不同海拔梯度紫果云杉径向生长对干旱事件的响应OA

To investigate the response patterns of the radial growth of Picea purpurea to drought events across different altitudinal gradients in the Miyaluo forest area of western Sichuan,this study collected a total of 90 tree-ring cores at altitudes of 3 100 m(low altitude),3 300 m(mid altitude),and 3 500 m(high altitude)within the area and established tree-ring width chronologies for the low,mid,and high-altitude zones,respectively.Correlation analyses were then conducted between the tree-ring width chronologies of the three altitudes and monthly climatic factors[maximum temperature,mean temperature,minimum temperature,Palmer Drought Severity Index(PDSI),and monthly precipitation]from September of the previous year to September of the current year.Meanwhile,the resistance,recovery,and resilience of trees during three drought events,as well as the recovery ratio and recovery time of trees after drought stress,were assessed.The results showed that the three drought events occurred in 1986,1997-1998,and 2002-2003,with PDSI values of-1.7,-2.1,and-2.5,respectively.The first drought event reached the level of mild drought(PDSI<-1.0),and the second and third drought events were classified as moderate drought(-2.0<PDSI<-3.0).Trees at low,mid,and high altitudes were all affected by the three drought events,and generally exhibited lower ring width indices during or after the occurrence of these drought events.Specifically,tree radial growth at the low altitude was negatively correlated(P<0.05)with the mean temperature,minimum temperature,and maximum temperature in March of the current year.No significant correlation was found between tree radial growth at mid altitude and any monthly climatic factor.Tree radial growth at the high altitude showed positive correlations with the mean temperature and minimum temperature in December of the previous year(P<0.05,P<0.01),respectively.Moreover,it exhibited a negative correlation with the precipitation in October of the previous year(P<0.05)and a positive correlation with the precipitation in January of the current year(P<0.05).In addition,trees at the high altitude showed higher resistance,recovery,and resilience to drought events than those at mid and low altitudes,with trees at mid and high altitudes having the fastest post-drought recovery(completing recovery in only 4 years),while trees at the low altitude required 6 years to recover.