Ethiopia is land of geographical contrasts with elevations that range from 125 m below sea level in the Danakil Depression to 4533 m above sea level in the Semien Mountains, a world heritage site. The diverse climate of various ecological regions of the country has driven the establishment of diverse vegetation, which range from Afroalpine vegetation in the mountains to the arid and semi-arid vegetation type in the lowlands. The formation of Ethiopian vegetation is highly connected to the climate and geological history of the country. Highland uplift and rift formation due to volcanic forces formed novel habitats with different topography and climatic conditions that have ultimately become drivers for vegetation diversification. Due to Ethiopia's connection with the temperate biome in the north and the Arabian Peninsula during the dry glacial period, the biotic assemblage of Ethiopian highlands consists of both Afrotropical and palearctic biota. In general, eight distinct vegetation types have been identified in Ethiopia, based mainly on elevation and climate gradients. These vegetation types host their own unique species, but also share several common species. Some of the vegetation types are identified as centers of endemism and have subsequently been identified globally as the East African Afromontane hotspot. Ethiopia is biologically rich, with more than 6500 vascular plant species. Of these species, 12% are endemic mainly due to geographical isolation and unique climatic conditions. However, researchers have yet to extensively investigate the ecology, phenology, as well as the evolutionary, genetics, and conservation status of Ethiopian vegetations at community and species level over space and time. This lack of research is a barrier to achieving the goal of zero global plant extinctions. Taxa extinction risk assessment has not been extensively carried out for majority of Ethiopian species. Detailed research is needed to explore how vegetation and species respond to rapidly growing environmental change. Currently, human-induced climate change and habitat fragmentation are severely threatening the country's biodiversity, and the consequences of these effects have not been studied at large. Furthermore, we still lack scientific evidence on how micro- and macro-ecological and evolutionary processes have been shaping vegetation structures in this climatically, topographically, and geologically diverse country. These gaps in our knowledge represent an opportunity for ecologists, geneticists, evolutionary biologists, conservation biologists, and other experts to investigate the biodiversity status and the complex ecological processes involved in structuring vegetation dynamics so as to help take effective conservation actions.

Environmental filtering consistently shapes the functional and phylogenetic structure of species across space within diverse forests. However, poor descriptions of community functional and lineage distributions across space hamper the accurate understanding of coexistence mechanisms. We combined environmental variables and geographic space to explore how traits and lineages are filtered by environmental factors using extended RLQ and fourth-corner analyses across different spatial scales. The dispersion patterns of traits and lineages were also examined in a 20-ha tropical rainforest dynamics plot in southwest China. We found that environmental filtering was detected across all spatial scales except the largest scale (100 × 100 m). Generally, the associations between functional traits and environmental variables were more or less consistent across spatial scales. Species with high resource acquisition-related traits were associated with the resource-rich part of the plot across the different spatial scales, whereas resource-conserving functional traits were distributed in limited-resource environments. Furthermore, we found phylogenetic and functional clustering at all spatial scales. Similar functional strategies were also detected among distantly related species, suggesting that phylogenetic distance is not necessarily a proxy for functional distance. In summary, environmental filtering considerably structured the trait and lineage assemblages in this species-rich tropical rainforest.

Background and Aims Our understanding of plant responses to biotic and abiotic drivers are largely based on aboveground plant traits, with little focus on belowground traits despite their key role in water and nutrient uptake. Here, we aimed to understand the extent to which above and belowground traits are coordinated, and how these traits respond to soil moisture gradients and plant intraspecific competition. Methods We chose seedlings of five tropical tree species and grew them in a greenhouse for 16 weeks under a soil moisture gradient (low (drought), medium, and high (well-watered) moisture levels) with and without intraspecific competition. At harvest, we measured nine above and five belowground traits of all seedlings based on standard protocols. Key Results In response to the soil moisture gradient, aboveground traits are found to be consistent with the leaf economics spectrum whereas belowground traits are inconsistent with the root economics spectrum. We found high specific leaf area and total leaf area in well-watered conditions while high leaf dry matter content, leaf thickness and stem dry matter content were observed in drought conditions. However, belowground traits showed contrasting patterns with high specific root length but low root branching index in the low water treatment. The correlations between above and belowground traits across the soil moisture gradient were variable. That is, specific leaf area was positively correlated with specific root length, while it was negatively correlated with root average diameter across moisture levels. However, leaf dry matter content was unexpectedly positively correlated with both specific root length and root branching index. Intraspecific competition has influenced both above and belowground traits, but interacted with soil moisture to affect only belowground traits. Consistent with functional equilibrium theory, more biomass was allocated to roots under drought conditions, and to leaves under sufficient soil moisture conditions. Conclusions Our results indicate that the response of belowground traits to plant intraspecific competition and soil moisture conditions may not be inferred using aboveground traits suggesting that multiple resource use axes are needed to understand plant ecological strategies. Lack of consistent leaf—root trait correlations across the soil moisture gradient highlight the multidimensionality of plant trait relationships which needs more exploration.