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2.
Sci Rep ; 13(1): 15305, 2023 09 18.
Artigo em Inglês | MEDLINE | ID: mdl-37723314

RESUMO

We studied spatial patterns of kinship in the offspring of the endangered Lodoicea maldivica, a dioecious palm that produces the largest seed of any plant. Previous research has suggested that restricted seed and pollen dispersal in populations resulted in strong spatial genetic structure. We used microsatellites to genotype young plants and their potential parents at four sites across the species' entire natural range. We determined the most likely parents of each young plant based on the spatial separation of each parent pair, their genetic relatedness, and the level of correlated paternity. We identified both parents (43 female, 54 male) for 139 of 493 young plants. Mean distance between parental pairs was 26.8 m. Correlated paternity was low (0.168), indicating that mother trees were often pollinated by several fathers. Parental pairs were more closely related than expected by chance, suggesting outbreeding depression. Our results highlight the apparent strong mate choice for close kin in parent pairs of surviving offspring. We discuss the alternative biological processes that could lead to this, including the potential for break-up of favourable allelic combinations necessary for the development of the palm's very large seed. Management implications include germinating seeds where they naturally fall, using a diverse range of male plants as pollen donors for hand pollination, and protecting the native community of gecko pollinators.


Assuntos
Arecaceae , Sementes , Alelos , Genótipo , Mãos
3.
BJGP Open ; 7(4)2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37277172

RESUMO

BACKGROUND: Eliciting patients' ideas, concerns, expectations, and whether a problem has an 'effect' on their life (ICEE), is a widely recommended communication technique. However, it is not known how frequently ICEE components are raised in UK GP consultations. AIM: To assess the frequency of ICEE in routine GP consultations with adult patients and explore variables associated with ICEE. DESIGN & SETTING: An observational study was undertaken. It involved secondary analysis of a pre-existing archive of video-recorded, face-to-face GP consultations in the UK. METHOD: Observational coding of 92 consultations took place. Associations were assessed using binomial and ordered logistic regression. RESULTS: Most consultations included at least one ICEE component (90.2%). The most common ICEE component per consultation was patient ideas (79.3%), followed by concerns (55.4%), expectations (51.1%), and then effects on life (42.4%). For all ICEE components patients more commonly initiated the ICEE dialogue, and in only three consultations (3.3%) did GPs directly ask patients about their expectations. Problems that were acute (odds ratio [OR] 2.98, 95% confidence interval [CI] = 1.36 to 6.53, P = 0.007) or assessed by GPs aged ≥50 years (OR 2.10, 95% CI = 1.07 to 4.13, P = 0.030) were associated with more ICEE components. Problems assessed later in the consultation (OR 0.60 per problem order increase, 95% CI = 0.41 to 0.87, P = 0.007) by patients aged ≥75 years (OR 0.40, 95% CI = 0.16 to 0.98, P = 0.046) and from the most deprived cohort (OR 0.39, 95% CI = 0.17 to 0.92, P = 0.032) were associated with fewer ICEE components. Patient ideas were associated with more patients being 'very satisfied' post-consultation (OR 10.74, 95% CI = 1.60 to 72.0, P = 0.014) and the opposite was true of concerns (OR 0.14, 95% CI = 0.02 to 0.86, P = 0.034). CONCLUSION: ICEE components were associated with patient satisfaction and demographic variables. Further research is required to assess if the way ICEE are communicated affects these associations and other potential confounders.

5.
Br J Gen Pract ; 71(712): e869-e876, 2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34489251

RESUMO

BACKGROUND: Previous studies have reported how often safety-netting is documented in medical records, but it is not known how this compares with what is verbalised and what factors might influence the consistency of documentation. AIM: To compare spoken and documented safety-netting advice and to explore factors associated with documentation. DESIGN AND SETTING: A cross-sectional study, using an existing GP consultations archive. METHOD: Observational coding involving classifying and quantifying medical record entries and comparison with spoken safety-netting advice in 295 video-/audio-recorded consultations. Associations were tested using logistic regression. RESULTS: Two-thirds of consultations (192/295) contained spoken safety-netting advice that applied to less than half of the problems assessed (242/516). Only one-third of consultations (94/295) had documented safety-netting advice, which covered 20.3% of problems (105/516). The practice of GPs varied widely, from those that did not document their safety-netting advice to those that nearly always did so (86.7%). GPs were more likely to document their safety-netting advice for new problems (P = 0.030), when only a single problem was discussed in a consultation (P = 0.040), and when they gave specific rather than generic safety-netting advice (P = 0.007). In consultations where multiple problems were assessed (n = 139), the frequency of spoken and documented safety-netting advice decreased the later a problem was assessed. CONCLUSION: GPs frequently do not document the safety-netting advice they have given to patients, which may have medicolegal implications in the event of an untoward incident. GPs should consider how safely they can assess and document more than one problem in a single consultation and this risk should be shared with patients to help manage expectations.


Assuntos
Documentação , Encaminhamento e Consulta , Estudos Transversais , Humanos
6.
Br J Gen Pract ; 70(699): e723-e730, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32895240

RESUMO

BACKGROUND: Skin complaints are common in primary care, and poor outcomes in long-term conditions are often due to low adherence to treatment. Shared decision making and self-management support may help, yet there is little understanding of patient involvement or the support provided by GPs. AIM: To describe the content of primary care consultations for skin problems, including shared decision making practice, delivery of self-management advice, and follow-up. DESIGN AND SETTING: Cross-sectional study of video-recorded UK adult GP consultations and linked data. METHOD: A coding tool was developed and applied to all consultations with skin problems. Shared decision making was assessed using the observer OPTION5 scale. RESULTS: A total of 45/318 consultations (14.2%) related to one or more skin problems, which were discussed alongside other problems in 71.1% (32/45) of consultations. Of the 100 different problems discussed in these consultations, 51 were dermatological. The mean amount of time spent on skin problems in the consultations was 4 minutes 16 seconds. Medication was recommended for 66.7% (34/51) of skin problems, with low shared decision making (mean OPTION5 score = 10.7). Self-management advice (verbal only) was given for 47.1% (24/51) of skin problems. Most skin problems (84.3%; 43/51) were not referred to secondary care; 32.6% (14/43) of the skin problems not referred were seen again in primary care within 12 weeks, of which 35.7% (5/14) follow-up appointments were not planned. CONCLUSION: In this study, skin problems were usually presented alongside other complaints and resulted in a medication recommendation. Shared decision making was uncommon and self-management advice not consistently given, with re-attendance for the same problem common. GPs' training should reflect how frequently skin problems are seen and seek to improve patient involvement in decision making and support self-management.


Assuntos
Dermatologia , Adulto , Estudos Transversais , Tomada de Decisões , Humanos , Participação do Paciente , Encaminhamento e Consulta
7.
Sci Rep ; 10(1): 11365, 2020 07 09.
Artigo em Inglês | MEDLINE | ID: mdl-32647221

RESUMO

Worldwide, alien plant invasions have been intensively studied in the past decades, but mechanisms controlling the invasibility of native communities are not fully understood yet. The stochastic niche hypothesis predicts that species-rich plant communities are less prone to alien plant invasions than species-poor communities, which is supported by some but not all field studies, with some very species-rich communities such as the Brazilian Cerrado becoming heavily invaded. However, species-rich communities potentially contain a greater variety of facilitative interactions in resource exploitation than species-poor communities, from which invasive plants might benefit. This alternative hypothetical mechanism might explain why nutrient-poor, species-rich ecosystems are prone to invasion. Here we show that a high species richness both impedes and promotes invasive plants in the Brazilian Cerrado, using structural equation modelling and data from 38 field sites. We found support for the stochastic niche hypothesis through an observed direct negative influence of species richness on abundance of alien invasive species, but an indirect positive effect of species richness on invasive alien plants through soil phosphatase activity that enhances P availability was also found. These field observations were supported with results from a mesocosm experiment. Root phosphatase activity of plants increased with species richness in the mesocosms, which was associated with greater community P and N uptake. The most prominent alien grass species of the region, Melinis minutiflora, benefited most from the higher N and P availability in the species mixtures. Hence, this study provides a novel explanation of why species-richness may sometimes promote rather than impede invasion, and highlights the need to perform facilitation experiments in multi-species communities.


Assuntos
Espécies Introduzidas/estatística & dados numéricos , Dispersão Vegetal/fisiologia , Poaceae/fisiologia , Brasil , Monoéster Fosfórico Hidrolases/metabolismo , Proteínas de Plantas/metabolismo , Raízes de Plantas/metabolismo , Solo/química , Microbiologia do Solo , Processos Estocásticos
8.
PLoS One ; 15(4): e0231576, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32339175

RESUMO

Urban residents can benefit from spending time in outdoor spaces and engaging with nature-related activities. Such engagement can improve health and well-being, support community cohesion, and improve environmentally-friendly behaviours. However, engagement with nature may not be equal amongst different members of society. We investigated individual variation in engagement with nature in Singapore, a high-density city in tropical Southeast Asia. Through a survey of 1000 residents, we analysed relationships between demographic factors such as age, income, and sex, and the frequency of visitation to different ecosystem types, and the frequency of engagement with different nature-related activities. Parks and neighbourhood open spaces were among the most commonly-visited outdoor spaces, with nature reserves and other natural areas being visited less frequently. Common activities included sitting outdoors, art and photography, and running, while hiking and nature recreation were less frequent. In contrast with previous studies, we found relatively small differences among different groups of the population in their preferred types of outdoor activities. Older people, those with lower incomes, and without degrees were less likely to visit most types of outdoor space and engage with most types of nature-related activities. In the case of nature reserves, the distance from the visitor's home had a significantly negative influence on the frequency of visitation. These findings demonstrate that the benefits of engagement with nature are not equally enjoyed by all demographic groups, and that some groups lack engagement across the board. Strategies to increase nature engagement in tropical cities could include increasing the local availability and accessibility of different types of outdoor space, and education and public outreach programmes to encourage participation.


Assuntos
Meio Ambiente , Recreação , População Urbana/estatística & dados numéricos , Adulto , Fatores Etários , Idoso , Idoso de 80 Anos ou mais , Viés , Feminino , Humanos , Estilo de Vida , Masculino , Pessoa de Meia-Idade , Singapura , Fatores Socioeconômicos
9.
Landsc Urban Plan ; 200: 103837, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32341614

RESUMO

Urban ecosystem service (UES) is becoming an influential concept to guide the planning, design, and management of urban landscapes towards urban sustainability. However, its use is hindered by definitional ambiguity, and the conceptual bases underpinning its application remain weak. This is exemplified by two different but equally valid interpretations of UES: "urban ecosystem services", referring to ecosystem services from analogs of natural and semi-natural ecosystems within urban boundaries, and "urban ecosystem services", a much broader term that includes the former group as well as urban services in a city. While we recognize that a single definition of UES is not possible nor necessary as its application is context-dependent, it is nevertheless useful to clarify the relationships between these interpretations to promote consistent use, and importantly, explore how a broader interpretation of UES might advance its applications in areas that have been neglected. We developed a conceptual framework that links UES to natural and human-derived capital to explain the relationships between the dual meanings of UES and proposed three normative propositions to guide its application: (1) integrate holistically multiple components of natural capital to provide UES, (2) reduce dependence on non-renewable abiotic resources and human-derived capital, and (3) enhance UES through technology. The framework we developed helps to resolve the current ambiguity in the meanings of UES, highlights the need to recognise neglected aspects of natural capital important for UES, and can be used to clarify relationships with related concepts conveying dependence of human well-being on nature.

10.
AoB Plants ; 12(1): plz079, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31976055

RESUMO

Lodoicea maldivica (coco de mer) is a long-lived dioecious palm in which male and female plants are visually indistinguishable when immature, only becoming sexually dimorphic as adults, which in natural forest can take as much as 50 years. Most adult populations in the Seychelles exhibit biased sex ratios, but it is unknown whether this is due to different proportions of male and female plants being produced or to differential mortality. In this study, we developed sex-linked markers in Lodoicea using ddRAD sequencing, enabling us to reliably determine the gender of immature individuals. We screened 589 immature individuals to explore sex ratios across life stages in Lodoicea. The two sex-specific markers resulted in the amplification of male-specific bands (Lm123977 at 405 bp and Lm435135 at 130 bp). Our study of four sub-populations of Lodoicea on the islands of Praslin and Curieuse revealed that the two sexes were produced in approximately equal numbers, with no significant deviation from a 1:1 ratio before the adult stage. We conclude that sex in Lodoicea is genetically determined, suggesting that Lodoicea has a chromosomal sex determination system in which males are the heterogametic sex (XY) and females are homogametic (XX). We discuss the potential causes for observed biased sex ratios in adult populations, and the implications of our results for the life history, ecology and conservation management of Lodoicea.

11.
Br J Gen Pract ; 69(689): e869-e877, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31740456

RESUMO

BACKGROUND: Safety netting is recommended in a variety of clinical settings, yet there are no tools to record clinician safety-netting communication behaviours. AIM: To develop and assess the inter-rater reliability (IRR) of a coding tool designed to assess safety-netting communication behaviours in primary care consultations. DESIGN AND SETTING: A mixed-methods study using an existing dataset of video-and audio-recorded UK primary care consultations. METHOD: Key components that should be assessed in a coding tool were identified using the published literature and relevant guidelines. An iterative approach was utilised to continuously refine and generate new codes based on the application to real-life consultations. After the codebook had been generated, it was applied to 35 problems in 24 consultations independently by two coders. IRR scores were then calculated. RESULTS: The tool allows for the identification and quantification of the key elements of safety-netting advice including: who initiates the advice and at which stage of the consultation; the number of symptoms or conditions the patient is advised to look out for; what action patients should take and how urgently; as well as capturing how patients respond to such advice plus important contextual codes such as the communication of diagnostic uncertainty, the expected time course of an illness, and any follow-up plans. The final tool had substantial levels of IRR with the mean average agreement for the final tool being 88% (κ = 0.66). CONCLUSION: The authors have developed a novel tool that can reliably code the extent of clinician safety-netting communication behaviours.


Assuntos
Codificação Clínica , Comunicação em Saúde , Segurança do Paciente , Atenção Primária à Saúde , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Educação de Pacientes como Assunto , Encaminhamento e Consulta , Reino Unido , Gravação em Vídeo , Adulto Jovem
12.
Br J Gen Pract ; 69(689): e878-e886, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31740458

RESUMO

BACKGROUND: Safety-netting advice is information shared with a patient or their carer designed to help them identify the need to seek further medical help if their condition fails to improve, changes, or if they have concerns about their health. AIM: To assess when and how safety-netting advice is delivered in routine GP consultations. DESIGN AND SETTING: This was an observational study using 318 recorded GP consultations with adult patients in the UK. METHOD: A safety-netting coding tool was applied to all consultations. Logistic regression for the presence or absence of safety-netting advice was compared between patient, clinician, and problem variables. RESULTS: A total of 390 episodes of safety-netting advice were observed in 205/318 (64.5%) consultations for 257/555 (46.3%) problems. Most advice was initiated by the GP (94.9%) and delivered in the treatment planning (52.1%) or closing (31.5%) consultation phases. Specific advice was delivered in almost half (47.2%) of episodes. Safety-netting advice was more likely to be present for problems that were acute (odds ratio [OR] 2.18, 95% confidence interval [CI] = 1.30 to 3.64), assessed first in the consultation (OR 2.94, 95% CI = 1.85 to 4.68) or assessed by GPs aged ≤49 years (OR 2.56, 95% CI = 1.45 to 4.51). Safety-netting advice was documented for only 109/242 (45.0%) problems. CONCLUSION: GPs appear to commonly give safety-netting advice, but the contingencies or actions required on the patient's part may not always be specific or documented. The likelihood of safety-netting advice being delivered may vary according to characteristics of the problem or the GP. How to assess safety-netting outcomes in terms of patient benefits and harms does warrant further exploration.


Assuntos
Comunicação em Saúde , Segurança do Paciente , Atenção Primária à Saúde , Adulto , Idoso , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Reino Unido , Gravação em Vídeo , Adulto Jovem
14.
J Evol Biol ; 31(6): 784-800, 2018 06.
Artigo em Inglês | MEDLINE | ID: mdl-29518274

RESUMO

Studies of genetic adaptation in plant populations along elevation gradients in mountains have a long history, but there has until now been neither a synthesis of how frequently plant populations exhibit adaptation to elevation nor an evaluation of how consistent underlying trait differences across species are. We reviewed studies of adaptation along elevation gradients (i) from a meta-analysis of phenotypic differentiation of three traits (height, biomass and phenology) from plants growing in 70 common garden experiments; (ii) by testing elevation adaptation using three fitness proxies (survival, reproductive output and biomass) from 14 reciprocal transplant experiments; (iii) by qualitatively assessing information at the molecular level, from 10 genomewide surveys and candidate gene approaches. We found that plants originating from high elevations were generally shorter and produced less biomass, but phenology did not vary consistently. We found significant evidence for elevation adaptation in terms of survival and biomass, but not for reproductive output. Variation in phenotypic and fitness responses to elevation across species was not related to life history traits or to environmental conditions. Molecular studies, which have focussed mainly on loci related to plant physiology and phenology, also provide evidence for adaptation along elevation gradients. Together, these studies indicate that genetically based trait differentiation and adaptation to elevation are widespread in plants. We conclude that a better understanding of the mechanisms underlying adaptation, not only to elevation but also to environmental change, will require more studies combining the ecological and molecular approaches.


Assuntos
Adaptação Fisiológica/genética , Fenômenos Fisiológicos Vegetais/genética , Plantas/classificação , Altitude , Evolução Biológica
15.
Ecol Evol ; 7(19): 7765-7776, 2017 10.
Artigo em Inglês | MEDLINE | ID: mdl-29043032

RESUMO

Habitat degradation can reduce or even prevent the reproduction of previously abundant plant species. To develop appropriate management strategies, we need to understand the reasons for reduced recruitment in degraded ecosystems. The dioecious coco de mer palm (Lodoicea maldivica) produces by far the largest seeds of any plant. It is a keystone species in an ancient palm forest that occurs only on two small islands in the Seychelles, yet contemporary rates of seed production are low, especially in fragmented populations. We developed a method to infer the recent reproductive history of female trees from morphological evidence present on their inflorescences. We then applied this method to investigate the effects of habitat disturbance and soil nutrient conditions on flower and fruit production. The 57 female trees in our sample showed a 19.5-fold variation in flower production among individuals over a seven-year period. Only 77.2% of trees bore developing fruits (or had recently shed fruits), with the number per tree ranging from zero to 43. Flower production was positively correlated with concentrations of available soil nitrogen and potassium and did not differ significantly between closed and degraded habitat. Fruiting success was positively correlated with pollen availability, as measured by numbers and distance of neighboring male trees. Fruit set was lower in degraded habitat than in closed forest, while the proportion of abnormal fruits that failed to develop was higher in degraded habitat. Seed size recorded for a large sample of seeds collected by forest wardens varied widely, with fresh weights ranging from 1 to 18 kg. Synthesis: Shortages of both nutrients and pollen appear to limit seed production of Lodoicea in its natural habitat, with these factors affecting different stages of the reproductive process. Flower production varies widely amongst trees, while seed production is especially low in degraded habitat. The size of seeds is also very variable. We discuss the implications of these findings for managing this ecologically and economically important species.

16.
Integr Environ Assess Manag ; 13(5): 906-914, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28316137

RESUMO

Since the publication of the Organisation for Economic Co-operation and Development (OECD) avian acute oral guideline, OECD 223, empirical data have become available to compare the performance of OECD 223 with statistical simulations used to validate this guideline and with empirical data for US Environmental Protection Agency Office of Chemical Safety and Pollution Prevention (USEPA OCSPP) guideline OCSPP 850.2100. Empirical studies comprised 244 for Northern bobwhite, of which 73 were dose-response tests and 171 were limit tests. Of the dose-response tests, 26 were conducted to OECD 223 (using 3-4 stages) and 33 to OCSPP 850.2100 (using the single 50-bird design). Data were collected from 5 avian testing laboratories from studies performed between 2006 and 2013. The success with which the LD50 and slope could be determined was 100% and 96% for OECD 223 (mean 26 birds per test) and 100% and 51% for OCSPP 850.2100 (mean 50 birds per test). This was consistent with the statistical simulations. Control mortality across all species and designs amounted to 0.26% (n = 2655) with only single mortalities occurring in any 1 study and <1% for any 1 species. The simulations used to validate the OECD 223 design showed that control mortality up to 1% will have no observable impact on the performance. The distribution of time to death for Northern bobwhite, zebra finch, and canary were obtained from 90, 29, and 17 studies, and mortalities appeared within 3 d for 71%, 95%, and 91% of birds tested, respectively. Integr Environ Assess Manag 2017;13:906-914. © 2017 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).


Assuntos
Exposição Ambiental/análise , Poluentes Ambientais/toxicidade , Administração Oral , Animais , Aves , Relação Dose-Resposta a Droga , Guias como Assunto , Organização para a Cooperação e Desenvolvimento Econômico , Testes de Toxicidade
17.
BMJ ; 355: i6411, 2016 12 05.
Artigo em Inglês | MEDLINE | ID: mdl-27919933

Assuntos
Segurança , Humanos
18.
New Phytol ; 206(3): 990-999, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25616088

RESUMO

The iconic Lodoicea maldivica palm appears to invest heavily in reproduction, with females bearing the world's largest seeds and males producing copious pollen. We asked how these palms, which grow in extremely poor soils, obtain sufficient nutrients to support such high levels of reproductive function. Our study site was the Vallée de Mai UNESCO Site on Praslin, Seychelles. We measured the trees' allocations of dry matter, nitrogen (N) and phosphorus (P) to aboveground growth and reproduction, quantified stemflow and throughfall, and measured availabilities of N and P in the soil. We show that the nutrient costs of reproduction are very high in male and female plants, and for P far exceed those of vegetative growth. We describe how the palm leaves form a huge funnel that intercepts particulate material, especially pollen, which is flushed to the base of the trunk when it rains. In this way, Lodoicea improves its nutrient supply and that of its dispersal-limited offspring. Lodoicea shares many functional characteristics with dominant trees of other monodominant forests in the humid tropics. It also exhibits unique features, including its huge seed, effective funnelling mechanism and diverse community of closely associated animals, suggesting a long evolutionary history under relatively stable conditions.


Assuntos
Arecaceae/fisiologia , Sementes/fisiologia , Arecaceae/anatomia & histologia , Arecaceae/metabolismo , Biomassa , Herbivoria , Modelos Biológicos , Nitrogênio/metabolismo , Fósforo/metabolismo , Pólen/fisiologia , Reprodução , Sementes/anatomia & histologia , Sementes/metabolismo
19.
Ecol Evol ; 4(8): 1423-38, 2014 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-24834338

RESUMO

During the past century, the biomass of woody species has increased in many grassland and savanna ecosystems. As many of these species fix nitrogen symbiotically, they may alter not only soil nitrogen (N) conditions but also those of phosphorus (P). We studied the N-fixing shrub Dichrostachys cinerea in a mesic savanna in Zambia, quantifying its effects upon pools of soil N, P, and carbon (C), and availabilities of N and P. We also evaluated whether these effects induced feedbacks upon the growth of understory vegetation and encroaching shrubs. Dichrostachys cinerea shrubs increased total N and P pools, as well as resin-adsorbed N and soil extractable P in the top 10-cm soil. Shrubs and understory grasses differed in their foliar N and P concentrations along gradients of increasing encroachment, suggesting that they obtained these nutrients in different ways. Thus, grasses probably obtained them mainly from the surface upper soil layers, whereas the shrubs may acquire N through symbiotic fixation and probably obtain some of their P from deeper soil layers. The storage of soil C increased significantly under D. cinerea and was apparently not limited by shortages of either N or P. We conclude that the shrub D. cinerea does not create a negative feedback loop by inducing P-limiting conditions, probably because it can obtain P from deeper soil layers. Furthermore, C sequestration is not limited by a shortage of N, so that mesic savanna encroached by this species could represent a C sink for several decades. We studied the effects of woody encroachment on soil N, P, and C pools, and availabilities of N and P to Dichrostachys cinerea shrubs and to the understory vegetation. Both N and P pools in the soil increased along gradients of shrub age and cover, suggesting that N fixation by D. cinerea did not reduce the P supply. This in turn suggests that continued growth and carbon sequestration in this mesic savanna ecosystems are unlikely to be constrained by nutrient limitation and could represent a C sink for several decades.

20.
PLoS One ; 9(2): e89588, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-24586894

RESUMO

Plants are a major factor influencing methane emissions from wetlands, along with environmental parameters such as water table, temperature, pH, nutrients and soil carbon substrate. We conducted a field experiment to study how different plant species influence methane emissions from a wetland in Switzerland. The top 0.5 m of soil at this site had been removed five years earlier, leaving a substrate with very low methanogenic activity. We found a sixfold difference among plant species in their effect on methane emission rates: Molinia caerulea and Lysimachia vulgaris caused low emission rates, whereas Senecio paludosus, Carex flava, Juncus effusus and Typha latifolia caused relatively high rates. Centaurea jacea, Iris sibirica, and Carex davalliana caused intermediate rates. However, we found no effect of either plant biomass or plant functional groups--based on life form or productivity of the habitat--upon methane emission. Emissions were much lower than those usually reported in temperate wetlands, which we attribute to reduced concentrations of labile carbon following topsoil removal. Thus, unlike most wetland sites, methane production in this site was probably fuelled chiefly by root exudation from living plants and from root decay. We conclude that in most wetlands, where concentrations of labile carbon are much higher, these sources account for only a small proportion of the methane emitted. Our study confirms that plant species composition does influence methane emission from wetlands, and should be considered when developing measures to mitigate the greenhouse gas emissions.


Assuntos
Magnoliopsida/fisiologia , Metano/química , Solo/química , Áreas Alagadas , Biomassa , Ecossistema , Efeito Estufa
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