| Larix chinensis, which is endemic in China, belongs to the second grade of national protected plant. It mainly distributes at the Alpine range of Qinling Mountains from 2600m to 3600m above the sea level. Additionally, it is the unique timberline species in Qinling Mountains. This species plays an important role in soil and water conservation, rocks stabilization, and ecological protection. The radial growth of trees is not only influenced by climate change, but also closely related to the site environment. In this study, we conducted a systematic study of the relationship between the radial growth characteristics of L. chinensis and the environmental factors across different sites and time scales (1a,2a,5a and 10a) in the concentrated distribution areas of L. chinensis on both the north and south slope of Taibai Mountain (belongs to Qinling Mountains). Data were collected by sample method and tree ring method, and were analyzed by single factor analysis of variance and stepwise regression analysis. This study revealed the growth regularity of L. chinensis on different time scales and the influence of environmental factors on the radial growth. This study provides a scientific basis for further research on natural regeneration and tending management of L. chinensis in Qinling Mountains. The main conclusions are as follows:1. The result of polynomial regression showed that the radial growth of L. chinensis increased year by year on both the south and north slope, and the amount of radial growth was firstly increased and then decreased in a single year. On the south slope, the largest amount of radial growth occurred in 1904, and on the north slope, it occurred in 1935.2. The polynomial regression of radial growth and time scales revealed that with the increase of the time scale, the amount of radial growth was firstly increased and then decreased with increasing age. The best coefficient of determination (R2) was 0.86 and 0.84 on the north and south slope respectively.3. Gradual regression was applied to detect the relationship between radial growth and environmental factors. The results showed that, on the north slope, the radial growth of L. chinensis were positively correlated with soil thickness on 1-year timescale; the radial growth was negatively correlated with slope and slope positions on 2-year timescale; the radial growth was negatively correlated with slope and positively correlated with rock exposed degree on 5-year and 10-year timescale; the correlation of the radial growth and elevation was not significant. On the south slope, the slope and canopy density of radial growth of L. chinensis were positively correlated on 1-year timescale; the radial growth was negatively correlated with elevation on 2-year timescale; the radial growth was positively correlated with slope gradient on 5-year timescale; the radial growth was negatively correlated with elevation on 10-year time-scale; the slope and bare rock degree were not significantly correlated with the radial growth.4. The average radial growth of L. chinensis of the south slope was significantly higher than that of the north slope in Qinling Mountains. In contrast, the highest amount of radial growth occurred in plot 8 (S, South aspect), and the lowest occurred in plot 2 (N, North aspect); the whole pattern showed as follow:plot 8 (S)> plot 7 (S)> plot 6 (S)> plot 3 (N)> plot 1 (N)> plot 5 (S)> plot 4 (N)> plot 2 (N).5. In general, the characteristics of radial growth was different in different time scales, the amount of radial growth of L. chinensis increased firstly and then more obviously decreased with the increasing timescale. On the 1-year time scale, bare rock, slope and altitude could affect the growth of L. chinensis radial growth; the radial growth was negatively correlated with bare rock and elevation, however, positively correlated with slope. On 2-year,5-year and 10-year timescale, only bare rock was negatively correlated with the radial growth of L. chinensis. |
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