Response Of Pinus Tabulaeformis Forests To Climate Change Based On Tree-ring Data In Songshan, Beijing, China

In order to find the relationship between arborous layer productivity and the climatic factors,sixteen Pinus tabulaeformis plots were chosen as study area in the natural forests and plantations of Songshan Nature Reserve. The arborous layer biomass and productivity in past 33 years were counted by measuring ring width of the natural forests and plantations.To explore the relationship between the climate change and NPP.correlations between productivity and climatic factors(including temperature and precipitation)were analyzed,and so that to provide references for forest management under climate change.Based on the principles of dendrochronology.tree ring width chronologies were constructed and the relationship between the climate change and radial growth of two diameter classes of natural Pinus tabulaeformis were analyzed. The results showed that:(1)During the past 33 years,the annual mean productivity of nature forests were 3.72t/hm2/a,arborous layer biomass increased from 50.52t/hm2(1980) to 173.23t/hm2(2013);and the annual mean productivity of plantations were 3.23 t/hm2, arborous layer biomass increased from 7.74t/hm2(1980) to 114.49t/hm2(2013).(2)Productivity of natural forests were significant positive correlated with the temprature in the August of previous year and in the February of current year.The natural foressts productivity also positive correlated with the precipitation in June significantly. Productivity of plantations were positive correlated with the temprature in January and February significantly;and significant positive correlated with the precipitation in May.Results showed that the productivity of the natural forests were mainly effected by the annual mean temperature and the precipitation from May to July;the mean temperature from January to April was the dominant factor of the plantations productivity.(3)The sensitivity of small DBH trees were higher than the large one and the chronologies quality of the small DBH trees was also superior to large trees; the quality of RES chronology was superior to STD chronology for all the two groups. Different diameter classes showed different relationship with the climate change:The temperature and precipitation in current January and February were the mainly impact factors for all the two groups;besides,the radical growth of the large DBH trees also positive correlated with the precipitation in previou August and negative correlated with the temperature in current May and June; The increase of precipitation in previous November will be the limiting climatic factor to the radical growth of small DBH trees.