浙江天童常绿阔叶林幼苗的更新机制

发布时间：2018-06-21 00:19

本文选题：扩散限制假说 + Janzen-Connell假说　；参考：《华东师范大学》2016年博士论文

【摘要】：探究群落物种共存机制是现今最重要的生态学问题之一,其中群落幼苗更新过程作为影响群落物种共存的关键过程,更是生态学家研究的重点。因此许多假说都试图去解释群落幼苗的更新过程,其中扩散限制假说、Janzen-Connell效应(以下简称J-C效应)假说以及生境偏好假说作为近年来预测水平较高的三个假说,被认为是影响群落幼苗更新最重要的机制。然而,三种假说独立解释群落幼苗整个更新过程的能力都相对较弱,如何将三者整合起来,最大程度上发挥各个机制对群落幼苗更新过程的解释能力,仍是困扰许多生态学家的问题。为此,本研究以物种组成丰富的浙江天童20 ha常绿阔叶林群落动态监测样地为平台,对样地内561个幼苗样方(1m2)中的木本幼苗进行了为期3年(7次)的动态监测。根据Kitajima 和 Fenner(2000)对群落幼苗更新的定义,将该群落内的幼苗更新过程分为三个阶段-新生幼苗出现阶段、幼苗建立阶段以及幼苗生长阶段。并利用能够综合群落内不同物种、调查时间和空间位置等分类因素的混合效应模型,分析在群落尺度上,不同更新机制对群落幼苗更新不同阶段的影响,从而了解不同更新机制的时间分化特征。希望依据该时间分化特征能够将三种更新机制进行有机的整合,使其能够更准确更全面地解释群落幼苗的更新过程。本研究的主要研究结果如下：1.群落内的新生幼苗(Newly germinated seedlings)是由种子子叶刚刚展开所形成的,其空间分布格局主要受同种可繁殖个体空间分布格局的限制,说明扩散限制过程是群落新生幼苗空间分布格局的主要形成机制。相比于代表扩散限制的因子,代表生境偏好的微生境因子其影响程度相对较低,但仍有部分微生境因子对新生幼苗的空间分布范围有显著影响。比如,冠层开度因子对群落新生幼苗的个体分布产生了显著负影响,说明在林下光环境较好的生境中,群落新生幼苗的个体数反而相对较少。另外,代表J-C效应的因子并未对群落新生幼苗的空间分布格局产生显著性的影响。2.从群落新生幼苗出现到其建植的建立阶段(Seedling establishment),其存活主要受代表J-C效应的因子影响,使得幼苗在远离母株,靠近其它成树的低密度区域建立。与此同时,代表生境偏好的部分微生境因子也对其存活产生了显著影响。然而,随着群落幼苗苗龄的增加,J-C效应和生境偏好对幼苗短期存活的影响都在减弱。3.建立后的群落幼苗会经历较长时间的生长阶段(Seedling development)才能成为新的可繁殖个体,完成整个更新过程。由于群落幼苗生长阶段的年死亡率低,难以通过3年的短期监测完整地了解影响其存活的大部分因子。为此,我们仅分析了各因子对其短期存活率的影响。结果显示,幼苗的相对生长速率是影响生长期幼苗短期存活最重要的因子。因此,我们可以利用生长期幼苗的生长状况预测其未来存活的可能性,并且通过分析外在因子对幼苗生长的影响,间接地了解生长期幼苗未来可能的存活格局。通过分析我们发现冠层开度是唯一显著影响其相对生长速率的因子。在林下冠层开度较大,光环境较好的生境中,群落幼苗的相对生长速率会显著提升,从而可能间接地提高了其未来存活的可能性。因此生境偏好过程是影响幼苗生长阶段更新的关键机制。综上所述,我们发现在群落新生幼苗的出现阶段,其空间分布格局主要受扩散限制过程的影响,导致群落新生幼苗与母株间形成了明显的聚集格局。在群落幼苗建立阶段,J-C效应主导了群落幼苗的建立格局,使得新生幼苗偏向远离母株的低密度区域建立,分散了原本不利于物种共存的母株与新生幼苗间的聚集格局,为群落中异种幼苗的更新提供空间。另外,在群落幼苗生长阶段,幼苗主要偏好在林下光环境较好的生境中生长和存活,缓解了该生境条件下新生幼苗较少,更新不利的现象。因此依据群落幼苗更新机制的时间分化特征,能够较好地整合三种群落幼苗更新机制,使其能够更准确更全面地解释群落幼苗的更新过程。
[Abstract]:The mechanism of community species coexistence is one of the most important ecological problems. The regeneration process of community seedlings is the key process affecting the coexistence of community species, and it is also the focus of ecologists. Therefore, many hypotheses try to explain the process of regeneration of the community seedlings, including the diffusion restriction hypothesis, the Janzen-Connell effect (below) The J-C effect hypothesis and the habitat preference hypothesis, which are three hypotheses which have higher prediction level in recent years, are considered to be the most important mechanism to influence the regeneration of the community seedlings. However, the three hypotheses independently explain the ability of the whole regeneration process of the community to be relatively weak. How to integrate the three, to the greatest extent, to play various mechanisms The interpretation ability of community seedling regeneration is still a problem that puzzles many ecologists. In this study, the dynamic monitoring site of the 20 ha evergreen broad-leaved forest community in Zhejiang Tiantong, which is rich in species composition, was used to monitor the dynamic monitoring of the 3 year (7 times) of the wood seedlings of the 561 sample plots (1m2) in the sample plots. According to Kitajima And Fenner (2000) for the definition of community seedling renewal, the process of seedling regeneration in this community is divided into three stages, the emergence stage of new young seedlings, the stage of seedling establishment and the stage of seedling growth, and the mixed effect model which can be used to investigate the time and the spatial location of the different species in the community is used to analyze the community scale. In order to understand the time differentiation characteristics of different regeneration mechanisms, we hope that the three regeneration mechanisms can be integrated organically to explain the regeneration process of young seedlings more accurately and more comprehensively. The main research results of this study are as follows: The new young seedlings (Newly germinated seedlings) in the community are formed by the just expansion of the seed cotyledon, and the spatial distribution pattern is mainly restricted by the spatial distribution pattern of the same species of reproducing individuals, indicating that the diffusion restriction process is the main mechanism of the spatial distribution pattern of the new young seedlings of the community. Factors, the microhabitat factors representing habitat preference are relatively low, but there are still some microhabitat factors that have a significant impact on the spatial distribution of the new young seedlings. For example, the canopy opening factor has a significant negative effect on the individual distribution of the new young seedlings. The number of individual seedlings was relatively small. In addition, the factors representing the J-C effect did not have a significant effect on the spatial distribution pattern of the new young seedlings of the community..2. from the emergence of the young seedlings to the establishment of the plant (Seedling establishment), the survival of the seedlings was mainly influenced by the factor of the J-C effect, so that the seedlings were far away from the mother plant. At the same time, some microhabitat factors that represent habitat preference also have a significant impact on survival. However, the effect of the J-C effect and habitat preference on the short-term survival of the seedlings will undergo a longer period of growth as the seedling age of the community increases. Seedling development can become a new reproducing individual and complete the whole process. Because of the low annual mortality rate at the growth stage of the community seedlings, it is difficult to understand most of the factors that affect its survival through 3 years' short-term monitoring. The relative growth rate is the most important factor affecting the short-term survival of the growth period seedlings. Therefore, we can predict the possibility of future survival by using the growth condition of the growth period seedlings, and indirectly understand the possible future survival pattern of the young seedlings by analyzing the effects of external factors on the growth of seedlings. The opening of the present canopy is the only factor that significantly affects its relative growth rate. The relative growth rate of the seedlings in the community is significantly elevated in a habitat with greater canopy opening and better light environment, which may indirectly increase the possibility of its future survival. Therefore, the habitat preference process is the key machine for the regeneration of the seedling growth stage. In summary, we found that the spatial distribution pattern was mainly influenced by the diffusion restriction process in the emergence stage of the new community young seedlings, which led to the formation of a distinct aggregation pattern between the new young seedlings and the mother plants. In the stage of the establishment of the community seedlings, the J-C effect dominated the establishment of the young seedlings, making the young seedlings far away from the mother. The establishment of low density region of the plant disperses the aggregation pattern between the mother plant and the new young seedlings which is not conducive to the coexistence of the species, and provides space for the regeneration of the young seedlings in the community. In addition, in the stage of the growth of the community seedlings, the seedlings mainly prefer to grow and survive in the habitats with better light environment, and alleviate the new young seedlings under this habitat. Less adverse phenomenon. Therefore, the update time updating mechanism based on community differentiation characteristics of seedlings, can better integrate the three kinds of seedling community update mechanism, which can explain the community seedling renewal process is more accurate and more comprehensive.
【学位授予单位】：华东师范大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：S718.5

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