Response Relationship Between The Growth DF Xing'an Larch And Climate Change

The issue of global climate change has been attracting much attention in academia.In recent years,the response of terrestrial ecosystems to global climate change has become one of the core of this problem.As an important part of terrestrial ecosystem,forest can reflect environmental changes in some aspects.For example,tree growth will be controlled by genetic factors and environmental constraints.Therefore,tree growth process can reflect local climate change.As the Daxing'anling region is located in the northeast of China,it is the highest latitude and permafrost distribution area in China,so the area is very sensitive to climate change and can be used for practical analysis.In this paper,Tahe,Xinlin,Huma and Huzhong in Daxing'anling region are selected as the research area,and the main growing tree species(Larix gmelinii)in the Daxing'anling region are selected as the research object.Record a large amount of climate,environment and other information,and establish the chronology of larch tree ring width in four regions,download the meteorological data(including monthly average temperature?monthly average minimum temperature?monthly average maximum temperature?monthly precipitation)of stations in the Daxing'anling region of the National Meteorological Science Data Center,as well as the GIMMS NDVI data set within 500 m of each sampling point.Then the response difference of Larix gmelinii to climate elements is analyzed.The research is not only important for understanding the growth mechanism of larch trees in the Daxing'anling region.The main research contents of this paper:(1)Four standardized chronologies of Tahe,Xinlin,Huma and Huzhong were established and analyzed after field collection of Larix gmelinii ring samples and analysis of test,de trend and correction.The characteristic values of each chronology are large,which can better translate the local climate,but there are differences among the chronologies.The signal-to-noise ratio of Huma area is smaller than that of the other three areas,indicating that the growth of Larch in humanly affected humanly is stronger than that in other areas.The R value of Tahe,Xinlin and Huma areas is larger than that of Huzhong area,and there are significant differences in tree growth between Huzhong area and other areas.(2)In order to accurately reflect the influence of temperature and precipitation on vegetation coverage in the Daxing'anling Region on a spatial scale,Download the monthly NDVI data of spot-vegetation satellite remote sensing data,and conduct spatial correlation analysis with the climate elements after spline difference,The vegetation coverage in Daxinganling has the strongest correlation with the temperature from May to September(3)There are spatial differences in the response of Larch radial growth to climate factors in Daxinganling region.The tree ring width index in Tahe Area has a significant negative correlation with the average temperature and average maximum temperature in September of last year and the temperature(average temperature ? average maximum temperature)in June and July of that year.Tahe samples were collected at the highest latitude.The larch studied in this paper is in a monsoon climate and is weakly limited by water and nutrients.The influence of latitude change is mainly reflected in heat.The increase of latitude leads to the decrease of tree growth cycle and photosynthetic rate,resulting in the decrease of production.The sampling points in Xinlin area are affected by the terrain,and the precipitation is higher than that in other areas.Excessive precipitation during the growing season leads to insufficient light and slow photosynthetic efficiency of trees.In addition,it will also lead to the increase of soil moisture and the hypoxia of vegetation roots,which will limit the growth of trees.At this time,the temperature becomes the main factor affecting the trees,which is mainly reflected in the acceleration of water evaporation,so as to alleviate the slow growth caused by excessive soil moisture.Therefore,the tree ring width index in Xinlin area has a significant positive correlation with the average minimum temperature in August of last year and August of that year,and with the precipitation in October of last year.There was no significant correlation between tree ring width index and monthly average temperature,monthly minimum temperature and monthly maximum temperature in Huma area.The altitude of Huzhong sample plot is higher.As the altitude increases,the temperature decreases,and the growing environment is cooler than other regions.Temperature is becoming the main influencing factor for radial growth of trees.The tree ring width index in Huzhong area has a significant positive correlation with the temperature in May(average temperature and average maximum temperature),and has a significant positive correlation with the average temperature in June and the average minimum temperature in August.(4)The canopy growth of Larix gmelinii in Daxinganling Region has little spatial difference.NDVI in Tahe Area is significantly positively correlated with the temperature(average temperature? average minimum temperature ?average maximum temperature)in May.There is a significant positive correlation between NDVI and the average minimum temperature in May in Huma area,and there is a significant positive correlation between NDVI and the average temperature in May in Huzhong area.The increase of temperature in May can promote the development of Larch leaves and play an important role in photosynthesis.The correlation difference among regions is due to the different natural environment of the sampling points.The average temperature in July and August and the average maximum temperature in July and August were significantly positively correlated with NDVI in Tahe,Xinlin,huma and Huzhong areas.July and August is the month with the highest temperature and the period with the highest leaf greenness.At this time,leaf cell division is the most vigorous and photosynthesis is relatively strong.NDVI in Tahe and Xinlin areas was significantly positively correlated with the average maximum temperature in August of last year,NDVI in Huzhong area was significantly positively correlated with the average maximum temperature in July,August and September of last year,and with the average minimum temperature in June and July of last year.June to September of last year were in the growth season.At this time,the rise of temperature promoted the growth of leaves,produced nutrients for the growth of trees,and stored the remaining nutrients for the next year.(5)There was a significant positive correlation between tree ring width index and NDVI in July in Huzhong and Huma areas(P <0.01).Using the tree ring chronology of long-time series,the change sequence of NDVI in July in the historical period of the Daxing'anling Region was reconstructed.It is found that there are five decline periods in the NDVI change sequence in July in the historical period of reconstruction,which correspond to the climate change trend,drought and fire records in the Daxing'anling Region.The time series superposition analysis method shows that the reconstructed NDVI sequence is related to ENSO events,and the NDVI value decreases in the first year after El Ni (?) o.