Effects of different snow treatments on soil humus content in subalpine forest soils in western Sichuan, China

doi:10.17521/cjpe.2024.0128

Abstract

Abstract:

Aims The reduction of snow cover may affect the organic matter turnover process in alpine forests by altering the surface hydrothermal environment and microbial activity, thereby affecting the synthesis and decomposition of soil humus.

Methods Focusing on the Abies fargesiivar. faxoniana fir forest in the subalpine region of western Sichuan, three snow cover treatments were set up in field: control (natural snow cover), snow cover reduction (50% snow cover removal), and snow cover removal (100% snow cover removal). The study investigated the effect of snow cover reduction/removal on soil extractable humic substance, humic acid, fulvic acid contents, and spectroscopic characteristics of humic substances. The study further explored the dynamic correlations between different snow cover treatments and soil humus based on dynamic monitoring of environmental factors and soil physicochemical properties.

Important findings The results showed that: (1) The snow cover reduction/removal treatment significantly reduced contents of soil extractable humic substance, humic acid, and fulvic acid. (2) Soil humification was low in all three snow cover treatments, with soil humic/fulvic acid values less than 1 and humic/extractable humic substance values less than 0.5. (3) Correlation analysis showed that total nitrogen content was negatively correlated with contents of soil extractable humic substance, humic acid, and fulvic acid. In summary, the snow cover reduction/removal treatments reduced soil humus content and affected the degree of soil humification. These results could facilitate an in-depth understanding of the formation of soil humus and the mechanisms of soil fertility maintenance in subalpine forests.

Key words: humus, humic acid, fulvic acid, snow cover, subalpine forest

HUANG Wen-Lan, LIU Yao, JIAN Yi, ZHANG Lin-Hui, CHEN Su, HUANG Lu-Lu, YU Li-Yun, LI Han, WANG Li-Xia, TAN Bo, ZHANG Li. Effects of different snow treatments on soil humus content in subalpine forest soils in western Sichuan, China[J]. Chin J Plant Ecol, 2024, 48(11): 1445-1458.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2024.0128

https://www.plant-ecology.com/EN/Y2024/V48/I11/1445

Figures/Tables 5

Fig. 1 Effects of different snow treatments on soil moisture content (A), pH (B), soil organic carbon (C), total nitrogen (D), and soil total phosphorus (E) contents in subalpine forests in western Sichuan (mean ± SD, n = 5). * indicate significant differences in main effects at different times in the same soil layer (p < 0.05). Different uppercase letters indicate significant differences in main effects between treatments at the same soil layer (p < 0.05).

Table 1 Efects of soil layer and snow treatment on soil physicochemical properties, humic substances, and optical properties at different sampling times

Fig. 2 Effects of different snow treatments on soil extractable humus content (A), humic acid content (B), fulvic acid content (C), humic acid/fulvic acid (D), humic acid/extractable humus (E), hue coefficient (F), optical density value (G), and A600/C (H) in subalpine forest soils in western Sichuan (mean ± SD, n = 5). * indicating significant differences in main effects at different times in the same soil layer (p < 0.05). Different uppercase letters indicate significant differences in main effects between treatments at the same soil layer (p < 0.05). Different lowercase letters indicate significant differences in simple effects between treatments at the same time and soil layer (p < 0.05).

Fig. 3 Kumuda type of humic substances in different soil layers in subalpine forest in western Sichuan. Stability of humic substances: A > B > P > Rp. Values are averaged across sampling dates.

Fig. 4 Soil humus was correlated with physical and chemical properties during the snow melting period (A, B) and early snow formation period (C, D) in subalpine forests in western Sichuan. The size of the circular dot is used to show the strength of the correlation, color is used to represent the positive and negative correlation coefficients, and the color block of the square is used to represent the p-value of the correlation test. E4/E6, optical density value; FA, fulvic acid content; FTC, freeze-thaw cycle; HA, humic acid content; HA/FA, humic acid /fulvic acid; HS, extractable humic substance content; PQ, humic acid/extractable humic substance; SOC, soil organic carbon content; SWC, soil water content; Tm, temperature; TN, total nitrogen content; TP, total phosphorus content; Δlog K, hue coefficient.

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