Mowed Grassland Research Articles

Response of grassland greenhouse gas emissions to different human disturbances – A global Meta-analysis

Human disturbances have increased greenhouse gas (GHG) emissions from grassland, worsening global warming. However, the response of grassland GHG (CO2, N2O, and CH4) to human disturbances across various climatic zones requires further elucidation, as does the intricate relationship between GHG emissions and temperature and precipitation. A Meta-analysis of the effects of human disturbances on GHG in grassland over the past 40 years revealed that grazing, fertilization, mowing, and burning significantly influenced the total emissions of N2O, CH4, CO2, and GHG from grassland. However, the light and moderate grazing exerted no substantial impact on CO2 emission flux. In frigid zone grassland, the N2O emission flux was most significantly affected by grazing, the CH4 emission flux affected by fertilization was higher than grazing, and the CO2 emission flux was more sensitive to heavy grazing than severe fertilization. In temperate grassland and savanna, GHG emission flux was most sensitive to fertilization, with CO2 emission flux in savanna being particularly responsive to burning. The effect of increased temperature and precipitation on CO2e in fertilized grassland was approximately double that of grazed grassland and quadruple that of mowed grassland. This study emphasizes the increased effect of human disturbances on GHG emissions in the grassland, especially with the most significant impact of fertilization disturbances on GHG emissions in most grassland areas. Lowering the level of fertilization during grassland management could serve as a crucial step in mitigating GHG emissions from grassland. In summary, rigorous control of disturbance intensity represented an effective strategy for mitigating greenhouse gas emissions, albeit potentially impacting grassland productivity. Future endeavors should focus on determining the optimal disturbance intensity to strike a balance amidst these complex effects.

Environment and management jointly shape the spatial patterns of plant species diversity of moist grasslands in the mountains of Northeastern Yunnan

Grasslands account for about a quarter of the Earth’s land area and are one of the major terrestrial ecosystems, with significant ecological and economic value. The influence of environmental factors and management types on grassland biodiversity has garnered considerable attention. This study investigated how patterns of species richness are influenced by geographical distance, environmental gradients, and management type in the grasslands of northeastern Yunnan, China. We used structural equation modeling to disentangle the impacts of environment and management on phylogenetic community structure, and partial Mantel tests to estimate the roles of dispersal limitation and environmental filtering on taxonomic and phylogenetic beta diversity of three types of grasslands. Our results show that taxonomic alpha diversity increased in grazed grasslands and decreased in mowed grasslands, compared with protected grasslands. However, the phylogenetic structure of both grazed and mowed grassland communities was clustered, whereas that of protected communities was random. Moreover, both grazing and mowing significantly reduced the taxonomic and phylogenetic beta diversity of grasslands, with the lowest values observed in mowed grasslands. Both taxonomic and phylogenetic beta diversity were dominated by species turnover under different management types. The taxonomic and phylogenetic beta diversities of protected and grazed grasslands were simultaneously affected by environmental filtering and dispersal limitation, with the later playing a stronger role. In addition, mowing and related management measures had a stronger filtering effect on grassland community structure, as reflected by changes in community composition.

Arbuscular mycorrhizal fungi reduce ammonia emissions under different land-use types in agro-pastoral areas

Ammonia (NH3) emissions, the most important nitrogen (N) loss, always induce a series of environmental problems such as increased the frequency of regional haze pollution, accelerated N deposition, and N eutrophication. Arbuscular mycorrhizal (AM) fungi play key roles in N cycling. However, whether AM fungi can alleviate N losses by reducing NH3 emissions is still unclear. The potential and mechanism by which AM fungi reduce NH3 emissions in five land-use types (grazed grassland, mowed grassland, fenced grassland, artificial alfalfa grassland, and cropland) were explored in this study. The results showed that AM fungal inoculation significantly reduced NH3 emissions and the mycorrhizal responses of NH3 emissions were determined by land-use type. Structural equation modeling (SEM) showed that AM fungi and land-use type directly affected NH3 emissions. In addition, the reduction in NH3 emissions was largely driven by the decline in soil NH4+-N and pH and the increase the abundances of ammonia-oxidizing archaea (AOA) and bacteria (AOB), urease activity and plant N content induced by AM fungal inoculation and land-use type. The present results highlight that reducing the negative influence of agricultural intensification caused by land-use type changes on AM fungi should be considered to reduce N losses in agriculture and grassland ecosystems.

Extreme wet precipitation and mowing stimulate soil respiration in the Eurasian meadow steppe

The imbalance of terrestrial carbon (C) inputs versus losses to extreme precipitation can have consequences for ecosystem carbon balances. However, the current understanding of how ecosystem processes will respond to predicted extreme dry and wet years is limited. The current study was conducted for three years field experiment to examine the effects of environmental variables and soil microbes on soil respiration (Rs), autotrophic respiration (Ra) and heterotrophic respiration (Rh) under extreme wet and dry conditions in mowed and unmowed grassland of Inner Mongolia. Across treatments (i.e. control, dry spring, wet spring, dry summer and wet summer), the mean of Rs was increased by 24.9 % and 24.1 % in the wet spring and wet summer precipitation treatments, respectively in mowed grassland. In other hand, the mean of Rs was decreased by −22.1 % and −3.5 % in dry spring and dry summer precipitation treatments, respectively in mowed grassland. The relative contribution of Rh and Ra to Rs showed a significant (p < 0.05) change among simulated precipitation treatments with the highest value (76.18 %) in wet summer and 26.41 % in dry summer, respectively under mowed grassland. Rs was significantly (p < 0.05) affected by the interactive effect of extreme precipitation and mowing treatments in 2020 and 2021. The effects of precipitation change via these biotic and abiotic factors explained by 52 % and 81 % in Ra and Rh, respectively in mowed grassland. The changes in microbial biomass carbon (MBC) and nitrogen (MBN) had significant (p < 0.05) direct effects on Rh in both mowed and unmowed grasslands. The influence of biotic and abiotic factors on Rs was stronger in mowed grasslands with higher standardized regression weights than in unmowed grassland (0.78 vs. 0.69). These findings highlight the importance of incorporating extreme precipitation events and mowing in regulating the responses of C cycling to global change in the semiarid Eurasian meadow steppe.

Digestibility and nutritive value of late mowed grassland

Nutritive value of a fodder from extensive established pasture was tested. The nutrient content was measured by the Wendeeanalysis and by in vitro ruminant digestibility method. Results of former experiments showed that the nutritive value of an extensive established pasture in the case of late outdoor growing is low. In our results the highest crude protein content was in the year 2002, while in 2003 can be observed a steep decline, which showed in 2004 further decrease. The crude protein values were the highest in case of middle seed norm. The nutritive values of these pastures provide just supply for the demand and it was declined due to the negative N-balance in the rumen. Our results showed that the samples from the year of establishment could possibly be used for preserved feed (6.01 MJ NE l kg-1). The crop from all other years and sowing times did not reach a value of 5.00 MJ NE l kg-1, but approach a level of 4.4 to 4.5 MJ NE l kg-1, thus they would not be suitable for preserved feed. It can be recommended that this late season crop should rather be used for grazing of livestock than as preserved feed.

Stoichiometric characteristics of different agroecosystems under the same climatic conditions in the agropastoral ecotone of northern China

Ecological stoichiometry affects the processes and functions of ecosystems, but the similarities and differences of stoichiometric characteristics among diverse agropastoral ecosystems under the same climatic conditions remain unclear. In this study, plant and soil stoichiometric characteristics of different agroecosystems, namely natural grassland (free-grazing and mowed grassland), artificial grassland (oat, Chinese leymus and corn silage), field crops (naked oats, flax and wheat) and commercial crops (cabbage and potatoes), were investigated in Guyuan County, China. Results showed total nitrogen (TN), total phosphorus (TP) and N:P ratios in plant tissue varied significantly among ecosystem types (P &amp;lt; 0.05). In general, the mean soil organic carbon, TN and TP content in the 0–0.3 m soil layer in potatoes (8.01, 1.05 and 0.33 g kg–1 respectively) were significantly lower than in other agroecosystems (P &amp;lt; 0.05). The mean C:N ratios of the 0–0.3 m soil layer did not differ significantly among the agroecosystems (P &amp;gt; 0.05). However, the C:P ratio was lower in potato than cabbage sites (24.64 vs 33.17), and was lower at both these sites than in other agroecosystems (P &amp;lt; 0.05). With regard to N:P ratios, only the potato ecosystem had lower values than in other ecosystems (P &amp;lt; 0.05), which did not differ significantly (P &amp;gt; 0.05). Above all, N is more likely to be limiting than P for biomass production in local agroecosystems. Soil C:P and N:P ratios decreased significantly with an increase in the utilisation intensity (from natural grassland to commercial crop). The findings of this study suggest that restoring, preserving and increasing soil organic carbon (especially for cabbage and potatoes), scientifically adjusting the application of N and P fertiliser and enhancing subsidies for low-loss soil nutrient systems, such as grassland, rather than commercial crops will help improve and sustain agroecosystems.

Soil organic carbon changes after deforestation and agrosystem establishment in Amazonia: An assessment by diachronic approach

Abstract Deforestation and agrosystem establishment can alter soil organic carbon (SOC) stocks, leading to greenhouse gases emissions and fertility losses, however SOC response has great variability. In the humid tropics like the Amazonia biome, carbon inputs from agrosystems are rarely quantified and described, despite their major contribution to the SOC dynamics after deforestation. We assessed SOC dynamics with repeated measurements in the layer 0–30 cm until five years after deforestation in a diachronic site in French Guiana, cleared with a fire-free method associated to large woody debris inputs. Three agrosystems were studied: one year maize/soybean rotation with disk tillage (DT) and without tillage (NT), and a mowed grassland (G). Aboveground carbon inputs from agrosystems were measured. In addition to SOC stocks assessment, we measured roots carbon stocks, and performed δ 13 C measurements in grassland soil. We found a transient SOC stock increase until 1.5 years after deforestation because of large woody debris inputs from deforestation method, but these C inputs were rapidly mineralized and poorly contributed to SOC stocks 5 years after deforestation. SOC stocks in grassland did not differ from forest despite large hay exports. Thanks to large root-derived carbon inputs, C4-SOC stock in grassland was 10.4 t ha −1 5 years after deforestation (18.7% of the SOC stock). In annual crops, 5 years after deforestation, SOC stocks decreased on average by 18.6% compared to forest. SOC stocks did not differ according to soil tillage since aboveground carbon inputs were similar in DT and NT systems. Lower SOC stocks in annual crops compared to grassland is explained by lower carbon restitutions and by higher mineralization rate of organic matter.

Habitat fragmentation, vole population fluctuations, and the ROMPA hypothesis: An experimental test using model landscapes.

Increased habitat fragmentation leads to smaller size of habitat patches and to greater distance between patches. The ROMPA hypothesis (ratio of optimal to marginal patch area) uniquely links vole population fluctuations to the composition of the landscape. It states that as ROMPA decreases (fragmentation increases), vole population fluctuations will increase (including the tendency to display multi-annual cycles in abundance) because decreased proportions of optimal habitat result in greater population declines and longer recovery time after a harsh season. To date, only comparative observations in the field have supported the hypothesis. This paper reports the results of the first experimental test. I used prairie voles, Microtus ochrogaster, and mowed grassland to create model landscapes with 3 levels of ROMPA (high with 25% mowed, medium with 50% mowed and low with 75% mowed). As ROMPA decreased, distances between patches of favorable habitat (high cover) increased owing to a greater proportion of unfavorable (mowed) habitat. Results from the first year with intensive live trapping indicated that the preconditions for operation of the hypothesis existed (inversely density dependent emigration and, as ROMPA decreased, increased per capita mortality and decreased per capita movement between optimal patches). Nevertheless, contrary to the prediction of the hypothesis that populations in landscapes with high ROMPA should have the lowest variability, 5 years of trapping indicated that variability was lowest with medium ROMPA. The design of field experiments may never be perfect, but these results indicate that the ROMPA hypothesis needs further rigorous testing.

Are small, isolated prairie remnants effectively smaller than they look and getting smaller?1,2

Abstract To evaluate the floristic sustainability of three small, isolated tallgrass prairie remnants, spatial and temporal patterns of species and functional group (FG) composition, richness, diversity, and dominance were examined to determine whether there was divergence between edge (outer 10 m) and interior zones. These remnants, all protected and managed nature preserves, are rectangular in shape and range in area from 1.29 ha to 1.77 ha; each is bordered by cropland and unmanaged or mowed ruderal grassland. A stratified sampling design was established using permanently marked transects oriented perpendicular to the long axis of each site. Vegetation data were collected in 50 cm × 50 cm quadrats along each transect; prairies were resampled 5–6 yr following baseline data collection. The null expectations were no differences between edge and interior zones, no differences between edge type (crop and noncrop), and no change over time. Results from linear mixed-effects models identified significant diffe...

Effect of dairy manure type on the carbon balance of mowed grassland in Nasu, Japan: comparison between manure slurry plus synthetic fertilizer plots and farmyard manure plus synthetic fertilizer plots

The objective of this study was to compare the carbon (C) balance of mowed grassland that received either manure slurry plus synthetic fertilizers (slurry plots) or sawdust-containing composted farmyard manure plus synthetic fertilizers (FYM plots). Dairy slurry (65.8–66.4 Mg ha–1 year–1) or FYM (36.5–39.2 Mg ha–1 year–1) was applied to a maximum based on a safe potassium content that met the potassium requirement for forage grass production. Ammonium sulfate and superphosphate were additionally supplied to meet the nitrogen (N) and phosphorus requirements. The C inputs to the soil through manure + plant residues (losses during harvesting) and the C outputs from the soil (i.e., respiration) through decomposition of soil organic matter (Rs) + applied manure (Rm) + plant residues (Rp) were monitored for 2 years. Rs and Rm were estimated by using a closed-chamber method with root exclusion. Rp was estimated by using a litter-bag method. Rs averaged 8.2 Mg-C ha–1 per 2 years. Rm accounted for 84% of the applied slurry C (5.5 Mg-C ha–1 per 2 years), and 23% of applied FYM C (9.0 Mg-C ha–1 per 2 years). Rp accounted for 68–70% of plant-residue C (1.0–1.1 Mg-C ha–1 per 2 years) in the slurry and FYM plots. The C balance of the grassland, estimated as C inputs through manure + plant residues minus C outputs through Rs + Rm + Rp, was – 7.0 Mg-C ha–1 per 2 years in the slurry plots and –1.0 Mg-C ha–1 per 2 years in the FYM plots. Thus, FYM application produced a smaller decrease in the soil organic C by 6.0 Mg-C ha–1 per 2 years in comparison with the slurry application. The decomposability of the applied manure therefore depended on the storage conditions, which have an important effect on the C balance (i.e., increment of SOC). Plant residues (i.e., harvest loss) contributed less than FYM to the C balance.

How much do sod-based rotations reduce nitrate leaching in a cereal cropping system?

Nitrogen is essential to improving agricultural production systems, explaining why the contamination of groundwater by this nutrient is widespread. The aim of this paper was to describe data collected over 9 years on estimated leaching levels using a simple computation procedure and measurements of soil water content and water balance, nitrate concentrations in drainage water and meteorological data, and to assess the impacts of the duration of the grassland phase and the level of nitrogen fertilization on grassland on the drainage water quality. The study was carried out at a site of the Long-term Environmental Research Observation and Experimentation facility (SOERE) for Environmental Research- Agro-ecosystems, Biogeochemical Cycles and Biodiversity, run by the INRA experimental unit of Lusignan. The experimental treatments were sequences of maize, wheat and barley with different grassland rotational periods (a pure arable crop rotation; three or six years of grassland receiving high-level nitrogen applications; six years of grassland with a low N application rate and long-term grassland with nitrogen application). The study covered the period from April 2005 to June 2013, during which most drainage occurred in the autumn and early winter. Treatments with the longest duration of grassland exhibited less drainage than those containing a higher proportion of arable crops. The average nitrate concentration was 52.7±38.63mgNO3L−1 under a pure crop rotation, compared to 14.9±14.76mgNO3L−1 under a permanent grassland treatment. There were significant differences (P<0.0001) in cumulative nitrogen leaching between the different cropping systems, ranging from 9 to 37kgNha−1year−1. The introduction of mowed grassland sequences into this arable crop rotation caused a marked reduction in the nitrate levels in groundwater, and the greater the proportion of grassland within the rotation the more markedly was the NO3− concentration reduced, whatever the level of N fertilization during the grassland sequence.

Community disassembly and invasion of remnant native grasslands under fluctuating resource supply

Summary Native vegetation fragments embedded in anthropogenic landscapes are increasingly threatened by land‐use intensification. Managing disturbance regimes and nutrient inputs may help maintain species diversity in such remnants. Yet, it is unclear the extent to which changes in resource availability due to reduced capture by resident plants and/or increased supply rates may trigger native community disassembly and exotic invasions. We examined how mowing disturbance and N fertilizer addition affected plant community recovery after a burning event in a remnant corridor of tussock pampa grassland in Argentina. The percentage cover and richness of native and exotic plant functional groups were monitored over 4 years. According to the ‘fluctuating resource theory’, we expected invasion to be the highest when both light and N availability were increased simultaneously. Mowing delayed recovery by dominant C4 tussock grasses and promoted subordinate, native C3 grasses and exotic legumes, thus enhancing both native and exotic species richness. Fertilization induced a transient increase in native forbs but decreased total plant richness. Moreover, N addition to mowed grassland led to rapid invasion by short‐lived exotic forbs, which were then replaced by exotic perennial grasses. Exotic grasses eventually spread across the grassland corridor, although at different rates depending on the treatment, and in parallel to a generalized decline in native species cover. Synthesis and applications. Community disassembly patterns reflected differential responses of native and exotic functional groups to altered resource supply rates. Synergisms between canopy disturbances and N enrichment posed the greatest threat to preserving a pampa grassland remnant prone to invasion. Establishing buffer zones may be required to enhance the viability of corridor‐like grassland remnants in agricultural landscapes.

Potential of Kentucky Freeway Rights-of-Way to Displace Fossil Fuel Consumption through Production of Switchgrass (Panicum virgatum L.)

ABSTRACT The grassland area of freeway rights-of-way in Kentucky was estimated to determine its potential to produce switchgrass (Panicum virgatum L.) for bioenergy feedstock. Kentucky's freeways include 9.2×103 ha of mowed grassland within their rights-of-way. This area could produce approximately 64×103 t/yr of switchgrass, sufficient to make 21×106 L of cellulosic ethanol, or generate 64 GWh of electricity annually. Switchgrass grown on freeway rights-of-way could offset about 0.5% of fossil fuel currently used on Kentucky freeways if converted to ethanol, or 0.8% if converted to electricity for vehicle propulsion. Future changes in vehicle efficiency and traffic volume will have much greater impact on the volume of fossil fuel used on Kentucky freeways than conversion of freeway-grown switchgrass to alternative fuel. Kentucky's state government's projection of a 42% increase in traffic volume by 2025 contrasts with this study's projection of 28% decline derived from extrapolation of linear trends obse...

Assessing the impact of land abandonment, nitrogen enrichment and fairy-ring fungi on plant diversity of Mediterranean grasslands

Semi-natural calcareous grasslands are of great conservation interest because of their high species richness, but they are threatened by land abandonment and nitrogen eutrophication. These plant communities evolved as a result of a long history of human activity, which generated and maintained these habitats by extensive grazing and mowing. Calcareous grasslands are listed as a priority for conservation in the EC Habitats Directive. However, the effects of different management regimes, nitrogen enrichment, and soil-borne pathogens on plant species diversity are less clear for grasslands of the Mediterranean Basin, compared to meadows in Northern and Central Europe. In this study, we assessed the impact of land abandonment, nitrogen enrichment, and fairy-ring fungi on species diversity in semi-natural grasslands found in the Mediterranean Basin by comparing the available literature with findings from recent studies carried out in Central Italy. In a series of field experiments, the cutting of abandoned grassland consistently reduced the living biomass of the dominant perennial grasses, such as Brachypodium rupestre and Bromus erectus, and promoted a rapid increase in species richness and diversity by allowing the establishment of rare species. There was a similar, but less effective, restoration of species diversity and composition in mowed grassland after litter removal. We also show that nitrogen enrichment at levels comparable to atmospheric deposition depresses species diversity, which also hampers the positive effects of litter removal. Our findings are consistent with previous results achieved in Northern and Central Europe, which however, mainly focused on grasslands with intermediate to high primary productivity levels. The limited availability of data from low-productivity, drought-prone Mediterranean grasslands requires further studies to assess the impact of land abandonment and nitrogen eutrophication in such ecosystems. Finally, we discuss the role of fairy-ring fungi in the maintenance of plant diversity in species-rich grassland. We show that fairy-ring fungi (e.g. Agaricus campestris) critically affect the spatial distribution and diversity of coexisting plant species. By killing the dominant perennial herbs, these radially growing plant pathogens produce empty niches for rare, short-lived species, thus affecting the vegetation pattern. Overall, our results are of interest for environmental managers, as they provide guidelines for the restoration of abandoned areas and the conservation of these species-rich habitats.

Land-use history has a stronger impact on soil microbial community composition than aboveground vegetation and soil properties

The response of soil microbial communities following changes in land-use is governed by multiple factors. The objectives of this study were to investigate (i) whether soil microbial communities track the changes in aboveground vegetation during succession; and (ii) whether microbial communities return to their native state over time. Two successional gradients with different vegetation were studied at the W. K. Kellogg Biological Station, Michigan. The first gradient comprised a conventionally tilled cropland (CT), mid-succession forest (SF) abandoned from cultivation prior to 1951, and native deciduous forest (DF). The second gradient comprised the CT cropland, early-succession grassland (ES) restored in 1989, and long-term mowed grassland (MG). With succession, the total microbial PLFAs and soil microbial biomass C consistently increased in both gradients. While bacterial rRNA gene diversity remained unchanged, the abundance and composition of many bacterial phyla changed significantly. Moreover, microbial communities in the relatively pristine DF and MG soils were very similar despite major differences in soil properties and vegetation. After >50 years of succession, and despite different vegetation, microbial communities in SF were more similar to those in mature DF than in CT. In contrast, even after 17 years of succession, microbial communities in ES were more similar to CT than endpoint MG despite very different vegetation between CT and ES. This result suggested a lasting impact of cultivation history on the soil microbial community. With conversion of deciduous to conifer forest (CF), there was a significant change in multiple soil properties that correlated with changes in microbial biomass, rRNA gene diversity and community composition. In conclusion, history of land-use was a stronger determinant of the composition of microbial communities than vegetation and soil properties. Further, microbial communities in disturbed soils apparently return to their native state with time.

Effects of nitrogen enrichment, plant litter removal and cutting on a species‐rich Mediterranean calcareous grassland

Semi‐natural calcareous grasslands are of great interest in conservation because of their high species richness, but presently they are threatened by both land abandonment and nitrogen eutrophication. The paper reports on a three‐year field experiment conducted in a species‐rich Mediterranean grassland to study the effects of nitrogen application coupled with removal of plant litter and artificial cutting on plant species diversity. Vegetation treatments were applied both to abandoned and adjacent long‐term mowed grassland, to evaluate their restoration value and impact of management abandonment. Cutting significantly increased species diversity in the abandoned area by positively affecting the cover of almost all annual and biennial species and several perennial forbs. Cutting strongly reduced the dominance of perennial grasses. Litter removal had similar effects to cutting, although it was far less effective in increasing species diversity. In the mowed area, cutting abandonment did not reduce species diversity, although the perennial grasses started to increase their cover, while several rare species reduced their abundance. Surprisingly, nitrogen enrichment did not affect species diversity both in the abandoned and mowed area. Our results provided evidence that, within three years, annual cutting can partially restore the species diversity of abandoned grasslands.

Hierarchical tree classifiers to find suitable sites for sandplain grasslands and heathlands on Martha’s Vineyard Island, Massachusetts

The grasslands and heathlands of Martha’s Vineyard Island, Massachusetts provide habitat for unusual, rare, and endangered species. Currently, these globally rare ecosystems exist as fragments on the southern coast of the island within a matrix of wooded, agricultural, and developed land. We used existing land cover patterns to train a hierarchical tree classifier model according to 10 biogeoclimatic and positional variables. This model was then used to predict suitable sites where grasslands and heathlands do not presently occur but could be efficiently established. The tree classifier model indicates that many sites compatible with sandplain grasslands currently contain agricultural lands, residential development, mowed grassland, and commercial development. Efficient establishment could be undertaken at locations buffering existing grasslands to increase their extent by 67% relative to current conditions and join isolated fragments. Sites compatible with heathlands also currently contain agriculture and residential development as well as later successional vegetation including maritime forests and pitch pine. Conversion of these sites to heathlands, as indicated by the model, would increase the current extent by 25% and increase average patch size. An adaptive management approach to grassland and heathland supplementation could be employed to validate the causal mechanisms between the predictor variables and the vegetative communities. Testing of the predictive accuracy of the Martha’s Vineyard Island tree classifier models at other coastal sites would also provide information on the true mechanisms responsible for distribution patterns.

Microhabitat use, giving‐up densities and temporal activity as short‐ and long‐term anti‐predator behaviors in common voles

We used depletable food patches to determine the effect of microhabitat (mowed versus unmowed adjacent grasslands) and time (day versus night) on the foraging behavior of common voles (Microtus arvalis). The food remaining after 12‐h periods (giving‐up density, GUD) measured the vole's habitat selection under predation risk. In accord with several other rodent species and the effects of avian predators, voles had significantly lower GUDs in the unmowed than mowed portion of the grassland. GUDs in patches along the border between adjacent habitats were more similar to the risky mowed grassland than the safe unmowed grass. Time interacted strongly with microhabitat. In the mowed grass, voles had significantly higher GUDs at night than day. Whereas in the unmowed grass, GUDs were significantly higher during the day than night. Vole GUDs did not vary with time along the boundary. This suggests that predators are more abundant or effective in the mowed grass at night (owls?), and in the unmowed grass during the day (weasels?). In terms of predation risk, the voles perceived the mowed grass at night as the riskiest and the unmowed grass at night as the safest. Voles may have difficulties assessing resources under high predation risk: GUDs among patches were well equalized in the unmowed microhabitat whereas in the mowed grass only day GUDs did not vary significantly among patches. We linked these results to the vole's day‐night‐activity and life span. For the 533 voles live‐trapped at the study area, the ratio of day versus night captures for each individual served as an activity index and the span between first and last capture measured minimum life span. In accord with higher GUDs at night, very few individuals behaved selectively towards the night, but individual life expectancy increased with temporal opportunism. Microhabitat differences in GUDs reflect short‐term strategies of predator avoidance and the trapping data reflect long‐term patterns of anti‐predator behavior.

Ruissellement, érosion sur les versants de la France des plaines et des collines. Exemple : Cessières (02 Aisne)

Erosion by runoff of slopes of the plaines and hills of France : example of Cessières On a test-site including a typical sampling of temperate climates of the Bassin de Paris, erosion measures have been made about superficial and hypodermic runoff during a period of 8 years (1977-1984) on the following 3 sites : 5 test parcel units (bare soil), one of which is a mowed grass land, 4 others are under spontaneous grass plots, 3 others under pine-groves (Pinus). These phenomena, as well their quantification and their possible applications, have been proved. Erosion under a very thick temperate forest exists in spite of the interception of about 70% of the atmospheric precipitations (tree-rings 45% vegetal litter 25%) ; erosion is equivalent under spontaneous grass plots, concerning bare soil the runoff rates average 11 % and the denudation zones are about 2,2 mm a year (30 t ha/year). These results of present erosion processes could be directly linked up with historic geomorphology. It is also shown in this paper that in certain conditions hypodermic runoff is more important than the one which affects the surface.