小兴安岭谷地云冷杉林粗木质残体碳密度特征

以小兴安岭谷地云冷杉林9.12 hm~2固定样地为研究对象,分析粗木质残体(CWD)碳密度的基础特征,揭示其与林分因子和物种多样性的关系。结果表明:(1)谷地云冷杉林CWD碳密度为13.25 t C/hm~2,其中云杉(Picea spp.)、冷杉(Abies nephrolepis)、兴安落叶松(Larix gmelinii)和未知种的CWD碳密度分别为3.59、2.61、3.06和2.85 t C/hm~2。(2)不同腐烂等级下CWD碳密度呈近正态分布,多集中在Ⅱ和Ⅲ等级,分别占总量的42.7%和35.4%。不同径级的CWD碳密度也呈近正态分布,主要分布在30—40 cm和40—50 cm径级上。干中折断、拔根倒、枯立木和干基折断为谷地云冷杉林CWD碳密度的主要存在方式。腐烂等级为Ⅰ和Ⅴ的CWD中,拔根倒的碳密度最高,其他腐烂等级中均为干中折断的碳密度最高。(3)CWD碳密度表现出较强的空间异质性,其随着林分平均胸径、最大胸径和胸高断面积的增加而下降,呈显著负相关关系(P0.05);而与林分密度、多样性指数和均匀度指数均无显著相关性(P0.05)。

Carbon density of coarse woody debris in a spruce-fir valley forest in Xiaoxing'an Mountains, China

Coarse woody debris (CWD) is a substantial carbon pool and a source of nutrients within forest ecosystems. It plays several important ecological roles including the regulation of nutrient cycling and energy flow, as well as habitat provision for many organisms. The CWD carbon density basic character, the relationship between CWD carbon density and stand factors, and species diversity were studied in a large permanent plot (9.12 hm²) of spruce-fir valley forest in Xiaoxing''an Mountains. The results showed that: (1) total carbon density of CWD in the spruce-fir valley forest was 13.25 tC/hm², and the carbon density of CWD for spruce (Picea spp.), fir (Abies nephrolepis), dahurian larch (Larix gmelinii), and unidentified species were 3.59, 2.61, 3.06, and 2.85 tC/hm², respectively. (2) CWD carbon density under different decay classes followed a normal distribution with greater concentrations in classes II and III, which accounted for 42.7% and 35.4% of the total CWD carbon density, respectively. CWD carbon density within different DBH classes also followed a normal distribution, with higher values in the 30-40 cm and 40-50 cm classes. The primary forms of CWD carbon density originated from breakage at the trunk, uprooted blow-down, standing dead, and breakage at the rootstock. Uprooted blow-down had the highest carbon density in decay classes I and V. However, breakage at the trunk had the highest carbon density of other decay classes. (3) CWD carbon density showed a high spatial heterogeneity and it decreased with increasing stand mean DBH, maximum DBH, and basal area (P < 0.05). No significant relationships were observed between CWD carbon density and stand density, diversity index, and evenness index.