The transmissive critical zone: understanding the karst hydrology-biogeochemical interface for sustainable management

地球表面（土壤和植物）和下面的岩石相互作用，雨水通过土壤流入岩石。土壤赋予水一种化学特征，有时会导致水质下降。这种特征是通过岩石的运动来调节的，然后，当地下水重新出现时，细菌活动会在溪流和河流中出现。因此，地球外层的功能对人类的关键需求至关重要——我们有多少水和水的质量；水从土壤中排出后，土壤的功能有多好。因此，对这些层如何相互作用的研究被称为“临界带”研究。我们的研究项目在当地居民面临重大环境挑战的环境中使用这种“关键区域”研究——在中国农村，一个快速增长的地区，许多人生活在贫困线以下。这是英国和中国的一个联合研究项目。我们将重点关注其中两个挑战：水的可用性和质量，以及关键地带的水运动如何影响地表植被。对这项研究至关重要的是，下面的岩石主要是石灰岩。石灰石很容易溶解，水可以在地下快速流动。因此，土壤可能会干燥得更快（因为地下是自由排水的），而且地表和地下的储水量有限。石灰石在世界范围内分布广泛，特别是在中国，因此这里的研究与世界上许多地方有关。住在集水区的人一般都是靠土地生活的。它为它们提供水和食物，这种现象被称为生态系统提供服务。山坡不太陡的地方，土地表面被大量耕种。这反过来又带来了一些问题，例如，水质很差，硝酸盐（一种存在于肥料中的化学物质）的含量高得危险；植被的清除使岩石暴露出来，限制了土地的使用。当地居民面临的另一个挑战是气候正在变化。雨水输送到集水区的方式一直在变化，以至于水不像以前那样可用。因此，也出现了水资源短缺，这导致作物歉收，从而导致粮食损失。土地利用变化对形成这些生态系统服务很重要，但气候变化可能是居民将面临的最重大威胁之一；科学必须帮助他们为面对这些威胁做好准备，并取得成功。我们的研究将产生当前关键区域功能的模型，然后我们可以从这些模型中研究关键区域功能如何适应不同的环境驱动因素。在这个项目之外，有大量的科学模型已经确定了气候可能如何变化。因此，我们可以利用这一点来运行我们将开发的关键区域功能模型，不仅在土地利用变化的情况下，而且在未来的气候情景下。所有这些研究将有助于了解这个汇水临界区对未来威胁最敏感的地方。然而，重要的是要让需要使用它的人了解这种理解。因此，我们将进行的最后一项活动是在“知识交流”的保护伞下进行的——与那些需要这项研究的人分享我们的发现，并根据他们也拥有的知识调整我们的理解。因此，我们最后但并非最不重要的活动是与那些生活在景观中的人和管理景观的人合作，帮助他们确定他们的活动如何造成最小的伤害，并为他们的生态系统服务提供最大的保护。因此，我们与中国同事的合作至关重要。我们为项目带来了新的技能（例如新的水文建模技能），他们将从中受益。此外，由于英中两国的流域管理实践差异很大，他们将学习其他好的做法，以帮助改善环境，使居民摆脱贫困

The Earth's surface (soil and plants), and the rock underneath interact, linked by rainwater flowing through the soil into the rock. The soil imparts a chemical signature to the water, sometimes bad leading to loss of water quality. This signature is mediated by movement through the rock, and then, when underground water re-emerges, in streams and rivers by bacterial activity. As such, how this outer layer of planet Earth functions is 'critical' to key needs of mankind - how much water we have available and its quality; how well the soil functions as a result of water draining through it. The study of how these layers interact is thus called 'critical zone' research.Our research programme uses such 'critical zone' research in an environment where the local residents face significant environmental challenges - in rural China, an area of rapid growth and where many live under the poverty line. This is a joint research programme between UK and China. We will focus on two of these challenges: water availability and quality, and how movement of water in the critical zone influences surface vegetation. Crucial to this research is that the underlying rock is mostly limestone. Limestone is easily dissolved and water can move very quickly through the subsurface. So soils may dry sooner (as the subsurface beneath is freely-draining) and there is limited water storage on the surface and underground. Limestone is widely distributed world-wide, but particularly in China and so study here is relevant to many world-wide.The people living in the catchment generally live-off-the-land. It provides their water and food - a phenomenon known as the ecosystem providing services. Where the slopes are not too steep, the land surface is heavily-cultivated. This in turn presents problems e.g., the water quality is poor, with dangerously high-level of nitrate (a chemical that is found in fertiliser); clearance of vegetation exposes rock, limiting how land may be used. Further challenging to local residents is that the climate is changing. How rain is delivered to the catchment has been changing such that water is not available as before. Thus there have also been water shortages, and this led to crop failure and so loss of food.Land use change is important in shaping these ecosystem services, but climate change may be one of the most significant threats the residents will face; science must help them prepare for facing these threats with successful outcomes. Our research will generate models of how the critical zone functions currently and from these we can then investigate how the critical zone functioning may adapt to different environmental drivers. There is a large body of scientific modelling outside this project that has identified how the climate may change. Thus, we can draw on this to run the models we will develop of the critical zone functioning, not only under land use change, but also under future climate scenarios.All this research will contribute to understanding where this catchment critical zone is most sensitive to future threats. However, it is important that this understanding reaches the people who need to use it. So the final activity we will undertake comes under the umbrella of 'knowledge exchange' - sharing our findings with those who need this research, and adjusting our understanding based on knowledge they too have. Thus our last, but not least, activity is working with those who live in the landscape and those who manage it, to help them identify how their activities can cause the least harm and offer the most protection to their ecosystem services. Our collaboration with Chinese colleagues is therefore crucial. We bring new skills to the project (e.g. new hydrological modelling skills) that they will benefit from. Additionally as catchment management practices will be quite different across UK-China, they will learn about other good practice to help improve their environment and remove residents from poverty