不同植被类型下土壤胡敏酸降解特性

为了解不同植被类型下土壤HA(胡敏酸)降解菌的种类、分布状况及其中C的降解程度,选取退耕还林典型地带,于农田、油松、刺槐、沙棘、混交林0~10cm土样中分别提取HA,利用HA作为唯一C、N源筛选HA降解微生物. 结果表明:相比农田土壤HA,各林地土壤HA中w(C)增加,w(N)有所减少；共分离获得5株HA降解菌,根据16s rRNA序列鉴定,分别为Bacillus licheniformis、Rhizobium nepotum、Microbacterium resistens、Stenotrophomonas maltophilia、Streptomyces azureus,相似度分别为99.65%、99.78%、98.71%、99.23%、99.78%. 农田、刺槐、油松及混交林的降解菌优势种为Bacillus licheniformis,沙棘优势种为Streptomyces azureus,刺槐无Rhizobium nepotum分布,沙棘和混交林无Stenotrophomonas maltophilia分布；降解菌数量为沙棘>刺槐>农田>油松>混交林,混交林仅为沙棘的58.87%；混交林、油松、沙棘、刺槐降解菌的RC(呼吸量碳)分别较农田高出25.35%、11.28%、10.36%、7.11%,混交林与农田差异显著(P<0.05). 沙棘、刺槐、农田、油松降解菌MBC(微生物生物量碳)分别较混交林高出131.91%、68.48%、64.98%、54.47%,刺槐、农田、油松三者与沙棘及混交林差异显著(P<0.05). 沙棘土壤HA的TDR(总降解率)明显高于农田和混交林(P<0.05). 相关性分析表明,降解菌数量与MBC呈极显著正相关,与RC呈极显著负相关(P<0.01). 结果表明,植被类型影响了土壤HA降解菌的群落组成及其降解特性. 

Decomposition Characteristics of Soil Humic Acid Under Different Vegetation Types

Humic acid (HA) from the 0-10cm depth from an arable soil, as well as four forest soils (Chinese pine, black locust, Sea-buckthorn and mixed forest) was extracted from a typical area in land conversion projects. The soils were the sole energy constituents in the HA medium. Several species of microorganisms, from soil of these vegetation types and capable of utilizing HA as a carbon and nitrogen sources, were trained and isolated in the medium. Results showed that the HA extracted from the four forest soils had a higher carbon content, and lower nitrogen content, than those of the arable land. Four bacteria strains and one strain actinomycetes were isolated by the HA substrate. The species were Bacillus licheniformis (99.65%), Rhizobium nepotum (99.78%), Microbacterium resistens (98.71%), Stenotrophomonas maltophilia (99.23%) and Streptomyces azureus (99.78%) based on the 16s rRNA sequence analysis. B. licheniformis was the dominant species in HA substrate of arable land, Chinese pine, black locust and mixed forest, and S. azureus was the dominant species in Sea-buckthorn HA medium. R. nepotum was not found in the black locust HA substrate, and S. maltophilia was not found in Sea-buckthorn or mixed forest soils. The colony forming unit (CFU) of decomposing bacteria in HA medium was in the decreasing order Sea-buckthorn>black locus>arable land>Chinese pine>mixed forest. CFU in mixed forest was only 58.87% that of Sea-buckthorn. Soil HA total degradation rate (TDA) was comprised of two parts:respiration carbon (RC) and microbial biomass carbon (MBC). The Microbial RC of mixed forest, Chinese pine, Sea-buckthorn and black locust was higher by 25.35%, 11.28%, 10.36% and 7.11% respectively than that of arable land. The difference between the mixed forest and arable land was significant (P<0.05). MBC of decomposing bacteria in Sea-buckthorn, black locust, arable land, and Chinese pine was higher by 131.91%, 68.48%, 64.98% and 54.47% respectively over that of the mixed forest. The MBC of black locust, arable land and Chinese pine showed no significant differences. However, the difference among the Sea-buckthorn and Mixed forest was significant (P<0.05). TDR of Sea-buckthorn soil HA was significantly higher than that in arable land and mixed forest (P<0.05). Correlation analysis showed that CFU was correlated positively with MBC and negatively correlated with RC negatively (P<0.01). This indicated the change of vegetation type had some influence on the community of HA decomposition bacteria and their decomposition characteristics.