林龄和气候变化对三峡库区马尾松林蓄积量的影响

Effects of stand age and climate change on the volume of Pinus massoniana forests in the Three Gorges Reservoir Area of central China

【目的】林龄增长和气候变化是影响森林蓄积量变化的关键因素,研究这两种因素对区域尺度森林蓄积的影响具有重要意义。【方法】本文基于生态过程模型(3-PG)、森林资源规划设计调查数据及3种未来气候情景(BS、RCP4.5和RCP8.5),量化了林龄和气候变化对三峡库区马尾松林蓄积的影响。【结果】2009-2050年林龄促使三峡库区马尾松林蓄积年均增长2.60×106 m^3/a或2.60 m^3/(hm^2·a);而气候变化对蓄积生长的促进作用较小,年均增量为1.70×10^5~2.00×105 m^3/a或0.17^0.20 m^3/(hm^2·a),相当于林龄影响的6.55%^7.67%。林龄和气候变化对马尾松林蓄积生长的促进作用在三峡库区中部最强,而在库区南部最弱。林龄促进马尾松林单位面积蓄积年均增长最高和最低的地区分别是万州区和巴南区,对应值为4.54和1.17 m^3/(hm^2·a)。气候变化对开州区单位面积蓄积年均增长的促进作用最高,为0.40 m^3/(hm^2·a),而对涪陵区的促进作用最低,为0.03 m3/(hm^2·a)。【结论】林龄和气候变化均促进马尾松林蓄积生长,其共同作用将使万州区和开州区马尾松林单位面积蓄积年均增量最高,而使巴南区蓄积年均增量最低。未来需重点关注巴南区马尾松林生长,通过加强抚育管理、调整林龄结构以维持区域森林资源增长。

[Objective]Both stand age and climate change are crucial factors influencing forest volume dynamics,and it is important to investigate their effects on forest volume on a regional scale.[Method]Based on an ecological process model(3-PG),data from a forest resource planning and design survey and three future climate scenarios(BS,RCP4.5,and RCP8.5),this study quantified the effects of stand age and climate change on the volume growth of Pinus massoniana forests in the Three Gorges Reservoir Area(TGRA)of central China.[Result]Stand age was predicted to increase the annual average volume of the Pinus massoniana forests by 2.60×106 m^3/year or 2.60 m^3/(ha·year)in the TGRA during 2009 to 2050.While the effect of climate change was less pronounced than that of stand age,an annual volume increment of 1.70×10^5-2.00×105 m^3/year or 0.17-0.20 m^3/(ha·year)only accounted for 6.55%-7.67%of the effect of stand age.The effects of both stand age and climate change on volume growth in Pinus massoniana forests were predicted to be the strongest in the central part and the weakest in the southern part of the TGRA.The Wanzhou District was predicted to present the highest annual average increment of volume per hectare(4.54 m^3/(ha·year))owing to stand age;while Banan District,the lowest value(1.17 m^3/(ha·year)).The promoting effects of climate change on volume growth were predicted to be the highest in Kaizhou District(0.40 m^3/(ha·year));the lowest in Fuling District(0.03 m^3/(ha·year)).[Conclusion]Both stand age and climate change are predicted to enhance the volume growth of the Pinus massoniana forests,and their combined effects would most increase the annual average volume increment per hectare in Wanzhou and Kaizhou Districts and least in Banan District.Studies are required to focus on the growth of Pinus massoniana forests in Banan District in the future through strengthening of forest management and adjustment of the forest age structure to maintain the development of regional forest resources.