冰雪灾害对中亚热带人工针叶林净初级生产力的影响

The effects of ice storms on net primary productivity in a subtropical coniferous plantation

结合中亚热带江西千烟洲人工针叶林2005、2008和2011年3次树木清查数据以及树木相对生长方程,比较了2008年1月南方冰雪灾害前后的NPP,评价了森林生态系统灾后的恢复能力。结果表明:乡土树种马尾松(Pinus massoniana)与杉木(Cunninghamia lanceolata)比外来树种湿地松(Pinus elliottii)抗灾害能力强;在个体水平上,胸径(D)较大的树木抗灾害能力较差。灾后马尾松与杉木的D增长率降低,而湿地松增大。冰雪灾害导致大量碳(10.44 t C/hm2)从乔木层碳库转移到死生物量碳库,占乔木层碳储量的18.28%。灾前NPP和碳利用效率(CUE)分别为736.23 g C m-2a-1和0.41;灾后经过近4年的恢复,NPP和CUE分别为683.08 g C m-2a-1和0.38。

In the context of global warming, climate change will increase the occurrence probability of extreme weather events such as severe droughts and ice storms. In recent years, the increasing frequency of ice storms in southern China has prompted us to study the impact of these weather events on the net primary productive （NPP） of forest ecosystem, particularly plantations, which are more sensitive to extreme weather events. Severe ice storms during mid-January and mid- February 2008 in southern China provided an opportunity to study the effects of this disturbance on the NPP of a plantation. We used data from field inventories and eddy covariance observations to evaluate the direct impact of the ice storms and the post-ice storm recovery in a subtropical plantation at Qianyanzhou, Jiangxi Province. We developed biomass allometric equations for the three major plantation species; estimated the NPP before and after the ice storms by combining the forest inventories for 2005, 2008, and 2011; and evaluated the recovery ability of the ecosystem. We obtained the following results. （ 1 ） The optimal biomass model developed from our survey data was a power function model. The biomass model fit for slash pine （ Pinus elliottii ） and Chinese fir （ Cunninghamia lanceolata） was improved after adding tree height as a further independent variable, whereas that of Masson pine （Pinus massoniana ） was not. Compared to the biomass data collected from other stands calculated using allometric equations, the biomass calculated using the optimal model was closest to the observed values. （2） The exotic species slash pine was more severely species Masson pine and Chinese fir; this difference can be attributed to damaged by ice storms compared with the native the specific characteristics of the slash pine. A large number of damage to storm damage of broadleaved trees regenerated in the study plot after the ice storms. （3） At the individual level, the extent trees varied with the stem diameter at breast height （D） ： trees with a larger D were more susceptible to ice than tress with a smaller D. Prior to the ice storms, the D growth rate of Masson pine and Chinese fir increased with increasing D class （the maximum values were 1.9 and 0.8 cm/a, respectively）, whereas the D growth rate of slash pine increased with decreasing D class, with a maximum value of O. 1 cm/a. Post-ice storm, the relationships between the D growth rate and D class of the three species were exactly reversed. （4） The carbon （C） density of living trees in tree layer was 57.10 t C/hm2 pre-ice storm, but decreased to 46.66 t C/hm2（a reduction of --10.44 t C/hm~ or 18% of the original living tree biomass pool） post-ice storm. The NPP was 736 g C m-2 a-1 pre-ice storm, and the carbonuse efficiency （the ratio of NPP to gross primary production, CUE） was 0.41. After nearly 4 years of recovery, the NPP was 683.08 g C -2 -1 m a and the CUE was 0.38. Furthermore, the biomass C storage of living trees had increased to 54.38 t C/hm2.