Spatial Pattern And Environmental Explanation Of Main Tree Species In Maolan Karst Forest

The evergreen deciduous broad-leaved mixed forest of Maolan Karst in Guizhou Province is a special and highly native forest ecosystem,which is the most complete non-zonal vegetation with important research value in the same latitude in the world.The analysis of the spatial pattern of the main tree species and their environmental interpretation in the Maolan Karst forest is of great significance for the study of the ecological process of this community and the scientific conservation of the native forest of the Maolan Karst forest.Based on the data of each wood scale and environmental factors of the fixed plot of karst evergreen deciduous broad-leaved mixed forest in Maolan National Nature Reserve,the main tree species structure(diameter structure and height structure),spatial distribution pattern and environmental factors affecting its distribution were analyzed using ecological research methods such as important values,point pattern process and redundancy analysis in community ranking analysis,and the following results were obtained:(1)The study area was rich in tree species and the dominant tree species were not obvious,and 9 main tree species were selected according to the important values: Nandina domestica 、 Pistacia chinensis 、 Acer coriaceifolium 、 Boniodendron minus 、 Diospyros dumetorum 、 Distylium myricoides 、 Mallotus philippensis 、 Pittosporum illicioides 、Quercus glauca,and the important values were 4.97%,4.91%,3.73%,3.37%,3.29%,3.19%,2.96%,2.83% and 2.51%,respectively.Among them,Berberidaceae has the highest relative abundance of Nandina domestica,that is,the species has the largest number of plants in the sample plot,the relative significance of Pistacia chinensis in the Anacardiaceae is the largest,and the relative frequency of Mallotus philippensis of Euphorbiaceae is the largest,that is,the number of samples is the largest.(2)The diameter structure of the main tree species in the Maolan karst evergreen deciduous broad-leaved mixed forest was mainly divided into three types,namely the inverted "J" distribution,the "L" distribution and the single-column distribution.Among them,the diameter structure of trees such as Pistacia chinensis,Acer coriaceifolium and Boniodendron minus showed an inverted J shape.The main component of the shrub layer is that the structure of the Nandina domestica is single-columned;The structure of the mother tree of Distylium myricoides and Mallotus philippensis is L-shaped.The number of individuals of the study tree species in each height level varied greatly,and the height structure was L-shaped.There are trees in all height levels,and the height of the main tree species is mainly concentrated in a height of less than 5 m,accounting for 66.08% of all height grades,and the rest of the height grades account for relatively small,and the community state belongs to the stable growth type.(3)The spatial distribution of the main tree species in the community showed a significant aggregation distribution on a small scale,and the degree of aggregation decreased with the increase of the study scale,and then showed a random or uniform distribution.As small trees grow into large trees,the degree of aggregation continues to weaken,and the large trees are mainly randomly or uniformly distributed at the research scale.The relationships between 36 species composed of 9 major tree species were mainly spatially independent on the study scale of 0-40 m,except for Nandina domestica and Pistacia chinensis,which showed significant spatial positive correlation at the scale of 3 m,Pittosporum illicioides and Quercus glauca showed a significant spatial positive correlation at a scale of 1 m.(4)The redundancy analysis showed that 14 soil factors and topographic factors selected in this study jointly explained 86.18% of the distribution of the main tree species in the Maolan Karst evergreen deciduous broad-leaved mixed forest,and the degree of explanation was ideal.Altitude in topographic factors,water content and total phosphorus in soil factors were the key environmental factors affecting the distribution of major tree species in the community.In summary,the community structure of the evergreen deciduous broad-leaved mixed forest of Maolan Karst was relatively stable.The population of major tree species is highly concentrated,and the relationship between major tree species is not close.Due to seasonal drought,poor water storage capacity and lack of nitrogen and phosphorus required for plant growth in soil in karst areas,the spatial distribution of major species is mainly affected by the altitude in the topographic factors,the water content and total phosphorus in the soil factors,and the community is in a relatively stable stage.