不同混交类型对毛竹林土壤有机碳和土壤呼吸的影响

为了解不同混交类型对毛竹林土壤有机碳含量和组成以及土壤呼吸的影响,为武夷山地区毛竹林土壤环境改善和可持续生产经营积累实验数据,以武夷山地区毛竹(Phyllostachys edulis J.Houz.)纯林、毛竹-阔叶树混交林、毛竹-油茶(Camellia oleifera Abel.)混交林、毛竹-杉木Cunninghamia lanceolate (Lamb.) Hook.]混交林和毛竹-油桐Vernicia fordii (Hemsl.) Airy Shaw]混交林5种林地为研究对象,对林地土壤进行采样并测定土壤有机碳含量、土壤活性有机碳组成和比例以及土壤呼吸.结果显示:(1)5种林地的土壤总有机碳(soil organic carbon,SOC)含量和SOC富集系数均表现为毛竹-阔叶树>毛竹-油茶>毛竹-杉木>毛竹纯林>毛竹-油桐,且一年之中夏季SOC含量最低.(2)SOC、土壤可溶性有机碳(dissolved organic carbon,DOC)、土壤微生物生物量碳(microbial biomass carbon,MBC)和轻组碳(lightfractionorganiccarbon,LFOC)含量均随土层深度加深而降低;毛竹-油桐林、毛竹-杉木林和毛竹-阔叶树林的几种土壤有机碳之间均表现为显著(P <0.05)正相关,部分甚至达到极显著(P <0.01).(3)毛竹-阔叶树林地的DOC、MBC和LFOC含量显著(P <0.05)高于其他林地,毛竹-油桐林地的DOC和LFOC含量在几种混交类型中最低,但其在0-20 cm土层的MBC含量显著(P <0.05)高于其他林地;DOC占SOC的比例随土层深度加深而增大,LFOC比例随土壤深度加深而减小,但混交林的LFOC比例相对于毛竹纯林有所提高,MBC比例在一定范围内波动.(4)一年四季中夏季林地的土壤呼吸最高,而毛竹-油茶林的土壤呼吸在几种林地中较高.综上,不同混交类型对土壤有机碳含量和组成以及土壤呼吸产生影响,毛竹-油桐林的土壤有机碳相对毛竹纯林有所下降,但其能够提高土壤上层的MBC含量,毛竹-阔叶树和毛竹-油茶的混交类型对土壤有机碳含量的提升效果较好,但毛竹-油茶林的土壤呼吸较高,因此在选择毛竹林混交方式时需要综合考虑.(图5表2参53)

Effects of different mixed forest types on soil organic carbon and soil respiration in Phyllostachys edulis J. Houz forest

This study was conducted to understand the effects of different mixed forest types on soil organic carbon content, composition, and soil respiration in a Phyllostachys edulis forest, and to accumulate experimental data for the improvement of the soil environment, and sustainable production and management of P. edulis forests in the Wuyi Mountains. Five types of forests in the Wuyi Mountains: P. edulis forest, mixed forest of P. edulis and broad-leaved trees, mixed forest of P. edulis and Camellia oleifera, mixed forest of P. edulis and Cunninghamia lanceolata, and mixed forest of P. edulis and Vernicia fordii were used as research sites. Soil samples were taken from these forest lands, followed by determination of the soil organic carbon(SOC) content, composition, proportion of soil active organic carbon, and soil respiration. The results showed that:(1) The SOC content and SOC enrichment modulus of the five forests were as follows: mixed forest of P. edulis and broad-leaved trees > mixed forest of P. edulis and C. oleifera > mixed forest of P. edulis and C. lanceolata > P. edulis forest > mixed forest of P. edulis and V. fordii, and the SOC content was the lowest in summer.(2) The contents of SOC, dissolved organic carbon(DOC), microbial biomass carbon(MBC), and light fraction organic carbon(LFOC) decreased with the depth of the soil layer. There were significant(P < 0.05) positive correlations among these types of soil organic carbon in mixed forests of P. edulis and V. fordii, P. edulis and C. lanceolata, and P. edulis and broad-leaved trees, and some even reached extremely significant correlations(P < 0.01).(3) DOC, MBC, and LFOC contents in mixed forests of P. edulis and broad-leaved trees were significantly(P < 0.05) higher than those in other forest lands. DOC and LFOC contents in mixed forests of P. edulis and V. fordii were the lowest in these mixed types, but MBC contents in the 0-20 cm soil layer were significantly(P < 0.05) higher than those in the other forest lands. The proportion of DOC increased and the proportion of LFOC decreased with soil depth. However, the proportion of LFOC in the mixed forest was higher than that in the pure bamboo forest, and the proportion of MBC fluctuated within a certain range.(4) Soil respiration in these forests was the highest in summer, while that in the mixed forest of P. edulis and C. oleifera was the highest of all of the forests. In summary, different mixed types resulted in differences in SOC content, composition, and soil respiration. Soil organic carbon in mixed forests of P. edulis and V. fordii was lower than that in the pure P. edulis forest, but it could increase the MBC content in the upper layer of the soil. The mixed type of P. edulis-broad-leaved-tree and P. edulis-C. oleifera had a better effect on increasing SOC content, but the soil respiration of mixed forests of P. edulis and C. oleifera was higher, so we should consider these factors comprehensively while choosing a mixed mode of P. edulis forest.