Enhancement of diversity, stand structure and regeneration of woody species through area exclosure: the case of a mopane woodland in northern Botswana

Abstract

This study examines the effect of closed area on woody species regeneration by comparing the woody species regeneration among closure, open woodland, and degraded land areas in Loma Bosa district, Dawuro zone in southern Ethiopia. Results show that Simpson's Diversity Index was 7.24 for woody species in closed area, 6.01 in open woodland and 3.40 in open degraded land area. Shannon-Weiner Diversity Index(H') was 2.26 for woody species in closed area, 2.38 in open woodland area and 1.56 in open degraded land area. The results of Sorenson's similarity coe cients indicates woody species composition in closed area are highly correlated with open woodland areas. Wood species density were 2,225 ha-1 , 1,642 ha-1 , and 297 ha-1 for closed area, open woodland area, and open degraded land area, respectively. The results indicate that closed area development enhanced species composition, richness, diversity, woody vegetation regeneration, inverted J shape Diameter at Breast Height (DBH) and height class and higher woody species density and crown cover class percentage compared to open degraded area. Overall results from this study indicated that area closure is important for improvement of woody species regeneration in the study area. 1. Introduction Land degradation, a process of diminishing the productive potentials of land resources, is one of the serious environmental problems at the global scale (Le et al., 2016; Nkonya et al., 2016). It has been increasing in severity and extent in many parts of the world. For instance, in 2008, the United Nations Food and Agriculture Organization (FAO) reported that more than 20% of all cultivated areas, 30% of forests, and 10% of grasslands undergoing degradation in the world. A recent study by Le et al. (2016) reported that about 29% of the global land area covered by the degraded land, which are affecting about 3.2 billion people who are especially rural communities, smallholder farmers, and the very poor in the developing regions of the world. Land degradation mainly triggered by population pressure, expansion of agricultural land, deforestation, and over-exploitation of the natural resources (Mganga et al., 2015; Yirdaw et al., 2017, Manaye et al., 2019). It is one of the major drivers of declining agricultural productivity, increasing food insecurity, rural poverty, and deterioration of ecological functions in the world (Gashaw et al., 2018). Thus, combating of land degradation though rehabilitation and ecological restoration is important to ensure the long-term productivity of the land resources and survival of life on the earth (Asmare & Gure, 2019; Manaye et al., 2019). Successful land rehabilitation and ecological restoration activities enhances improved land productivity, food security, livelihoods, biodiversity, ecological balance, and other ecosystem services and functions (Mureithi et al., 2014; Reside et al., 2017; Mekuria et al., 2017). Closuring degraded area from human and livestock interference is one of the successful rehabilitation activities to combat land degr...

Species composition, stand structure, and regeneration status of tree species in dry Afromontane forests of Awi Zone, northwestern Ethiopia

“…The result revealed that the five studied forests contain different tree species, which fulfill critical ecological, e.g., provision of habitats for other plants and wild animals, as well as economic functions. The species composition recorded in the studied forests was comparable to those of another dry Afromontane forest of Ethiopia (36 species) (Girma and Mosandl 2012) and a mopane woodland in northern Botswana (35 species) (Teketay et al 2018). However, it was lower than tropical forests (55 species) of Kenya (Mutiso et al 2015).…”

Diversity, stand structure and regeneration status of woody species, and spatial cover of herbaceous species in Mokolodi Nature Reserve, Southeastern Botswana

“…When all the species (woody species and herbaceous species) are considered, the species composition in MNR is lower than those reported from Ethiopia (Senbeta and Teketay, 2003;Zegeye et al, 2006). The diversity and evenness values of the woody species in MNR (1.44 an 0.38, respectively) are much lower than those reported for Shorobe (2.18 and 0.6, respectively), Maun (area exclosure in Island Safari Lodge, 2.15 and 0.6, respectively), Xobe (1.5 and 0.5, respectively) villages (Neelo et al, 2013;Neelo et al, 2015) as well as in an area exclosure of more than 10 years (3.14 and 1.6, respectively) in Maun (Teketay et al, 2016), northern Botswana, and other dry land forests (Senbeta and Teketay, 2003;Alelign et al, 2007;Zegeye et al, 2006).…”

“…The species, family and genera richness values of woody species (44 spp., 17 families and 26 genera) recorded in this study were higher than those reported from studies in Shorobe (41 spp., 15 families and 23 genera), Maun (area exclosure in Island Safari Lodge, 33 spp., 13 families and 20 genera) and Xobe (27 spp., 10 families and 24 genera) villages (Neelo et al, 2013;Neelo et al, 2015) as well as in an area exclosure of more than 10 years (32 spp., 12 familes and 19 genera) and open area adjacent the area exclosure (24 spp., 10 familes and 15 genera) in Maun (Teketay et al, 2016) in northern Botswana, and in Shekole (18 spp.) and Guba (23 spp.)…”

Vegetation survey of the woodlands of Huíla Province

“…A threshold of H' = 2 has been mentioned as the minimum value above which an ecosystem can be regarded as medium to high diversity . The mean Shannon diversity index found in the Mopane woodlands of the study area was relatively low compared to similar habitats in northern Botswana; this is attributed to anthropogenic disturbance, suggesting that non-protected woodlands are negatively impacted by human activity, with a direct eff ect on the composition and diversity of species (Teketay et al, 2018). Within the study area we found H' values below 1; this may not only be related to the minimum number of plots surveyed, but also to the monodominance of single tree species such as Baikiaea plurijuga-Baphia massaiensisTerminalia sericea.…”