| 摘要: |
| 气候变暖背景下，越来越多证据表明远离人类活动的偏远高山地区湖泊生态系统已经发生明显变化。然而，气候、非气候因子以及流域过程的影响错综复杂，使得高山地区湖泊生态系统响应全球变化的研究未取得统一认识。本研究选择云南省维西高山湖聚龙湖作为研究对象，利用沉积记录中的粒度、磁化率、元素以及硅藻等，结合气候记录和遥感资料，分析了近180年来聚龙湖沉的湖泊流域生态环境变化历史。结果表明，1970-1996年间区域气温升高，聚龙湖流域覆盖的冰川大面积消融，地化指标(TOC、TN、中值粒径、沉积速率)表明湖泊水动力增强、营养负荷降低；2000年以后区域降水减少、温度持续增加，流域永久性冰川消失，裸地面积增加，元素和磁化率指标表明土壤风化侵蚀增强。研究时段内，聚龙湖硅藻群落主要以Fragilaria占优势。在水动力增强的期间，河流相的Nitzschia spp.和附生Achnanthes minutissima相对丰度增加，硅藻主要组成(以PCA第一轴得分表示)在1960s存在突变点，之后保持相对稳定，与流域气候-水文-侵蚀等指标的持续变化不同；然而，硅藻群落次要组分在1960s之后持续变化，说明流域气候-水文-侵蚀等过程已经开始影响硅藻群落稀有物种群落，整个硅藻群落可能在未来全球变化下受到更大影响。本研究突出了气候变化下湖泊流域的水文、侵蚀、冰川消融多个过程对高山湖泊水生生物群落的综合影响，进一步明确了高山湖泊生物群落对全球变化的非线性响应特征。未来的气候变化背景下，西南横断山区水生硅藻群落稀有物种将持续变化，可能最终导致整个硅藻生物群落的突变。鉴于硅藻是该区域水生生态系统最重要的初级生产者，其重大变化将显著影响其它生物类群的多样性和稳定性，应该开展多尺度(时间、空间、跨营养级)的研究，以进一步科学评估全球变化对生物圈的影响。 |
| 关键词: 硅藻 西南横断山区 气候变化 突变 冰川消融 |
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| 基金项目:国家重点基础研究发展计划（973计划） |
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| Multi-process changes in the watershed of the sedimentary record of Lake Julong,Hengduan Mounrtains over the past two centuries |
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Yang Yufeng,Zhao Yanjie,Zheng Jianan,Qiu Hengshuai,Zhu Kexin,Zhao Yu,Wang Rong,Wenxiu Zheng
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1.Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences;2.School of Geography and Ocean Science, Nanjing University
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| Abstract: |
| In the context of a warming climate, there is increasing evidence that lake ecosystems in remote alpine areas far from human activities have undergone significant changes. However, the complex interplay of climatic, non-climatic factors, and watershed processes complicates the understanding of lake ecosystem responses to global changes in alpine areas. In this study, we chose Julong Lake, an alpine lake in Weixi, Yunnan Province, as the research site, and analyzed the history of lake basin ecosystem changes over the past 180 years using grain size, magnetization, elements, and diatoms in the sedimentary record, in conjunction with climatic records and remote sensing data. The results showed that the regional temperature increased during 1970-1996, the glaciers covering the Julong Lake watershed ablated in a large area, and the geochemical indicators (TOC, TN, median particle size, sedimentation rate) indicated the enhancement of lake hydrodynamics and a reduction in nutrient loads. After 2000, regional precipitation decreased, and temperature continued to increase, leading to the disappearance of permanent glaciers in the watershed and an increase in bare land area. Elemental and magnetization indexes indicated enhanced weathering and erosion of soils. The diatom community of Julong Lake was dominated by Fragilaria during the study period. During the period of enhanced hydrodynamics, the relative abundance of Nitzschia spp. and epiphytic Achnanthes minutissima increased. The primary composition of diatoms (expressed as PCA Axis I scores) reached a tipping point in the 1960s and then remained relatively stable, in contrast to the continuous changes in climatic, hydrological, and erosional indicators. However, the secondary composition of diatom communities continued to change after the 1960s, indicating that processes such as watershed climate, hydrology, and erosion have begun to affect rare species in the diatom community. This suggests that the entire diatom community may be increasingly affected under future global change. This study highlights the combined effects of hydrology, erosion, and glacier ablation on aquatic communities in alpine lakes under climate change, clarifying the nonlinear response characteristics of these communities to global changes. In the context of future climate change, rare species in aquatic diatom communities in the Southwest Hengduan Mountains will continue to change, potentially leading to abrupt shifts in the entire diatom biome. Given the crucial role of diatoms as primary producers in aquatic ecosystems, such changes could significantly impact the diversity and stability of other biota. Future research should involve multi-scale studies (temporal, spatial, and across trophic levels) to comprehensively assess the impacts of global change on the biosphere. These studies should include detailed monitoring of diatom communities and their responses to various climatic and non-climatic factors to predict potential ecological shifts and inform conservation strategies. |
| Key words: Diatom southwest Hengduan Mountains climate change regime shift glacier ablation |
