The Health Status Of Ancient Trees And Their Variations Along Altitudinal Gradient In The West Tianmu Mountain,Zhejiang Province

As an important part of forest and urban ecosystems,ancient trees support a large group of animal and plant species,and sustain critical ecosystem services for us.Currently,a large amount of ancient trees is facing serious threats of dramatic decline or dieback in the face of climate change and anthropogenic disturbance.In China,many ancient trees are distributed in mountainous areas,and thus the mountains should be one key area for the studies of ancient tree distributions and conservation.Along the elevation gradient in mountains,plants and animals face different levels of anthropogenic disturbance,which may have an important impact on the growth,reproduction and protection of ancient trees.However,few studies have quantitatively assessed the relation between ancient tree health and elevation gradient.The understanding in ancient tree distributions along elevations and the limiting factors could contribute to ancient tree management and conservation strategies.Tianmu Mountain National Nature Reserve is located in the northwest of Hangzhou,Zhejiang Province.Due to its complex terrain and suitable climate,there are over 5000 ancient trees in this area,and the reserve is well known as “The Kingdom of Large Trees”.Currently,quantitative evaluation on the variations of the ancient trees' ratio of the tree trunk decay and hollow area along elevation is absent in Tianmu Mountain.In this study,the PICUS Tree Tomography was used to investigate the ratios of decay and hollow area in ancient trees' trunk,and 137 ancient trees of 11 species were surveyed.By analyzing the variations of ancient trees' ratio of the tree trunk decay and hollow area along altitudinal gradient and its correlations with climate and tree size,I found that:(1)The ratio of decay and hollow area in the ancient tree trunks is 18.89% on average(±1.73%).Nearly 36% of the ancient trees have decayed trunk without a hollow,and 62% of the trees have hollows in the tree trunk.(2)The ratio of the tree trunk decay and hollow area of ancient trees varied with species.There are seven ancient tree species in high ratio of the tree trunk decay and hollow area,including Torreya grandis,Ginkgo biloba,Quercus acutissima,Pinus taiwanensis,Liquidambar formosana,Phoebe chekiangensis and Metasequoia glyptostroboides,while four species in low ratio of the tree trunk decay and hollow area,including Cryptomeria fortune,Ostrya rehderiana,Litsea auriculata,and Pseudolarix amabilis.(3)The ratio of the tree trunk decay and hollow area of ancient trees showed significant correlations with altitude.The ancient trees with decayed or hollow conditions in trunks and the ratios of the decay and hollow area increased with increasing altitude.(4)The ratio of the tree trunk decay and hollow area of ancient trees also showed significant correlations with tree size.The trends were similar with the patterns of altitudinal gradient.To sum up,the ratio of the tree trunk decay and hollow area of ancient trees varies.Along altitudinal gradient from 300 m to 1200 m,there are some clear patterns between the health status of ancient trees and tree size.These findings provide critical information for the protection and management of ancient trees.