The Study On Community Ecology Of Pinus Kwangtungensis Forest In Hainan Province

Pinus kwangtungensisis a special kind of conifers in our country,mainly distributed from tropical distribution to north pan tropic distribution in Guangdong,Guangxi,Guizhou,Hunan and Hainan Province.Among of those,P.kwangtungensis in Hainan is primary distributed at a high altitude of 1000～1800 meter’s regions,including the Yingge Mountains and middle part of Wuzhishan Mountains,and the Jiaxi Mountains in the southwestern part,and the first two regions are most typical.As the southernmost area distribution of P.kwagtungensis,it is of great scientific value and practical significance to the study on the structural characteristics of the P.kwangtungensis community,the coexistence mechanism of community species,the community structure and stability of P.kwangtungensis forest.Therefore,we established four plots,three from the Yingge Mountains and one from the Jiaxi Mountains,14400 square meters totally.We conducted a comparative study in terms of the community structure characteristics,dominant population niche,inter-specific associations and community stability.We found that:(1)From the aspect of community species,families distributed in Pan-tropic and tropical Asian have an advantage in the number of P.kwangtungensis forest in Hainan.For the difference of the altitude,the species composition of P.kwangtungensis forest both in Yingge Mountains and Jiaxi Mountains presents some difference to some extent.On the one hand,the former consist of Myrtaceae,Rubiaceae,Myrsinaceae,and so on,which belong to a middle low elevational families in Pan-tropic.On the other hand,the latter include the theaceae,symplocaceae,polypodiaceae,some high altitude Families in Pan-tropic.Compare to the similar Sampling area,the species composition of P.kwangtungensis forest in Hainan is obviously less than the distribution in Guangdong,Guangxi,et al,no matter it concerns with the number of vascular plants Families or Genera of quantity.Therefore,the community tends to be more unstable,the recession tends to be more serious,and the reasons are under the investigation.With the analyze of dominant population diameter class structure,all the hardwood species in various plots’ dominant population are parts of growth population or stable population,and the diameter classes in population update well,its development and stability is good.On country,as P.kwangtungensis population occupy a significant position in Tree layer,it is far less than dominant population in other layers,such as seriously aging,difficulty of seedling regeneration,and large age-class dominance.P.kwangtungensis population is declining.The analysis results of species diversity shows,the species diversity of these four plots is plot 2(4.367)>plot 3(4.332)>plot 4(3.958)>plot 1(3.714),and the Pielou is plot 2(0.791)>plot 3(0.756)>plot 1(0.736)>plot 4(0.660),moreover,the plot 2 with the highest species diversity index and evenness index,then,it’s the plot 3,and plot 1and plot 4 take the lowest position in species diversity index and evenness index.(2)Studied in the 4 sample areas,the niche breadth of P.kwangtungensis population ordered as plot 4(2.1014)>plot 1(1.6016)>plot 2(1.4441)>plot 3(1.1701).P.kwangtungensis population in the fourth plots possess the strongest adaptability and competitiveness,and the third plots is the weakest.Besides,the niche breadth of P.kwangtungensis population in the fourth plot is not far distinct with the other dominant population.Compared to other three samples,the species population decline is the most slow,but still has strong competitive ability.And the difference in the third plots is the most significant,the competitiveness is the weakest,if the community develops naturally,the third plot of P.kwangtungensis population may be the earliest succession drop or withdraw from the original community and spread out,followed by no.2 and no.1,finally,it is 4.Niche overlap and niche breadth of these four plots of P.kwangtungensis population is the same with the other dominant population in the size of the order,it’s plot 4>plot 1>plot 2>plot 3,but among the niche overlap of the other dominant population,P.kwangtungensis population on the four plots is on the top,so as the competition and crowding from other dominant population,followed by plot 2 and plot 1.The smallest of niche overlap is the third plot,and the large niche breadth form the niche overlap.At present,the use of resources and the degree of different isolation of P.kwangtungensis population in Hainan is not obvious,is a kind of population mixed between needle and the instability of the transition and evergreen broad-leaved forest community.(3)The analysis results on inter-specific associations of dominant population reveals that the other three plots of P.kwangtungensis population generally present the obvious positive correlation while the third plot shows the invisible negative correlation.The results of positive and negative coupling of the X2-tes are 1.23,1.75,0.76,and 1.33,the positive and negative coupling of coupling coefficient AC)are 1.02,1.83,0.76,and 1.33.This two conclusions show a high consistency,and its cooperatively use more correctly reveals the correlation of correlation.Meanwhile,its(OI)index result shows that all the dominant population plots with the species of 48.57%,76.19%,46.67%,58.1%closely linked.Between the P.kwangtungensis and dominant population,the inter-species relation of the second plot is dominant on positive correlation,while the other three plots are superior to the other on negative correlation.In the process of growth and renewal,P.kwangtungensis is not only restricted by Inter-specific competition,but also affected by the fierce competition from other species.(4)Study on community stability proved that the four plots including Tree layer,shrub layer,Herb layer,and its stability and stable point 20/80 exist some difference,so the degree of stability is not so good.On the comparing stability of all the structure layers,it’s ordered as shrub layer>Herb layer>Tree layer,and its overall stability listed as plot 4>plot 1>plot 3>plot 2.With the common impact of the dominant population’s biological characteristics and environmental factors,the community is unstable.If the succession of the community goes naturally,and with the enhancing inter-specific competition,the existing community environment and the population structure of P.kwangtungensis may firstly order the certain change of community pattern,then the dominant position of the P.kwangtungensis will be gradually taken place by the broad-leaf species,at last,it will disappear or out of The original community distribution area,spreading around.