Soil Biology Group, Wageningen University and Research, Wageningen, The Netherlands.
Manaaki Whenua - Landcare Research, Lincoln, New Zealand.
Glob Chang Biol. 2021 Dec;27(23):6217-6231. doi: 10.1111/gcb.15878. Epub 2021 Sep 28.
Climate warming may be exacerbated if rising temperatures stimulate losses of soil carbon to the atmosphere. The direction and magnitude of this carbon-climate feedback are uncertain, largely due to lack of knowledge of the thermal adaptation of the physiology and composition of soil microbial communities. Here, we applied the macromolecular rate theory (MMRT) to describe the temperature response of the microbial decomposition of soil organic matter (SOM) in a natural long-term warming experiment in a geothermally active area in New Zealand. Our objective was to test whether microbial communities adapt to long-term warming with a shift in their composition and their temperature response that are consistent with evolutionary theory of trade-offs between enzyme structure and function. We characterized the microbial community composition (using metabarcoding) and the temperature response of microbial decomposition of SOM (using MMRT) of soils sampled along transects of increasing distance from a geothermally active zone comprising two biomes (a shrubland and a grassland) and sampled at two depths (0-50 and 50-100 mm), such that ambient soil temperature and soil carbon concentration varied widely and independently. We found that the different environments were hosting microbial communities with distinct compositions, with thermophile and thermotolerant genera increasing in relative abundance with increasing ambient temperature. However, the ambient temperature had no detectable influence on the MMRT parameters or the relative temperature sensitivity of decomposition (Q ). MMRT parameters were, however, strongly correlated with soil carbon concentration and carbon:nitrogen ratio. Our findings suggest that, while long-term warming selects for warm-adapted taxa, substrate quality and quantity exert a stronger influence than temperature in selecting for distinct thermal traits. The results have major implications for our understanding of the role of soil microbial processes in the long-term effects of climate warming on soil carbon dynamics and will help increase confidence in carbon-climate feedback projections.
如果气温升高刺激土壤碳向大气中流失，可能会加剧气候变暖。这种碳-气候反馈的方向和幅度尚不确定，主要是因为缺乏对土壤微生物群落生理学和组成的热适应的了解。在这里，我们应用大分子速率理论 (MMRT) 来描述在新西兰一个地热活跃地区的自然长期变暖实验中土壤有机质 (SOM) 微生物分解的温度响应。我们的目标是测试微生物群落是否通过其组成的变化和与其结构和功能权衡进化理论一致的温度响应来适应长期变暖。我们通过宏条形码技术来描述微生物群落组成（使用宏条形码技术），并通过 MMRT 来描述 SOM 微生物分解的温度响应（使用 MMRT），对沿来自一个包含两个生物群落（一个灌木丛和一个草原）的地热活动区的距离增加的横断面取样的土壤进行了特征描述，并在两个深度（0-50 和 50-100 毫米）进行了取样，以便环境土壤温度和土壤碳浓度广泛且独立地变化。我们发现，不同的环境中存在着具有不同组成的微生物群落，随着环境温度的升高，嗜热菌和耐热菌的相对丰度增加。然而，环境温度对 MMRT 参数或分解的相对温度敏感性 (Q) 没有可检测的影响。MMRT 参数与土壤碳浓度和碳：氮比强烈相关。我们的研究结果表明，虽然长期变暖选择了适应温暖的类群，但底物质量和数量比温度对选择具有不同热特性的微生物群落具有更强的影响。这些结果对我们理解土壤微生物过程在气候变暖对土壤碳动态的长期影响中的作用具有重大意义，并有助于提高对碳-气候反馈预测的信心。
