增温对川西亚高山冷杉林凋落叶分解过程中有机碳含量的短期影响

Short-term effects of warming on organic carbon content during leaf litter decomposition in subalpine fir forest of western Sichuan

关键词:  增温, 凋落物, 有机质分解, 有机碳, 亚高山森林

Key words:  warming, litter, organic matter decomposition, organic carbon, subalpine forest

摘要:

全球气候变暖对陆地生态系统地表凋落物分解过程具有深远影响,认识高寒森林凋落物分解及其有机碳组分对增温的响应,对于阐明气候变化背景下森林碳周转具有重要意义。为探究增温引起的水热条件变化对凋落物分解过程中有机碳组分的短期影响,该研究在四川西部亚高山冷杉林内开展了为期1年的凋落叶原位分解实验。通过开顶式增温棚(OTC)模拟增温,连续采样监测凋落叶质量及其有机碳组分的动态变化。结果表明:(1)与对照组相比,模拟增温显著提高了土壤温度(+0.55 ℃),而显著降低了凋落物含水量(7.46%),但对土壤含水量无显著影响。(2)模拟增温未显著改变凋落叶质量残留和主要有机碳组分(如总有机碳、热水可溶有机碳和非结构性碳)含量,而溶解性有机碳(DOC)、可溶性糖和淀粉的含量受增温和采样时期交互作用显著影响,表明凋落物质量残留和多数有机碳组分含量对短期增温不敏感。(3)偏最小二乘结构方程模型(PLS-SEM)分析显示,尽管模拟增温未改变土壤温度和含水量、凋落物质量与有机碳组分之间的关联路径,但显著强化了凋落物含水量与有机碳组分之间的负相关关系,这表明未来川西亚高山温度升高可能通过改变地表凋落物水分状态从而影响凋落物有机碳向土壤输入养分。该研究结果强调,未来研究应更加关注增温对凋落物水分动态的影响及其在碳周转中的作用,该结果为深入理解高寒生态系统碳循环过程及优化未来全球气候变化情景下森林响应预测模型提供了重要依据。

Abstract:

Global warming profoundly impacts the decomposition of surface litter in terrestrial ecosystems. Understanding the response of litter decomposition and its organic carbon components in alpine forests to warming is of great significance for comprehending forest carbon turnover under climate change. To explore the short-term impact of warming-induced hydrothermal changes on organic carbon components during litter decomposition, a one-year in-situ decomposition experiment was carried out in a subalpine fir forest in western Sichuan. The dynamic changes of leaf litter mass and its organic carbon components were monitored through continuous sampling using simulated warming in an open-top chamber(OTC). The results were as follows:(1)Compared with the control, simulated warming significantly increased soil temperature(+0.55 ℃), while significantly decreased litter water content by 7.46%, however, it had no significant effect on soil water content.(2)Simulated warming did not significantly change the mass remaining and the content of major organic carbon components(such as total organic carbon, hot water-soluble organic carbon, and non-structural carbon)of leaf litter. However, the content of dissolved organic carbon(DOC), dissolved sugar, and starch was significantly affected by the interaction between warming and the sampling period, indicating that litter mass remaining and the content of most organic carbon components are not sensitive to short-term warming.(3)The partial least squares structural equation model(PLS-SEM)analysis showed that although simulated warming did not alter the association pathways among soil temperature and water content, litter mass, and organic carbon components, it significantly strengthened the negative correlation between litter water content and organic carbon components. This suggests that future temperature increases in subalpine areas of western Sichuan may affect the input of litter organic carbon into soil as a source of nutrients by altering the moisture status of surface litter. This study emphasizes that future research should focus more on the impact of warming on litter moisture dynamics and its role in carbon turnover. These findings provide an important basis for a deeper understanding of the carbon cycle in alpine ecosystems and for optimizing forest response prediction models under future global climate change scenarios.