| The Shennongjia Nature Reserve in Western Hubei Province with typical fragile ecological environment is an area which is sensitive to climate change.Abies fargesii is the typical coniferous species in this area.Well-replicated Abies fargesii tree-ring width chronologies at different altitude were developed to investigate their radial growth response to climate variables using different methods of analysis,including correlation analysis between different chronologies,analysis of regional climatic characteristics,correlation analysis between different-altitude chronologies and monthly factors(e.g.mounthly mean temperature and total precipitation),correlation analysis between different-altitude chronologies and other growing season indicators(e.g.cumulative temperature and continuous days).All of these analyses were aimed to investigate the similarities and differences of responses to climate among different-altitude Abies fargesii chronologies.The main conclusions of this study are as follows:(1)The correlation among different-altitude standard chronologies are all significantly positive.The highest correlation occurred between the middle-altitude chronology and high-altitude chronology,and the lowest correlation occurred between the high-altitude and low-altitude chronology,which meant that the closer the altitude,the higher the correlation.(2)The averaging annual mean temperature in Shennongjia Nature Reserve was 17.4?.Although the change of annual mean temperature in recent 61 years was U-shape,the overall trend was declining with the decrease rate 0.01?/10a,The averaging annual total precipitation was 1086.4mm,and the trend of annual total precipitation in recent 61 years was declining at the decrease rate 16.1mm/10a.(3)The responses of different-altitude chronologies to monthly climate factors(e.g.monthly mean temperature and total precipitation)showed both similarities and differences.Correlation analyses showed that all the tree-ring width chronologies were positively correlated to mean temperature of April and total precipitation of prior October and prior December,and negatively correlated to total precipitation of September,all of which were at 0.05 significant level.As the altitude increased,grow-response was more sensitive to mean temperature of April and total precipitation of September,but less sensitive to total precipitation of prior October and December.(4)The responses of different-altitude chronologies to other growing season factors(e.g.cumulative temperature and continuous days)showed both similarities and differences.Results showed the highest positive correlation was at 6.6?,meaning that the sensitive temperature threshold for photosynthesis of Abies fargesii was around 6.6?.Defined this way,the growing season started on May 21st and ended on September 20th,lasting about 123 days.Besides,the results showed different characteristics according to altitude gradient.The high-altitude chronology showed the highest positive correlation at 6.0 ?,with the growing season started on May 22nd and ended on September 19th,lasting about 121 days.The middle-altitude chronology showed the highest positive correlation at 6.6 ?,with the growing season started on May 21st and ended on September 20th,lasting about 120 days.The low-altitude chronology showed the highest positive correlation at 7.6?,with the growing season started on May 23nd and ended on September 18th,lasting about 119 days.As a whole,the sensitive temperature threshold for photosynthesis decreased with the increase of altitude.However,the continuous days of growing season were little changed,might due to some other factors,such as light intensity,etc.(5)In general,the chronology characteristics and their responses to climate factors(e.g.mounthly mean temperature,monthly total precipitation,cumulative temperature and continuous days of the growing season)of Abies fargesii differed on the same slope with finite distance.However,there were more similarities than differences. |
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