From microbe to mountain (research at Moor House)
Biodiversity encompasses variation from the smallest soil microbes, through to the whole landscape level. On the moorlands of northern England, researchers are looking at how diversity at different scales affects carbon cycling
To many of us, the words ‘moorland’ and ‘peatland’ conjure up images of bleak, cold, wet places. Yet the UK’s moorlands are valuable for the goods and services they provide; benefits that we call ‘ecosystem services’. These areas are valuable for their biodiversity, for recreation, and for the supply of fresh drinking water, as many rivers have their sources high up on the moors. Moorlands also play an important role in regulating our climate due to the amount of carbon they take up (or sequester) from the atmosphere. Stocks of carbon in peat have built up over thousands of years due to plant photosynthetic uptake of carbon (as carbon dioxide) exceeding losses of carbon via decomposition, respiration and erosion. This is due largely to very slow rates of decomposition in the cold, wet environment. Changes in climate and in the way we manage our land could upset this balance, leading to the release of carbon back to the atmosphere as carbon dioxide or methane, or into water as dissolved organic carbon.
The aim of our research is to find out what factors control carbon inputs and outputs (fluxes) in peat and the degree to which biodiversity regulates these processes, at a range of scales from single species to whole landscapes. To do this we have been conducting a series of experiments that monitor carbon fluxes across sites with different plants and different depths of peat. Our work is at Moor House National Nature Reserve (NNR) in the north Pennines of England. This ECN site has been used for ecological research for over 50 years, and the wealth of data available from ECN are of great value to our research. For example, continuous monitoring by ECN gives us accurate and up-to-date weather and climate information, while longer term records allow us to look back at previous conditions and measurements to find out what has been changing over the years. In addition to standard ECN measurements, we are measuring fluxes of greenhouse gases such as carbon dioxide and methane, levels of dissolved organic carbon in water, soil nutrients and rates of decomposition. We have found that these differ between habitats and between plant species, and we are now investigating the links between carbon cycling and biodiversity.
A sheep’s eye view
One of the first things to notice when visiting moorlands is the wide range of plants found growing in different habitats. Sphagnum mosses and rushes grow in damp areas whereas grasses and shrubs prefer dryer hummocks. The way we manage the land also affects the plants that grow there, with grazing by sheep and controlled burning as part of grouse moor management reducing the amount of heather and encouraging grasses. Each plant group has a different set of traits, or characteristics, which affect the amount of carbon they can take up from the atmosphere. For example, grasses and sedges such as cotton grass are able to take up much more carbon than slow growing Sphagnum mosses. Similarly, the amount of carbon returned to the atmosphere as the plants and soil organisms respire is different for each plant group. As far as inputs and outputs of carbon are concerned, biodiversity of moorland plants certainly matters.
A worm’s eye view
We know far less about the diversity below our feet. Small soil organisms, ranging from microscopic bacteria and fungi to mites, collembola and enchytraid worms, provide carbon cycling services: they decompose dead organic matter and release carbon and nitrogen from the soil back into the atmosphere. We are using new molecular techniques to measure how diverse the soil microbial communities are, and how important they are to carbon cycling.
A bird’s eye view
Looking down on Moor House from above, the patchwork of plant communities is clearly visible. Far from being an endless expanse of brown, moorlands are mottled landscapes marked by hummocky heather, stark areas of plant-free eroding peat, and branching gullies. These distinctive landforms are inhabited by different plant communities, with different sets of traits and capacities for carbon cycling. We might also expect the microbial communities to differ between moorland landforms, since there are strong connections between biodiversity above and below ground. Crucially, for estimating how much carbon is stored below ground, the depth of peat varies between landforms, being particularly shallow in gullies.
Integrating the scales
It is important to consider the different moorland landforms – heather moorland, eroding peat and gullies – when estimating the carbon cycling potential of the landscape as a whole. We’re currently investigating the relationships between plants, microbes and carbon cycling in the three landforms, in addition to measuring fluxes of greenhouse gases. Since heather moorland, eroding patches and gullies are easily-distinguishable from the air, we can use high-resolution aerial photography in combination with spatial statistics to scale-up plot-level biodiversity information to the landscape scale. Ultimately, we hope to use this landscape-scale information to improve the accuracy of peatland carbon cycling models.
In addition to threats to biodiversity, one of the greatest global issues is climate change. We need to establish how changes in climate will interact with changes in biodiversity to affect carbon cycling. For this, we have set up a new experiment at Moor House. We are increasing the temperature within small vegetation enclosures, to explore the effects of warming and vegetation change on carbon cycling. Initial results indicate that vegetation type and warming are important, and that these two factors interact to influence carbon cycling processes.
Improving management of carbon stocks
In summary, biodiversity varies at all levels in moorlands, from plant and microbial species through to habitats in the landscape. By understanding more about how each level of diversity affects carbon cycling we can improve our knowledge of how peatland carbon cycling works and make better predictions of the future carbon storage potential of these ecosystems. This in turn should help to inform landowners how best to manage this land to balance their immediate needs with the need to preserve biodiversity and ensure these environments continue to function as major stores of carbon. The wealth of ECN and other data collected at Moor House makes it an ideal site for this research.
Dr Sue Ward is a Research Associate at Lancaster University [email Sue]
Mike Whitfield is a PhD student at CEH Lancaster [email Mike]
All the research described was undertaken on NERC funded projects with Lancaster University and CEH Lancaster