Anthropogenic effect on deposition dynamics of lake sediments based on 137Cs and 210Pbex techniques in Jiuzhaigou National Nature Reserve, China

Abstract

Radionuclide dating techniques characterized by 137 Cs and 210 Pb ex have recently been applied in the study of lake sediments around the world. In this study, a chronological series of sediment cores was established based on 137 Cs and 210 Pb ex analyses along with the evaluation of sediment properties, such as particle size distribution, total organic carbon (TOC), carbonate content, and acid-insoluble residue, to study sediment accumulation rates, sediment sources, and responses to human activities in the Jiuzhaigou National Nature Reserve in southwestern China. In terms of the particle size distribution of sediments, silt content was the highest, and clay and sand contents were relatively low. The sediments displayed high TOC contents because of the significant amounts of vegetation grown in the lakes. The carbonate content was also high due to the overall geological background of carbonates in Jiuzhaigou. Carbonate content tended to decline from top to bottom in the sediment cores, whereas the acid-insoluble residue tended to increase. These results suggested that the depth variation of the environmental parameters of the sediments in two lakes in Jiuzhaigou would correspond to each other. The results indicated that the sediment rate of Jiuzhaigou was generally high with strong siltation, indicating that serious soil loss was induced by intensive human activities in the basin over the past decades. The increases in the mass accumulation rate, contents of acid-insoluble residue, and mean particle size during the periods of 1840-1900s, late 1930s-early 1950s, 1966-1978, and 2003-2006 revealed the occurrence of severe soil and water loss as a result of extensive agricultural expansion, large-scale deforestation, and road construction in Jiuzhaigou. The deposition rate and the properties of lacustrine sediments could reflect the significant impact of human activities on lake sedimentation during Jiuzhaigou′s history.

Are climate warming and enhanced atmospheric deposition of sulfur and nitrogen threatening tufa landscapes in Jiuzhaigou National Nature Reserve, Sichuan, China?

“…less organic debris for tufa barrage development, and (7) flood plains become more erodible, reducing tufa accumulation. Lake core evidence and runoff monitoring have already proved that deforestation increased soil erosion, lake sedimentation, and nutrient inputs to runoff in Jiuzhaigou Liang et al, 2014). All the above suggest that deforestation and its associated land use change might be another important cause of tufa degradation in Jiuzhaigou and a relevant systematic analysis is needed in future.…”

“…cascades/shoals, 110 lakes/pools, and numerous springs. Due to logging in 1966-1978 and poor management of tourism development in the 1980s and early 1990s, human activities caused remarkable adverse effects on tufa landscapes then, such as increased lake sedimentation, water pollution, and physical damage to tufa (Zhou, 1998;Gu et al, 2013;Liang et al, 2014). In order to protect the tufa landscapes, logging was banned in 1978 and a number of regulations/infrastructure were implemented/built in the late 1990s…”

Carbon accumulation and sequestration of lakes in China during the Holocene

“…Great efforts have been made to estimate the C accumulation and sequestration capacity of lakes and to identify the controlling factors (Alin & Johnson, 2007; Kastowski et al ., ; Ferland et al ., ; Heathcote & Downing, ; Anderson et al ., ; Kortelainen et al ., Kortelainen et al ., ). Several factors have been suggested to significantly affect lake C cycle including climate (Gudasz et al ., ; Anderson et al ., ), nitrogen input (Heathcote & Downing, ; Kortelainen et al ., Kortelainen et al ., ; Anderson et al ., ), and land‐use change (Anderson et al ., ; He & Ruan, ; Liang et al ., ). However, most of such studies are confined to lakes in boreal and subarctic regions (Anderson et al ., , ; Ferland et al ., ; Kortelainen et al ., Kortelainen et al ., ), while lakes in other climate regions have received little attention.…”

Conserving the unique aquatic ecosystem of the Jiuzhai National Heritage Site after the 2017 earthquake: Achievements and challenges

“…After the earthquake, the Chinese government launched post-disaster reconstruction with an investment of 3.655 billion Chinese yuan, and these efforts mainly included engineering countermeasures, such as projects covering housing and public infrastructure rebuilding, secondary geohazard control, and ecological restoration. While these projects are necessary to reconstruct the Jiuzhai NNR and can effectively reduce the negative effects of collapses, landslides, debris flows, and other earthquake-induced secondary geohazards, relatively high-intensity reconstruction projects and improper activities may cause soil loss, which eventually occurs in water bodies and lakes (Liang et al, 2014), leading to swamping, as well as nonpoint source pollution, which can eventually be harmful to aquatic systems.…”