Carbon and Nitrogen Amendments Lead to Differential Growth of Bacterial and Fungal Communities in a High-pH Soil

Pramod N.KAMBLE; Erland B(AA)TH

摘要

Microbial growth in soil is mostly limited by lack of carbon (C).However,adding fresh,C-rich litter can induce nitrogen (N) limitation.We studied the effect of alleviating C and N limitation in high-pH (＞ 8) soils,soils expected to favor bacterial over fungal growth.Nitrogen limitation was induced by incubating soils amended with C-rich substrate (starch or straw) for 4 weeks.Limiting nutrients and the effects of alleviating limitation were then studied by adding C (as glucose) or N (as NH4NO3) and measuring microbial growth and respiration after 4 d.In non-amended,C-limited soils,adding C but not N increased both microbial respiration and bacterial growth.In N-limited,substrate-amended soils,adding C increased respiration,whereas adding N increased both microbial respiration and growth.Inducing N limitation by amending with straw was most easily detected in increased fungal growth after the addition of N,whereas with starch,only bacterial growth responded to alleviating N limitation.Compared to earlier results using a low-pH soil,the effect of substrate used to induce N limitation was more important than pH for inducing bacterial or fungal growth after alleviating N limitation.Furthermore,we found no evidence that alleviating N limitation resulted in decreased respiration concomitant with increased microbial growth in soil,suggesting no drastic changes in C use efficiency.

机译：土壤中微生物的生长主要受到碳（C）缺乏的限制。但是，添加新鲜，富含C的垫料会引起氮（N）的限制。我们研究了缓解高pH条件下C和N限制的作用（＞ 8）土壤，预期比细菌生长更有利于细菌的土壤。通过将富含C的底物（淀粉或稻草）改良的土壤培养4周来诱导氮限制。然后研究通过添加C（作为葡萄糖）限制营养和减轻限制的作用。）或N（以NH4NO3的形式），并在4 d后测量微生物的生长和呼吸。在非改良的C限制土壤中，添加C但不增加N会增加微生物呼吸和细菌生长。在N受限的底物改良土壤中，添加C增加了呼吸作用，而添加N则增加了微生物呼吸作用和生长。添加N后最容易检测到通过秸秆改良引起的N限制，而添加淀粉后，只有细菌生长才缓解N限制。与使用低pH值土壤的早期结果相比，用于减轻氮含量的底物在减轻氮含量限制后对诱导细菌或真菌生长的作用比pH值更为重要。此外，我们没有发现减轻氮含量导致呼吸下降的证据。伴随着土壤微生物生长的增加，这表明碳利用效率没有急剧变化。

Carbon and Nitrogen Amendments Lead to Differential Growth of Bacterial and Fungal Communities in a High-pH Soil

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