坡位对护坡草坪中构树种群特征及雌雄个体生长的影响

Effects of Slope Position on Population Characteristics and Growth Strategies of Dioecious Broussonetia papyrifera in Degraded Slope Lawn

为了研究雌雄个体对自然坡位适应性的性别差异,以紫色土丘陵区人工建植6年后的3个坡向的边坡草坪为对象,通过测定坡上、坡中、坡下及坡底4个坡位上次生演替构树幼树种群的种群面积、种群密度、年龄结构、雌雄性比、分布系数等特征参数及雌雄个体株高和地径,研究坡位对次生构树种群特征和雌雄个体生长的影响。结果表明:(1)4个坡位的坡度和土壤理化性状有显著差异(P<0.05),构树均可入侵形成次生种群,随坡位降低种群面积、种群密度成倍增加(P<0.05);(2)坡位显著影响种群年龄结构,随坡位降低一年生苗树比例增加,幼树和成年树比例降低(P<0.05),坡上和坡中年龄结构为衰退型,下坡为稳定型,坡底为增长型;(3)坡位显著影响幼树和成年树的性比,坡上和坡中偏向雄株,下坡和坡底偏向雌株,坡位对成年树性比影响大于幼树;(4)坡位显著影响各龄构树的空间分布格局,坡位越低一年生苗和幼苗树越呈集群分布,随树龄增加分布系数均为下降,雌株趋向均匀分布,雄株趋向随机分布;(5)坡位对各龄构树的株高影响大于地径,株高随坡位降低而增加,地径随土层厚度增加而增加。综上,边坡草坪演替成构树+草本的混生群落,雄株对资源匮乏的耐受力强于雌株,雌株对资源的竞争力强于雄株,表现为与坡位的坡向和土壤理化性质相匹配的次生种群特征和个体生长策略,适合在裸露边坡植被恢复中推广与应用。

In order to study the gender differences of male and female individuals’adaptability to natural slope position,the secondary Broussonetia papyrifera population in the degraded slope lawn of purple hilly area was used as study materials.The slope was divided into four slope positions as uphill,middle,downhill and flat,and population characteristics such as population area,population density,age structure,male-female ratio,distribution coefficient,and other characteristic parameters,as well as the height and ground diameter of male and female individuals were determined.The results showed that:(1)There were significant differences in slope size and soil physical and chemical properties among the 4 slope positions(P<0.05).B.papyrifera could invade each position and form secondary population,but the population area and density increased exponentially with the decrease of slope position(P<0.05).(2)The slope position significantly influenced the age structure of the population.With the decrease of the slope position,the proportion of one-year seedlings increased,while the proportion of young trees and adult trees decreased(P<0.05).The age structure of B.papyrifera population on uphill and middle slope was declining type,the downhill was stable and the flat was increasing type.(3)The slope position significantly affected the sex ratio of young trees and adult trees,with male plants on the uphill and middle slopes,and female plants on the downhill and flat slopes.(4)The slope position significantly affected the age spatial distribution pattern of B.papyrifera.The lower the slope position,the more annual seedlings and seedling trees were clustered.With the increase of tree age,the distribution coefficient decreased,and the females tended to be evenly distributed,while the males tended to be randomly distributed.(5)The slope position had more influence on the height of different trees than the ground diameter.The plant height increased with the decrease of slope position,while the ground diameter increased with the increase of soil thickness.To sum up,B.papyrifera invaded the degraded lawn and formed a mixed community of B.papyrifera and herbs.The males’tolerance to the lack of resources was better than females,and the females’competitiveness to resources was stronger than males.The secondary population characteristics and individual growth strategy matched with the slope position and soil physical and chemical properties,so B.papyrifera was suitable for popularization and application in vegetation restoration of bare slope.