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  • Title: Effects of soil warming on soil microbial extracellular enzyme activities with different depths in a young Chinese fir (Cunninghamia lanceolata)plantation of subtropics.
    Author: Zheng W, Zhou JC, Lin WS, Zheng Y, Li C, Li XF, Ji YH, Yang ZJ.
    Journal: Ying Yong Sheng Tai Xue Bao; 2019 Mar; 30(3):832-840. PubMed ID: 30912375.
    Abstract:
    Extracellular enzyme activitie (EEAs) are a sensitive indicator of microbial function and soil organic matter decomposition in response to climate warming. Up to now, most studies of climate warming and their effects on EEAs have been restricted on the relatively carbon rich topsoil (the upper 20 cm of the soil), whereas little is known about EEAs in subsoil (below 30 cm depth). This study focused on the responses of EEAs to soil warming in a subtropical forest at depths of 0-10 cm, 10-20 cm, 20-40 cm and 40-60 cm. The examined extracellular enzymes included β-glucosidase (BG), cellobiohydrolase (CBH), phenoloxidase (PHO) and peroxidase (PEO), all being involved in the C-cycle. The results showed that, 1) warming significantly increased all EEAs (18%-69%) at the depth of 0-10 cm and 10-20 cm. Below the depth of 20 cm, warming did no affect or suppressed EEAs (13%-31%), except increasing PHO (10%) at 20-40 cm. 2) Results from the redundancy analysis showed that the EEAs were mainly driven by ammonium nitrogen (NH4+-N) and soil moisture (M) in organic carbon rich topsoil. Warming enhanced nutrient competition between soil microorganisms and plants. Thus, it increased EEAs to meet NH4+-N demands of microorganisms. In subsoil with relatively low substrate availability, the EEAs were dominated by dissolved organic matter and microbial biomass (MBC). Warming increased dissolved organic matter and thus provided more substrates for microorganisms, which relieved the dependence of microbes on EEAs. Consequently, warming diminished EEAs in subsoils. Our results suggested that EEAs at the four depths showed different responses to warming. In addition, environmental factors accounting for the variances in EEAs under soil warming condition were different at topsoil and subsoil. Paying more attention to microbes at different soil depths has important implications to precisely predict ecosystem C cycling in response to global warming. 土壤微生物胞外酶可有效反映气候变暖对土壤微生物功能和土壤有机质分解的影响.目前关于气候变暖对土壤微生物胞外酶活性(EEAs)影响的相关研究主要关注有机碳含量较丰富的表层土壤(0～20 cm),而对深层土壤(>20 cm)EEAs的研究仍较缺乏.因此,本研究关注土壤增温对亚热带不同深度(0～10 cm、10～20 cm、20～40 cm和40～60 cm)EEAs的影响及主要调控因素,其中微生物胞外酶包括参与碳循环的β-葡萄糖苷酶(BG)、纤维二糖水解酶(CBH)、酚氧化酶(PHO)和过氧化物氧化酶(PEO).结果表明: 土壤增温提高了0～10 cm和10～20 cm土壤所有胞外酶的活性(18%～69%).在20 cm以下的深层土壤中,土壤增温仅显著提高了20～40 cm的PHO(10%),而对其余胞外酶的活性无显著影响或有一定的抑制作用(13%～31%).冗余分析(RDA)结果表明: 在微生物可利用有机碳较丰富的表层土壤中,铵态氮(NH4+-N)和土壤含水率(M)是调控EEAs的主要因素,增温增强了微生物与植物之间的养分竞争,因而提高EEAs以获取微生物所需的养分NH4+-N;而在微生物底物有效性较低的深层土壤中,EEAs主要受可溶性有机质(可溶性有机碳和可溶性有机氮)和微生物生物量(MBC)的影响,增温提高深层土壤可溶性有机质的含量,为微生物提供更多的底物,减少微生物对EEAs的需求,进而降低EEAs.本研究发现,不同深度EEAs对土壤增温具有不同响应,且土壤增温条件下表层和深层土壤的EEAs具有明显不同的调控因素.因此,加强不同深度土壤微生物的研究对于准确评估生态系统碳循环对全球变暖的响应具有重要意义.
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