Resilience and regime shifts in peatland microbial communities: implications for soil functioning

人类在许多方面依赖土壤。它们为我们食用的大多数农作物提供营养、水分和锚定，它们过滤并保持降雨，它们储存大量的碳，这有助于减缓气候变化。土壤也是各种土壤生物的家园，它们在推动地球功能所依赖的地球化学循环方面发挥着重要作用。尽管有这些重要作用，但一系列压力，包括土地管理的变化，土地污染和气候变化正在威胁土壤以及生活在其中的微生物和动物种群。这些压力不仅对土壤功能构成直接威胁，而且还可能产生长期影响，例如使土壤更容易受到极端气候事件的影响，由于气候变化，极端气候事件在世界范围内变得越来越普遍，并可能对生态系统产生破坏性后果。对海洋、湖泊和森林的研究证据表明，热浪和干旱等极端事件可能引发从一种生态系统状态到另一种生态系统状态的突然和戏剧性的转变或制度转变。例如，澳大利亚西海岸的珊瑚礁群落显示，海洋热浪引发了从广阔的海带森林到形成草坪的海藻的突然而戏剧性的转变。这些制度的变化可能对这些生态系统提供的功能产生重大影响。然而，这种状态转变是否发生在土壤中尚不清楚。在这一小笔赠款中，我们想解决三个迄今为止尚未测试的与土壤安全高度相关的问题。首先，我们想知道长期的气候变暖是否会使土壤及其微生物群落更容易受到极端气候事件的影响，并且更难从极端气候事件中恢复过来，即干旱。其次，我们想测试气候对土壤及其微生物群落的长期影响是否使它们更容易受到过渡的影响，或者从一种状态到另一种状态的制度转变，以及这些制度转变是否会降低土壤的功能，例如它们储存碳的能力。最后，我们想看看气候变化对土壤功能的影响是否可以被抑制，例如通过改变植被的管理。我们计划利用一个独特的变暖和植被操纵实验，这是我们几年前在英格兰北方的摩尔屋国家自然保护区的泥炭毯上建立的，由NERC资助。这项实验非常适合这项研究，因为它自2008年以来一直在持续运行，这使我们处于一个独特的位置来检测长期变暖（2017年9年）如何改变土壤及其微生物群落对干旱的适应能力，以及它们对政权转变的敏感性。该实验还包括植被操作处理，这使我们能够测试植被变化，特别是杜鹃花科矮灌木的存在，是否可以抑制气候变化对土壤及其功能的影响。最后，实验是在富含碳的泥炭地上进行的，这些泥炭地不仅与英国土壤安全高度相关，因为它们覆盖了英国大面积的土地表面并储存了大量的碳，而且它们为NERC土壤安全计划增加了一个独特的高度互补的维度。这些问题是NERC土壤安全计划的核心，该计划旨在解决是什么控制着土壤的能力及其抵抗、恢复和最终适应扰动的功能，例如极端气候事件造成的扰动。此外，通过测试我们的问题，我们将获得对微生物群落动态及其与持续和快速环境变化相关的功能的新的、变革性的理解，并产生有助于设计可持续管理策略以保持泥炭地恢复力的知识。

Humans rely on soils in many ways. They provide nutrients, water and anchorage for most of the crops that we eat, they filter and hold onto rainfall, and they store vast amounts of carbon, which helps to mitigate climate change. Soils also are home to a vast diversity of soil organisms, which play major roles in driving the biogeochemical cycles on which the functioning of Earth depends. Despite these important roles, a range of pressures, including changes in land management, land contamination, and climate change are threatening soils and the populations of microbes and animals that live in them. These pressures not only pose immediate threats to soil functioning, but also they could have longer-term impacts, for instance making soils more vulnerable to extreme climatic events, which are becoming more common worldwide as a result of climate change and can have devastating consequences for ecosystems. Evidence from studies of oceans, lakes and forests shows that extreme events, such as heat waves and drought, can trigger sudden and dramatic transitions, or regime shifts, from one ecosystem state to another. For example, reef communities off the western coast of Australia revealed a sudden and dramatic transition from extensive kelp forest to turf-forming seaweeds triggered by marine heatwaves. These regime shifts can have major consequences for the functions that these ecosystems provide. However, whether such regime shifts occur in soils is not really known. In this small grant, we would like to tackle three so far untested questions of high relevance for Soil Security. First, we want to know if long term climate warming makes soils and their microbial communities more vulnerable to, and less able to recover from, extreme climate events, namely drought, which is increasing in frequency. Second, we want to test if long-term effects of climate on soils and their microbial communities make them more vulnerable to transitions, or regime shifts from one state to another, and whether these regimes shifts degrade the functions that soils perform, for example their ability to store carbon. Last, we want to see if these effects of climate change on soil functioning can be dampened, for instance through changing the management of vegetation. We plan to make use of a unique warming and vegetation manipulation experiment that we set up several years ago on blanket peat at Moor House National Nature Reserve, northern England, funded by NERC. This experiment is ideally suited to this study because it has been running continuously since 2008, which puts us in a unique position to detect how long-term warming (9 years in 2017) has altered the resilience of soils and their microbial communities to drought, but also their susceptibility to regime shifts. The experiment also includes a vegetation manipulation treatment, which allows us to test if vegetation change, especially the presence of ericaceous dwarf-shrubs, can dampen effects of climate change on soils and their functioning. And finally, the experiment is on carbon-rich peatlands, which are not only of high relevance for UK Soil Security because they cover a large area of the UK land surface and store vast amounts of carbon, but also they add a distinct and highly complementary dimension to the NERC Soil Security Programme. These questions are at the heart of the NERC Soil Security programme which seeks to resolve what controls the ability of soils and their functions to resist, recover and ultimately adapt, to perturbations, such as those caused by extreme climatic events. Also, by testing our questions, we will gain new, transformative understanding of the dynamics of microbial communities and their functioning in relation to on-going and rapid environment change, and produce knowledge that could help in the design of sustainable management strategies for maintaining resilience in peatlands.