鼎湖山针阔混交林锥栗种子距离制约研究

Janzen-Connell 距离制约假说认为:扩散到远离母树地点的种子,更容易逃避种子捕食者和病原体侵染。验证锥栗(Castanopsis chinensis)种子是否支持该假说,可以预测锥栗种群分布格局,解释锥栗种群更新不良的原因。在鼎湖山针阔混交林内,选择离成年母树3、10和15 m处,进行种子放置实验,以及种子消毒和未消毒埋土实验。在无覆盖实验中,10 m处大种子的消失数始终最大,种子离母树距离和种子大小两个因素对种子消失数均没有显著性影响。在排除哺乳动物实验中,种子放置第一周,种子消失数均很少。整个试验期,种子离母树距离和种子大小两个因素对种子消失数也没有显著性影响。在病原体实验中,埋土前两个月,经过消毒的种子袋中种子均保存完好,没有病原体侵染。埋土的种子从第三个月到第六个月,不同距离处的种子,以及消毒和未消毒处理的种子,被侵染数之间均有显著性差异;被侵染的种子数到第六个月趋于稳定。因此,锥栗种子被脊椎动物取食,不呈现距离制约(Distance-dependent)格局;而被病原体侵染的种子命运则支持距离制约假说。

STUDY OF DISTANCE-DEPENDENCE ON CASTANOPSIS CHINENSIS SEED IN CONIFEROUS AND BROAD-LEAVED MIXED FOREST OF DINGHUSHAN, CHINA

Aims The Janzen-Connell hypothesis is that seed survival improves with increased distance from the parental plant. Our objectives were to determine whether the Janzen-Connell hypothesis (1) is supported by Castanopsis chinensisseed survival, (2) can forecast the population’s distribution pattern, and (3) explains the reason for limited recruitment. Methods We selected three mature C. chinensis trees in coniferous and broad-leaved mixed forest of Dinghushan, China and recorded seed mortality with Open treatments (OP), Small Mammal Exclusion experiments (EM) and pathogen infection treatments at 3, 10, and 15 m from the trees.  Important findings In the OP treatment, the number of missing seeds was largest at 10 m; however, seed predation was not significantly affected by distance from tree and seed size. In the EM treatment, few seeds were missing in the first week, and seed predation was not significantly affected by distance and seed size during the study period. In the first two months, seeds with Caoton treatment remained intact, and from the third to the sixth month, the number of seeds infected by pathogens was significantly affected by distance and disinfecting action. After the sixth month, the number of seeds infected by pathogens was relatively constant. These results illustrate that pathogens are related to mortality of seeds of C. chinensis and that this mortality is distance dependent, while the mortality caused by vertebrate animals is not distance dependent.