Effects Of Stand Age And Climate On Organs Biomass Of Several Typical Pine Forests In China

Forest biomass is an important and direct indicator, which embodies the forest production potential and carbon sequestration potential, is also the foundation of material circulation and energy flow in ecosystems. Investigations on the determinants of forest biomass is not only important for seeking the mechanisms how ecosystems work, but also to provide scientific evidence for the development of long-term effective control measures of the forest land productivity and the selection of carbon sink forest. This research focuses on Pinus massoniana forests, Pinus tabulaeformis forests and Pinus forests in China. Field measurement data on 136 Pinus massoniana forest stands,136 Pinus tabulaeformis forest stands and 439 Pinus forest stands have been collected from published literatures. Eight climatic indices, including mean annual temperature (MAT,℃), mean annual precipitation (MAP, mm), mean annual bio-temperature (BT, ℃), warmth index (WI, ℃), coldness index (CI, ℃), mean annual potential evapotranspiration (PE, mm), mean annual actual evapotranspiration (ARET, mm) and humidity index (HI, mm/℃), are selected to describe the climatic effect on organs biomass. Simple linear regression and multiple statistical analyses are conducted to establish the relationships among organs biomass, stand age and climate. We also obtain the dominant climatic factors and analyze the effects of stand age and climate on organs biomass for each forest type. The main results are listed as following:(1) For Pinus massoniana forests, the determination coefficients (R2) of the relationships among stand age and biomass of stem, branch, leaf, aboveground, belowground are 0.470,0.309,0.002,0.535 and 0.477 respectively; For Pinus tabulaeformis forests, the determination coefficients are 0.587,0.602,0.117,0.639 and 0.619; For Pinus forests, the determination coefficients are 0.292,0.297,0.022, 0.330 and 0.416. The accuracy of organs biomass prediction is low when merely considering stand age.(2) For Pinus massoniana forests, the maximum determination coefficients (R2) of the relationships among climate and biomass of stem, branch, leaf, aboveground, belowground are 0.155,0.136,0.068,0.255 and 0.230 respectively; For Pinus tabulaeformis forests, the maximum determination coefficients are 0.146,0.103, 0.024,0.127 and 0.057; For Pinus forests, the maximum determination coefficients are 0.111,0.003,0.123,0.082 and 0.008. The accuracy of organs biomass prediction is low when merely considering stand age. There are differ significant correlation between organs biomass of different forest types and different climate factors, and mostly not significant correlation. The accuracy of organs biomass prediction is low when merely considering climate.(3) For Pinus massoniana forests, the determination coefficients (R2) of the relationships among stand age, climate and biomass of stem, branch, aboveground, belowground are 0.578,0.405,0.652 and 0.612 respectively; For Pinus tabulaeformis forests, the determination coefficients are 0.683,0.658,0.117,0.718 and 0.619; For Pinus forests, the determination coefficients are 0.592,0.358,0.123,0.586 and 0.476. Thus taking both stand age and climate into consideration could predict organs biomass much better than merely considering stand age or climate.(4) Stand age influence on organs biomass is generally higher than climate factors, its explanatory power between 11.7% and 63.9%. Among all the climatic factors considered, MAP is the dominant climatic factor of Pinus massoniana stem, Pinus massoniana aboveground, Pinus massoniana belowground, Pinus tabulaeformis stem, Pinus tabulaeformis aboveground, Pinus stem, Pinus aboveground and Pinus belowground; ARET is the dominant climatic factor of Pinus tabulaeformis branch, Pinus stem, Pinus branch and Pinus aboveground; MAT is the dominant climatic factor of Pinus massoniana branch; WI is the dominant climatic factor of Pinus leaf.In this study, the accurate prediction equations for organs biomass are established, and the dominant factors determining organs biomass of forests are selected. This research is of great value in improving the prediction precision of forest biomass, seeking the mechanisms of forest biomass accumulation, restoring the degraded forests and planning forestation for carbon sink.