Search

Your search keyword '"Wellington N"' showing total 6 results
Start Over Author "Wellington N" Topic arid
6 results on '"Wellington N"'

1. Effect of Moisture Availability on Nitrogen and Phosphorus Uptake by Plants Under Semi-arid Soil Conditions

Author

P.N Macharia and Wellington N. Ekaya

Subjects
Moisture availability, Moisture, Phosphorus, food and beverages, chemistry.chemical_element, General Medicine, Biology, Nitrogen, Arid, chemistry, Agronomy, Soil water, Seeding, Legume
Abstract

A study was conducted in the semi-arid Kibwezi division of Kenya to investigate the effect of moisture availability on nitrogen and phosphorus uptake by plants. The study consisted of four treatments i.e. control, grass, legume, and grass/legume mixture. These were replicated on two sites with different soils. On each site, two sets of treatment were set up whereby one was WATER AVAILABILITY ON NITROGEN AND PHOSPHORUS UPTAKE BY RANGE PLANTS 361 given additional water, whereas one remained unwatered. The experiment was conducted during the short and the long rains. CP and P contents were determined for each of the treatments and seasons. The CP content of plants generally decreased as they grew from vegetative to seeding stage. Watering had no significant effect (P

Published
2002

2. Production and decomposition of plant litter in an arid rangeland of Kenya

Author

Wellington N. Ekaya, Jenesio I. Kinyamario, and Research funded by the UNEP Project on climate change and the productivity of tropical grasslands

Subjects
chemistry.chemical_classification, Nutrient cycle, Ecology, Forage, Plant litter, Arid, chemistry, Agronomy, Litter, Environmental science, Animal Science and Zoology, Organic matter, Ecosystem, Quadrat
Abstract

Data on litter production and decomposition in an arid rangeland in Kenya was collected over a two-year period. Litter sampling was carried out at monthly intervals using a rectangular 0.25m-2 quadrat frame. Litter within the quadrats was handpicked and washed with running water to get rid of soil particles, dried, and weighed. Weights were expressed on organic matter basis. Monthly litter production ranged from 31.4g m-2 to 130.0g m-2. Mean monthly yield was 92.5 ± 26g m-2, with a 28% coefficient of variation. There was no significant difference (p>0.01) in litter yield between 1992 and 1993. Rate of decomposition for aboveground material ranged from 0.005g g-1 day-1 to 0.084g g-1 day-1. The mean annual rate of decomposition was 0.026g g-1 day-1. Belowground plant material rates of decomposition spread from 0.009g g-1 day-1 to 0.062g g-1 day-1, with a mean annual rate of 0.041g g-1 day-1. Belowground material consistently decomposed faster than aboveground material. Peaks in both aboveground and belowground material decomposition rates coincided with rainfall peaks. Overall, in this arid environment, litter production and decomposition is pulsed in nature, and trends are closely related to rainfall occurrence. Moisture is thus a limiting factor both to the production and decomposition of litter. Belowground litter plays a significant role in nutrient cycling. Keywords: dead herbage yield; dryland ecosystem; ecosystem function; nutrient cycling African Journal of Range & Forage Science 2001, 18(2&3): 125-129

Published
2001

3. The Role of Moisture in the Successful Rehabilitation of Denuded Patches of a Semi-Arid Environment in Kenya

Author

Moses Nyangito, Wellington N. Ekaya, Kevin Z. Mganga, W.M. Muiri, N.K.R. Musimba, J. Francis, R. Von Kaufman, Nashon K. R. Musimba, Agnes W. Mwang’ombe, Arianne P. Verhagen, and D. Clavel

Subjects
business.product_category, Perennial grasses, biology, Perennial plant, Primary production, Land Use and Food Security, Landgebruik en Voedselzekerheid, References, biology.organism_classification, Arid, Plough, Cenchrus ciliaris, Agronomy, Loam, Foxtail, Eragrostis superba, Micro-carchments, Rangeland, business, General Environmental Science
Abstract

This study investigated the role of moisture in the successful rehabilitation of denuded patches in semi-arid lands of Kenya and the primary productivity of three perennial rangelands grasses namely Cenchrus ciliaris (African foxtail), Enteropogon macrostachyus (Bush rye) and Eragrostis superba (Maasai love grass) at three phenological stages (early growth, elongation and reproduction) as pure stands and two-grass mixtures. The grasses were sown on either rainfed (Sites 1 and 2) or simulated rainfall conditions (site 3). Site preparation in all the 3 sites involved mechanical bush clearing, use of fire and creation of micro-catchments using an ox-drawn plough. Soils in site 3 were sandy clay loams and those in sites 1 and 2 were sandy clays. There was total failure in establishment sites 1 and 2 under natural rainfall. Site 3 had good germination and subsequent establishment. These results were attributed to the moisture conditions in the three sites. There was a significant difference (p

Published
2011

4. Determinants of woody cover in African savannas

Author

Alioune Diouf, Steven I. Higgins, Mahesh Sankaran, Feetham Banyikwa, Jonas Ardö, William B. Sea, Niall P. Hanan, Nick Zambatis, Xavier Le Roux, Susan Ringrose, Herbert H. T. Prins, Kelly K. Caylor, Andries Bronn, Jacques Gignoux, Jörg Tews, Gabriela Bucini, Pierre Hiernaux, Brian S. Cade, Halszka Hrabar, Christie J. Feral, Michael B. Coughenour, Jayashree Ratnam, David J. Augustine, Edmund C. February, Robert J. Scholes, Kristine L. Metzger, Jeff Worden, Peter G. H. Frost, Wellington N. Ekaya, Fulco Ludwig, Natural Resource Ecology Laboratory [Fort Collins] (NREL), Colorado State University [Fort Collins] (CSU), Division of Forest Science and Technology, USDA Forest Service, Commanche National Grassland, US Geological Survey [Fort Collins], United States Geological Survey [Reston] (USGS), Fonctionnement et évolution des systèmes écologiques (FESE), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Helmholtz Zentrum für Umweltforschung = Helmholtz Centre for Environmental Research (UFZ), Laboratoire d'Ecologie Microbienne - UMR 5557 (LEM), Institut National de la Recherche Agronomique (INRA)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Ecole Nationale Vétérinaire de Lyon (ENVL)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Centre National de la Recherche Scientifique (CNRS), CSIRO Centre for Environment and Life Sciences, Commonwealth Scientific and Industrial Research Organisation [Canberra] (CSIRO), Department of Physical Geography and Ecosystem Science [Lund], Lund University [Lund], Department of Botany, University of Dar es Salaam (UDSM), Department of Agriculture and Game Management, Port Elizabeth Technikon, Department of Civil and Environmental Engineering, Princeton University, Centre de Suivi Ecologique [Dakar] (CSE), Department of Range Management, University of Nairobi (UoN), Environmental Sciences Department, University of Virginia, University of Cape Town, Institute of Environmental Studies, University of Zimbabwe (UZ), Centre d'études spatiales de la biosphère (CESBIO), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE), University of Pretoria [South Africa], Department of Zoology, University of Wisconsin-Madison, Resource Ecology Group, Wageningen University and Research [Wageningen] (WUR), Harry Oppenheimer Okavango Research Center, University of Botswana, Plant Ecology & Nature Conservation, University of Potsdam = Universität Potsdam, Scientific Services, Kruger National Park, Natural Resource Ecology Laboratory, University of Colorado Boulder [Boulder], United States Geological Survey [Reston] ( USGS ), Fonctionnement et évolution des systèmes écologiques ( FESE ), École normale supérieure - Paris ( ENS Paris ) -Université Pierre et Marie Curie - Paris 6 ( UPMC ) -Centre National de la Recherche Scientifique ( CNRS ), Umweltforschungszentrum Leipzig Halle, Sekt Okosyst Anal, Ecologie microbienne ( EM ), Centre National de la Recherche Scientifique ( CNRS ) -Ecole Nationale Vétérinaire de Lyon ( ENVL ) -Université Claude Bernard Lyon 1 ( UCBL ), Université de Lyon-Université de Lyon-Institut National de la Recherche Agronomique ( INRA ) -VetAgro Sup ( VAS ), Commonwealth Scientific and Industrial Research Organisation [Canberra] ( CSIRO ), Department of Physical Geography and Ecosystems Analysis [Lund], University of Dar es Salaam ( UDSM ), Centre de Suivi Ecologique, University of Nairobi ( UoN ), University of Virginia [Charlottesville], University of Zimbabwe, Centre d'études spatiales de la biosphère ( CESBIO ), Université Paul Sabatier - Toulouse 3 ( UPS ) -Institut national des sciences de l'Univers ( INSU - CNRS ) -Observatoire Midi-Pyrénées ( OMP ) -Centre National d'Etudes Spatiales ( CNES ) -Centre National de la Recherche Scientifique ( CNRS ), Mammal Research Institute, University of Wisconsin-Madison [Madison], Wageningen University and Research Centre [Wageningen] ( WUR ), Potsdam University, École normale supérieure - Paris (ENS Paris), Université de Lyon-Université de Lyon-Centre National de la Recherche Scientifique (CNRS)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS)-Ecole Nationale Vétérinaire de Lyon (ENVL), Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE)-Université Toulouse III - Paul Sabatier (UT3), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Université Fédérale Toulouse Midi-Pyrénées-Centre National de la Recherche Scientifique (CNRS)-Institut de Recherche pour le Développement (IRD)-Météo France-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), Universität Potsdam, École normale supérieure - Paris (ENS Paris)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Centre National de la Recherche Scientifique (CNRS), Helmholtz Zentrum für Umweltforschung (UFZ), Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Vétérinaire de Lyon (ENVL)-Université Claude Bernard Lyon 1 (UCBL), Université de Lyon-Université de Lyon-Institut National de la Recherche Agronomique (INRA)-VetAgro Sup - Institut national d'enseignement supérieur et de recherche en alimentation, santé animale, sciences agronomiques et de l'environnement (VAS), Université Fédérale Toulouse Midi-Pyrénées-Université Fédérale Toulouse Midi-Pyrénées-Observatoire Midi-Pyrénées (OMP), Université Fédérale Toulouse Midi-Pyrénées-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS), and Wageningen University and Research Centre [Wageningen] (WUR)

Subjects
0106 biological sciences, Canopy, 010504 meteorology & atmospheric sciences, quantile regression, Rain, Biome, Plant Ecology and Nature Conservation, [SDV.BID]Life Sciences [q-bio]/Biodiversity, Poaceae, 010603 evolutionary biology, 01 natural sciences, [ SDV.EE ] Life Sciences [q-bio]/Ecology, environment, Trees, Soil, DISPONIBILITE D'ELEMENT NUTRITIF, vegetation, Animals, Ecosystem, Biomass, 0105 earth and related environmental sciences, [ SDV.BID ] Life Sciences [q-bio]/Biodiversity, [SDV.EE]Life Sciences [q-bio]/Ecology, environment, Herbivore, [ SDE.BE ] Environmental Sciences/Biodiversity and Ecology, mechanisms, Multidisciplinary, WIMEK, SUBTANCE NUTRITIVE, Ecology, FEU, Vegetation, 15. Life on land, stability, PE&RC, Arid, Wood, Geography, Disturbance (ecology), Wildlife Ecology and Conservation, ZONE SEMI-ARIDE, Africa, Plant cover, Plantenecologie en Natuurbeheer, systems, Desert Climate, [SDE.BE]Environmental Sciences/Biodiversity and Ecology, fire, tree-grass coexistence
Abstract

Savannas are globally important ecosystems of great significance to human economies. In these biomes, which are characterized by the co-dominance of trees and grasses, woody cover is a chief determinant of ecosystem properties. The availability of resources (water, nutrients) and disturbance regimes (fire, herbivory) are thought to be important in regulating woody cover, but perceptions differ on which of these are the primary drivers of savanna structure. Here we show, using data from 854 sites across Africa, that maximum woody cover in savannas receiving a mean annual precipitation (MAP) of less than approximately 650 mm is constrained by, and increases linearly with, MAP. These arid and semi-arid savannas may be considered 'stable' systems in which water constrains woody cover and permits grasses to coexist, while fire, herbivory and soil properties interact to reduce woody cover below the MAP-controlled upper bound. Above a MAP of approximately 650 mm, savannas are 'unstable' systems in which MAP is sufficient for woody canopy closure, and disturbances (fire, herbivory) are required for the coexistence of trees and grass. These results provide insights into the nature of African savannas and suggest that future changes in precipitation may considerably affect their distribution and dynamics.

Published
2005

5. Abiotic and herbaceous vegetational characteristics of an arid rangeland in Kenya

Author

Wellington N. Ekaya, CN Karue, Jenesio I. Kinyamario, and research funded by the UNEP Project on climate change and the productivity of tropical grasslands

Subjects
Abiotic component, Hydrology, Ecology, Standing crop, Environmental science, Animal Science and Zoology, Relative humidity, Quadrat, Herbaceous plant, Rangeland, Arid, Structure and function
Abstract

A two-year study was conducted with an overall objective of characterising the structure and function of an arid rangeland in Kenya. A plot measuring 100 x 100m was used for this study. Data on rainfall and temperature were recorded at the plot site whereas data on evaporation rates and relative humidity were obtained from the meteorological office near the study site. Herbaceous aboveground material was sampled at monthly intervals using a rectangular 0.25m2 quadrat frame. Clipped material was separated by species and classified dead or live by physical examination. A 5cm diameter metal soil corer was used to sample belowground plant material, at monthly intervals. The sampled material was washed with running water over 2mm sieves and classified dead or live using the vital staining technique. All weights and calculations were based on organic weight. Total aboveground standing crop ranged from 84.6g m-2 to 295.4g m-2, with a mean of 162.3 60.6g m-2. Mean monthly aboveground standing crop for 1992 and 1993 was 142.8 53.8 and 178.5 63.3g m-2 respectively. The two values were significantly different (p0.01) in the mean belowground dead material yield between 1992 and 1993. In 1992, annual NPP was 439.2g m-2, giving a net primary productivity of 1.22g m-2day-1. Monthly NPP ranged from 17.2g m-2 to 90.1g m-2. In 1993, annual NPP was 944.5g m-2, equivalent to a net primary productivity of 2.62g m-2day-1. Monthly NPP was between 27.4g m-2 and 548.6g m-2. Over the 1992—1993 period, NPP was 1 383.7g m-2, equivalent to a productivity of 1.92g m-2day-1. Trends in monthly NPP closely followed the trend in rainfall. On the whole, herbaceous vegetation production and productivity were episodic in nature and closely linked to rainfall. The high primary productivity puts arid and semi-arid rangelands under sharp focus as CO2 sinks, whose role in the amelioration of greenhouse effect could be more important than is currently appreciated. Keywords: climatic elements; aboveground biomass; belowground biomass; primary productivity African Journal of Range & Forage Science 2001, 18(2&3): 117-124

Published
2001

Catalog

Books, media, physical & digital resources
See catalog results