兴安落叶松火烧迹地林褥层可溶性有机质的时间变化特征

doi:10.13292/j.1000-4890.202012.021

摘要/Abstract

摘要： 探索林褥层可溶性有机质在火后随恢复时间的变化特征，能够更全面地认知林褥层在火顶极生态系统中的作用，有助于我们认知火干扰对陆地生态系统产生持久影响的机制。以不同过火年份兴安落叶松火烧迹地和未过火样地的林褥层（未分解凋落物层、半分解凋落物层和苔藓层）为对象，使用水浸提法提取其可溶性有机质(DOM)，测定其在未过火和火后各时期可溶性有机碳(DOC)含量、可溶性有机质的紫外可见光光谱参数和荧光光谱参数等指标，分析比较林褥层在各时期相同指标间的差异。火干扰导致未分解层DOC含量、半分解层和苔藓层的紫外可见吸光度、HIX_b、苔藓层a(355)在恢复初期和恢复中期持续下降，在恢复后期回升。未分解层a(355)、紫外-可见吸光度、SUVA₂₅₄、HIX_b、半分解层DOC含量在恢复初期下降，在恢复中期和后期持续回升。苔藓层DOC含量在恢复中期下降，在恢复后期回升。半分解层SUVA₂₅₄在恢复初期显著升高，在恢复中期回落。未分解层SUVA₂₈₀在恢复初期和中期持续升高，在恢复后期回落，半分解层和苔藓层SUVA₂₈₀、苔藓层SUVA₂₅₄在火后持续降低，降幅逐渐减缓。过火前后各层FI以及半分解层a(355)无明显变化。火烧迹地林褥层未分解层分解速率高于半分解层，其随恢复时长的变化趋势均为先降低再升高。火干扰对兴安落叶松林褥层DOM多种特征产生显著影响。随恢复时间的增加，兴安落叶松火烧迹地林褥层DOC含量、腐殖化程度、芳香化程度、不饱和共轭双键数目、半分解层和苔藓层DOM平均相对分子量均表现出先降低再升高的趋势，未分解层DOM平均相对分子量表现出先升高再降低的趋势。未分解层DOC含量、a(355)、HIX_b、FI、SUVA₂₅₄和SUVA₂₈₀随生态恢复变化趋势与半分解层不同，其中，未分解层SUVA₂₅₄和SUVA₂₈₀变化趋势与半分解层相反。本研究未发现火干扰对兴安落叶松林褥层DOM来源及自生源特征有明显影响。未分解层受恢复时长影响较大，半分解层受恢复时长影响适中，苔藓层受恢复时长影响较小。

关键词: 兴安落叶松, 火烧迹地, 可溶性有机质, 时间尺度, 紫外-可见光光谱, 荧光光谱

Abstract: This study explored the temporal variation of dissolved organic matter (DOM) in postfire forest floor as burned stands recovered over time. Such knowledge would help us understand the role of forest floor in the fire climax forest ecosystem and mechanism of the lasting impact of fire disturbance on terrestrial ecosystem. The unburned and burned forest floors of Larix gmelinii with varied post-fire time (in years) were studied with focus on Oi horizon, Oe horizon, and moss layer. DOM was extracted using the water extraction method. Dissolved organic carbon (DOC) content, UV visible spectrum parameters, and fluorescence spectrum parameters of DOM were measured, and then possible differences among forest stand restoration stages were analyzed. The DOC content, UV-Vis absorbance and HIX_b in Oe horizon and moss layer, and a(355) in moss layer exhibited a continuous decreasing pattern in the early and middle restoration stages, which began to increase in the late restoration stage. The a(355), UV-Vis absorbance, SUVA₂₅₄, and HIX_b in Oi horizon and the DOC content in Oe horizon decreased continuously in the early restoration stage but increased in the middle and late restoration stages. The DOC content in moss layer decreased in the middle restoration stage but increased in the late restoration stage. The SUVA₂₅₄ increased in the early restoration stage but decreased in the middle restoration stage. The SUVA₂₈₀ in Oi horizon increased continuously in the early and middle restoration stages but decreased in the late restoration stage. The SUVA₂₈₀ in Oi horizon and moss layer and the SUVA₂₅₄ in moss layer decreased continuously after fire, but the decline was slowing down over time. The FI in forest floor and a(355) in Oe horizon were not significantly affected by fire disturbance. The decomposition rate of the Oi horizon was higher than that of the Oe horizon in post fire forest floor. However, the decomposition rate varied over time, showing decrease first and then increase in both horizons. Fire disturbance had significant effects on DOM characteristics of Larix gmelinii forests. In the burned area, the DOC content, humification degree, aromatization degree, the number of unsaturated conjugated double bonds and mean relative molecular weight of DOM in Oe horizon and moss layer all initially decreased and then increased. By contrast, the average molecular weight of DOC in Oi horizon increased first and then decreased. Along with the restoration, the variation trends of DOC content, a(355), SUVA₂₅₄, SUVA₂₈₀, HIX_b and FI of Oi horizon were different from those of Oe horizon, while the variation trends of SUVA₂₅₄ and SUVA₂₈₀ in Oi horizon were opposite to those in Oe horizon. Fire disturbance did not affect DOM source and autotrophic characteristics of Larix gmelinii forest floor. The magnitude of the effects of restoration duration on forest floor chemical dynamics was strong for Oi horizon, moderate for Oe horizon, and weak for moss layer.

Key words: Larix gmelinii, burned area, dissolved organic matter, time-scale, UV visible spectrum, fluorescence spectrum.

王立轩, 杨光, 高佳琪, 瓮岳太, 邸雪颖, 于宏洲. 兴安落叶松火烧迹地林褥层可溶性有机质的时间变化特征[J]. 生态学杂志, 2020, 39(12): 3913-3923.

WANG Li-xuan, YANG Guang, GAO Jia-qi, WENG Yue-tai, DI Xue-ying, YU Hong-zhou. Temporal variation of dissolved organic matter in postfire forest floor of Larix gmelinii.[J]. Chinese Journal of Ecology, 2020, 39(12): 3913-3923.

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兴安落叶松火烧迹地林褥层可溶性有机质的时间变化特征

Temporal variation of dissolved organic matter in postfire forest floor of Larix gmelinii.

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