侵蚀退化地植被恢复过程中芒萁对土壤可溶性有机碳的影响

林下植被是生态系统的重要组分。通过对比分析红壤侵蚀区植被恢复过程中,林下有无芒萁覆盖地的土壤可溶性有机碳(DOC,Dissolved Organic Carbon)含量及其与地下根系生物量、地上植被淋溶液DOC含量的关系。结果表明:林下植被芒萁覆盖增加了地上叶片和地下根系生物量,土壤DOC含量及储量也显著增加(P0.05),芒萁覆盖对表层土壤(0—20cm)DOC的影响大于深层土壤(20—100cm)(P0.05);相关分析结果表明,林下芒萁覆盖地土壤DOC储量与细根生物量的垂直变化呈显著的正相关关系(P0.05),且随植被恢复年限的增加相关性显著增加,地下根系的垂直分布直接影响各土层DOC储量。不同植被恢复时期,林下芒萁覆盖地土壤DOC与鲜叶(马尾松+芒萁)和枯落物(马尾松+芒萁)淋溶液DOC均呈显著的正相关关系(P0.01),而林下裸露地土壤DOC仅与鲜叶(马尾松)淋溶液DOC呈显著的相关性(P0.01),林下芒萁覆盖地相对于裸露地枯落物淋溶液对土壤DOC储量的影响大于鲜叶。植被恢复过程中芒萁覆盖地土壤微生物生物量碳和微生物熵显著高于林下裸露地。因此,在植被恢复进程中,芒萁能够提供更多底物参与土壤物质与养分循环,对土壤DOC的贡献较大,为侵蚀区马尾松林恢复提供了重要的养分再吸收来源;同时芒萁覆盖增加了微生物活性,促进了微生物对土壤DOC的同化作用,提高了微生物碳源的利用率,对土壤有机碳的积累起着重要的作用。

Effects of Dicranopteris dichotoma on soil dissolved organic carbon in severely eroded red soil

Understory, an important component of the forest ecosystem, plays an important role in maintaining forest structure and soil quality. To analyze the relationship between soil dissolved organic carbon (DOC), belowground biomass, and DOC leachates of aboveground biomass, we conducted a comparative experiment of the presence or absence of understory Dicranopteris dichotoma on severely eroded red soil. The results showed that the aboveground and belowground biomass, and the content of soil DOC increased significantly with understory D. dichotoma coverage (P < 0.05); the effect of D. dichotoma on the surface soil (0-20cm) was greater than the deep soil (20-100cm) (P < 0.05). The correlation analysis showed that there was a significant positive correlation between soil DOC storage and fine root biomass (P < 0.05), indicating that the vertical distribution of underground roots directly affects the soil DOC reserves. Moreover, there was a significant positive correlation between soil DOC with fresh leaf (Pinus massoniana and D. dichotoma) and litter (P. massoniana and D. dichotoma) leachates during vegetation restoration (P < 0.01), but there was only a significant correlation with fresh leaf (P. massoniana) leachates in the bare ground (P < 0.05). The effect of the litter leachates on the soil DOC storage was higher than the fresh leaves. The soil microbial biomass carbon and microbial entropy in D. dichotoma-covered land were significantly higher than bare land in the process of vegetation restoration. Therefore, D. dichotoma may provide more substrates to participate in soil material and nutrient cycling, contributing greatly to soil DOC, which further provides important nutrient reabsorption sources for restoration of P. massoniana forest in eroded areas. It is possible that D. dichotoma coverage increases microbial activity and promotes assimilation of soil microorganisms; thereby playing an important role in the accumulation of soil organic carbon by improving utilization of microbial carbon sources.