呼伦贝尔沙地樟子松生产力及其对气候因子的响应

Productivity of Mongolian Pine(Pinus sylvestris var.mongolica)and Its Response to Climate Change in Hulunbuir Sandy Land

[目的]森林在减缓温室气体浓度和气候变化方面发挥着巨大作用,研究不同密度下林分生产力及其对气候的响应有助于森林生态系统的功能评估及适应性管理。[方法]本研究利用树木年轮学方法得到了呼伦贝尔沙地不同密度(用林分胸高断面积表示)的天然樟子松林净初级生产力,并结合气象因子分析其对温度、降水及干旱指数的响应。[结果]表明:胸高断面积为8.83、21.94、24.28、32.36和34.9 m^(2)·hm^(−2)的樟子松林的多年平均净初级生产力分别为1.17、2.99、3.55、4.69和4.86 t·hm^(−2)·a^(−1),随样地密度增加而增加;高密度樟子松林净初级生产力与上年7月和当年9月平均气温及平均最高气温显著正相关(P<0.05);5月降水是天然樟子松林净初级生产力的关键限制因子,所有密度林分的净初级生产力均与当年5月降水显著正相关(P<0.05);自上年11月至当年7月,净初级生产力与帕默尔干旱胁迫指数(PDSI)的相关系数随林分密度增加而减小,表明林分竞争的增加导致了净初级生产力对PDSI敏感性的降低。[结论]林分密度对呼伦贝尔沙地天然樟子松的净初级生产力及其气候响应存在明显影响,密度调整可能是气候变化下森林适应性管理的关键措施。

[Objective]Exploring the stand productivity in the forests with different densities and its response to climate change is helpful for the functional assessment and adaptive management of forest ecosystems.[Method]In this study,the net primary productivity(NPP)of natural Mongolian pine(Pinus sylvestris var.mongolica)forests with different densities(indicated by stand basal area)in the Hulunbuir Sandy Land was obtained by dendrochronology method,and its response to temperature,precipitation and drought index was analyzed.[Result]The results showed that the annual average NPP with stand basal area of 8.83,21.94,24.28,32.36,and 34.9 m^(2)·hm^(−2) were 1.17,2.99,3.55,4.69,and 4.86 t·hm^(−2)·a^(−1),respectively,which indicated that NPP increased with the increase of stand density.The NPP in the high-density forests were significantly positively correlated with the average temperature and average maximum temperature in July of previous year and September of the current year(P<0.05).The precipitation in current May was the key limiting factor for the NPP.NPP in all stands was significantly positively correlated with the precipitation in current May of that year(P<0.05).From previous November to current July,the correlation coefficient between NPP and Palmer Drought Severity Index(PDSI)decreased with increasing stand density,which indicated that the increase in stand competition led to the reduction of the sensitivity of NPP to PDSI.[Conclusion]Stand density has a significant impact on the NPP of natural Mongolian pine forest,as well as NPP response to climate in Hulunbuir Sandy Land.Density management may be a key measure for forest adaptive management under climate change.