bluuebunny/crossref_metadata_2025_split huggingface dataset:
A GIS‐supported model for the simulation of the spatial structure of wildland fire, Cass Basin, New Zealand
Authors: Perry George L.W. , Sparrow Ashley D. , Owens Ian F. 
Published: March 2003

Summary1. The behaviour of wildland fire in spatially heterogeneous landscapes was simulated using a model (PYROCART) that integrates the Rothermel fire spread model and a geographic information system (GIS).2. The principal aims of the research were to test the applicability of overseas fire behaviour models to New Zealand ecosystems, and to assess the applicability of GIS to fire spread prediction.3. The model was validated using an uncontrolled fire that occurred in the Cass Basin, South Island, New Zealand in May 1995. This fire burnt 580 ha across a complex vegetation mosaic comprising shrubland, stands ofNothofagus solandrivar.cliffortioides, bog and tussockland.4. The overall predictive accuracy of the model was estimated to be 80%. Prediction accuracies within different fuel types and slope angles are also presented. Fuel type and slope appeared to be the dominant influences on fire spread. No trends in prediction accuracy by wind speed or direction were apparent. The predicted burnt area and the real burnt area had a similar overall shape. It was found, however, that at high wind speeds the model tended to over‐predict rates of fire spread in some directions.5. The PYROCART model shows potential as a land management tool, especially for the testing of hypotheses concerning land management strategies. However, due to the complex input data and parameterization techniques it requires, it is less suitable forin situfire management.
Age‐ and sex‐specific behaviour in harbour sealsPhoca vitulinaleads to biased estimates of vital population parameters
Authors: Härkönen Tero , Hårding Karin C. , Lunneryd Sven Gunnar 
Published: March 2003

Summary1. Modelling of the population dynamics of seals require data on an array of vital parameters (fecundity, mortality, age structure, migrations, population growth rate). The most common way to obtain these data is to estimate the parameters from samples taken from the population. However, the influence from skewed samples can be substantial in populations with age‐ and sex‐specific features. By quantifying the behavioural differences among age and sex classes, data from skewed samples can be compensated retrospectively. Awareness of the existence and the potential magnitude of such biases is highly relevant for the design of surveys, sampling programmes and the implementation of management plans of age structured populations.2. The age‐ and sex‐specific behaviour of harbour sealsPhoca vitulinaand grey sealsHalichoerus grypuscan be studied by using freeze‐branded animals. Since the brand is permanent and visible up to a distance of 500 m, the harassment is limited to one occasion in the lifetime of the seal (the catching day).3. A method is also given for analysing data arising from re‐sighted branded animals, where re‐sightings of individual seals were transformed to estimates of relative haul‐out frequencies of seals by age and sex.4. The composition of harbour seal groups on land exhibit a conspicuous seasonal flux, and the fraction on land was not representative of the entire population at any time during the summer. The results have far‐reaching implications since most studies of seals are carried out at haul‐out sites, and differential behaviour between the sexes and among age classes is expected in all populations and species of seals. Skewed samples generate biases in estimates of population growth rate, age‐specific mortality and fecundity.5. Age‐specific haul‐out patterns must be taken into account when analysing data from populations with non‐stable age structures. As a consequence of changes in age structure after the 1988 seal epizootic, surveys under‐estimated the size of the Swedish–Danish harbour seal population by 6% in 1988 and over‐estimated the same parameter by up to 16% during the following years.6. The present paper establishes the complications of sampling natural populations that are structured by age and sex, and presents a method on how to quantify sampling errors.
Simulated effects of logging on carbon storage in dipterocarp forest
Authors: Pinard M.A. , Cropper W.P. 
Published: March 2003

Summary1. As the role of forestry‐based options for reducing or mitigating greenhouse gas emissions is debated by policymakers, there is a need to inform the debate by synthesizing existing information on carbon dynamics in tropical forest systems and by applying this information to a range of possible interventions in forestry.2. To investigate the consequences of reductions in logging damage for ecosystem carbon storage, we constructed a model to simulate changes in biomass and carbon pools following logging of primary dipterocarp forests in south‐east Asia. We adapted a physiologically driven tree‐based model of natural forest gap dynamics (FORMIX) to simulate forest recovery following logging.3. Following selective logging, simulated ecosystem carbon storage declined from prelogging levels (213 Mg C ha−1) to a low of 97 Mg C ha−1, 7 years after logging. Carbon storage in biomass approached prelogging levels about 120 years after logging.4. The relationship between fatal stand damage and ecosystem carbon storage was not linear, with biomass recovery following logging severely limited by 50–60% stand damage.5. Results from simulations suggest that when 20–50% of the stand is killed during logging, replacing persistent forest species with pioneer tree species can reduce the site's potential for carbon storage by 15–26% over 40–60 years.6. Reducing fatal damage from 40% to 20% of the residual stand, as was the case with a pilot project in Malaysia, was associated with an increase of 36 Mg C ha−1in mean carbon storage over 60 years.7. Efforts to monitor and verify the benefits, either through carbon sequestration in new growth or carbon retention in existing biomass, of offset projects involving tropical forests and natural forest management should focus on above‐ground biomass, particularly the large trees. Selection of the most appropriate allometric equations for a site and species is important because of their influence on biomass estimates.
Modelling water chemistry for a major Scottish river from catchment attributes
Authors: Cresser M.S. , Smart R. , Billett M.F. , Soulsby C. , Neal C. , Wade A. , Langan S. , Edwards A.C. 
Published: March 2003

1. The prediction of water quality is increasingly required in river catchment management, but methods are still developmental. We therefore derived empirical models to predict the concentrations of base cations, H+ and alkalinity at any point in a complex Scottish river system, and under diverse discharge conditions. Input data were readily available from geological and topographic maps, whole rock composition data and catchment land use inventories in geographical information systems (GIS). 2. A key and novel feature of the model was prediction using geological data for the riparian zone within 50 m of the river. The discharge contributions that passed through soil derived from each parent rock were estimated and used as weightings in predicting final run‐off quality. 3. Typical equations for upland catchments for mean, maximum or minimum river water Ca concentration, [Ca], were of the form [Ca] = a + b √{Carz}, where {Carz} denotes flow routing‐weighted rock CaO concentration of the riparian zone rock types present. These equations were significant at P < 0·0001. Similar approaches were applicable to alkalinity and to other base cations. 4. Predictions of [Ca] in catchments with mixed land use were improved by including model terms for catchment riparian zone cover of agriculturally improved (intensified) grassland and arable land. These results indicated anthropogenic effects on base cation flux that would not be represented by geological data alone. 5. Similarly, concentrations of Na, Mg and K were correlated with Cl concentration in the river water, primarily as a consequence of marine‐derived Cl. Including distance from the east coast as a predictive variable in place of [Cl] obviated the need for direct [Cl] measurement in model operation. 6. We advocate further work to assess whether similar models can be developed and applied in other geographical locations, where features such as land use, geology and sea salt inputs will all vary.
Large‐scale spatial variation in the breeding performance of song thrushesTurdus philomelosand blackbirdsT. merulain Britain
Authors: Paradis Emmanuel , Baillie Stephen R. , Sutherland William J. , Dudley Caroline , Crick Humphrey Q.P. , Gregory Richard D. 
Published: March 2003

1. Spatial variation in breeding performance is of critical importance in understanding the large‐scale distribution and abundance of living species, and in understanding species conservation. We studied the large‐scale spatial variation in reproductive output of two species of declining British bird, the song thrushTurdus philomelosand the blackbirdTurdus merula.2. We developed a method to predict spatial variation in reproductive output. Brood size and nest failure rates during the incubation and nestling periods were related to environmental factors using generalized linear models. Predicted values obtained from these models were combined to give values of number of fledglings produced per nesting attempt for 10‐km squares throughout Britain.3. We observed substantial spatial variation in reproductive output for both species; the component that varied most was nest failure rate during incubation. We were more successful in relating environmental factors to spatial variation in reproductive output for song thrush than for blackbird.4. Reproductive output in both species was affected mainly by factors that vary on a small spatial scale. Nest failure rate during incubation increased significantly where corvids were more abundant, suggesting a role for avian nest predators in determining spatial variation in reproductive output.5. Our approach can be extended readily to other species of birds, to other taxonomic groups and to finer spatial scales. Such models could be used to evaluate the implications of current and proposed wider countryside management for spatial variation in breeding performance. Evaluations based on breeding success as well as numbers are likely to be more robust than those based solely on abundance.
Aggregation and temporal stability of carabid beetle distributions in field and hedgerow habitats
Authors: C.F.G. Thomas , Parkinson L. , Griffiths G.J.K. , Garcia A. Fernandez , Marshall E.J.P. 
Published: March 2003

Summary Understanding the spatial dynamics of insect distributions in farmland can provide insights into their ecological requirements and potential for management. Identifying the scale, location and persistence of species’ aggregations is an important step towards understanding the factors driving population distributions. This study examined how different carabid species were distributed in field and field margin habitats, and analysed their spatiotemporal dynamics. We sampled 156 locations in a grid of pitfall traps over approximately 1 ha, comprising a hedgerow and adjacent parts of two arable fields. Traps were monitored between June and November 1994 to provide data with high spatial and temporal resolution of the two‐dimensional distributions of six carabid beetle taxa. The pattern of carabid activity‐density over the experimental site was displayed in a series of contour plots. Spatial analyses by distance indices (SADIE) were used to provide aggregation indices (Ia) for the distributions of carabid species at different times.A second SADIE index (Im) of spatial association between two sets of counts was used to measure the spatial stability of species’ aggregation patterns through time.Imwas also used to measure association or dissociation between the distributions of different species, and the spatial association between a species’ distribution and an environmental variable. Each taxon was aggregated most of the time, but different taxa aggregated in patches within the field and/or hedgerow to different and varying extents. The field boundaries were important for some species, either as the only habitat in which they occurred (Amaraspp.), as the major focus of more widespread distribution (Harpalus rufipes), or as a seasonal refuge (Nebria brevicollis). Within the crop habitat, different species also occupied different areas, providing some evidence to suggest species packing in space. Spatial distributions between consecutive samples were strongly and positively associated, indicating stability of patch location over short time‐scales. The strength of the association in turn was correlated with activity‐density. When time lags were introduced between sample distributions, some negative association indices indicated displacement of patches. In most cases, however, positive association was maintained over long periods, demonstrating patch stability. The spatial stability of patches suggests that future studies should focus on the detailed measurement of biotic and abiotic factors associated with patch location. Identifying the underlying causes of population distributions in farmland has important implications for managing habitat to enhance populations of beneficial predators, and targeting insecticide applications in precision agriculture to minimize their adverse side‐effects.
The effects of management on soil and plant carbon sequestration in slash pine plantations
Authors: Shan Jianping , Morris Lawrence A. , Hendrick Ronald L. 
Published: March 2003

SummaryIntensively managed pine plantations in the south‐eastern United States can play an important role in global carbon sequestration both through accumulation of carbon in wood used in long‐lasting products as well as through increased soil carbon storage. Fertilization and understorey‐elimination are two commonly used intensive management practices in the south‐eastern United States that have the potential to increase carbon storage in vegetation and affect soil carbon.In this study, we assessed the effects of these practices on carbon accumulation in vegetation biomass and in the soil of 17‐year‐old slash pinePinus elliottiiplantations in the flatwoods of northern Florida, USA.Three treatments, fertilization, understorey‐elimination, and fertilization plus understorey‐elimination, were evaluated and compared with an untreated control.All three treatments increased above‐ground biomass accumulation compared with the untreated control; understorey‐elimination also increased biomass of the forest floor litter, with or without fertilization.Although understorey‐elimination increased above‐ground production, as a result of reduced below‐ground production total net primary production was decreased in plots from which the understorey was eliminated.Soil carbon storage was lower in plots where the understorey was eliminated, with or without fertilization. This appeared to be the result of reduced fine root growth and mortality but also may have reflected reduced litterfall inputs early in the rotation.Our results indicate that intensive management of pine plantations on sandy flatwoods soils can increase carbon sequestration, but these increases will be the result of increased carbon accumulation in biomass and its long‐term uses rather than through increased soil carbon.
Estimating group size and population density of Eurasian badgers Meles meles by quantifying latrine use
Authors: Tuyttens F.A.M. , Long B. , Fawcett T. , Skinner A. , Brown J.A. , Cheeseman C.L. , Roddam A.W. , Macdonald D.W. 
Published: March 2003

Summary

Conservation issues and a potential role in disease transmission generate the continued need to census Eurasian badgers Meles meles, but direct counts and sett counts present difficulties. The feasibility of estimating social group size and population density of badgers by quantifying their use of latrines was evaluated.
The number of latrines, or preferably the number of separate dung pits, which were known from bait‐marking to be used by members of a social group, was positively correlated with adult group size estimated from mark–recapture studies at Woodchester Park and North Nibley (south‐west England). In the latter study area both latrine‐use measures were also significantly associated with total group size (i.e. including cubs and adults).
In spring 1997 and 1998, we quantified latrine use along strip transects, following linear features across four and five areas, respectively, in England, where badger density in summer was known from mark–recapture/resight studies.
Seven latrine‐use measures were evaluated with regard to their potential to predict badger density. Each measure separately explained between 62% and 91% of the variation in population density in a given year. The simplest measures (latrines km−1 and pits km−1) were most stable between years.
For these two simple latrine‐use measures, a linear model without an intercept term explained the highest proportion of variation in population density. A stepwise procedure to produce the best model selected only one (latrines km−1) of the two measures as an explanatory variable, indicating that pits km−1 is colinear with the former variable.
A badger census technique based on simple measurements of latrine use has great promise but needs to be validated across a wider range of badger populations, habitats, years, seasons and weather conditions.
Ecosystem recovery in restored headwater streams: the role of enhanced leaf retention
Authors: Muotka Timo , Laasonen Pekka 
Published: March 2003

Summary

There is controversy over how the success of ecological restoration should be measured. Traditionally, emphasis has been placed on species diversity and other community attributes, whereas the restoration of ecosystem processes has received less attention. Here, we combine replicated field experiments and a field survey to provide an ecosystem‐level measure of stream restoration success.
Numerous headwater streams in Finland, and in many other parts of the world, have been channelized for timber transport, resulting in channels with simplified structure and flow. Recently, programmes have been launched to restore these streams to their pre‐channelization condition. While the efficacy of restoration in improving fish habitat has been tested, little is known about effects on other stream biota or on the retention of leaf litter, despite its importance in trophic dynamics of forested headwater streams. Using a before‐after‐control‐intervention (BACI) designed experiment with multiple reference and experimental streams, we examined restoration‐induced changes in retention efficiency by conducting leaf‐release experiments before (1993) and after (1996) restoration.
Substrate heterogeneity increased, but moss cover decreased dramatically following restoration. Retention efficiency in restored streams was higher than in channelized, but lower than in natural, streams. Algae‐feeding scrapers were the only macroinvertebrate group whose density increased significantly after restoration.
Aquatic mosses were a key retentive feature in both channelized and natural streams, but their importance to retention was strikingly reduced by restoration. During restoration work, mosses are detached from large areas of the stream bed, exposing bare stone surfaces for colonization by periphytic algae.
A more effective restoration technique would involve the use of moss transplants, or the addition of large woody debris, to increase retentiveness and thus enhance the availability of organic material to benthic consumers. This case study on rivers illustrates how restoration projects benefit from an ecosystem perspective and from measures of ecosystem processes in assessing restoration success.
Peat bog restoration by floating raft formation: the effects of groundwater and peat quality
Authors: Smolders Alfons J. P. , Tomassen Hilde B. M. , Lamers Leon P. M. , Lomans Bart P. , Roelofs Jan G. M. 
Published: March 2003

Summary A prerequisite for the restoration of desiccated bog remnants is rewetting the peat surface. Frequently in Europe, extensive areas are flooded in order to maximize water retention, and growth of peat mosses is often observed in the shallow zones. In deeper waters, regeneration appears to depend on whether residual peat will become buoyant and form floating rafts. In order to study the initial stages of peat bog regeneration, conditions required for peat buoyancy were studied on peat monoliths collected from three cut‐over bog remnants in the Netherlands. The effects of different peat quality and water chemistry on buoyancy of the monoliths, as well as growth ofSphagnum cuspidatumand nutrient availability, were followed in a glasshouse experiment. Both groundwater and peat quality affected the buoyancy of the monoliths and the growth ofS. cuspidatum. When groundwater containing bicarbonate (1 mmol l−1HCO3−, pH 6·0) was applied, the pH of peat monoliths increased fromc. 3·5 toc. 4·5 due to acid buffering. As a result, two of the peat types became more buoyant and the concentration, production and emissions of methane (CH4) increased. It was concluded that the increase in CH4production, induced by the increased pH, was responsible for the buoyancy. When groundwater contained both HCO3−(1 mmol l−1) and sulphate (1 mmol l−1), pH was further increased to approximately pH 5·0 due to alkalinity generated by the SO42–reduction process. CH4production, however, decreased because of interference from the SO42–, as confirmed in additional incubation experiments. Phosphate concentrations, however, greatly increased in the HCO3−/SO42–addition treatment due to the interaction between sulphide and iron phosphate precipitates. In one of the peat types, treatments did not influence CH4production and buoyancy, most probably because of its low decomposability. The chemical characteristics of the peat, notably the concentrations of lignin and soluble phenolics as well as C:N, C:P and C:K ratios, were all higher than in the other two peat types. The increase ofS. cuspidatumbiomass during the experiment appeared to be strongly related to the N:P ratios of the capitula, which differed considerably among the three peat types. We conclude that when bog remnants are inundated the prospects for bog regeneration are largely determined by peat quality and water chemistry. Peat mats with low concentration of lignin and phenolics and low C:N ratios are most likely to become buoyant in water with a higher pH, so providing suitable environments forSphagnumspecies. When peat quality is inadequate, either shallow inundation or the addition of suitable peat from elsewhere is indicated.