Mesic Grasslands Research Articles

Tree-grass competition along a catenal gradient in a mesic grassland, South Africa

The interaction, both above and belowground, between tree saplings and the surrounding grass sward is dependent on solar radiation, temperature, rainfall, soil depth, tree species and sward composition. These factors, as well as level of sward defoliation, influence whether the system will remain as savanna or move towards a woodland or grassland state. The effects of above- and belowground competition between grasses and two Acacia species and the effects of soil depth on these interactions were examined by planting A. karroo and A. nilotica seedlings into a natural sward on three different soil depths. Three aboveground treatments: full shading, reduced shading by tying back the neighboring grasses and reduced shading by clipping, and two belowground treatments: full and no belowground competition, were used. Plant size increased with increasing soil depth, while belowground competitive intensity was unaffected. Removing belowground competition increased sapling biomass by half (P < 0.05) on all soil depths. By contrast, reduced shading had little effect at all soil depths, whereas sward clipping increased sapling biomass (47%) on shallow soils only (P = 0.027), indicating that encroachment on shallow soils may result from factors that decrease root vigor of the surrounding grasses rather than light competition. Irrespective of soil depth, root competition appeared to be the major factor influencing sapling growth rates, thus grazing management practices that reduce grass root productivity are expected to result in woody encroachment.

Interactive effects of grazing, drought, and fire on grassland plant communities in North America and South Africa

Grazing, fire, and climate shape mesic grassland communities. With global change altering all three factors, understanding how grasslands respond to changes in these combined drivers may aid in projecting future changes in grassland ecosystems. We manipulated rainfall and simulated grazing (clipping) in two long-term fire experiments in mesic grasslands in North America (NA) and South Africa (SA). Despite their common drivers, grasslands in NA and SA differ in evolutionary history. Therefore, we expected community structure and production in NA and SA to respond differently to fire, grazing, and drought. Specifically, we hypothesized that NA plant community composition and production would be more responsive than the SA plant communities to changes in the drivers and their interactions, and that despite this expected stability of SA grasslands, drought would be the dominant factor controlling production, but grazing would play the primary role in determining community composition at both sites. Contrary to our hypothesis, NA and SA grasslands generally responded similarly to grazing, drought, and fire. Grazing increased diversity, decreased grass cover and production, and decreased belowground biomass at both sites. Drought alone minimally impacted plant community structure, and we saw similar treatment interactions at the two sites. Drought was not the primary driver of grassland productivity, but instead drought effects were similar to or less than grazing and fire. Even though these grasslands differed in evolutionary history, they responded similarly to our fire, grazing, and climate manipulations. Overall, we found community and ecosystem convergence in NA and SA grasslands. Grazing and fire are as important as climate in controlling mesic grassland ecosystems on both continents.

English

This paper reports a floristic and phytocenologic review of the mesic and dry grasslands of the southern Iberian System based on numerical and indicator species analysis. The crispness of classification was checked resulting in four main groups that classify grasslands in mesic ( Molinio-Arrhenatheretea and Nardetea ), semi-dry calcareous ( Festuco-Brometea ), dry calcareous ( Sideritido fontquerianae-Arenarion aggregatae ), and dry siliceous grasslands ( Hieracio castellani-Plantaginion radicatae ). DCA and CCA were performed on topographic parameters as explanatory variables of the community diversity and differences in variability between communities were also tested with ANOVA. Rock cover and slope best explained the differences in the floristic composition between the main vegetation groups, and for the discrimination of the dry cryoturbated grasslands ( Sideritido-Arenarion aggregatae ) from other types of grasslands, while altitude best discriminated some associations belonging to the same main vegetation group, such as the semi-dry grasslands ( Cirsio microcephalae-Onobrychidetum hispanicae and Festuco andresmolinae-Brachypodietum phoenicoidis ) and dry grasslands of upfrozen soils ( Festucetum hystricis and Paronychio capitatae-Artemisietum lanatae ) . The exploration of the diagnostic species in combination with the topographic patterns of the community diversity brought out the phytosociological interpretation of transitional communities, like the case of Festucetum hystricis variant of Plantago maritima subsp. serpentina.

Diversity of the Western Carpathian flysch grasslands: Do extremely species-rich plant communities coincide with a high diversity of snails?

Upland fringes of the White Carpathians (Czech Republic) are known to support grasslands with the world’s highest local plant species richness. We investigated whether this unusually high plant richness has a parallel in snail communities, whether patterns of species composition of snail and plant communities in grasslands co-vary and how they are affected by local environment and landscape history. We compared plant and snail communities of dry to mesic grasslands in three neigh bouring regions: (1) hilly lowland of the Central Moravian Carpathians, (2) upland fringes and (3) upland of the White Carpathians. Both snail and plant communities exhibited a strong gradient in species composition associated with altitude, annual temperature and precipitation, soil calcium and pH. However, there was no correlation between local species richness of plants and snails in individual plots. The upland fringes of the White Carpathians were richest in snail species, probably due to intermediate environmental conditions, supporting the occurrence of species with contrasting environmental requirements. The highest local numbers of plant species were also recorded there, although differences among regions were not significant. The regional species richness of plants was also highest in the upland fringes, whereas that of snails was highest in the hilly lowland. Similarities in the diversity patterns of plants and snails among regions suggest the importance of regional factors for local richness, although local abiotic factors, which are partly correlated with the three regions, also influence local species composition and richness.

Evidence of Physiological Decoupling from Grassland Ecosystem Drivers by an Encroaching Woody Shrub

Shrub encroachment of grasslands is a transformative ecological process by which native woody species increase in cover and frequency and replace the herbaceous community. Mechanisms of encroachment are typically assessed using temporal data or experimental manipulations, with few large spatial assessments of shrub physiology. In a mesic grassland in North America, we measured inter- and intra-annual variability in leaf δ13C in Cornus drummondii across a grassland landscape with varying fire frequency, presence of large grazers and topographic variability. This assessment of changes in individual shrub physiology is the largest spatial and temporal assessment recorded to date. Despite a doubling of annual rainfall (in 2008 versus 2011), leaf δ13C was statistically similar among and within years from 2008-11 (range of −28 to −27‰). A topography*grazing interaction was present, with higher leaf δ13C in locations that typically have more bare soil and higher sensible heat in the growing season (upland topographic positions and grazed grasslands). Leaf δ13C from slopes varied among grazing contrasts, with upland and slope leaf δ13C more similar in ungrazed locations, while slopes and lowlands were more similar in grazed locations. In 2011, canopy greenness (normalized difference vegetation index – NDVI) was assessed at the centroid of individual shrubs using high-resolution hyperspectral imagery. Canopy greenness was highest mid-summer, likely reflecting temporal periods when C assimilation rates were highest. Similar to patterns seen in leaf δ13C, NDVI was highest in locations that typically experience lowest sensible heat (lowlands and ungrazed). The ability of Cornus drummondii to decouple leaf physiological responses from climate variability and fire frequency is a likely contributor to the increase in cover and frequency of this shrub species in mesic grassland and may be generalizable to other grasslands undergoing woody encroachment.

Alteration of hydrological processes and streamflow with juniper (Juniperus virginiana) encroachment in a mesic grassland catchment

To understand the effect of woody plant encroachment on hydrological processes of mesic grasslands, we quantified infiltration capacity in situ, the temporal changes in soil water storage, and streamflow of a grassland catchment and a catchment heavily encroached by juniper (Juniperus virginiana, eastern redcedar) in previously cultivated, non-karst substrate grasslands in north-central Oklahoma for 3 years. The initial and steady-state infiltration rates under the juniper canopy were nearly triple to that of the grassland catchment and were intermediate in the intercanopy spaces within the encroached catchment. Soil water content and soil water storage on the encroached catchment were generally lower than on the grassland catchment, especially when preceding the seasons of peak rainfall in spring and fall. Frequency and magnitude of streamflow events were reduced in the encroached catchment. Annual runoff coefficients for the encroached catchment averaged 2.1%, in contrast to 10.6% for the grassland catchment. Annual streamflow duration ranged from 80 to 250 h for the encroached catchment compared with 600 to 800 h for the grassland catchment. Our results showed that the encroachment of juniper into previously cultivated mesic grasslands fundamentally alters catchment hydrological function. Rapid transformation of mesic grassland to a woodland state with juniper encroachment, if not confined, has the potential to drastically reduce soil water, streamflow and flow duration of ephemeral streams in the Southern Great Plains. Copyright © 2013 John Wiley & Sons, Ltd.

Impacts of seasonality and surface heterogeneity on water‐use efficiency in mesic grasslands

ABSTRACTWoody encroachment is occurring in grasslands worldwide, with largely unknown effects on local carbon and water fluxes and the energy balance. Water‐use efficiency (λ) is a measure of carbon assimilation per evapotranspiration. Here, a was compared among three different grassland ecosystems in eastern KS, USA, by using the eddy covariance technique. Variation in λ was examined at multiple timescales and across different burning regimes. Site‐specific variations in λ were more readily observed at seasonal and inter‐annual timescales rather than daily and monthly averages. Annually burned grassland with homogeneous C4 grass cover had less negative values of λ [lower water‐use efficiency (WUE)] than infrequently burned grassland that is presently undergoing woody encroachment and a transition to a shrub‐dominated ecosystem. The most likely explanation for differences in λ are differences in rooting depth and source‐water acquisition between encroaching woody plants and the native grass community. Reliance on a deeper water source by the woody community may buffer the negative consequences of forecasted climate variability and drought, resulting in greater landscape WUE and reduced susceptibility to water stress when compared with the coexisting grass species. Copyright © 2013 John Wiley &amp; Sons, Ltd.

Responses to fire differ betweenSouthAfrican andNorthAmerican grassland communities

AbstractQuestionDoes fire frequency affect mesic grassland plant community structure and composition similarly inNorthAmerica andSouthAfrica?LocationKonzaPrairieBiologicalStation (KNZ),Kansas,USA, and Ukulinga Research Farm (URF), KwaZulu‐Natal, South Africa.MethodsPlant community structure and composition were compared among annually burned, unburned and intermediate treatments within two long‐term fire frequency manipulation experiments in native grasslands in North America and South Africa using comparable methodology over a 5‐yr period. Because fire may reduce soil nitrogen (N) availability and thus affect plant community structure, N additions were superimposed on the fire treatments as a means of assessing direct vs indirect mechanisms driving responses to fire.ResultsThe total number of species was higher atURF(183) than atKNZ(57). Overall divergence in plant community response to fire frequency occurred despite similar responses to nutrient additions. AtKNZ, more frequent fire resulted in dominance by a few, tall, deep‐rooted rhizomatous grasses (e.g.Andropogon gerardii). On unburned sites, shorter, more shade‐tolerant species such asPoa pratensisincreased in abundance, althoughA. gerardiiremained dominant. Species richness increased with decreasing fire frequency atKNZ. AtURF, frequent fire resulted in short, diverse grassland weakly dominated by a range of grass species, includingThemeda triandra,Tristachya leucothrixandHyparrhenia hirta. Decreasing fire frequency reduced species richness and resulted in dominance by a few, relatively tall caespitose grasses such asAristida junciformis. There was a complete turnover of dominant species between annually burned and unburned treatments atURF, while atKNZA. gerardiiandSorghastrum nutansoccurred across the range of treatments. N addition reduced species richness in both sites.ConclusionsDifferent responses to fire frequency betweenKNZandURFare likely linked to the dominant species and their characteristic traits, including height and method of clonal reproduction, with the rhizomatous growth form ofA. gerardiidominating the North American grassland. South Africa does not have an equivalent grass species; instead, a range of tufted, non‐rhizomatous species dominate across the fire frequency treatments atURF. Reductions in soil N due to frequent fire did not appear to be a common mechanism driving responses in community composition in these two grasslands.

Evaluation of the allelopathic potential of five South African mesic grassland species

The recent success of Aristida junciformis Trin. and Rupr. and Eragrostis curvula Schrad. Nees in dominating South African grasslands has posed agricultural and ecological threats. With the objective of examining if the current success of the species is related to allelopathy, the present study assessed the allelopathic potential of five common perennial grassland species (Poaceae). Aqueous extracts prepared by soaking separately 2, 10, 25 and 40 g of leaf and root material in 100 mL of distilled-water for 36 h were bioassayed using a biotest species i.e. Grand Rapids lettuce seeds (Lactuca sativa L. cv.). Species, dilution level and plant-part had a highly significant (P < 0.001) effect on germination percentage, as well as shoot and root elongation of the biotest species. At higher concentrations, the leaf extracts of all species showed significant inhibitory activities which declined with increases in dilution level. A. junciformis, E. curvula and Megathyrsus maximus (Jacq.) BK Simon and SWL Jacobs. demonstrated the highest degree of inhibition in germination percentage and subsequent seedling length; with complete inhibition recorded at dilution levels ≥25 % w/v. At high concentration levels, root extracts of all species, except Themeda triandra Forssk. exhibited significant inhibitory effects on germination; with Hyparrhenia hirta (L.) Staph being most inhibitory. Relatively speaking, E. curvula, A. junciformis and M. maximus showed the highest degree of inhibition. These findings suggest that these three species possess strong allelopathic potential. Such an allelopathic supremacy may contribute to their dominance in natural grasslands. Further studies, however, are still required to isolate responsible phytochemicals and to better understand if allelopathic advantage is the key factor contributing to population dynamics in the field.

Direct and indirect relationships between genetic diversity of a dominant grass, community diversity and above-ground productivity in tallgrass prairie

Question Both genetic diversity within a dominant species and species diversity have been shown to affect productivity. However, these two levels of diversity have the potential to affect productivity in similar or opposing ways. Our study assessed direct and indirect relationships between genetic diversity of a dominant grass species and plant community diversity on productivity within a mesic grassland with naturally co-occurring genotypes and species. Location Konza Prairie Biological Station, Kansas, USA (39°05′35″ N, 96°33′31″ W). Methods We conducted a study at two sites (~65 plots per site) in intact tallgrass prairie that have been subjected to frequent (burned 14 times) and infrequent (burned nine times) fire treatments for ~30 yrs. With frequent burning, the dominant C4 grass, Andropogon gerardii, typically has higher abundance; in contrast, infrequently burned sites typically have higher species diversity but lower abundance of A. gerardii. Therefore, we hypothesized that genetic diversity within A. gerardii would have a significant direct relationship with productivity for the frequently burned site due to higher population abundances of A. gerardii overall, whereas species diversity would have a significant direct relationship with productivity for the infrequently burned site. Results Contrary to our predictions, genetic diversity of A. gerardii was not related to above-ground productivity either directly or indirectly via traits, while diversity at the community level had a negative indirect relationship with productivity via a negative effect of A. gerardii abundance on community diversity for both frequently and infrequently burned sites. Conclusions While much of the focus of diversity–productivity research has been on direct relationships between diversity at the community or population level separately, future studies should examine the indirect and potentially interactive effects of both levels of diversity in natural communities.

Plant Trait Assembly Affects Superiority of Grazer's Foraging Strategies in Species-Rich Grasslands

BackgroundCurrent plant – herbivore interaction models and experiments with mammalian herbivores grazing plant monocultures show the superiority of a maximizing forage quality strategy (MFQ) over a maximizing intake strategy (MI). However, there is a lack of evidence whether grazers comply with the model predictions under field conditions.Methodology/FindingsWe assessed diet selection of sheep (Ovis aries) using plant functional traits in productive mesic vs. low-productivity dry species-rich grasslands dominated by resource-exploitative vs. resource-conservative species respectively. Each grassland type was studied in two replicates for two years. We investigated the first grazing cycle in a set of 288 plots with a diameter of 30 cm, i.e. the size of sheep feeding station. In mesic grasslands, high plot defoliation was associated with community weighted means of leaf traits referring to high forage quality, i.e. low leaf dry matter content (LDMC) and high specific leaf area (SLA), with a high proportion of legumes and the most with high community weighted mean of forage indicator value. In contrast in dry grasslands, high community weighted mean of canopy height, an estimate of forage quantity, was the best predictor of plot defoliation. Similar differences in selection on forage quality vs. quantity were detected within plots. Sheep selected plants with higher forage indicator values than the plot specific community weighted mean of forage indicator value in mesic grasslands whereas taller plants were selected in dry grasslands. However, at this scale sheep avoided legumes and plants with higher SLA, preferred plants with higher LDMC while grazing plants with higher forage indicator values in mesic grasslands.ConclusionsOur findings indicate that MFQ appears superior over MI only in habitats with a predominance of resource-exploitative species. Furthermore, plant functional traits (LDMC, SLA, nitrogen fixer) seem to be helpful correlates of forage quality only at the community level.

The fragility of mesic C4 grasslands in South Africa

The fragility of mesic C4 grasslands in South Africa

Yield and species composition of a mesic grassland savanna in South Africa are influenced by long‐term nutrient addition

AbstractSpecies composition and productivity of natural grasslands are influenced by soil nutrient status. With high resource availability, productivity is expected to increase, and competition is assumed to gain prominence with predicted exclusion of species of lower competitive ability. During 2010 and 2011 we used the dry weight rank method to measure above‐ground phytomass production of herbage in 96 plots (9 m × 2.7 m) fertilized for 60 years with two forms of nitrogen (N as limestone ammonium nitrate or ammonium sulphate at four levels: 0, 7.1, 14.1, 21.2 g m−2), phosphorus (P as superphosphate at two levels: 0, 33.6 g m−2), and lime (two levels: 0, 225 g m−2). Light attenuation was measured as the proportion of photosynthetically active radiation reaching the lower leaf layers of the grasses and the ground surface. Light conditions beneath the grass layer were reduced by nutrient addition to 30% of full sunlight but remained above 60% in non‐fertilized plots. Grass total above‐ground phytomass production increased with nutrient addition. The strongest yield responses were attained with N plus P addition. Species responses showed that Themeda triandra and Hyparrhenia hirta decreased in above‐ground phytomass production with nutrient addition while Panicum maximum, Eragrostis curvula and E. plana increased. These findings are discussed in terms of competitive interactions among species, their position in the grass canopy and their physiological tolerances to high nitrogen environments.

Extreme precipitation patterns and reductions of terrestrial ecosystem production across biomes

Precipitation regimes are predicted to shift to more extreme patterns that are characterized by more heavy rainfall events and longer dry intervals, yet their ecological impacts on vegetation production remain uncertain across biomes in natural climatic conditions. This in situ study investigated the effects of these climatic conditions on aboveground net primary production (ANPP) by combining a greenness index from satellite measurements and climatic records during 2000–2009 from 11 long‐term experimental sites in multiple biomes and climates. Results showed that extreme precipitation patterns decreased the sensitivity of ANPP to total annual precipitation (PT) at the regional and decadal scales, leading to decreased rain use efficiency (RUE; by 20% on average) across biomes. Relative decreases in ANPP were greatest for arid grassland (16%) and Mediterranean forest (20%) and less for mesic grassland and temperate forest (3%). The cooccurrence of heavy rainfall events and longer dry intervals caused greater water stress conditions that resulted in reduced vegetation production. A new generalized model was developed using a function of both PT and an index of precipitation extremes and improved predictions of the sensitivity of ANPP to changes in precipitation patterns. Our results suggest that extreme precipitation patterns have substantially negative effects on vegetation production across biomes and are as important as PT. With predictions of more extreme weather events, forecasts of ecosystem production should consider these nonlinear responses to altered extreme precipitation patterns associated with climate change.

Identifying the water sources consumed by bison: implications for large mammalian grazers worldwide

The sources of drinking water consumed by grazers vary over time and may be highly selective, similar to choices in diet. Water sources consumed by large grazers in natural populations are not typically measured directly. Instead, consumption is inferred based on animal proximity to water sources. Here, we analysed the stable isotopic signature of water (δ18O and δD) extracted from fecal samples from a herd of bison in mesic grassland as a direct estimation of the water sources consumed over time. Bison at this site have their choice of a range of habitats and drinking water sources. Potential source‐water samples measured had a large range of isotopic signatures, allowing the isotopic composition of water from bison fecal samples to be proportionally estimated based on varying sources. Results indicate bison have low reliance on multiple streams on site; rather, the majority of water consumed was from rainfall‐fed sources (puddles and wallows) and from forage. Our research suggests that source‐water analysis from fecal samples is a robust technique when samples from large grazers can be collected soon after production. These results have implications for analyses of the foraging patterns and landscape utilization by this and other large grazers, because hotter and drier future conditions are likely to reduce the frequency and amount of rainfall‐fed puddles available for consumption in many grassland systems worldwide.

Taxonomy, paleoecology and taphonomy of ground sloths (Xenarthra) from the Fairmead Landfill locality (Pleistocene: Irvingtonian) of Madera County, California

The Fairmead Landfill locality contains a diverse middle Irvingtonian, (0.78–0.55Ma), vertebrate fauna that includes three sloths, Megalonyx wheatleyi, Nothrotheriops shastensis and Paramylodon harlani. The co-occurrence of these three genera in a single fauna is relatively rare in both the Irvingtonian and Rancholabrean and this is only the fourth documented Irvingtonian fauna to contain all three sloth genera. The presence of the three different sloths, each of which had different ecological requirements, indicates the presence of a variety of different habitats at this time and a heterogeneous landscape. Preliminary analysis of pollen from the site supports the interpretation of the existence of a mosaic of plant communities, but a landscape dominated by a mesic grassland. This interpretation is also supported by the total faunal diversity that includes taxa associated with woodlands as well as open habitat and taphonomic differences in the preservation and relative abundance of the different sloths. Evolutionarily the Fairmead Landfill sloths show a suite of morphological, size and proportional characters that indicate they represent transitional populations between older and younger members of their respective lineages.

Mixtures with grass litter may hasten shrub litter decomposition after shrub encroachment into mountain grasslands

Shrub encroachment in mesic grasslands alters the identity and quality of litters entering the system. As litter from shrubs and grasses can differ in their quality, this can lead to differences in litter decomposition by the direct effect of quality, but also to litter interaction during decomposition. The objective of this study was to examine the occurrence of non-additive effects of litter mixtures on the decomposition rates of legume shrub litter (poor in P) or conifer shrub litter (poor in N) and grass litter. In addition to single litter type litterbags for the three species, we mixed litters of each pair of possible combinations to determine the influence of each species on mass loss. Litterbags were placed in the field and collected after 1, 6, 8, 12 and 24 months. In each collection, litter of each species remaining in mixed bags was separated, dry weighed and analyzed for C, N and P. With respect to shrub litter decomposing alone, mass loss of shrub litter when mixed with grass showed a 9–10 % increase in decomposition rate for conifer and a 3 % increase for legume litter. These litter mixture effects varied with time and they were detected after a decomposition period of 1 year in legume litter and of 2 years in conifer litter. Grass litter hastened conifer and legume litter decomposition in leaf litter mixtures, at least during the first stages of the process. The potential consequences of this result to alter litter accumulation patterns and thus carbon sequestration rates after shrub encroachment into grasslands will depend on whether the observed trends are maintained in the advanced decomposition stages.

Legacies of precipitation fluctuations on primary production: theory and data synthesis

Variability of above-ground net primary production (ANPP) of arid to sub-humid ecosystems displays a closer association with precipitation when considered across space (based on multiyear averages for different locations) than through time (based on year-to-year change at single locations). Here, we propose a theory of controls of ANPP based on four hypotheses about legacies of wet and dry years that explains space versus time differences in ANPP-precipitation relationships. We tested the hypotheses using 16 long-term series of ANPP. We found that legacies revealed by the association of current- versus previous-year conditions through the temporal series occur across all ecosystem types from deserts to mesic grasslands. Therefore, previous-year precipitation and ANPP control a significant fraction of current-year production. We developed unified models for the controls of ANPP through space and time. The relative importance of current-versus previous-year precipitation changes along a gradient of mean annual precipitation with the importance of current-year PPT decreasing, whereas the importance of previous-year PPT remains constant as mean annual precipitation increases. Finally, our results suggest that ANPP will respond to climate-change-driven alterations in water availability and, more importantly, that the magnitude of the response will increase with time.

Characterizing and evaluating successional pathways of fen degradation and restoration

The definition of restoration targets and the evaluation of restoration success require a comprehensive, ecosystem-based analysis of all successional pathways, which proceed along gradients of land use intensification and continue after implementation of restoration measures. In the presented study, such analysis was applied to fen ecosystems. Study areas were river valleys and eutrophic lakes in The Netherlands and in Schleswig-Holstein, the northernmost state of Germany. At these sites high fen degradation has taken place and restoration strategies such as “recovery of peat-forming systems” and “development of species-rich fen grasslands” have recently been pursued. Based on an indirect successional analysis, we derived characteristic shifts of abiotic (hydrodynamics, soil parameter) and biotic (species composition, phytomass production) ecosystem traits relative to increasing land use intensity. Species richness and nature conservation value (NCV) initially increased and afterwards decreased during the process of land use intensification. This floristic change was accompanied by an initial decrease and subsequent increase in system productivity. Indicators for P-availability showed the same trend and there was evidence that nutrient limitation changed initially from N- (tall sedge reeds) to P- or P/N (co)-limitation (small sedge reeds) and afterwards again to N-limitation (wet and mesic grasslands). The successional analysis documented the abiotic requirements of vegetation types and their characteristic species, and thus, allowed for the use of these ecosystem traits as indicators to evaluate the success of specific restoration targets. For example, the decrease of Scheuchzerio-Caricetea species could be related more directly to reduced light availability than to an increase of the groundwater tables. Furthermore, we calculated threshold values of these traits for the occurrence of target species. For instance, a sustainable establishment of light-demanding mesotrophic species can only be expected if the standing crop value is less than 400gm−2. In a further step, we estimated the restoration success in selected study areas by applying the findings of the successional analysis. Results showed that rewetting measures have to be carried out with caution if both restoration strategies are aspired in one specific area. Moreover, restoration success of both strategies is limited in initially highly degraded areas. Sources for target species are often missing and abiotic conditions such as nutrient levels and flooding periods are often inappropriate. Consequently, expectations for restoration success should be adapted to the realistic development potential of the individual system and a cost–benefit analysis has to be carried out to avoid unnecessary management costs.

Semi-natural Grassland Vegetation Database of Latvia

The Semi-natural Grassland Vegetation Database of Latvia (GIVD ID EU-LV-001) was first developed in 1999 as part of the PhD Thesis on syntaxonomy and diversity of dry and mesic grasslands of Latvia. The database includes the original releves established by the author as early as 1997. The majority of releves belongs to the Filipendulo-Helictotrichion (Festuco-Brometea) and Arrhenatheretalia communities, but Molinietalia, Nardetalia, Caricion nigrae, Koelerion glaucae and Plantagini-Festucion are covered, as well. The total number of releves stored is 2,500 and there are approximately 700 releves to be digitised. Plot size varies from 1 to 125 m, the majority of releves are 4-9 m large. Releves contain records of vascular plants, bryophytes, and lichens (excl. non-terrestrial taxa) percentage cover values. The database holds information on geographic localisation, slope inclination and aspect, management type, soil type etc. Part of the releves are included in the large-scale database: Dry Grasslands in the Baltic and Nordic Region. Several publications are based on the database dealing with Latvia’s vegetation classification at regional and local scale and with long-term changes of vegetation. The Laboratory of Geobotany at the Institute of Biology of the University of Latvia is planning to develop a joint database of vegetation of Latvia and the current database will be a part of that database.