天宝岩长苞铁杉倒木微生物生物量和可溶性有机碳氮的变化

摘要

Downed logs are important carbon and nutrient pools in forest ecosystems. Monitoring of dynamics of microbial biomass and dissolved organic carbon/nitrogen are of great significance to in-depth understanding of the mechanism of downed log decomposition. Microbial biomass carbon ( MBC) , microbial biomass nitrogen ( MBN) , dissolved organic car-bon (DOC), dissolved organic nitrogen (DON), and ratio of carbon to nitrogen in bark, sapwood and heartwood of downed T. longibracteata logs various in decaying degree from Grade I to Grade V in the Tianbaoyan National Nature Re-serve, Fujian Province of China was analyzed. Results show:(1) The downed logs varied from 7. 41% to 63. 27% in wa-ter content, and were 311. 66-564. 87, 2. 34-5. 82 and 0. 09-0. 35 g·kg-1, respectively, in organic carbon, TN and TP; ( 2) In terms of MBC and MBN, the three components of the highly decayed downed logs ( GradesⅣandⅤin deca-ying degree) displayed an decreasing order of heartwood > sapwood > bark; ( 3) Sapwood and heartwood was higher in DOC than bark of the logs the same in decaying degree, while sapwood was higher in DON than bark and heartwood, ex-cept for logs of Grade Ⅱ in decaying degree;( 4) Microbial biomass C/N ratio in heartwood varied sharply between logs different in decaying degree, whereas DOC/DON ratio in sapwood did;(5) Position in the log, decaying degree and their interactions all had remarkable impacts on MBC, MBN, DOC, DON, MBC/MBN and DOC/DON ( P<0. 01 ); and (6) MBC, DOC and DON were extremely and positively related to water content in the log (P<0. 01), whereas NBC/MBN and DOC/DON negatively to TP in the log ( P<0. 05) . To sum up, during the downed log decaying or decomposing process, water content is the major factor affecting MBC, MBN, DOC and DON in decaying downed logs.%倒木是森林生态系统重要的碳库和养分库,测定倒木分解过程中微生物生物量和可溶性有机碳氮含量对于深入了解倒木分解机理具有重要意义.以天宝岩国家级自然保护区5个腐烂等级长苞铁杉(Tsuga longibracteata)倒木为研究对象,分析其树皮、边材和心材微生物生物量碳氮、可溶性有机碳氮含量以及碳氮比,结果表明:(1)长苞铁杉倒木含水率w为7.41%~63.27%,有机碳、全氮和全磷含量分别为311.66~564.87、2.34~5.82和0.09~0.35 g·kg-1;(2)高腐烂等级倒木(Ⅳ级和Ⅴ级)微生物生物量碳(MBC)和氮(MBN)含量均表现为心材>边材>树皮;(3)5个腐烂等级倒木边材和心材可溶性有机碳(DOC)含量均高于树皮,除第Ⅱ腐烂等级外,其他腐烂等级倒木心材可溶性有机氮(DON)含量均高于树皮和边材;(4)不同腐烂等级倒木心材微生物生物量碳氮比(MBC/MBN)变化较大,而不同腐烂等级倒木可溶性有机碳氮比(DOC/DON)则表现为边材变化较大;(5)倒木部位、腐烂等级及交互作用对其MBC、MBN、DOC、DON、MBC/MBN和DOC/DON均有极显著影响(P<0.01);(6)倒木MBC含量与含水率呈极显著正相关(P<0.01),DOC和DON含量也与含水率呈极显著正相关(P<0.01),MBC/MBN和DOC/DON与全磷含量呈显著负相关(P<0.05).研究表明,倒木分解过程中微生物生物量碳氮和可溶性有机碳氮含量变化受其含水率影响较大.