Piospheric influence on forage species composition and abundance in semi-arid Karamoja sub-region, Uganda

Egeru, Anthony; Wasonga, Oliver Vivian; MacOpiyo, Laban; Mburu, John; Tabuti, John R. S.; Mwanjalolo, Majaliwa

doi:10.1186/s13570-015-0032-y

Cited by 21 publications

(23 citation statements)

References 39 publications

(57 reference statements)

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“…This evenly distributed grazing pressure along the river reducing animal impact on vegetation, hence the higher species diversity. Similar results were observed by Egeru et al (2015) in the Karamoja sub-region of Uganda who attributed the observations to varying use of landscape, piosphere location, and herder characteristics. The results further corroborate those Hu et al (2015) that herd movements impacted on species composition, diversity, and richness.…”

Section: Shannon-wiener Diversity Index Species Richness and Pielousupporting

confidence: 84%

“…Most forbs observed were also perennial and survived for more than a season. Pre-dominance of perennial grasses during dry and wet seasons was also observed by Egeru et al (2015) in the Karamoja sub-region of Uganda. As noted by Kasale (2013) and Wesuls et al (2013), perennial grasses possess a self-seeding characteristic, are tolerant to drought, and have a spreading capacity that enable them to develop good cover and hence survive both seasons.…”

Section: Shannon-wiener Diversity Index Species Richness and Pieloumentioning

confidence: 81%

“…C. dactylon was, however, more pronounced near the water points. This was because C. dactylon can withstand heavy grazing, is extremely tolerant to fire, and adapts to various climatic and edaphic conditions, in addition to being tolerant to both salinity and flooding (Rita et al 2012;Egeru et al 2015). In a related study in the Sonamarg area of the Kashmir Himalayas, Mir et al (2015) also observed that the importance value index of C. dactylon significantly increased during peak grazing seasons.…”

Section: Species Compositionmentioning

confidence: 99%

“…Impacts on soil include, among others, alterations to soil nutrients such as organic carbon, total nitrogen and pH (Smet and Ward 2006;Shahriary et al 2012), soil compaction, reduction of soil aggregate stability and changes in soil texture. The effects on vegetation include increased shrub mortality, plant defoliation, alterations to species composition and demography (Riginos and Hoffman 2003), and changes in herbaceous vegetation (Egeru et al 2015). Plant defoliation by livestock and wildlife grazing around these piospheres increases palatable species' mortality, thereby reducing their ability to favorably compete with less palatable alien and exotic species (Hunt et al 2002;Shahriary et al 2012).…”

Section: Introductionmentioning

confidence: 99%

“…Piospheric studies on species composition, richness, and diversity indices have been done in most parts of the world including Australia (Landman et al 2012), Asia (Shahriary et al 2012), Southern Africa (Todd 2006), Northern Africa (Tarhouni et al 2007), and Uganda (Egeru 2014;Egeru et al 2015). Nevertheless, there have been no studies conducted in Kenya, especially in the southern rangelands where water interventions have been widely undertaken to alleviate water shortage and enhance pastoral livelihoods (Opiyo et al 2015).…”

Section: Introductionmentioning

confidence: 99%

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Plant species composition and diversity depending on piospheres and seasonality in the southern rangelands of Kenya

et al. 2017

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Introduction: Scarcity of water in the rangelands of Kenya has led to the introduction of piospheres. Previous research has however produced contrasting results on the effects of piospheres and seasonality on ShannonWiener's diversity index, and therefore, this information is still deficient. In this study, the impact of these piospheres on plant species composition, diversity, and richness was assessed. Methods: Vegetation sampling was done during both the long rains (April) and the dry season (August). Three piosphere types (dam, trough, and a seasonal river) were studied using 0.25 m 2 quadrats to sample vegetation at intervals of 20 m along 100-m transects. Four 100-m transects were used per piosphere (north, east, south, and west directions). Shannon-Wiener's diversity index was used to determine species richness and composition. Twoway ANOVA was used to determine if piospheric distance had an effect on species diversity, richness, and evenness using GenStat 15th edition. Results: A total of 22 grasses and 29 forbs were recorded in the study area. The most abundant grasses near the piospheres were Eragrostis tenuifolia (12.9%) and Cynodon dactylon (10.6%). E. tenuifolia is an increaser species and was therefore most abundant in areas of severe grazing while C. dactylon has been known to be tolerant to grazing. The most abundant forbs were Crotalaria brevidens (37.5%). The Shannon-Wiener diversity index significantly increased (F = 25.07, P = 0.001) with distance from the three piospheres owing to the high grazing intensity near the piospheres and was significantly different between piospheres, being higher (F = 10.05, P = 0.001) at 20 m from the river (1.2 ± 0.1) compared to a similar distance from the dam (0.9 ± 0.1) and the trough (0.8 ± 0.2). This was probably because the trough was smaller in size compared to the other piospheres, thereby concentrating more grazing animals per unit area and causing a greater impact on plant species. Conclusions: The study demonstrated that species diversity, richness, and evenness were low near the piospheres due to heavy grazing. Similarly, the lowest species diversity, richness, and evenness were recorded near the trough compared to the dam and the river. This study therefore recommends that range reseeding and rest period be done to rehabilitate degraded areas and facilitate plant regeneration. Larger piospheres should also be used to minimize animal impact per unit area.

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Section: Shannon-wiener Diversity Index Species Richness and Pielousupporting

confidence: 84%

Section: Shannon-wiener Diversity Index Species Richness and Pieloumentioning

confidence: 81%

Section: Species Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Plant species composition and diversity depending on piospheres and seasonality in the southern rangelands of Kenya

et al. 2017

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The effects of herbivore aggregations at water sources on savanna plants differ across soil and climate gradients

Titcomb

Amooni

Mantas

et al. 2021

Ecological Applications

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Water sources in arid and semiarid ecosystems support humans, wildlife, and domestic animals, forming nodes of activity that sculpt surrounding plant communities and impact critical grazing and soil systems. However, global aridification and changing surface water supply threaten to disrupt these water resources, with strong implications for conservation and management of these ecosystems. To understand how effects of herbivore aggregation at water impact plant communities across contexts, we measured herbivore activity, plant height, cover (trees, grasses, forbs, and bare ground), diversity, and composition at 17 paired water sources and matrix sites across a range of abiotic factors in a semiarid savanna in Kenya. The effects of proximity to surface water and herbivore aggregation on plant communities varied substantially depending on soil and rainfall. In arid areas with nutrient‐poor sandy soils, forb and tree cover were 50% lower at water sources compared to neighboring matrix sites, bare ground was 20% higher, species richness was 15% lower, and a single globally important grazing grass (Cynodon dactylon) dominated 60% of transects. However, in mesic areas with nutrient‐rich finely textured soils, species richness was 25% higher, despite a 40% increase in bare ground, concurrent with the decline of a dominant tall grass (Themeda triandra) and increase in C. dactylon and other grass species near water sources. Recent rainfall was important for grasses; cover was higher relative to matrix sites only during wet periods, a potential indication of compensatory grazing. These findings suggest that effects of herbivore aggregation on vegetation diversity and composition will vary in magnitude, and in some cases direction, depending on other factors at the site. Where moisture and nutrient resources are high and promote the dominance of few plant species, herbivore aggregations may maintain diversity by promoting grazing lawns and increasing nondominant species cover. However, in arid conditions and sites with low nutrient availability, diversity can be substantially reduced by these aggregations. Our results highlight the importance of considering abiotic conditions when managing for effects of herbivore aggregations near water. This will be particularly important for future managers in light of growing global aridification and surface water changes.

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Small effects of livestock grazing intensification on diversity, abundance, and composition in a dryland plant community

Jordan

Palmquist

Burke

et al. 2022

Ecological Applications

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Livestock grazing is a globally important land use and has the potential to significantly influence plant community structure and ecosystem function, yet several critical knowledge gaps remain on the direction and magnitude of grazing impacts. Furthermore, much of our understanding of the long‐term effects on plant community composition and structure are based on grazer exclusion experiments, which explicitly avoid characterizing effects along grazing intensity gradients. We sampled big sagebrush plant communities using 68 plots located along grazing intensity gradients to determine how grazing intensity influences multiple aspects of plant community structure over time. This was accomplished by sampling plant communities at different distances from 17 artificial watering sources, using distance from water and cow dung density as proxies for grazing intensity at individual plots. Total vegetation cover and total grass cover were negatively related to grazing intensity, and cover of annual forbs, exotic cover, and exotic richness were positively related to grazing intensity. In contrast, species richness and composition, bunchgrass biomass, shrub density and size, percentage cover of bare ground, litter, and biological soil crusts did not vary along our grazing intensity gradients, in spite of our expectations to the contrary. Our results suggest that the effects of livestock grazing over multiple decades (mean = 46 years) in our sites are relatively small, especially for native perennial species, and that the big sagebrush plant communities we sampled are somewhat resistant to livestock grazing. Collectively, our findings are consistent with existing evidence that indicates the stability of the big sagebrush plant functional type composition under current grazing management regimes.

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Piospheric influence on forage species composition and abundance in semi-arid Karamoja sub-region, Uganda

Cited by 21 publications

References 39 publications

Plant species composition and diversity depending on piospheres and seasonality in the southern rangelands of Kenya

Plant species composition and diversity depending on piospheres and seasonality in the southern rangelands of Kenya

The effects of herbivore aggregations at water sources on savanna plants differ across soil and climate gradients

Small effects of livestock grazing intensification on diversity, abundance, and composition in a dryland plant community

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