Land-use intensity effects on soil methane cycling microbes in grassland and forest soils

甲烷（CH4）是仅次于二氧化碳的第二大温室气体（GHG）。自2007年以来，目前的大气甲烷浓度正在急剧增加，据推测这主要是人为原因，可能与粮食生产的集约化农业有关。因此，当今农业面临的一项主要挑战是调整土地利用强度，以确保高效且同时可持续的作物耕作系统，以平衡温室气体排放和不断增长的世界人口对粮食的需求。两组完全不同的原核生物对土壤中的CH4循环至关重要。甲烷营养细菌（MOB）通过氧化大气中的甲烷和产甲烷古菌产生的甲烷到达大气之前的甲烷而起到生物CH4过滤器的作用。目前尚不清楚土地利用强度的差异如何控制土壤甲烷循环中这些关键微生物的功能多样性和活性。初步数据表明，在通气良好的草地土壤中，高利用强度对甲烷氧化有不利影响。然而，土地利用强度对甲烷氧化菌和产甲烷菌时空动态的影响几乎一无所知。因此，我们组建了一个跨学科的联盟，由来自土壤科学、微生物学和宏基因组学的专家组成，他们在土壤温室气体排放、甲烷营养和产甲烷原核生物方面具有良好的背景和互补的专业知识。利用最先进的方法的独特组合，我们将利用生物多样性探索的理想环境作为平台，解决关于土地利用强度对土壤甲烷循环中这些关键微生物的功能多样性和活动的影响的紧迫问题。我们制定了一套目标和假设，将在两个工作包中进行测试。WP1将重点研究300个草地和森林土壤中MOB和介导的甲烷通量对土地利用强度的响应，分别通过甲烷通量测量和定性和定量PCR研究甲烷氧化与甲烷营养细菌丰度和多样性以及环境特性之间的关系。在WP2中，我们将重点关注产甲烷和产甲烷营养原核生物活动的季节和日动态（使用偏转录组和甲烷通量数据），以及这种动态在多大程度上受到草地利用强度的影响。我们将重点比较受水影响的组织土壤和通气良好的细体土壤。我们的BE_CH4项目将提供迫切需要的关于草地和森林利用强度对甲烷循环微生物时空动态的影响的知识，最终控制土壤中的甲烷通量。

Methane (CH4) is, beside CO2 the second most important greenhouse gas (GHG). Current atmospheric methane concentrations are strongly increasing since 2007, which is assumed to be predominantly of anthropogenic origin and likely related to intensified agriculture for food production. Thus, one major challenge for today´s agriculture is to adjust land-use intensity to ensure productive and at the same time sustainable crop farming systems to balance GHG emissions and increasing food demands of a growing world population.Two fundamentally different groups of prokaryotes are crucial for CH4 cycling in soils. Methanotrophic bacteria (MOB) act as biological CH4 filter by oxidizing atmospheric CH4 and that CH4, which is produced by methanogenic archaea before it reaches the atmosphere. It is currently unclear how differences in land-use intensity control the functional diversity and activity of these key microorganisms in the soil methane cycle. Preliminary data indicate that high land-use intensity in well aerated grassland soils negatively impacts methane oxidation. However, almost nothing is known about the influence of land-use intensity on spatial and temporal dynamics of methanotrophs and methanogens. We have therefore assembled an interdisciplinary consortium of experts from soil science, microbiology and metagenomics with well-documented background and complementary expertise in soil GHG emissions, methanotrophic and methanogenic prokaryotes. Using a unique combination of state-of-the-art approaches, we will use the ideal setting of the Biodiversity Exploratories as platform to address pressing questions about the effect of land-use intensity on the functional diversity and activity of these key microorganisms in the soil methane cycle.We have laid out a set of objectives and hypotheses that will be tested in two work packages (WP). WP1 focusses on the responses of MOB and mediated methane fluxes to land-use intensity in 300 grassland and forest soils, where the relationship between methane oxidation and abundance and diversity of methanotrophic bacteria and environmental properties will be studied by methane flux measurements and qualitative and quantitative PCR, respectively. In WP2 we will focus on the seasonal and diurnal dynamics in the activity of methanogenic and methanotrophic prokaryotes (using metatranscriptome and methane flux data) and to which extent the dynamics are influenced by grassland land-use intensity. We will focus on comparison between grasslands on water affected Histosols and well-aerated Leptosols.Our project BE_CH4 will contribute urgently needed knowledge on the influence of grassland and forest land-use intensity on spatial and temporal dynamics of methane cycling microbes that ultimately control methane fluxes in soils.