Species Composition and Standing Crop Variation in an Unfertilized Meadow and Its Relationship to Climatic Variability during Six Years

Year-to-year variability of species composition and hay yield were investigated during a six-year period (1988-1993) in a traditionally mown meadow of great species richness at Negrentino in southern Switzerland. Climatic parameters (temperature, duration of sunshine, global radiation, precipitation, evaporation, relative moisture) measured at a nearby weather station were calculated for ten-day units and compared to quantitative vegetation data. Yields of the first and second harvest were positively correlated with the mean relative moisture during the first and second growth period. Distinct variation patterns were recognized among the 48 species and interpreted as direct or indirect responses of interacting species to climatic conditions during three periods of the year. The first variation pattern including abundant graminoids reflects a strong direct effect by weather conditions in the first growth period. Species of the other variation patterns responded differently to extreme summer droughts with apparent time-lags. Some species reflect warm and humid conditions in early spring followed by dry conditions in a particular year; others combine features of different variation patterns

Spatial heterogeneity confounded ozone-exposure experiment in semi-natural grassland

Interpretation of observations from manipulative experiments is often complicated by a multitude of uncontrolled processes operating at various spatial and temporal scales. As such processes may differ among experimental plots there is a risk that effects of experimental treatments are confounded. Here we report on a free-air ozone-exposure experiment in permanent semi-natural grassland that suggested strong ozone effects on community productivity after 5years. We tested ozone effects and investigated the potential of confounding due to changes in nutrient management. Repeated-measure ANOVA revealed mainly negative temporal trends for frequency of abundant productive plant species. Constrained ordination additionally showed converging trajectories of species compositions for ozone and control treatments with time. Yields sampled prior to the start of the experiment and soil nitrogen concentrations revealed that spatial heterogeneity in the soil nutrient status was not accounted for by the random allocation of treatments to plots with a bias towards less productive patches in the elevated-ozone plots. Re-analysis of yield data using repeated-measure ANOVA with a covariable to account for productivity prior to the start of fumigation revealed effects on the temporal changes in total yield and yield of legumes that cannot be separated between ozone and pre-treatment nutrient status. Changes in species composition favour an ecological interpretation with spatial heterogeneity as the major cause of different yield declines. Although elevated ozone may cause subtle physiological changes with longer term implications, our new results suggest that species-rich mature grassland such as the one studied at Le Mouret may be less sensitive to elevated ozone than previously assumed. In this experiment a confounded design was hidden at the start by transitory effects of a prior change in nutrient treatment

Positive diversity-invasibility relationship in species-rich semi-natural grassland at the neighbourhood scale

Background and Aims Attempts to answer the old question of whether high diversity causes high invasion resistance have resulted in an invasion paradox: while large-scale studies often find a positive relationship between diversity and invasibility, small-scale experimental studies often find a negative relationship. Many of the small-scale studies are conducted in artificial communities of even-aged plants. Species in natural communities, however, do not represent one simultaneous cohort and occur at various levels of spatial aggregation at different scales. This study used natural patterns of diversity to assess the relationship between diversity and invasibility within a uniformly managed, semi-natural community. Methods In species-rich grassland, one seed of each of ten species was added to each of 50 contiguous 16 cm2 quadrats within seven plots (8 × 100 cm). The emergence of these species was recorded in seven control plots, and establishment success was measured in relation to the species diversity of the resident vegetation at two spatial scales, quadrat (64 cm2) within plots (800 cm2) and between plots within the site (approx. 400 m2) over 46 months. Key Results Invader success was positively related to resident species diversity and richness over a range of 28-37 species per plot. This relationship emerged 7 months after seed addition and remained over time despite continuous mortality of invaders. Conclusions Biotic resistance to plant invasion may play only a sub-ordinate role in species-rich, semi-natural grassland. As possible alternative explanations for the positive diversity-invasibility relationship are not clear, it is recommended that future studies elaborate fine-scale environmental heterogeneity in resource supplies or potential resource flows from resident species to seedlings by means of soil biological networks established by arbuscular mycorrhizal fung

RISE, a Tool for Holistic Sustainability Assessment at the Farm Level

Sustainability must be adopted as a key principle in global markets. Numerous studies have been conducted to evaluate the degree of sustainability on a national and local level. However, only little information for single farm assessment is currently available. The present paper introduces a tool, the "Response-Inducing Sustainability Evaluation" (RISE), which allows an easy assessment at the farm level. It is system-oriented and offers a holistic approach for advice, education and planning. The model covers ecological, economical and social aspects by defining 12 indicators for Energy, Water, Soil, Biodiversity, Emission Potential, Plant Protection, Waste and Residues, Cash Flow, Farm Income, Investments, Local Economy and Social Situation. For each indicator a "State" (S) and a "Driving force" (D) are determined from direct measures of a number of parameters. The "State" indicates the current condition of the specific indicator, higher values are more desirable, and the "Driving force" is a measure of the estimated pressure the farming system places on the specific indicator; in this case lower values are desirable. D and S are standardized on a 0 to 100 scale; a perfect indicator would be identified by S=100 and D=0, whereas significant challenges would be captured by a combination of a low S and a high D. The degree of sustainability (DS) of each indicator is defined as DS= (S-D), bound by construction to the -100 to +100 range. The overall results are summarized and displayed in a sustainability polygon. In addition to this polygon a strength/weakness profile is determined for 1) the stability of the social, economic and ecological framework, 2) farmer's risk awareness and risk management measures, 3) grey energy in machines, buildings and external inputs, 4) animal health and welfare. RISE has been tested and used to evaluate very different farms in Brazil, Canada, China and Switzerland. Results are considered relevant with regard to the objective stated. Further testing, adaptation and fine-tuning is under way. A similar model covering the supply chain to the factory gate is also under development.Sustainability assessment, Sustainability at the farm and crop level, Indicators of sustainability, Driving Force - State - Response (DSR) - model, Environmental Economics and Policy, Farm Management,

The impact of seed deficiency on productivity and on negative drought effect in semi‐natural grassland

Questions Vegetative re‐sprouting and recruitment from seed determine grassland recovery after severe drought, but the mechanisms determining vegetation composition are not fully understood. We ask how the timing of drought and seed availability modify the drought legacy effects on composition and function in a temperate, semi‐natural grassland. Location Negrentino, southern Alps, Switzerland. Methods Under automated rainout shelters, we simulated extreme seasonal drought events in a late summer and in the following spring, added rainwater to simulate normal conditions in no‐drought controls and maintained haymaking at times of normal practice. Towards the end of the summer drought, we added seeds of ten local species in a three‐factor split‐plot arrangement with seven blocks as the replicated unit. We measured fine‐scale variation in soil depth. We assessed the biomass of graminoids and forbs at regular harvesting dates and the species frequencies of established plants and recruits before treatment start, repeating these assessments for three years thereafter. We measured the biomass proportions of post‐drought annual recruit cohorts in year 4 after drought. Results One‐time seed addition augmented recruits, modified species composition and enhanced species diversity; these effects propagated to increased reproductive shoots of recruits and community biomass four years later. Single and repeated seasonal droughts only caused low adult plant mortality but clearly reduced recruitment from seed, while post‐drought establishment was slightly enhanced. Seed augmentation compensated the negative spring drought effect on forb recruits and in turn mitigated the negative impact of drought on species diversity after drought. Conclusions Our experiment shows that seed deficiency limits productivity and that seed deficiency compensation can help to stabilize diversity and productivity in semi‐natural grassland. Releasing the current constraints of management on seed supply in grassland would therefore assist in mitigating negative drought impacts

Year-to-Year Changes in Unfertilized Meadows of Great Species Richness Detected by Point Quadrat Analysis

An experimental study site in an unfertilized meadow of great species richness at Negrentino (820 m) in Southern Switzerland has been investigated by successive point quadrat analysis since 1988. Two different managements, traditional mowing and abandonment, were realized on 3 x 6 plots of 200 x 220 cm. On each plot point frequency (sensu Goodall 1952) was sampled at spaces of 10 cm using the same 11 x 16 points every year. On all the plots 71 species were recorded within the four year period of 1988-1991. Small spatial differences and vegetational changes in time are interpreted on an ordination diagram of correspondence analysis. Differences between successional and fluctuational changes are recognized already in the early phase. On one plot a peak of phytocyclic fluctuation connected with a mass development of Trifolium repens was observed. Many species show significant year-to-year frequency changes. Taxa positively and negatively affected by abandonment are presented. Management and dry weather conditions in April and May are considered to be the main causes of trends and fluctuations

Accurate determination of vegetational change in meadows by successive point quadrat analysis

The point quadrat method can be used for determination of vegetational change in meadows of great species diversity. An appropriate sampling technique is described comprehending an apparatus of high rigidity and a shelter to keep off wind and rain. Sample size related to sampling time expense affects the number of species recorded and methodical error which is empirically determined by repetitive sampling. A setup of fixed points leads to higher accuracy than random sampling. When methodical error is quantitatively known, significant vegetational change can be detected by sampling at successive times

Effects of mowing and removing litter on reproductive shoot modules of some plant species in abandoned meadows of Monte San Giorgio

Reproductive shoot modules have been counted in a permanent plot experiment on Monte San Giorgio (Southern Switzerland) since 1988. The 8 species presented here, including the dominant grass (Molinia arundinacea) and seven locally abundant species, two grasses (Danthonia alpina, Bromus erectus), a sedge (Carex flacca) and four forbs (Centaurea bracteata, Anthericum ramosum, Serratula tinctoria, Inula hirta) changed considerably from year to year. Mowing negatively affected cover and standing crop proportions of M. arundinacea and positively influenced the number of reproductive shoot modules of most species. Removing litter did not affect the cover of M. arundinacea but mainly increased its number of reproductive shoot modules. It is concluded that density of reproductive shoots is very sensitive to weather condi¬ tions and different treatments

Did recent climatic shifts affect productivity of grass-dominated vegetation in southern Switzerland? Evidence from time series of two semi-natural grasslands and a maize field

Time series of crop data from three grass-dominated ecosystems in southern Switzerland were selected for a comparison with climatic variables over the past decades. Standing crop from two permanent species-rich grasslands at Prugiasco and Salorino and the kernel yield of maize planted every year in monoculture at Cadenazzo were measured using standardised methods under controlled conditions in experimental areas over 13 (1988-2000) or 28 (1972-1999) years, respectively. The maize series was corrected for effects of sowing density and genetic variation due to the change of varieties over time. The sensitivity of crop variables to climatic variables, temperature, precipitation, relative humidity and duration of sunshine, recorded at Locarno-Monti, was calculated for 3-month and half-year intervals in 1-yr periods previous to harvest dates. Yields in semi-natural grasslands and in the maize field significantly responded to climatic variables, which were not subject to long-term trends, relative humidity or sunshine, respectively, during the growth period. A series of extremely dry summers negatively affected yields of the maize field and triggered a lagged shift towards a reduced grass-forb ratio in the harvest of the more intensively mown meadow. Dry summers were explained by a lee-effect of upper-level winds blowing from a more northward direction over the Alps in 1989-1991. It is concluded that grass-dominated vegetation in the Southern Alps was more sensitive to changing precipitation patterns than increased temperatures. The vegetation response to climate depended on the methods of human interference