东北地区两种主要造林树种生态系统固碳潜力

自从1980年,我国开展了一系列举世瞩目的造林工程,增加了森林面积3亿hm2。造林后生态系统有机碳库的微小变化都显著影响大气碳库,对全球碳素循环和平衡起着重要的作用。研究了退耕还林不同年限长白落叶松林的植被、凋落物和土壤碳库的变化规律,并且选择可比性较强的退耕还红松林、退耕还草和红松原始林作为参照,分析总结了退耕还林对生态系统储碳能力和碳循环的影响。结果表明,退耕还林后生态系统的植被、凋落物碳储量随退耕还林年限增加而增加:从退耕3a到33a,植被和凋落物碳储量分别从4.134、0Mg/hm2增加到74.11、11.31Mg/hm2。土壤碳储量则是先降低再增加:在还林初期的12a里,土壤碳密度降低到最小量75.87Mg/hm2,随后逐渐恢复和积累,21a后,土壤碳密度恢复到农田的水平84.28Mg/hm2,随后土壤碳密度出现净积累。在长白山地区,退耕3、12、22a和33a长白落叶松、33a红松生态系统的碳储量分别是81.778、114.488、130.004、187.255Mg/hm2和178.580Mg/hm2。长白落叶松的固碳能力随林龄而增加,两种主要造林树种(长白落叶松和红松)的生态系统的固碳潜力没有显著差异。长期来看(如250a),生态系统碳库存的能力非常大(269.57Mg/hm2)。这种状况表明,在长白山地区退耕还林后,生态系统长期来看是一个可观的碳汇。

Carbon sequestration potential of ecosystem of two main tree species in Northeast China

Since 1980,China has launched large-scale afforestation campaigns with an area of 30 million hectares.Even if afforestation only slightly affects ecosystem C stocks at the local level,it could have a significant effect on the global C budget if enough agricultural land is converted.We studied the change of C stock in biomass,forest floor and soil and C circle after the cropland was converted to larch(Olga Bay Larch,Larix olgensis Henry)forest in seven stands in afforestation chronosequence, and made comparisons of ecosystem carbon change with adjacent Korean pine (Pinus koraiensis Sieb.et Zucc),pasture,and cropland.An adjacent 250-year-old natural forest was included as a control for the possible long-term carbon storage in Changbai Mountmn,northeast China.The findings are that:the C stocks in biomass and forest floor both increased over stand age;from the third year to the 33~(rd) year of cropland-to-forest conversion program,the C stock changed from 4.134 to 74.11 MS/hm~2 for the biomass,and from 0 to 11.31 Mg/hm~2 for the forest floor.Soil carbon density initially decreased during the first 12 years to a minimum level of 75.87 Mg/hm~2.Then it gradually recovered and started to accumulate and reached a level of 84.28 MS/hm~2 in the 21~(st) year.as high as that of cropland.The ecosystem C stocks were 81.778,114.488,130.004,187.255 and 178.580 Mg/hm~2 after afforestation of 3、12、22、33 years for larch and 33 years for Korean pine.The carbon sequestration of larch increased over afforestation time.There was no significant difference in the ecosystem C stocks between larch and Korean pine.The high ecosystem carbon contents (269.57 Mg/hm~2)in the 250-year-old afforested stand suggest that the afforestation ecosystem in Changbai Mountain area may serve as potential sinks for C in the long run.