Summer Mowing Research Articles

Traffic intensity and vegetation management affect flower‐visiting insects and their response to resources in road verges

Abstract Road verges can support high densities of flowers and could therefore provide new opportunities for the conservation of flower‐visiting insects. One way of optimizing road verges for vascular plant diversity is to adjust mowing regimes, but to date it is unclear how this affects flower‐visiting insects. Furthermore, for mobile organisms like wild bees and butterflies, there is a risk that the benefit of increased habitat quality in road verges is limited by the proximity to traffic, but this is poorly studied. In a crossed study design, we separated mowing time and frequency (early summer and autumn, or only late summer) from road verge habitat classification (valuable for biodiversity according to transport authority, or regular). We did so along a gradient of traffic intensity, to investigate if a mowing regime designed to enhance plant diversity can also benefit wild bees and butterflies, and if traffic limits the conservation potential of road verges. Road verges that were mown only in late summer had higher flower densities, and there was a positive relationship between flower density and wild bee abundance and species richness. Butterfly abundance and species richness only benefitted from a late summer mowing in valuable but not in regular road verges. Traffic intensity had a substantial negative impact on abundance and species richness of wild bees and butterflies. Higher traffic intensities limited the positive relationship between plant and butterfly species richness that we observed at lower traffic intensities. Increasing width of the road verges buffered negative effects of the traffic on wild bee as well as butterfly abundances, and on wild bee species richness. Synthesis and applications. Road verges can play a valuable role for the conservation of wild bees and butterflies, but there is a need to consider both traffic intensity and resource availability when implementing management strategies. To support wild bee and butterfly diversity, we recommend actions to enhance plant species richness and flower resource availability, and to focus these conservation efforts on roads with low traffic intensity, or on wide road verges.

Reversing expansion of Calamagrostis epigejos in Carpathian mountain grasslands by mowing and application of hemiparasitic Rhinanthus alectorolophus

AbstractQuestionsThe expansion of Calamagrostis epigejos poses a significant threat to the biodiversity of mountain grasslands. We asked whether grasslands dominated by C. epigejos can be restored through mowing and the application of hemiparasitic Rhinanthus alectorolophus.LocationCarpathian Violion caninae alliance mountain grassland close to Vrchslatina, Veporské vrchy Mts, Slovakia.MethodsWe conducted a before–after control–impact experiment in a grassland entirely dominated by C. epigejos: six blocks, each with four treatment combinations: (i) mowing once in summer, (ii) mowing in summer and autumn, (iii) mowing in summer and seed sowing of R. alectorolophus, (iv) mowing in summer and autumn along with seed sowing of R. alectorolophus. We monitored the above‐ground biomass of C. epigejos, R. alectorolophus, the combined above‐ground biomass of other species, and the vegetation composition annually from 2014 to 2017. Linear mixed‐effect models and redundancy analysis (RDA) were employed to analyze the effects of the treatments on C. epigejos and community parameters.ResultsSowing established R. alectorolophus at the plots mown twice in the first year, but its density strongly declined in subsequent years. R. alectorolophus and mowing twice significantly reduced C. epigejos biomass and herb layer cover. They also increased community evenness and the ratio between other species and C. epigejos biomass with a more pronounced effect on the plots where R. alectorolophus was applied. Mowing twice led to increased species richness, evenness, the number of target grassland species and their proportion in the community. R. alectorolophus had an additional positive impact on community evenness and the proportion of target species. RDA identified R. alectorolophus as the main driver of the directional community change triggered by the experimental treatments.ConclusionMowing twice per season proves to be an efficient restoration management strategy for mountain grasslands dominated by C. epigejos. Sowing R. alectorolophus, however, may be employed as an additional measure to accelerate the decline of C. epigejos at the outset of the restoration process and enhance community structure and composition.

Study of the Effect of Mowing and Drying on the Lipid Composition of Grass Leaves in Permafrost Ecosystems

Mowing the plant shoots under hot, sunny, and dry conditions severely traumatizes the entire vegetative body, and the overall life cycle of the plant is altered. The purpose of the present research was to investigate the effects of mowing and drying on lipids, fatty acids (FA), sterols, and the systemic responses in leaves of plant material at three time points (24 h, 72 h, and leaves of new shoots after traumatic mowing in summer (1 July) and those subjected to cold hardening by autumn temperatures in September (aftergrass)) were analyzed for the first time. The leaves of five species of herbaceous plants growing in permafrost ecosystems were analyzed by HPTLC and GC-MS. It was established that fatty acids in the tissues of aftergrass leaves were characterized by higher values of the n-6/n-3 ratio than in summer grasses. It was demonstrated that exposure of leaves for 72 h in natural conditions in summer and at low temperatures in autumn in leaves of aftergrass resulted in significant changes in the composition of membrane phospholipids. The obtained findings indicate that leaves of aftergrass are the most valuable plant raw material in terms of FAs and phytosterols content compared to hay mowed in summer.

Long-term subtropical grassland plots take a long time to change: Replacement is more important than richness differences for beta diversity.

We studied β diversity of grasses in a subtropical grassland over 60 years in South Africa. We examined the effects of burning and mowing on 132 large plots. We sought to determine the effects of burning and mowing, and mowing frequency, on the replacement of species and the species richness. We conducted the study at Ukulinga, research farm of the University of KwaZulu-Natal, Pietermaritzburg, South Africa (29°24'E, 30°24'S) from 1950-2010. Plots were burned annually, biennially, triennially, and a control (unburned). Plots were mowed in spring, late summer, spring plus late summer, and a control (unmowed). We calculated β diversity, with a focus on replacement and richness differences. We also used distance-based redundancy analyses to examine the relative effects of replacement and richness differences on mowing and burning. We used beta regressions to test for the effect of soil depth and its interactions with mowing and burning. There was no significant change in grass beta diversity until 1995. Thereafter, there were changes in β diversity that demonstrated the primary effects of summer mowing frequency. There was no significant effect of richness differences but a strong effect of replacement post-1995. There was a significant interaction between mowing frequency and soil depth in one of the analyses. Changes in grassland composition took a long time to manifest themselves and were unapparent prior to 1988. However, there was a change in sampling strategy prior to 1988, from point hits to nearest plants, that may also have influenced the rates of changes in replacement and richness differences. Using β-diversity indices, we found that mowing was more important than burning that burning frequency was unimportant, and there was a significant interaction effect between mowing and soil depth in one of the analyses.

People prefer arable fields and flower strips with continuous soil cover and diversified vegetation

Agriculture is a key driver of the dynamics and transformation of rural landscapes in Western Europe. However, little is known about the influence of cropping techniques on visual perceptions of the aesthetic and ecological value of agricultural fields. We used an online survey to investigate the preferences of French residents for fields of contrasting appearances due to different cropping systems. Participants were shown photographs taken at four periods of field management (i.e., fallow period, seedbed preparation, recommencement of plant growth after winter, and end of the cycle crop), either alone or in combination with temporal sequences typical of organic, conservation, and conventional cropping systems. The perception of flower strips across the seasons was also evaluated according to three levels of diversity and two management options (with and without summer mowing). Agricultural fields with high degrees of soil cover (e.g., presence of a cover crop, narrow inter-rows) and diversified vegetation (e.g., intercrop, weeds) were perceived as more aesthetic and favorable for biodiversity. The temporal sequences reflecting visual appearances of cropped fields under conservation agriculture were considered more aesthetically appealing and favorable to biodiversity than those for organic or conventional agriculture. Participants ranked wildflower strip sequences in descending order of plant species diversity. Within diversity levels, strips not mown in summer were preferred over those mown in summer for both aesthetic and biodiversity preservation value. These results could provide the basis of a design for payments for environmental services, including the socio-cultural services provided by agroecological cropping systems.

Use of remote sensing and bio-geochemical models to estimate the net carbon fluxes of managed mountain grasslands

The current paper presents a methodology which can simulate the net carbon fluxes of semi-natural grasslands based on the combination of a parametric and a bio-geochemical model. The first model (modified C-Fix) estimates grassland gross primary production (GPP) by driving the light use efficiency approach with remotely sensed normalized difference vegetation index (NDVI) data. The latter model (BIOME-BGC) simulates all main ecosystem processes based on meteorological and ancillary data. The outputs of the two models are finally combined and corrected for the effects of human-induced biomass changes (i.e. mowing, grazing, etc.). The modelling strategy, fed with ancillary and MODIS NDVI data, is tested in two semi-natural grasslands, the first (Amplero) on the Apennines and the second (Monte Bondone) on the Alps (Central and Northern Italy, respectively). The two sites, which show diversified eco-climatic conditions and are managed differently (i.e. Amplero by spring mowing plus cattle grazing and Monte Bondone by summer mowing), were selected for the availability of eddy covariance observations of GPP and net ecosystem production (NEP) collected during several years (from 2003 to 2012). These observations were used to assess the estimates of the modelling strategy, obtaining promising results for both study sites. The greatest estimation errors are found in the Alpine site and are mostly induced by the inaccurate detection of local grassland NDVI values, which is due to the insufficient spatial and temporal resolutions of the used MODIS NDVI imagery. The results of the study highlight the importance of information on the local management practices applied, which is decisive for quantifying medium-term changes in net carbon fluxes.

Сезонная динамика содержания липидов и жирных кислот в тканях злаков Avena sativa и Bromopsis inermis

Yakutia is a zone of continuous permafrost distribution, and its uniqueness lies in the fact that it has a kind of hidden biological resource that allows herbivores to survive even in conditions of limited floristic diversity. The current paper focuses on the disclosure of this resource, which we believe is in the nutritional value of permafrost plants. We have studied the content of total lipids and their essential polyunsaturated fatty acids in summer and autumn vegetative plants. According to the goal stated, we have pioneered the use of thin-layer and gas-liquid chromatography and mass spectrometry to show seasonal changes in the content of total lipids and their essential polyunsaturated fatty acids in the following plants: annual Avena sativa L. of standard and late sowing dates, and perennial Bromopsis inermis Leys before and after summer mowing in the conditions of Central Yakutia. Artificial shortening of the vegetation period of grasses has led to their preservation by natural cold (green cryo-feed). We have found that an increase in the amount of lipids in cereal plants occurs with the onset of low hardening air temperatures in the autumn period, in particular, a significant increase in linoleic С18:2(ω-6) and α-linolenic С18:3(ω-3) acids compared with indicators of summer vegetative plants. The detected process may indicate an increase in the energy intensity of frozen feed, thereby determining the important role of cryo-feed for pre-winter fat accumulation in herbivores in the cryolithozone. In the body of animals, soluble sugars of autumn vegetative or winter-green plants growing or frozen by natural cold and used as autumn and winter feed are converted into medium- and long-chain essential polyunsaturated fatty acids of the omega-6 and omega-3 families (arachidonic, and eicosapentaenoic and docosahexaenoic acids, respectively) and to a large extent help to winter. The use of grown green cryo-feed as a vitamin supplement for farm animals during a long stall period will open up new opportunities in increasing the productivity of livestock breeding in Yakutia in the future and help optimize the flow of substances and energy along the trophic cryo-feed – animal – human chain. Essential PUFAs, namely linoleic and α-linolenic acids, play an essential role in health and prolonging human life.

Buried but unsafe – Defoliation depletes the underground storage organ (USO) of the mesic grassland geophyte, Hypoxis hemerocallidea

Mesic grasslands in South Africa (> 650 mm a − 1 MAP) are rich in herbaceous forbs, which outnumber grass species by more than 5 to 1. Many of these forbs are geophytes with underground storage units (USOs), such as thickened rootstocks, rhizomes, bulbs, or corms, that provide resources (non-structural carbohydrates, minerals, and water) enabling them to resprout after dry, frosty winters, and fire. However, despite their extensive biomass and reserves ostensibly protected underground, mesic grassland geophytes can be severely depleted or extirpated by chronic trampling and grazing of their aerial parts by livestock. This study examined a possible explanation for the demise of grassland geophytes in overgrazed grassland by investigating, in a pot trial, whether the growth of a geophyte and the size of its USOs are negatively affected by simulated green leaf loss. In a 2 × 2 factorial (clipped vs. unclipped x spring regrowth in the dark vs. light), five replicate plants of Hypoxis hemerocallidea, a common mesic grassland geophyte that resprouts from a corm, were subject to six severe (clipped to 80 mm) defoliations during the growing season and regrown in spring under full or restricted light to measure stored reserve contribution to regrowth. Defoliated plants were resilient to defoliation during the growing season, matching the total biomass production of unclipped plants, though cutting reduced the number of leaves by ¬60% and flowers by almost 85%. Spring regrowth on stored reserves equalled that from reserves plus concurrent photosynthesis, indicating the value of USOs for regrowth. However, there was a marked carry-over effect of previous season defoliation, resulting in a one-third reduction in shoot growth and 40% fewer inflorescence in spring. Crucially, corm mass was more than halved by clipping, which resulted in lower spring biomass and inflorescence production. It was concluded that buried stored reserves are not protected from recurrent defoliation and mechanical damage to aerial plant parts and that continued diminishment of USOs under chronic disturbance by overgrazing or frequent mowing would weaken and likely eventually kill plants, reducing overall forb species richness. Lenient management by infrequent summer mowing or grazing at moderate stocking rates combined with periodic rotational full season resting and dormant-season burning is recommend to maintain the USOs and vigour of grassland geophytes in mesic grassland.

The impact of climate change on flow conditions and wetland ecosystems in the Lower Biebrza River (Poland).

Water plays a key role in the functioning of wetlands and a shortage or contamination of it leads to changes in habitat conditions and degradation of ecosystems. This article scrutinizes the impact of climate change on the hydrological characteristics of floods (maximum flow, duration, volume) in the River Biebrza wetlands (North-East Poland). We analysed the trends in duration and volume of flood and maximum discharges in the historical period 1970–2000 and predicted these for the future periods 2020–2050 and 2070–2100, respectively. Next we assessed the impact on the wetland ecosystems. The basis of our assessments consists of statistical analyses of hydrographs and calculations by the Soil and Water Assessment Tool hydrological model and considering nine bias-corrected climate models. The results indicate that both volume and duration of winter floods will keep increasing continuously under Representative Concentration Pathways 4.5 and 8.5. The reduction in peak annual floods is expected to decline slightly in both scenarios. On the other hand, the analysis of trends in mean and standard deviation revealed negligible tendencies in the datasets for summer and winter hydrological seasons within the three time frames analysed (1970–2000; 2020–2050; 2070–2100). We foresee several future implications for the floodplain ecosystems. Shifts in transversal ecosystem zonation parallel to the river will likely take place with more highly productive flood tolerant vegetation types. Nutrient availability and algal blooms during spring inundations will likely increase. Slowdown of organic matter turnover later in summer will lead to a higher peat accumulation rate. Logistical problems with summer mowing and removal of bushes in winter may enhance shrub encroachment.

The disappearance of cultural landscapes: the case of wooded-meadows in the Ligurian Apennines (NW Italy)

The “wooded-meadows system” is a multifunctional use of vegetation resources widespread in Europesince the Neolithic, and well documented in the Ligurian Apennines (NW Italy) between the MiddleAges and the first half of the 19th century. The management of wooded-meadows included: collectionof fallen and dead branches in spring, later used for fuel; mowing and grazing in summer; collection ofsecondary products; making sheaves from branches in autumn, later used as cattle and sheep fodder;coppicing, pollarding and cutting of trees in winter.Three sites located in eastern Ligurian Apennines were studied by means of an interdisciplinaryapproach in order to better understand the impact and the consequences of this historical landusepractice on vegetation structure and composition. In particular, based on specific features ofpalynological diagrams, it was possible to conclude that (compared to the post-cultural phase) when thewooded-meadows system was in use, all the sites were characterized by: (1) lower pollen percentagesof trees; (2) higher pollen percentages of shrubs and herbs; (3) higher percentages of anthropogenicpollen indicators; (4) higher values of palynological richness.This research also represents a contribution to issues of nature-conservation policy for the preservationof cultural landscapes. (Less)

Reversing expansion of Calamagrostis epigejos in a grassland biodiversity hotspot: Hemiparasitic Rhinanthus major does a better job than increased mowing intensity

AbstractQuestionsCan hemiparasitic Rhinanthus major originating from a local population suppress the competitive clonal grass Calamagrostis epigejos and reverse its expansion in species‐rich semi‐natural grasslands? Does sowing seeds of R. major facilitate restoration of target meadow vegetation? Is R. major more beneficial for biodiversity restoration/conservation than increased mowing intensity, a conventional measure to suppress C. epigejos?LocationČertoryje National Nature Reserve, Bílé Karpaty (White Carpathians) Protected Landscape Area, Czech Republic.MethodsWe conducted a before‐after‐control‐impact experiment in meadow patches heavily infested by C. epigejos: eight blocks, each containing four plots with four treatment combinations: (1) traditional management, i.e. mowing once in summer, (2) mowing in summer and autumn (3) mowing in summer and seed sowing of R. major, (4) mowing in summer and autumn and seed sowing of R. major. Above‐ground biomass of C. epigejos and vegetation composition of each of the plots were monitored every year from 2013 to 2016. To assess the effects of treatments, we analysed biomass production of C. epigejos, herb layer cover and vegetation composition.ResultsBoth sowing R. major and an additional autumn meadow cut significantly suppressed C. epigejos. Their effects were additive and of comparable size. Both treatments also had significant but markedly different effects on community composition. Rhinanthus major facilitated directional community composition change towards the regional Brachypodio‐Molinetum meadows. In contrast, increased mowing intensity significantly decreased frequency of threatened species, which however may have also been influenced by R. major.ConclusionsSowing of autochthonous R. major seeds was demonstrated as an efficient tool to suppress C. epigejos and facilitate community restoration. It can be combined with an additional meadow cut to further accelerate decline of the grass. The additional cut should however be used as a short‐term practice (1–2 years) only to minimize potential negative effects of its long‐term application on some threatened plant species. The effects of R. major are comparable to those of Rhinanthus alectorolophus reported previously. As a species occurring naturally in species‐rich dry grasslands, R. major has a broader and longer‐term application potential than R. alectorolophus in ecological restoration and conservation of these communities.

Optimum Seasonal Mowing Heights for Smooth Crabgrass Reduction in Tall Fescue Lawns

Cultural control methods for pest management are desirable as they can reduce pesticide use resulting in reduced costs and environmental impact. Previous research has shown increased mowing heights can reduce crabgrass (Digitaria sp.) populations. However, seasonal mowing height adjustments may further decrease crabgrass populations as lower heights of cut can increase turf density during optimal growing conditions. An experiment was conducted to determine ideal mowing height combinations during summer vs. fall/spring for crabgrass reductions in a tall fescue (Festuca arundinacea) sward. A half rate of prodiamine was included as a split-plot treatment to determine if mowing height combinations could reduce the amount of pesticide required to control crabgrass. Four fall/spring mowing heights (1, 2, 3, and 4 inches) were combined with the same summer mowing heights such that all heights were represented in both seasons. Results indicate that seasonal mowing height variations did not provide any better reduction in crabgrass populations over only using higher heights of cut consistently throughout the year. Also, the half rate of prodiamine successfully controlled crabgrass in all mowing heights except the lowest mowing height during summer months.

Clover green manure productivity and weed suppression in an organic grain rotation

AbstractGreen manure crops must produce high biomass to supply biological N, increase organic matter and control weeds. The objectives of our study were to assess above-ground biomass productivity and weed suppression of clover (Trifoliumspp.) green manures in an organic soybean [Glycine max(L.) Merr.]-winter wheat (Triticum aestivumL.)-corn (Zea maysL.) rotation in eastern Nebraska in three cycles (2011–12, 2012–13, 2013–14). Treatments were green manure species [red clover (T. pratenseL.) and white clover (T. repensL.)] undersown into winter wheat in March and green manure mowing regime (one late summer mowing or no mowing). We measured wheat productivity and grain protein at wheat harvest, and clover and weed above-ground biomass as dry matter (DM) at wheat harvest, 35 days after wheat harvest, in October and in April before clover termination. Winter wheat grain yields and grain protein were not affected by undersown clovers. DM was higher for red than for white clover at most sampling times. Red clover produced between 0.4 and 5.5 Mg ha−1in the fall and 0.4–5.2 Mg ha−1in the spring. White clover produced between 0.1 and 2.5 Mg ha−1in the fall and 0.2–3.1 Mg ha−1in the spring. Weed DM was lower under red clover than under white clover at most sampling times. In the spring, weed DM ranged from 0.0 to 0.6 Mg ha−1under red clover and from 0.0 to 3.1 Mg ha−1under white clover. Mowing did not consistently affect clover or weed DM. For organic growers in eastern Nebraska, red clover undersown into winter wheat can be a productive green manure with good weed suppression potential.

Mowing strategies for controlling Cirsium arvense in a permanent pasture in New Zealand compared using a matrix model.

Defoliation has frequently been proposed as a means of controlling Cirsium arvense (L.) Scop. (Californian thistle, Canada thistle, creeping thistle, perennial thistle), an economically damaging pastoral weed in temperate regions of the world, but its optimization has remained obscure. We developed a matrix model for the population dynamics of C. arvense in sheep‐grazed pasture in New Zealand that accounts for the effects of aerial shoot defoliation on a population's photosynthetic opportunity and consequential overwintered root biomass, enabling mowing regimes varying in the seasonal timing and frequency of defoliation to be compared. The model showed that the long‐term population dynamics of the weed is influenced by both the timing and frequency of mowing; a single‐yearly mowing, regardless of time of year, resulted in stasis or population growth, while in contrast, 14 of 21 possible twice‐yearly monthly mowing regimes, mainly those with mowing in late spring, summer, and early autumn, resulted in population decline. Population decline was greatest (with population density halving each year) with twice‐yearly mowing either in late spring and late summer, early summer and late summer, or early summer and early autumn. Our results indicate that mowing can be effective in reducing populations of C. arvense in pasture in the long term if conducted twice each year when the initial mowing is conducted in mid spring followed by a subsequent mowing from mid summer to early autumn. These mowing regimes reduce the photosynthetic opportunity of the C. arvense population and hence its ability to form the overwintering creeping roots upon which population growth depends.

High‐nature‐value grasslands have the capacity to cope with nutrient impoverishment induced by mowing and livestock grazing

Summary Management of high‐nature‐value (HNV) grasslands follows agri‐environmental schemes across large areas of Europe. Long‐term agreements and restrictions of fertilizers cause soil nutrient impoverishment, but remarkably this quite often does not reduce biomass production. Therefore, we tested how species‐rich vegetation copes with nutrient impoverishment under the most frequently used treatments, that is summer mowing and livestock grazing. During 2011–2012 we studied, simultaneously, plant species composition, soil and biomass chemical properties in two equally designed experiments where mowing, grazing or leaving fallow have been applied since 2004. We asked whether soil‐based (Corg : Ntot, plant‐available P and K) and plant‐based measures (N : P, N : K, K : P ratios and N‐, P‐, K‐nutrition indices) indicate the same pattern of nutrient limitation as the observed productivity gradient. Seven years of management application resulted in the lowest plant‐available P under grazing and the lowest plant‐available K under mowing, but neither grazed nor mown plots produced less biomass than fallow ones. Grazing supported dominance of grasses while mowing that of non‐leguminous forbs. Projection of nutrition indices to a common framework with nutrient ratios suggests that critical thresholds for diagnosis of nutrient limitation are a function of N deficiency. At biomass production of 2 t ha−1 a N‐nutrition index of 50 yielded threshold N : P = 14·0; hence, all our treatments with N : P of 9·9–12·5 should be N limited. Inspecting the productivity gradient separately for each management, we found only soil Corg : Ntot negatively related to biomass production in mown plots indicating N limitation. However in grazed plots, positive association of biomass production with plant‐available P and negative with biomass N : P and N : K suggested PK co‐limitation. Synthesis and applications. Mowing and grazing induced different patterns of soil nutrient impoverishment and nutrient limitation, but they did not reduce biomass production of high‐nature‐value grasslands. Non‐leguminous forbs prevailing under mowing precluded shortage of P, while grasses dominating under grazing efficiently captured N. We recommend designing agri‐environmental measures that will encourage alternating mowing and grazing. This should promote coexistence of multiple forbs and grasses, balance nutrient limitation and ensure stable biomass production under future low‐input scenarios.

Restoration of acidified and eutrophied rich fens: Long-term effects of traditional management and experimental liming

Rich fens are known for their high botanical diversity encompassing many endangered species. For decades, several management measures, including mowing and burning, have been applied to maintain a high biodiversity by means of slowing down the natural succession from calcareous rich fens to acidic poor fens or woodland. In this study, we assessed the long-term effects of these traditional management measures, and explored the effectiveness of liming as a measure to restore rich fen vegetation. Effects of summer mowing, and of burning after winter mowing, were assessed by comparing current (2013) and historical (1967) vegetation data. Effects of experimental liming, using different levels of lime addition (0, 1000, 2000, and 4000kgDolokal/ha), were monitored in the field during 7.5 years. Summer mowing led to more acidic and nutrient-poor conditions as indicated by a shift from rich to poor fen vegetation, including a well-developed bryophyte cover dominated by Sphagnum with some threatened species. Burning (after winter mowing) counteracted acidification but increased nutrient availability, as indicated by dominance of vascular species characteristic of productive tall-herb grasslands and a sparse bryophyte cover with common species. We conclude that the traditional measures were unable to maintain rich fen composition in the long term. Given the fact that the restoration of hydrological conditions, favouring rich fens, is not always feasible, liming could be an alternative to counteract acidification and improve rich fen conditions in the short term. This measure, however, appeared to be unsustainable as the re-establishment and dominance of Sphagnum spp. seriously complicated the development of rich fen vegetation in the longer term.

Mowing regime has different effects on reed stands in relation to habitat

Reed (Phragmites australis) is widespread in aquatic habitats in Europe where it plays an important ecological role, especially as stabilizer of lake and river shores and as filter against pollutants. Reed is also abundant in ecotones towards terrestrial habitats, especially fen meadows, where its expansion can out-compete rare slowly-growing fen species. Therefore, defining appropriate guidelines for managing reed in wetlands has to consider differences in the ecological roles that reed plays in different wetland habitats. In a small pre-alpine lake in N Italy, we mowed reed stands in three plant communities located along a transect from the lake shore to the periphery. In each community, three areas were subjected to reed mowing in late winter, as traditionally done in the past. Three additional areas were subjected to mowing in winter and summer, while three areas served as un-treated controls. Summer mowing was carried out in August, when the nesting period of birds was concluded. Mowing in winter did not affect reed aboveground biomass (RAB) in any community but enhanced the efficiency of removing nutrients by reducing litter accumulation in the soil. Mowing in winter and summer only slightly decreased RAB in the riparian community, not at all in the intermediate community but significantly diminished RAB in fen meadows. Phosphorus deficiency and/or reduced competition with other species probably accounted for RAB reduction in fen meadows. In conclusion, winter mowing can be overall recommended for preventing eutrophication of littoral habitats while summer mowing is advisable for preventing reed expansion in fen meadows. However, the timing of summer mowing has to be defined considering all requirements needed for optimal management of each individual site.

Hand Pulling Following Mowing and Herbicide Treatments Increases Control of Spotted Knapweed (Centaurea stoebe)

AbstractExtensive areas in the upper Midwest have been invaded by spotted knapweed, and effective management strategies are required to reestablish native plant communities. We examined effects of mowing, mowing plus clopyralid, or mowing plus glyphosate in factorial combination with hand pulling and burning on knapweed abundances on a knapweed-infested site in western Michigan. We applied mowing and herbicide treatments in summer 2008, and seeded all plots with native grasses and forbs in spring 2009. We conducted the knapweed pulling treatment from 2009 to 2012 in July. The prescribed burn was conducted in April 2012. By 2012, hand pulling reduced adult knapweed densities to 0.57 ± 0.12 m−2(0.053 ± 0.011 ft−2) (mean ± SE), which was 5.8% of nonpulled treatments, juvenile densities to 0.29 ± 0.07 m−2(2.1% of nonpulled treatments), and seedling densities to 0.07 ± 0.06 m−2(2.6% of nonpulled treatments). After 3 yr, hand pulling reduced seed bank densities to 68 ± 26 m−2as compared to 524 ± 254 m−2in nonpulled treatments and 369 ± 66 m−2in adjacent untreated areas of the study site. Without hand pulling, effects of mowing or mowing plus glyphosate were short-lived and allowed knapweed to rapidly resurge. In comparison, although a single mowing plus clopyralid treatment maintained significantly reduced densities of knapweed for 4 yr, by 2012 knapweed biomass in the nonpulled clopyralid treatment was approximately 60% of that in the other nonpulled treatments. Burning had minimal impacts on knapweed densities regardless of treatment combination, probably as a result of low fire intensity. Results demonstrated that persistent hand pulling used as a follow-up to single mowing or mowing plus herbicide treatments can be an effective practice for treating isolated spotted knapweed infestations or for removing small numbers of knapweed that survive herbicide applications.

Alleyway Cover Crops Have Little Influence on Pinot noir Grapevines (Vitis viniferaL.) in Two Western Oregon Vineyards

Seven cover-crop treatments were compared in two north Willamette Valley Pinot noir vineyards over two years to test if alleyway cover crops that are mowed in spring and summer compete with grapevines for water or nutrients. Five different cover-crop mixtures were compared to a clean-cultivated control and resident vegetation treatments in 2004 and 2005. Treatments were evaluated for biomass production, quantity of nitrogen (N) contributed to the vineyard floor, weed suppression, and effect on soil water content. Vine responses to the different floor-management strategies included measures of shoot growth, water and nutrient status, yield, and juice quality. Three treatments were evaluated for their effect on fine roots and colonization by arbuscular mycorrhizal fungi (AMF). Cover crops influenced soil moisture in a different manner at each site, although the lowest soil moisture was consistently found in the perennial grass and clover mixture. Cover-crop treatments had an impact on grapevine N status at one vineyard, altering leaf blade N concentrations at bloom and juice N concentrations at harvest, although different treatments did not alter N status consistently over time. Cover crops did not alter shoot growth, pruning mass, leaf water potential, fine root density, or colonization of roots by AMF and did not affect yield, cluster weights, juice soluble solids, pH, or titratable acidity. Results showed that alleyway cover crops managed by spring and summer mowing do not have consistent effects on grapevines in western Oregon vineyards and suggest that little competition occurs between cover crops and vines in the mixtures evaluated. Further examination of cover crops composed primarily of clovers or of perennial grasses is warranted.

Effect of different mowing regimes on butterflies and diurnal moths on road verges

In northern and central Europe road verges offer alternative habitats for declining plant and invertebrate species of semi-natural grasslands. The quality of road verges as habitats depends on several factors, of which the mowing regime is one of the easiest to modify. In this study we compared the Lepidoptera communities on road verges that underwent three different mowing regimes regarding the timing and intensity of mowing; mowing in mid-summer, mowing in late summer, and partial mowing (a narrow strip next to the road). A total of 12,174 individuals and 107 species of Lepidoptera were recorded. The mid-summer mown verges had lower species richness and abundance of butterflies and lower species richness and diversity of diurnal moths compared to the late summer and partially mown verges. By delaying the annual mowing until late summer or promoting mosaic-like mowing regimes, such as partial mowing, the quality of road verges as habitats for butterflies and diurnal moths can be improved.