Patch area and current coffee management determine woody plant diversity in patches of semi-forest coffee embedded in an agricultural matrix

AbstractEffective conservation of biodiversity in patches of (semi-) natural vegetation is dependent on an understanding of the influence of management as well as spatial and temporal factors. In southwestern Ethiopia coffee generally grown under a rather dense layer of indigenous trees (so called semi-forest coffee - SFC) often in patches embedded in an open agricultural landscape. The aim of the study was to disentangle what governs the variation in species richness of woody species among such patches. We collected data on species and possible explanatory factors in 40~×~40 m plots centered in 40 SFC patches, measured the patch area for 1987 and 2013, and the amount of surrounding SFC-area for each patch. We recorded the number of coffee stems and the level of disturbance caused by slashing of the understory vegetation. Species richness of large coffee shade trees (>20 cm in diameter) was higher in larger patches with even slightly better fit of the statistical models when the historical area was taken into account. However, most species of large trees also occurred as seedlings showing that there is still a potential to conserve these species in the patches. Coffee management negatively affected the richness and density of woody species, especially in the intermediate size class (1.6–20~cm diameter). Disturbances accompanying coffee management such as slashing of the ground vegetation also negatively affected tree seedling density as well as species richness. There was no effect of connectivity on species richness. Based on the combination of these results we conclude that small patches of semi-forest coffee had fewer species of large trees, not because of a lack of tree seedlings, but probably because of differentiated local extinctions, perhaps during the time when the species were intermediate sized. To maintain the species richness of large trees in semi-forest coffee patches, the sites need to be actively managed

Structurally complex farms support high avian functional diversity in tropical montane Ethiopia

Of all feeding guilds, understorey insectivores are thought to be most sensitive to disturbance and forest conversion. We compared the composition of bird feeding guilds in tropical forest fragments with adjacent agro-ecosystems in a montane region of south-west Ethiopia. We used a series of point counts to survey birds in 19 agriculture and 19 forest sites and recorded tree species within each farm across an area of 40 × 35 km. Insectivores (~17 spp. per plot), frugivores (~3 spp. per plot) and omnivores (~5 spp. per plot) maintained species density across habitats, while granivores and nectarivores increased in the agricultural sites by factors of 7 and 3 respectively. Species accumulation curves of each guild were equal or steeper in agriculture, suggesting that agricultural and forest landscapes were equally heterogeneous for all bird guilds. Counter to most published studies, we found no decline in insectivore species richness with forest conversion. However, species composition differed between the two habitats, with certain forest specialists replaced by other species within each feeding guild. We suggest that the lack of difference in insectivorous species numbers between forest and agriculture in this region is due to the benign nature of the agricultural habitat, but also due to a regional species pool which contains many bird species which are adapted to open habitats

Vicariance, dispersal, and hybridization in a naturally fragmented system: the afro-alpine endemics Carex monostachya and C. runssoroensis (Cyperaceae)

Published version available at https://doi.org/10.1007/s00035-015-0162-2. The naturally fragmented habitat on the tallest African mountains provides a good model system to study vicariance, dispersal, and hybridization. Many mountains are separated by lowland that likely was unsuitable for high-alpine plants even during cold climatic periods. We explore the relative importance of these processes using two endemic sister species: the widespread Ethiopian/eastern East African Carex monostachya and the mainly western East African C. runssoroensis. These bog-forming sedges co-occur in some mountains and are hypothesized to hybridize. The two species were distinctly differentiated for genome-wide Amplified Fragment Length Polymorphisms (AFLPs), also in one mountain where they co-occur. However, the plants from another mountain showed strong signals of admixture. The results suggest initial divergence into one western and one northern/eastern lineage, followed by long-distance dispersal resulting in secondary contact zones. Also within species genetic diversity was clearly structured with distinct genetic groups on some, but not all mountains. Differentiation levels varied considerably and did not always correspond to the extent of lowland habitat between mountains. The narrow Rift Valley in the otherwise nearly contiguous highlands in Ethiopia appears to present a much stronger barrier to dispersal than the extensive lowlands separating Ethiopia from East Africa. This may be a general pattern since it has been documented also for other afro-alpine specie

Multi-scale mosaics in top-down pest control by ants from natural coffee forests to plantations

While top-down control plays an important role in shaping both natural and agricultural food webs, we lack insights into how top-down control effects vary across spatial scales. We used a multi-scale survey of top-down control of coffee pests and diseases by arboreal ants to examine if colony location creates a small-scale mosaic in top-down control around trees and if the strength of that control varies between sites at the landscape scale. We investigated pest and disease levels on coffee shrubs at different distances from shade trees with and without a Crematogaster spp. ant colony in 59 sites along a coffee management intensity gradient in southwestern Ethiopia. Within sites, ants significantly suppressed herbivory and coffee leaf rust at distances less than 10 m from nesting trees. Top-down control varied between sites, with stronger top-down control of free-feeding herbivory near ant colonies at sites with lower management intensity and stronger top-down control of a skeletonizer at sites with higher canopy cover. We conclude that the strength of top-down control by ants is highly heterogeneous across spatial scales, as a consequence of the biology of the predator at the small scale and herbivore density or changes in herbivore-ant interactions at the landscape scale

Data from: Waiving the extinction debt: can shade from coffee prevent extinctions of epiphytic plants from isolated trees?

Aim: Local extinction after habitat modifications is often delayed, leading to an extinction debt. Our first aim was to develop a conceptual model for natural and human-mediated habitat improvements after a disturbance that may waive part of the predicted extinction debt. Second, we wanted to test this model on the distribution of epiphytic plants on trees that had been isolated in the agricultural matrix after forest clearing, around which coffee subsequently had been planted with a possible improvement of the microclimate. Location: Bonga, Southern Nations, Nationalities and Peoples Region (SNNPR), Ethiopia. Methods: We studied 50 trees that had been isolated for periods ranging from a few years to half a century after clearing. The trees were now located in the agricultural landscape at different distances from intact Afromontane forests. Fourteen trees in the forests were used as references. Each tree was inventoried for all vascular epiphytic plants, mosses and liverworts. Results: Time since clearance had a direct negative effect on number of forest specialist species via delayed extinctions and the detected large extinction debt of both bryophytes and vascular plants continued to be paid over several decades. However, time since clearance had an indirect positive effect on number of forest indicator species via the reappearance of shade from coffee planted surrounding the trees, even if the waiving effect on the extinction debt was rather small. Additionally, trees at further distances from the forest edge had fewer forest-associated species. Main conclusions: Our results show that the ability of agroecological landscapes to foster forest biodiversity may be overestimated if meta-community processes over time and space are not taken into account. However, the possibility of initiating counteracting processes that modify the level of expected local extinctions should be evaluated more often to find ways of improving conditions for biodiversity in human-modified landscapes

Data_Hylander_Nemomissa

Environmental data and species occurrence data from all sites. See the ReadMe file for more explanations

The mating system of Sesbania sesban (L.) Merr. (Leguminosae)

The mating system of Sesbania sesban was studied using one natural population and two cultivated populations. A large number of progeny (600) was assayed from each population for one polymorphic locus of Malate dehydrogenase (Mdh). The level of out-crossing in the studied populations ranged from 40–100%. The genotype frequencies were in agreement with those of the Hardy-Weinberg expected genotype proportions as in randomly mating populations at P < 0.05. The floral structure and the pollen shedding behaviour of the flowers of S. sesban could favour cross-pollination and/or self-pollination depending on the circumstances. Self-pollination usually occurs late in the flowering period when pollinators fail to visit the flowers. Such a “delayed selfing” facilitates out-crossing in the presence of appropriate pollinators under natural conditions, but confers a selective advantage where pollinators are limiting. The results indicated that S. sesban could be self-fertilized in the absence of pollinators or could out-cross with other heterozygous individuals in the neighboring population when suitable pollinators are available. S. sesban exhibits “facultative xenogamy” or “delayed selfing” and is a mixed mating species. Key words/phrases: Allozymes, delayed selfing, Hardy-Weinberg equilib rium, malate dehydrogenase, mixed mating system SINET: Ethiopian Journal of Science Vol.25(2) 2002: 177-19

Impact of land use type on soil seed bank flora in Chilimo Forest, Ethiopia: Implications for natural restoration of vegetation

A very long history of human interference and pressure from population growth has imparted different land use types in the Chilimo forest: shrub land, closed forest, Cupressus lusitanica plantation, Eucalyptus plantation, Juniperus procera dominated stand, Olea europaea subsp. cuspidata dominated stand, open forest, Podocarpus falcatus dominated stand, abandoned arable land, and grassland. A total of 100 plots (each 20 m x 20 m) were used in ten habitat types (10 plots in each) for the collection of data on the soil seed bank and standing vegetation. Soil  samples were collected from within small quadrats (15 cm x 15 cm) from four successive soil layers. A total of 105 plant species were identified from the soil seed bank with total densities ranging between 4991 and 11017 seeds/m2. Of the total recorded species in the soil seed bank, herbaceous species were represented with the largest number (87.6%) whereas the contribution of woody species was low (11.4%). The highest number of species was recorded from the closed canopy stand while the highest density of seeds was found in the arable land. The overall vertical distribution of seeds showed the highest densities occurring in the upper 3 cm soil depth and gradually decreasing with increasing depth, except in the arable land. There was a significant difference among the habitat types in the density of soil seed bank suggesting different types, level and frequency of disturbance on different habitat types. The very low similarity between the soil seed bank and aboveground flora is reflective of both the current and past standing vegetation.Key words/phrases: Afromontane, Forest degradation, Restoration, Soil seed bank, Species diversity