Composition and size class structure of tree species in Ihang’ana forest reserve, Mufindi district, Tanzania

Ihang’ana Forest Reserve is part of the Udzungwa Mountains ecosystem that falls under the Eastern Arc Mountains (EAM). Previous plant biodiversity studies in this ecosystem concentrated on large-sized Forest Reserves of greater than 20,000 ha (FR) such as the Uzungwa Scarp ignoring small-sized forests of less than 300 hectares. This study was therefore undertaken to assess tree species composition, structure and diversity in Ihang’ana FR (2982 ha), one of the forest reserves in the Udzungwa Mountains Ecosystem. A total of 7 transects with 12 plots of sizes 20m x 50m each were established for vegetation sampling. Seventytree species representing 32 families and a total of 6478 individuals were identified from Ihang’ana FR. Alpha diversity ranged between 1.334 and 2.865 (mean 2.246 ± 0.309) with most plots recording species diversity of greater than 2.014. The most frequent occurring species were Aphloia theiformis (96.4%), Diospyros whyteana (91.6%), Nuxia floribunda (91.6%) Olea europaea (86.9%) and Macaranga capensis var. capensis (77.4%). Majority of these species similarly scored the highest Importance Value Index (IVI) as follows: Aphloia theiformis (112.6), Nuxia floribunda (111.36), Olea europaea (101.75), Bridelia micrantha (101.25), Diospyros whyteana (98.06), Macaranga capensis var. capensis (87.62), Morella salicifolia (71.3). M. capensis var. capensis, an indicator species for disturbance, was poorly represented in the lower DBH size classes, possibly an indication of forest recovery from past disturbance. Despite reports that licensed timber extraction used to take place in the forest in the early 1980’s the situation on the ground as observed during this study shows that the forest has recovered from such disturbance. It is therefore recommended that the central government continue supporting the local communities around the forest reserve for example in maintaining fire lanes as part of conservation and management of Ihang’ana forest Reserve.Keywords: Eastern Arc Mountains, Ihang’ana Forest Reserve, IVI, tree species composition, tree species diversity, Udzungwa Mountain

Investigating the Direct and Indirect Effects of Forest Fragmentation on Plant Functional Diversity

Ongoing habitat loss and fragmentation alter the functional diversity of forests. Generalising the magnitude of change in functional diversity of fragmented landscapes and its drivers is challenging because of the multiple scales at which landscape fragmentation takes place. Here we propose a multi-scale approach to determine whether fragmentation processes at the local and landscape scales are reducing functional diversity of trees in the East Usambara Mountains, Tanzania. We employ a structural equation modelling approach using five key plant traits (seed length, dispersal mode, shade tolerance, maximum tree height, and wood density) to better understand the functional responses of trees to fragmentation at multiple scales. Our results suggest both direct and indirect effects of forest fragmentation on tree functional richness, evenness and divergence. A reduction in fragment area appears to exacerbate the negative effects resulting from an increased amount of edge habitat and loss of shape complexity, further reducing richness and evenness of traits related to resource acquisition and favouring tree species with fast growth. As anthropogenic disturbances affect forests around the world, we advocate to include the direct and indirect effects of forest fragmentation processes to gain a better understanding of shifts in functional diversity that can inform future management efforts

A new species in the tree genus Polyceratocarpus (Annonaceae) from the Udzungwa Mountains of Tanzania

Polyceratocarpus askhambryan-iringae, an endemic tree species of Annonaceae from the Udzungwa Mountains of Tanzania, is described and illustrated. The new species is identified as a member of the genus Polyceratocarpus by the combination of staminate and bisexual flowers, axillary inflorescences, subequal outer and inner petals, and multi-seeded monocarps with pitted seeds. From Polyceratocarpus scheffleri, with which it has previously been confused, it differs in the longer pedicels, smaller and thinner petals, shorter bracts, and by generally smaller, less curved monocarps that have a clear stipe and usually have fewer seeds. Because Polyceratocarpus askhambryan-iringae has a restricted extent of occurrence, area of occupancy, and ongoing degradation of its forest habitat, we recommend classification of it as Endangered (EN) on the IUCN Red List

Annual cycles are the most common reproductive strategy in African tropical tree communities

Abstract We present the first cross‐continental comparison of the flowering and fruiting phenology of tropical forests across Africa. Flowering events of 5446 trees from 196 species across 12 sites and fruiting events of 4595 trees from 191 species across 11 sites were monitored over periods of 6 to 29 years and analyzed to describe phenology at the continental level. To study phenology, we used Fourier analysis to identify the dominant cycles of flowering and fruiting for each individual tree and we identified the time of year African trees bloom and bear fruit and their relationship to local seasonality. Reproductive strategies were diverse, and no single regular cycle was found in >50% of individuals across all 12 sites. Additionally, we found annual flowering and fruiting cycles to be the most common. Sub‐annual cycles were the next most common for flowering, whereas supra‐annual patterns were the next most common for fruiting. We also identify variation in different subsets of species, with species exhibiting mainly annual cycles most common in West and West Central African tropical forests, while more species at sites in East Central and East African forests showed cycles ranging from sub‐annual to supra‐annual. Despite many trees showing strong seasonality, at most sites some flowering and fruiting occurred all year round. Environmental factors with annual cycles are likely to be important drivers of seasonal periodicity in trees across Africa, but proximate triggers are unlikely to be constant across the continent.Additional co-authors: Roman M. Wittig, Thomas Breuer, Mireille Breuer‐Ndoundou Hockemba, Crickette M. Sanz, David B. Morgan, Anne E. Pusey, Badru Mugerwa, Baraka Gilagiza, Caroline Tutin, Corneille E. N. Ewango, Douglas Sheil, Edmond Dimoto, Fidèle Baya, Flort Bujo, Fredrick Ssali, Jean‐Thoussaint Dikangadissi, Kim Valenta, Michel Masozera, Michael L. Wilson, Robert Bitariho, Sydney T. Ndolo Ebika, Sylvie Gourlet‐Fleury, Felix Mulindahabi, Colin M. Beal

Annual cycles are the most common reproductive strategy in African tropical tree communities

We present the first cross continental comparison of the flowering and fruiting phenology of tropical forests across Africa. Flowering events of 5,446 trees from 196 species across 12 sites, and fruiting events of 4,595 trees from 191 species, across 11 sites were monitored over periods of 6 to 29 years, and analysed to describe phenology at the continental level. To study phenology we used Fourier analysis to identify the dominant cycles of flowering and fruiting for each individual tree and we identified the time of year African trees bloom and bear fruit and their relationship to local seasonality. Reproductive strategies were diverse and no single regular cycle was found in >50% of individuals across all 12 sites. Additionally, we found annual flowering and fruiting cycles to be the most common. Sub-annual cycles were the next most common for flowering whereas supra-annual patterns were the next most common for fruiting. We also identify variation in different subsets of species, with species exhibiting mainly annual cycles most common in West and West-Central African tropical forests, while more species at sites in East-Central and Eastern African forests showed cycles ranging from sub-annual to supra-annual. Despite many trees showing strong seasonality, at most sites some flowering and fruiting occurred all year round. Environmental factors with annual cycles are likely to be important drivers of seasonal periodicity in trees across Africa, but proximate triggers are unlikely to be constant across the continen

A preliminary account of the forest avifauna of Ihang’ana and Idewa Forest Reserves: ‘forest islands’ on the Udzungwa Plateau, Tanzania

This study reports on the forest avifaunas of Ihang’ana and Idewa Forest Reserves, located on the Udzungwa Plateau, Tanzania, which are undocumented in published literature. Field surveys were conducted between 28 October and 6 November 2020 using the McKinnon species list method. From 185 McKinnon 10-species lists, 40 species were observed in Ihang’ana and 30 in Idewa Forest Reserves, for a combined total of 41 species. Of the species recorded, over 78% (32 species) were forest-dependent birds representative of Eastern Arc Mountains forests. Seven species detected are considered restricted-range species, including Yellow-throated Greenbul Arizelocichla chlorigula, which is endemic to the Eastern Arc Mountains of Tanzania. The results suggest that forest birds, including montane species, can survive in isolated areas of suitable habitat even when patch size is small. As such, forests such as Ihang’ana and Idewa forests can still play an important role in the conservation of forest birds

Seasonal use of remnant forest fragments by understorey forest birds in the Uluguru Mountains, Tanzania: a conservation priority

Forest fragmentation can lead to extinctions of some species at local levels and is eroding bird diversity at an increasing rate. While there is information on the distribution of forest bird species in most of the Eastern Arc Mountain forests, some forests, particularly the smaller fragments, have not been adequately surveyed. Using mist netting we surveyed avifauna in some of the poorly known forests (12.5–25 ha) located 320–1 300 m above sea level in the Uluguru Mountains in order to address their conservation importance. Proportions of seasonal altitudinal migrants were significantly higher in these lower-altitude forests during the cold season than the hot season. The results suggest that these forests support bird species of conservation concern, most of which are forest dependent and some of which make seasonal movements between high-altitude montane forests and lowland/ foothill forests. These forests are important cold-season habitat of altitudinal migrants and further fragmentation should be halted as a matter of regional and global priority.Keywords: altitudinal gradient, altitudinal migration, bird distribution, conservation, fragmentation, mist-nettin

The relationship between the abundance of non-native tree species and the community structure of resident woody species in tropical montane forest of West Usambara Mountains, Tanzania

Non-native tree species are globally claimed as liable to the encroachment of natural forests in their proximity resulting to the loss of biodiversity. This study was conducted in Magamba Nature Forest Reserve (MNFR) in West Usambara Mountains of Tanzania. A total of 96 (20 m x 20 m) plots were established to record all woody plants with Diameter at Breast Height (DBH) ≥ 5 cm while two nested plots of 2 m x 5 m were set to measure any plant with DBH ≥ 1 cm but less than 5 cm. Furthermore, two nested plots of 1 m x 1 m were established within the bigger plot in order to assess and record seedlings (DBH 0.05) association when assessed against the total abundance, species diversity, richness and evenness of all the resident woody species. This non-significant result may not necessarily mean no effect. This is because the P-value does not explain the size of the effect in biological data. Further analysis revealed that, the biomass of resident species was negatively related to the abundance of non-native species A. melanoxylon (p = 0.003) and E. grandis (p = 0.038). The negative relationship between the abundance, richness, diversity, evenness, and biomass of the resident woody species and the abundance of non-native species portrayed in this study raise an alarm. Therefore, there is need for setting monitoring and control mechanism to stop further spread of the non-native tree species in MNFR and hence, save the remaining biodiversity of the area

Back to Africa: monitoring post-hydropower restoration to facilitate reintroduction of an extinct-in-the-wild amphibian

Monitoring of the ecological efficiency of different restoration and mitigation measures is important to inform decision-making but can be challenging, especially in remote and low-resource settings. Species composition of the vegetation is sensitive to environmental variation, and can thus be used in restoration assessment, but this requires statistical approaches that can accommodate multivariate responses. We use principal response curves (PRC) to assess the efficiency of post-hydropower mitigation measures installed to secure the reintroduction of an extinct-in-the-wild amphibian back into its only native habitat. The endemic ovoviviparous Kihansi spray toad Nectophrynoides asperginis is only known from a wetland in the Lower Kihansi River Gorge in the Eastern Arc Mountains in Tanzania. River flow was diverted from the gorge for hydropower production in 1999, causing the spray wetland to desiccate, consequently threatening the toad and other plant and animal species dependent on the spray-zone habitat. To mitigate the toad population collapse, a sprinkler system was installed over a limited section of the original spray-zone wetlands to mimic the waterfall spray and toads were taken to the USA for ex situ breeding. The decline, extinction, ex situ breeding, and planned reintroduction of the species has driven substantial research on Kihansi spray toad biology. In contrast, the efficiency of the mitigation measures in restoring the spray-zone wetland habitat required for its successful reintroduction has not been formally evaluated. Here, we analyze re-sampled vegetation data from the spray-zone wetland over a period of eight years by means of principal response curves to investigate if the post-hydropower mitigation measures have successfully restored the pre-hydropower ecosystem. The results show that the spray-zone vegetation is recovering. The wetland flora and especially species important to the Kihansi spray toad have increased and the restored ecosystem has stabilized, favoring the reintroduction of the Kihansi spray toad to its native habitat. However, the wetland ecosystem is not restored entirely and continued mitigation measures are needed. Continued monitoring is essential to support evidence-based restoration, and we conclude that assessment based on vegetation monitoring coupled with principal response curve analyses provides a cost-effective and efficient monitoring tool for such projects. Read More: http://www.esajournals.org/doi/abs/10.1890/ES14-00093.