Carbon Stock Of Chinese Pine Plantations And The Response Of Radial Growth To Climate On The Loess Plateau

Chinese pine is one of the main afforestation tree species in the Loess Plateau and plays avital role in ecological civilization construction and vegetation reconstruction.At present,with the majority of Chinese pine plantations entering the middle-aged and mature forest stage,the issues of structural optimization and management of Chinese pine plantations and how to respond to climate change have gradually emerged,which was an urgent problem in sustainable management of Chinese pine plantation in the region.In this study,tree ring analysis was used to study Chinese pine plantations in Xunyi,Huangling,Huanglong,Fuxian,Yichuan,Zhidan and Shenmu,in order to clarify the growth process,evaluate the carbon storage of Chinese pine,and reveal the response of its radial growth to climate factors.The relevant results in this study can provide the foundation for the structural optimization and management of Chinese Pine forests and their adaptation to climate change.The main results are as follows:(1)The radial growth of Chinese Pine plantations showed a significant downward trend with the forest age,and did not show a significant change with the latitude.The values of the radial growth are concentrated at 0.2-1.0 cm/a.The radial growth in Huangling and Yichuan was the largest,over 1.4 cm/a,and the minimum value was 0.1 cm/a in the Loess Plateau.(2)The carbon content of Chinese Pine plantations was leaves> branches> trunks> bark> roots.Among regions,the highest carbon content of leaves in Shenmu was 50.45%,and the lowest carbon content of leaves in Yichuan was 41.30%.The carbon content of branches and trunks were highest in Xunyi,which were 49.25% and 45.92%,respectively.The lowest in Yichuan were 40.65% and 40.29% respectively;the carbon content of bark and roots were highest in Fuxian,respectively 41.82% and 40.68%,and the lowest in Shenmu were 36.83% and 35.68%.(3)The carbon stock of individual organs of Chinese Pine in different regions first increased and then decreased with the forest age.The carbon stock of individual organs in each region showed leaf > trunk > branch > root > bark.In the later stage of the growth,the carbon stock of leaves was larger than that of trunks.The forest age of this transformation in Xunyi,Huangling,Huanglong,Yichuan,Zhidan and Shenmu was 29 a,32 a,40 a,33 a,22 a and 6 a;At the same time,the root carbon stock also had a trend to change to the bark carbon stock.The forest age in the six regions of Xunyi,Fuxian,Huangling,Zhidan,Huanglong and Yichuan is 26 a,26 a,25 a,24 a,19 a,and 31 a.In the later stage of the growth,the individual carbon stock of the Chinese Pine plantation showed Huanglong > Fuxian > Xunyi > Huangling > Zhidan > Yichuan > Shenmu.(4)The cumulative carbon stock in different regions showed a consistent upward trend.Trunks and leaves have the largest cumulative carbon storage,followed by branches,roots and bark.The carbon stock of the leaves in Shenmu was biggest,accounting for 39.83%,while the trunk carbon stock was maximum in the remaining regions in the early growth stage(50.68-62.32%),and the trunk and leaf carbon stock in the later period did not differ much,32.56% and 35.93%.The accumulated carbon stock in stands showed Huanglong > Huangling > Fuxian > Xunyi > Zhidan > Yichuan > Shenmu.(5)The radial growth had a negative correlation with monthly precipitation,and had a positive correlation with the monthly average temperature in Xunyi,Huanglong and Huangling.The radial growth had a positive correlation with monthly precipitation and had a negative correlation with the monthly average temperature in Yichuan and Shenmu.The radial growth was mainly related to the precipitation and average temperature of the growing season(June-August),the growing end season(September-November)and the growing end season of the previous year.The radial growth was significantly positively correlated with the average highest temperature in the growing season of the previous year in Huanglong and Huangling,while in Zhidan and Yichuan,it was significantly negatively correlated with the lowest temperature in the growing season.In addition,the radial growth of Chinese Pine was affected by the climatic factors from September to November of the previous year,indicating that precipitation and temperature have significant lagging effects on the radial growth of Chinese Pine plantations.