Study On Spatial Difference Of Radial Growth Response Of Pinus Sylvestris Var. Mongolica In Plantations In Heilongjiang Province To Climate

Mongolian pine(Pinus sylvestris var.mongolica)is widely used in afforestation projects in northern China.Planted Mongolian pine trees have experienced severe growth declines in recent years in the southeast part of northeast China.Yet,litter is known on how the warming or drought affects the planted Mongolian pine growth in the northeast part of northeast China,the northern edge of planted Mongolian pine forests.We used a tree-ring network of 1270 tress from 54 plantations to investigate how the drought influenced tree growth in the northern edge of plantation.To study how the climatic factors(temperature,precipitation,relative humidity,PDSI,VPD,SPEI)affect the radial growth of Pinus sylvestris var.mongolica in the north edge plantation.To analyze the correlation between ring width and climate factors of Pinus sylvestris var.mongolica in artificial forest and to discuss the influence of radial growth of Pinus sylvestris var.mongolica in north China.The main results are as follows:1、Tree growth was negative correlated with June temperature from most sites(92.5%)for the period 1987-2017.The radial growth was positive correlated with June precipitation in most sites(92.5%).Precipitation and temperature had no significant influences on growth in most sites.The radial growth showed a positive correlation with PDSI in June,July and August in most sites(83.0%).The strongest correlations between drought index(PDSI,VPD)and growth were found in summer.2、Drought is the main factor controlling Mongolian pine growth in our study regions.The response of radial growth to summer PDSI changed significantly from negative to positive with increased PDSI(R2 = 0.177,p < 0.01).Tree growth showed a significantly positive correlation with PDSI(p<0.05)in 17 sites of the mesic region.The radial growth was negatively correlated with summer temperature in most sites(62.3%),but has a positive correlation with precipitation(79.2%)and RH(77.4%).The radial tree growth was negatively correlated with VPD in most sites(73.6%).3、The radial growth of Mongolian pine was strongly influenced by drought.Narrow rings appeared in severe drought years,while wide rings form in wet years.Tree growth reduced about 17% in severe drought years in the mesic sites while tree growth reduced 9% in xeric sites.Trees reduced their growth by 9% in common drought years in mesic sites and 7% in xeric sites.