1,720,984 research outputs found
Factors influencing conservation of trees on farmland and silvicultural management activities in a Sudanian agro-ecosystem, West Africa
No full textThe loss of tree resources and low productivity of soil are the main environmental problems
affecting the livelihoods in developing countries. This paper reports a study of factors
influencing farmers’ decision to protect and manage trees on their farmland that aims to restore
degraded land and improve biodiversity. The data were collected from personal interviews
conducted with farmers in the Center-West region of Burkina Faso and were analyzed using
Principal Component Analysis, multiple linear regression and binary logistic regression. The
results showed that farmer’s decision to participate in conservation of trees on farmland was
mainly influenced by silvicultural knowledge and skills, participation in farmers' groups or other
social organizations with interest in tree conservation, the social value of biodiversity in the
rural, and the perceived economic benefits of trees on farm. These factors need to be taken into
consideration to enhance farmers' participation in agroforestry and to achieve tree cover
restoration. Regression analysis showed that important variables for explaining variation in
levels of motivation in tree conservation on farms include household wealth, gender, ethnic
group, age, education level, marital status, religion, residence status, farm size, household size
and technical support. These results indicate that organizations promoting agroforestry among
poorer smallholders will have more success if they consider the diversity of smallholder socioeconomic
and perceptional characteristics. The findings from this study will help in the
restoration of degraded rural landscapes, the conservation of biodiversity and improve resilience
in farmland and natural land formations
Comparison of aboveground vegetation and soil seed bank composition at sites of different grazing intensity around a savanna-woodland watering point in West Africa
No full textGrazing removes a plant’s aboveground vegetative and reproductive tissues and can modify the soil seed bank, potentially impacting the restoration of preferred species. Knowledge about aboveground vegetation and species composition of soil seed bank and the processes that contribute to vegetation recovery on and surrounding watering points subjected to grazing is lacking. Successful restoration strategies hinge on addressing these knowledge gaps. We assessed the effects of livestock grazing on aboveground vegetation and soil seed bank characteristics along a river bank and surrounding areas subject to different grazing intensities and draw implications for restoration. Plots (50 × 50 m) were established along five transects representing differing levels of grazing intensity. Soil samples were taken from three layers within each plot to determine soil properties and species composition of soil seed bank using the seedling emergence method. Heavy grazing resulted in the disappearance of perennial grasses, a reduction in species diversity and a decrease in soil nutrients with increased soil depth. Overall, the similarity between the extant aboveground vegetation and flora within the soil seed bank was low. The soil seed bank was dominated by herbaceous species and two woody species, suggesting that many woody species are not accumulating in the soil. With increasing soil depth, the seed density and richness declined. Canonical correspondence analyses (CCAs) showed that emerged seedlings from the soil seed bank were significantly influenced by soil carbon, organic matter, total nitrogen, total potassium and soil cation exchange capacity. This finding suggests that current grazing practices have a negative impact on the vegetation surrounding watering points; hence there is a need for improved grazing management strategies and vegetation restoration in these areas. The soil seed bank alone cannot restore degraded river banks; active transfer of propagules from adjacent undisturbed forest areas is essential
Contrasting land use systems influence soil seed bank composition and density in a rural landscape mosaic in West Africa
No full textSoil seed banks (SSBs) play a key role in the post-disturbance recruitment of many plant species. Seed bank diversity can be influenced by spatial and environmental variability and disturbance heterogeneity across the landscape. Understanding the recovery potential of native vegetation from SSBs is important for restoration and biodiversity conservation. Yet, in savanna-woodland, little is known about how SSBs vary in their germination, composition and density under different land uses, and how SSBs relate to aboveground vegetation (AGV). Using a sampling design based on the Land Degradation Surveillance Framework, we assessed the SSB and AGV in twelve 0.25 ha plots among sixteen in four contrasting land use systems of savanna-woodland in Burkina Faso: bushland, cultivated farmland, fallow and wetland. A total of 720 soil samples were taken from four stratified depths of 0–5 cm, >5–10 cm, >10–15 cm, and >15–20 cm. The SSB composition and richness was determined by the seedling emergence technique. Results showed that the SSB in all land uses was largely dominated by annual grasses with few perennial herbaceous and woody species. Seed density was highest in the fallow soil and highest in the upper soil layers for all land uses. A non-metric multidimensional scaling ordination of the SSB and AGV indicated that the SSBs were a poor reflection of the AGV. Based on these findings, spatial variations in landscape characteristics not only influence seed distribution and viability but also have the potential to influence population persistence. These results imply that successful restoration of fragmented ecosystems requires the addition of seeds and seedlings of target species
Relationships between soil seed banks and above-ground vegetation along a disturbance gradient in the W National Park trans-boundary biosphere reserve, West Africa
No full textAims
Vegetation succession depends on the availability of suitable propagules
in the soils, thus knowledge of soil seed banks is essential
for formulating effective strategies for restoring the vegetation of
degraded sites. The W National Park, the only trans-boundary biosphere
reserve in West Africa, is being extensively fragmented and
degraded in recent decades. The aims of this study were to assess
the reserve’s soil seed banks, their relationships with standing vegetation
and bundle of disturbances and their potential significance
for vegetation restoration.
Methods
The size and composition of the above-ground species vegetation
were assessed in nine plots of 1 ha each representing a range of
habitats with differing disturbance severity (low, intermediate and
high). A total of 702 soil samples were taken from three layers (0–3,
3–6 and 6–9 cm) and soil seed bank was analyzed using the seedling
emergence technique.
Important Findings
Generally, seeds of non-woody taxa dominated in samples from
all soil depths and habitats of all disturbance severities. The mean
soil seed density was 17.8, 24.4 and 26.3 seeds/dm3 in samples
from the least, intermediate and most disturbed sites, respectively,
and highest in the upper soil layers in all cases. The results indicate
that there is limited potential for restoring woody vegetation
solely from soil seed banks, and that woody species in the region
rely more on recently shed seeds trapped in the standing dead
biomass and litter on the ground than soil seed banks for regeneration.
Thus, human intervention is needed to accelerate forest
recovery, mainly through alleviating anthropogenic impacts on
the ecosystem (for instance, avoiding destruction of new seeds
by intense fire), and site manipulation to improve environmental
conditions for seedling establishment and growth. Other ways
of restoring forests than through the soil seed bank (e.g. sowing
seeds collected elsewhere, and planting tree seedlings) could also
be relevant
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
