Michelle Greve is an associate professor in the Department of Plant and Soils Sciences at the University of Pretoria, South Africa. She is broadly interested in what drives patterns of diversity. She has a particular interest in the drivers of the structure and distribution of grassy habitats (grasslands and savannas). Michelle started her career exploring patterns of diversity and distribution in African systems at macroecological scales, and now complements this work with field and experimental studies. A particular focus has been using functional traits to understand responses to disturbances, and assessing drivers of distribution and structure at different spatial scales. Amongst others, this includes assessing factors and traits that affect seedling survival, and how this scales up to understanding the structure and distribution of grassy biomes; as well as assessing patterns and drivers of grassland diversity at different spatial scales. Michelle also has a long-standing interest in the invasion ecology of the sub-Antarctic islands.

Abstract:

Southern African grasslands: diverse, essential but undervalued

Temperate grasslands are the most transformed and least protected biome in the world. South Africa is home to an extensive area of temperate grasslands. Traditionally, low biodiversity value was placed on South African grasslands: early ecologists considered them to be forests degraded by long-term anthropogenic burning practices. We now know that they are ancient and diverse systems that originated before humans. Despite the fact that the grasslands of South Africa are the second-most diverse biome in South Africa, and that grasslands provide valuable ecosystem services, fairly little is known about the diversity of the grassland flora. I summarise what we know about patterns and drivers of grassland diversity and highlight some interesting aspects of the natural history of the biome. Grasslands harbour high alpha and beta diversity patterns at species, genus and family level. Recent work has shown that alpha diversity for the biome is higher than previously thought. Also, forbs, which, compared to grasses are rarely studied, show considerably higher beta, and often higher alpha diversity than grasses, indicating that they contribute most to the overall diversity of the grassland biome. Climatic factors are poor predictors of diversity patterns within the biome. Also, while it has been suggested that fire and frost may be important in distinguishing grasslands from the similar savanna biome by suppressing the recruitment of woody seedlings, several lines of evidence suggest that many tree species can withstand fire and frost events. Therefore, much remains to be determined in understanding the diversity and distribution of South African grasslands.

Since her graduation from Charles University in Prague in 1987 she is employee of Institute of Botany of the Czech Academy of Sciences in Trebon. Her main interest is plant experimental and functional morphology. Her main topics are: clonality in plants, response of root sprouting plants to damage, bud bank ecology, architecture of herbaceous plants. She is author of database of clonal and bud bank traits of central European flora CLO-PLA. In 2020, she got prestigious grant Praemium Academiae and this enabled her to build an interdisciplinary team of ecologists, anatomists, ecophysiologists to study functions of belowground plant organs.

Abstract:

Ecologist in the enchanted belowground world of plant communities

Vegetation scientists generally assume that the belowground parts of plant communities mirror the aboveground parts and thus all important community responses and functions can be assessed solely by the examination of a community from above. However, this concept is not viable when we also look at a plant community from below. First, we can see that in herbaceous communities, green shoots are annual, while the longevity of roots, rhizomes, and bulbs can range from one season to decades. The relative dominance of species assessed according to the area of cover of green shoots may not be equal to dominance according to the area or biomass of belowground organs. Aboveground plant traits can be easy to measure but belowground traits are often better at responding to environmental gradients. This leads us to question whether we can ignore the belowground plant parts of our communities. I will try to answer this question showing examples of the different functions belowground plant parts provide, namely clonal multiplication and mobility, as well as the response to disturbance and productivity gradients.

Benjamin Blonder is an ecologist focusing on plant response to climate change, past and present. He is assistant professor in the Department of Environmental Science, Policy, and Management at the University of California Berkeley. He previously was assistant professor at Arizona State University's School of Life Sciences and Natural Environment Research Council independent research fellow at the Environmental Change Institute at the University of Oxford. He is also interested in improving science education through experiential approaches. He co-founded and currently works with the University of Arizona Sky School, a program that provides inquiry-based outdoor science education to K-12 students throughout the southwest.

Abstract:

A hotter and drier future: consequences for Rocky Mountain aspen forests

Extreme droughts are becoming increasingly common. In semi-arid or snowmelt-dominated regions, these climate extremes may have major effects on plant genetics, demography, and ultimately geographic distribution. Critically, these may be genetically variable, such that impacts are more severe for some populations than others, and may also be temporally lagged, so that the consequences of a given perturbation may not be apparent until several years later.

I will illustrate some of these impacts and concepts through a case study of quaking aspen (Populus tremuloides). Aspen is a foundation tree species that occurs widely from Alaska (northern USA) to Jalisco (central MX), often in monodominant stands. It has high genetic variation, can grow in spatially extensive clones, and occurs in both diploid and triploid cytotypes. The species is experiencing large mortality events in many parts of its range, and is a high priority for land management and conservation.

I will first highlight the importance of considering genetic variation in predicting species’ demographic responses to changing environments. Using a combination of hyperspectral remote sensing, genomic, and field census data, I will show that the demographic consequences of heat and drought differ strongly among diploid and triploid individuals, and that allelic genetic variation is as important to predicting demography as topographic factors. Thus, mapping the geographic mosaic of genetic variation is necessary for accurate predictions of demographic responses to environmental change – and remote sensing will soon make this mapping possible.

I will second highlight the role of temporal lags in demographic responses to climate extremes. The consequences of stressors may not become apparent for months or years after a stressor, due to interactions among carbon starvation and hydraulic failure mechanisms. Using spatially and temporally extensive datasets for drought, temperature, phenology, and mortality, I will show that climate events occurring several years prior can predict phenological and demographic variation in future years, and again that genetic variation strongly influences the magnitude of these lags.

These case studies highlight the utility of integrating genomics and remote sensing with field-based measurements of vegetation, and help move us towards better prediction of the spatial and temporal heterogeneity of vegetation responses to climate extremes.

Dr. Mahesh Sankaran is a Professor of Ecology at the National Centre for Biological Sciences, Bengaluru, India. He is a community and ecosystems ecologist who has worked extensively in savanna and forest ecosystems in Africa and India. His interests lie in understanding the factors that regulate the distribution, structure and dynamics of savanna ecosystems from local to global scales, the effects of top-down and bottom-up forces in regulating savanna structure and function, and the potential responses of savanna ecosystems to ongoing and future climatic changes.

Abstract:

Tropical grassy biomes: A South Asian Perspective

Tropical grassy biomes (TGBs), which include both savannas and grasslands, are ancient biomes that harbor unique biodiverse and support the livelihoods of a large fraction of the world’s human population. Although ecologists have long recognized the importance of the savannas of Africa, Australia and South America, the TGBs of Asia have been largely ignored or misclassified. Here, I first address the historical legacies that underlie this lack of appreciation of South Asian TGBs, discuss the challenges with mapping and conserving these biomes in S. Asia, and explore the potential responses of these biomes to select global change drivers. I then focus on a unique TGB – the montane forest-grassland mosaics of the southern Western Ghats biodiversity hotspot – and discuss the factors that structure these bi-phasic ecosystems and their potential responses to future climate change, and the threats and challenges facing the conservation and restoration of these ecosystems.