Study On Characteristics Of Community Environment Of Rhododendron In Baima Mountain Of Chongqing

Forty-one samples of 20m×20m were set to analysis the composition,canopy density,diversity and habitat characteristics of the associated community of Rhododendron in Baima mountain.And,the relations between spatial distribution of Rhododendron and habitat conditions were studied.Last,based on the study of the size structure of Rhododendron,the Development trend of different species of Rhododendron were discussed.The main results are as follows:(1)Associated communities of Rhododendron in Baima mountain can be classified into 8 types.Different growth form of Rhododendron has different vegetation types to where they grow:shrubby Rhododendron such as Rhododendron mariesii Hemsl.et Wils,Rhododendron simsii Planch are mainly distributed in the Mixed broadleaf-conifer forest;Rhododendron who are Large shrub such as Rhododendron coeloneurum Diels,Rhododendron ochraceum Rehd.et Wils are mainly distributed in evergreen and deciduous broad-leaved mixed forest.Rhododendron who are trees such as Rhododendron auriculatum Hemsl are mainly distributed in the evergreen broad-leaved forest;(2)Different kind of Rhododendron have a certainly different suitable environment.Elevation,slope direction and slope have the most obvious influence on the distribution of Rhododendron species.(1)The distribution range of different species of Rhododendron is different.Shrubs Rhododendron are mainly distributed in an altitude of 1100 m ~ 1300m;Large bush Rhododendron are mainly distributed in an altitude of 1300 m ~ 1700m;Trees form of rhododendron is mainly distributed at an altitude of 1500 m ~ 1800 m.(2)The distribution scope of slope of Rhododendron is mainly influenced by its growth form.Usually,the scope of slope of tree Rhododendron is 0°~45°,Large shrub Rhododendron is 25°~60°and bush Rhododendron is 0°~80°;what's more,the scope of slope of seedling of tree Rhododendron is 60°~90°,seedling of Large shrub Rhododendron is 25°~90°and seedling of bush Rhododendron is 0°~45°;(3)and the slope,are mainly decided by the Rhododendron adaptability to illumination: the Tree Rhododendrons are mainly distributed in relatively flat terrain where have enough sunshine,bush Rhododendrons are mainly distributed in the slope where own medium intensity sunlight,Large bush Rhododendrons enjoy both strong and moderate intensity sunlight,and where the light is weak,such as slope of northwest and north,found no wild Rhododendron occurs.(4)The change of illumination conditions of environment has a great influence on the beginning of flowering and seedling.Generally,the greater the canopy density,the smaller the proportion of flowering,the distribution of seedlings showed a normal distribution,when the canopy density is 0.2~0.6,the number of seedlings in the plot is largest.Rhododendron of Different vegetative form have different adaptability to illumination conditions in community.For the tree Rhododendron a 70% upper light transmission rate is the most conducive to flowering,for large shrubby Rhododendron,this data is 30%~72%,and for the shrubby plants it is 36%-75%.And when a 20%~80% light transmission rate in seedlings layer of tree Rhododendron is most conducive to seed germination and growth;for large shrubby Rhododendron,the data is 18%~58% and 10%~43%(5)Spatial competition between Rhododendron and competitive trees are related to the growth form of wild Rhododendron and the height and DBH of the competition wood.The larger the size of Rhododendron,the smaller the competition with the competition tree in the community,the greater the intraspecific competition;and the smaller the size,the greater the interspecific competition,the greater the intraspecific competition.Spatial neighborhood size have a great effect on flowering and seedling regeneration.The higher the height of the Rhododendron,the larger the area and canopy density,the weaker the illumination,the less the number of seedlings.Therefore,according to the research,when the average neighborhood of Rhododendron is of 5 ?The most conducive to seedling growth and flowering of rhododendron.(6)Analyzing the11 kinds of wild Rhododendron's population age structure,we find that the population of Rhododendron leptothrium Balf.f.et forrest are declining due to lack of seedlings;Rhododendron simsii Planch?Rhododendron augustinii Hemsl?Rhododendron discolor Fr.? Rhododendron ochraceum R.et W.? Rhododendron calophytum Fr.?Rhododendron coeloneurum Diels Rhododendron argyrophyllum Fr.arebelong to the growth of population and the are Rhododendron auriculatum Hemsl.?Rhododendron mariesii Hemsl.et Wils.have a stable population.