黄土区六种植物凋落物与不同形态氮素对土壤微生物量碳氮含量的影响

黄土高原丘陵沟壑区进行的以退耕还林还草为主的生态环境建设，使得进入土壤生态系统有机物的种类及数量发生变化，其对土壤微生物量碳、氮的影响是值得关注的问题。采用室内培养法研究了采自该区6种不同植物凋落物（碳氮比在15.1-50.7之间）及其与不同形态氮素（NH+4-N及NO-3-N）配合对土壤微生物量碳、氮及矿质态氮含量的影响。结果表明，加入不同凋落物均显著提高了土壤微生物量碳、氮含量，其中加入柠条、沙打旺等碳氮比低的凋落物在培养的一段时期内土壤微生物量碳、氮均高于碳氮比高的凋落物（刺槐、沙柳和长芒草）。在加入凋落物再施用NH+4或NO-3，也提高了土壤微生物量碳、氮含量，其中铵态氮处理土壤微生物量碳、氮含量的增加达显著水平，说明微生物更易利用铵态氮。加入C/N高的凋落物后土壤中的矿质氮发生固持，矿质态氮固持量与凋落物的C/N比呈显著的正相关关系。建议在黄土高原丘陵沟壑区植被恢复过程中，有必要考虑不同植物凋落物的碳、氮养分含量及转化特性，以协调土壤碳、氮转化过程。

Effects of plant residues and nitrogen forms on microbial biomass and mineral nitrogen of soil in the Loess Plateau

Both the quality and quantity of plant residues returned into the soil ecosystems in the gully and valley region of the Loess Plateau have been substantially changed with the returning of croplands to forests and grasslands since 1990 in Northwestern China.However,no study has reported if soil carbon(C) or nitrogen(N) has been increased after one decade of such a land use change.An important mechanism to understand these changes is to know if and how soil microbial biomass C and N(SMBC,SMBN) and mineral N h...