Floodplain rehabilitation in North Cameroon: Impact on vegetation dynamics

Abstract. Since the construction in 1979 of a dam in the Logone floodplain in the Sahelo‐Sudanian zone of Cameroon, annual inundations have decreased, reducing perennial vegetation as important grazing source for nomadic herds and wildlife during the dry season. Presently, possibilities exist to release excess water for floodplain rehabilitation. In 1994 a pilot release was executed, reflooding 200 km², to verify predicted advantages. Vegetation has been studied from 1984 onwards along a transect covering flooded, recently reflooded and desiccated parts of the floodplain. Since 1993, the floristic composition has also been monitored in a grid in the centre of the impact zone. Cover of perennial grasses, most notably Echinochloa pyr amidalis and Oryza longistaminata increased from 41 to 61% in the reflooded zone. Vetiveria nigritana, a tussock grass that used to be dominant, disappeared slowly after the dam construction and has not shown a comeback. The cover of annual species, most notably Sorghum arundinaceum, a dominant annual grass only since the mid‐1980s, decreased in the reflooded zone from 58% to 34%. If the present conversion rate of annual into perennial grassland is extrapolated, recovery towards a 100% perennial state may be reached after the 2003 flooding season. Apart from favourable climatic conditions, recovery might be dependent on the restoration of soil fertility, limiting an approach focusing on flooding depth only.     

Bird Communities and Biomass Yields in Potential Bioenergy Grasslands

Demand for bioenergy is increasing, but the ecological consequences of bioenergy crop production on working lands remain unresolved. Corn is currently a dominant bioenergy crop, but perennial grasslands could produce renewable bioenergy resources and enhance biodiversity. Grassland bird populations have declined in recent decades and may particularly benefit from perennial grasslands grown for bioenergy. We asked how breeding bird community assemblages, vegetation characteristics, and biomass yields varied among three types of potential bioenergy grassland fields (grass monocultures, grass-dominated fields, and forb-dominated fields), and assessed tradeoffs between grassland biomass production and bird habitat. We also compared the bird communities in grassland fields to nearby cornfields. Cornfields had few birds compared to perennial grassland fields. Ten bird Species of Greatest Conservation Need (SGCN) were observed in perennial grassland fields. Bird species richness and total bird density increased with forb cover and were greater in forb-dominated fields than grass monocultures. SGCN density declined with increasing vertical vegetation density, indicating that tall, dense grassland fields managed for maximum biomass yield would be of lesser value to imperiled grassland bird species. The proportion of grassland habitat within 1 km of study sites was positively associated with bird species richness and the density of total birds and SGCNs, suggesting that grassland bioenergy fields may be more beneficial for grassland birds if they are established near other grassland parcels. Predicted total bird density peaked below maximum biomass yields and predicted SGCN density was negatively related to biomass yields. Our results indicate that perennial grassland fields could produce bioenergy feedstocks while providing bird habitat. Bioenergy grasslands promote agricultural multifunctionality and conservation of biodiversity in working landscapes.     

Pastoralist Responses to Floodplain Rehabilitation in North Cameroon

This paper examines the responses of mobile pastoralists to a floodplain rehabilitation program in north Cameroon. From 1993 to 1999, we measured changes in number of camps and herds, and the time they spent in the 600 km² of the Logone floodplain that was reflooded in 1994. The first year, few pastoralists anticipated the reflooding or its impact, and the increase in grazing intensity was caused by a prolonged stay of pastoralists who already used the area for transit. The following three years showed a sharp increase in the number of camps and herds, which stabilized from 1997 onwards. Overall, grazing intensity increased threefold, following the gradually recovering perennial grasslands, with no signs of overexploitation of the area. These developments closely match the ideal preemptive distribution model. We also examined how reflooding affected pastoral incursions in the Waza National Park located in the floodplain.

Cattle grazing in CRP grasslands during the nesting season: effects on avian abundance and diversity

The Conservation Reserve Program (CRP) is a primary tool for restoring grassland in the United States, in part as wildlife habitat, which has benefited declining grassland bird populations. Among potential mid-contract management practices used to maintain early-successional CRP grasslands, cattle grazing had been prohibited and is currently disincentivized during the primary nesting season for birds (much of the growing season), despite the important role that large herbivores historically played in structuring grassland ecosystems. Conservative grazing of CRP grasslands could increase spatial heterogeneity in vegetation structure and plant diversity, potentially supporting higher densities of some grassland bird species and higher bird diversity. Our objective was to determine the effect of experimental cattle grazing on species-specific relative abundance and occupancy, species diversity, and community dissimilarity of grassland birds on CRP grasslands across the longitudinal extent of Kansas, USA (a 63.5-cm precipitation gradient) during the 2017–2019 avian breeding seasons. Fifty-three of 108 fields were grazed by cattle during the growing seasons of 2017 and 2018 and all fields were rested from grazing in 2019. For all analyses, we examined separate model sets for semiarid western versus more mesic eastern Kansas. Using data from line transect surveys, we modeled relative abundances of 5 songbird species: grasshopper sparrow (Ammodramus savannarum), dickcissel (Spiza americana), eastern meadowlark (Sturnella magna), western meadowlark (Sturnella neglecta), and brown-headed cowbird (Molothrus ater). Grazing had delayed yet positive effects on abundances of grasshopper sparrow in western Kansas, and eastern meadowlark in eastern Kansas, but negative effects on dickcissel abundance in western Kansas and especially on burned fields in eastern Kansas. Somewhat counterintuitively, brown-headed cowbirds in western Kansas were more abundant on ungrazed versus grazed fields in the years after grazing began. In addition, we modeled multi-season occupancy of 3 gamebird species (ring-necked pheasant [Phasianus colcicus], northern bobwhite [Colinus virginianus], mourning dove [Zenaida macroura]) and Henslow's sparrow (Centronyx henslowii); grazing did not affect occupancy of these species. In eastern Kansas, species diversity was highest in grazed, unburned fields. In western Kansas, bird communities in grazed and ungrazed fields were dissimilar, as determined from multivariate analysis. Though regionally variable, conservative stocking of cattle on CRP grasslands during the nesting season as a mid-contract management tool might increase bird species diversity by restructuring habitat that accommodates a greater variety of species and decreasing abundances of species associated with taller, denser stands of vegetation.     

Remnant Populations and Plant Functional Traits in Abandoned Semi-Natural Grasslands

Although semi-natural grasslands in Europe are declining there is often a time delay in the local extinction of grassland species due to development of remnant populations, i.e., populations with an extended persistence despite a negative growth rate. The objectives of this study were to examine the occurrence of remnant populations after abandonment of semi-natural grasslands and to examine functional traits of plants associated with the development of remnant populations. We surveyed six managed semi-natural grasslands and 20 former semi-natural grasslands where management ceased 60–100 years ago, and assessed species response to abandonment, assuming a space-for-time substitution. The response of species was related to nine traits representing life cycle, clonality, leaf traits, seed dispersal and seed mass. Of the 67 species for which data allowed analysis, 44 species declined after grassland abandonment but still occurred at the sites, probably as remnant populations. Five traits were associated with the response to abandonment. The declining but still occurring species were characterized by high plant height, a perennial life form, possession of a perennial bud bank, high clonal ability, and lack of dispersal attributes promoting long-distance dispersal. Traits allowing plants to maintain populations by utilizing only a part of their life cycle, such as clonal propagation, are most important for the capacity to develop remnant populations and delay local extinction. A considerable fraction of the species inhabiting semi-natural grasslands maintain what is most likely remnant populations after more than 60 years of spontaneous succession from managed semi-natural grasslands to forest.     

Genetic diversity in perennial ryegrass and white clover among old Dutch grasslands as compared to cultivars and nature reserves

To support conservation policies for old Dutch grasslands that are still in agricultural use, morphological variation and AFLP-based (amplified fragment length polymorphism-based) genetic diversity was studied in perennial ryegrass and white clover populations and compared with the diversity in reference varieties. In addition, AFLP variation was also studied in grasslands located in nature reserves. From principal component analysis (PCA), it appeared that date of ear emergence in perennial ryegrass and characters related to plant vigour in white clover were the main morphological characters separating the reference varieties from the old Dutch grassland populations, and some of the grassland populations from each other. In both species, intrapopulation variation was lower for the reference varieties. Lower heterogeneity within the reference varieties was also found in the AFLP analysis. All common AFLP's observed in old Dutch grasslands could also be found in the reference varieties and nature reserves. Only a small number of low-frequency alleles found in old Dutch grasslands were absent from the other two groups. However, band frequencies of markers could vary considerably between populations, which may have been caused by selection. Analysis of the AFLP data by PCA distinguished the majority of reference varieties from the old Dutch grasslands, and showed genetic differentiation only between some grasslands. Comparison of old Dutch grasslands with grasslands in nature reserves indicated that basically the same range of genetic variation is covered by the two groups. Our study indicates that the Netherlands harbour a more or less continuous population for major parts of the diversity of perennial ryegrass and white clover. It was concluded that no specific conservation measures are presently needed to maintain genetic diversity of perennial ryegrass and white clover occurring in old Dutch grasslands.     

Implications of grazing and burning of grasslands on the sustainable use of francolins (Francolinus spp.) and on overall bird conservation in the highlands of Mpumalanga province, South Africa

We investigated the densities of the Redwing Francolinus levaillantii and Greywing Francolins F. africanus and the diversity of grassland birds in general along a land-use gradient in the highlands of Mpumalanga province, South Africa. Redwing Francolins cannot tolerate intensive grazing and frequent burning and are confined largely to unburnt, ungrazed grasslands. Their density and the species richness of grassland birds in general are negatively correlated with grazing intensity. Redwing populations drop to densities that cannot be utilised by hunters on a sustainable basis in grasslands that are grazed at even moderate levels or burned annually. Nineteen bird species (including five threatened species) were confined to essentially pristine grassland and were never observed in grazed/annually burned grasslands. The Greywing Francolin is more evenly distributed (although always at sub-utilisation densities) along the grassland land-use gradient, and its density is positively correlated with grazing intensity. There are two assemblages of grassland bird species that appear to be indicative of the intensity of habitat utilisation. Populations of grassland birds in the study area are becoming increasingly dependent on isolated patches of pristine grassland and are threatened by management involving annual burning and high stocking rates on a landscape scale.     

Relationships between vegetation and bird community composition in grasslands of the Serengeti

The Serengeti–Mara ecosystem holds one of the largest natural grasslands of the world, which is well known for its large herds of mammals. However, the bird community structure of these grasslands has hardly ever been studied. For the first time, a large‐scale study on grassland bird communities has been conducted in all typical open grasslands of the Serengeti National Park. We used ten grassland plots representing a gradient of increasing vegetation height and also including shrubs and trees to analyse the influence of vegetation structure on the composition of grassland bird communities. Three communities of breeding birds were identified in relation to (a) short grass, (b) intermediate and long grass and (c) wooded grasslands. The bird communities of intermediate, long and wooded grassland were very similar, because of identical dominant bird species. Our results suggest that breeding birds of East African grasslands exhibit two contrasting habitat relationships: (1) birds that are restricted to short grass, and (2) species that are tolerant to vegetational shifts from intermediate grass via long grass to early stages of woody vegetation. Because the vegetation is often driven beyond this range in managed tropical grasslands through high grazing pressure or through shrub encroachment, we expect that the long‐grass bird communities will not generally resist anthropogenic disturbance.     

Waterfowl of a subtropical African floodplain

Many water bodies in arid southern Africa are seasonal and waterfowl habitats become restricted during the dry winters. Nevertheless, some tropical species, such as the white-faced duck, are expanding their ranges into more temperate regions where summer habitats are available, thus increasing pressure on overwintering habitats. The subtropical Pongolo River floodplain is an important overwintering area for a diverse water-fowl community that includes 13 of the 16 species that breed in South Africa and one of the few regular migrants. Historical evidence suggests that numbers of white-faced duck, which represent over 70% of the floodplain community, have increased 10-fold over the last two decades. An abundant, nutritious food (Potamogeton crispus turions) attracts waterfowl to the Pongolo floodplain during winter and an increase in bird fat reserves suggests that they leave for summer breeding grounds in good condition. Unseasonal flood releases from an upstream reservoir may cause low food supplies in late spring before the onset of the summer rainy season when breeding habitats become available. This study emphasizes the need for a better understanding of the role of winter habitats in maintaining waterfowl populations.     

Predicted avian responses to bioenergy development scenarios in an intensive agricultural landscape

Conversion of native prairie to agriculture has increased food and bioenergy production but decreased wildlife habitat. However, enrollment of highly erodible cropland in conservation programs has compensated for some grassland loss. In the future, climate change and production of second-generation perennial biofuel crops could further transform agricultural landscapes and increase or decrease grassland area. Switchgrass (Panicum virgatum) is an alternative biofuel feedstock that may be economically and environmentally superior to maize (Zea mays) grain for ethanol production on marginally productive lands. Switchgrass could benefit farmers economically and increase grassland area, but there is uncertainty as to how conversions between rowcrops, switchgrass monocultures and conservation grasslands might occur and affect wildlife. To explore potential impacts on grassland birds, we developed four agricultural land-use change scenarios for an intensively cultivated landscape, each driven by potential future climatic changes and ensuing irrigation limitations, ethanol demand, commodity prices, and continuation of a conservation program. For each scenario, we calculated changes in area for landcover classes and predicted changes in grassland bird abundances. Overall, birds responded positively to the replacement of rowcrops with switchgrass and negatively to the conversion of conservation grasslands to switchgrass or rowcrops. Landscape context and interactions between climate, crop water use, and irrigation availability could influence future land-use, and subsequently, avian habitat quality and quantity. Switchgrass is likely to provide higher quality avian habitat than rowcrops but lower quality habitat than conservation grasslands, and therefore, may most benefit birds in heavily cultivated, irrigation dependent landscapes under warmer and drier conditions, where economic profitability may also encourage conversions to drought tolerant bioenergy feedstocks.     

Interim Response of Wading Birds (Pelecaniformes and Ciconiiformes) and Waterfowl (Anseriformes) to the Kissimmee River Restoration Project,Florida, U.S.A

Success of the Kissimmee River Restoration Project will be evaluated in part by monitoring populations of wading birds (Pelecaniformes and Ciconiiformes) and waterfowl (Anseriformes). These two waterbird guilds were integral components of the pre‐channelization river–floodplain ecosystem, and both declined substantially following channelization. Restoration is expected to attract wading birds and waterfowl by reintroducing naturally fluctuating water levels, seasonal hydroperiods, and historic vegetation communities. Post‐construction aerial surveys (November 2001 to May 2008) within the Phase I restoration area indicate that the abundance and species richness of both wading birds and waterfowl have shown a positive restoration response thus far. Dry season abundance of aquatic wading birds and waterfowl has exceeded restoration expectations (≥30.6 birds/km² and ≥3.9 birds/km², respectively) each year since the completion of restoration Phase I in 2001. While there has been a significant positive restoration effect on waterfowl abundance, waterfowl species richness (n = 6) has not yet reached the restoration expectation of ≥13 species. Abundance of the terrestrial cattle egret (Bubulcus ibis), which increased dramatically after the majority of floodplain wetlands were converted to cattle pastures in the channelized system, has shown a significant negative response to restoration. It is anticipated that completion of the remaining phases of restoration (II/III), and implementation of the Kissimmee River Headwaters Revitalization water regulation schedule by 2019, will further increase and improve habitat for wading birds and waterfowl by reestablishing floodplain hydrology that more closely mimics historical conditions.     

Ant Community Development on Rehabilitated Ash Dams in the South African Highveld

Ant communities have been widely used as indicators of minesite rehabilitation in Australia and are beginning to play a similar role in other parts of the world. Here we examine ant communities on rehabilitated ash dams associated with a coal‐fired power station on the highveld of South Africa, to improve our understanding of ecosystem development on these substrates. Ants were sampled using pitfall traps at 11 ash‐dam sites, ranging from unrehabilitated to 9‐year‐old rehabilitated sites, as well as two adjacent natural grassland sites. Sampling was conducted on 12 occasions from March 1997 to January 1999. Forty‐nine ant species from 19 genera were recorded during the study. Site species richness was positively correlated with rehabilitation age, ranging from 10 to 25 at ash‐dam sites, compared with 28 and 34 at the two natural grassland sites. There was a humped relationship between total ant abundance and rehabilitation age, with abundance peaking after 5–7 years at levels far higher than those at natural sites. Ordination analysis showed clear separation between ash‐dam and natural sites along the first axis. The unrehabilitated ash‐dam site was also separated from rehabilitated sites along the first axis. Sites of different rehabilitation age were separated along the second axis. Individual ant species showed clear successional patterns across the rehabilitation gradient. Although there was a clear successional trend for the development of ant communities on rehabilitated ash dams, this trend was not toward natural grassland. The lack of convergence toward ant communities of natural grasslands reflects the markedly different substrate and plant composition on ash dams and supports the widely held view that restoration of natural grassland communities is not a realistic goal of ash‐dam rehabilitation. However, the development of species‐rich ant communities, containing at least some late‐successional species, indicates the potential for rehabilitated ash dams to support diverse and complex ecosystems.     

Grassland area determines beetle assemblage dissimilarity from surrounding floodplain forest

Patch size is known to affect biodiversity in fragmented landscapes, but is usually examined in systems where the surrounding matrix habitat is unfavourable. We examined beetle diversity in a floodplain ecosystem that is characterised by naturally occurring grassland patches within a dominant matrix of contrasting yet habitable forest. We asked whether differences in the beetle assemblage between grassland and forest vegetation depended on the area of the grassland patch, which is a function of its flooding frequency and duration: smaller grasslands tend to be higher on the floodplain and are flooded less often and for shorter periods than larger grasslands. We found a negative relationship between grassland area and beetle abundance and species richness, and a positive relationship between grassland area and compositional dissimilarity from the surrounding forest. As expected, we found an overall difference in composition between forest and grassland assemblages, with five beetle species more common in the grasslands. Our study indicates that floodplain grasslands not only support beetle assemblages that are distinct from the surrounding forest, but that assemblages from the larger grasslands are compositionally more distinct than those from smaller grasslands. A likely cause of this pattern is the reduced edge effects and greater environmental contrast between forest and large grasslands that may be exposed to greater variation in local climate. Ongoing changes to flood regimes and potential encroachment of forest plants may decrease grassland area in the future, which may reduce spatial heterogeneity in the insect community in this unique floodplain ecosystem.     

Restoration Practices Have Positive Effects on Breeding Bird Species of Concern in the Chihuahuan Desert

Woody plant encroachment into grasslands is a global concern. Efforts to restore grasslands often assume that removal of woody plants benefits biodiversity but assumptions are rarely tested. In the Chihuahuan Desert of the Southwestern United States, we tested whether abundances of grassland specialist bird species would be greater in plant communities resulting from treatment with herbicides to remove encroaching shrubs compared with untreated shrub‐dominated areas that represented pre‐treatment conditions. In 2010, we surveyed breeding birds and vegetation at 16 treated–untreated pairs. In 2011, we expanded the survey effort to 21 treated–untreated pairs, seven unpaired treatment areas, and five reference grassland areas. Vegetation in treatment areas had higher perennial grass foliar and basal cover and lower shrub foliar cover compared with untreated areas. Several regionally declining grassland specialists exhibited higher occurrence and relative abundance in treated areas. A shrubland specialist, however, was associated with untreated areas and may be negatively impacted by shrub removal. Bird community composition differed between treated and untreated areas in both years. Our results indicate that shrub removal can have positive effects on grassland specialist bird species, but that a mosaic of treated and untreated areas might be most beneficial for regional biodiversity .     

Frequent use of burned grasslands by the vulnerable Saffron-Cowled Blackbird Xanthopsar flavus: implications for the conservation of the species

In the world scenario of declining grassland bird populations, South American species are a particular concern. The Saffron-Cowled Blackbird Xanthopsar flavus is endemic to grasslands in Central and southern South America and its status is vulnerable. Natural history studies stress a number of factors responsible for the decline in its populations. In this paper, we present results from a grassland fire experiment aimed at evaluating the effect of grassland fires on foraging (grasses) and breeding (marshes) habitat use by the Saffron-Cowled Blackbird in a region where fire has been used for centuries as a tool for cattle management. We compare burned grasslands with a control treatment and grasslands within a conservation unit, evaluating uses before and after burning as well as relating bird abundance with environmental characteristics. We found that the Saffron-Cowled Blackbird used the burned treatments more frequently and avoided habitats with tall grasses and developed vegetation. Thus, this species is absent from the conservation unit, which has not experienced fires in nearly three decades. The Saffron-Cowled Blackbird depends on the existence of marshes (breeding habitat) surrounded by short grasses (foraging habitat). In the study region, short grasses are a result of burning practices. As the burning period coincides with the breeding season, the lack of criteria on the part of landowners regarding how to apply and control fire poses a permanent threat to these populations.     

Grassland versus non-grassland bird abundance and diversity in managed grasslands: local,landscape and regional scale effects

Declines of West European farmland birds have been associated with intensive agricultural practices, while in Central and Eastern European countries grasslands still harbour a diverse and unique bird community. However, in these countries comparative studies on the effects of agricultural intensity on biodiversity are virtually missing. We compared bird communities of paired extensively and intensively grazed cattle pastures in three different regions of the Hungarian Great Plain. The influence of grazing intensity, landscape and regional effects were tested on the abundance and species richness of two ecological groups of bird species (grassland and non-grassland birds), as well as on the abundance of the three commonest grassland bird species (Skylark, Yellow wagtail, Corn bunting) in linear mixed models. We found significant effects of grazing intensity on the abundance of grassland birds, which were more abundant on the extensive sites, whereas no effects were found on non-grassland birds. This could be explained by a closer dependence of grassland birds on grasslands for nesting and foraging, whereas non-grassland birds only used grasslands opportunistically for foraging. Landscape effect was shown on grassland bird abundance, but not on non-grassland birds. The regions did affect only the species richness of grassland birds. At species level, the effect of management was significant for the three commonest grassland species, which were more abundant on the extensive fields in all regions. Additionally, on Skylark abundance landscape and regional effects were also shown. These findings suggest that conservation of biodiversity in agricultural systems requires the consideration of landscape perspective to apply the most adequate management.     

Perennial biomass feedstocks enhance avian diversity

Federal mandates to increase biofuel production in North America will require large new tracts of land with potential to negatively impact biodiversity, yet empirical information to guide implementation is limited. Because the temperate grassland biome will be a production hotspot for many candidate feedstocks, production is likely to impact grassland birds, a group of major conservation concern. We employed a multiscaled approach to investigate the relative importance of arthropod food availability, microhabitat structure, patch size and landscape‐scale habitat structure and composition as factors shaping avian richness and abundance in fields of one contemporary (corn) and two candidate cellulosic biomass feedstocks (switchgrass and mixed‐grass prairie) not currently managed as crops. Bird species richness and species density increased with patch size in prairie and switchgrass, but not in corn, and was lower in landscapes with higher forest cover. Perennial plantings supported greater diversity and biomass of arthropods, an important food for land birds, but neither metric was important in explaining variation in the avian community. Avian richness was higher in perennial plantings with greater forb content and a more diverse vegetation structure. Maximum bird species richness was commonly found in fields of intermediate vegetation density and grassland specialists were more likely to occur in prairies. Our results suggest that, in contrast to corn, perennial biomass feedstocks have potential to provide benefits to grassland bird populations if they are cultivated in large patches within relatively unforested landscapes. Ultimately, genetic improvement of feedstock genets and crop management techniques that attempt to maximize biomass production and simplify crop vegetation structure will be likely to reduce the value of perennial biomass plantings to grassland bird populations.     

Vegetation development after a large scale restoration of species-rich grasslands in a Central European floodplain

Large scale restoration using local high-diversity seed mixture combined with turf transfer was applied on ex-arable land in the Morava River floodplain in the western Slovakia in the years 1999–2012. The post-restoration vegetation development was recorded during 12 years after the restoration using floristic records per restored polygons with cover estimation in simple 3-degree scale. Temporal changes in species composition were evaluated by gradient analysis and number of characteristic grassland and ruderal species on restored sites was analysed by general linear models. Species composition changed gradually towards the species composition typical for species-rich floodplain grasslands, but the trajectory was not straightforward and several irregularities were observed. They were probably induced by extreme weather events (drought, floods). The decrease in ruderal species and increase in the number of typical floodplain grassland species were observed, when floodplain grassland species permanently outcompeted ruderal species since 8th year after the restoration. However the development in large scale was slower, than expected from previous small-scale experiments, it is evident, that combination of local seed mixture sowing with a turf transfer is a feasible method for the restoration of species-rich floodplain grasslands from arable land.     

Structure and seasonal dynamics of humid tropical grasslands in Meghalaya,India

Abstract. Four humid grassland communities at three different locations in Meghalaya, India were analysed during 1988 and 1989 for species and life-form composition, diversity and dominance in relation to altitude, soil and prevailing disturbances. Due to the adverse interactive influences of exceptionally high annual rainfall (> 10 000 mm), topography and human interference on soil fertility, the grassland at Cherrapunji, at 1300 m altitude, had a low species diversity (H'= 1.74) and was dominated by three perennial grass species. Similar grasslands, at both higher and lower altitudes on fertile soil and with lower rainfall (ca. 2000 mm), showed higher diversity values (H'= 2.28 at Burnihat and 2.31 at Upper Shillong). The proportion of perennial species and chamaephytes increased with elevation. At the high altitude site a grassland under short-term protection from fires and grazing had a higher species richness, density and basal cover than an unprotected grassland. All grasslands show a clear seasonality, albeit with different patterns, with a maximum in density and basal cover in August. The differences in structure and seasonality are discussed in terms of different levels of stress.