Fungal control of nitrous oxide production in semiarid grassland
Fungal control of nitrous oxide production in semiarid grassland
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DOI：
10.1007/s10533-007-9165-4
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发表时间：
2008-01-01
期刊：
影响因子：
4
通讯作者：
Stavely, L. K.
中科院分区：
文献类型：
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作者：
Crenshaw, C. L.;Lauber, C.;Stavely, L. K.
真菌既具有硝化作用，又具有反硝化作用，并在许多土壤中主导微生物生物量。最近的研究表明，真菌而不是细菌途径主导着荒漠土壤中氮素的转化。我们通过比较细菌和真菌在美国新墨西哥州中部半干旱草原的对照和氮肥施肥点对N2O产生的贡献来评估这一假设。土壤样本取自兰格拉玛(B.gracilus)的根际和生长在丛生草之间空旷区域的微生物结皮。土壤以30%或70%的持水能力培养，暴露于三种杀菌剂处理(对照、环己亚胺或链霉素)中的一种。48h后，量化N2O和CO2的产生以及几种胞外酶的活性。施N的土壤N2O产生量高于对照土壤(165vs.41pmolh(-1)g(-1))，结皮土壤高于根际土壤(108vs.97pmolh(-1)g(-1))，且随土壤水分的增加而增加(146vs.60pmolh(-1g-1))。平均而言，杀菌剂(环己亚胺)的添加使N2O的产生量减少85%，而CO2的产生量增加69%；杀菌剂(链霉素)的添加使N2O的产生量减少53%，对CO2的产生量有混合影响。通过糖苷酶和蛋白水解酶的测定以及可提取的硝酸盐和铵的测定，N2O的产生与C和N的矿化潜力显著相关。结果表明，真菌硝化反硝化作用和细菌自养硝化作用主导着该生态系统中N的转化，N2O的产生对土壤覆盖、N沉积和水分高度敏感。
Fungi are capable of both nitrification and denitrification and dominate the microbial biomass in many soils. Recent work suggests that fungal rather than bacterial pathways dominate N transformation in desert soils. We evaluated this hypothesis by comparing the contributions of bacteria and fungi to N2O production at control and N fertilized sites within a semiarid grassland in central New Mexico (USA). Soil samples were taken from the rhizosphere of blue grama (B. gracilus) and the microbiotic crusts that grow in open areas between the bunch grasses. Soils incubated at 30% or 70% water holding capacity, were exposed to one of three biocide treatments (control, cycloheximide or streptomycin). After 48 h, N2O and CO2 production were quantified along with the activities of several extracellular enzymes. N2O production from N fertilized soils was higher than that of control soils (165 vs. 41 pmol h(-1) g(-1)), was higher for crust soil than for rhizosphere soil (108 vs. 97 pmol h(-1) g(-1)), and increased with soil water content (146 vs. 60 pmol h(-1) g(-1)). On average, fungicide (cycloheximide) addition reduced N2O production by 85% while increasing CO2 production by 69%; bactericide (streptomycin) reduced N2O by 53% with mixed effects on CO2 production. N2O production was significantly correlated with C and N mineralization potential as measured by assays for glycosidic and proteolytic enzymes, and with extractable nitrate and ammonium. Our data indicate that fungal nitrifier denitrification and bacterial autotrophic nitrification dominate N transformation in this ecosystem and that N2O production is highly sensitive to soil cover, N deposition and moisture.