Radial Growth Of Trees In Ledum-Larix Gmelinii Forest In Response To Climatic Factors

In the present global warming,the climate characteristics of our country has changed significantly,as early as 1951-2004 average annual temperature has very obvious warming trend.Located in the high latitudes of China,the Daxing’anling is the most sensitive zone for climate change in China.The ground zone vegetation is mainly Larix gmelinii forest with a homogenous species composition and tree growth that is very sensitive to climate.Therefore,in this thesis,the Ledum-Larix gmelinii forest in the Daxing’anling area was used as the research object,and sample plots were set up in the Chaocha forestry field in Genhe City to collect Larix gmelinii sample cores and establish a chronology of the annual ring width of Larix gmelinii at different diameter levels.The M-K test and sliding t-test were used to test for mutations in temperature and precipitation in the study area,and to investigate the correlation between Larix gmelinii and climatic factors before and after the mutations.Using Pearson correlation analysis and sliding correlation analysis,we studied the relationship between radial growth and climatic factors of different diameter classes of Larix gmelinii to reveal the influence of climate change on the growth of different diameter classes of Larix gmelinii in the Daxing’anling Mountains.The main findings are as follows:(1)The climate of the study area between 1969 and 2020 had a sudden warming change in 1986,temperature showed an upward trend,and the relative humidity shows a decreasing trend,and the study area as a whole was in a semi-humid state.(2)Temperature is the main factor affecting the growth of Larix gmelinii in the Daxinganling area,and the appropriate increase in temperature is beneficial to the growth of small-diameter Larix gmelinii;however,as the climate warms,the correlation coefficient between small-diameter Larix gmelinii and temperature is generally higher than that of large-diameter Larix gmelinii,while the precipitation is lower than that of large-diameter Larix gmelinii.The microclimate difference makes large-diameter Larix gmelinii more sensitive to drought,while small-diameter Larix gmelinii is more sensitive to temperature.(3)Before the mutation(1969-1986),the radial growth of Larix gmelinii had no significant changes in precipitation and mean temperature,but had a significant positive correlation with the maximum temperature in July of the current year,and a significant negative correlation with the relative humidity in September,October and September of the previous year.There was a significant negative correlation between Larix gmelinii and the minimum temperature in September last year.(4)After the mutation(1987-2020),the radial growth of Larix gmelinii had significant changes in climate factors: the radial growth of Larix gmelinii had a significant positive correlation with the average temperature and precipitation during the growing season;The mean minimum and maximum air temperature in February of the same year were negatively correlated with small diameter Larch,and the mean maximum air temperature in March of the same year was negatively correlated with large diameter Larch.In terms of relative humidity,there was a significant negative correlation between Larix gmelinii with large small diameter in winter,it is mainly suppressed by winter temperatures more prominently.