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The multifunctional role of shade trees for conservation of biodiversity and ecosystem services in natural forests and agroforests is well documented, yet we lack insights into the impact of shade tree species identity on pest and disease dynamics on agroforestry crops such as coffee and cacao, and its implications for management. We conducted two surveys on the impact of shade tree species identity and canopy cover on pests, diseases and a fungal hyperparasite on Arabica coffee in southwestern Ethiopia, which is one of the areas of origin of Arabica coffee. One survey was in a commercial plantation, and the other along a management gradient from only little managed coffee growing in the natural forest to intensively managed commercial plantations. To link these findings to current shade tree selection criteria, we complemented these surveys by interviews with farmers and managers. Shade tree species identity left a weak imprint on insect pest levels, and insect pests levels differed strongly in the strength and direction of their response to canopy cover. In contrast to the insect pests, the incidence of coffee leaf rust and its hyperparasite, as well as coffee berry disease, differed among shade tree species, with particularly high levels of coffee leaf rust and the hyperparasite underneath the canopy of the shade trees Acacia abyssinica and Croton macrostachyus, and coffee berry disease underneath the canopy of Acacia abyssinica and Polyscias fulva. Smallholder farmers used many criteria for selecting shade trees, such as leaf traits and competition for soil moisture, but low priority is given to the effect of shade tree species identity on pests and diseases. Our findings help to understand spatial variation in pest and disease dynamics in natural forests and agroforests, and may inform the selection of shade tree species by coffee producers and thereby contribute to ecologically-informed pest and disease management. Importantly, our finding highlight the potent

Tropical agroforestry systems provide farmers with resources for their livelihoods, but are also well-recognized as refuges for biodiversity. However, the relationship between yield and biodiversity might be negative in these systems, reflecting a potential trade-off between managing for increased yield or biodiversity. The potential for synergies will depend partly on the shape of the biodiversity–yield relationship, where a concave relationship suggests a faster decline in biodiversity with increasing yields than a linear or convex shape. We studied the relationship between biodiversity (plant species richness and composition) and coffee yield along a gradient of management in south-western Ethiopia, coffee's native range. We inventoried species richness and community compoasition of woody plants, herbaceous plants and bryophytes at 60 sites. We also measured coffee management-related variables and assessed coffee yield for 3 consecutive years at each site. Species richness of woody plants had a concave relationship with coffee yield, that is, tree richness declined fast initially before levelling out at higher yields, whereas there was no relationship between coffee yield and species richness of herbaceous plants or bryophytes. Species composition of woody plants, herbaceous plants and bryophytes all had a concave relationship with coffee yield. From a methodological perspective, we found that multi-year data on yield were necessary to reliably assess the relationship between biodiversity and yield, and that the number of coffee shrubs or coffee dominance were poor proxies for yield when trying to capture the biodiversity–yield relationship. Synthesis and applications. The concave relationship between biodiversity components (species richness and composition) and yield suggests that there is a strong conflict between the goals of increasing production and conserving biodiversity. However, it is important to recognize that this pattern is largely driven by the ver

Low-altitude lakes in eastern Africa have long been investigated and have provided valuable information about the Late Quaternary paleohydrological evolution, such as the African Humid Period. However, records often suffer from poor age control, resolution, and/or ambiguous proxy interpretation, and only little focus has been put on high-altitude regions despite their sensitivity to global, regional, and local climate change phenomena. Here we report on Last Glacial environmental fluctuations at about 4000 m asl on the Sanetti Plateau in the Bale Mountains (SE Ethiopia), based on biogeochemical and palynological analyses of laminated lacustrine sediments. After deglaciation at about 18 cal kyr BP, a steppe-like herb-rich grassland with maximum Chenopodiaceae/Amaranthaceae and Plantago existed. Between 16.6 and 15.7 cal kyr BP, conditions were dry with a desiccation layer at ~ 16.3 cal kyr BP, documenting a temporary phase of maximum aridity on the plateau. While that local event lasted for only a few decades, concentrations of various elements (e.g. Zr, HF, Nb, Nd, and Na) started to increase and reached a maximum at ~ 15.8–15.7 cal kyr BP. We interpret those elements to reflect allochthonous, aeolian dust input via dry northerly winds and increasingly arid conditions in the lowlands. We suggest an abrupt versus delayed response at high and low altitudes, respectively, in response to Northern Hemispheric cooling events (the Heinrich Event 1). The delayed response at low altitudes might be caused by slow negative vegetation and monsoon feedbacks that make the ecosystem somewhat resilient. At ~ 15.7 cal kyr BP, our record shows an abrupt onset of the African Humid Period, almost 1000 years before the onset of the Bølling–Allerød warming in the North-Atlantic region, and about 300 years earlier than in the Lake Tana region. Erica pollen increased significantly between 14.4 and 13.6 cal kyr BP in agreement with periodically wet and regionally warm conditions. Similarly

Questions In some fire-prone ecosystems, bryophytes play a crucial role by providing the surface fuel that controls the fire return interval. Afroalpine heathlands are such an ecosystem, yet almost nothing is known about the bryophytes in this system. We do not know the level of species richness, or if there is a successive accumulation of species over time, or if some species are adapted to specific phases along the successional gradient, for example early-successional species sensitive to competition. Location Afroalpine heathlands in Ethiopia. Methods We made an inventory of all bryophytes in 48 plots of 5 m x 5 m, distributed along a chronosequence from 1 to 25 years post fire. The heathlands are located between 3500 m and 3800 m a.s.l. and are managed by traditional pasture burning with fire intervals of 8-20 years. Results We found in total 111 taxa of bryophytes. Post-fire mortality was almost 100%. The youngest plots had only a few cosmopolitan species often found after fire. Initially, species richness increased monotonically while starting to level off around 15 years after fire, when many plots had around 30 species and a high cover of Breutelia diffracta, which is a key ground-living species, important as surface fuel. Most species were found with sporophytes, a pattern even stronger for the most frequent species. Conclusions Interestingly, bryophyte diversity is already remarkably high by only 15 years after total eradication. The relatively slow accumulation of species in the first years after fire suggests that dispersal in space, and not time, is the major mechanism by which sites regain their diversity (i.e. spore banks play a smaller role than colonization of wind-borne spores). This indicates that the high species richness is built up through colonization from surrounding heathlands, and perhaps also from higher-altitude alpine grasslands and lower-altitude forests, and that the bryophyte diversity in this system is maintained by the traditional f

With the current deforestation rates in tropical ecosystems, optimizing biodiversity in managed systems has become fundamental for conservation. Agroforestry has been suggested to conserve biodiversity and buffer deforestation rates, while also sustaining local livelihoods. While many studies have focused on the relation between local management intensity and biodiversity, processes at the landscape scale are often overlooked and remain a knowledge gap. In this study we identified drivers behind woody plant regeneration in coffee agroforestry on both local and landscape scale. We used univariate-, multivariate- and structural equation models to relate seedling species richness, diversity, density, community composition and height to local management intensity and location in the landscape of 60 coffee agroforestry sites in southwestern Ethiopia. Local management intensity, which simplifies and reduces canopy cover, negatively impacted species richness, diversity and density, presumably due to altered microclimatic conditions and a reduction in local seed sources. Seedling height was also reduced by management intensity, including slashing frequency and canopy cover. On the landscape scale, species richness and diversity of seedlings was higher at sites adjacent to continuous forests where seed sources are abundant, and declined with distance to the forest. In particular, late successional species were negatively affected, whereas common shade tree species and pioneers occurred as seedlings throughout the landscape and in more managed systems. This suggests that dispersal limitation is detrimental for the regeneration of late successional species, especially in agroforestry systems where the standing woody plant diversity is largely reduced. Our results indicate that natural regeneration of woody plants still occurs in coffee agroforestry systems, primarily when the canopy structure is dense and diverse and/or when sites are located nearby continuous forests. Managem

Agroforestry systems can provide habitats for a rich biodiversity including multitrophic interactions, which presents opportunities to develop natural pest control. Shade coffee systems in several coffee growing areas of the world host such unique habitats where pests and their natural enemies interact. One of the major global challenges for coffee production, coffee leaf rust caused by the fungal pathogen Hemileia vastatrix is attacked by the fungal hyperparasite, Lecanicillium lecanii. However, we lack insights in the dynamics and biocontrol potential of the hyperparasite on coffee leaf rust from landscapes in Arabica coffee's native range. To understand the temporal dynamics across landscapes and environmental drivers of the rust and hyperparasite, and the potential for biocontrol of the rust by the hyperparasite, we studied the rust and hyperparasite during the dry and wet seasons for three consecutive years at 60 sites across a gradient of coffee management in southwestern Ethiopia. We found that coffee leaf rust was more severe during the dry season, whereas the hyperparasite was more severe during the wet season in two out of three years. The rust growth rate from the wet to the dry season transition was negatively related to the hyperparasite index during the wet season, implying a potential top-down control. Coffee leaf rust was generally more severe at lower altitudes in the dry season, whereas the hyperparasite was more severe at high altitude. The rust incidence increased with management intensity, while the hyperparasite was more common under less intensive management. This study could be interesting in that it represents a landscape where Arabica coffee originated and the rust and hyperparasite might have a long co-evolutionary history. Our findings highlight the potential of the hyperparasite to suppress the rust's growth rate from the wet to dry season transition when the rust severity could otherwise be at its peak. We show that less intensively man

Ethiopia aims to restore 15 million ha degraded forests and woodlands, but effects on the potentially contrasting goals of long-term carbon storage, biodiversity and sustainable livelihoods are unknown. To quantify the effects of grazing exclusion on vegetation and fire behaviour, we established six 30 x 30 m fenced exclosures with grazed controls, in a mesic wooded savanna. Experimental burns were done after 1.5 years. Tree seedlings were few but more common inside fences. Field layer cover and biomass increased inside fences, and grass species increased in numbers and cover. Fire intensity was higher inside fences, killing shrubs and saplings but not mature trees. Interviews confirmed that overgrazing has resulted in cool fires, causing shrub encroachment. High-intensity fires occurred in the 1980s after a zoonotic disease killed most livestock. Short-term increase in carbon storage through fire and grazing exclusion may lead to loss of pasture, and in the long-term increased wildfire risk.

Studies of early human settlement in alpine environments provide insights into human physiological, genetic, and cultural adaptation potentials. Although Late and even Middle Pleistocene human presence has been recently documented on the Tibetan Plateau, little is known regarding the nature and context of early persistent human settlement in high elevations. Here, we report the earliest evidence of a prehistoric high-altitude residential site. Located in Africa's largest alpine ecosystem, the repeated occupation of Fincha Habera rock shelter is dated to 47 to 31 thousand years ago. The available resources in cold and glaciated environments included the exploitation of an endemic rodent as a key food source, and this played a pivotal role in facilitating the occupation of this site by Late Pleistocene hunter-gatherers.

Species are often controlled by biotic factors such as competition at the warm edge of their distribution range. Disturbances at the treeline, disrupting competitive dominance, may thus enable alpine species to utilize lower altitudes. We searched for evidence for range expansion in grazed, fire-managed Ethiopian subalpine Erica heathlands across a 25-year chronosequence. We examined vascular plant composition in 48 plots (5x5m) across an altitudinal range of 3,465-3,711m.a.s.l. and analyzed how community composition changed in relation to increasing competition over time (using a Shade index based on Erica shrub height and cover) and altitude. Species habitats and altitudinal ranges were derived from literature. Time since fire explained more variation (r(2)=.41) in species composition than altitude did (r(2)=.32) in an NMDS analysis. Community-weighted altitudinal optima for species in a plot decreased strongly with increasing shade (GLM, Standardized Regression Coefficient SRC=-.41, p=.003), but increased only weakly with altitude (SRC=.26, p=.054). In other words, young stands were dominated by species with higher altitudinal optima than old stands. Forest species richness increased with Log Shade index (SRC=.12, p=.008), but was unaffected by altitude (SRC=-.07, p=.13). However, richness of alpine and heathland species was not highest in plots with lowest Shade index, but displayed a unimodal pattern with an initial increase, followed by a decrease when shading increased (altitude was not significant). Our results indicate that disturbance from the traditional patch burning increases the available habitat for less competitive high-altitude plants and prevents tree line ascent. Therefore, maintaining, but regulating, the traditional land use increases the Afro-alpine flora's resilience to global warming. However, this system is threatened by a new REDD+ program attempting to increase carbon storage via fire suppression. This study highlights the importance of un

One hundred and thirty-nine taxa of mosses are reported from the montane forest zone of southwest Ethiopia. Of these, 53 taxa are new country records and Meteoriopsis reclinata (Mull. Hal.) M. Fleisch. ex Broth. is, in addition, new to Africa. Most of the new records are of species also found in Uganda, Kenya or Tanzania, but there are some surprises, such as Fabronia perciliata Mull. Hal. with the closest location in South Africa and Namibia, Entodontella cameruniae Broth. previously known only from West Africa and Bryomaltaea obtusifolia (Hook.) Goffinet, otherwise reported only from the Democratic Republic of the Congo. We list all taxa and give a short account of their frequency and in which habitat and on which substrate they grow. That such a large proportion of the species are new to the country suggests that Ethiopia is bryologically very under-explored, and that further exploration will reveal many additional species. In particular, the remnant forests of southwest Ethiopia are likely to be of great importance as bryophyte hotspots.

A recent trend in conservation biology is not only to focus on protected areas of natural vegetation but also on the management of agricultural landscapes, since these landscapes are considered to be-of vital importance for overall landscape biodiversity both through the opportunity for species to thrive there and as conduits for inter-patch dispersal. Since trees are considered to be key structures to enhance biodiversity in agricultural landscapes, we need to understand what factors regulate their occurrences. Farmers choices will decide the composition of land-uses and the associated densities and composition of trees. We compared tree density and tree species composition across eight different land use types replicated in ten agricultural landscapes in relatively humid climates of mid-altitudes (1500-2500 m asl) in Ethiopia. In each landscape five transects of 1 km divided into 50 plots of 20 x 20 m were surveyed for woody plants. Annual crop plots had a low tree density (of trees >10 cm DBH) (6 per ha), but since it generally was the most abundant land use type altogether, many tree species were still found there (4-29 per transect in the different landscapes). Most tree species had their highest relative occurrence in the perenial crops land-use type and among the different perenial crop types, plots with coffee were more species rich than plots with khat (Catha edulis) (a stimulant crop increasing in frequency); plots with Eucalyptus trees were intermediate. A few species were more associated with grazing areas and homegardens indicating that a combination of land-uses enhances the overall species diversity in these agricultural landscapes. However, if the trend of increasing areas of khat and Eucalyptus would lead to decreases in shade coffee there is a risk for severe erosion of tree density and species richness across these landscapes with cascading effects on associated biodiversity.