Local and landscape-level effects on Ethiopian church forest biodiversity and implications for forest ecosystem services

Ethiopië wordt gekenmerkt door een zeer sterke mate van bosversnippering, waarbij bossen nog vrijwel uitsluitend worden aangetroffen als kleine en geïsoleerde fragmenten rond kerken. Een beter begrip van de ecologische integriteit en veerkracht van kerkbossen, en de landschapsmatrix waarin ze gelegen zijn, is dus van groot belang voor het natuurbehoud. In dit kader onderzochten wij eerst de diversiteit, structuur en regeneratiestatus van bosfragmenten in het zuidoosten van het Tanameer. Wij registreerden 115 boomsoorten waarvan de meeste een onregelmatig verspreidingspatroon en beperkte mate van regeneratie vertoonden. Vervolgens bestudeerden we factoren op lokaal- en landschapsniveau die de diversiteit en structuur van deze bosgemeenschappen verklaren. Kerkbossen met meer vergelijkbare kenmerken op lokaal niveau vertoonden daarbij een grotere overeenkomst in vegetatiesamenstelling, terwijl effecten op landschapsniveau minder duidelijk waren. Vijf boomsoorten dreigen momenteel volledig uit de regio te verdwijnen. Daarnaast vergeleken we de ecosysteemdiensten van kerkbossen en omliggende landschapsmatrix en onderzochten we het belang van kerkbossen voor de diversiteit van 131 voorkomende vogelsoorten. De gevonden verbanden tussen lokale- en landschapskenmerken, boskarakteristieken, ecossysteemdiensten en gevoeligheid van vogelsoorten op bosverstoring zullen hopelijk leiden tot een betere bescherming van de Ethiopische kerkbossen en hun unieke biodiversiteit

Woody vegetation composition and structure of church forests in southeast of Lake Tana, Northwest Ethiopia

Understanding woody plant species composition and structure is fundamental to design and optimize the needed conservation measures for Ethiopian church forests. The aim of this study was to describe the composition, structure, and regeneration status of woody species in church forests in southeast of Lake Tana, Ethiopia. Data were collected from twenty-four church forests. Four plots (20 m × 20 m) were established in each church forest. Plots were located in four cardinal directions (north, east, west, and south) at different distances from the forest center. Four subplots (5 m × 5 m) were established in each plot to assess seedlings and canopy cover. In each plot, all woody plants were identified and counted, and diameter at breast height (DBH) was measured. Species and family importance values were computed to characterize the species composition. Additionally, population structural features were analyzed through the variation of tree size classes. Species richness (SR), Pilou evenness (Jʹ), and Shannon–Wiener index (Hʹ) were used to determine species diversity. A total of 115 woody species representing 53 families and 97 genera were found. Of these, 62% were trees, 36% shrubs, 1.89% climber, and 0.06% reed species. Species richness differed among forests, ranging between 16 and 38 species. Fabaceae, Sapotaceae, and Rubiaceae were the dominant families with a high family importance values of 41, 28, and 22, respectively. The church forests have relatively high indices of species diversity (SR = 26 ± 1.25), (Jʹ = 0.75 ± 0.02), and (Hʹ = 2.42 ± 0.07), indicating that they play a major role in the conservation of woody species. However, a relatively high densities of Eucalyptus spp. ranging from 13 to 1925 individuals ha−1 were recorded, and these exotic tree species, thus, form a potential threat to the conservation of native species. The diameter class distribution of some selected keystone and dominant species formed four main shape types, of which the irregular-shaped pattern was most predominant, which suggests missing cohorts and regeneration problems for most species. Higher densities of Eucalyptus plantations were recorded in more recently established than old church forests. Therefore, effective measures should be taken to address the major pressures, such as plantation of exotic species that negatively affect the species composition and vegetation structure of these church forests, which, in turn, affect their ecosystem functions and services