Abstract
The interest in using ecological bioindicators - species or higher taxa, whose presence/absence or abundance reflect the abiotic or biotic state of an ecosystem - as cost-effective means of ecological monitoring has been globally increasing. The main aim of this study was to assess if such ecological bioindicator species could be identified within Afromontane grassland avifauna that would be used for monitoring the effects of livestock grazing on ecosystem in the Bale Mountains of Ethiopia. We collected data on birds and vegetation structure along 14 transects each in the light (protected) and heavy (unprotected) grazing sites in June 2014 (referred to as the first sampling period) and in December 2014 (the second sampling period). Then, we (i) initially identified potential bioindicator species for the light grazing site, based on data collected during the first sampling period; (ii) examined relationships between abundance of these bioindicators and level of grazing pressure; (iii) tested the consistency of those initially selected bioindicator species, based on independent data collected during the second sampling period. We used the Indicator Value (IndVal) Analysis method to identify bioindicator species for the light grazing site. Species with significant IndVal>60% were considered as potential bioindicator for the site compared to the heavy grazing site. Six species were initially identified as potential bioindicators from the first sampling period dataset, and four of these species were again consistently identified from the second sampling period. Furthermore, abundance of the bioindicators had significantly declined with increasing grazing pressure, but positively correlated with four habitat variables (i.e. heights of shrub, herb and grass, and cover of shrub). These findings suggest that those consistently identified four species represent suite of reliable bioindicators that can successfully be used for monitoring of changes in habitat structure in the site. Recommendations on how to apply these findings for ecological monitoring are provided.
Highlights
IntroductionBioindicators are species or group of species, or higher taxa, whose biological or ecological attributes (e.g. presence/absence, abundance, survival rate, reproductive success, etc) readily reflect the abiotic or biotic state of an environment (environmental bioindicators), an ecosystem (ecological bioindicators), or the diversity of taxa (biodiversity bioindicators) (McGeoch, 1998; Momona Ethiopian Journal of Science (MEJS), V11(2):186-208, 2019 ©CNCS, Mekelle University,ISSN:2220-184XSubmitted on: 30-03-2016Accepted on: 28-06-2019Addisu Asefa and Girma Mengesha (MEJS)Volume11(2):187-208, 2019Niemi and McDonald, 2004)
Bioindicators are species or group of species, or higher taxa, whose biological or ecological attributes readily reflect the abiotic or biotic state of an environment, an ecosystem, or the diversity of taxa (McGeoch, 1998; Momona Ethiopian Journal of Science (MEJS), V11(2):186-208, 2019 ©CNCS, Mekelle University,ISSN:2220-184XSubmitted on: 30-03-2016Accepted on: 28-06-2019Addisu Asefa and Girma Mengesha (MEJS)Volume11(2):187-208, 2019Niemi and McDonald, 2004)
The specific objectives of this study were to: (i) identify potential bioindicator bird species for the low grazing grassland site based on data collected during the first sampling period; (ii) test the responses of bird species that were initially identified as bioindicators of habitat change to both grazing pressure and grazing-induced changes in vegetation structure; (iii) test the consistency, and estimate the reliability, of initially selected potential bioindicator species using data collected in the area during the second sampling period; and, (iv) develop predictive models relating abundance of bioindicators with habitat parameters which the bioindicators are supposed to be indicator for
Summary
Bioindicators are species or group of species, or higher taxa, whose biological or ecological attributes (e.g. presence/absence, abundance, survival rate, reproductive success, etc) readily reflect the abiotic or biotic state of an environment (environmental bioindicators), an ecosystem (ecological bioindicators), or the diversity of taxa (biodiversity bioindicators) (McGeoch, 1998; Momona Ethiopian Journal of Science (MEJS), V11(2):186-208, 2019 ©CNCS, Mekelle University,ISSN:2220-184XSubmitted on: 30-03-2016Accepted on: 28-06-2019Addisu Asefa and Girma Mengesha (MEJS)Volume11(2):187-208, 2019Niemi and McDonald, 2004). The premise to use bioindicators for ecological monitoring has come from the fact that most ecosystems are biologically and ecologically highly diverse and complex, making difficult to undertake surveys on tall taxa during monitoring (Noss, 1990). Application of the bioindication concept in conservation initiatives has been advocated to be used as a simple and cost-effective means of ecological monitoring to assess the current and predict the future healthiness of ecosystems (Noss, 1990; McGeoch, 1998; Carignan and Villard, 2002; Niemi and McDona, 2004). According to McGeoch (1998), the first step during bioindicator species identification is clearly defining the specific objectives—i.e. what is to be indicated by monitoring the bioindicators? Once the objectives are defined and potential bioindicator species are identified based on a priori suitability criteria
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