The Rainfall-Altitude Relation and Its Ecological Significance in Kenya

Trapnell, C. G.; Griffiths, J. F.

doi:10.1080/03670074.1960.11665266

Cited by 12 publications

(4 citation statements)

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“…Vegetation in the study area is a mosaic of Combretum and Acacia formations (Figure e,f; Kindt et al, ; Trapnell & Graffiths, ), forming a narrow belt on relatively higher and moister portions of the Acacia ‐tall grass and open grassland savannah of East Africa (Edwards, ). Much of this natural vegetation is highly fragmented, largely, by cultivated farmlands inhabited by a population of smallholding sedentary agricultural communities, who exercise subsistence‐oriented mixed farming systems that include both crop and livestock production (Jaetzold, Hornetz, Shisanya, & Schmidt, ).…”

Section: Methodsmentioning

confidence: 99%

“…The idealised features of ASS systems are relevant to two strikingly different vegetation systems (broad‐leaved nonspiny Combretum woodland and fine‐leaved spiny Acacia vegetation formations) found in the mesic savannah ecosystems of southeastern Kenya (see Trapnell & Graffiths, ; Pratt, Greenway, & Gwynne, ; and Kindt et al, ). Mesic savannah ecosystems of southeastern Kenya are within the larger Somali‐Masai phytogeographical region (White, ).…”

Section: Introductionmentioning

confidence: 99%

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Characterisation of alternative stable vegetation assemblages in a mesic savannah in Kenya

et al. 2020

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The phenomenon of sharp boundaries between distinctive vegetation types occurring under the same climatic conditions has often been interpreted by plant ecologists to characterise alternative stable states (ASS). The phenomenon may be relevant in explaining two strikingly different vegetation formations (broad‐leaved nonspiny Combretum and fine‐leaved spiny Acacia) co‐occurring in mesic savannah of southeastern Kenya. We hypothesise that the two vegetation within southeastern Kenya ecosystems represent ASS whose transition may be a response to soil characteristics switch. To explore our hypothesis, we analysed empirical field data of woody species and soil characteristics from 57 plots that included 25 from Combretum and 32 from Acacia vegetation formations. We compared floristic composition and soil characteristics between the two systems and correlated edaphic statuses and vegetation states. We encountered 2,749 woody plant individuals, representing 115 species, 87 genera and 40 families. We found that the two vegetation had discrete woody species composition and soil characteristics, and also a significant species–edaphic association. The results are consistent with the ASS theory demonstrating that soil characteristics are among the important micro‐environmental filters driving and maintaining woody vegetation mosaics in the tropics. Importantly, understanding ASS has ramifications for sustainable utilisation of woody plant resources in East African savannahs.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Characterisation of alternative stable vegetation assemblages in a mesic savannah in Kenya

et al. 2020

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“…On the most direct level of interaction between anthropogenic and biophysical factors, prime locations and modes of farming in East Africa coincide with areas of high vulnerability. One example is that precipitation and soil fertility are often linked to altitude, with more suitable areas for agriculture in sloped highlands (Kurukulasuriya and Mendelsohn 2008;Trapnell and Griffiths 1960). Moreover, farmers often solely depend on rain for watering their crops, whereby they time the planting during the beginning of the rainy season (Barron et al 2003;Traerup and Mertz 2011), leaving the fields exposed to the full force of torrential rains (Thornes 1990).…”

Section: Introductionmentioning

confidence: 99%

Drivers of increased soil erosion in East Africa’s agro-pastoral systems: changing interactions between the social, economic and natural domains

et al. 2019

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Increased soil erosion is one of the main drivers of land degradation in East Africa's agricultural and pastoral landscapes. This wicked problem is rooted in historic disruptions to co-adapted agro-pastoral systems. Introduction of agricultural growth policies by centralised governance resulted in temporal and spatial scale mismatches with the complex and dynamic East African environment, which subsequently contributed to soil exhaustion, declining fertility and increased soil erosion. Coercive policies of land use, privatisation, sedentarisation, exclusion and marginalisation led to a gradual erosion of the indigenous social and economic structures. Combined with the inability of the new nation-states to provide many of the services necessary for (re)developing the social and economic domains, many communities are lacking key components enabling sustainable adaptation to changing internal and external shocks and pressures. Exemplary is the absence of growth in agricultural productivity and livelihood options outside of agriculture, which prohibits the absorption of an increasing population and pushes communities towards overexploitation of natural resources. This further increases social and economic pressures on ecosystems, locking agro-pastoral systems in a downward spiral of degradation. For the development and implementation of sustainable land management plans to be sustainable, authorities need to take the complex drivers of increased soil erosion into consideration. Examples from sustainable intensification responses to the demands of population increase, demonstrate that the integrity of locally adapted systems needs to be protected, but not isolated, from external pressures. Communities have to increase productivity and diversify their economy by building upon, not abandoning, existing linkages between the social, economic and natural domains. Locally adapted management practices need to be integrated in regional, national and supra-national institutions. A nested political and economic framework, wherein local communities are able to access agricultural technologies and state services, is a key prerequisite towards regional development of sustainable agro-pastoral systems that safeguard soil health, food and livelihood security.

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“…The vegetation of the Reserve away from the riverine strip is principally of the 'semi-arid bushland' type (Lind & Morrison, 1974) or 'Acacia desert-scrub' and 'Acuciu short-grass' types in the terminology of Walter (1971). According to the maps and descriptions of Pratt, Greenway & Gwynne (1966) most of the communities fall into their 'ecological zone V', consisting largely of 'wooded grassland plus bush grassland' (WGBG), or the 'thorn-bushland and thicket' of Trapnell & Griffiths (1960). The Uaso Nyiro riverine strip is a complex mixture of communities whose status is clarified and described in detail below.…”

Section: Introductionmentioning

confidence: 99%

The vegetation of the Samburu–Isiolo Game Reserve

Barkham

Rainy

1976

African Journal of Ecology

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Summary (1) Communities were identified in the field from presence/absence records of species using a form of progressive approximation. These communities were then mapped from aerial photographs of the Reserve area and boundaries were later checked on the ground. The quantitative characteristics of the communities were described in terms of cover and frequency. (2) The data were subjected to standard computer analyses and these results are used in an assessment of the validity of the original subjective techniques. (3) A hypothetical scheme is suggested which explains the principal lines of vegetation variation in terms of water availability and soil salinity. A number of related vegetation catenae may be recognized in addition to an east–west trend of increasing tree cover which is attributed to decreasing salinity along the riverine strip. (4) It is concluded that the effects of grazing and burning regimes are superimposed upon those of the physical environment and that further rapid changes in vegetation composition will take place within the next few decades.

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The Rainfall-Altitude Relation and Its Ecological Significance in Kenya

Cited by 12 publications

References 4 publications

Characterisation of alternative stable vegetation assemblages in a mesic savannah in Kenya

Characterisation of alternative stable vegetation assemblages in a mesic savannah in Kenya

Drivers of increased soil erosion in East Africa’s agro-pastoral systems: changing interactions between the social, economic and natural domains

The vegetation of the Samburu–Isiolo Game Reserve

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