立地类型对张广才岭天然白桦林生态系统碳储量的影响

运用相对生长方程与碳/氮分析方法,测定了我国温带张广才岭7种立地类型(阳坡上、中、下坡位和阴坡上、中、下坡位及谷地)天然白桦林的生态系统碳储量(植被与土壤)及植被净初级生产力与年净固碳量,揭示立地类型对温带天然白桦林生态系统碳库及其固碳能力的影响规律。结果表明:1白桦林植被碳储量((76.28±18.11)—(115.57±5.59)t C/hm~2)在阴、阳坡的上坡位和下坡位显著高于谷地35.1%—51.5%(P0.05),阴、阳坡中坡位高于谷地但差异性不显著(32.5%—33.6%,P0.05);2其土壤碳储量((81.53±6.15)—(181.90±21.62)t C/hm~2)在阳坡各坡位显著高于阴坡中、下部与谷地24.0%—123.1%(P0.05),阴坡上、中部显著高于阴坡下部和谷地36.0%—81.2%(P0.05);3其生态系统碳储量((174.57±20.27)—(282.96±17.92)t C/hm~2)在阳坡各坡位显著高于阴坡中、下坡位与谷地14.1%—62.1%(P0.05),阴坡上、中坡位显著高于阴坡下坡位与谷地19.5%—48.1%(P0.05);4其植被净初级生产力((6.98±1.60)—(9.59±0.69)t hm~(-2)a~(-1))在阴、阳坡上坡位显著高于阴坡中坡位34.2%—37.4%(P0.05),其他4个立地类型高于阴坡中坡位但差异性不显著(8.5%—20.6%,P0.05);5其年净固碳量((3.26±0.74)—(4.56±0.36)t C hm~(-2)a~(-1))在阳坡上坡位显著高于阴坡中坡位39.9%(P0.05),其他5个立地类型高于阴坡中坡位但差异性不显著(9.2%—30.4%,P0.05)。因此,张广才岭天然白桦林的生态系统碳储量及其固碳能力均存在着明显的立地分异规律性,故在评价与管理我国温带白桦林碳汇时应考虑立地类型影响。

Effects of site condition on ecosystem carbon storage in a natural Betula platyphylla forest in the Zhangguangcai Mountains, China

Ecosystem carbon storage (vegetation and soil), net primary productivity (NPP), and annual net carbon sequestration (ANCS) in a natural white birch (Betula platyphylla) secondary forest in the Zhangguangcai Mountains of China were measured using relative growth equations and the carbon/nitrogen analytical approach. Measurements were taken at seven sites, including the top, middle, and lower regions of both the sunlit and shaded slope, and the valley floor. Our goal was to determine the effect of site type on ecosystem carbon stock and carbon sequestration capacity of white birch forests. Carbon storage in the vegetation of the forest ((76.28 ± 18.11)-(115.57 ± 5.59) t C/hm²) was significantly higher (35.1%-51.5%) in the upper and lower regions of the sunlit and shaded slope than in the valley (P<0.05). Vegetative carbon stores were also higher (32.5%-33.6%) in the mid region of the sunlit and shaded sloped than in the valley, but the differences were not significant (P > 0.05), Soil organic carbon stores ((81.53 ± 6.15)-(181.90 ± 21.62) t C/hm²) were significantly higher (P<0.05; 24.0%-123.1%) at the upper, mid and lower region of the sunlit slope than at the mid and lower region of the shaded slope and in the valley. (Soil organ carbon was also significantly higher (36.0%-81.2%) at the upper and mid region than at the lower region of the shaded slope and the valley (P<0.05). Ecosystem carbon storage ((174.57 ± 20.27)-(282.96 ± 17.92) t C hm^-2) was significantly higher (P<0.0514.1%-62.1%) at the three sites on the sunlit slope than at the mid and lower region of the shaded slope and in the valley, and significantly higher (19.5%-48.1%) at the upper and mid region than at the lower region of the shaded slope and in the valley (P<0.05). The NPP ((6.98±1.60)-(9.59±0.69) t hm^-2 a^-1) was the highest at the upper regions of the sunlit and shaded slopes, which were significantly higher (P<0.05; 34.2%-37.4%) than that at the mid region of the shaded slope. NPP was at a medium level at the other four sites, which were higher (8.5%-20.6%) than at the mid region of the shaded slope, where the value was the lowest. The ANCS ((3.26±0.74)-(4.56±0.36) t C hm^-2 a^-1) was the highest at the upper part of the sunlit slope, which was significantly higher (39.9%) than at the mid region of the shaded slope (P<0.05). ANCS was at a medium level at the five remaining sites, being higher (9.2%-30.4%) than at the mid region of the shaded slope, which had the lowest value. Therefore, the carbon storage, NPP, and ANCS in a temperate white birch forest ecosystem exhibited variations among sites. The effects of site type should be considered in the evaluation and management of carbon sinks in temperate white birch forests.