Spatial Distribution Pattern Of The Natural Population Of Tetracentron Sinense Oliv. In Leigong Mountain National Nature Reserve

In this paper,the spatial distribution pattern of Tetracentron sinense Oliv.natural population in Leigong Mountain nature reserve and its influencing factors were studied.The results are as follows:(1)The seedings and saplings of T.sinense population were extremely scare,and the adult trees were the most,but the old-aged trees were few.The natural regeneration of T.sinense population was poor,which was in the early recession stage.Point pattern analysis found that four patches showed a high cluster distribution in a small scale.There were different spatial correlations between different age-classes of T.sinense.saplings and adult trees showed positive correlation at smaller scale indicating the cooperative action between them,while adult trees had no correlation with old-aged trees,and even showed negative correlation in some patches,indicating the stronger competition between adult and old-aged trees.(2)In T.sinense communities,the important value of T.sinense was the highest,indicating the characteristics of constructive species,and the important value of other four species(including Styrax japonicus,Acer sinense,Pterostyrax psilophyllus and Cerasus tomentosa)were relative higher,suggesting the associated dominant species.In different patches,there were positive correlation between the dominant species and T.sinense at a small scale,which gradually became irrelevant as the scale increased,and even negative correlation in some patches at a certain scale.The results indicated that there may be ecological characteristics of cooperation between the T.sinense population and the its associated dominant species in a certain scale range.On the contrary,different dominant species had negative correlation phenomenon in different patches,indicating that the competition between T.sinense and its associated dominant species became more intense.(3)The whole change of soil mineral elements in the reserve was not great.The content of different mineral elements in the same patch varied greatly,but the content of the same mineral element in different patches was similar.Most of the mineral elements in each patch had positive correlation,indicating cooperation action between mineral elements.The total amount of seven mineral elements(including sodium,calcium,magnesium,zinc,phosphorus,potassium and nitrogen),all belonged to moderate variation intensity.The action size was different among the seven mineral elements in the reserve,and the six mineral elements(including TCa,TMg,TZn,TN,TP and TK)had higher content indicating higher contribution rate.The distribution of most mineral elements in the soil showed a better spatial structure,the spatial self-correlation of each mineral element was strong,and the random factors had little influence on their distribution.The spatial distribution of mineral elements in each patch were predicted,similar distribution characteristics was found in the same elements among different patches.The content of various mineral elements was obviously related to the altitude,and the maximum value of most mineral elements appeared in the middle altitude area.(4)Altitude in four patches was the main habitat factor affecting the distribution of T.sinense.The distribution of T.sinense in the reserve had similar characteristics in different patches: all of them were distributed in the middle and lower altitude regions,where the mineral elements content was relatively rich.Altitude was also the main factor affecting the distribution of mineral elements.CCA ranking analysis among the dominant species and habitat factors in the T.sinense community showed that the first two ranking axes can explain more than 50% of relationship between species and their habitats,and the correlation between species and theirs habitat factor ranking axis was high,indicating the reliability of the ranking results,and also indicating that the distribution of T.sinense and its associated dominant species was greatly affected by habitat factors.(5)According to the results above,some suggestions were put forward.Firstly,the management of the reserve and awareness of protection should be strengthened,and in-situ conservation for T.sinense should be also carried out.Secondly,artificial intervention should be implemented to impropve the input of some mineral elements(including Ca,Zn,Mg,N and K),to create forest gap or forest edge environment for T.sinense,and to reduce the competitive effect of its associated species on the resource utilization,and then to promote the establishment of seedlings and saplings,and to promote there generation of T.sinense natural populations.