喀斯特森林常见树种倒木分解对土壤腐殖质的影响

Effects of Downed Logs Decomposition of Common Tree Species on Soil Humus in Karst Forest

摘要:

为探究喀斯特森林常见树种倒木分解过程中，树种、腐烂等级及距离对土壤腐殖质含量的影响机制，了解倒木在森林生态系统中的功能作用，以茂兰喀斯特常绿落叶阔叶混交林中处于轻度、中度和重度腐烂的青冈栎(Cyclobalanopsis glauca)、圆果化香(Platycarya longipes)、枫香(Liquidambar formosana)和狭叶润楠(Machilus rehderi)倒木为研究对象，对距离倒木10、30和50 cm处的表层土壤中的腐殖质总碳、胡敏酸、富里酸和胡敏素含量进行测定。结果表明，喀斯特森林常见树种倒木的树种、腐烂等级及树种和腐烂等级的交互作用显著影响土壤腐殖质各组分含量(总碳、胡敏酸、富里酸和胡敏素)，距离则显著影响土壤腐殖质的有机碳和胡敏素。狭叶润楠倒木邻近土壤腐殖质总碳、胡敏酸、富里酸和胡敏素含量显著低于枫香、青冈栎和圆果化香。重度腐烂的枫香和圆果化香倒木邻近土壤腐殖质总碳、胡敏素含量均显著高于轻度腐烂。随着距倒木距离的增加，狭叶润楠和枫香的总碳含量和胡敏素含量呈显著下降趋势。倒木邻近土壤的有机碳、全氮、全磷、水解氮和有效磷含量与各腐殖质组分之间的相关性随着腐烂等级增加显著增强。喀斯特森林中倒木分解对土壤碳和养分循环具有重要影响，不同树种间土壤腐殖质积累模式有差异，且腐烂等级可调节倒木分解与养分循环之间的关系。

Abstract:

To explore the influence mechanisms of tree species, decay grades and distance on the content of soil humus during the decomposition process of common tree species in karst forests, and to understand the functional role of fallen trees in forest ecosystems, the contents of total carbon, humic acid, fulvic acid and humin in the surface soil at 10, 30 and 50 cm away from the fallen trees of Cyclobalanopsis glauca, Platycarya longipes, Liquidambar formosana and Machilus rehderi in the evergreen and deciduous broad-leaved mixed forest of Maolan karst were measured. The results showed that the tree species, decay grades and the interaction between tree species and decay grades of fallen trees in karst forests significantly affected the contents of various components of soil humus (total carbon, humic acid, fulvic acid and humin), while distance significantly affected the organic carbon and humin of soil humus. The contents of total carbon, humic acid, fulvic acid and humin in the soil adjacent to the fallen trees of M. rehderi were significantly lower than those of L. formosana, C. glauca and P. longipes. The contents of total carbon and humin in the soil adjacent to the heavily decayed fallen trees of L. formosana and P. longipes were significantly higher than those of the slightly decayed ones. With the increase of distance from the fallen trees, the contents of total carbon and humin of M. rehderi and L. formosana showed a significant downward trend. The correlations between the contents of organic carbon, total nitrogen, total phosphorus, hydrolyzable nitrogen and available phosphorus in the soil adjacent to the fallen trees and the contents of various components of soil humus significantly increased with the increase of decay grades. Therefore, the decomposition of fallen trees in karst forests had an important impact on soil carbon and nutrient cycling. There were differences in the accumulation patterns of soil humus among different tree species, and decay grades could regulate the relationship between fallen tree decomposition and nutrient cycling.