵩草植物群落,高山嵩草植物群落最高;3种植物群落的土壤线虫个体密度均在返青期最大,盛长期次之，枯草期最小,季节间差异显著。土壤线虫类群属数则以委陵菜群落为最高,高山嵩草群落次之,藏北嵩草群落最低,季节变化趋势与个体密度一致。(3)委陵菜群落的土壤线虫多样性及丰富度均最高,高山嵩草群落次之,藏北嵩草群落最低;藏北嵩草群落的均匀度和优势度均明显高于其它两种植物群落。一般地,从土壤表层往下,多样性指数(H′)、丰富度指数(SR)随着土层加深而减小,而均匀度指数(J′)、优势度指数(λ)则随之增大,这种趋势在高山嵩草群落和藏北嵩草群落比较明显。(4)3种植物群落之间,土壤线虫营养类群组成及分布特征差异显著。植食性线虫和食细菌线虫是研究区域的主要营养类群。不同植物群落间,植食性线虫和杂食/捕食性线虫的相对多度差异显著。土壤线虫生活策略以r-对策为主,表现为cp2线虫类群在3种植物群落均为优势类群。通过食真菌线虫和食细菌线虫的比例(F/B)及线虫通道指数(NCR),说明3种植物群落的土壤有机质均以细菌分解途径为主。在指示高寒草甸所受干扰方面,cp5对于来自于放牧等干扰表现的较为敏感,而PPI/MI的灵敏度较低。(5)在植物群落的盛长期,土壤含水量、pH、电导率与土壤线虫个体密度均显著相关,食真菌性线虫明显受到土壤pH的影响,食细菌性线虫仅在返青期受到pH的影响,杂食/捕食性线虫在枯草期的个体密度与土壤含水量显著相关。从cp1到cp5,线虫各功能类群与土壤性质之间的关系逐渐增强,cp2和cp4在返青期受到土壤pH的影响;cp1及cp3类群跟土壤理化性质间没有表现出显著的相关性;cp5类群在返青期和枯草期跟土壤含水量显著相关,在盛长期则跟土壤pH间极显著相关。(6)委陵菜群落一般被看做是高山嵩草型高寒草句发生严重退化的形式。高山嵩草型高寒草甸发生退化会导致土壤线虫个体密度下降,虽然线虫的类群属数未发生明显变化,但线虫群落种类构成却发生了较大的变化。退化还导致植食性线虫的个体密度增加,以及cp3、cp5类群在群落中所占的比重增大等。因此,土壤线虫群落对高山嵩草高寒草甸发生退化有明显的响应。(7)短期围封提高了土壤线虫群落的物种多样性和丰富度,优势类群种类及其个体数量均明显增加。(8)围封使土壤线虫群落的营养结构发生变化。自由放牧样地土壤线虫群落不同营养类群的个体密度:植食性线虫食细菌性线虫食真菌性线虫杂食/捕食性线虫,而围封样地则为:食真菌性线虫植食性线虫占线虫食细菌性线虫杂食/捕食性线虫,但2样地间各营养类群个体密度的差异并未达到显著水平。围封降低了植食性线虫在群落中所占的比重,使高寒草甸生态系统向更加稳定的方向发展。(9)围封样地的多样性指数H′、丰富度SR均高于放牧样地;围封样地的优势度指数λ明显低于放牧样地;WI指数反映出在放牧强度最大的植被盛长期(8月)高寒草甸的健康程度最差,若进一步过载会将导致高寒草甸退化。本研究通过对西藏北部地区高寒草句土壤线虫群落与植物群落之间的关系进行研究,提出了藏北高寒草甸土壤线虫个体密度、属数、时空分布特点等方面的调查结果,揭示出青藏高原特殊气候条件下高寒草甸土壤线虫群落结构的基本特征。通过研究自由放牧对高寒草甸土壤线虫群落的影响,以及土壤线虫群落对围封措施的响应情况,获得了围封措施有利于藏北高寒草甸生态系统的正向演替,使之向更稳定的方向发展的结论,为当地畜牧业发展提供了理论依据。
[Abstract]:Soil nematodes are widely distributed in various types of soil, playing an important role in maintaining the stability of the soil ecosystem, promoting material circulation and energy flow, and is an ideal environmental indicator. Therefore, in recent years, the research on the structure characteristics and influencing factors of soil nematode community has been paid much attention. So far, there are few studies on soil nematodes in the Tibet plateau. In northern Tibet, the grassland is the largest and most important ecosystem type. Among them, the alpine meadow is widely distributed and has typical regional representation. In order to understand the effect of vegetation on the soil nematode community in the alpine environment of Tibet Plateau, this study has been studied. The selected research area is located in Nagqu County Nagqu county (N31 31 '38 "~ N31 degree 32' 02, E 92 degree 04 '03" to E92 degree 04' 16 "altitude 4534 m ~ 4567 m). In the study area, the representative plant communities are selected as the alpine meadow, which are the main group species of Potentilla, Alpine Kobresia and North Tibet. By stratified sampling, the spatial and temporal characteristics of soil nematode communities were analyzed by the individual density, species composition, nutritional structure, characteristics index and biodiversity index of nematode communities. In addition, the alpine kobrex Alpine alpine meadow, which had been enforced for 3 years, was set up inside and outside the fence, and the soil line was analyzed. On the basis of understanding the change of the nematode community and the relationship between the nematode community and its soil environment, the influence of free grazing on the alpine meadow in northern Tibet, and the effect of enclosure on the alpine meadow restoration, were discussed in order to provide a theoretical basis for the restoration of degraded grassland and the development of Tibet animal husbandry. The main results are as follows: (1) 33038 species of soil nematode were isolated from the soil samples of 3 plant communities in the northern alpine meadow of Tibet. It was divided into 2 classes, 6 orders, 51 families and 93 genera, and the individual density was 23~4109 100g-1 dry soil. (2) the individual density of the soil nematode was the lowest in the plant community of Potentilla, followed by the northern Kobresia Kobresia plant community, and 3 species of plant communities. The individual density of soil nematode was the largest in the period of returning to green. The minimum in the period of withered grass was the lowest. The number of soil nematode groups was the highest, the highest in the Alpine Kobresia community, the lowest in the northern Kobresia kobreus, and the seasonal trend was the same as the individual density. (3) the diversity and richness of the soil nematode in the community of Potentilla Potentilla The degree is the highest and the Alpine Kobresia community is the lowest. The evenness and dominance of Kobresia kobrei are obviously higher than those of the other two plant communities. Generally, the diversity index (H ') and the richness index (SR) decrease with the depth of the soil layer, and the evenness index (J'), dominance index ([lambda) (lambda) Ze Suizhi This trend is more obvious in the Alpine Kobresia and Kobresia kobreus communities. (4) there are significant differences in the composition and distribution of soil nematode nutrient groups among the 3 plant communities. The soil nematode life strategy was dominated by the r- strategy, which showed that the CP2 nematode group was the dominant group in 3 plant communities. Through the proportion of fungi nematodes and bacterial nematodes (F/B) and the nematode channel index (NCR), the soil organic matter in the 3 plant communities was dominated by the bacterial decomposition pathway. In the area of interference, cp5 is more sensitive to the interference from grazing, and the sensitivity of PPI/MI is low. (5) in the long term of the plant community, soil water content, pH, electrical conductivity and soil nematode individual density are significantly correlated, and fungus eating nematodes are obviously affected by soil pH, and the bacterial nematode is only affected by pH during the green period. The individual density of omnivorous / predatory nematodes was significantly correlated with soil moisture content during the period of withered grass. From CP1 to cp5, the relationship between the functional groups of nematodes and soil properties gradually increased, and CP2 and CP4 were affected by the soil pH during the return period; there was no significant correlation between CP1 and CP3 groups and the physical and chemical properties of soil; cp5 groups were in the green period. There is a significant correlation between the soil moisture content and the soil water content of the dead grass period. (6) (6) the community of Potentilla is generally regarded as a form of severe degeneration of Alpine Kobresia humus. The degradation of Alpine Kobresia alpine meadow will lead to the decrease of individual density of soil nematode, although the number of nematode groups does not occur. The species composition of the nematode community changed significantly, but the degeneration also resulted in the increase of the individual density of the herbivorous nematode, and the increase in the proportion of CP3 and cp5 groups in the community. Therefore, the soil nematode community had a significant response to the degradation of Alpine Kobresia humilis meadow. (7) the short-term enclosure improved the soil nematode community. Species diversity and richness, dominant group species and their individual numbers increased significantly. (8) the nutrient structure of soil nematode communities was changed by enclosure. The individual density of different nutrient groups in soil nematode communities in free grazing plots: herbivorous nematode eating nematode omnivores / predatory nematodes, and enclosure samples The site was as follows: fungal nematode phytophagous nematodes were dominated by bacterial nematode omnivus / predator nematode, but the individual density differences between the 2 types of vegetative groups did not reach a significant level. The enclosure decreased the proportion of herbivorous nematodes in the community and made the alpine meadow ecological system develop in a more stable direction. (9) enclosed plots The diversity index H 'and richness SR were higher than grazing plots; the dominance index of enclosure plots was significantly lower than that of grazing plots; the WI index reflected the worst degree of health in the alpine meadow with the largest grazing intensity in the long term (August), if further overload would result in the degradation of the alpine meadow. This study passed to the northern region of Tibet high The relationship between the soil nematode community and the plant community was studied. The results of the investigation on the individual density, the number and the spatial and temporal distribution of the soil nematode in the northern Tibetan alpine meadow revealed the basic characteristics of the knot structure of the soil nematode community in the alpine meadow soil under the special climate of the Qinghai Tibet Plateau. The influence of the nematode community in the meadow soil and the response of the soil nematode community to the enclosure measures, the enclosure measures have been obtained for the positive succession of the alpine meadow ecosystem in the north of Tibet, and the conclusion that it develops in a more stable direction provides a theoretical basis for the development of the local animal husbandry.
【学位授予单位】：南京农业大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：S812.2

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