Vegetation composition, diversity, stand structure and carbon stock of a dry evergreen montane forest of Lendikinya forest reserve in Tanzania

Abstract

Abstract. Mwaluseke ML, Mwakalukwa EE, Maliondo SMS. 2023. Vegetation composition, diversity, stand structure and carbon stock of a dry evergreen montane forest of Lendikinya forest reserve in Tanzania. Biodiversitas 24: 551-562. There is limited information on woody plant diversity and vegetation patterns in African dry forests, particularly in East Africa, and hence increasing the interests in understanding species composition, diversity, and structural attributes of catchment forest reserves found in Tanzania. Moreover, tree species composition, species richness, and carbon stock are not well documented in most montane forests in the region, apart from Ethiopia. Their potential in terms of carbon storage is also important for understanding their productivity and the extent to which they can be used in mitigating the effects of climate change. This study assessed vegetation composition and diversity, stand structure and potential carbon stocks of Lendikinya Forest Reserve, a dry evergreen montane forest located in Monduli District in Tanzania. A total of 56 concentric circular plots with subplots of 2 m, 5 m, 10 m, 15 m and 20 m radii were used to collect woody species data on standing trees and stumps across the entire forest of 3,689 ha. A total of 79 species belonging to 36 families were identified. Drypetes natalensis (9.2%), Diospyros abyssinica (7.1%) and Dombeya rotundifolia (6.5%) were the most important species as per the Importance Value Index (IVI). The diversity indices have indicated the forest reserve to have a high diversity of woody species. Stand structure comprises 1,398 ± 679 stems ha-1, basal area of 11.42 ± 5.41 m2ha-1and standing volume of 54.47 ± 24.1 m3ha-1 while the mean carbon stocks were 16.04 ± 7.7 t C ha-1. The alarming disturbances stress the urgent need for increased conservation efforts in order to protect the existing biodiversity and increase carbon storage and enhance water conservation in the reserve.

Woody species diversity, composition, structure and carbon storage of a dry evergreen montane forest of Essimingor Nature Forest Reserve in Tanzania

“…The mean above-ground biomass and potential carbon stocks of the forest reserve for trees and shrubs with diameter ≥5cm were 116.19±70.61 Mg ha -1 and 56.93±34.60 Mg C ha -1 respectively, while the mean below-ground biomass and potential carbon stocks of the forest reserve for trees and shrubs with diameter ≥5cm were 70.84±40.24 Mg ha -1 and 34.71±19.72 Mg C ha -1 , respectively (Table 1, Figure 6). Tree species which had high contribution to the observed above-ground carbon density were C. malosana (11.74±3.85 Mg C ha -1 ), D. natalensis (10.12±4.60 Mg C ha -1 ), D. abyssinica (6.50±2.73 Mg C ha In contrast, the total mean aboveground carbon stocks found in this study is higher than that reported by Mwaluseke (2015) from a dry evergreen forest of Lendikinya Forest Reserve in Tanzania who reported a value of 16.04±7.7 t C ha -1 ; Biadgligne et al (2022) reported two values of 14.84±1.27 t C ha -1 and 3.49±0.66 t C ha -1 from two community forests from Ethiopia; Solomon et al (2017) The high value reported by several authors could be due to differences in climatic conditions of these sites in terms of rainfall received and the presence of many large trees which had significant contribution to the total mean carbon density than the presence of many small trees reported in this study (Mauya and Madundo 2021). According to Mauya and Madundo (2021) climate, topography as well as estimation methods particularly the selection of allometric models is also key factors when it comes to accurate estimation of AGB and AGC in the different study sites.…”

“…Siraj and Zhang (2018) recorded a total basal area of 454.52 m 2 •ha -1 from a dry Afromontane forest in Ethiopia. However, the mean basal area reported in this study is higher than 11.42±5.41 m 2 ha -1 reported by Mwaluseke (2015) from a dry evergreen forest of Lendikinya Forest Reserve in Tanzania.…”

“…The total mean volume of 27.3±16.3 m 3 ha -1 reported in this study for trees and shrubs with DBH ≥ 5 cm was considered lower than 40.03±11.21 m 3 ha -1 reported by Dugilo (2009) from Selela village forest reserve and a value of 54.47±24.1 m 3 ha -1 from a dry evergreen forest of Lendikinya Forest Reserve in Tanzania (Mwaluseke (2015) while Sitati et al (2016) reported a much higher value of 395.07±14 m 3 ha -1 from a dry evergreen forest of Ketumbeine Forest Reserve in Tanzania. However, the volume reported in this study is within the range of 16.7 to 92.17±39.0 m 3 ha -1 commonly reported in other forests including miombo woodland (Mwakalukwa et al 2014; and at least two recent reports e.g., Chamshama et al 2004 [76.1m 3 ha -1 ]; Maliondo et al 2005 [54.0 m 3 ha -1 ]; Sawe et al 2014 [32.6 m 3 ha -1 ]).…”

“…The values of the Shannon-Wiener index (H´= 2.70) for trees and shrubs in the present study are lower than those documented in other tropical forests. For instance, Sitati et al (2014) reported a H´ value of 2.848 from a dry evergreen forest of Gelai Forest Reserve in Tanzania; Mwaluseke (2015) reported a H´ value of 3.46 from a dry evergreen forest of Lendikinya Forest Reserve in Tanzania; Boz and Maryo (2020) from Ethiopia reported an average H´ value of 3.38; Kacholi et al (2015) found an overall H´ value of 4.03 from the Uluguru forests in Tanzania; and Tynsong et al (2022) reported a H´ values ranging from 3.74-3.95 (mean 3.85±0.06) from the tropical evergreen forests in India. However, H´ values in this study are much higher than those documented by Sitati et al (2016) from a dry evergreen forest of Ketumbeine Forest Reserve in Tanzania (H´ value of 2.3616); Kayombo et al (2022) reported a H´ value of >1.5 from Tanzania, Sutomo and van Etten (2023) reported H´ values ranging from 0.6-1.9 (mean 1.4) from seasonally dry tropical forest in Indonesia; Erenso et al (2014) reported H´ value of 1.79 and Dugilo (2009) reported H´ value of 1.298.…”

“…The isolated forest on top of a hill is part of broader distribution of dry evergreen montane forests surrounded by open savanna (forestsavanna mosaic) in Eastern Africa (Greenway 1973;White 1983). ENFR is among many forests found on small protruding and isolated hills in most parts of dry areas in Tanzania with high biodiversity values (Lovett and Pocs 1993;Sitati et al 2014;Sitati et al 2016;Kayombo et al 2022) and carbon storage potential (Swai et al 2014;Mwaluseke 2015) but is less studied. This information is important to aid the preparation of strategies for successful management of the forest reserve and planning for Ecotourism.…”