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，目前大气中的甲烷浓度正在大幅增加，据推测，这主要是人为造成的，可能与粮食生产的强化农业有关。因此，当今农业面临的一个主要挑战是调整土地利用强度，以确保生产力，同时可持续的作物种植系统，以平衡温室气体排放和不断增长的世界人口不断增加的粮食需求。两种根本不同的原核生物对土壤中的CH4循环至关重要。甲烷氧化菌（MOB）通过氧化大气中的甲烷以及由产甲烷古菌产生的甲烷到达大气之前的甲烷，起到生物甲烷过滤器的作用。目前尚不清楚土地利用强度的差异如何控制这些关键微生物在土壤甲烷循环中的功能多样性和活性。初步数据表明，高土地利用强度在良好的通气草原土壤产生负面影响甲烷氧化。然而，几乎没有什么是已知的土地利用强度对甲烷氧化菌和产甲烷菌的时空动态的影响。因此，我们组建了一个由土壤科学、微生物学和宏基因组学专家组成的跨学科联盟，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丰富的背景和互补的专业知识。我们将利用生物多样性探索站的理想环境作为平台，采用最先进的方法进行独特的组合，以解决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性的影响等紧迫问题。我们已经制定了一系列目标和假设，将在两个工作包（WP）中进行测试。WP1侧重于MOB和介导的甲烷通量的响应，土地利用强度在300草地和森林土壤，甲烷氧化和甲烷氧化菌的丰度和多样性和环境属性之间的关系将分别通过甲烷通量测量和定性和定量PCR研究。在WP 2中，我们将专注于产甲烷和甲烷营养原核生物的活动的季节性和昼夜动态（使用元转录组和甲烷通量数据），并在何种程度上的动态草原土地利用强度的影响。我们将重点关注受水影响的组织土和通气良好的轻质土上的草原之间的比较。我们的项目BE_CH4将提供急需的知识，了解草原和森林土地利用强度对甲烷循环微生物时空动态的影响，这些微生物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.