Reconstruction Of Forest Pests History Based On Tree Rings Late Wood Width In The Fujian Region

The humid subtropical region,as an important ecological barrier in China,has always been a key area for the country to carry out forest resource protection and ecological security guarantee work.Climate change has significantly increased the frequency and severity of forest pest disasters in most parts of the world.The short and incomplete historical record of forest pest outbreaks in China limits the comprehensive understanding of the response mechanism of pest outbreaks to climate change.In this study,by establishing a tree ring dataset in the humid subtropical Fujian region of China,combining tree-ring climatology and ecological analysis methods,we compared and analyzed the dynamic evolution characteristics of cells in the cambium and woody parts of the host and healthy Pinus massoniana Lamb.before and after infection,and the differences in their responses to climate,evaluated the impact of the outbreak of Dendrolimus punctatus Walker on different wheel width indicators,and reconstructed the outbreak history of Dendrolimus punctatus Walker in Fujian over the past 200 years,clarify the relationship between climate factors,coupled sea air modes,and pest outbreaks,and explore the ecological resilience differences of Pinus massoniana Lamb.growth in response to drought and pest stress.The main research content and conclusions of the paper are as follows:(1)After being infected with pine wilt disease,the number and growth rate of cells in each stage of the xylem formation of host Pinus massoniana Lamb.was significantly inferior to those of health Pinus massoniana Lamb..However,in the early stages of infection,the number and growth rate of cells in each stage of the xylem formation of host Pinus massoniana Lamb.are superior to those of healthy Pinus massoniana Lamb.This is because Pinus massoniana Lamb.significantly improves its photosynthetic capacity after being damaged,which is a plant defense reaction.The number of cells in the cambium of healthy Pinus massoniana Lamb.is significantly positively correlated with relative humidity.This is because higher air humidity can wet the tree crown,reduce leaf water potential,and water enters the cambium cells through infiltration,leading to the expansion of the cambium and subsequent cell enlargement;there is a significant negative correlation between the number of cells in the cambium of healthy Pinus massoniana Lamb.and the vapor pressure difference(VPD).This is because the increase in VPD leads to an increase in a transpiration rate,leading to an increase in negative pressure in the water transport system of the tree.As a result,the swelling pressure of the cambium cells in the trunk decreases,and the cells contract.(2)Compared with the tree-ring-width and early-wood-width of trees,the results of the outbreak history of Dendrolimus punctatus Walker based on the reconstruction of tree rings late-wood-width are more accurate.This is because there is a significant “lag effect”in the radial growth of the tree-ring-width and early-wood-width,which means there is a2-3 year time interval between the outbreak year and the maximum radial growth reduction based on the reconstruction of the tree-ring-width and early-wood-width.The outbreak of Dendrolimus punctatus Walker in different regions of Fujian is not synchronized,because the intensity of pest outbreaks may vary in different regions,and trees in areas with superior growth environments are more resilient and/or productive than those in other regions.(3)The climate model and ocean-atmosphere interaction of the opposite outbreak year and non outbreak year of the summer Dendrolimus punctatus Walker in Fujian region indicates that warmer and drier climate conditions are conducive to the outbreak of the summer Dendrolimus punctatus Walker in Fujian region,and the outbreak of the summer Dendrolimus punctatus Walker in Fujian region is significantly affected by the La Ni(?)a event.(4)When dealing with drought and pests stress,the resistance and resilience of Pinus massoniana Lamb.growth is balanced against each other.Pinus massoniana Lamb.populations in Sanming and Nanping showed higher resistance to drought,but lower resilience;The Pinus massoniana Lamb.population from Fuzhou prioritizes resilience over resistance.The Pinus massoniana Lamb.population in Fuzhou exhibits a more conservative strategy,indicating an adaptive advantage under water stress.The resistance of Pinus massoniana Lamb.to pests is significantly lower than that of drought events,while its resilience to pests is significantly higher than that of drought events.This is because Pinus massoniana Lamb.leaves tend to store nutrients and slow down growth after loss,which is the result of long-term adaptation and evolution of plants to the environment.It is a conservative carbon utilization strategy,which is more conducive to resisting the adverse effects of pests again.This study compensates for the short historical record of the outbreak of Dendrolimus punctatus Walker in Fujian region,and has important application value in studying the long-term evolution characteristics and laws of Dendrolimus punctatus Walker.It helps to comprehensively understand the response mechanism of Dendrolimus punctatus Walker outbreak to climate change,and is conducive to maintaining the stability and balance of the forest ecosystem,effectively maintaining the forest ecological environment,and achieving the healthy development of forestry,provide a scientific basis for ensuring forest ecological security in subtropical regions of China.