森林凋落物淋溶中的溶解有机物与紫外-可见光谱特征

Ultraviolet-visible Spectroscopic Characteristics of Dissolved Organic Matter Released from Forest Litterfall

摘要:

对格氏栲(Castanopsiskawakamii)和杉木(Cunninghamialanceolata)人工林新近凋落物、半分解层(F层)和分解层(H层)凋落物进行室内模拟淋洗实验,研究了凋落物淋溶过程中溶解有机碳(DOC)浓度变化及紫外-可见(UV-Vis.)光谱特征。结果表明,格氏栲和杉木人工林新近凋落物淋出液的DOC浓度较低,F层淋出液的DOC浓度较高;格氏栲凋落物淋出液的DOC浓度基本上随淋溶次数的增加而降低,杉木的则先升后降。淋出液中溶解有机物(DOM)的紫外吸收值均随波长的增加而减小,且UV-Vis.吸收曲线均在200 nm附近出现吸收峰,不同来源DOM的E₂₄₀/E₄₂₀存在显著差异;同一样品各次淋出液的DOC浓度与E₂₀₀有很好的线性关系(R²>0.90),据此,可用E₂₀₀值估算DOC浓度。

Abstract:

Laboratory leaching experiment and UV-visible spectra determination were carried out for leachates from fresh litter fall and litters in F (fragmented) and H (Humus) layers in 35-year-old plantations of Castanopsis kawakamii and China fir (Cunninghamia lanceolata) in Fujian Province. The results showed that the concentration of dissolved organic carbon (DOC) in leachate from fresh litter fall was lower and that from F layer was higher for both plantations. In Castanopsis plantation, DOC concentration declined with the increasing number of leaching times, whereas that in China fir plantation increased at first then decreased. UV-visible spectra absorption values of leachates from litter fall and different litter layers decreased with the increase of wavelength, and a peak at about 200 nm was observed in all cases. E₂₄₀/E₄₂₀ ratio of dissolved organic matter from different sources was quite different. The concentration of DOC in leachates from the same sample was linearly correlated with E₂₀₀ (R²>0.90), suggesting that DOC concentration could be estimated at E₂₀₀.