【作者】 赵陆强；

【导师】 王刚；

【作者基本信息】 兰州大学 ， 生态学， 2011， 博士

【摘要】 甘南藏族自治州是甘肃省的重要牧区,主要草地类型为高寒草甸、亚高寒草甸和沼泽化草甸等。近几十年来,由于人类的干扰和自然因素的作用,导致该地区草地退化,主要表现为草地群落的物种多样性和生产力下降,部分草地出现沙化的现象。本文研究了α、β多样性与生产力之间的关系,施肥((NH4)2HPO4)对物种多样性、生产力以及群落物种组成的影响,空间结构和土壤因子对群落物种组成的影响三个部分。研究内容主要围绕以下几个方面的问题：(1)甘南(亚)高寒草甸α、β多样性与生产力之间是否存在特定的关系,在不同的空间尺度上,这些关系如何变化。(2)施肥((NH4)2HPO4)对群落的物种多样性和生产力有何种影响；群落的物种组成发生何种变化；形成诸多变化的机制何在。(3)甘南高寒草甸的植物群落,pH值、全氮、全磷、速效氮、速效磷、土壤有机质、Ca、K、Mg、Na等十种土壤因子,哪些因子与物种组成之间的关系重要；生态位理论和中性理论对物种组成能否做出合理解释。实验的研究对象为甘南高寒草甸(玛曲分站、玛曲县欧拉乡)和亚高寒草甸(合作分站)。通过野外实验和样方调查,结合实验室内土壤养分分析,运用OriginPro 7.5、Canoco 4.5等软件分析,获得主要研究结果如下：(1)在局域空间尺度上,三个站点中仅有两个站点的α多样性与生产力之间表现为线性正相关关系,但扩大空间尺度到景观尺度后,三个站点的α多样性与生产力之间均表现为显著的线性正相关关系。(2)在局域空间尺度上,三个站点中仅有两个站点的β多样性与生产力之间表现为线性负相关关系,但扩大空间尺度到景观尺度后,三个站点的β多样性与生产力之间均表现为显著的线性负相关关系。(3)施肥提高了甘南草地植物群落的生产力,但施肥量与生产力之间并不是线性正相关关系,而是呈钟形曲线关系,随着施肥量的增加,生产力逐渐增加,当施肥量达到43.2gNm-2(48gPm-2)的时候,生产力达到最高,如果再继续加大施肥量,生产力反而会持续地下降。(4)施肥明显降低了甘南草地植物群落的物种多样性,施肥量与物种多样性之间表现为明显的线性负相关关系,施肥量越高,造成物种多样性的损失就越大;而施肥与物种分布的均匀性之间呈钟形曲线关系,随着施肥量的增加,物种分布的均匀性逐渐增加,当施肥量达到14.4gNm-2(16gPm-2)的时候,物种分布的均匀性达到最高,如果再继续加大施肥量,物种分布的均匀性反而会持续地降低。禾本科(Gramineae)和莎草科(Cyperaceae)植物随着施肥量的增加在群落中越来越占优势。(5)坡地0-20 cm土层,影响物种组成的主要土壤因子有：Ca, PI(有效P)、Mg、C(有机质)、Na,显著性顺序为：Ca>P1(有效P)>Mg>C(有机质)>Na；坡地20-40 cm土层,主要因子是：P1(有效P)；坡地40-60 cm土层,主要因子有：P(全P)、Ca、pH,显著性顺序为：P(全P)>Ca>pH;滩地0-20 cm土层,主要因子有：Na、pH、K、P、C、Mg,显著性顺序为：Na>pH>K>P＞C＞Mg;滩地20-40 cm土层,主要因子有：N1(有效氮)、pH,显著性：N1(有效氮)>pH;滩地40-60 cm土层,主要因子有：Na、P(全P),显著性：Na≈P(全P)。无论坡地还是滩地,都是0-20 cm土层的主要土壤因子的数量最多,而各层主要土壤因子的组成也不同。(6)土壤因子对群落物种组成的影响：坡地的土壤因子对群落物种组成的解释程度为14.62%,滩地的土壤因子对群落物种组成的解释程度为18.67%。空间扩散对群落物种组成的影响：坡地的随机扩散作用对群落物种组成的解释程度为13.53%,滩地的随机扩散作用对群落物种组成的解释程度为14.01%。由此可知,生态位理论和中性理论,都能对甘南高寒草甸群落物种组成做出相应的解释。更多还原

【Abstract】 Gannan Tibetan Autonomous Prefecture is an important pastoral area of Gansu Province, which covers alpine meadows, sub-alpine meadows, and marsh meadows. However, in recent decades, due to the impact of human activities and natural disturbance the land of this region has been somewhat degraded, including the decrease of species diversity and productivity, and even the emergence of grassland desertification.The present thesis consists of three parts:the first is about the relationships betweenα,βdiversity and productivity, the second is regarding to the effects of fertilization ((NH4)2HPO4) on species diversity, productivity and community species composition, and the last one is about the impact of spatial structure and soil factors on community species composition. Our main concerns are as following:(1) Whetherα,βdiversity of alpine meadows and sub-alpine meadows in Gannan are related to community productivity? If so, how do these relationships change with spatial scales?(2) How does fertilization affect species diversity, productivity and community composition? What are the underlying mechanisms for these changes?(3) Among ten soil factors, including pH, total N content, total P content, available N content, available P content, organic content, Ca, K, Mg, and Na, which is/are important for community structure? Regarding to the niche theory and neutral theory, which one could better explain the patterns observed?The experiments were conducted on alpine meadows (Maqu and Oula) and sub-alpine meadows (Hezuo). Through field observations and nutrition addition experiments, using the software of OriginPro 7.5 and Canoco 4.5, the results we obtained were as follows:(1) At local spatial scale, two plots of three showed that the relationships between a diversity and productivity were positive at (sub-)alpine meadows. However, when the spatial scale was expanded to the whole landscape, the positive relationships were significant for all three plots.(2) At local spatial scale, two plots of three showed that the relationships between P diversity and productivity were negative in this region. However, when the spatial scale was expanded to the landscape level, the negative relationships were significant for all three plots.(3) Fertilization notably improved the productivity of grassland plant community, but the relationship of fertilizing levels with productivity was bell-curve, not linearly positive. Productivity was highest at the fertilizing level of 43.2gNm-2 (48gPm-2)(4) Fertilization significantly reduced species diversity of communities. The relationship of fertilizing amount with species diversity was clearly negative. The higher the fertilizing amount, the more the species diversity lost. The evenness of species distribution was highest at the fertilizing level of 14.4gNm-2(16gPm-2). Species of Gramineae and Cyperaceae were more and more dominant in communities with the fertilizing amount increasing.(5) On the sloping plots, for the soil layer of 0-20 cm, the main soil factors which affected community species composition were:Ca content, available P content, Mg content, organic content, and Na content, and the order of significance was:Ca content> available P content> Mg content> organic content> Na content; for the layer of 20-40 cm, the main factor was:available P content; for 40-60 cm, the main factors were:total P content, Ca content, and pH, and the order of significance was: total P content> Ca content> pH. On the bottomland of plots, for 0-20 cm soil layer, the main factors were:Na content, pH, K content, total P content, organic content, and Mg content, and the order was:Na content> pH> K content> total P content> organic content> Mg content; for 20-40 cm soil layer, the main factors were:available N content and pH, and the order was:available N content> pH; for 40-60 cm soil layer, the main factors were:Na content and total P content, and the order was:Na content≈total P content. For both sloping and bottomland plots, the number of the main soil factors notably affecting the community structure was maximum in the layer of 0-20 cm.(6) Regarding to the percentage of the variation for community species composition explained by the soil factors, in sloping plots the explained variation was 14.62%, and in bottomland was 18.67%. The percentage of the variation explained by the variables of spatial dispersal in sloping plots was 13.53%, and in bottomland was 14.01%. Based on this, we could conclude that both niche theory and neutral theory could correspondingly explain species composition in community of alpine meadow in Gannan.更多还原