黄山濒危植物小花木兰生态位与年龄结构研究

基于对黄山风景区濒危植物小花木兰（Magnolia seiboldii）分布群落的样地调查，采用定量分析的方法，研究了小花木兰群落中主要种群的生态位宽度、生态位重叠和小花木兰种群的年龄结构．结果表明：（1）分别用Levins和Shannon weiner两指数测得的主要优势种群的生态位宽度结果基本一致；重要值大的种群一般具有较宽的生态位。生态位重叠与生态位宽度有关，具较宽生态位的种群一般与其他种群具有较高的生态位重叠，另外，具有相似生境要求和相似生物学特征的种群间也具有较大的生态位重叠，如都是耐萌种的小花木兰与四照花（Dendrobenthamia japonica）的生态位重叠值较高。种群间生态位重叠程度较高，物种间关系复杂，对资源共享趋势明显。（2）小花木兰为星散间断分布，在群落中处于伴生从属地位，生存易受群落变化的影响。对生境要求相似的种群在同一生境下当资源充分时能形成良好的共生关系，支持林思祖等人的生态位重叠与竞争不成相关关系的学说。（3）通过对小花木兰年龄结构的统计发现，小花木兰年龄结构不完整，属于衰退型，幼苗储备严重不足，成为该种群更新的一大瓶颈。（4）它的高海拔分布显示了低温是它生存的一个重要保证；水分也是影响小花木兰种群动态的重要因子。散花坞生境中小花木兰生长良好，呈增长趋势，而清凉台生境小花木兰则表现为年龄老化，呈衰退趋势。散花坞和清凉台可视为重点保护生境，其间生境差异导致的种群动态差异有待于进一步探讨。

Age structure and niche of the endangered Magnolia sieboldii in Huangshan Mountain

Based on the data collected from the plots investigation along with the implementation Levins,Shannon weiner and niche overlap formulas,this paper investigated the niche breadth values and niche overlap values of the main tree species were measured in the natural forestry of Magnolia sieboldii and the age structure of Magnolia sieboldii The results showed that: The descending order of niche breadth value was to some extent in accordance with that of important values,but Enkianthus chinensis is different from others for its strong adaptability.The values of niche overlap were relevant to niche breadth in that the populations with wide niche breadths usually had high overlap values with the other populations.The niche overlap values among the populations with the same or similar environment requirements and similar biological properties were also higher.For example,Magnolia sieboldii and Enkianthus chinensis,with the same shade-tolerant characteristic,had high overlap value.Through this niche research it was shown that Magnolia sieboldii,is characterized by scattered distribution,poor regeneration and less competitive advantages with associated species in the community.Thus,Magnolia sieboldii was easily influenced by community variation.It was found that populations with the same ecological characteristics could form a fine relation in the same habitat when resources were sufficient.This finding provided further support for linsizu's theory that the relationship between niche overlap and competition was not positively correlated.It was also found that the age structure of Magnolia sieboldii was not integrated as young trees were absent,Such inconsistencies threaten population development.Water condition, for example,was an ecological factor which affected the presence of Magnolia sieboldii,and its high altitude distribution showed its need for low temperature.Magnolia Sieboldii grew well in Sanhuawu,while,its age structure in Qinliangtai was older than those in other plots,Qinliangtai and Sanhuawu can be regarded as key conservation habitats and it can be noted that the dynamic differences brought about by the variance between the two habitats above would merit further exploration.