新疆哈巴河桦木属湿地3600年以来的植被变化和人类活动

Vegetation changes and human activities in the Betula wetland of Habahe in Xinjiang, China since 3600 cal a BP

湿地是水陆相互作用形成的独特自然综合体,对全球气候变化敏感,尤其是干旱半干旱区分布的湿地对自然环境和人类活动的响应更为显著。基于新疆哈巴河地区桦木林湿地人工开挖130 cm深的地层剖面,结合较高时间分辨率的14C测年数据和孢粉组合,揭示出该区3600年来曾经历5个时段的植被变化和人类活动的影响。3540—3430 cal a BP期间,该区以蒿属(Artemisia)等旱生植物为主,湿地尚未形成;3430—2640 cal a BP期间,局地小环境较湿润,湿生草本和以沼泽蕨(Thelypteris palustris)为代表的蕨类植物大量生长,落叶阔叶的桦木属(Betula)植物开始出现;至2640—660 cal a BP期间,浅水湿地开始形成,桦木属植物迅速扩张,但在大区域仍分布着由藜科(Chenopodiaceae)和蒿属等为主要组成的荒漠植被;尤其在660—210 cal a BP期间,桦木属成为森林的优势种;值得关注的是,近200年以来,该区以藜科为代表的草本植物增多,而桦木林出现萎缩。通过对选取的典型局域湿地不同历史时期环境变化和人类活动影响的研究,揭示了该区3600年以来的植被和环境变化,从而加深对当地历史时期植被变化过程的理解,同时也可为当地湿地生态建设和湿地生物多样性保护政策的制定提供科学依据。

Wetlands are uniquely natural complexes that result from the interaction between land and water,which are particularly sensitive to climate change and human activities,especially the different wetlands that are distributed around the arid areas in northwest China.Sediments deposited in natural wetlands provide continuous fossil records with a high time resolution for regional climatic change and the evolution process of local wetlands.Therefore,they have great advantages in revealing changes in regional ecological environment and interaction between human beings and climate and environment.Sporopollen is a reliable high-resolution environmental proxy that is widely used in the reconstruction of paleovegetation,paleoclimate,and paleoenvironment.Fossil pollen data from a 130 cm sediment profile collected in the Betula wetland of Habahe in Xinjiang of China indicated that the area has experienced five periods of change in terms of vegetation and human activity over the past 3600 years.The results indicate that desert plants such as Artemisia dominated the study area during the period 3540—3430 cal a BP and wetlands had not yet formed then.However,the local microclimate became more humid,while herbaceous plants and ferns such as Thelypteris palustris became abundant during the time Betula first appeared around 3430—2640 cal a BP.The shallow wetland began to develop and Betula expanded rapidly during the period 2640—660 cal a BP,however,desert vegetation such as Chenopodiaceae and Artemisia still thrived in the area.The area became a full wetland with Betula becoming dominant from 660—210 cal a BP.A decline in Betula and sharp increases in Chenopodiaceae pollen were evident in the pollen assemblages from the past 200 years,and were not only related to the drying of climate but also affected by the intensification of human activities,resulting in the reduction of birch plants and shrinkage of the wetland area.Moreover,high population growth during the period promoted the rapid development of animal husbandry and agriculture,thus breaking the balance between man and nature and leading to the further deterioration of the natural environment around the wetland.Therefore,by investigating the impact of environmental changes and human activity on typical local wetlands during different historical periods,this study revealed the changes of vegetation and environment in the Habahe region over the past 3600 years.This study contributes to the conservation of wetlands,biodiversity,and local ecological construction.In addition,it increases the knowledge on historical vegetation and human environmental changes that have occurred in this region.