The Lagged Effect Of Climatic Factors On Radial Variation Of Plantation Populus Ussuriensis Based On Time Series Analysis

Growth of planted trees is affected by inheritance, climatic factors and silviculture.The climatic factors are more important than others. And growth of trees is affected not only by the climate in this year but also by the climate before. In order to cultivate and manage plantation populus ussuriensis reasonably, effects of climatic changes on plantation populus ussuriensis wood formation have to be ascertained. The climatic signals aren’t easy to be derived from those trees’rings. Furthermore, it is difficult to get long-term and exact climate data. Previous researches are infirmly about climatic factors affecting on tree growth in plantation, and also about climatic factors affecting on wood physical and anatomical properties, especially about climatic factors lagged affecting on wood physical and anatomical properties. With plantation populus ussuriensis being the object, the lagged effect of climatic factors on radial variation of plantation populus ussuriensis was investigated in this paper.First the index of the anatomical characteristics and physical characteristics of the plantation populus ussuriensis wood were standardized by rejected the influences of the genetic factors, cultivation measures and site conditions, then established standard index attached to the climatic factors.Second, the lagged effects of climatic factors on radial variation of plantation populus ussuriensis were studied by Granger causality tests of time series analysis, the climatic factors included the mean temperature, relative humidity, precipitation, sunshine percentage, ground temperature, lowest ground temperature and highest ground temperature. Finally, the paper based on populus ussuriensis wood characteristics index time series and the largest lagged effected climatic factors time series to establish the VAR model, and uesd impulse response function analysis and variance decomposition to analyze.Through the Grainger causality test we found that hysteresis of each of climate factors change affecting populus ussuriensis structures properties were significant and lags term of each kinds of climate factors were different.Mean temperature and precipitation were the most significant climatic factors. Hysteresis of mean temperature in June, relative humidity in March, precipitation in October, sunshine percentage in October and ground temperature in September were most significant, secondly were the highest ground temperature in January and mean temperature in March. The lagged effect of climatic factors on ring width, early wood vessel wall to lumen ratio, early wood vessal density, early wood vessal length to width ratio, late wood fiber wall thickness, late wood fiber length and vessal proportion were weak.The paper based on populus ussuriensis wood characteristics index time series and the largest lagged effected climatic factors time series to establish the VAR model, and uesd impulse response function analysis and variance decomposition to analyze. Impulse response function analysis shows that the lagged effect of climatic factors on radial variation of plantation populus ussuriensis showed a shock state. The maximum positive response and the minimum negative response more appear in the first nine lag period.And the lagged effect will gradually disappear with the increasing lag time. Variance decomposition shows that the contribution rate of lagged effect of climatic factors on radial variation of plantation populus ussuriensis was from24%to58%. The contribution rate of mean temperature in June to late wood fiber wall to lumen ratio and highest ground temperature in January to early wood density were the minimum, about24%. The contribution rate of percentage in October to late wood vessal wall to lumen ratio was the maximum, about58%.The result of this paper will provide a scientific basis and practical significance for oriented cultivation of plantation populus ussuriensis.