天山北麓新人工绿洲扩张过程中的碳库格局变化与碳库迁移

Changes in the carbon pool pattern and carbon pool migration during the expansion of new artificial oases in the northern foothills of Tianshan Mountains within the last 40 years

基于地面调查数据、气象数据和遥感数据分析了40年来天山北麓新人工绿洲迅速扩张对区域植被和土壤的碳库格局、碳库迁移及碳储量的影响,结果如下:1976-2016年,研究区农田面积占比从3.25%增加到40%以上,沼泽消失,水库干涸,灌丛大幅减少,土壤盐碱化过程停止,裸盐碱地面积40年里减少近70%,新生草地在裸盐碱地上形成;2016年6月植被有效碳储量约为0.122Tg,比1976年下降了15.7%,成为一个弱的碳源;土壤碳库在干旱地区陆地生态系统碳库中占绝对主导地位,1976年研究区(0-60cm)的土壤有机碳储量为7.814Tg,其中耕地仅占4.2%,1996年土壤有机碳储量比1976年减少12.4%,呈明显碳源特征,到2016年,耕地土壤有机碳储量占比超过50%,总碳储量与1996年相比微降1.2%,土壤碳库重新趋于稳定。其中,裸盐碱地土壤碳库在向耕地、灌丛地、草地土壤碳库的迁移过程中贡献了1.265Tg的碳储量增量,草地土壤碳库在向耕地、灌丛地碳库的迁移过程中贡献了0.894Tg的碳储量增量;若维持现有耕地规模不再进行新的垦荒活动,40a垦荒造成的土壤碳库损失可以逐渐恢复并重新形成碳汇效应。

Based on ground survey data, meteorological data, and remote sensing data, this study analyzed the impact of regional vegetation and soil from the rapid expansion of new artificial oases in the northern foothills of Tianshan Mountains in the past 40 years on carbon pool pattern and migration and carbon sequestration.The results are as follows：from 1976 to 2016, the proportion of farmland in the study area increased from 3.25% to more than 40%. As the marsh disappeared, the reservoir dried up, the shrub cover was drastically reduced, the soil salinization process ceased, and the degree of salinization gradually decreased. Finally, new grassland has formed over bare saline-alkali soil, and there has been an approximate 70% reduction in the area of naked saline alkali over the last 40 years. The effective carbon sink of vegetation was decreased by 15.7% compared with that in 1976. The soil（0-60cm） total carbon storage in the study area in 1976 was 7.814TgC, of which, farmland only accounted for 4.2%. In 2016, the farmland soil organic carbon storage accounted for more than 50%, and the total soil carbon storage decreased slightly by 1.2% compared with that in 1996. The soil carbon pool appears to have stopped declining and has achieved a new balance. The soil carbon pools of bare soil salinity increased by 1.265TgC during the transfer of soil carbon to farmland, shrub land, and grassland soil carbon pools. The carbon stocks of grassland soils increased by 0.8934TgC during migration to the farmland and shrub land carbon pool. If the existing scale of cultivated land is well controlled, the loss of the soil carbon pool caused by the 40-year reclamation can be gradually recovered and the carbon sink effect can be re-formed. Human activities are decisive factors that influence the pattern of NPP distribution in the study area. Reclamation activities are generally carried out in arid oasis, especially in the desert intertidal zone around the old oasis during 1976 to 2016. Once oases are reclaimed and farmland extends to desert, a new artificial oasis is dramatically expanded, with a drastic change in water consumption patterns and temporal and spatial distributions, causing significant changes in the ecological environment. The overdraft of groundwater leads to the disappearance of spring overflow and the drying of reservoirs, which has negative effects on the ecological environment in the research area. Therefore, the sustainable development of water resources and future development trend of ecosystem carbon pool feedback in the process of new artificial oasis expansion should be taken seriously and demands further studies.