bluuebunny/crossref_metadata_2025_split huggingface dataset:
The ecological implications of harvesting non‐timber forest products
Authors: Ticktin T. 
Published: February 2004

SummaryThe harvest of wild non‐timber forest products (NTFP) represents an important source of income to millions of people world‐wide. Despite growing concern over the conservation of these species, as well as their potential to foster forest conservation, information on the ecological implications of harvest is available only in disparate case studies.Seventy studies that quantify the ecological effects of harvesting NTFP from plant species were reviewed, with the aims of assessing the current state of knowledge and drawing lessons that can provide guidelines for management as well as better directing future ecological research in this area.The case studies illustrated that NTFP harvest can affect ecological processes at many levels, from individual and population to community and ecosystem. However, the majority of research was focused at a population level and on a limited subset of plant parts that are harvested.Tolerance to harvest varies according to life history and the part of plant that is harvested. Moreover, the effects of harvest for any one species are mediated by variation in environmental conditions over space and time, and by human management practices.In order to withstand heavy harvest, specific management practices in addition to gathering are necessary for many NTFP species. Management practices can be carried out at different spatial scales and some are highly effective in fostering population persistence.Synthesis and applications. Substantial advances have been made towards identifying the ecological impacts of NTFP harvest. However, there is a need for longer‐term studies that focus on multiple ecological levels (ranging from genes to ecosystems), that assess the mechanisms underlying impacts and that validate current models. Researchers and forest managers need to work with local harvesters in designing and evaluating management practices that can mitigate the negative effects of harvest.
Regulation of shrub dynamics by native browsing ungulates on East African rangeland
Authors: Augustine David J. , Mcnaughton Samuel J. 
Published: February 2004

Abstract

Herbivores, edaphic features and fire are primary factors regulating the balance between woody and herbaceous vegetation in savannas. Many observational studies have evaluated the potential effects of browsing herbivores on woody plant dynamics in African savannas, but few experimental studies have compared the dynamics of African savannas with and without browsers.
A replicated herbivore exclusion experiment was used to assess the role that native ungulates play in regulating woody plant dynamics on commercial rangeland in central Kenya, where the indigenous fauna have been allowed to coexist with cattle.
Exclusion of native browsing ungulates for just 3 years showed that they have dramatic effects at every scale from individual twig growth rates to overall rates of woody biomass accumulation in the ecosystem.
At the scale of individual Acacia twigs, browsers significantly reduced leaf density, leaf biomass and growth rates of twigs < 50 cm above‐ground (within the foraging height of dik‐diks Madoqua kirkii), but browsers had no effects on twig leaf density or leaf biomass at a height of 1·0–1·25 m above‐ground.
Reductions in the growth rate of twigs within the foraging height of dik‐diks was associated with a 6‐fold reduction in the rate at which shrubs < 0·5‐m tall were recruited into the 0·5–1·5 m height class. This reduced recruitment combined with measured rates of shrub mortality in larger height classes shows that browsers reduced the rate of increase in shrub density nearly to zero (7·1 ± 10·2 shrubs ha−1 year−1) compared to the rapid rate of increase in the absence of browsers (136·9 ± 13·6 shrubs ha−1 year−1).
Damage to shrub canopies by elephants Loxodonta africana caused large, significant reductions in cover of A. mellifera and Grewia tenax, but lesser reductions in cover of A. etbaica. For Acacias, elephant damage was focused on shrubs > 2·5 m tall, such that Acacias in intermediate height classes (0·5–2·5 m) experienced minimal browser impacts. Elephants influenced shrubland dynamics by altering shrub height‐class distributions, shifting species composition from broad‐leaved Grewia tenax to fine‐leaved Acacia species, and suppressing woody biomass accumulation; but elephants had little influence on changes in shrub density.
Synthesis and applications. Our results suggest that a community of native browsers that includes both small, selective species (e.g. dik‐diks) and large, bulk‐feeding species (elephants) can provide an important ecosystem service by suppressing shrub encroachment on commercial rangeland.
Disease transmission between and within species, and the implications for disease control
Authors: Caley Peter , Hone Jim 
Published: February 2004

SummaryDisease transmission can occur between and within species for diseases with multiple hosts. If these diseases are undesirable, for economic or health reasons, then the relative importance of each type of transmission should be determined. Bovine tuberculosis (Tb) caused byMycobacterium bovisis one such undesirable disease.In parts of New Zealand,M. bovisinfection is highly prevalent in feral ferretMustela furopopulations, and there is concern they may be acting as a reservoir of infection for domestic livestock, similar to the role played by brushtail possumsTrichosurus vulpecula. We undertook a manipulative large‐scale field experiment to test for and quantify interspecific transmission ofM. bovisfrom brushtail possums to feral ferrets, and intraspecific transmission ofM. boviswithin feral ferret populations.Age‐specific prevalence data obtained from cross‐sectional surveys was modelled to estimate the effect of experimental reductions in possum population density on the force ofM. bovisinfection in ferrets. A simple analysis estimated the force ofM. bovisinfection in ferrets to be reduced by 88% at sites previously subjected to a possum population density reduction. A more detailed analysis, incorporating ferret survey data from both before and after possum population density reduction and controlling for the effect of ferret sampling, estimated that possum population density reduction decreased the force ofM. bovisinfection in ferrets by 29% at sites of high ferret density, and 88% at sites of low ferret density, compared with experimental control sites.There is clearly substantial possum‐to‐ferret transmission ofM. bovis, and controlling possum populations is the logical first step to managingM. bovisinfection in ferret populations, especially at sites with low ferret density. Intra‐specific transmission is virtually absent in low density ferret populations though evident at higher densities.Synthesis and applications.These results have management implications for other multiple‐host diseases around the world, such as bovine tuberculosis and rabies. Control of within‐species transmission may not be as effective for disease control as a reduction in between‐species transmission. The management decision should be based on empirical estimates of the magnitude of each form of transmission.
The challenge of managing multiple species at multiple scales: reptiles in an Australian grazing landscape
Authors: Fischer Joern , Lindenmayer David B. , Cowling Ann 
Published: February 2004

Summary

Understanding the ecological effects of processes operating at multiple spatial scales on multiple species is a key challenge in ecology. It underpins both basic research and the increasing recognition of scale‐dependence in conservation biology.
Organisms are affected by ecological processes operating at multiple spatial scales. Hence the study of multiple species and spatial scales is a key challenge in ecology.
A spatially nested experimental design was used to investigate the habitat relationships of reptiles in a grazing landscape in southern New South Wales, Australia. Regression modelling was used to relate the presence of species and species richness to habitat variables.
Different species were predicted by different habitat variables, and some species reflected habitat structure at one, but not all, spatial scales. The four‐fingered skink Carlia tetradactyla was associated with box woodlands, areas with few rocks and many spiders, and areas with a northerly aspect and high tree cover. Boulenger's skink Morethia boulengeri was more likely to be found in areas with many ants and beetles, and also in areas with a northerly aspect and high tree cover. The striped skink Ctenotus robustus and olive legless lizard Delma inornata were significantly more likely to be detected in areas with a simple microhabitat structure. Species richness was highest in box woodlands (Eucalyptus albens and Eucalyptus melliodora) and at sites characterized by a high variability of habitat structure.
Different habitat variables varied over different spatial scales. For example, invertebrate abundance varied mostly over tens of metres, while grass/forb cover varied mostly over hundreds to thousands of metres.
Synthesis and applications. The multitude of species’ responses and spatial habitat variability highlighted the potential limitations of the fragmentation paradigm because it may oversimplify ecological complexity. On this basis, conservation in variegated grazing landscapes may need to consider changes to livestock management across entire landscapes, rather than concentrate solely on the preservation of particular patches.
Expansion of invasive species on ombrotrophic bogs: desiccation or high N deposition?
Authors: Tomassen Hilde B. M. , Smolders Alfons J. P. , Limpens Juul , Lamers Leon P. M. , Roelofs Jan G. M. 
Published: February 2004

SummaryIn many ombrotrophic bog areas the invasion of grass (e.g.Molinia caerulea) and tree (e.g.Betula pubescens) species has become a major problem. We investigated whether the invasion of such species is due to high atmospheric nitrogen (N) deposition by conducting a fertilization experiment.The effects of experimentally increased N input onMolinia,BetulaandEriophorum vaginatumwere studied in desiccated bog vegetation in Ireland, where there is relatively low background N deposition. Four different N treatments were applied for 3 years: 0 (control), 2, 4 and 8 g m−2 year−1.Ammonium and nitrate concentrations in the peat moisture increased at high N addition rates, leading to significantly higher carbon : nitrogen (C : N) and nitrogen : phosphorus (N : P) ratios in the top layer of the peat. The potential CO2production rate of the peat was not stimulated at high N addition rates due to severe acidification of the peat.Despite high tissue N : P ratios (above 40), above‐ground biomass production byMoliniawas stimulated at high N addition rates, and foliar nutrient concentrations were unaffected. In contrast toMolinia,BetulaandEriophorumwere unable to increase their above‐ground biomass, probably due to P limitation. Regrowth of the lichenCladonia portentosawas suppressed at high N addition rates.Synthesis and applications.We conclude that the invasion of bogs byMoliniaandBetulais likely to be less affected by desiccation than by increased N availability. Apparently,Moliniais well adapted to P‐limiting conditions, which may explain its success in regions with increased N deposition levels. The high availability of P in many Dutch bogs compared with Irish bogs, together with prolonged high N deposition levels, may explain the strong increase in bothMoliniaandBetulaobserved in the Netherlands. As long as N and P availabilities in Dutch bogs are too high to prevent invasion ofBetulaand/orMolinia, management measures stimulating growth ofSphagnummosses could probably reduce the negative effects of high N deposition levels.
Competitive control of invasive vegetation: a native wetland sedge suppresses Phalaris arundinacea in carbon‐enriched soil
Authors: Perry Laura G. , Galatowitsch Susan M. , Rosen Carl J. 
Published: February 2004

Summary

Invasive plants pose a major threat to native plant communities around the globe. Current methods of controlling invasive vegetation focus on eradication of existing populations, and are often effective only in the short term. Manipulating resource availability to give native species a competitive advantage over invasive species could reduce ecosystem vulnerability to invasion and might more effectively control invasive vegetation. We evaluated this approach for controlling invasions of sedge meadow communities by Phalaris arundinacea, a widespread invasive grass in North American wetlands.
To test whether lowering nitrogen (N) availability would allow a wetland sedge, Carex hystericina, to suppress Phalaris competitively, we examined Carex and Phalaris competition under a range of inorganic N concentrations (25–400 mg kg−1) in a glasshouse. We lowered N availability in wetland soil using carbon enrichment and repeated harvests of a cover crop, and then created a N gradient by applying NH4‐N to the N‐depleted soil.
In soil without carbon added, competition with Phalaris reduced Carex biomass by 91%, while competition with Carex did not influence Phalaris, as is commonly observed in sedge meadows. Phalaris biomass was five times Carex biomass in mixed stands. Conversely, in soil depleted of available N via carbon enrichment, competition with Carex reduced Phalaris biomass by 82%, while competition with Phalaris reduced Carex biomass by only 32%, indicating that Carex is the superior competitor for N. Carex biomass was six times Phalaris biomass in mixed stands in the carbon‐enriched soil.
Carbon enrichment lowered soil inorganic N by 10–30 mg kg−1. NH4‐N addition mitigated the negative effects of carbon on Phalaris growth and competitive ability, indicating that carbon enrichment altered competitive outcomes by lowering N availability. Greater Carex N uptake efficiency under N‐poor conditions appeared to account for the Carex competitive ability for N.
Synthesis and applications. Carex dominance in carbon‐enriched soil strongly suggests that lowering soil inorganic N to < 30 mg kg−1 in restored wetlands would allow establishing sedge meadow communities to suppress Phalaris invasions. Low‐N soils might be achieved via carbon enrichment, vegetation harvests and reduced N inputs. Reducing community vulnerability to invasion by manipulating resource availability appears to be a promising approach to invasive species management.
Assessing eutrophication and reference conditions for Scottish freshwater lochs using subfossil diatoms
Authors: Bennion Helen , Fluin Jennie , Simpson Gavin L. 
Published: February 2004

Summary

The European Council Water Framework Directive requires reference conditions to be determined for all water body types including lakes. We examined the role of palaeolimnology, specifically the diatom record, as a tool for assessing eutrophication and for defining lake reference conditions and ecological status.
Sediment cores (representing c. ad 1850 to present day) were taken from 26 Scottish freshwater loch basins. Radiometric dating techniques (210Pb and 137Cs) established a chronology for each core. Two levels of diatom analysis were employed: a relatively high resolution (15–20 samples) at 21 lochs considered of high interest, and a lower resolution (four to five samples) at the remaining sites.
Detrended correspondence analysis and dissimilarity measures were applied to the core top (present day) and bottom (reference state, c. ad 1850) samples to assess floristic change at each site. Significant floristic change, indicative of nutrient enrichment, occurred in 18 lochs along a broad trophic gradient.
Two‐way indicator species analysis (twinspan) was applied to the bottom (c. ad 1850) samples to classify the ‘reference’ diatom assemblages and thereby characterize the reference floras of the different lake types. twinspan identified four site end‐groups, each with a characteristic diatom assemblage, although there was some overlap in the taxa present in the four groups. Water depth and productivity were key factors that explained the groupings.
Diatom transfer functions that reconstructed total phosphorus (TP) concentrations were used to evaluate eutrophication. Nineteen lochs had increases in diatom‐inferred (DI) TP of > 5 µg l−1 (five of these > 20 µg l−1), six lochs had no change or negligible increases in DI‐TP (< 2 µg l−1), and there was evidence of a decline in DI‐TP in one loch over the period represented by the sediment cores. The inferred increases were significant at 12 lochs.
Synthesis and applications. Our data indicate that it may be difficult to find minimally impacted waters to act as reference sites, particularly for shallow, lowland lake types, in the current population. The derivation of site‐specific reference conditions from the sediment record is a particularly valuable approach in such cases. Ordination, clustering and dissimilarity measures applied to palaeodata, combined with transfer functions, offer powerful techniques for characterizing lake types, defining ecological and chemical reference conditions, and assessing deviation from the reference state.
Behavioural and environmental correlates of soaring‐bird mortality at on‐shore wind turbines
Authors: Barrios Luis , Rodríguez Alejandro 
Published: February 2004

Summary

Wind power plants represent a risk of bird mortality, but the effects are still poorly quantified. We measured bird mortality, analysed the factors that led birds to fly close to turbines, and proposed mitigation measures at two wind farms installed in the Straits of Gibraltar, one of the most important migration bottlenecks between Europe and Africa.
Bird corpses were surveyed along turbine lines and an associated power line to estimate mortality rates. The behaviour of birds observed within 250 m of turbines was also recorded as a putative indicator of risk. The effects of location, weather and flight behaviour on risk situations (passes within 5 m of turbines) were analysed using generalized linear modelling (GLM).
Mortality caused by turbines was higher than that caused by the power line. Losses involved mainly resident species, mostly griffon vultures Gyps fulvus (0·15 individuals turbine−1 year−1) and common kestrels Falco tinnunculus (0·19 individuals turbine−1 year−1). Mortalities were not associated with either structural attributes of wind farms or visibility.
Vulture collisions occurred in autumn–winter and were aggregated at two turbine lines where risks of collisions were greatest. The absence of thermals in winter forced vultures to use slopes for lift, the most likely mechanism influencing both their exposure to turbines and mortality.
Kestrel deaths occurred during the annual peak of abundance in summer. Carcasses were concentrated in the open habitats around a single wind farm and risk may have resulted from hunting habitat preferences.
Synthesis and applications. We conclude that bird vulnerability and mortality at wind power facilities reflect a combination of site‐specific (wind–relief interaction), species‐specific and seasonal factors. Despite the large number of migrating birds in the study area, most follow routes that are displaced from the facilities. Consequently, only a small fraction of birds on migratory flights was actually exposed to turbines. New wind installations must be preceded by detailed behavioural observation of soaring birds as well as careful mapping of migration routes.
Conservation and biological monitoring of tropical forests: the role of parataxonomists
Authors: Basset Yves , Novotny Vojtech , Miller Scott E. , Weiblen George D. , Missa Olivier , Stewart Alan J. A. 
Published: February 2004

SummaryThe demise of tropical rain forests will lead to a large‐scale extinction of genetic diversity, particularly of arthropods. Curtailing these trends might be facilitated by (i) reducing rates of habitat loss and degradation, (ii) enhancing systematics and (iii) increasing the flow of primary information on tropical biodiversity.We emphasize the need to examine alternative approaches that could generate a constant stream of data from tropical ecosystems. We argue that data collecting by parataxonomists (local assistants trained by professional biologists) represents one of the most efficient approaches to the study of tropical ecosystems available to date.Parataxonomists can provide high‐quality biological specimens and ecological information; statistical power will be high due to large sample sizes of data; database growth will be rapid and results will be published in a timely manner; and there will be collateral education of local people in conservation biology by the parataxonomists themselves.We stress that training local parataxonomists to inventory and monitor biodiversity is a promising and efficient strategy that deserves more attention in conservation biology. In particular, it may be one of the most feasible approaches for the biological monitoring of small and cryptic organisms in species‐rich environments, such as invertebrates in tropical rain forests.Synthesis and applications.Permanent botanical plots yield a wealth of data on the organization of tropical forests, and their numbers should be increased to monitor tropical biodiversity. Likewise, augmenting the number of local parataxonomist groups in various tropical countries and networking these contingents to monitor functionally diverse taxa may provide an efficient biological monitoring system in tropical forests.
Setting up tropical biodiversity for conservation through non‐damaging use: participation by parataxonomists
Authors: Janzen Daniel H. 
Published: February 2004

Summary

A parataxonomist is a resident, field‐based, biodiversity inventory specialist who is largely on‐the‐job trained out of the rural work force and makes a career of providing specimens and their natural history information to the taxasphere, and therefore to a multitude of users across society.
Any large inventory effort will benefit from a team of parataxonomists, not only through the large quantity of material and information they will gather and process, but through its among‐year and within‐season continuity.
Parataxonomists’ accuracy increases substantially with pride of workplace ownership, experience, and detail and continuity of iterative feedback from users of specimens and information.
Being drawn from the pool of rural workers into activities that are normally the privilege of university‐educated citizens, parataxonomists require continuous mentoring and encouragement to compensate for their potential social isolation from their former peer groups and the defensive disdain with which they may be treated by more elevated social classes.
Synthesis and applications. Parataxonomists are a key element in setting up wild biodiversity for non‐damaging sustainable development, not only through finding and making biodiversity available, but also by being employed locally by its development. The parataxonomist is to the neighbouring forest as both a literate person and a reference librarian are to a library.