湘南典型次生林粗木质残体生物量、碳储量和养分特征

Biomass, carbon storage and nutrient content of coarse woody debris in secondary-growth forests in southern Hunan

对九龙江森林公园次生常绿阔叶林粗木质残体(CWD)进行量化研究,了解亚热带典型次生林CWD的本底数据。以九龙江森林公园典型天然次生林中的6个20m×20m的标准样地为对象,调查并分析样地内不同分解等级CWD的生物量、碳储量和养分特征变化。九龙江森林公园亚热带典型次生林的CWD储量在2.8—30.4t/hm^(2)之间,碳储量在6.10—6.75t/hm^(2)之间,大量营养元素(N、P、K、 Ca、 Mg)含量相对稳定,化学计量变化不显著,微量营养元素中Pb与Cd元素含量随着分解等级的增加而增加。九龙江森林公园亚热带典型次生林的CWD储量在亚热带常绿阔叶林中处于中等水平,CWD主要以分解中后期的倒木为主,反映出该次生林处于中幼龄林阶段,具有较高的碳储量,养分含量相对稳定,并表现出Pb与Cd在CWD中积累的现象,在中度分解和重度分解的CWD中Pb含量分别增加了62.65%和69.88%,Cd含量则分别增加了33.33%和100%,其内在机理有待进一步深入研究。研究结果有助于进一步了解CWD如何参与森林生态系统养分循环、重金属积累等生态过程,比较不同林分干扰历史下CWD储量、分布及养分特征的异质性,补充CWD参与碳循环和碳平衡过程的本底数据,为亚热带典型次生林的保护与可持续经营提供了科学依据。

In order to understand the structural and function roles played by coarse woody debris(CWD) in typically subtropical secondary-growth forests, the biomass, carbon storage and nutrient content of CWD were investigated in Jiulongjiang Forest Park, southern Hunan, China. The result showed the CWD biomass ranged from 2.8 t/hm^(2)to 30.4 t/hm^(2)and the carbon storage ranged from 6.095 t/hm^(2)to 6.751 t/hm^(2)in the study sites. The contents of other nutrients(N, P, K) were relatively stable, and the stoichiometric changes were not significant. The contents of Pb and Cd increased with the increase of decay classes. The CWD storage of the typical subtropical secondary forest in Jiulongjiang Forest Park was at a middle level when compared to the existing cases of the subtropical evergreen broad-leaved forests elsewhere. The CWD was mainly composed by logs in the medium-and late-decay, which reflected this forest was in the stage of young growth forest, with high carbon storage, relatively stable nutrient content. In the medium-and late-decay, the Pb content increased by 62.65% and 69.88% respectively, the Cd content increased by 33.33% and 100%, respectively, the internal mechanism of the significant accumulation of Pb and Cd in CWD needed to be further studied. The results could help us understand how CWD participates in the ecological processes such as nutrient cycling and heavy metal accumulation in forest ecosystems, help to compare the heterogeneity of CWD reserves, distribution and nutrient content under different forest disturbances history, supplement the background data of CWD′s participation in the carbon cycle and carbon balance process. The results provide scientific basis for the protection and sustainable management of subtropical secondary forests.