Ecological Responses Of Alsophila Spinulosa Communities To The Phyllostachys Heterocycla Disturbance Of Chishui Alsophila Spinulosa National Nature Reserve

Alsophila spinulosa whichbelong to Cyatheaceae,Alsophila,which is an ancient relic plant and classified as the National Grade 2 Protected Plantsin the List of National Key Protected Wild Plants.Chishui Alsophila spinulosaNational Nature Reserve is one of the largest number and most wide area of A.spinulosa and is the reserve which puts A.spinulosa and their living environment as protected object.A recent survey found that the bamboo area is constantly expanding and it invading the A.spinulosa community rapidly and destroying the native ecological environment of A.spinulosa which cause the decrease of the number of A.spinulosa.A.spinulosa is being tested to its limit.This paper takes A.spinulosa for research whichis disturbed by P.heterocycla in Chishui Alsophila spinulosa National Nature Reserve.Based on the theories and methodologies of ecology and phytocoecology,the ecological characteristics under P.heterocycla disturbance such as the clum density ofbambooand other species,floristic composition,life form,community structure,species diversity and niche were analyzed,to reveal the ecological response of A.spinulosa community under P.heterocycla.In addition,the basic ecological response of A.spinulosa which are severe disturbed by P.heterocycla and Dendrocalamus latifloruswere analyzed.Provide valuable informations for the effective protection of A.spinulosa natural forest resource,the restoration and reconstruction of A.spinulosa community which are degraded and disturbed by bamboo plants.The main results are summarized as follows:1?The clum density of A.spinulosa and other species decreased,the total number of standing tree ofA.spinulosa community decreased first and then increase with the increasing of P.heterocycla disturbing intensity.2?45 families,73 genera,82 species of vascular plant were found in 9 communities which were disturbed by P.heterocyclabut the species composition is relatively simple.The P.heterocycla disturbance had an effect on the floristic composition of the A.spinulosa community.The species composition of the A.spinulosa community in family,genus and species were generally decreased.Compared with mild disturbance,the species composition in the A.spinulosa community were decreased by 24 family,43 genus and 45 species under severe disturbance.The P.heterocycla disturbance had a minor effect on on the property of the A.spinulosa community floras.From the family level,the floras were dominated by pantropic distribution family,accounted for 65.38%,68.75% and 75.00% of the total number of seed plants which is consistent with the distribution of subtropical evergreen broad-leaved forest.From the genus level,the floras were dominated by tropical genera,accounted for 82.61%,75.86% and 66.68% of the total number of seed plants.3?The P.heterocycla disturbance had influenced the life form spectrum of A.spinulosa community and the influence on phanerophyte and geophytes is relatively obvious.The A.spinulosa community had similar life form spectrum and the phanerophyte occupied a dominant position accounting for 54.29% and 44.68% respectively under mild and moderate disturbance.And the geophytes are the dominant life form under severe disturbance.In addition,the P.heterocycla disturbance had influenced the crown density of A.spinulosa community.From the perspective of shade tolerance,the percentage of tolerant-shade plants decreased first and then increased,the percentage of light-demanding and neutrophilous plants increased first and then decreased with the increase of P.heterocycla disturbing intensity and the crown density of A.spinulosa community decreased first and then increased.4?The P.heterocycla disturbance had severely influenced the diameter and height class structure of tree layer.Bamboo gradually expanded to adjacent communities,and occupied the dominance of the tree layer,simplifying the structure of the community.The large diameter and height class individuals gradually disappear with the increasing of P.heterocycla disturbing intensity which makes the community more vulnerable to decay.The middle-aged plants are dominant and the seedlings,young-plants are absence in A.spinulosa population which are decline under the disturbance of diferent P.heterocycla intensity.The decline trend is more obvious under moderate and severe disturbance.5?The important value of P.heterocycla in tree layer raised up to 0.6551 and 0.9326 which is the dominant species in the tree layer under moderate and severe disturbance.In addition,the P.heterocycla disturbance had influence the status of A.spinulosa in the community.The important value of tree and shrub layer of A.spinulosa had decreased and the important value of herb layer had increased with the increasing of P.heterocycla disturbing intensiy.The species diversity characteristic of tree layer,shrub layer and herb layer were different under disturbance of different P.heterocycla intensity.The species diversity of tree layer was most affected by P.heterocycla disturbance.The species richness of A.spinulosa community were mild disturbance > moderate disturbance > severe disturbance.By the change rule of Shannon-weiner index,the species diversity of tree and shrub layer was most affected under P.heterocycla disturbance.By the change rule of Simpson's index,the dominant of tree layer was most affected under P.heterocycla disturbance.By the change rule of Pielou index,the stability of tree layer was gradually decreased and the stability of shrub,herb layer were increased first and then decreased with the increase of P.heterocycla disturbing intensity.6?The niche breadth value of Melliodendron xylocarpum was biggest,1.99 and the maximum value of niche overlap appeared in A.spinulosa and Sloanea leptocarpa,Ficus irisana,0.93 under P.heterocycla mild disturbance.The niche breath value ofP.heterocycla were biggest,2.90 and 2.97,the maximum value of niche overlap were appeared in A.spinulosa and P.heterocycla,0.92 and 0.55 under moderate severe disturbance.The niche breadth value of A.spinulosa,the niche overlap value of A.spinulosa and P.heterocycla was increased first and then decreased with the increase of P.heterocycla disturbing intensity.The niche breath value decreased to 1.00 under severe disturbance.7?Compared with P.heterocycla severe disturbance,the influence of the clum density ofbambooand other species,floristic composition and life form under D.latiflorus severe disturbance were larger.