不同经营措施对毛竹林生态系统净碳汇能力的影响

Effects of Different Management Measures on the Net Carbon Sequestration Capacity of Moso bamboo Forest Ecosystem

【目的】探讨不同经营措施对毛竹林生态系统净碳汇能力的影响,为毛竹林固碳经营提供依据。【方法】利用两因素随机区组设计,排除地形因子等影响,选取施肥量和采伐方式2个因素,每个因素分别设置3个水平,共9个试验组合:大量施肥强度采伐、大量施肥中度采伐、大量施肥弱度采伐、中等施肥强度采伐、中等施肥中度采伐、中等施肥弱度采伐、不施肥强度采伐、不施肥中度采伐和不施肥弱度采伐,研究2010—2013年不同经营措施对毛竹林生态系统净碳汇能力的影响。【结果】2010和2013年两期0~50 cm土层土壤有机碳储量差异显著(P<0.05),而0~10 cm土层土壤有机碳贮量差异不显著(P>0.05);两期植被总碳储量和毛竹碳储量差异均极显著(P<0.01),而两期林下植被总碳储量差异不显著(P>0.05);样地外运输总泄漏量仅占样地内施肥总排放量的7.32%;中等施肥弱度采伐处理与大量施肥强度采伐处理净碳汇量差异显著(P<0.05),中等施肥弱度采伐处理林分的净碳汇量最多,达到64.721 tC·hm^(-2),而大量施肥强度采伐处理林分的净碳汇量最少,为-14.237tC·hm^(-2),说明过度集约经营可能造成毛竹林生态系统的碳排放,而合理经营方式有利于毛竹林生态系统的碳积累;土壤碳库变化量占所有碳库变化量总和的70.99%±12.30%,毛竹碳库变化量占所有碳库变化量总和的23.37%±11.24%,林下植被碳库变化量占所有碳库变化量总和的0.63%±0.37%,运输泄漏量占所有碳库变化量总和的0.40%±0.16%,施肥排放量占所有碳库变化量总和的4.60%±4.85%,其中土壤碳库和毛竹碳库的变化量之和占所有碳库变化量总和的94.36%。【结论】在碳汇项目计量监测时,为了节约成本,可以忽略林下植被碳库和运输泄漏以及施肥引起的温室气体排放。大量施肥强度采伐的毛竹林常规经营方式不仅植被总碳储量增加较少,而且还引起了明显的土壤碳排放,不利于毛竹林生态系统净碳汇量的积累。采用中等施肥弱度采伐的生态经营方式,不仅使植被总碳储量增加最多,同时土壤碳储量也增加最多,是一种最有利于毛竹林增汇减排的经营方式。

【Objective 】Moso bamboo shows excellent carbon sequestration potential and plays an important role in combating climate change. Managing bamboo forests affects not only soil carbon pool,but also vegetation carbon pool,and there comes along with carbon emissions and carbon leakage problems. It is of vital significance to study the comprehensive effect of different management measures on the carbon in bamboo forest ecosystem. 【Method】A two-way randomized blockdesign was adopted to evaluate the effects of different management measures on net carbon sequestration capacity of moso bamboo forest ecosystem during 2010 to 2013. Excluding the effects of topographical factors,we chose fertilization intensity and harvesting model as the two factors,and each of them was set with three levels,coming to a total of nine treatments： high intensities of both fertilization and harvesting,high intensity of fertilization with intermediate intensity of harvesting,high intensity of fertilization with low intensity of harvesting,intermediate intensity of fertilization with high intensity of harvesting,intermediate intensities of both fertilization and harvesting,intermediate intensity of fertilization with low intensity of harvesting model,no fertilization with high intensity of harvesting model,no fertilization with intermediate intensity of cutting,no fertilization with low harvesting model. 【Result】Results showed that between 2010 and 2013 there were no significant differences（P〈0. 05） in SOM storage in 0-10 cm soil layer but differences were significant（P〈0. 05） in SOM storage in 0-50 cm soil layer. Differences of carbon storage by under canopy vegetation was not significant（P〈0. 05） while differences of total carbon storage by vegetation and moso bamboo carbon storage were highly significant（P〈0. 01）. The total transportation leakage from sample area accounted for only 7. 32% of total fertilization emissions inside sample area. Differences of net carbon sequestration were significant（P〈0. 05） between treatments of A2B3（intermediate fertilization intensity with low intensity of harvesting and high retention model） and treatments of A1B1（high fertilization intensity with high intensity of harvesting and low retention model）. The highest net carbon sequestration was 64. 721 tC·hm-2in treatments A2B3,and the lowest was-14. 237 tC·hm-2in treatments A1B1.It implies that excessive intensive management may cause carbon emissions in moso bamboo forest ecosystem,and a reasonable model of management will benefit carbon accumulation in moso bamboo forest ecosystem. The soil carbon pool changes accounted for 70. 99% ± 12. 30% of all carbon pool changes,the moso bamboo carbon pool for 23. 37% ±11. 24%,the under canopy vegetation carbon pool for 0. 63% ± 0. 37%,the transportation leakage for 0. 40% ± 0. 16%,and fertilization emissions for 4. 60% ± 4. 85%. The sum of soil carbon pool changes and moso bamboo carbon pool changes accounted for 94. 36% of all carbon pool changes. 【Conclusion 】When monitoring and measuring carbon sequestration,for cost saving,we may consider to ignore the under canopy vegetation carbon pool and transportation leakage. The study also showed that under the common management measure of moso bamboo forest,i. e.,high fertilization intensity with high harvesting intensity,the total carbon storage by vegetation increases slowly,and soil carbon emission is significant,which goes against the accumulation of net carbon sequestration in moso bamboo forests. We suggest that intermediate fertilization intensity with low harvesting intensity be the best measure to increase carbon sequestration in moso bamboo forests,not only the total vegetation carbon storage increases most,but also soil carbon pool,it is a most favorable model of management for increasing carbon sequestration and reducing the emission of carbon dioxide.