Moor House National Nature Reserve Research Articles

Effects of long-term removal of sheep-grazing in a series of British upland plant communities: Insights from plant species composition and traits

Environmental and management pressures are considered a threat for preserving plant communities worldwide. Identification of long-term impacts of changing management practices on plant community composition must, therefore, be a major priority to ensure improvement in conservation value. Land abandonment/wilding is one topical area where there is little available information on long-term impacts. To address this, here, we describe plant species compositional change over relatively long-time scales in a range of four British upland communities (high-level grasslands, intermediate grasslands, blanket bogs and high-level bogs) and its relationships with a series of life-history and plant trait variables. Our aims were to determine whether the business-as-usual sheep grazing practice was maintaining these communities, and if grazing was to be removed as part of abandonment/wilding strategies, would there be a conservation benefit. We used a series of long-term experimental grazing-exclosure studies at twelve sites (>40 years) on the Moor House National Nature Reserve in northern England. Each site consisted of paired plots; i.e. sheep-grazed versus ungrazed. Our results showed that there was relatively little change in dominant plant species with most change occurring within sub-dominant species. Similarly, different temporal responses in plant species richness were detected between the experiments (richness was reduced in three experiments, only one increased). In any case, the vegetation temporal trajectories were moving in similar direction in grazed and ungrazed plots at most sites. Interestingly, blanket bog experiments showed a clear compositional convergence for both grazed and ungrazed plots, although, the between-site differences related to a combination of elevation and past burning testament. Finally, the bryophytes (especially liverworts) and lichens were the groups that contributed most to the reductions in species richness. Moreover, implementation of a no-stock grazing strategy under a land abandonment/wilding approach will not bring about much plant change in the short-term in the plant communities studied here.

Release from sheep‐grazing appears to put some heart back into upland vegetation: A comparison of nutritional properties of plant species in long‐term grazing experiments

AbstractRewilding or wilding is a popularised means for enhancing the conservation value of marginal land. In the British uplands, it will involve a reduction, or complete removal, of livestock grazing (sheep), based on the belief that grazing has reduced plant species diversity, the ‘Wet Desert’ hypothesis. The hope is that if livestock is removed, diversity will recover. If true, we hypothesise that the species extirpated/reduced by grazing and then recover on its removal would more nutritious compared to those that persisted. We test this hypothesis at Moor House National Nature Reserve (North‐Pennines), where seven sets of paired plots were established between 1953 and 1967 to compare ungrazed/sheep‐grazed vegetation. Within these plot‐pairs, we compared leaf properties of seven focal species that occurred only, or were present in much greater abundance, in the absence of grazing to those of 10 common species that were common in both grazed and ungrazed vegetation. Each sample was analysed for macro‐nutrients, micro‐nutrients, digestibility, palatability and decomposability. We ranked the species with respect to 22 variables based on effect size derived from Generalised Linear Modelling (GLM) and compared species using a Principal Components Analysis. We also assessed changes in abundance of the focal species through time using GLMs. Our results support the ‘Wet Desert’ hypothesis, that is, that long‐term sheep grazing has selectively removed/reduced species like our focal ones and on recovery, they were more nutritious (macro‐nutrients, some micro‐nutrients) palatable, digestible and decomposable than common species. Measured changes in abundance of the focal species suggest that their recovery will take 10–20 years in blanket bog and 60 years in high‐altitude grasslands. Collectively, these results suggest that sheep grazing has brought about biotic homogenization, and its removal in (re)wilding schemes will reverse this process eventually! The ‘white woolly maggots’ have eaten at least part of the heart out of the highlands/uplands, and it will take some time for recovery.

Thermodynamic Control of the Carbon Budget of a Peatland

AbstractThe transformations and transitions of organic matter into, through, and out of an ecosystem must obey the second law of thermodynamics. This study considered the transition in the solid components of the organic matter flux through an entire ecosystem. Organic matter samples were taken from each organic matter reservoir and fluvial transfer pathway in a 100% peat‐covered catchment (Moor House National Nature Reserve, North Pennines, UK) and were analyzed by elemental analysis and bomb calorimetry. The samples analyzed were as follows: bulk aboveground and belowground biomass; individual plant functional types (heather, mosses, and sedges); plant litter layer; peat soil; and samples of particulate and dissolved organic matter (POM and DOM). Samples were compared to standards of lignin, cellulose, and plant protein. It was possible to calculate: enthalpy of formation ( ); entropy of formation ( ); and Gibbs free energy of formation ( ) for each of the samples and standards. The increase (decreasing negative values) in through the ecosystem mean that for all but litter production, the transformations through the system must be balanced by production of low (large negative values) products, not only CO2 or CH4 but also DOM. The change in down the peat profile shows that reaction of the soil organic matter decreases or even ceases at depth and the majority of the reaction has occurred above 40 cm below the surface. This approach represents a new objective way to test and trace organic matter transformations in and through an ecosystem.

A Molecular Budget for a Peatland Based Upon 13C Solid‐State Nuclear Magnetic Resonance

AbstractPeatlands can accumulate organic matter into long‐term carbon (C) storage within the soil profile. This study used solid‐state 13C nuclear magnetic resonance (13C‐NMR) to investigate the transit of organic C through a peatland ecosystem to understand the molecular budget that accompanies the long‐term accumulation of C. Samples of biomass, litter, peat soil profile, particulate organic matter, and dissolved organic matter (DOM) were taken from the Moor House National Nature Reserve, a peat‐covered catchment in northern England where both the dry matter and C budget for the ecosystem were known. The results showed that: The interpretation of the 13C‐NMR spectra shows that polysaccharides are preferentially removed through the ecosystem, while lignin components are preferentially retained and come to dominate the organic matter accumulated at depth in the profile. The DOM is derived from the oxidation of both biomass and the degradation of lignin, while the particulate organic matter is derived from erosion of the peat profile. The DOM is differentiated by its proportion of oxidized functional groups and not by its aromatic content. The changes in functionality leading to DOM production suggest side chain oxidation resulting in C‐C cleavage/depolymerisation of lignin, a common reaction within white rot fungi. The 13C‐NMR budget shows that O‐alkyl functional groups are disproportionately lost between primary production and accumulation in the deep peat, while C‐alkyl functional groups are disproportionately preserved. The carbon lost as gases (CO2 and CH4) was estimated to be composed of 93% polysaccharide‐derived carbon and 7% lignin‐derived carbon.

Moorland vegetation responses following prescribed burning on blanket peat

Moorlands provide several key ecosystem services, as well as supporting shooting of red grouse (Lagopus lagopus scotica Latham). Prescribed burning of heather is an integral aspect of grouse-moor management but is sometimes presented as ecologically damaging. However, a long-term burning experiment at Moor House National Nature Reserve, North Pennines, northern England, showed that more frequent burning actually increased the cover of peat-building species such as Sphagnum mosses and cotton grass (Eriophorum vaginatum L.). Here we compare those findings with data from another deep-peat site in the North Pennines, but one that is actively managed as a grouse moor. We describe post-fire vegetation change using aerial images to construct a time-series of burns. Comparable with the Moor House study, we found highest levels of Sphagnum and Eriophorum cover on fires last burned within 3–10 years, whereas heather (Calluna vulgaris L.) cover, that of other mosses, and overall vegetation height all increased in a linear manner over time since burning. These results from an actively managed grouse moor subject to prescribed burning demonstrate that the cover and species richness of Sphagnum, a key peat-forming group, correlated with reduced dominance of tall heather, can benefit from a post-burn period of up to 10 years.

The flux of organic matter through a peatland ecosystem: The role of cellulose, lignin, and their control of the ecosystem oxidation state

This study used thermogravimetric analysis (TGA) to study the transit of organic C through a peatland ecosystem. The biomass, litter, peat soil profile, particulate organic matter (POM), and dissolved organic matter (DOM) fluxes were sampled from the Moor House National Nature Reserve, a peat-covered catchment in northern England where both the dry matter and carbon budget for the catchment were known. The study showed that although TGA traces showed distinct differences between organic matter reservoirs and fluxes, the traces could not readily be associated with particular functionalities or elemental properties. The TGA trace shows that polysaccharides are preferentially removed by humification and degradation with residual peat being dominated by lignin compositions. The DOM is derived from the degradation of lignin while the POM is derived from erosion of the peat profile. The carbon lost as gases (CO2 and CH4) was estimated to be composed of 92 to 95% polysaccharide carbon. The composition of the organic matter lost from the peat ecosystem means that the oxidative ratio (OR) of the ecosystem experienced by the atmosphere was between 0.96 and 0.99: currently, the Intergovernmental Panel on Climate Change uses an OR value of 1.1 for all ecosystems.

Gully hotspot contribution to landscape methane (CH 4) and carbon dioxide (CO 2) fluxes in a northern peatland

Peatlands are long term carbon catchments that sink atmospheric carbon dioxide (CO 2) and source methane (CH 4). In the uplands of the United Kingdom ombrotrophic blanket peatlands commonly exist within Calluna vulgaris (L.) dominated moorland ecosystems. These landscapes contain a range of topographical features that influence local hydrology, climate and plant community composition. In this study we examined the variation in ecosystem CO 2 respiration and net CH 4 fluxes from typical plant-soil systems in dendritic drainage gullies and adjacent blanket peat during the growing season. Typically, Eriophorum spp., Sphagnum spp. and mixed grasses occupied gullies while C. vulgaris dominated in adjacent blanket peat. Gross CO 2 respiration was highest in the areas of Eriophorum spp. (650 ± 140 mg CO 2 m − 2 h − 1 ) compared to those with Sphagnum spp. (338 ± 49 mg CO 2 m − 2 h − 1 ), mixed grasses (342 ± 91 mg CO 2 m − 2 h −1) and C. vulgaris (174 ± 63 mg CO 2 m − 2 h − 1 ). Measurements of the net CH 4 flux showed higher fluxes from the Eriophorum spp (2.2 ± 0.6 mg CH 4 m − 2 h − 1 ) locations compared to the Sphagnum spp. (0.6 ± 0.4 mg CH 4 m − 2 h − 1 ), mixed grasses (0.1 ±0.1 mg CH 4 m − 2 h − 1 ) and a negligible flux detected from C. vulgaris (0.0 ± 0.0 mg CH 4 m − 2 h − 1 ) locations. A GIS approach was applied to calculate the contribution of gullies to landscape scale greenhouse gas fluxes. Findings from the Moor House National Nature Reserve in the UK showed that although gullies occupied only 9.3% of the total land surface, gullies accounted for 95.8% and 21.6% of the peatland net CH 4 and CO 2 respiratory fluxes, respectively. The implication of these findings is that the relative contribution of characteristic gully systems need to be considered in estimates of landscape scale peatland greenhouse gas fluxes.

A Record of Atmospheric Pollution and Vegetation Change as Recorded in Three Peat Bogs from the Northern Pennines Pb-Zn Orefield

The metal mining landscape of the northern Pennines is unique, containing a relatively large concentration of mines dating back possibly to the Roman period. Little attention, however, has been given to understanding how the metal mining industry has altered the natural landscape. This paper sets out to address this by using palaeoenvironmental techniques to reconstruct the vegetational landscape and atmospheric pollution history surrounding the metal mines of the upper Rookhope valley, Weardale and Moorhouse National Nature Reserve in Teesdale. Results from pollen analysis suggest that small, temporary woodland clearance occurred during the Neolithic and Bronze Age, followed by more substantial clearances during the Iron Age and Romano-British period. Metal mining had little impact on vegetation, in particular woodland, until Medieval times. Evidence of higher lead concentrations and a permanent reduction in arboreal pollen percentages in the pollen diagrams correlate with the growth of the lead mining industry from the eleventh century AD onwards as documented in historical records.

A Record of Atmospheric Pollution and Vegetation Change as Recorded in Three Peat Bogs from the Northern Pennines Pb-Zn Orefield

The metal mining landscape of the northern Pennines is unique, containing a relatively large concentration of mines dating back possibly to the Roman period. Little attention, however, has been given to understanding how the metal mining industry has altered the natural landscape. This paper sets out to address this by using palaeoenvironmental techniques to reconstruct the vegetational landscape and atmospheric pollution history surrounding the metal mines of the upper Rookhope valley, Weardale and Moorhouse National Nature Reserve in Teesdale. Results from pollen analysis suggest that small, temporary woodland clearance occurred during the Neolithic and Bronze Age, followed by more substantial clearances during the Iron Age and Romano-British period. Metal mining had little impact on vegetation, in particular woodland, until Medieval times. Evidence of higher lead concentrations and a permanent reduction in arboreal pollen percentages in the pollen diagrams correlate with the growth of the lead mining industry from the eleventh century AD onwards as documented in historical records.

Use of 14C carbon dating to determine feeding behaviour of enchytraeids

There is a lack of information about the trophic position of enchytraeid species, and it is unknown whether their vertical distribution in the soil corresponds to different feeding strategies. This study, for the first time, employs radiocarbon techniques to investigate the in situ feeding behaviour of enchytraeids. Soil cores including the associated vegetation were taken from a cambic stagnohumic gley near the summit of Great Dun Fell (845m) in 1996. Since enchytraeid populations are known to be affected by changes in temperature and moisture regimes in upland soils, additional sampling was carried out at the soil warming experiment at the same site. Soil cores were also taken from a blanket bog on Hard Hill (560m) at Moor House National Nature Reserve in 1998. All cores were sliced in the field into five layers, each of 2cm, to a total depth of 10cm. A subsample of each layer was used for animal extraction, and a parallel soil sample was used for 14C isotope analysis. Results indicate that enchytraeids assimilate carbon components which are predominantly of material that is ca. 5–10 years old. The vertical movements of the worms due to changing abiotic factors do not affect this as they show similar values at all depths. However, in response to warming, they could have changed their C source as a lower 14C enrichment with depth was observed in the heated samples.

Insects and plants in a changing atmosphere

This is the winter meeting for the year 2000, a year in which we all spent some time looking to the past as well as considering the opportunities and challenges of the future. For this Society, founded in 1913, the 20th century was the formative time. It progressed from its origins in the Vegetation Committee, through the initial rather separate growth of animal ecology and the launching of the Journal of Animal Ecology in 1932, to the present interdisciplinary view of our subject in which terms like molecular ecology are common place. Having had the privilege of being a member of the society for almost half of that period I found myself reflecting on the circumstances which encouraged me to go along my particular ecological track. Like most biologists of my generation I followed separate A-levels in botany and zoology with a specialist university training in one of these, in my case zoology. However, this was soon to change. The new universities of the 1960s were establishing departments of biological sciences and the oldest had begun to teach ecology in year one as an integrated subject (Varley et al. 1967). I was much influenced by these developments and, I suppose, also by my background from the then heavily polluted industrial East Lancashire uplands. I count myself lucky that the ecology I was taught was wide-ranging and had an interdisciplinary element, whilst the organisms I chose to work on (phytophagous insects) were better botanists than I was! I was fortunate to have the opportunity to participate in J.B. Cragg's programme of upland ecology at the Moor House National Nature Reserve (Cragg 1961) and later had the similar good fortune to work at Wytham Woods. The former is an area much admired and written about

Standardisation of temperature observed by automatic weather stations.

Daily mean, maximum and minimum surface air temperature data were gathered from a network of automatic weather stations (AWS) within the Moor House National Nature Reserve in northern England. Five AWS were installed next to the official Environmental Change Network weather station at Moor House. Data were compared graphically and correction constants were calculated to adjust data from each AWS to the standard of the official station by optimising the concordance correlation coefficient. Each corrected station was re-located next to one of five in-situ stations in and around the reserve, allowing correction of all temperature sensors to a common standard. The mean error associated with measured daily mean, maximum and minimum temperature for each sensor does not exceed +/- 0.2 K. The procedure quantifies a source of systematic measurement error, improving the identification of spatial temperature differences between stations.

Enchytraeid worms (Oligochaeta) enhance mineralization of carbon in organic upland soils

SummaryWe investigated the functional role of enchytraeid worms (Oligochaeta) in organic upland soils experimentally, because that role of these animals is little known. We made microcosms of intact soil cores cut from two depths, 0–4 cm and 4–8 cm, of a Cambic Stagnohumic Gley from the Moor House National Nature Reserve (UK). Enchytraeids were added to half of the microcosms, resulting in four treatments: litter (L), litter + enchytraeids (L + E), soil (S) and soil + enchytraeids (S + E). Triplicates of each treatment were established, and all microcosms (60) were then incubated in the dark at 15°C, arranged in a fully randomized design. The experiment ran over 110 days, with five destructive harvests at days 10, 25, 50, 75 and 110, when microbial measurements (soil respiration and biomass C) as well as measures of decomposition (nutrient concentration in leachates) were made. Enchytraeids almost doubled the availability of organic carbon (measured as dissolved organic carbon in soil leachates) in the surface (0–4 cm) microcosms only. There were no effects of enchytraeids on the release of inorganic N or P from either soil horizon, although the release of ammonium and phosphate was correlated with the number of enchytraeids in the microcosms. The depth from which the soil was taken exerted a strong influence on nutrient leaching, with almost six times more ammonium and four times more carbon being leached from the surface (0–4 cm) layer than from the more decomposed (4–8 cm) horizon. There was little nitrate leaching from any of the treatments, with only one‐quarter as much nitrate leached from the surface (0–4 cm) as from the subsurface (4–8 cm) horizon. Enchytraeids had no detectable effect on microbial biomass, but they increased microbial respiration by 35% in the surface (0–4 cm) horizon. Because they enhanced microbial activity in this horizon we suggest that enchytraeids indirectly drive the processes of decomposition and nutrient mineralization in organic upland soils.

Runoff generation and water table fluctuations in blanket peat: evidence from UK data spanning the dry summer of 1995

Understanding of the hydrology of upland blanket peatlands has been limited both by the logistical difficulties of obtaining data from such environments and by technical difficulties with plot scale investigations of peat hydrology. The relative importance of infiltration-excess and percolation-excess as runoff generating mechanisms as opposed to the saturation-excess mechanism remains unclear. This study uses catchment-scale runoff data, in combination with monitoring of water table levels, to identify the relative importance of these mechanisms for an upland peat catchment within the Moor House National Nature Reserve in the UK. Mean runoff coefficients for the catchment are 0.4 and the flood hydrographs are flashy. Monitored water table in the catchment is within 5 cm of the surface (i.e. within the acrotelm) 93% of the time. High stream flows always occur at times of high water table suggesting that overland and near surface runoff is controlled by saturation of the catotelm rather than by infiltration capacity. Depressed rates of water table recovery at the end of a prolonged period of low water table in 1995 suggest possible physical changes once the peat has dried out. The likelihood that such periods of low water table will become more common under global warming scenarios raises concern over the impact of such changes: increased erosion, water discoloration, and increased CO 2 flux may result.

Long-term rainfall and streamflow records for north central England: putting the Environmental Change Network site at Moor House, Upper Teesdale, in context

Long-term rainfall and streamflow records for the Moor House National Nature Reserve and sites close by in the northern Pennines are analysed in order to place observations made since 1991 as part of the UK Environmental Change Network (ECN) in context. Rainfall records for the Durham Observatory since 1880 and streamflow for the River Wear at Durham since 1958 provide a regional setting within which the upland records can be assessed. Since 1991, the most notable event has been the drought of the 1995 summer which followed one of the wettest winters on record. A strong tendency is noted for increased hydrological variability recently, with the contrast between winter and summer becoming more extreme, both for rainfall and runoff.

Cognettia sphagnetorum (Enchytraeidae) and nutrient cycling in organic soils: a microcosm experiment

A microcosm experiment was carried out to investigate the role of enchytraeids in nitrogen and phosphorus mineralisation in an organic grassland soil. Soil cores were taken from a cambic stagnohumic gley with associated vegetation in the Moor House National Nature Reserve (UK), defaunated, separated into 3 cm layers and inoculated with Cognettia sphagnetorum (Vejdovsky) in microcosms, maintained at 15°C in the laboratory. The leaching of dissolved organic nitrogen (DON), ammonium and phosphorus (total, organic and soluble reactive phosphorus) was monitored over 8 weeks, and found to be significantly greater in the presence of C. sphagnetorum; this effect varied with soil depth, highest increases being found in the 0–3 and 3–6 cm soil layers. The pH in the leachates was also increased in the presence of Cognettia. The impacts of seasonal vertical distribution of enchytraeids on nutrient cycling are discussed, together with the implications of climate change in these systems.

The dynamics of dissolved nitrogen in a blanket peat dominated catchment

Precipitation, soil solution and drainage water were collected from a blanket peat catchment at Moor House National Nature Reserve in the Northern Pennine Uplands, UK, an area of moderately high N deposition. Two tributaries of the main stream were also sampled. Between 1993 and 1995 samples were analysed for NH 4 + and NO 3 − and for part of the period for organic N. Inputs of N in precipitation exceeded outputs in stream water. Organic N represented a small proportion of N inputs while inputs of inorganic N averaged 10.2 kg ha −1 a −1. Soil solution from 10 cm depth in the peat was dominated by organic N whereas at 50 cm NH 4 + slightly exceeded organic N. NO 3 − was rarely detected at either depth except during a period of exceptionally warm and dry weather in 1995. Output fluxes in stream water of organic N (5.7 to 6.5 kg ha −1 a −1) were much greater than those of inorganic N (0.6 to 2.2 kg ha −1 a −1). Inorganic N in streams was predominantly NO 3 − except in the smallest stream which had the largest concentrations of NH 4 +. This suggests that N transformations, particularly nitrification, may be taking place in the mineral soils adjacent to the streams or within the stream channel of the larger catchment.

Effects of climate change on soil fauna; responses of enchytraeids, Diptera larvae and tardigrades in a transplant experiment

A transplant experiment was carried out on the Moor House National Nature Reserve, Cumbria, UK, and two sites with different climatic characteristics were selected for determining how Enchytraeids, Diptera larvae and Tardigrades respond to changes in climate. The soil was a cambic stagnohumic gley, characterized by a high organic matter content and low pH. Vegetated soil cores were taken from near the summit of Great Dun Fell (GDF) and used for the transplant experiment. Cores were then placed back at GDF (845 m) and also transplanted to Sink Beck (SNK, 480 m), providing a mean annual temperature increase of 2.5°C. In order to discriminate between the effects of temperature and rainfall on the size and vertical distribution patterns of the fauna, a further series of lysimeters were established at SNK, and rainfall inputs were manipulated, intending to provide a total input equivalent to the ambient rainfall at the top site. At regular intervals, a number of cores were destructively sampled from each treatment (top site—GDF; lower site—SNK; enhanced rainfall inputs-SNK) and the vertical distribution of the soil fauna determined. Enchytraeidae, Tardigrada and Diptera were commonly found in soil samples at the Reserve and appeared sensitive to the imposed changes in temperature and moisture. Different species of enchytraeids responded differently: numbers of Cognettia sphagnetorum were correlated positively with temperature, whereas their vertical distribution was determined by moisture. Cernosvitoviella atrata was unable to avoid dry conditions which apparently caused severe mortality when exposed to the elevated temperatures; Achaeta eiseni was a more tolerant species, increasing in numbers with increasing temperature. Diptera larvae appeared to be dependent on the moisture status of the upper soil layers and their populations were reduced at higher temperatures and lower moisture contents. By contrast, tardigrades were able to survive adverse conditions by entering an anhydrobiotic stage, recovering when seasonal climate improved. General trends in soil faunal responses to climatological changes in the UK are predicted.

Effects of temperature elevation on the population dynamics of the upland heather psyllid Strophingia ericae (Curtis) (Homoptera: Psylloidea)

1 Cloches permeable to gas and water were used to simulate the effect of climate warming on upland populations of the heather psyllid Strophingia ericae at Moor House National Nature Reserve in the North Pennines, UK.2 The cloches produced an average warming of about 1 °C in the heather canopy over a period of one year.3 The density of S. ericae increased markedly in cloches within a few months of erection.4 Species composition and numbers of potential predators were similar inside cloches and in control plots.5 In the two year life‐cycle of S. ericae, the warming effect advanced the phenology from the second to third instar in the first winter, but in the second winter, fifth instar nymphs did not moult prematurely to adult.6 The density of S. ericae was higher on Calluna vulgaris at its boundary with Juncus squarrosus than in the pure C. vulgaris sward (in both cloched and control plots).

Role of Nitrogen in Herbage Production by Agrostis-Festuca Hill Grassland

The role of nitrogen (N) in limiting herbage production was assessed in an altitudinal sequence of Agrostis-Festuca grasslands in the Moor House National Nature Reserve. For most of the growing season the concentration of ammonium-N found in the soils at the times of sampling greatly exceeded that of nitrate-N. Laboratory determinations of soil N mineralization rates at field growing season temperatures showed that mineral N accumulated almost entirely as nitrate in samples from lower altitudes and as ammonium in soil samples taken at the highest altitude. A linear relationship between the mean annual concentration of N in the herbage and primary production in the four grassland sites suggests that soil N supply was a limiting factor (...)