Respones Of Abies Faxoniana Of Tree-ring To Climate Factor In Sub-Apline In Western Sichuan

Sub-Alpine area in Western Sichuan with typical fragile ecological environment is anature complex with world, typical and respresentative significance and is sensitive to climatechange. Sub-Apline dark coniferous forest is dominant ecosystem in sub-Alpine area. As animportant approach to climate reconstruction and an establishment of tree responses toenvironmental factors, tree-ring stable isotope technique has been widely used in the field ofclimate change due to its advantages of accuracy for cross-dating, well continuity,high-resolution and high sensitively to environmental changes.By sampling tree-ring of Abies faxoniana collected from Sub-Apline forests in WolongSichuan in2010, the stability of the tree-ring width and tree-ring carbon stable isotopecomposition(13C) polynomial are fitting to the trend extracted high-frequency sequence. Abiesfaxoniana tree-ring width and tree-ring carbon stable isotope composition (13C) and theclimate factors(temperature, precipitation and humidity) by establish the relational model usingcorrelation analysis, multiple regression analysis and other statistical methods. We thenexpounded responds of Abies faxoniana to climatic change (claimte warming and reduction ofprecipitation), which revealed the essence of Abies faxoniana tree-ring width and tree-ringcarbon stable isotope composition and climatic factors, and Abies faxoniana tree growth ofclimate factor changes provide an important basis for predicting future climate change. Themain conclusions of this study are as follows:1) The annual average temperature was13.71℃, the climatic trend rate was0.15℃/10a-1（P＜0.05）; the annual rainfall was895mm with bigger annual precipitation fluctuation, andthe climate inclination rate was-21.65mm/10a-（1P＜0.05）in Wolong during1955to2009. Thelast55years’ climate change indicated that the temperature had a significant upward trend(P<0.05), while the precipitation had a slight downward trend reaching a significant level (P<0.05). 2) There were significant differences between three different altitudes of Abies faxonianatree ring width trend. But at the same altitude, the changing rate of Abies faxoniana tree ringwidth was similar. In especifically, the annual ring width decreased with altitudes’ dropping inthe same year, and the upper limit of forest ceiling ring width index was higher, while thelower limit was relatively low. The tree-ring chronology characteristic drops with rising ofaltitude, and the minimum low-elevation forests ring chronologies have high quality andsensitivity. Meanwhile, the tree-ring width of Abies faxoniana was positively correlated withthe mean monthly temperature in current February(P <0.05).3) The carbon stable isotope series(1904~2009) varied from-23.33‰to-26.31‰withthe average value of-24.91‰and the coefficient of variation was from-0.011to-0.038, whichshowed strong first-order autocorrelation. The tree-ring carbon stable isotope compositiontrends were different with altitudes, while they were similar at the same altitude which had agood indication to environmental changes, showing that Abies faxoniana tree rings were stablein Wolong Sichuan. The tree-ring DS values showed a significant positive correlation to themean monthly temperature of the January in the previous year, and the February and Novemberof the current year(P <0.05). The most sensitive variation to the DS values was the wintertemperature.4) The tree-ring width of Abies faxoniana of lower limit (elevation2750m) waspositively correlated to the mean monthly temperature in current February and the meanmonthly relatively humidity in the previous year July(P<0.05). The most sensitive variable tothe tree-growth values was the winter temperature. Howere tree-ring width of higher limit(elevation3150m)was positivly correlated to the mean monthly temperature in currentFebruary, April and in the previous year July(P<0.05). The most sensitive variable to thetree-growth values was the spring temperature. Altitude central area(elevation2950m) was arelatively suitable climatic condition, where Abies faxoniana trees width growth did not changesignificantly. 5) The tree-ring DS values of lower limit showed a significant positive correlation to themean monthly temperature of the December of the current year and the mean monthlyrelatively humidity of the August in the previous year(P<0.05). The tree-ring DS values ofhigher limit showed a significant positive correlation to the mean monthly temperature of theApril of the current year and the mean monthly relatively humidity of theAugust in theprevious year(P<0.05). The tree-ring DS values of altitude central area showed a significantpositive correlation to the mean monthly temperature of the February and November of thecurrent year and the January and November in the previous year(P<0.05). The most sensitivevariable to the DS values was the winter temperature, and Lag effectD.Growth of forest trees are mainly confined by temperature constraints in Sub-Alpine,Western Sichuan which clarified the relationship between the growth of trees and theenvironment, from the perspective of the biological basis. Rising of winter temperature wasconducive of the advance of the growing season, resulting in the growth of plants strongdrought resistance weakened; meanwhile, the constructive species Abies faxonianadependended barely on rain, which was conducive to the survival of plants, and was a maintainof the stability of subalpine dark coniferous forest plant communities. Our research filled thedisadvantage of research in Qinghai-Tibeat plateau with few meteorological station and shortobservation period and provided a basis for the study of growth of Abies faxoniana response toclimate change.