长期人类活动对浙江全新世植被的影响

Long-term impacts of anthropogenic disturbances on Holocene vegetation in Zhejiang,China

全新世人类活动逐渐增强,其对自然植被的干扰和改造也逐渐加深,在部分地区已然成为引起植被变化不可忽视的因素之一。考古结果证实,浙江地区在过去10 ka存在连续的文化序列,但全新世人类活动对区域植被的影响程度和范围尚不明确。本文收集、整理了浙江地区共40个样点的全新世孢粉记录,按照有无史前文化的发生将其分为遗址、遗址周边和自然3类数据,利用RRatepol程序包计算了各个样点的植被变化速率(RoC),同时使用孢粉生物群区化方法(Biomisation)重建了古植被变化过程。结果显示,在文化遗址,全新世RoC变化幅度较大且波动频繁,9.0—3.0 cal ka BP期间整体呈增加趋势;遗址周边的RoC变化幅度介于遗址和自然点位之间,在3.0 cal ka BP之后呈现迅速增加;自然点的RoC变幅最小且较为稳定,在2.0 cal ka BP后才出现明显升高。全新世期间人类活动引起的局部植被变化速率可能是自然植被变化的2~3倍,并且在3.0 cal ka BP后,人类活动对浙江古植被影响的空间范围开始明显扩张。人类活动导致的植被变化与自然植被变化存在一定的背离,新石器时代毁林开荒和种植农业的发展导致了浙江地区植被景观的破碎化。遗址点的生物群区停留时间明显低于遗址周边及自然点,说明全新世人类活动加速了区域植被成分变化的同时,也导致植被生态系统的弹性和恢复力显著降低。在浙江地区以孢粉进行的气候重建以及自然保护地体系建设实践中面临的植被保护和恢复问题,必须考虑长期的人类干扰历史以及植被变化历史格局的潜在影响。

During the Holocene,human activities gradually intensified,resulting in significant interference and alteration of natural vegetation.Anthropogenic disturbance has been one of the most critical factors driving vegetation changes in some regions.The archaeological study illustrated that continuous Neolithic culture developed in Zhejiang during Holocene.However,the relationship between vegetation changes and human activities in this region remains unclear.Here,we collected 40 pollen records in Zhejiang and classified them into three groups,i.e.,archaeological sites,peripheral sites and natural sites.After standardizing the chronology and taxonomy of those pollen data,we calculated the rate and pattern of vegetation changes(RoCs)by the R-Ratepol package and Biomisation.The results showed that the RoCs increased significantly at archaeological sites,with high variabilities during 9000-3000 cal a BP.The values of RoCs at peripheral sites were lower than that of archaeological sites but showed a dramatic increase after 3000 cal a BP.The RoCs at natural sites were the lowest and relatively stable before 2000 cal a BP;after 2000 cal a BP,it accelerated and outstripped that of archaeological and peripheral sites.The increased RoCs at both the peripheral and natural sites manifested that the spatial range of human impact on vegetation expanded significantly in the late Holocene.The vegetation change rates exerted by Neolithic human activities might be 2-3 times greater than that under the natural state.Furthermore,there was a certain deviation between the human-related and natural vegetation changes.The deforestation and cultivation of Neolithic ancestors led to the fragmentation of the terrestrial landscape.The residence time of biomes at archaeological sites was significantly lower than that in natural and peripheral sites.To sum up,long-term human activities in Zhejiang accelerated the regional vegetation changes and reduced the stability of terrestrial ecosystems.In pollen-based vegetation and climate reconstructions,and also in the practice of vegetation protection and restoration,the potential influence of long-term human activities must be considered.