An environmental reconstruction based on palynological evidence preserved in peat was carried out... more An environmental reconstruction based on palynological evidence preserved in peat was carried out to examine late Holocene alpine tree line dynamics in the context of past climatic changes on Galdhøpiggen (Jotunheimen, southern Norway). We analysed a peat core taken from a mire at the present-day tree line (1000 m a.s.l.), c. 450 m downslope from the lower limit of sporadic permafrost. We adopted a combination of commonly used indicators of species' local presence to reconstruct past vegetation assemblages, such as the relative pollen abundance (%), pollen accumulation rate (PAR), and presence of indicator species. Additionally, fossil pollen from the peat sequence was compared to modern pollen from a surface moss polster in order to establish a modern analogue. The results were compared with studies covering the late-Holocene climatic changes in the area. The reconstruction demonstrates that a pine-dominated woodland reached above the present-day tree line at c. 4300 cal. yr BP, suggesting a warmer climate suitable for Scots pine (Pinus sylvestris) growth at this altitude. Scots pine retreated to lower altitudes between c. 3400-1700 cal. yr BP, accompanied by the descent of the low-alpine shrub-dominated belt, in response to cooling climatic conditions. The colder period covered c. 1700-170 cal. yr BP, and an open downy birch (Betula pubescens) woodland became widespread at 1000 m a.s.l., whilst pine remained sparse at this altitude. From c. 170 cal. yr BP onwards, warming allowed pine to re-establish its local presence alongside downy birch at 1000 m a.s.l.
Supplementary material from "Resilience: nitrogen limitation, mycorrhiza and long-term palaeoecological plant–nutrient dynamics
Ecosystem dynamics are driven by both biotic and abiotic processes, and perturbations can push ec... more Ecosystem dynamics are driven by both biotic and abiotic processes, and perturbations can push ecosystems into novel dynamical regimes. Plant–plant, plant–soil and mycorrhizal associations all affect plant ecosystem dynamics; however, the direction and magnitude of these effects vary by context and their contribution to ecosystem resilience over long time periods remains unknown. Here, using a mathematical framework, we investigate the effects of plant feedbacks and mycorrhiza on plant–nutrient interactions. We show evidence for strong nutrient controlled feedbacks, moderation by mycorrhiza and influence on ecological resilience. We use this model to investigate the resilience of a longitudinal palaeoecological birch–<i>δ</i><sup>15</sup>N interaction to plant–soil feedbacks and mycorrhizal associations. The birch–<i>δ</i><sup>15</sup>N system demonstrated high levels of resilience. Mycorrhiza were predicted to increase resilience by supporting plant–nitrogen uptake and immobilizing excess nitrogen; in contrast, long-term enrichment in available nitrogen by plant–soil feedbacks is expected to decrease ecological resilience.
It is well established in the world's fire-prone regions that wildfires can considerably change t... more It is well established in the world's fire-prone regions that wildfires can considerably change the hydrological dynamics of freshwater catchments. Limited research, however, has focused on the potential impacts of wildfire ash toxicity on aquatic biota. Here, we assess the chemical composition and toxicity of ash generated from wildfires in six contrasting vegetation types distributed globally (UK grassland, Spanish pine forest, Spanish heathland, USA chaparral, Australian eucalypt forest and Canadian spruce forest). Acute (48 h) immobilisation tests were conducted on the extensively studied aquatic macroinvertebrate Daphnia magna, a sensitive indicator of aquatic contaminants. We found significant differences between the chemical composition and toxicity of these ash types. The UK and Spanish ash had no detectable toxicity to Daphnia magna, whereas the Australian eucalypt, USA chaparral and Canadian spruce ash all caused significant toxicity (immobilisation). The principal characteristics of the latter ash types were their high pH, and NO 3 À , Cl À and conductivity levels. Elevated water-soluble and total concentrations of metals (e.g. Mn, Fe, Zn, Pb, Cu and As) and total polycyclic aromatic hydrocarbons (PAHs) were not linked to toxicity.
Favourable microclimates are predicted to buffer fragmented populations against the effects of en... more Favourable microclimates are predicted to buffer fragmented populations against the effects of environmental change, but ecological timeseries are often too short to establish the extent to which such microsites facilitate population persistence through multiple climate shifts. We investigate the effects of microclimatic heterogeneity on woodland resilience through millennial climate and disturbance shifts near northwest European woodland range limits. We use palaeoecological data from northern Scotland to study the effects of fragmentation on community composition and diversity in a potentially favourable microclimate, and compare palynological timeseries of tree abundance from five sites to assess the effects of favourable (low-lying sheltered) versus more marginal (higher altitude) settings on population persistence and stability. The sheltered site shows persistence of tree cover through Holocene climatic and anthropogenic shifts, including climaticallydriven regional woodland contraction around 4400 cal BP (calendar years before present), when surviving woods became compositionally differentiated into upland pine and low-lying deciduous communities. A favourable microclimate can thus buffer woodlands against environmental shifts and increase continuity of canopy cover, but it does not generate stable communities. Compositional reorganisation is an essential stress response mechanism and should be accommodated by conservation managers. The replacement of deciduous taxa by Pinus sylvestris after 1060 cal BP represents the decoupling of pine distribution from climate drivers by management intervention. As a result, current microrefugial woodland composition reflects late Holocene human intervention. Alternative models of community composition and behaviour from palaeoecology provide a stronger foundation for managing microsite communities than relict woods in contrasting environmental settings.
Tropical Montane Cloud Forests (TMCFs) form biodiverse communities that are characterized by freq... more Tropical Montane Cloud Forests (TMCFs) form biodiverse communities that are characterized by frequent occurrence of low-level clouds from which they capture a substantial proportion of their precipitation-here referred to as occult precipitation. TMCFs provide important ecosystem services, in particular the supply of water to their wider surroundings. Throughout the tropics (here 23.5 • S to 23.5 • N), they are under pressure from deforestation and poor land management which leads to loss of both forest area and species diversity, and reduces their capture of occult precipitation. Climate change may also reduce occult precipitation in TMCFs since the cloud base may lift in response to higher temperatures-the 'lifting cloud-base hypothesis'. These threats to TMCFs are well understood, but their quantitative
The influence of non-native pollen, both long-distance transported and from introduced taxa, on r... more The influence of non-native pollen, both long-distance transported and from introduced taxa, on reconstruction of past vegetation is not often well quantified in palynological investigations. We examined both fossil and modern samples from the Galápagos Islands, a remote archipelago lying 1000 km from the nearest continent. These islands are particularly well-suited for such an assessment, as (1) the native flora is limited and well-known, enabling increased taxonomic resolution within the palynological record, and (2) human impact in the Galápagos started after discovery by Europeans in 1535, allowing clear distinctions to be made between native and introduced taxa. Pollen samples were collected from five profiles in the Galápagos and grouped in (a) a pre-human-impact period, (b) an early human-impact period after c. 1535, and (c) a late human-impact period after c. 1973 when the introduced Cinchona pubescens tree started to expand. Introduced taxa accounted for approximately 10% of total pollen (excluding Cyperaceae) throughout the human-impact periods and long-distance transported pollen for approximately 5%. Twenty pollen taxa of introduced plants were found. Cinchona, which grows abundantly near the study sites, accounted for most of the introduced pollen, but an appreciable part also came from introduced plants growing in low numbers and at more distant locations within the archipelago. Total long-distance transported pollen (35 taxa) increased from 3% of total pollen in the pre-human-impact period to 5% in the human-impact periods, probably due to destruction of native vegetation through fire and thus reduction of local pollen production. These phenomena might lead to erroneous interpretation of local plant occurrence when the native/non-native or local/extralocal status of plants is not known.
Holocene fire in the Scottish Highlands: evidence from macroscopic charcoal records
The Holocene, Feb 1, 2006
It has been hypothesized that the mid-Holocene decline of pine (Pinus sylvestris L.) woodland in ... more It has been hypothesized that the mid-Holocene decline of pine (Pinus sylvestris L.) woodland in the Scottish Highlands may have been the result of a change in the fire regime of the region. Little is known about the Holocene fire history of these forests, although a number of factors suggest that fire may have played a significant role. This study examines whether fire was a prevalent factor in Scotland over the course of the Holocene and its relationship with Highland vegetation communities. Both macroscopic and microscopic charcoal are analysed in conjunction with a full palynological investigation from four Holocene lake sedimentary sequences in locations throughout the Scottish Highlands. Comparison of macroscopic charcoal abundance profiles with those from areas of known wildfire activity and the consistent pattern of burning revealed across the four disparate Highland sites indicate that broad-scale burning of vegetation did occur. Charcoal abundance was related to vegetation composition at all four of the sites examined. The abundance of pine, however, was found to be unrelated to fire history. Instead, fire appears to be predominantly linked to the development of heath and blanket mire communities. Analysis of three different macroscopic charcoal size fractions (? 500 gm, 250-500 gm and 125-250 gm) revealed strong correlations between measures. Microscopic charcoal abundance, however, was more variable and was determined to be a less accurate measure of local catchment-scale burning within the region.
Long‐term trajectories of non‐native vegetation on islands globally
Ecology Letters
Human‐mediated changes in island vegetation are, among others, largely caused by the introduction... more Human‐mediated changes in island vegetation are, among others, largely caused by the introduction and establishment of non‐native species. However, data on past changes in non‐native plant species abundance that predate historical documentation and censuses are scarce. Islands are among the few places where we can track human arrival in natural systems allowing us to reveal changes in vegetation dynamics with the arrival of non‐native species. We matched fossil pollen data with botanical status information (native, non‐native), and quantified the timing, trajectories and magnitude of non‐native plant vegetational change on 29 islands over the past 5000 years. We recorded a proportional increase in pollen of non‐native plant taxa within the last 1000 years. Individual island trajectories are context‐dependent and linked to island settlement histories. Our data show that non‐native plant introductions have a longer and more dynamic history than is generally recognized, with critical i...
An environmental reconstruction based on palynological evidence preserved in peat was carried out... more An environmental reconstruction based on palynological evidence preserved in peat was carried out to examine late-Holocene alpine tree line dynamics in the context of past climatic changes on Galdhøpiggen (Jotunheimen, southern Norway). We analysed a peat core taken from a mire at the present-day tree line (1000 m a.s.l.), c. 450 m downslope from the lower limit of sporadic permafrost. We adopted a combination of commonly used indicators of species’ local presence to reconstruct past vegetation assemblages, such as the relative pollen abundance (%), pollen accumulation rate (PAR), and presence of indicator species. Additionally, fossil pollen from the peat sequence was compared to modern pollen from a surface moss polster to establish a modern analogue. The results were compared with studies covering the late-Holocene climatic changes in the area. The reconstruction demonstrates that a pine-dominated woodland reached above the present-day tree line at c. 4300 cal. yr BP, suggesting ...
Whether Arctic and alpine ecosystems will act as a future net sink or source of carbon remains un... more Whether Arctic and alpine ecosystems will act as a future net sink or source of carbon remains uncertain. The present study investigates ways in which ecosystem (soil and vegetation) and geomorphological (cryogenic disturbance) factors may control or affect the future release of carbon in an alpine permafrost landscape. Rates of ecosystem respiration (Re) were examined using a portable gas analyzer across an altitudinal transect ranging from mid‐ to high‐alpine vegetation zones underlain by discontinuous to continuous permafrost on Galdhøpiggen (Norway). Measurements were made of Re during the peak growing season on active and relict sorted circles exhibiting varying levels of frost disturbance and shrub encroachment. Re was found to be controlled more strongly by soil microclimate and plant growth forms than by geomorphic indicators of cryoturbation in thawing permafrost or by atmospheric conditions. The results indicate that increasing shrub cover leads to elevated Re, while an in...
Prescribed fire is a controversial and highly debated topic in UK land management. • Water supply... more Prescribed fire is a controversial and highly debated topic in UK land management. • Water supply catchments are at risk from water quality impacts of fire. • Irresponsible burning in the UK uplands threatens to reduce vital carbon storage. • Prescribed burning over inappropriate timescales reduces faunal and floral diversity. • More research is needed to reliably inform management practices in the UK.
Holocene fire in the Scottish Highlands: evidence from macroscopic charcoal records
The Holocene, 2006
It has been hypothesized that the mid-Holocene decline of pine (Pinus sylvestris L.) woodland in ... more It has been hypothesized that the mid-Holocene decline of pine (Pinus sylvestris L.) woodland in the Scottish Highlands may have been the result of a change in the fire regime of the region. Little is known about the Holocene fire history of these forests, although a number of factors suggest that fire may have played a significant role. This study examines whether fire was a prevalent factor in Scotland over the course of the Holocene and its relationship with Highland vegetation communities. Both macroscopic and microscopic charcoal are analysed in conjunction with a full palynological investigation from four Holocene lake sedimentary sequences in locations throughout the Scottish Highlands. Comparison of macroscopic charcoal abundance profiles with those from areas of known wildfire activity and the consistent pattern of burning revealed across the four disparate Highland sites indicate that broad-scale burning of vegetation did occur. Charcoal abundance was related to vegetation...
LETTER The ecological consequences of megafaunal loss: giant tortoises and wetland biodiversity
The giant tortoises of the Galapagos have become greatly depleted since European discovery of the... more The giant tortoises of the Galapagos have become greatly depleted since European discovery of the islands in the 16th Century, with populations declining from an estimated 250 000 to between 8000 and 14 000 in the 1970s. Successful tortoise conservation efforts have focused on species recovery, but ecosystem conservation and restoration requires a better understanding of the wider ecological consequences of this drastic reduction in the archipelago’s only large native herbivore. We report the first evidence from palaeoecological records of coprophilous fungal spores of the formerly more extensive geographical range of giant tortoises in the highlands of Santa Cruz Island. Upland tortoise populations on Santa Cruz declined 500–700 years ago, likely the result of human impact or possible climatic change. Former freshwater wetlands, a now limited habitat-type, were found to have converted to Sphagnum bogs concomitant with tortoise loss, subse-quently leading to the decline of several n...
An environmental reconstruction based on palynological evidence preserved in peat was carried out... more An environmental reconstruction based on palynological evidence preserved in peat was carried out to examine late Holocene alpine tree line dynamics in the context of past climatic changes on Galdhøpiggen (Jotunheimen, southern Norway). We analysed a peat core taken from a mire at the present-day tree line (1000 m a.s.l.), c. 450 m downslope from the lower limit of sporadic permafrost. We adopted a combination of commonly used indicators of species' local presence to reconstruct past vegetation assemblages, such as the relative pollen abundance (%), pollen accumulation rate (PAR), and presence of indicator species. Additionally, fossil pollen from the peat sequence was compared to modern pollen from a surface moss polster in order to establish a modern analogue. The results were compared with studies covering the late-Holocene climatic changes in the area. The reconstruction demonstrates that a pine-dominated woodland reached above the present-day tree line at c. 4300 cal. yr BP, suggesting a warmer climate suitable for Scots pine (Pinus sylvestris) growth at this altitude. Scots pine retreated to lower altitudes between c. 3400-1700 cal. yr BP, accompanied by the descent of the low-alpine shrub-dominated belt, in response to cooling climatic conditions. The colder period covered c. 1700-170 cal. yr BP, and an open downy birch (Betula pubescens) woodland became widespread at 1000 m a.s.l., whilst pine remained sparse at this altitude. From c. 170 cal. yr BP onwards, warming allowed pine to re-establish its local presence alongside downy birch at 1000 m a.s.l.
Supplementary material from "Resilience: nitrogen limitation, mycorrhiza and long-term palaeoecological plant–nutrient dynamics
Ecosystem dynamics are driven by both biotic and abiotic processes, and perturbations can push ec... more Ecosystem dynamics are driven by both biotic and abiotic processes, and perturbations can push ecosystems into novel dynamical regimes. Plant–plant, plant–soil and mycorrhizal associations all affect plant ecosystem dynamics; however, the direction and magnitude of these effects vary by context and their contribution to ecosystem resilience over long time periods remains unknown. Here, using a mathematical framework, we investigate the effects of plant feedbacks and mycorrhiza on plant–nutrient interactions. We show evidence for strong nutrient controlled feedbacks, moderation by mycorrhiza and influence on ecological resilience. We use this model to investigate the resilience of a longitudinal palaeoecological birch–<i>δ</i><sup>15</sup>N interaction to plant–soil feedbacks and mycorrhizal associations. The birch–<i>δ</i><sup>15</sup>N system demonstrated high levels of resilience. Mycorrhiza were predicted to increase resilience by supporting plant–nitrogen uptake and immobilizing excess nitrogen; in contrast, long-term enrichment in available nitrogen by plant–soil feedbacks is expected to decrease ecological resilience.
It is well established in the world's fire-prone regions that wildfires can considerably change t... more It is well established in the world's fire-prone regions that wildfires can considerably change the hydrological dynamics of freshwater catchments. Limited research, however, has focused on the potential impacts of wildfire ash toxicity on aquatic biota. Here, we assess the chemical composition and toxicity of ash generated from wildfires in six contrasting vegetation types distributed globally (UK grassland, Spanish pine forest, Spanish heathland, USA chaparral, Australian eucalypt forest and Canadian spruce forest). Acute (48 h) immobilisation tests were conducted on the extensively studied aquatic macroinvertebrate Daphnia magna, a sensitive indicator of aquatic contaminants. We found significant differences between the chemical composition and toxicity of these ash types. The UK and Spanish ash had no detectable toxicity to Daphnia magna, whereas the Australian eucalypt, USA chaparral and Canadian spruce ash all caused significant toxicity (immobilisation). The principal characteristics of the latter ash types were their high pH, and NO 3 À , Cl À and conductivity levels. Elevated water-soluble and total concentrations of metals (e.g. Mn, Fe, Zn, Pb, Cu and As) and total polycyclic aromatic hydrocarbons (PAHs) were not linked to toxicity.
Favourable microclimates are predicted to buffer fragmented populations against the effects of en... more Favourable microclimates are predicted to buffer fragmented populations against the effects of environmental change, but ecological timeseries are often too short to establish the extent to which such microsites facilitate population persistence through multiple climate shifts. We investigate the effects of microclimatic heterogeneity on woodland resilience through millennial climate and disturbance shifts near northwest European woodland range limits. We use palaeoecological data from northern Scotland to study the effects of fragmentation on community composition and diversity in a potentially favourable microclimate, and compare palynological timeseries of tree abundance from five sites to assess the effects of favourable (low-lying sheltered) versus more marginal (higher altitude) settings on population persistence and stability. The sheltered site shows persistence of tree cover through Holocene climatic and anthropogenic shifts, including climaticallydriven regional woodland contraction around 4400 cal BP (calendar years before present), when surviving woods became compositionally differentiated into upland pine and low-lying deciduous communities. A favourable microclimate can thus buffer woodlands against environmental shifts and increase continuity of canopy cover, but it does not generate stable communities. Compositional reorganisation is an essential stress response mechanism and should be accommodated by conservation managers. The replacement of deciduous taxa by Pinus sylvestris after 1060 cal BP represents the decoupling of pine distribution from climate drivers by management intervention. As a result, current microrefugial woodland composition reflects late Holocene human intervention. Alternative models of community composition and behaviour from palaeoecology provide a stronger foundation for managing microsite communities than relict woods in contrasting environmental settings.
Tropical Montane Cloud Forests (TMCFs) form biodiverse communities that are characterized by freq... more Tropical Montane Cloud Forests (TMCFs) form biodiverse communities that are characterized by frequent occurrence of low-level clouds from which they capture a substantial proportion of their precipitation-here referred to as occult precipitation. TMCFs provide important ecosystem services, in particular the supply of water to their wider surroundings. Throughout the tropics (here 23.5 • S to 23.5 • N), they are under pressure from deforestation and poor land management which leads to loss of both forest area and species diversity, and reduces their capture of occult precipitation. Climate change may also reduce occult precipitation in TMCFs since the cloud base may lift in response to higher temperatures-the 'lifting cloud-base hypothesis'. These threats to TMCFs are well understood, but their quantitative
The influence of non-native pollen, both long-distance transported and from introduced taxa, on r... more The influence of non-native pollen, both long-distance transported and from introduced taxa, on reconstruction of past vegetation is not often well quantified in palynological investigations. We examined both fossil and modern samples from the Galápagos Islands, a remote archipelago lying 1000 km from the nearest continent. These islands are particularly well-suited for such an assessment, as (1) the native flora is limited and well-known, enabling increased taxonomic resolution within the palynological record, and (2) human impact in the Galápagos started after discovery by Europeans in 1535, allowing clear distinctions to be made between native and introduced taxa. Pollen samples were collected from five profiles in the Galápagos and grouped in (a) a pre-human-impact period, (b) an early human-impact period after c. 1535, and (c) a late human-impact period after c. 1973 when the introduced Cinchona pubescens tree started to expand. Introduced taxa accounted for approximately 10% of total pollen (excluding Cyperaceae) throughout the human-impact periods and long-distance transported pollen for approximately 5%. Twenty pollen taxa of introduced plants were found. Cinchona, which grows abundantly near the study sites, accounted for most of the introduced pollen, but an appreciable part also came from introduced plants growing in low numbers and at more distant locations within the archipelago. Total long-distance transported pollen (35 taxa) increased from 3% of total pollen in the pre-human-impact period to 5% in the human-impact periods, probably due to destruction of native vegetation through fire and thus reduction of local pollen production. These phenomena might lead to erroneous interpretation of local plant occurrence when the native/non-native or local/extralocal status of plants is not known.
Holocene fire in the Scottish Highlands: evidence from macroscopic charcoal records
The Holocene, Feb 1, 2006
It has been hypothesized that the mid-Holocene decline of pine (Pinus sylvestris L.) woodland in ... more It has been hypothesized that the mid-Holocene decline of pine (Pinus sylvestris L.) woodland in the Scottish Highlands may have been the result of a change in the fire regime of the region. Little is known about the Holocene fire history of these forests, although a number of factors suggest that fire may have played a significant role. This study examines whether fire was a prevalent factor in Scotland over the course of the Holocene and its relationship with Highland vegetation communities. Both macroscopic and microscopic charcoal are analysed in conjunction with a full palynological investigation from four Holocene lake sedimentary sequences in locations throughout the Scottish Highlands. Comparison of macroscopic charcoal abundance profiles with those from areas of known wildfire activity and the consistent pattern of burning revealed across the four disparate Highland sites indicate that broad-scale burning of vegetation did occur. Charcoal abundance was related to vegetation composition at all four of the sites examined. The abundance of pine, however, was found to be unrelated to fire history. Instead, fire appears to be predominantly linked to the development of heath and blanket mire communities. Analysis of three different macroscopic charcoal size fractions (? 500 gm, 250-500 gm and 125-250 gm) revealed strong correlations between measures. Microscopic charcoal abundance, however, was more variable and was determined to be a less accurate measure of local catchment-scale burning within the region.
Long‐term trajectories of non‐native vegetation on islands globally
Ecology Letters
Human‐mediated changes in island vegetation are, among others, largely caused by the introduction... more Human‐mediated changes in island vegetation are, among others, largely caused by the introduction and establishment of non‐native species. However, data on past changes in non‐native plant species abundance that predate historical documentation and censuses are scarce. Islands are among the few places where we can track human arrival in natural systems allowing us to reveal changes in vegetation dynamics with the arrival of non‐native species. We matched fossil pollen data with botanical status information (native, non‐native), and quantified the timing, trajectories and magnitude of non‐native plant vegetational change on 29 islands over the past 5000 years. We recorded a proportional increase in pollen of non‐native plant taxa within the last 1000 years. Individual island trajectories are context‐dependent and linked to island settlement histories. Our data show that non‐native plant introductions have a longer and more dynamic history than is generally recognized, with critical i...
An environmental reconstruction based on palynological evidence preserved in peat was carried out... more An environmental reconstruction based on palynological evidence preserved in peat was carried out to examine late-Holocene alpine tree line dynamics in the context of past climatic changes on Galdhøpiggen (Jotunheimen, southern Norway). We analysed a peat core taken from a mire at the present-day tree line (1000 m a.s.l.), c. 450 m downslope from the lower limit of sporadic permafrost. We adopted a combination of commonly used indicators of species’ local presence to reconstruct past vegetation assemblages, such as the relative pollen abundance (%), pollen accumulation rate (PAR), and presence of indicator species. Additionally, fossil pollen from the peat sequence was compared to modern pollen from a surface moss polster to establish a modern analogue. The results were compared with studies covering the late-Holocene climatic changes in the area. The reconstruction demonstrates that a pine-dominated woodland reached above the present-day tree line at c. 4300 cal. yr BP, suggesting ...
Whether Arctic and alpine ecosystems will act as a future net sink or source of carbon remains un... more Whether Arctic and alpine ecosystems will act as a future net sink or source of carbon remains uncertain. The present study investigates ways in which ecosystem (soil and vegetation) and geomorphological (cryogenic disturbance) factors may control or affect the future release of carbon in an alpine permafrost landscape. Rates of ecosystem respiration (Re) were examined using a portable gas analyzer across an altitudinal transect ranging from mid‐ to high‐alpine vegetation zones underlain by discontinuous to continuous permafrost on Galdhøpiggen (Norway). Measurements were made of Re during the peak growing season on active and relict sorted circles exhibiting varying levels of frost disturbance and shrub encroachment. Re was found to be controlled more strongly by soil microclimate and plant growth forms than by geomorphic indicators of cryoturbation in thawing permafrost or by atmospheric conditions. The results indicate that increasing shrub cover leads to elevated Re, while an in...
Prescribed fire is a controversial and highly debated topic in UK land management. • Water supply... more Prescribed fire is a controversial and highly debated topic in UK land management. • Water supply catchments are at risk from water quality impacts of fire. • Irresponsible burning in the UK uplands threatens to reduce vital carbon storage. • Prescribed burning over inappropriate timescales reduces faunal and floral diversity. • More research is needed to reliably inform management practices in the UK.
Holocene fire in the Scottish Highlands: evidence from macroscopic charcoal records
The Holocene, 2006
It has been hypothesized that the mid-Holocene decline of pine (Pinus sylvestris L.) woodland in ... more It has been hypothesized that the mid-Holocene decline of pine (Pinus sylvestris L.) woodland in the Scottish Highlands may have been the result of a change in the fire regime of the region. Little is known about the Holocene fire history of these forests, although a number of factors suggest that fire may have played a significant role. This study examines whether fire was a prevalent factor in Scotland over the course of the Holocene and its relationship with Highland vegetation communities. Both macroscopic and microscopic charcoal are analysed in conjunction with a full palynological investigation from four Holocene lake sedimentary sequences in locations throughout the Scottish Highlands. Comparison of macroscopic charcoal abundance profiles with those from areas of known wildfire activity and the consistent pattern of burning revealed across the four disparate Highland sites indicate that broad-scale burning of vegetation did occur. Charcoal abundance was related to vegetation...
LETTER The ecological consequences of megafaunal loss: giant tortoises and wetland biodiversity
The giant tortoises of the Galapagos have become greatly depleted since European discovery of the... more The giant tortoises of the Galapagos have become greatly depleted since European discovery of the islands in the 16th Century, with populations declining from an estimated 250 000 to between 8000 and 14 000 in the 1970s. Successful tortoise conservation efforts have focused on species recovery, but ecosystem conservation and restoration requires a better understanding of the wider ecological consequences of this drastic reduction in the archipelago’s only large native herbivore. We report the first evidence from palaeoecological records of coprophilous fungal spores of the formerly more extensive geographical range of giant tortoises in the highlands of Santa Cruz Island. Upland tortoise populations on Santa Cruz declined 500–700 years ago, likely the result of human impact or possible climatic change. Former freshwater wetlands, a now limited habitat-type, were found to have converted to Sphagnum bogs concomitant with tortoise loss, subse-quently leading to the decline of several n...
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