Low-productivity Grassland Research Articles

Decreasing nitrogen deposition rates: Good news for oligotrophic grassland species?

Several studies have found that increased nitrogen (N) deposition leads to a decline in species richness in semi-natural grasslands, mainly due to the loss of species typical of nutrient-poor soils. However, after reaching a peak around 1990, N deposition has decreased in Europe over the last 30 years. In this study, we investigated the changes in species number and composition of semi-natural grasslands during this period of declining N deposition. To this end, we compared the data from the first survey (2001-2005) of 147 grassland sites in Switzerland with those from the third survey (2011-2015). We further analysed the vegetation development of a specific hay meadow from 1992 to 2013. In this grassland, total vegetation cover and the cover of graminoid species decreased, while the cover of oligotrophic species increased. At the 147 grassland sites, total species number decreased at sites with still high levels of N deposition and it tended to increase at sites with low N deposition, i. e. below the critical load for N deposition. The number of oligotrophic grassland species increased at sites with a large decrease in N deposition and strong inclination. Thus, the results of this study indicate that the reduction of N emissions had a measurable positive effect on species diversity in these semi-natural grasslands. Most of the grasslands surveyed appear to be quite resilient against N deposition, i. e. they do not shift to an alternative low diversity state dominated by a few competitive species, and recovery of the species composition as a result of the decrease in N deposition seems possible, especially on steep slopes. Furthermore, the study underlines the importance of regular management of semi-natural, unfertilised, low-productivity grassland to maintain the diversity of oligotrophic grassland species.

Simplifying the complexity of the soil microbiome to guide the development of next‐generation SynComs

AbstractIntroductionMicrobial synthetic communities (SynComs) are commonly commercialised to improve crop yield and restoration outcomes. However, many times, these SynComs are over‐simplistic and are far from being able to unleash the soil microbiome's full potential. This is partially due to the fact that harnessing the full potential of the soil microbiome to fuel new SynComs is highly complex.Materials and MethodsHere, I used a multidisciplinary approach combining data from a global grassland field survey and ecological theory with satellite‐based measurements for aboveground biomass and ‘omics’ to provide an example of how to connect the soil microbiome of real‐world ecosystems with the development of the next generation of SynComs. The same approach could be used to identify individual taxa associated with plant productivity within and across any ecosystem type from local to global scales.ResultsI used a three‐step approach (#1 Dominant taxa + #2 correlation networks + #3 microbe‐function) aiming at identifying individual soil taxa with the potential to promote plant production across contrasting environments. This approach simplified the complexity of the soil microbiome to 0.4% of all investigated taxa, which were positively associated with plant productivity after statistically accounting for other key environmental factors. These taxa are common, ubiquitous and native across contrasting global grasslands, suggesting that they could be used under different soil and climatic conditions, and potentially, under different climate change scenarios. Finally, this study further provides a list of soil taxa associated with high and low productive grassland ecosystems globally.ConclusionThe multidisciplinary approach presented here, along with the use of SynComs, can help unlock the soil microbiome's full potential when aiming to support food production and the restoration of ecosystems under global change.

Promotion of afforestation in New Zealand’s marginal agricultural lands through payments for environmental services

Several payments for environmental services (PES) schemes to promote large-scale afforestation are currently operational in New Zealand. In addition, the country has the only national greenhouse gas (GHG) Emissions Trading Scheme centred on forest carbon credits in the world. These market-based instruments are paramount in promoting the changes in land use required to achieve New Zealand’s GHG-emission targets under the Paris Agreement, as well as to pave the way towards the goal of a low-carbon economy by 2050. We estimated the impacts of PES schemes on the profitability of Pinus radiata forestry to identify low-productivity grasslands where afforestation is likely to financially offset the current land use (i.e., mainly sheep-and-beef farming), under the assumption of constant returns to scale. We find that even without PES, 56% of these agricultural lands present lower economic returns than forestry. When PES are considered, results suggest that, depending on the PES schemes and carbon prices, 77–100% of the low-productivity grassland areas could financially benefit from afforestation. If realized, afforestation of those lands could result in the long-term removal of 1.2–1.5 Pg CO2 from the atmosphere.

Ефективність поверхневого поліпшення гірських схилових луків Карпат

Goal. To determine peculiarities of formation of phytocenoses, productivity, chemical composition, nutritive value, and energy content of grass forages depending on the options for surface improvement of slope meadows of the mountain forest belt of the Carpathians at different modes of use. Methods. General scientific methods (hypotheses, induction and deduction, analogy, generalization) — to select the work program, and special (field, laboratory, mathematical-statistical, calculation) — to conduct researches and their generalization. Results. Surface improvement of cereals and grasses (with 28% share of low-value in feed terms Nardus stricta) low-productive (1.39 t/ha of dry weight) slope grasslands of mountain forest belt of the Carpathians improves their species composition and chemical composition of feed increases the productivity of the land. Share of sowed cereals or legumes increases to 34 – 46%. Under the hay regime the highest efficiency as to the output from 1 ha of dry mass was fixed for reseeding mixtures of grasses on the background of N60P30K60 (4.33 t), for the multi-mow regime — reseeding of white clover on the background of P30K60 (3,71 t), that was, respectively, by 14 and 106% more than in the variants without reseeding, and by 146 and 167% more than in the variants without improvement. Among measures of surface improvement influencing forage quality by chemical composition, increasing the content of crude protein, was the introduction of N60P30K60 or 15 t/ha of manure at multi-mow use, and reseeding of white clover — on the background P30K60. Regardless of the measures of surface improvement the highest content of crude protein, the best energy content, and nutritional value of grass fodder were fixed for multi-mow (simulated pasture) mode of use than for hay-mowing. Conclusions. Surface improvement of meadows of the mountain forest belt of the Carpathians with natural grass by operating factors of the improvement of species composition and quality of grass fodder, as well as an increase of their productivity, is the annual entering of N60P30K60 or 15 t/ha of manure, or N60P30K60 + reseeding of grass mixture (Lolium pratense and Phleum pratense) for hay use, or P30K60 + reseeding of white clover for multi-mow use. The best positive effect ensures the application of mineral fertilizers in combination with the reseeding of perennial grasses.

Wild Seed Harvesting at Mountainous Species-Rich Grassland in Calcareous Italian Alps

Wild harvesting is an efficient option for supplying seed to be used for restoring seminatural grasslands. Several methods are currently used to implement wild harvesting, but few controlled experiments have investigated its efficiency regarding seed amount and number of species collected. A harvesting trial was conducted in a species-rich, low-productivity grassland of the calcareous Italian Alps (1 030 m above sea level [a.s.l.). Three mechanical methods were tested in three replications using a completely randomized block design: green hay (GH), dry hay (DH), and seed stripping (SS) harvesting. The number of fertile shoots, mature seeds, and species collected was recorded and compared with the standing seed yield (SSY). GH, DH, and SS harvested approximately 84%, 70%, and 29% of SSY, respectively. Forbs were harvested more efficiently than grasses in all methods but in most cases at very low seed amounts per m2 due to their low seed density for SSY. No significant difference among methods was found for the number of species collected as mature seeds, but SS, implemented on larger plots, tended to collect more forb species. Comparing the results with those of other experiments demonstrated that the relatively cool temperature of the seed maturation period at the mountain site favored stronger seed retention and therefore increased the GH and DH efficiency but decreased the SS efficiency. In cool mountain areas, wild harvesting from forb-rich grasslands should be more successful by SS implemented on wide areas and several times over the vegetative season. In less species-rich grassland, GH and DH can efficiently collect high seed amounts of the fewer species present, even if implemented over smaller areas.

Nitrogen availability alters rhizosphere processes mediating soil organic matter mineralisation

The intrinsic nitrogen (N) supply capacity of soil is central to understanding the productivity of natural plant communities, and essential in the context of determining optimal fertilization rates for agricultural soils. However, it is largely unknown how nutrient availability affects plant mediated priming effects driving soil organic matter mineralisation and associated N-fluxes. We applied continuous, steady-state 13C–CO2 labelling to Lolium perenne grown in high and low productivity grassland soils to allow quantification of SOM- and root-derived soil CO2 efflux. Nutrient treatments (N, P and K) were applied as repeated additions to soils, and impacts on source partitioned soil CO2 efflux were assessed relative to unamended planted and fallow soils. Plants were clipped to uniform height at weekly intervals. Increasing nutrient availability in both soils resulted in a reduction in plant-mediated SOM mineralisation and clipping of plants greatly lowered root-derived respiration but increased SOM mineralisation. Nutrient addition to fallow systems had no effect on SOM mineralisation in either soil. Plant growth stimulated SOM priming, concurrent mobilisation of N from SOM and subsequent plant N uptake in the high productivity soil. Priming was not observed in the low productivity soil due to its greater inherent organic matter stability, resulting in lowered plant-mediated and basal SOM mineralisation. That addition of nutrients reduced SOM mineralisation in planted systems but had no effect in fallow systems is indicative of nutrient availability specifically altering plant-mediated priming of SOM mineralisation. We suggest that plant-soil interactions mediating priming effects are an important determinant of productivity and that the magnitudes of these effects are modified by nutrient availability and soil-specific controls.

Carbon fluxes of an alpine peatland in Northern Italy

It is widely known that peatlands are a significant carbon (C) stock. Most peatlands are located in boreal and subarctic regions of the northern hemisphere but some occur also at high altitude and, contrary to the first; their contribution in terms of carbon sequestration is far less studied. In the Alps, there are numerous small peatlands, which are threatened by increasing temperatures and an alteration of their water balance. The aim of this study was to investigate the carbon fluxes of a small-scale fen in the Alps over three years (2012–2014).During the study period, the peatland experienced a high interannual variation in weather conditions while it acted as a carbon source based on CO2 emissions (NEE: 180.7±65.2gCCO2m−2yr−1) for all three years. This was mainly due to the short net C uptake period (73±7 days) and high respiration. Ecosystem respiration and summer gross primary production were both very high compared to other peatlands around the world and compared to a nearby low productive grassland. In wintertime, the soil did not freeze, resulting in a slow decomposition of the organic matter. Low methane fluxes were recorded during a 10-month measurement campaign, for a total of 3.2gCCH4m−2 over the December 2013–September 2014 period. Our findings suggest that the interannual variability of temperature and soil water content exert a strong influence on the carbon balance of peatlands of the Alps and that could further worsen depending upon the magnitude of climate change.

Carbon storage potential in size–density fractions from semi-natural grassland ecosystems with different productivities over varying soil depths

Researchers have increasingly recognised a profound need for more information on SOC stocks in the soil and the factors governing their stability and dynamics. Many questions still remain unanswered about the interplay between changes in plant communities and the extent to which changes in aboveground productivity affect the carbon dynamics in soils through changes in its quantity and quality. Therefore, the main aim of this research was to examine the SOC accumulation potential of semi-natural grasslands of different productivities and determine the distribution of SOM fractions over varying soil depth intervals (0–10, 10–20, 20–30 30–50 50–80 and 80+cm). SOM fractionation was considered as a relative measure of stability to separate SOM associated with clay minerals from SOM of specific light densities less than 2gcm−3 (size-density fractionation). Two clay-associated fractions (CF1, <1μm; and CF2, 1–2μm) and two light fractions (LF1, <1.8gcm−3; and LF2, 1.8–2.0gcm−3) were separated. The stability of these fractions was characterised by their carbon hot water extractability (CHWE) and stable carbon isotope composition. In the semi-natural grasslands studied, most OC was stored in the top 30cm, where turnover is rapid. Effects of low productivity grasslands became only significantly apparent when fractional OC contributions of total SOM was considered (CF1 and LF1). In deeper soil depths OC was largely attributed to the CF1 fraction of low productivity grasslands. We suggest that the majority of OM in deeper soil depth intervals is microbially-derived, as evidenced by decreasing C/N ratios and decreasing δ13C values. The hot water extraction and natural δ13C abundance, employed here allowed the characterisation of SOM stabilisation properties, however how climatic changes affect the fate of OM within different soil depth intervals is still unknown.

Challenging the paradigm of nitrogen cycling: no evidence of in situ resource partitioning by coexisting plant species in grasslands of contrasting fertility.

In monoculture, certain plant species are able to preferentially utilize different nitrogen (N) forms, both inorganic and organic, including amino acids and peptides, thus forming fundamental niches based on the chemical form of N. Results from field studies, however, are inconsistent: Some showing that coexisting plant species predominantly utilize inorganic N, while others reveal distinct interspecies preferences for different N forms. As a result, the extent to which hypothetical niches are realized in nature remains unclear. Here, we used in situ stable isotope tracer techniques to test the idea, in temperate grassland, that niche partitioning of N based on chemical form is related to plant productivity and the relative availability of organic and inorganic N. We also tested in situ whether grassland plants vary in their ability to compete for, and utilize peptides, which have recently been shown to act as an N source for plants in strongly N-limited ecosystems. We hypothesized that plants would preferentially use NO3−-N and NH4+-N over dissolved organic N in high-productivity grassland where inorganic N availability is high. On the other hand, in low-productivity grasslands, where the availability of dissolved inorganic N is low, and soil availability of dissolved organic N is greater, we predicted that plants would preferentially use N from amino acids and peptides, prior to microbial mineralization. Turves from two well-characterized grasslands of contrasting productivity and soil N availability were injected, in situ, with mixtures of 15N-labeled inorganic N (NO3− and NH4+) and 13C15N labeled amino acid (l-alanine) and peptide (l-tri-alanine). In order to measure rapid assimilation of these N forms by soil microbes and plants, the uptake of these substrates was traced within 2.5 hours into the shoots of the most abundant plant species, as well as roots and the soil microbial biomass. We found that, contrary to our hypothesis, the majority of plant species across both grasslands took up most N in the form of NH4+, suggesting that inorganic N is their predominant N source. However, we did find that organic N was a source of N which could be utilized by plant species at both sites, and in the low-productivity grassland, plants were able to capture some tri-alanine-N directly. Although our findings did not support the hypothesis that differences in the availability of inorganic and organic N facilitate resource partitioning in grassland, they do support the emerging view that peptides represent a significant, but until now neglected, component of the terrestrial N cycle.

Height and clonality traits determine plant community responses to fertilization

Fertilization via agricultural inputs and nutrient deposition is one of the major threats to global terrestrial plant richness, yet we still do not fully understand the mechanisms by which fertilization decreases plant richness. Tall clonal species have recently been proposed to cause declines in plant species richness by increasing in abundance in response to fertilization and competing strongly with other species. We tested this hypothesis in a fertilization experiment in a low productivity grassland by using a novel experimental manipulation of the presence vs. absence of clonal species and by examining the role of height within these treatments. We found that fertilization decreased species richness more in the presence than absence of clonal species. We also found that only tall species increased in biomass in response to fertilization. In the absence of clonal species, fertilization increased biomass of tall nonclonal species. However, in the presence of clonal species, fertilization decreased tall nonclonal biomass and only tall clonal biomass increased. Fertilization caused almost all short species to be lost in the presence, but not the absence, of clonal species and caused greater declines in the mean and variance of light levels in the presence of clonal species. These results show that the traits of species in a community can determine the magnitude of species loss due to fertilization. The strongly negative effect of tall clonals on species richness in fertilized plots is likely a result of their capacity to decrease light levels to a greater extent and more uniformly than nonclonal species, and thereby drive the exclusion of short species. These results help clarify the mechanisms whereby fertilization decreases grassland plant species richness and suggest that efforts to prevent the loss of species under fertilized conditions may be most effective when they focus on controlling the biomass of tall clonal species.

The Steinach Grassland Experiment: Soil chemical properties, sward height and plant species composition in three cut alluvial meadow after decades-long fertilizer application

The Steinach Grassland Experiment (SGE) is probably the oldest still-running grassland fertilizer experiment in Continental Europe. It was established on an alluvial Alopecurus pratensis meadow in southeast Germany in 1933. The aim of this study was to provide detailed information on this experiment concerning the effects of decades-long nitrogen, phosphorus, potassium, and calcium application (46 treatments in total) on (1) soil chemical properties, (2) sward height, (3) plant species composition, and (4) species richness of vascular plants derived from a field survey in spring 2008.(1) A steep gradient of soil properties was recorded, namely plant-available (Mehlich III) P (14–161mgkg−1), K (82–1018mgkg−1) and Ca (532–3336mgkg−1) concentrations, C:N ratio (6.9–10.4) and pH (H2O) (4.7–7.0).(2) Compressed sward height in the third week of May 2008 ranged from 11cm in the control to 47cm in the limed plot with high N, P, and K application.(3) Although fertilizer application altered the plant species composition, diversification of plant communities was not as high as in the case of fertilizer application on low productive soils in other experiments. This was caused by sufficient nutrients enabling the survival of species adapted to high nutrient availability, even in the unfertilized control. The species composition in productive alluvial grasslands is substantially less affected by fertilizer application than in low productive grasslands.(4) Long-term fertilizer application negatively affected the species richness of vascular plants directly by soil acidification and indirectly by an increase in sward height. The extent to which N application negatively affected species richness was dependent on whether N was applied alone or in combination with other nutrients and whether N application acidified the soil.

Ecosystem resilience despite large-scale altered hydroclimatic conditions

Climate change is predicted to increase both drought frequency and duration, and when coupled with substantial warming, will establish a new hydroclimatological model for many regions. Large-scale, warm droughts have recently occurred in North America, Africa, Europe, Amazonia and Australia, resulting in major effects on terrestrial ecosystems, carbon balance and food security. Here we compare the functional response of above-ground net primary production to contrasting hydroclimatic periods in the late twentieth century (1975-1998), and drier, warmer conditions in the early twenty-first century (2000-2009) in the Northern and Southern Hemispheres. We find a common ecosystem water-use efficiency (WUE(e): above-ground net primary production/evapotranspiration) across biomes ranging from grassland to forest that indicates an intrinsic system sensitivity to water availability across rainfall regimes, regardless of hydroclimatic conditions. We found higher WUE(e) in drier years that increased significantly with drought to a maximum WUE(e) across all biomes; and a minimum native state in wetter years that was common across hydroclimatic periods. This indicates biome-scale resilience to the interannual variability associated with the early twenty-first century drought--that is, the capacity to tolerate low, annual precipitation and to respond to subsequent periods of favourable water balance. These findings provide a conceptual model of ecosystem properties at the decadal scale applicable to the widespread altered hydroclimatic conditions that are predicted for later this century. Understanding the hydroclimatic threshold that will break down ecosystem resilience and alter maximum WUE(e) may allow us to predict land-surface consequences as large regions become more arid, starting with water-limited, low-productivity grasslands.

Landscape dialogues – discussing landscape issues with local people

Summary Human impacts on landscapes pose serious threats to Central European landscapes (e.g. ur ban sprawl, land consumption and loss of landscape diversity and biodiversity) and consequently, influence quality of life as landscapes are a key factor in individual and social wellbeing and affect everybody. Therefore, public participation is an issue of great significance when elaborating visions and action plans for sustainable landscape development. In order to implement participatory discussion of landscape issues, “landscape dialogues” in the Austrian LEADER region Muhlviertler Kernland were organised in the framework of the VItAL LANDSCApES project. The introduced method proved to be an adequate instrument to create awareness and to give local people a forum to elaborate on visions and concrete actions for sustainable landscape development. In the course of the “landscape dialogues”, complex issues of landscape development, e.g. the renewal of village cores, the cultivation of low-productive grasslands, the management of small-structured landscape elements as well as the increase of renewable energy use were addressed and gave impulses in some involved municipalities to continue the discussion in communicative and participatory planning processes within the Local Agenda 21 framework.

Afforestation effects on soil carbon stocks of low productivity grassland in New Zealand

AbstractSoil carbon stock change between two major land uses in New Zealand was measured by sampling paired plots across the boundaries of low productivity grassland and forest planted pre‐1990. The national soil carbon monitoring system uses low productivity grassland as a benchmark to evaluate soil carbon stock change for other land uses. The goal was to validate earlier estimates of the effect of pre‐1990 afforestation and to reduce their level of uncertainty. We selected a set of sites to represent the national stocks of forests planted pre‐1990. Previous studies derived estimates of the land‐use effect on soil carbon for afforestation ranging from +1.6 to −8.5 t/ha to 30 cm depth. For all estimates, the 95% confidence interval spanned zero. Our study used nine of the previous paired‐plot sites and sampled and analysed 21 new sites. The land‐use effect of change from grassland to forest planted pre‐1990 was estimated at −17.4 t/ha. The 95% confidence interval ranged from −10.1 to −24.6 t/ha and did not include zero change. The result supported the soil carbon monitoring system assumption that forests planted pre‐1990 have significantly lower soil carbon stocks than the low‐productivity‐grassland standard. Evidence of stock change occurred in depth increments to 0.2 m but with no significant change for the 0.2–0.3 m increment. This suggests that the sampling depth of 0.3 m was adequate for the estimation of soil carbon stock change.

Realized environmental values of Environmental Fallow policy measure

A novel agri-environment scheme for Environmental Fallow (EF) was introduced in Finland to replace a former obligatory CAP set-aside. Though potentially highly valuable, the ability of the current scheme for delivering the stated objectives of water protection, biodiversity, and soil state is yet to be confirmed. The presentation evaluates the role of the scheme for protection of surface waters and biodiversity based on data from the farmer interviews, field data on vegetation, and land-use register for the regions of Uusimaa, Pohjois-Pohjanmaa and Pirkanmaa. In 2010, over 7% of the agricultural utilized area was enrolled under the scheme with four types of fields: long-term grasslands, and fields sown with meadow plants, game crops or landscape flowers. The scheme has been highly popular among farmers but requires agronomic development of the options to reduce establishment failure, and optimise management for the best environmental output with the least agronomic problems. The potential of the scheme to protect surface waters is marginal since only 10% of EFs is situated near the water courses. The option of fallowing by establishing grassland, or by enrolling existing low productive grassland, was the most popular type of EF. The most biologically valuable meadow type remains rare, and the desired vegetation composition is non stable. The vegetation composition of the EF is more diverse than that under the former set-aside and also differs from that of other non-cropped biotopes such as margins and semi-natural grasslands. Plant species diversity correlated negatively with the reported fertility level of the parcels and therefore establishing grassland and meadow fallows on the least productive parcels is ecologically justified. However, possible targeting of the options according to the landscape setting should be investigated. At the current level, the scheme has succeeded to reverse the fallowing area to its state during the EU set-aside period. However, potential long-term efficiency of the current scheme is likely to be compromised by its untargeted and unbinding nature, and existing agronomic challenges in “sowing for nature”. Without a minimum required area, the scheme totally depends on the current and forecasted profit margin.

Impact of the plant community composition on labile soil organic carbon, soil microbial activity and community structure in semi-natural grassland ecosystems of different productivity

The main objective was to describe the effects of plant litter on SOC and on soil microbial activity and structure in extensively managed grasslands in Central Germany that vary in biomass production and plant community composition. The decomposition of shoot and root litter was studied in an incubation experiment. Labile C and N were isolated by hot water extraction (CHWE, NHWE), while functional groups of microbes were identified by PLFA analysis and microbial activity was measured using a set of soil exo-enzymes. The plant community composition, particulary legume species affected SOC dynamics and below-ground microbial processes, especially via roots. This was reflected in about 20% lower decomposition of root litter in low productivity grassland soil. The CHWE soil pool was found to be a key driver of the below-ground food web, controlling soil microbial processes. Below-ground responses appear to be related to the presence of legume species, which affected the microbial communities, as well as the ratio between fungal and bacterial biomass and patterns of soil enzyme activity. Low productivity fungal-dominated grasslands with slow C turnover rates may play an important role in SOC accumulation. The approach used here is of particular importance, since associated biological and biochemical processes are fundamental to ecosystem functioning.

Long‐term effects of cutting frequency and liming on soil chemical properties, biomass production and plant species composition of Lolio‐Cynosuretum grassland after the cessation of fertilizer application

AbstractQuestion: Is there any effect of cutting frequency and liming on P and K availability in the soil, biomass production and plant species composition after cessation of fertilizer application?Location: Eifel Mountains, SW Germany.Methods: The long‐term Grassland Extensification and Nutrient Depletion Experiment was established on a fertilized and mown pasture (Lolio‐Cynosuretum) in 1993. Treatments were: (1) two cuts per year without liming, (2) two cuts with liming, (3) four cuts without liming, (4) four cuts with liming and (5) continued intensive mowing as the control.Results: From 1993 to 2006, the plant available P concentration in the soil decreased substantially, whereas K concentration decreased only slightly. Biomass production decreased from 7 to 5 t DM ha−1. These trends were affected by cessation of NPK fertilizer application but not by cutting frequency or liming. In 2007, substantial differences in species composition between the control and the two‐cut and four‐cut treatments were recorded, whereas liming had no effect. Higher species richness was recorded in cut treatments compared to the control, but no effects of cutting frequency or liming were observed. Ellenberg indicator values indicated that soil nutrients influenced changes in species composition only marginally.Conclusions: The decrease in productivity and available soil P and K in favor of species richness was not achieved to any greater extent by four cuts than by two cuts, or by lime application. Although species richness slightly increased, we conclude that the restoration of low productive grasslands cannot be achieved by cutting management.

PERTURBATIONS ALTER COMMUNITY CONVERGENCE, DIVERGENCE, AND FORMATION OF MULTIPLE COMMUNITY STATES

Environmental perturbations (e.g., disturbance, fertilization) commonly shift communities to a new mean state, but much less is known about their effects on the variability (dispersion) of communities around the mean, particularly when perturbations are combined. Community dispersion may increase or decrease (representing a divergence or convergence among communities) if changing environmental conditions alter species interactions or magnify small initial differences that develop during community assembly. We used data from an experimental study of disturbance and fertilization in a low-productivity grassland to test how these two perturbations affect patterns of species composition and abundance. We found that a one-time biomass reduction decreased community dispersion, which persisted over four growing seasons. Conversely, continuous fertilization increased community dispersion and, when combined with disturbance, led to the formation of three distinct community states. These results illustrate that perturbations can have differing effects on community dispersion. Attention to the variance in community responses to perturbations lends insight into how ecological interactions determine community structure, which may be missed when focusing only on mean responses. Furthermore, multiple perturbations may have complex effects on community dispersion, yielding convergence or divergence patterns that are difficult to predict based on analysis of single factors.

Drying and rewetting effects on soil microbial community composition and nutrient leaching

The effects of a dry-rewetting event (D/RW) on soil microbial properties and nutrient release by leaching from two soils taken from adjacent grasslands with different histories of management intensity were studied. These were a low-productivity grassland, with no history of fertilizer application and a high-productivity grassland with a history of high fertilizer application, referred to as unimproved and improved grassland, respectively. The use of phospholipid fatty acid analysis (PLFA) revealed that the soil of the unimproved grassland had a significantly greater microbial biomass, and a greater abundance of fungi relative to bacteria than did the improved grassland. Soils from both grasslands were maintained at 55% water holding capacity (WHC) or dried to 10% WHC and rewetted to 55% WHC, and then sampled on days 1, 3, 9, 16, 30 and 50 after rewetting. The D/RW stress significantly reduced microbial biomass carbon (C), fungal PLFA and the ratio of fungal-to-bacterial PLFA in both soils. In contrast, D/RW increased microbial activity, but had no effect on total PLFA and bacterial PLFA in either soil. Microbial biomass nitrogen (N) was reduced significantly by D/RW in both soils, but especially in those of the improved grassland. In terms of nutrient leaching, the D/RW stress significantly increased concentrations of dissolved organic C and dissolved organic N in leachates taken from the improved soil only. This treatment increased the concentration of dissolved inorganic N in leachate of both soils, but this effect was most pronounced in the improved soil. Overall, our data show that D/RW stress leads to greater nutrient leaching from improved than from unimproved grassland soils, which have a greater microbial biomass and abundance of fungi relative to bacteria. This finding supports the notion that soils with more fungal-rich communities are better able to retain nutrients under D/RW than are their intensively managed counterparts with lower fungal to bacterial ratios, and that D/RW can enhance nutrient leaching with potential implications for water quality.

Importance of boreal grasslands in Sweden for butterfly diversity and effects of local and landscape habitat factors

A widespread decline in biodiversity in agro-ecosystems has been reported for several groups of organisms in Western Europe. The butterfly fauna was studied in 60 selected semi-natural grasslands in a coniferous-dominated boreal landscape in south-eastern Sweden. The aim was to investigate how butterfly assemblages were affected by the amount of semi-natural grasslands in the surrounding landscape. Furthermore, we wanted to determine if semi-natural grasslands in boreal landscapes harboured species otherwise declining in other parts of Europe. For each study site, the amounts of semi-natural grasslands in the landscape within radii of 500, 2,000 and 5,000 m were studied. Nine local habitat factors were also recorded. Only the amount of semi-natural grasslands within a 5,000 m radius could explain a significant part of the variation in butterfly composition, but there was no clear relationship between the amount of semi-natural grassland and butterfly diversity. Instead, this study showed that local habitat quality was very important for butterfly diversity at individual sites. Flower abundance, sward height and herb composition were the most important local factors. Patches surrounded by a small amount of semi-natural grasslands had high butterfly diversity, contrary to expectations. This may be explained by the fact that forest habitat provides a matrix with several features suitable for butterflies. The butterfly fauna was rich in species representative of low-productivity grasslands, species that are declining in other countries in Western Europe.