摘要：The Mongolian Plateau,a vital ecological barrier in northern China,is of great importance for studying vegetation dynamics in Mongolia against the background of climate *** studies can enhance our understanding of regional vegetation responses to global warming and contribute to the establishment of a stronger ecological barrier in northern ***,we analyzed the spatial and temporal characteristics of the NDVI(normalized difference vegetation index)in Mongolia using 8 km resolution GIMMS NDVI3g data from 1990 to 2022,along with temperature,precipitation,and elevation *** analysis and correlation methods were used to examine the relationships between the NDVI and temperature,as well as *** results showed four important aspects of these relationships.(1)The NDVI in Mongolia increased significantly from 1990 to 2022 at a rate of 0.0015 yr^(-1)(P<0.05).(2)Mongolia’s NDVI increased from 1990 to 2022 in 60.73%of the *** this total,the area with a significant increase accounted for 31.67%and was concentrated on the eastern and western *** area experiencing a significant decrease accounted for 15.67%and was mainly located on the southwestern edges.(3)The NDVI analysis revealed significant increasing trends in all regions except for those at elevations of 1500-2000 *** greatest rate of increase was observed between 500 and 1000 m,and the increasing trend weakened as elevation continued to increase before gradually becoming significant ***,the NDVI increased significantly across different slopes,and the rate of increase decreased as the slope increased.(4)From 1990 to 2022,Mongolia’s NDVI was mostly negatively correlated with *** occurred over 66.75%of the total land area,with 17.21%of the region exhibiting a significant negative correlation,mainly in the ***,the NDVI demonstrated a positive correlation with precipitation,encompassing 86.71%of the total land *** 4

摘要：青藏高原东部的高山森林是长江上游的重要生态屏障。然而,由于近几十年来持续的高强度采伐,大量的人工种植,以及完全的禁伐等措施,导致树木种类与年龄结构变得相对单一,生物多样性和生态功能都有所下降。为设计有效的森林管理方案,以优化森林结构,提高森林碳汇能力,本研究以四川茂县为研究地点,利用LANDIS-II模型对6种不同强度的森林管理方案(采伐、种植)进行测试,模拟和比较了这些方案与当前管理方案在未来100年间森林地上固碳速率的差异。研究结果表明:(i)与目前的管理方案相比,不同强度的采伐和种植明显改变了森林地上固碳速率;(ii)不同群落对管理方案的反应不同,不同的管理方案对寒温带针叶林和温带针叶林的地上固碳速率有显著的影响(P<0.05),但对阔叶林影响较小;(iii)应综合物种、群落和景观3个层面全面考虑森林管理方案。这些结果说明,在研究地点实施较长的采伐和种植间隔(20年)可以最大限度地提高森林的地上固碳速率。该研究为评估森林管理方案在恢复森林生态和增加碳汇功能的能力,以及为在青藏高原东部地区选择有效的森林管理方案提供了重要参考。

摘要：The permafrost region is one of the most sensitive areas to climate *** global warming,the Mongolian Plateau permafrost is rapidly degrading,and its vegetation ecosystem is seriously *** address this challenge,it is essential to understand the impact of climate change on vegetation at different permafrost degradation stages on the Mongolian *** on the general permafrost distribution,in this study,we divided different permafrost regions and explored the response of vegetation to climate change at different stages of permafrost degradation by the idea of“space instead of time”from 2014 to *** results of the study showed that:(1)Normalized difference vegetation index(NDVI)values showed a decreasing trend,and the proportion of the decreasing region was in the order of sporadic permafrost region>isolated and sparse permafrost region>continuous and discontinuous permafrost regions.(2)The main controlling factors of vegetation growth in permafrost regions are different,air temperature is the main controlling factor of vegetation growth in isolated and sparse permafrost region(r=-0.736)and sporadic permafrost regions(r=-0.522),and precipitation is the main controlling factor of vegetation growth in continuous and discontinuous permafrost region(r=-0.498).(3)The response of NDVI to climate change varies at different stages of permafrost *** the early stages of permafrost degradation,increased land surface temperature(LST)and air temperature favored vegetation growth and increased vegetation cover,whereas increased precipitation impeded vegetation growth;as the permafrost degraded,increased LST and air temperature impeded vegetation growth,whereas increased precipitation promoted vegetation growth.