AMF对喀斯特土壤枯落物分解和对宿主植物的养分传递

为探索丛枝菌根真菌(arbuscular mycorrhizal fungi,AMF)在喀斯特土壤中养分利用机制,采用分室系统隔室装置(用20μm或0.45μm尼龙网双层隔离)对香樟(Cinnamomum camphora)幼苗进行幼套球囊霉(Glomus etunicatum)接种处理和施氮处理,并采用15N稳定同位素技术标记了黑麦草(Lolium perenne)枯落物作为土壤有机残体,幼苗生长15周后测定了隔室幼苗生长性状指标、氮、磷摄取量、植株和隔室土壤中的δ15N值、微生物量碳、微生物量氮以及菌丝体密度,结果表明:AMF具有腐生营养能力,促进了土壤枯落物的分解并吸收其释放的15N传递给宿主植物利用;香樟幼苗优先利用根际周围氮维持生长;在低氮状态下,香樟植株通过AMF菌丝体更多地利用了相邻隔室枯落物分解释放的15N;施加根际外源氮有利于AMF对隔室枯落物的分解,但降低了植株对枯落物氮的利用;根际高氮状态下植株的氮、磷摄取量较大;高养分状态下提高了相邻隔室微生物量碳、氮含量和菌丝体密度。

Nutrients transfer for host plant and litter decompositon by AMF in Karst soil

In order to explore the nutrient utilization mechanisms of arbuscular mycorrhizal fungi(AMF) in Karst soil,Cinnamomum camphora seedlings were inoculated with Glomus etunicatum and fertilized with nitrogen in compartment equipment of microcosms separated by double 20μm-nylon mesh or 0.45μm-nylon mesh.Lolium perenne litter labelled isotope of 15N as organic residue were put into soil of compartments.Some indexes,which are traits of seedlings growth,nitrogen and phosphors uptake,δ15N value,micro-biomass carbon,micro-biomass nitrogen,hyphae length in soil,were measured after 15 weeks.The results indicated that: the arbuscular mycorrhizal symbiosis of Glomus etunicatum can have saprotrophic capability and it enhanced soil litter decomposition and taked up the 15N from the adjoining compartment to supply for the host plants;Cinnamomum camphora seedlings gived priority to the use of nutrient in the rhizosphere.Under low nitrogen status,the Cinnamomum camphora utilized more 15N which was released from the decomposed litter in the adjoining coompartment.Additional nitrogen of rhizosphere increased litter decomposition by AMF in the compartment,but reduced the utilization of organic nitrogen from litter by the seedlings.The plants were able to increase the uptake of nitrogen and phosphors in the rhizosphere under high nitrogen condition.The content of mic-biomass carbon and nitrogen and the hyphae length were enhanced under the high nutrient conditions.