Stronger Short-Term Effects of Mowing Than Extreme Summer Weather on a Subalpine Grassland

Mowing is known to favor plant diversity and influence ecosystem functioning in semi-natural grasslands. This effect could be influenced by climate variability, especially in regions with harsh climate, such as subalpine zones. In particular, short-term extreme weather fluctuations may induce rapid plant responses, affecting in turn the response to mowing. We tested the effects of concomitant summer weather manipulation and mowing on a subalpine grassland in the Central French Alps for two consecutive years. We addressed two questions: (1) How is a subalpine grassland affected by extreme summer weather? (2) Does extreme summer weather alter mowing effects on the grassland plant diversity and functioning? We used a multi-level, integrative approach assessing the responses of six abundant plant species, as well as effects on plant community structure, biomass production, and litter decomposition rates. Extreme summer weather was simulated by increasing summer temperature by 1.1°C, and decreasing summer rainfall by 80%—resulting in a 30% decrease in total annual precipitation. In addition, a heat-wave event was simulated during the first year of the experiment. This weather manipulation was combined with a late-summer mowing treatment (mown vs. unmown). Extreme summer weather mainly increased leaf senescence and decreased plant vegetative growth. Leaf litter decomposition was slowed, but only for species characterized by the fastest rates of litter decomposition. Mowing increased plant diversity by restricting the dominant grass species, thereby favoring subordinates. In the short term, this subalpine grassland was rather resistant to extreme summer weather, whereas mowing cessation remained the main factor affecting its biodiversity.     

Carbohydrate and nitrogen stores in Festuca paniculata under mowing explain dominance in subalpine grasslands

Cessation of traditional management threatens semi‐natural grassland diversity through the colonisation or increase of competitive species adapted to nutrient‐poor conditions. Regular mowing is one practice that controls their abundance. This study evaluated the ecophysiological mechanisms limiting short‐ and long‐term recovery after mowing for Festuca paniculata, a competitive grass that takes over subalpine grasslands in the Alps following cessation of mowing. We quantified temporal variations in carbon (C) and nitrogen (N) content, starch, fructan and total soluble sugars in leaves, stem bases and roots of F. paniculata during one growth cycle in mown and unmown fields and related them to the dynamics of soil mineral N concentration and soil moisture. Short‐term results suggest that the regrowth of F. paniculata following mowing might be N‐limited, first because of N dilution by C increments in the plant tissue, and second, due to low soil mineral N and soil moisture at this time of year. However, despite short‐term effects of mowing on plant growth, C and N content and concentration at the beginning of the following growing season were not affected. Nevertheless, total biomass accumulation at peak standing biomass was largely reduced compared to unmown fields. Moreover, lower C storage capacity at the end of the growing season impacted C allocation to vegetative reproduction during winter, thereby dramatically limiting the horizontal growth of F. paniculata tussocks in the long term. We conclude that mowing reduces the growth of F. paniculata tussocks through both C and N limitation. Such results will help understanding how plant responses to defoliation regulate competitive interactions within plant communities.     

A leachate a day keeps the seedlings away: mowing and the inhibitory effects of Festuca paniculata in subalpine grasslands

Background and Aims

Is the release of allelochemicals by the dominant tussock grass Festuca paniculata responsible for its dominance by inhibiting growth of neighbour grasses in subalpine grasslands? As such a community is also structured by mowing practices, what could be the impact of mowing on allelopathy?

Methods

A design was used that isolated allelopathy from resource competition by separating donor plants (Festuca paniculata) from target plants (F. paniculata, Dactylis glomerata and Bromus erectus). Leachates from donor pots containing bare soil, unmown F. paniculata or mown F. paniculata continuously irrigated target pots containing seedlings. Activated carbon was added in half of the target pots to adsorb potential allelochemicals. C and N analyses of target potting soil were used to test for any effect of treatments on resources. Total phenol concentration was measured in the solutions flowing from donor to target pots.

Results

Festuca paniculata leachates inhibited seedling growth of D. glomerata and B. erectus. Inhibition was correlated with polyphenol concentration, and was not due to resource competition for nitrogen. Mowing the leaves of the donor plants did not significantly increase this inhibition. The activated carbon treatment was not conclusive as it inhibited the seedling growing under control pots with only bare soil.

Conclusions

The results suggest that allelopathy may be at least partly responsible for F. paniculata dominance in subalpine meadows by inhibition of colonization by neighbouring species.Key words: Allelopathy, chemical interference, mowing, activated carbon, polyphenols, Festuca paniculata, Bromus erectus, Dactylis glomerata, subalpine, competition     

Effects of mowing on fungal endophytes and arbuscular mycorrhizal fungi in subalpine grasslands

In French subalpine grasslands, cessation of mowing promotes dominance of Festuca paniculata, which alters plant diversity and ecosystem functioning. One of the mechanisms underpinning such effects may be linked to simultaneous changes in the abundance of fungal symbionts such as endophytes and arbuscular mycorrhizal fungi. In field conditions, mowing reduced the abundance of the endophyte Neotyphodium sp. in leaves of F. paniculata by a factor of 6, and increased mycorrhizal densities by a factor of 15 in the soil. In greenhouse experiments, the mycorrhizal colonization of Trifolium pratense and Allium porrum increased 3- fold and 3.8- fold respectively in mown vs unmown grassland soil. Significantly reduced growth of the two host plants was also observed on soil from the unmown grassland. Such opposite effects of mowing on the two functional groups of fungal symbionts could suggest interactions between these two groups, which in turn could contribute to structuring plant communities in subalpine grasslands.     

Water‐soluble carbohydrates in Patzkea paniculata (L.): a plant strategy to tolerate snowpack reduction and spring drought in subalpine grasslands

• In subalpine grasslands of the central French Alps, cessation of traditional mowing promotes dominance of Patzkea paniculata (L.) G.H.Loos (Poaceae) tussocks, with high biomass but low fodder quality. Mowing limits P. paniculata abundance through the depletion of its water‐soluble carbohydrate (WSC) reserves, which sustain early spring growth initiation. However, the effectiveness of mowing effects is modulated by grassland functional composition, fertilization and climate change, as WSC compounds, and notably fructans, support plant physiological responses to climate stresses such as drought or frost.
• To characterize the mechanisms underpinning the control of P. paniculata under global change, we tested the effects of climate manipulation (combined snow removal and drought) and management (cutting and fertilization) alone or in combination on P. paniculata WSC storage in assembled grassland communities of varying functional composition.
• Management and climate treatments individually decreased seasonal fructan storage, with neither additive nor synergic effects between them, primarily due to the dominance of management over climate effects. Fructan amounts were higher in individuals growing in unmanaged exploitative communities compared to unmanaged conservative communities, regardless of climate treatments, but management overrode these differences.
• Our findings suggest that reduction by combined snow removal and drought of P. paniculata carbon allocation to WSC storage may similarly limit its dominance to that in current mowing practices.

     

Effects of winter mowing on vegetation succession in a lakeshore fen

Abstract. To assess whether winter mowing in wetlands fulfils the aim of preventing succession towards drier communities, 34 permanent quadrats (15 m²) were surveyed annually from 1984–1985 to 2000 within large mown and unmown (control) areas (several ha) in a calcareous lake shore fen (W Switzerland). Three trends were noticed: decrease of aquatic species, spread of Cladium mariscus and establishment of woody species (especially Alnus glutinosa and Frangula alnus). None of these trends was prevented by mowing, but mowing did prevent the accumulation of C. mariscus litter and kept woody saplings small. Succession was generally slow and often occurred in the form of sudden, discrete changes. Plant species richness increased with mowing and remained constant without mowing. Soil disturbance by the mowing machine contributed more to the effects of management on species composition than the periodic removal of biomass. It is concluded that mowing every three years in winter is insufficient to preserve semi‐aquatic communities against succession but sufficient to maintain the plant species richness of a low productive, regularly flooded fen.     

Delimitation of the alliances Caricion firmae (Seslerietalia albicantis) and Seslerion juncifoliae (Seslerietalia juncifoliae) in the southeastern Alps and Dinaric mountains

Abstract

A syntaxonomic and phytogeographic delimitation of the calcareous open sedge swards in the alpine belt of the Alps (Caricion firmae) and subalpine and alpine tussock grasslands in wind-exposed habitats (Seslerion juncifoliae) in the area of the south-eastern Alps and of the Dinaric mountains was performed. Analyses based on hierarchical classification, ordination and chorology clearly showed the distinction between the syntaxa: stands from the Liburnian karst (Mt Sne?nik – SW. Slovenia, Mts Risnjak and Snje?nik – NW. Croatia), Li?ka Plje?ivica and the Velebit mountains belong to the Dinaric alliance Seslerion juncifoliae, whereas stands from the Trnovski gozd plateau (W. Slovenia, north-westernmost part of the Dinaric mountains), although somewhat transitional between the two alliances, and stands from the Alps, were classified in the alliance Caricion firmae. The alliance Seslerion juncifoliae of the Dinaric mountains vicariates Caricion firmae of the Alps.     

Dynamics of common reed (Phragmites australisTrin.) in Swiss fens with different management

Dynamics of common reed (Phragmites australisTrin.) in Central Europe have so far mostly beeninvestigated in connection with studies on reed`die-back' along lake shores. However, there hasrecently been increasing concern about reed expansionat terrestrial sites, such as fens and wet grasslands.In this paper we report on the results of fourseparate studies which monitored reed dynamics inSwiss fens with various mowing regimes over a periodof 4 to 15 years. The first study compared unmownplots with plots mown in winter in a triennialrotation; the second one included unmown plots, plotsmown in summer, and plots mown in winter; the thirdone compared plots mown in June and September withplots only mown in September; the fourth studyinvestigated only plots mown in September. Shootnumber and shoot size were recorded in permanentquadrats. In all studies the performance of P.australisfluctuated without trend or tended todecrease during the period investigated. Thedecreasing tendency concerned shoot size rather thanshoot number, and within a given study it was strongerfor plots with initially taller shoots. The variousmowing regimes did hardly influence these changes.Mowing in winter every three years reduced shoot sizein the year after mowing, but not on the long term.Mowing every year in late summer reduced the shootsize compared with unmown plots on the short term, butthis effect almost disappeared on the long term, aftermowing had become biennial. Mowing in June (inaddition to in September) caused no noticeableeffects. We conclude that other factors (e.g. weatherconditions, competition, or population processes) aremore important than management in determining theabundance of P. australisin the fen communitiesinvestigated here, although long-term effects ofmowing in summer still need more investigation. As apractical consequence it is suggested that at siteswhich are not strongly dominated by P.australis, as most of those investigated here,reducing the performance of this species should notconstitute a major target of nature conservationmanagement, nor can its dynamics be used as anindicator for management success before underlyingcauses are better understood.     

The relationship between soil water storage capacity and plant species diversity in high alpine vegetation

Background: In those alpine regions where growing season precipitation is decreasing due to climate change, the capacity of soils to retain water may become an important factor for the persistence of plant species. However, the importance of soil water storage capacity (WSC) for plant species diversity has not been studied so far.

Aims: We aim to evaluate the relevance of WSC for species diversity of alpine plant communities in relation to temperature and length of growing season.

Methods: Species diversity was determined in 150 plots from a broad range of alpine vegetation types in the calcareous western part of the central Swiss Alps. WSC of soil cores sampled in every plot was determined, as well as rooting zone temperature and snowmelt date. Linear mixed models were used to assess the relationship between environmental data and species diversity.

Results: Species diversity was most strongly and positively related to WSC, followed by mean daily minimum temperature (T_min) of the growing season. Species diversity was significantly related to date of snowmelt only in sites with high WSC and/or T_min.

Conclusions: WSC represents an integrative measure for habitat quality and accounts for differences in species diversity within the study region. In order to understand and predict responses of plant species to climate change in high mountain regions, it may be crucial to also take changes in plant water supply into account.     

Mowing management and density dependence in meadow passerine hatching success

Capsule Improving habitat quality through late or intermittent mowing may increase passerine population density without reducing reproductive success.

Aim To describe the relationship between passerine territory density (TD) and Whinchat Saxicola rubetra and Yellow Wagtail Motacilla flava hatching success, under different management regimes.

Methods TD was defined by the Territory Mapping method in nine sites selected in five French flood plains, in four intermittently mown meadows in Russia and in four additional French sites where mowing was partially postponed. Hatching success was assessed by the observation of prey carrying. Generalized Linear Mixed Models were used to analyse the influence on hatching rates of mowing management, early mowing and TD. Linear Mixed Models were used to study the effect of mowing management on TD.

Results In French early mown meadows, TD affected reproductive success. Higher hatching rates and TD were observed in Russia. Similar results in French study sites with postponed mowing confirmed the influence of mowing management on carrying capacity.

Conclusion In west-European grassland systems, late or intermittently mown patches within or at the edge of meadow areas, with potentially improved invertebrate-prey availability, should help to sustain bird demography and improve the efficiency of current conservation programmes.     

Les pelouses à Festuca paniculata du Tessin (Suisse) dans un contexte Alpin

Vittoz P., Selldorf P., Eggenberg S. and Maire S. 2005. Festuca paniculata meadows in Ticino (Switzerland) and their Alpine environment. Bot. Helv. 115: 33–48.Festuca paniculata (L.) Schinz & Thellung locally dominates montane and subalpine meadows of the Alps and other mountains of southern Europe. Vegetation relevés were carried out in Switzerland and northern Italy to study the site conditions under which Festuca paniculata meadows occur in this part of the Alps, their species composition and phytosociological status, and their relationship to Festuca paniculata meadows described previously from the French Alps (Centaureo-Festucetum spadiceae) and Austrian Alps (Hypochaerido uniflorae-Festucetum paniculatae). The Swiss meadows were found to have a similar ecology to those in France and Austria. They occur mostly between 1600 and 2100 m a.s.l on steep slopes with southern aspect, generally on crystalline rocks, but sometimes on calcareous rocks if soils have been decalcified. The species composition of the Swiss meadows is closer to the Austrian than to the French communities, and we attribute them to the association Hypochaerido uniflorae-Festucetum paniculatae with the new subassociation polygaletosum chamaebuxi. Climate is probably the main factor separating vegetation units in the Alps: the Centaureo-Festucetum spadiceae occurs where summers are dry, whereas the Hypochaerido uniflorae-Festucetum paniculatae occurs where rainfall is not a limiting factor in summer.Manuscrit accepté le 10 février 2005     

Long‐term effects of agri‐environment schemes on breeding passerine populations in a lowland hay‐meadow system

Capsule Mowing postponement in 25% of a meadow system may lead to improved but instable population dynamics in meadow birds.

Aim To monitor the long‐term effects of mowing postponement on the abundance and territory density of meadow passerines in 25% of a 3000‐ha hay‐meadow area in the Saône Valley (eastern France).

Methods From 1993 to 2009, passerine abundance was measured annually in 78 plots using point counts and territory density was assessed in two study areas by Territory Mapping.

Results The programme of mowing postponement led to substantially increased passerine abundance and territory density, with the highest increase detected in Whinchats Saxicola rubetra. No positive trend was observed in Corn Buntings Emberiza calandra. Immediately after the increase in abundance, bird distribution within the study area was not influenced by the timing of mowing. The hatching success, assessed by the systematic observation of food carrying, was negatively influenced by early mowing (<40% recorded when >60% of the meadow area was already harvested on 1 July) or, in late mown areas, by high meadow passerine territory density (<40% when territory density was >10 per 10 ha). Hatching rate was usually higher in Whinchats than in Corn Buntings.

Conclusion By improving meadow passerine breeding outputs and density, mowing postponement led to instable population dynamics with dominance of certain species and density‐dependent breeding success.     

Description of Eucalyptodiplosis chionochloae sp. nov., a cecidomyiid feeding on inflorescences of Chionochloa (Poaceae) in New Zealand

Abstract

A cecidomyiid that feeds on developing seeds in the inflorescences of the New Zealand tussock grasses Chionochloa australis, C. conspicua, C. crassiuscula, C.flavescens, C. macra, C. oreophila, C. pallens, C. rigida, C. rubra, C. spiralis and C. teretifolia is formally described from C. pallens. The new species, named Eucalyptodiplosis chionochloae Kolesik, is the most ubiquitous of flower feeders of Chionochloa. Its larvae do not form galls but feed on the developing seeds in autumn, overwinter as diapausing larvae inside the floret, and pupate then rapidly eclose in summer, sometimes after extended diapause. Methods for rearing adults are described. Based on its morphological characters this species is most closely related to two described congeners that form galls on buds of Eucalyptus trees in Australia. Seed predation by Eucalyptodiplosis chionochloae larvae appears to be the primary driver of the extreme mast seeding (variation among years in flower crops) seen in the host Chionochloa species.     

Plant functional identity as the predictor of carbon storage in semi-arid ecosystems

Background: There is an increasing consensus that ecosystem processes are governed by functional identity and trait variation rather than species richness. Despite its importance, the relative effect of relevant functional traits for carbon storage has remained mostly untested in different bioclimatic regions.

Aims: In this study, different components of functional diversity such as community-weighted means of trait values (CWM), functional trait diversity (Rao’s quadratic diversity), functional richness (FRi), functional evenness (FEv) and functional divergence (FDiv) were used to associate carbon content of above-ground biomass, litter and soil in four bioclimatic regions including warm and cold-steppe, semi-steppe rangelands and oak dry forest in the south-west of Iran.

Methods: Several key important traits highly associated with carbon storage including specific leaf area (SLA), height (H), leaf dry matter content, leaf nitrogen and phosphorus content (LNC and LPC), leaf longevity, wood specific gravity and life form were determined to quantify single and multiple traits that contribute to different components of plant functional diversity.

Results: The results showed that CWM of H, Chamaephyte life form, LNC and LPC were among the most important aspects of functional diversity that positively predicted carbon storage in above-ground biomass and soil. We also observed the negative association of carbon storage with FEv of LNC, Rao of LNC and FEv of multiple traits in the rangelands and the negative association of carbon storage with FDiv of SLA in the forest.

Conclusions: Our results indicate that different components of functional diversity are essential for a mechanistic understanding of the role of plant diversity for carbon storage. The negative associations between FDiv and FEv and carbon storage do not provide support for the complementarity niche hypothesis. Our results suggest that in the more functionally diverse ecosystems dominated by functionally important species with key traits, the so-called functional identity does indeed promote carbon storage, at least in these semi-arid ecosystems.     

The effect of extreme weather events on breeding parameters of the White Stork Ciconia ciconia

Capsule Although the White Stork avoids adverse weather conditions by modifying its arrival and breeding, it cannot avoid extreme weather events during the breeding season.

Aims To show how extreme weather conditions can influence breeding attempts of a large, long-lived species, the White Stork.

Methods We analysed data on arrivals of White Storks in Western Poland from 2005 to 2013 and detailed breeding biology parameters from 2009 to 2013 in relation to weather conditions. We analysed breeding success and breeding failure rate from 1974 to 2013.

Results In years with a cold March White Storks arrived later than when March was warmer. Frost during incubation negatively influenced the hatching success. Extreme weather events caused high late mortality even for nestlings older than 30 days. Data from 27 breeding seasons showed a significant increase in mean breeding success but also a significant increase in the proportion of pairs which lost broods in the nestling stage.

Conclusion The White Stork can modify its arrival in response to current weather conditions on the breeding grounds but it cannot respond to extreme weather events. Due to increasing frequency of extreme weather events caused by climate change, White Stork breeding success may decrease in the future.     

Uptake,accumulation and phytoextraction efficiency of cesium in Gypsophila paniculata

Abstract

To evaluate the phytoextraction efficiency of Gypsophila paniculata from Cs-contaminated soils and analyze the mechanism of Cs accumulation in G. paniculata, we analyzed the characteristics of Cs bioaccumulation and subcellular distribution, in addition to its chemical forms in the plant under hydroponic conditions. The results showed that total Cs content in the aboveground parts and the entire plant were as high as 6137.32?mg·kg^?1?dry weight and 7338.49?mg·kg^?1?dry weight, respectively, after 17?days in the 50?mg·L^?1 Cs treatment. The BCF was between 2.35 and 3.38. The TF was between 1.00 and 2.46 in G. paniculata. Subcellular distribution of Cs in the plant was as follows: soluble fraction?>?cell wall?>?organelles. Inorganic Cs (F-ethanol) and water-soluble Cs (F-dH2O) were the main types of Cs in G. paniculata. Further studies show that the phytoextraction efficiency can reach 10.30–11.91% planting a season of G. paniculata under potted conditions. The results suggested that G. paniculata, a perennial, drought-tolerant herb, was a high-accumulator of Cs, which may have potential uses in phytoremediation of Cs-contaminated soil.     

Competitive effects of herbaceous vegetation on tree seedling emergence,growth and survival: Does gap size matter?

Question: What is the effect of gap size on the seedling emergence, growth and survival of four common tree species in wooded pastures? Location: A pasture in the Jura mountains, Switzerland. Methods: Seeds were sown in a complete three‐way factorial design with eight blocks in May 2003. Each block consisted of a competition treatment (four gap sizes including zero) and a mowing treatment (mown and unmown). Emergence, survival and total biomass of tree seedlings of three species (Picea abies, Acer pseudoplatanus and Fagus sylvatica) were measured. A fourth species (Abies alba) failed to germinate. Results: Gaps had a positive influence on the early stages of tree development for all species. Larger gaps favoured growth and survival more than small gaps. Seedling growth was higher when vegetation around the openings was mown. Mowing the vegetation at gap size zero enhanced both growth and survival compared to unmown vegetation. Mown gaps larger than zero had increased seedling desiccation but decreased seedling predation. Species showed similar trends in their emergence and growth responses to gap size and mowing treatments but for Picea emergence rate was higher and survivorship was lower than for Acer and Fagus. Conclusions: Gap size does matter for tree seedling success but even in more favourable large gaps only a small percentage of seedlings emerged and survived. The effects of gaps on tree seedling establishment are complex as a result of interactions between biotic and abiotic changes caused by gaps.     

Adding ecology into phylogeography: ecological niche models and phylogeography in tandem reveals the demographic history of the subalpine warbler complex

Capsule: This study documents evidence of interglacial refugia during the Last Interglacial for birds in the Mediterranean region, and emphasizes the importance of the Last Interglacial on the geographic distribution and genetic structure of Mediterranean species.

Aims: We focused on the historical biogeography of the subalpine warbler complex: Subalpine Warbler Sylvia cantillans and Moltoni’s Warbler Sylvia subalpina; we tested if this Mediterranean bird complex shared a similar demographic fate as the present-day widespread species in the temperate zones of Europe, through the late Quaternary glacial-interglacial cycles.

Methods: An ecological niche model was developed to predict the geographic distribution of the subalpine warblers under the past (the Last Interglacial and the Last Glacial Maximum) and the present bioclimatic conditions. Additionally, Bayesian Skyline Plot analysis was used to assess effective population size changes over the history of the subalpine warbler complex.

Results: During the Last Glacial Maximum, the subalpine warblers almost reached their current distribution in the Mediterranean region; yet, unlike the widespread temperate bird species, they survived the Last Interglacial in allopatric refugia in the Mediterranean region.

Conclusion: A unique biogeographic pattern was revealed, indicating the importance of the Last Interglacial on current distributional patterns and demographic histories of common bird species in the Mediterranean region. This study suggests that Mediterranean biogeography is far more complex than previously assumed, and so deserves further study and more attention.     

Stazioni Eterotopiche di Saxifraga Incrustata Vest. nel Carso Triestino

Abstract

Two abnormal stands of SAXIFRAGA INCRUSTATA Vest, on the Karst of Trieste. — Near of Trieste there are two dolines (sinkholes), where Saxifraga incrustata occurs. The average height of the zone is 300 m above the sea. This unusual presence of a subalpine plant at so low altitude is to relate to a temperature's decrease owing to a very intensive evaporation. In summer time develops a draft between the opposite sides of the dolines and produces the strong evaporation of percolation water in one case and of the imbibition water of a thick moss layer at the other hand.