1,720,996 research outputs found
The potential effect of climate change on tropical agroforestry systems; a study of Mt Kilimanjaro's Homegardens
No full textRainfed subsistence farmers in the tropics depending on natural resources for their crop production and wellbeing are highly vulnerable to climate change. Unless suitable adaptation measures are swiftly implemented, the wellbeing of these farmers could decline under climate change. Agroforestry, the integration and/or retention of trees within agricultural land, offers a potential adaptation solution through their various ecosystem services. However, whether and how agroforestry systems could themselves be impacted by climate change is currently not well understood.A systematic review of literature focusing on the tropics found that 1) the effects of climate change on tropical agroforestry systems remains an understudied research field, especially the effects on farmers, 2) based on the limited evidence climate change mostly negatively impacts tropical agroforestry systems, and 3), the current supporting evidence-based is not highly reliable. Following these review findings, this thesis empirically assesses how homegardens – a type of tropical agroforestry system – could be affected by climate change by using climate analogue analysis along Mt Kilimanjaro’s climate gradient, covering its ‘midland’ and ‘highland’ agroecological zones. The midland’s climate represents a potential warmer and drier future climate under climate change, while the highland’s climate represents the present climate conditions.To guide the thesis research, an interdisciplinary framework was developed using literature, existing frameworks, and qualitative fieldwork. The potential impacts of climate change on the homegarden’s tree-soil-crop ecological interactions supporting farmers’ banana production (farmers’ main food and cash crop), is then examined using structural equation modelling. The thesis then fully operationalises the conceptual framework through a mixed-methods study which examines variation and changes in provisioning ecosystem services and subsistence farmers’ wellbeing under different climate conditions to infer the potential impacts of climate change. The key findings from each chapter are then synthesised using causal loop diagrams to outline how climate change could affect homegardens as a social-ecological system.Overall, this thesis finds that climate change could negatively impact on the ecosystem services from homegardens underpinning subsistence farmers’ wellbeing. As such, farmers’ wellbeing may also decline, which could positively feedback into their crop production system and exacerbate declines in ecosystem services. This thesis concludes that decision-makers should consider the potential future climate scenarios for areas where agroforestry adaptation measures are being considered, as well as the availability of additional farmland that could be used to supplement farmers’ crop production to reduce their climate vulnerability
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
The potential impact of future climate change on the production of a major food and cash crop in tropical (sub)montane homegardens
No full textTropical agroforestry systems support the wellbeing of many smallholder farmers. These systems provide smallholders with crops for consumption and income through their ecological interactions between their tree, soil, and crop components. These interactions, however, could be vulnerable to changes in climate conditions; yet a reliable understanding of how this could happen is not well documented. The aim of this study is to understand how tree-soil-crop interactions and crop yield are affected by changes in climate conditions, which has implications for recognising how these systems could be affected by climate change. We used a space-for-time climate analogue approach, in conjunction with structural equation modelling, to empirically examine how warmer and drier climate conditions affects tree-soil-crop interactions and banana yield in Mt. Kilimanjaro's homegarden agroforest. Overall, the change in climate conditions negatively affected ecological interactions in the homegardens by destabilizing soil nutrient cycles. Banana yield, however, was mainly directly influenced by the climate. Banana yields could initially benefit from the warmer climate before later declining under water stress. Our findings imply that under increasingly warmer and drier climate conditions, homegarden agroforestry may not be a robust long-term farming practice which can protect smallholder's wellbeing unless effective irrigation measures are implemented
Variations on the Author
Full text link“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
Dataset of tree, soil, crop, climate variables for the Chagga Homegardens, supporting a publication 'The impact of different climate conditions on the production of a major food and cash crop in tropical (sub)montane homegardens'.
No full textThis data corresponds to the manuscript currently in review entitled 'the impact of different climate conditions on the production of a major food and cash crop in tropical (sub)montane homegardens'. The dataset comprises empirical measurements of physical and chemical soil properties taken at top soil (0-20cm) and subsoil (20-50cm) depths, on-farm trees, annual banana yield and climatic variables in Mt Kilimanjaro's Chagga Homegardens across 26 plots located along a vertical elevation transect spanning the area's midland and highland agro-ecological zones.
Tree and soil data were collected in 2013 as part of Dr Mathew Mpanda's PhD research at Sokoine University of Agriculture in Tanzania. Tree above-ground carbon, species richness, Shannon diversity index and composition values are the tree variables calculated and included in this dataset. These tree variables were calculated from measurements of tree height, diameter at breast height and identification of trees at the species level for each tree within each plot (excluding coffee shrubs) at 5 cm diameter at breast height and above. The above-ground biomass (kg/ha) estimations for each study site are based on Chave et al's (2014) allometric equation for measuring trees in the tropics. Above-ground biomass was halved to gain the tree above-ground carbon (AGC) stock. Tree AGC was also used to compute a species composition variables (% of tree biomass per plot) for legume trees species. The soil data was collected using composite and cumulative soil sampling. Samples were gathered using an inverted Y-shaped sampling design under the AfSIS protocol (UNEP 2012). Further details on the soil data collection process can be found in Mpanda et al (2016). The soil parameters included in the dataset are gravimetric soil moisture content (%), bulk density (g/cm3), Exchangeable Calcium (ExCa) (mg/kg), Exchangeable Potassium (K) (mg/kg), Exchangeable Sodium (mg/kg), Exchangeable Magnesium (Mg) (mg/kg), Exchangeable Actinium (Ac) (mg/kg), Exchangeable bases (Bas) (mg/kg), Iron concentration (Fe) (mgkg-1), Aluminium concentration (Al) (mgkg-1), Boron concentration (B) (mgkg-1), Copper concentration (Cu) (mgkg-1), Manganese concentration (Mn) (mgkg-1), Zinc concentration (Zn) (mgkg-1), Phosphorus concentration (P) (mgkg-1), Sulfur concentration (S) (mgkg-1), soil pH, ECd (acidity), ESP (alkalinity), total carbon (C) content (g/kg) and total nitrogen (N) content (g/kg). This dataset also includes the estimated mean annual precipitation (mm/yr), air temperature (°C), and relative humidity (%) for 2013 for each of the 26 plots. Climate data was derived from Appelhans et al (2016) high resolution climate maps on Mt Kilimanjaro's southern slopes, which used data from Hemp's (2006) rain gauge network. Temperature and relative humidity values were extracted from the relevant maps for each of the 26 plots. For the mean annual precipitation, values were estimated for each plot based on precipitation's strong linear relationship (R2 = 0.98) with elevation and data from two local rainfall stations. The main food and cash crop grown in the Chagga Homegardens is banana. In estimating the banana yield data (kg/ha) included in the attached dataset, a household survey was employed in the district in 2020 which gathered recalled estimates of household's 2013 annual yield. Next, based on a statistically significant quadratic relationship between banana yield and elevation (P <0.001), the associated equation was applied with elevation data to predict 2013's banana yield for each of the 26 plots. In the dataset (sheet 2), the banana yield values used to establish the equation are refined to those households in villages which are 1) located closest to the 26 plot transect and 2), do not use irrigation. The banana yield data for all households surveyed in 2020 can be made available upon request. Geo-references were removed from the dataset to protect the identity of the households which took part in the data collection process. If required, these values can be made available upon request to Martin Watts.
References:
Appelhans, T., Mwangomo, E., Otte, I., Detsch, F., Nauss, T. and Hemp, A., 2016. Eco-meteorological characteristics of the southern slopes of Kilimanjaro, Tanzania. International Journal of Climatology, 36 (9), 3245–3258. Chave, J., Réjou-Méchain, M., Búrquez, A., Chidumayo, E., Colgan, M. S., Delitti, W. B. C., Duque, A., Eid, T., Fearnside, P. M., Goodman, R. C., Henry, M., Martínez-Yrízar, A., Mugasha, W. A., Muller-Landau, H. C., Mencuccini, M., Nelson, B. W., Ngomanda, A., Nogueira, E. M., Ortiz-Malavassi, E., Pélissier, R., Ploton, P., Ryan, C. M., Saldarriaga, J. G. and Vieilledent, G., 2014. Improved allometric models to estimate the aboveground biomass of tropical trees. Global Change Biology, 20 (10), 3177–3190. Hemp, A., 2006. Continuum or zonation? Altitudinal gradients in the forest vegetation of Mt. Kilimanjaro. Plant Ecology [online], 184 (1), 27–42. Mpanda, M., Majule, A. E., Sinclair, F. and Marchant, R., 2016. Relationships between on-farm tree stocks and soil organic carbon along an altitudinal gradient, Mount Kilimanjaro, Tanzania. Forests Trees and Livelihoods [online], 25 (4), 255–266
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Dataset supporting the doctoral thesis "Assessing the impacts of future climate change on homegarden agroforestry systems: A case study on Mt Kilimanjaro's SE slopes"
No full textThe dataset is a mainly socio-economic quantitative household survey that measures indicators representing subsistence farmers' crop yield and household wellbeing in a homegarden agroforestry system in Tanzania's Moshi Rural District. The dataset was gathered for the purpose of assessing how a change in climate conditions (warmer and drier) could affect the wellbeing of subsistence farmers in the homegardens following a climate analogue analysis study design. This study pertains to Chapter 6 in the doctoral thesis "Assessing the impacts of future climate change on homegarden agroforestry systems: A case study on Mt Kilimanjaro's SE slopes".
The dataset includes:
-Hard_Copy_HH_Survey.pdf
-Coding_Sheet.xlsx
-Moshi_Homegarden_Data.xlsx
-Conversion_Units.pdf
The data will become available after the embargo of 4.12.2024 and can be accessed with CC BY license. </span
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
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