@article {164787, title = {Responses of African Savanna Trees to Large Herbivore Extinction and Rewilding.}, journal = {Ecol Lett}, volume = {29}, year = {2026}, month = {2026 Mar}, pages = {e70360}, abstract = {

The global decline or extinction of large mammals over the last 50,000 years has caused sweeping changes in the ecosystems they once inhabited. Trophic rewilding holds promise for returning lost ecological function and restoring processes that support ecosystem resilience, but there remains considerable uncertainty surrounding the efficacy of rewilding. To address this uncertainty, we experimentally excluded a diverse African savanna mammal community from replicated plots for 18 years to simulate extinction. Herbivore exclusion caused a rapid increase in tree cover, which was underlain by shifts in community composition and increases in canopy area, growth rate and density. We then removed the exclosure fences, simulating rewilding. Reintroducing herbivores rapidly reduced tree cover and largely reversed individual phenotypic shifts, but tree density remained elevated despite increased mortality rates after reintroduction. Our results suggest that even short-term extirpation can cause complex shifts in vegetation communities, some of which may be resistant to rewilding.

}, keywords = {Africa, Animals, Conservation of Natural Resources, Extinction, Biological, Grassland, Herbivory, Mammals, Trees}, issn = {1461-0248}, doi = {10.1111/ele.70360}, url = {https://onlinelibrary.wiley.com/doi/10.1111/ele.70360}, author = {Coverdale, Tyler C and Sankaran, Mahesh and Davies, Andrew B and Ratnam, Jayashree and Wigley, Benjamin J and Augustine, David J} } @article {159713, title = {Effects of sampling methodology on phenology indices: Insights from sites across India and modelling.}, journal = {J Biosci}, volume = {50}, year = {2025}, month = {2025}, abstract = {

Plant phenology is the study of the timing and extent of leaf, flower, and fruit production. Phenology data are used to study the drivers of cyclicity and seasonality of plant life-history stages, interactions with organisms such as pollinators, and effects of global change factors. Indices such as the timing of phenological events, and the proportion of individuals in a particular phenophase, seasonality, and synchrony have often been used to summarise plant phenology data. However, these indices have specific utilities and limitations and may be sensitive to sampling methodology, making cross-site comparisons challenging, particularly when data collection methods vary in terms of sample size, observation frequency, and the resolution at which phenophase intensity scores/values are recorded. We used fruiting phenology data from tropical trees across five sites in India to study the effects of sampling methodology on two indices: population-level synchrony (overlap) and seasonality. We supplemented these results with simulations of fast- and slow-changing phenologies to test for the effects of sampling methodology on these indices. We found that the overlap index is sensitive to the resolution of phenophase intensity measurement, with coarser intensity measures leading to overestimation of the overlap index. The seasonality index, on the other hand, was not affected by intensity resolution. Simulations indicated that finer intensity resolution is more important than frequency of observation to accurately estimate population synchrony and seasonality for fast- and slow-changing phenophases. Based on our findings, we provide recommendations for future study designs of tropical tree phenology research, particularly for long-term or cross-site studies.

}, keywords = {Flowers, Fruit, India, Plant Leaves, Pollination, Seasons, Trees}, issn = {0973-7138}, author = {Tiruvaimozhi, Yadugiri V and Teegalapalli, Karthik and Reddy, Abinand and Murali, Akhil and Datta, Aparajita and Krishnan, Aparna and Ratnam, Jayashree and Sankaran, Mahesh and Ongole, Shasank and Kasinathan, Srinivasan and Raman, T R Shankar and Ramaswami, Geetha} } @article {152246, title = {Climate and vegetation collectively drive soil respiration in montane forest-grassland landscapes of the southern Western Ghats, India}, journal = {Journal of Tropical Ecology}, volume = {40}, year = {2024}, month = {09/2024}, chapter = {e16}, abstract = {

CO2 release rates from soils via soil respiration play an important role in the carbon budget of terrestrial ecosystems. Though the roles of soil temperature and moisture on soil respiration are well recognised, less is known about how their effects vary across different land-cover types. This study looked at the interactive effects of land-cover change and microclimate on temporal patterns of soil respiration in a montane forest-grassland-plantation mosaic in a highly diverse but climatically sensitive ecosystem in the tropical Western Ghats of India. Across all vegetation types, soil respiration rates were highest during south-west monsoon (June{\textendash}October), when root growth, litter decomposition and microbial activity are relatively high and were lowest during the summer. Among vegetation types, soil respiration rates were higher in grasslands compared to non-native pine plantations, whereas that of forest and invasive wattle (Acacia mearnsii) plantations were intermediate between grasslands and pine plantations. The decline in respiration rates following conversion from grasslands to pine plantations could be due to relatively lower microbial activity, soil temperatures and, subsequently, slower litter decomposition. In addition, the sensitivity of soil respiration to changes in temperature and moisture differed between different vegetation types. Across all vegetation types, respiration was largely insensitive to changes in soil temperature when moisture levels were low. However, when soil moisture levels were high, respiration increased with temperature in grassland and wattle patches, decreased in the case of pine plantations and remained largely unchanged in shola forests. Our results suggest that changes in aboveground vegetation type can significantly affect soil C cycling even in the absence of any underlying differences in soil type.

}, doi = {10.1017/S0266467424000142}, author = {Joshi, Atul and Ratnam, Jayashree and Paramjyothi, Harinandanan and Sankaran, Mahesh} } @article {152143, title = {Indian wildlife ecology comes of age.}, journal = {Nat Ecol Evol}, year = {2024}, month = {2024 Dec 16}, issn = {2397-334X}, doi = {10.1038/s41559-024-02622-2}, author = {Bhaumik, Vaishali and Kumar, Ajith and Ratnam, Jayashree} } @article {145418, title = {Restoration of open ecosystems in the face of climate change}, journal = {GLOBAL ECOLOGY AND CONSERVATION}, volume = {53}, year = {2024}, month = {09/2024}, abstract = {

Open ecosystems occur all around the world in various forms including temperate and tropical grasslands, savannas, shrublands, heathlands, among others. They are home to unique biodiversity, provide key ecosystem services and sustain traditional livelihoods of nearly two billion people. In the face of ongoing climate change, practitioners aiming to restore open ecosystems need the support of the scientific community more than ever. The aim of this Special Issue (SI) is to provide an attention-grabbing collection of high-quality publications addressing the growing challenges of open ecosystems restoration. The SI contains 14 papers that fill various, often interdisciplinary knowledge gaps. Three papers deal with the challenges of identifying the right target states, including the genetic composition of constituting plant species, for restoration under changing environmental conditions and competing stakeholder interests. Five papers advance our understanding on the appropriate timing and methodological toolkit to actively ignite reassembly of the target plant communities, while two papers focus on situations where spontaneous processes can still also be relied on. The interaction of open ecosystems health and recovery with higher trophic levels, particularly grazers, is also discussed in three papers. Finally, a review paper systematically identifies further knowledge gaps, such as the role of soil microbes in grassland recovery and makes clear guidelines how to fill them. Due to the variety of topics and the rigorous content, this SI provides strong support for open ecosystems restoration policy and practice under the UN Decade on Ecosystem Restoration and beyond.

}, doi = {10.1016/j.gecco.2024.e02989}, author = {Tolgyesi, Csaba and Helm, Aveliina and Ratnam, Jayashree and Silveira, FAO and Torok, Peter} } @article {134596, title = {Patterns and consequences of invasion of tropical montane forests by Cestrum aurantiacum Lindl. in the Western Ghats}, journal = {FRONTIERS IN ECOLOGY AND EVOLUTION }, year = {2023}, month = {08/2023}, abstract = {

In the montane forest-grassland mosaics of the Western Ghats, land cover conversion to silviculture and agriculture over the last five decades has resulted in both loss of natural habitats and widespread invasion of remnant habitat patches. While invasion of the grassland habitats of the mosaic has been relatively well studied, there have been few attempts to understand the extent to which forest habitats (locally known as sholas) have been affected by the spread of exotic species. Here we examine the patterns and impacts of invasion of shola forest understoreys by Cestrum aurantiacum Lindl., an exotic shrub species. At the landscape scale, we demonstrate that the presence and abundance of this invasive in shola understories is negatively related to distance from tea plantations. Further, the intensity of invasion is higher in areas with greater seasonality of temperature and lower mean annual precipitation. At the patch scale, invasion is greatest at shola edges and away from stream courses. We find that C. aurantiacum abundance has negatively affected the regeneration of native shola tree species as well as the abundance of native shola understorey shrubs. Fifty three percent of invaded plots had no native shrubs present. In plots where both C. aurantiacum and native shrubs were present in large enough numbers, we found evidence of negative spatial dependence between stem locations of C. aurantiacum and native shrubs. Our findings have important implications for the management and conservation of these mosaics.

}, doi = {10.3389/fevo.2023.1198085}, author = {Das, Arundhati A. and Ratnam, Jayashree and Jathanna, Devcharan} } @article {116708, title = {Chronic browsing by an introduced mammalian herbivore in a tropical island alters species composition and functional traits of forest understory plant communities}, journal = {BIOTROPICA }, year = {2022}, month = {08/2022}, abstract = {

Mammalian herbivores have large-scale impacts on vegetation, altering structure, and species composition, especially in tropical grasslands and savannas. However, there is limited understanding of the potential impacts of mammalian herbivores in tropical wet forests, where they are typically less abundant. We investigated the effects of an introduced mammalian herbivore chital (Axis axis) on vegetation structure, composition and leaf functional traits of tropical evergreen forests of the Andaman Islands, India. Across seven islands, representing a gradient of herbivore densities, increasing chital presence was associated with decreased understory richness, understory density and adult tree richness, but was not related to adult tree density or size class distributions. We also found a significant decrease in community level leaf palatability traits (specific leaf area decreased and leaf thickness increased) with increasing chital habitat use. This community level shift in leaf trait values was better explained by intraspecific variation in leaf traits across islands rather than changes in species composition. In summary, we show persistent long-term impacts of an introduced mammalian herbivore on understory tropical tree communities although there is little impact on adult tree communities. Our results also show that functional traits of species can be altered in response to novel herbivory, even at herbivore densities where there are no detectable impacts on adult forest structure or composition. Such altered functional traits may potentially alter ecosystem functioning in these forests even without changes in vegetation structure. Abstract in Hindi is available with online material.

}, doi = {10.1111/btp.13149}, author = {Anujan, Krishna and Ratnam, Jayashree and Sankaran, Mahesh} } @article {131931, title = {Human{\textendash}elephant conflict mitigation as a public good: what determines fence maintenance?}, journal = {Ecology and Society}, volume = {27}, year = {2022}, month = {2022}, abstract = {

Negative interactions between humans and elephants are known to have serious consequences, resulting in loss of life and deterioration in the quality of life for both species. Reducing human{\textendash}elephant conflicts (HEC) is essential for elephant conservation as well as social justice. Non-lethal electric fences placed around villages or communities are a widely used intervention to mitigate HEC. Such barriers act as non-excludable and non-subtractable resources{\textemdash}i.e., public goods{\textemdash}that must be maintained collectively by beneficiaries or the State. Despite being fairly effective when well maintained, most such fences in northeast India are poorly maintained. This leads to our central question: why are some fences well maintained and others poorly maintained? We studied 19 such fences using qualitative comparative analysis, Ostrom{\textquoteright}s social-ecological systems framework, and a grounded theory approach, incorporating qualitative social science tools. We found that, contrary to our hypothesis, the functionality of fences cannot be predicted based on the design of the fence, whether or not the community made cash payments, or ethnic homogeneity or leadership in the village. Instead, we found there are three potential pathways of maintenance: (1) a community maintainer, (2) the community self-organizes, and (3) the Forest Department. Maintenance occurs when there is a congruence between perceived costs and benefits for the entity responsible for fence maintenance. These costs and benefits are diverse, including not just material benefits but intangibles like goodwill, sense of safety, social standing, and a feeling of fairness. We highlight these factors and provide recommendations for practitioners and policy.

}, doi = {10.5751/ES-13271-270324}, author = {Kamdar, Arjun and Baishya, Hiten Kumar and Nagendra, Harini and Ratnam, Jayashree and Smith, David and Sekar, Nitin} } @article {112957, title = {The thermal niche and phylogenetic assembly of evergreen tree metacommunities in a mid-to-upper tropical montane zone.}, journal = {Proc Biol Sci}, volume = {289}, year = {2022}, month = {2022 Jun 29}, pages = {20220038}, abstract = {

Frost and freezing temperatures have posed an obstacle to tropical woody evergreen plants over evolutionary time scales. Thus, along tropical elevation gradients, frost may influence woody plant community structure by filtering out lowland tropical clades and allowing extra-tropical lineages to establish at higher elevations. Here we assess the extent to which frost and freezing temperatures influence the taxonomic and phylogenetic structure of naturally patchy evergreen forests (locally known as ) along a mid-upper montane elevation gradient in the Western Ghats, India. Specifically, we examine the role of large-scale macroclimate and factors affecting local microclimates, including patch size and distance from edge, in driving metacommunity structure. We find that the metacommunity shows phylogenetic overdispersion with elevation, with greater representation of extra-tropical lineages above 2000 m, and marked turnover in taxonomic composition of woody communities near the frost-affected forest edge above 2000 m, from those below 2000 m. Both minimum winter temperature and patch size were equally important in determining metacommunity structure, with plots inside very large dominated by older tropical lineages, with many endemics. Phylogenetic overdispersion in the upper montane metacommunity thus resulted from tropical lineages persisting in the interiors of large closed frost-free where their regeneration niche has been preserved over time.

}, keywords = {Biological Evolution, Cold Temperature, Fever, Forests, Phylogeny, Wood}, issn = {1471-2954}, doi = {10.1098/rspb.2022.0038}, author = {Das, Arundhati Abin and Ratnam, Jayashree} } @article {98079, title = {Expansion of pine into mid-elevation Himalayan oak forests: Patterns and drivers in a multiple-use landscape}, journal = {Forest Ecology And Management}, volume = {119491}, year = {2021}, month = {10/2021}, abstract = {

Oak species worldwide are experiencing declines, with negative consequences for hardwood forests and their associated biodiversity, but the causes of these declines vary across species and habitats. We examine changes in extent of banj oak-dominated (Quercus leucotrichophora) moist temperate hardwood forests in a Western Hi-malayan landscape between 1991 and 2017. Using classified satellite imagery from 1991, 2001 and 2017, we found that dense banj oak forests have undergone substantial degradation and loss of area, while chir pine (Pinus roxburghii) forests have expanded, largely by replacing degraded banj oak stands. This transition was most likely to occur at sites that had lower levels of winter precipitation and Topographic Wetness Index (TWI) values and more pine forest in the surrounding landscape. Our findings are consistent with known requirements of shade and moisture for the recruitment of banj oak. Loss of banj oak forests is likely to reduce biodiversity and a number of ecosystem services linked to the well-being of local communities.

}, doi = {10.1016/j.foreco.2021.119491}, author = {Das, Arundhati and Menon, Tarun and Ratnam, Jayashree and Thadani, Rajesh and Rajashekar, Gopalakrishnan and Fararoda, Rakesh and Shahabuddin, Ghazala} } @article {95775, title = {Functional traits predict tree-level phenological strategies in a mesic Indian savanna}, journal = {BIOTROPICA}, year = {2021}, month = {06/2021}, abstract = {

Leaf phenology influences terrestrial primary production by determining the period of carbon uptake. While dominant leaf habit (evergreen/deciduous) is predictable at large scales based on environmental factors, there is substantial variability in the timing of key events such as leaf flush and senescence at smaller site-level scales. How much of this variability is explained by species functional traits related to a plant{\textquoteright}s carbon economy? We monitored leaf phenology for 113 individual trees of eleven dominant species in an Indian mesic savanna. Specifically, we related leaf functional traits and wood density to the (i) timing of leaf flush, leaf maturity, peak canopy, and senescence, (ii) duration of leaf deployment, (iii) duration from start of senescence to leaflessness, and (iv) time to attainment of peak mature canopy following leaf flush. We expected species that use resources conservatively (low specific leaf area (SLA), high leaf dry matter content, low leaf nitrogen, and high wood density) to senesce later and retain their leaves longer. For all species, leaflessness was most pronounced in early dry season and leaf flushing occurred in the late dry season. Species with high leaf carbon and dry matter content showed earlier leaf maturation, attained peak mature canopies sooner, and deployed leaves longer. Species with high SLA, leaf nitrogen, and low wood density showed earlier senescence but relationships were weak. In this savanna, phenology at fine scales was indeed associated with species functional traits relating to carbon investment, but these relationships were strong only when intra-specific variation in phenology was low.

}, doi = {10.1111/btp.12993}, author = {Ongole, Shasank and Teegalapalli, Karthik and Byrapoghu, Venkateshwarlu and Ratnam, Jayashree and Sankaran, Mahesh} } @article {92880, title = {Monsoon forced evolution of savanna and the spread of agro-pastoralism in peninsular India.}, journal = {Sci Rep}, volume = {11}, year = {2021}, month = {2021 Apr 27}, pages = {9032}, abstract = {

An unresolved issue in the vegetation ecology of the Indian subcontinent is whether its savannas, characterized by relatively open formations of deciduous trees in C-grass dominated understories, are natural or anthropogenic. Historically, these ecosystems have widely been regarded as anthropogenic-derived, degraded descendants of deciduous forests. Despite recent work showing that modern savannas in the subcontinent fall within established bioclimatic envelopes of extant savannas elsewhere, the debate persists, at least in part because the regions where savannas occur also have a long history of human presence and habitat modification. Here we show for the first time, using multiple proxies for vegetation, climate and disturbances from high-resolution, well-dated lake sediments from Lonar Crater in peninsular India, that neither anthropogenic impact nor fire regime shifts, but monsoon weakening during the past ~ 6.0\ kyr\ cal. BP, drove the expansion of savanna at the expense of forests in peninsular India. Our results provide unambiguous evidence for a climate-induced origin and spread of the modern savannas of peninsular India at around the mid-Holocene. We further propose that this savannization preceded and drove the introduction of agriculture and development of sedentism in this region, rather than vice-versa as has often been assumed.

}, issn = {2045-2322}, doi = {10.1038/s41598-021-88550-8}, author = {Riedel, Nils and Fuller, Dorian Q and Marwan, Norbert and Poretschkin, Constantin and Basavaiah, Nathani and Menzel, Philip and Ratnam, Jayashree and Prasad, Sushma and Sachse, Dirk and Sankaran, Mahesh and Sarkar, Saswati and Stebich, Martina} } @article {89124, title = {Varying impacts of logging frequency on tree communities and carbon storage across evergreen and deciduous tropical forests in the Andaman Islands, India}, journal = {FOREST ECOLOGY AND MANAGEMENT}, year = {2021}, month = {02/20201}, abstract = {

The majority of Earth{\textquoteright}s tropical forests have been selectively logged; some on repeated occasions. Selective logging is known to affect forest structure, composition and function in various ways, but how such effects vary with logging frequency and across forest types remains unclear. In the Andaman Archipelago in India, we examined adult and pole-sized trees in baseline (unlogged since 1990s), once-logged (logged between 2007 and 2014) and twice-logged (logged in early 1990s and between 2007 and 2014) evergreen and deciduous forests, and tested whether higher logging frequency was associated with lower canopy cover, tree density, tree diversity, aboveground carbon stocks and divergence in species composition, including increased relative abundances of deciduous species in these forests. While once-logged evergreen and deciduous forests were similar to their respective baselines for most attributes assessed, and twice-logged evergreen forests had 22-24\% lower adult tree density and diversity, twice-logged deciduous forests had 17-50\% lower canopy cover, pole density, adult species diversity and above-ground carbon stocks, and 12\% higher deciduous fractions compared to the baselines. Collectively our results reveal lasting impacts of repeated selective logging, even at relative low intensity, on tree communities and carbon storage. These impacts can potentially be mitigated by reducing logging frequency and retaining unlogged patches in logged landscapes, but management must also incorporate heterogeneity in responses and recovery across different forest types. In the Andaman Islands, all forests may require more than 15-25 years between logging events, with deciduous forests potentially requiring more stringent extraction limits compared to evergreen forests.

}, doi = {10.1016/j.foreco.2020.118791}, author = {Surendra, Akshay and Osuri, A. M and Ratnam, Jayashree} } @article {73041, title = {Grasses continue to trump trees at soil carbon sequestration following herbivore exclusion in a semi-arid African savanna.}, journal = {Ecology}, year = {2020}, month = {2020 Feb 06}, pages = {e03008}, abstract = {

While studies have shown that mammalian herbivores often limit aboveground carbon storage in savannas, their effects on belowground soil carbon storage remains unclear. Using three sets of long-term, large herbivore exclosures with paired controls, we asked how almost two decades of herbivore removal from a semi-arid savanna in Laikipia, Kenya affected aboveground (woody and grass) and belowground soil carbon sequestration, and determined the major source (C vs. C ) of belowground carbon sequestered in soils with and without herbivores present. Large herbivore exclusion, which included a diverse community of grazers, browsers, and mixed-feeding ungulates, resulted in significant increases in grass cover (~22\%), woody basal area (~8 m ha ) and woody canopy cover (31\%), translating to a ~8.5 t ha increase in aboveground carbon over two decades. Herbivore exclusion also led to a 54\% increase (20.5 t ha ) in total soil carbon to 30 cm depth, with ~71\% of this derived from C grasses (vs. ~76\% with herbivores present) despite substantial increases in woody cover. We attribute this continued high contribution of C grasses to soil C sequestration to the reduced offtake of grass biomass with herbivore exclusion together with the facilitative influence of open sparse woody canopies (e.g. Acacia spp.) on grass cover and productivity in this semi-arid system.

}, issn = {1939-9170}, doi = {10.1002/ecy.3008}, author = {Wigley, Benjamin J and Augustine, David J and Coetsee, Corli and Ratnam, Jayashree and Sankaran, Mahesh} } @article {66850, title = {Comment on "The global tree restoration potential".}, journal = {Science}, volume = {366}, year = {2019}, month = {2019 10 18}, abstract = {

Bastin {\textquoteright}s estimate (Reports, 5 July 2019, p. 76) that tree planting for climate change mitigation could sequester 205 gigatonnes of carbon is approximately five times too large. Their analysis inflated soil organic carbon gains, failed to safeguard against warming from trees at high latitudes and elevations, and considered afforestation of savannas, grasslands, and shrublands to be restoration.

}, keywords = {Carbon, Carbon Sequestration, Climate Change, Soil, Trees}, issn = {1095-9203}, doi = {10.1126/science.aay7976}, author = {Veldman, Joseph W and Aleman, Julie C and Alvarado, Swanni T and Anderson, T Michael and Archibald, Sally and Bond, William J and Boutton, Thomas W and Buchmann, Nina and Buisson, Elise and Canadell, Josep G and Dechoum, Michele de S{\'a} and Diaz-Toribio, Milton H and Durigan, Giselda and Ewel, John J and Fernandes, G Wilson and Fidelis, Alessandra and Fleischman, Forrest and Good, Stephen P and Griffith, Daniel M and Hermann, Julia-Maria and Hoffmann, William A and Le Stradic, Soizig and Lehmann, Caroline E R and Mahy, Gregory and Nerlekar, Ashish N and Nippert, Jesse B and Noss, Reed F and Osborne, Colin P and Overbeck, Gerhard E and Parr, Catherine L and Pausas, Juli G and Pennington, R Toby and Perring, Michael P and Putz, Francis E and Ratnam, Jayashree and Sankaran, Mahesh and Schmidt, Isabel B and Schmitt, Christine B and Silveira, Fernando A O and Staver, A Carla and Stevens, Nicola and Still, Christopher J and Str{\"o}mberg, Caroline A E and Temperton, Vicky M and Varner, J Morgan and Zaloumis, Nicholas P} } @article {64318, title = {Frost maintains forests and grasslands as alternate states in a montane tropical forest{\textendash}grassland mosaic; but alien tree invasion and warming can disrupt this balance}, journal = {JOURNAL OF ECOLOGY}, year = {2019}, month = {07/2019}, doi = {10.1111/1365-2745.13239}, author = {Joshi, Atul A and Ratnam, Jayashree and Sankaran, Mahesh} } @article {53619, title = {Functional Traits of Trees From Dry Deciduous {\textquotedblleft}Forests{\textquotedblright} of Southern India Suggest Seasonal Drought and Fire Are Important Drivers}, journal = {Front. Ecol. Evol.}, year = {2019}, month = {01/2019}, abstract = {

Two dominant biomes that occur across the southern Indian peninsula are dry deciduous {\textquotedblleft}forests{\textquotedblright} and evergreen forests, with the former occurring in drier regions and the latter in wetter regions, sometimes in close proximity to each other. Here we compare stem and leaf traits of trees from multiple sites across these biomes to show that dry deciduous {\textquotedblleft}forest{\textquotedblright} species have, on average, lower height: diameter ratios, lower specific leaf areas, higher wood densities and higher relative bark thickness, than evergreen forest species. These traits are diagnostic of these dry deciduous {\textquotedblleft}forests{\textquotedblright} as open, well-lit, drought-, and fire-prone habitats where trees are conservative in their growth strategies and invest heavily in protective bark tissue. These tree traits together with the occurrence of a C4 grass-dominated understory, diverse mammalian grazers, and frequent fires indicate that large tracts of dry deciduous {\textquotedblleft}forests{\textquotedblright} of southern India are more accurately classified as mesic deciduous {\textquotedblleft}savannas.{\textquotedblright}

}, doi = {10.3389/fevo.2019.00008}, author = {Ratnam, Jayashree and Chengappa, SK and Machado, Siddarth and Nataraj, N and Osuri, Anand M and Sankaran, Mahesh} } @article {69322, title = {Large herbivores maintain a two-phase herbaceous vegetation mosaic in a semi-arid savanna.}, journal = {Ecol Evol}, volume = {9}, year = {2019}, month = {2019 Nov}, pages = {12779-12788}, abstract = {

Many arid and semi-arid rangelands exhibit distinct spatial patterning of vegetated and bare soil-dominated patches. The latter potentially represent a grazing-induced, degraded ecosystem state, but could also arise via mechanisms related to feedbacks between vegetation cover and soil moisture availability that are unrelated to grazing. The degree to which grazing contributes to the formation or maintenance of degraded patches has been widely discussed and modeled, but empirical studies of the role of grazing in their formation, persistence, and reversibility are limited.We report on a long-term (17\ years) grazing removal experiment in a semi-arid savanna where vegetated patches composed of perennial grasses were interspersed within large (\>10\ m) patches of bare soil.Short-term (3\ years) grazing removal did not allow bare patches to become revegetated, whereas following long-term (17\ years) grazing removal, bare soil patches were revegetated by a combination of stoloniferous grasses and tufted bunchgrasses. In the presence of grazers, stoloniferous grasses partially recolonized bare patches, but this did not lead to full recovery or to the establishment of tufted bunchgrasses.These results show that grazers alter both the balance between bare and vegetated patches, as well as the types of grasses dominating both patch types in this semiarid savanna.Synthesis: Large herbivores fundamentally shaped the composition and spatial pattern of the herbaceous layer by maintaining a two-phase herbaceous mosaic. However, bare patches within this mosaic can recover given herbivore removal over sufficiently long time scales, and hence do not represent a permanently degraded ecosystem state.

}, issn = {2045-7758}, doi = {10.1002/ece3.5750}, author = {Augustine, David J and Wigley, Benjamin J and Ratnam, Jayashree and Kibet, Staline and Nyangito, Moses and Sankaran, Mahesh} } @article {34250, title = {Conservation lessons from large-mammal manipulations in East African savannas: the KLEE, UHURU, and GLADE experiments.}, journal = {Ann N Y Acad Sci}, year = {2018}, month = {2018 May 11}, abstract = {

African savannas support an iconic fauna, but they are undergoing large-scale population declines and extinctions of large (\>5\ kg) mammals. Long-term, controlled, replicated experiments that explore the consequences of this defaunation (and its replacement with livestock) are rare. The Mpala Research Centre in Laikipia County, Kenya, hosts three such experiments, spanning two adjacent ecosystems and environmental gradients within them: the Kenya Long-Term Exclosure Experiment (KLEE; since 1995), the Glade Legacies and Defaunation Experiment (GLADE; since 1999), and the Ungulate Herbivory Under Rainfall Uncertainty experiment (UHURU; since 2008). Common themes unifying these experiments are (1) evidence of profound effects of large mammalian herbivores on herbaceous and woody plant communities; (2) competition and compensation across herbivore guilds, including rodents; and (3) trophic cascades and other indirect effects. We synthesize findings from the past two decades to highlight generalities and idiosyncrasies among these experiments, and highlight six lessons that we believe are pertinent for conservation. The removal of large mammalian herbivores has dramatic effects on the ecology of these ecosystems; their ability to rebound from these changes (after possible refaunation) remains unexplored.

}, issn = {1749-6632}, doi = {10.1111/nyas.13848}, author = {Goheen, Jacob R and Augustine, David J and Veblen, Kari E and Kimuyu, Duncan M and Palmer, Todd M and Porensky, Lauren M and Pringle, Robert M and Ratnam, Jayashree and Riginos, Corinna and Sankaran, Mahesh and Ford, Adam T and Hassan, Abdikadir A and Jakopak, Rhiannon and Kartzinel, Tyler R and Kurukura, Samson and Louthan, Allison M and Odadi, Wilfred O and Otieno, Tobias O and Wambua, Alois M and Young, Hillary S and Young, Truman P} } @article {45438, title = {{\textquoteleft}Foresting{\textquoteright} the grassland: Historical management legacies in forest-grassland mosaics in southern India, and lessons for the conservation of tropical grassy biomes}, journal = {Biological Conservation}, volume = {224}, year = {2018}, month = {08/2018}, pages = {144-152}, abstract = {

Colonial encounters with tropical ecosystems were primarily driven by profit-oriented management practices; witness the extensive network of timber and forestry practices that were set up across colonial India. In contrast, the colonial engagement with the montane forest-grassland mosaics of the higher reaches of the Western Ghats in southern India was marked by intensive investment in vegetation management by colonial foresters that yielded no profits. In this archival study, we trace the history of extensive vegetation transformation in this landscape from the early nineteenth to the early twentieth century. We show how the misperception that the grasslands within this mosaic must have resulted from tree felling, fire-setting and buffalo grazing by indigenous communities led colonial foresters into a century-long effort at {\textquoteleft}foresting{\textquoteright} the grasslands, primarily through large-scale planting of exotic tree species. These efforts persisted despite economic losses and ecological evidence that native tree seedlings planted in the grasslands repeatedly failed to establish. These policies continued unabated into the late twentieth century in newly independent India. Today, the once picturesque landscapes of these ancient forest-grassland mosaics are diminished by large-scale plantations of exotic species. Some of these species have become invasive and pose significant threats to the remnant natural grasslands. While this historical narrative is set in the forest-grassland mosaics of southern India, it finds striking parallels in the current day, with grasslands and savannas globally threatened by the misperception that they are {\textquoteleft}degraded ecosystems{\textquoteright} that can be {\textquoteleft}forested{\textquoteright} or converted to other {\textquoteleft}productive{\textquoteright} land uses. We suggest that this case history portends the potential fates of many of earth{\textquoteright}s threatened tropical grasslands and savannas.

}, doi = {10.1016/j.biocon.2018.05.029}, author = {Joshi, Atul A and Mahesh Sankaran and Ratnam, Jayashree} } @article {26268, title = {Comment on "The extent of forest in dryland biomes".}, journal = {Science}, volume = {358}, year = {2017}, month = {2017 11 17}, abstract = {

Bastin et al (Reports, 12 May 2017, p. 635) infer forest as more globally extensive than previously estimated using tree cover data. However, their forest definition does not reflect ecosystem function or biotic composition. These structural and climatic definitions inflate forest estimates across the tropics and undermine conservation goals, leading to inappropriate management policies and practices in tropical grassy ecosystems.

}, issn = {1095-9203}, doi = {10.1126/science.aao1309}, author = {Griffith, Daniel M and Lehmann, Caroline E R and Str{\"o}mberg, Caroline A E and Parr, Catherine L and Pennington, R Toby and Sankaran, Mahesh and Ratnam, Jayashree and Still, Christopher J and Powell, Rebecca L and Hanan, Niall P and Nippert, Jesse B and Osborne, Colin P and Good, Stephen P and Anderson, T Michael and Holdo, Ricardo M and Veldman, Joseph W and Durigan, Giselda and Tomlinson, Kyle W and Hoffmann, William A and Archibald, Sally and Bond, William J} } @article {11595, title = {Spatial vegetation patterns and neighborhood competition among woody plants in an East African savanna.}, journal = {Ecology}, year = {2017}, month = {02/2017}, abstract = {

The majority of research on savanna vegetation dynamics has focused on the coexistence of woody and herbaceous vegetation. Interactions among woody plants in savannas are relatively poorly understood. We present data from a 10-year longitudinal study of spatially explicit growth patterns of woody vegetation in an East African savanna following exclusion of large herbivores and in the absence of fire. We examined plant spatial patterns and quantified the degree of competition among woody individuals. Woody plants in this semi-arid savanna exhibit strongly clumped spatial distributions at scales of 1 - 5 m. However, analysis of woody plant growth rates relative to their conspecific and heterospecific neighbors revealed evidence for strong competitive interactions at neighborhood scales of up to 5 m for most woody plant species. Thus, woody plants were aggregated in clumps despite significantly decreased growth rates in close proximity to neighbors, indicating that the spatial distribution of woody plants in this region depends on dispersal and establishment processes rather than on competitive, density-dependent mortality. However, our documentation of suppressive effects of woody plants on neighbors also suggests a potentially important role for tree-tree competition in controlling vegetation structure and indicates that the balanced-competition hypothesis may contribute to well-known patterns in maximum tree cover across rainfall gradients in Africa. This article is protected by copyright. All rights reserved.

}, issn = {0012-9658}, doi = {10.1002/ecy.1659}, author = {Dohn, Justin and Augustine, David J and Hanan, Niall P and Ratnam, Jayashree and Sankaran, Mahesh} } @article {5216, title = {Contrasting effects of defaunation on aboveground carbon storage across the global tropics.}, journal = {Nat Commun}, volume = {7}, year = {2016}, month = {2016}, pages = {11351}, abstract = {

Defaunation is causing declines of large-seeded animal-dispersed trees in tropical forests worldwide, but whether and how these declines will affect carbon storage across this biome is unclear. Here we show, using a pan-tropical data set, that simulated declines of large-seeded animal-dispersed trees have contrasting effects on aboveground carbon stocks across Earth{\textquoteright}s tropical forests. In our simulations, African, American and South Asian forests, which have high proportions of animal-dispersed species, consistently show carbon losses (2-12\%), but Southeast Asian and Australian forests, where there are more abiotically dispersed species, show little to no carbon losses or marginal gains ({\textpm}1\%). These patterns result primarily from changes in wood volume, and are underlain by consistent relationships in our empirical data (\~{}2,100 species), wherein, large-seeded animal-dispersed species are larger as adults than small-seeded animal-dispersed species, but are smaller than abiotically dispersed species. Thus, floristic differences and distinct dispersal mode-seed size-adult size combinations can drive contrasting regional responses to defaunation.

}, issn = {2041-1723}, doi = {10.1038/ncomms11351}, author = {Osuri, Anand M and Ratnam, Jayashree and Varma, Varun and Alvarez-Loayza, Patricia and Hurtado Astaiza, Johanna and Bradford, Matt and Fletcher, Christine and Ndoundou-Hockemba, Mireille and Jansen, Patrick A and Kenfack, David and Marshall, Andrew R and Ramesh, B R and Rovero, Francesco and Sankaran, Mahesh} } @article {7041, title = {Savannahs of Asia: antiquity, biogeography, and an uncertain future.}, journal = {Philos Trans R Soc Lond B Biol Sci}, volume = {371}, year = {2016}, month = {2016 Sep 19}, abstract = {

The savannahs of Asia remain locally unrecognized as distinctive ecosystems, and continue to be viewed as degraded forests or seasonally dry tropical forests. These colonial-era legacies are problematic, because they fail to recognize the unique diversity of Asian savannahs and the critical roles of fire and herbivory in maintaining ecosystem health and diversity. In this review, we show that: the palaeo-historical evidence suggests that the savannahs of Asia have existed for at least 1 million years, long before widespread landscape modification by humans; savannah regions across Asia have levels of C4 grass endemism and diversity that are consistent with area-based expectations for non-Asian savannahs; there are at least three distinct Asian savannah communities, namely deciduous broadleaf savannahs, deciduous fine-leafed and spiny savannahs and evergreen pine savannahs, with distinct functional ecologies consistent with fire- and herbivory-driven community assembly. Via an analysis of savannah climate domains on other continents, we map the potential extent of savannahs across Asia. We find that the climates of African savannahs provide the closest analogues for those of Asian deciduous savannahs, but that Asian pine savannahs occur in climates different to any of the savannahs in the southern continents. Finally, we review major threats to the persistence of savannahs in Asia, including the mismanagement of fire and herbivory, alien woody encroachment, afforestation policies and future climate uncertainty associated with the changing Asian monsoon. Research agendas that target these issues are urgently needed to manage and conserve these ecosystems.This article is part of the themed issue {\textquoteright}Tropical grassy biomes: linking ecology, human use and conservation{\textquoteright}.

}, issn = {1471-2970}, doi = {10.1098/rstb.2015.0305}, author = {Ratnam, Jayashree and Tomlinson, Kyle W and Rasquinha, Dina N and Sankaran, Mahesh} }