Allellopathic potential of invasive Psidium guajava L., against selected native tree species in Kakamega Tropical Forest, Western Kenya.

Kawawa, R.C. A; Obiri, John; Muyekho, Francis N.; Omayio, Dennis O.; Agevi, Humphrey; Mwaura, A; Obiet, Lenard; Kimutai, D.K; Sifuna, A.W

doi:10.9790/3008-1105028086

Cited by 11 publications

(8 citation statements)

References 14 publications

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“…The aspect of facilitating secondary forest succession tends to contradict observations by some studies that have reported that P. guajava exerts allelopathic effects on other woody species, which may inhibit their recruitment and growth [Chapla & Campos, 2010;Kawawa et al, 2016]. On the contrary, our results suggest that the species is an extremely aggressive colonizer of open fields, but it easily facilitates the recruitment and growth of shade-tolerant native species, which emerge from its shade and grow alongside it.…”

Section: P Guajava Invasion and Interactions With Other Woody Speciescontrasting

confidence: 93%

“…Despite being highly invasive in some parts of the world, P. guajava is not so noxious in others. In such areas, attention has been focused on its desirable economic attributes [Ojewole et al, 2008;Kawawa et al, 2016]. Such positive attributes have made some countries to downgrade it to a category two invader, which means that it is allowable under managed conditions.…”

Section: Introductionmentioning

confidence: 99%

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Ecological Manipulation of Psidium guajava to Facilitate Secondary Forest Succession in Tropical Forests

Otuoma¹,

Nyongesah²,

Owino³

et al. 2020

J. Ecol. Eng.

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Psidium guajava L. has been documented as an exotic invasive species in many parts of the world, but little is known about its interactions with native woody species during secondary forest succession in tropical forests. Its invasion and interactions with native species in different stages of secondary forest succession were assessed in Kakamega Rainforest in western Kenya. The study covered three forest blocks each with five different forest types, namely: open fields, young secondary forest, middle-aged secondary forest, old-growth secondary forest and disturbed primary forest, which served as the control. Open fields that were subjected to frequent clearing to control the spread of Psidium guajava remained under a thicket of the species two decades later. On the other hand, open fields where Psidium guajava was ignored, either due to lack of resources or sheer neglect, transformed into young secondary forest stands within a decade. The transformation increased woody species richness from 2.0±0.0 to 5.0±0.0 ha-1 , and the Shannon diversity index from 0.30±0.33 to 1.10±0.01. It reduced the dominance of Psidium guajava from 80.5±22.7 to 62.26±0.84% and changed the canopy structure. The change in canopy structure led to the mortality of Psidium guajava stems in the sub-canopy and understory layer, which significantly reduced its stem density from 1,111±313 to 639.4±45 stems ha-1. The pattern was repeated in middle-aged secondary forest stands with woody species richness increasing to 26.0±8.2 ha-1 , and Shannon index to 2.72±0.32. Psidium guajava's dominance and stem density decreased further to 30.44% and 400.57 stems ha-1 , respectively, due to mortality attributed to shading by native tree species. In the old-growth secondary forest, only snags of Psidium guajava were recorded. The species was not represented in the disturbed primary forest. The results indicate that Psidium guajava facilitates secondary forest succession by allowing shade-tolerant native tree species to recruit and grow in its shade. It is thereafter eliminated when the native species close the forest canopy. The species can be ecologically manipulated to facilitate post-disturbance forest regrowth and thereafter removing it when the forest canopy begins to close.

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Section: P Guajava Invasion and Interactions With Other Woody Speciescontrasting

confidence: 93%

Section: Introductionmentioning

confidence: 99%

Ecological Manipulation of Psidium guajava to Facilitate Secondary Forest Succession in Tropical Forests

Otuoma¹,

Nyongesah²,

Owino³

et al. 2020

J. Ecol. Eng.

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“…This implies that the majority of the species had the highest number of individuals at relatively low DBH and height classes with a gradual decrease towards high DBH and height size classes (Fashing and Mwangi Gathua, 2004;Senbeta and Denich, 2006;Gebrehiwot and Hundera, 2014). This indicates a healthier tree population of the woody species under the treatments (Abebe et al, 2013;Kawawa et al, 2016). Despite the saplings being the majority not all of them grow to maturity because of the allelopathic effect from some of the larger species for instance, the Eucalyptus species which are the most in the Eucalyptus dominated tree stand in study area (Kawawa et al, 2016).…”

Section: Discussionmentioning

confidence: 94%

Trade-Offs in Tree Species Selection and Carbon Offset on Farms Adjacent to Kakamega-Nandi Forest Ecosystem in Kenya

Muigai,

Agevi,

Otuoma

et al. 2023

Trop Subtrop Agroecosyst

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Background: Growing of trees on-farms has contributed significantly in easing pressure on the Kakamega–Nandi Forest Ecosystem. There are however concerns that Eucalyptus species is becoming the dominant tree in this landscape and may have adverse effects on the environment. Objectives: To determine the trade-offs in tree species selection and carbon offsets on farms in the margins of the Kakamega - Nandi Forest Ecosystem. Methodology: It employed a nested experimental design where the study area was divided into three 3x1 km sentinel blocks. Three different landscape models were chosen: Eucalyptus dominated tree stand, mixed tree stands and pure native tree stands. A sample plot comprised a main plot of 20m by 10m plot for measuring trees with a diameter at breast height (DBH) ≥ 10 cm, a sub-plot of 10m by 5m nested within the main plot for measuring saplings and shrubs of DBH less than 10cm. Data was collected on tree species type, stem DBH for trees, tree height, counts of trees, saplings and shrubs. The data was subjected to both exploratory and inferential statistical analysis using R Gui Version 4.2.1. Woody species diversity and carbon stocks were subjected to analysis of variance (ANOVA) at 5% significance level. Results: Native dominated tree stands had the highest biomass carbon (0.50-512.84 MgC ha-1) followed by mixed tree stands (0.10-110.82 MgC ha-1). Eucalyptus dominated was the least (0.10- 68.58 MgC ha-1) The above ground biomass in the Eucalyptus dominated tree stands and mixed trees stands was significantly lower than in the adjacent native trees stands (p=0.001). The mean carbon estimated in the treatments was 2.62 MgC ha-1 in the Eucalyptus trees dominated stands, 3.09 MgC ha-1 in mixed trees species stands and 19.05 MgC ha-1 in native tree species stand. Implications: Increase in the concentration of Eucalyptus trees led to a reduction in tree diversity. Trees in the Eucalyptus dominated tree stand and mixed trees stand had significantly lower stem diameters, basal area and tree biomass than in the adjacent indigenous trees stand. The fast rate of growth of Eucalyptus trees may have ensured that the trees grow fast at the expense of other woody species due to water and nutrient competition. Conclusion: The study revealed a general trend of increasing biomass carbon with increasing tree size in all the treatments. The majority of large trees were found in native tree stand indicating that they store majority of biomass carbon stocks. Across the treatment, carbon sequestration in the trees was directly related to above ground biomass production.

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“…However, despite being considered naturalized, this species appears in the park as a casual exotic (Richardson et al 2000;Pysek et al 2004;Moro et al 2012), since it was in a reproductive form, but with few individuals, not enough to be considered a viable population. This species was recorded in a few trails in the park, which is positive in terms of conservation, since P. guajava has allelopathic potential over other species (Chapla & Campos 2010;Kawawa et al 2016), which can negatively affect natural ecosystems.…”

Section: Psidium Striatulummentioning

confidence: 98%

Floristic inventory of Myrtaceae of Parque Nacional do Iguaçu, Paraná, Brazil

et al. 2023

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Myrtaceae is a diverse family in Brazil and the sixth most representative family in the Atlantic Forest. In Paraná, the Parque Nacional do Iguaçu (ParNa Iguaçu) is a large National Park and also one of the largest remnants of this phytogeographic domain. The objective of the present study was to carry out a floristic inventory of the Myrtaceae of the ParNa Iguaçu, presenting an identification key to the species, illustrations, conservation status evaluation, and comments on geographic distribution and phenology. The collections were carried out between May 2019 and March 2020 in two areas composed of Seasonal Semideciduous Forest and a transitional area to Mixed Ombrophilous Forest. In addition to the samples collected by us, material from other herbaria were also examined. Twenty-five native species and one exotic species of Myrtaceae were found, distributed in seven genera. Eugenia was the most representative genus with 11 species. Of the 26 species, seven are new occurrences for ParNa Iguaçu. From the samples collected in this research and other records in the northwest and west regions of the state of Paraná, the presence of Psidium striatulum in Seasonal Semideciduous Forest is confirmed. Eugenia myrciariifolia was the only species on Brazil’s endangered species list, the IUCN conservation status of which is Endangered (EN). The other species were considered as Least Concern (LC), but some of these species are restricted to certain areas or types of vegetation. Therefore, we conclude that ParNa Iguaçu contributes to the maintenance of these species in their natural environment.

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Allellopathic potential of invasive Psidium guajava L., against selected native tree species in Kakamega Tropical Forest, Western Kenya.

Cited by 11 publications

References 14 publications

Ecological Manipulation of Psidium guajava to Facilitate Secondary Forest Succession in Tropical Forests

Ecological Manipulation of Psidium guajava to Facilitate Secondary Forest Succession in Tropical Forests

Trade-Offs in Tree Species Selection and Carbon Offset on Farms Adjacent to Kakamega-Nandi Forest Ecosystem in Kenya

Floristic inventory of Myrtaceae of Parque Nacional do Iguaçu, Paraná, Brazil

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