Study On The Seedling Competition And Suitable Habitat Of Plant Species With Extremely Small Populations Abies Ziyuanensis

Abies ziyuanensis is a key wild plant at the national level and is only sporadically distributed in the middle and upper parts of a few tall mountains in Guangxi,Hunan and Jiangxi.In recent years,it has been observed that seedlings of A.ziyuanensis have a high mortality rate under field conditions,which is very unfavorable to the recovery of wild populations of this plant.In order to identify the effect of competition on the survival quality of A.ziyuanensis seedlings,this study conducted an experimental analysis of intra-species competition of A.ziyuanensis seedlings in heterogeneous soil environments and competition between A.ziyuanensis and broad-leaved tree seedlings.At the same time,Max Ent model combined with Arc GIS software was used to analyze and predict the future trends of the suitable distribution areas of A.ziyuanensis under the background of global climate change,providing a theoretical basis for population conservation and seedling regeneration in the field under global climate change.The results are as follows:1.The effects of different soil volumes and competition intensities on the biomass distribution,morphological characteristics and seedling quality of A.ziyuanensis seedlings were investigated by constructing double and triple planting competitions at 300 m L,600 m L and 1000 m L soil volumes,respectively.The growth of A.ziyuanensis seedlings was more significantly affected by soil volume than by competition intensity,and the seedlings planted in 1000 m L volume of soil had better growth and development.Soil volume ×competition intensity only significantly effected main root length,and soil volume had the greatest effect on root biomass and morphological indicators of A.ziyuanensis seedlings.This result indicates that soil volume is closely and positively related to the overall growth of A.ziyuanensis seedlings,and large diameter substrate containers should be used for seedling cultivation when cultivating strong A.ziyuanensis seedlings.2.The experiment was carried out in the greenhouse of the A.ziyuanensis reserve,where three soil nutrient environments were set up to compete with the neighboring plants of A.ziyuanensis seedlings and broadleaf maple(Acer kweilinense)seedlings.Considering the characteristic that most soils in nature are non-homogeneous,an environmental condition of soil nutrient availability based on heterogeneity was proposed.The survival rate of A.ziyuanensis seedlings under different soil nutrient treatments was analyzed by competition,and the above-ground growth characteristics and change patterns were investigated in combination with the height,basal diameter and leaf number of A.ziyuanensis seedlings.The results showed that interspecific competition caused increased mortality of A.ziyuanensis seedlings in both homogeneous and heterogeneous soils;A.ziyuanensis seedlings in heterogeneous soil nutrient environments had significant effects on basal diameter at the beginning and end of the experimental cycle,specifically basal diameter and seedling height grew better.3.Max Ent model and Arc GIS software were used to simulate the suitable distribution areas and overall future migration direction of A.ziyuanensis.Max Ent model had a high prediction accuracy,with AUC value reached 0.998.Under the current climate scenario,Guangxi Yinzhu Laoshan National Nature Reserve,Guangxi Quanzhou County and Guanyang County,Hunan Xinning County,Chengbu Miao Autonomous County,Jiangxi Suichuan County,Fujian Pucheng Luohe National Wetland Park and the north-central part of Taiwan Central Mountains were the highest suitable area for A.ziyuanensis.The main climatic factors most suitable for growth were precipitation of coldest quarter,isothermality,precipitation of driest month and mean temperature of wettest season,which ranged from231.99 ～ 433.06 mm,≤ 21.8 %,50.38 ～ 83.57 mm,and 10.6 ～ 20.5 °C,respectively.Under the future scenario of ssp126 and ssp585,A.ziyuanensis suitable distribution area will migrate westward.In summary,under intra-species competition,soil volume changes will affect the root system and above-ground morphological and functional indicators of A.ziyuanensis,and the heterogeneous nutrient environment is favorable to the survival and growth of A.ziyuanensis seedlings;interspecific competition increases the mortality of A.ziyuanensis seedlings.Global climate change will have a profound impact on the appropriate distribution areas of A.ziyuanensis,in which precipitation of coldest quarter,isothermality are the two key factors to determine the suitable growth area of A.ziyuanensis.