Grass species can be classified into different functional types based on their growth strategies, and contrasting persistence strategies are observed in different grass species. Excluding seedling recruitments, changes in populations of grasses are basically a trade-off between natality and mortality of tillers. We hypothesised that the persistence pathway of perennial grasses is linked to their growth strategy, regardless whether they are growing as monoculture or as a mixture. Species with contrasting growth strategies (Arrhenatherum elatius L., Dactylis glomerata L., and Festuca arundinacea Schreb.) were cultivated as monocultures and as a mixture and their tiller natality and mortality were evaluated for two years after swards establishment. All pastures maintained their population size during the experimental period, although decreases in tiller densities occurred during the warmer season. Arrhenatherum elatius had the highest tiller mortality and natality whereas the F. arundinacea had the lowest ones. Arrhenatherum elatius had many tillers appearing in all seasons but their tillers were short-lived. Conversely, F. arundinacea and D. glomerata developed numerous tillers during autumn and winter and their tillers survived, on average, almost six and three times longer than those of A. elatius, respectively. There were no differences in tillering dynamics among populations grown in monocultures or in the mixture. Regardless of whether they were cultivated in monocultures or as a mixture, the persistence pathway of perennial grasses is linked with their growth strategies with exploitative species presenting a high tiller turnover throughout the year whereas the persistence of more conservative species is based on a high tiller survival.

Core Ideas Mixing grass forage species can increase forage yield and stability. Overyielding was more influenced by increasing leaf biomass rather than stem biomass. Dominant grasses with contrasting growth strategies can compose productive and stable pastures. Mixtures composed of species with different growth strategies (e.g., exploitative and conservative), which have different abilities for resource capture and use, are thought to improve grassland ecosystem services. However, plant species that compete better for limiting resources can become dominant. This study examined whether potential dominant perennial grasses with different growth strategies can compose productive and stable forage mixtures under low competition for resources (nutrients and light). Arrhenatherum elatius L. (exploitative), Festuca arundinacea Schreb. (conservative), and Dactylis glomerata L. (moderately exploitative) were sowed as monocultures and as a three‐species mixture. Pastures were fertilized to maintain high soil fertility levels and mowed by half when their canopies reached 20 cm in height (95% of light interception in the vegetative stage) allowing for over 2 yr of data collection. The proportion of each species in the mixture remained unaltered throughout the experimental period. Transgressive overyielding was not observed; however, the mixture presented a similar yield to the most productive monocultures (10,200 kg DM ha−1 yr−1), although D. glomerata, which presented the lowest yield in monoculture (6400 kg DM ha−1 yr−1), comprised 68.1% of post‐cutting biomass in the mixture. Arrhenatherum elatius and F. arundinacea populations presented less yield variance in monoculture, but higher yield stability was observed in the mixture. Overyielding in the three studied species was strongly affected by leaf production. Mixtures composed of perennial grasses with different growth strategies when grown in nutrient‐rich soil and under conditions of low light competition can compose productive and stable swards, while maximizing leaf production.

Background and aims: The concepts of critical nitrogen (N) concentration and nitrogen nutrition index (NNI) provide effective tools for assessing the N nutritional status of pastoral systems. However, no conclusive data exist concerning the effects of stubble height at harvest on the N dilution curve [N concentration (N%) = a(biomass)−b] and mixed species cultivation on N nutritional status of forage plants with contrasting growth strategies. To evaluate these effects, three cool‐season perennial grasses (exploitative, Arrhenatherum elatius L.; moderately exploitative, Dactylis glomerata L.; conservative, Festuca arundinacea Scherb.) were grown under different cultivation methods either as pure stands or as a mixture and conducted two experiments. Methods: In experiment I, canopies of different grass species pure stands and mixtures were subjected to defoliation managements aimed to not exceed the critical LAI at harvest. Forage samples were collected from October 2015 to August 2016 to determine the N nutritional status throughout the seasons. In experiment II, half of each pure stand was mowed to 10 cm in height, and the other half to ground level. Thereafter, herbage samples were taken during regrowth to determine N dilution curves in both scenarios (from ground level and from stubble height of 10 cm). Results: We verified an NNI above 0.8 during autumn and winter for A. elatius, D. glomerata, and the mixture but only in winter for F. arundinacea. Dactylis glomerata grown in the mixture had a lower N% than its pure stand during autumn and winter, whereas A. elatius and F. arundinacea showed no differences irrespective of cultivation method throughout the year. The three forage species presented classical dilution curves when regrowth was initiated from ground level, but quadratic trends were observed when regrowth was initiated from stubble heights of 10 cm. Conclusions: Overall the N nutritional status of cool‐season perennial grasses was not affected by cultivation method when pastures were managed in conditions of non‐limiting N supply and with pre‐cut/grazing height targets derived from critical LAI measured at the full vegetative growth stage. Moreover, the N nutrition status in pastures managed under moderate/lenient defoliation should not be evaluated during periods of less intense canopy renewal and/or right after the cut/grazing events.

White grubs (Cyclocephala flavipennis) damaging perennial winter pastures in the South Region of Brazil.Ciência Rural, v.47, n.5, 2017. In the South Region of Brazil, besides the traditional cultivation of winter-annual pastures, cultivation of winter perennial grasses, particularly tall fescue (Festuca arundinacea Schreb.) and orchardgrass (Dactylis glomerata L.), can be an alternative to reduce the periods of low forage production from native and cultivated perennial warm season grasses. Despite the growing relevance of pasture cultivation in the temperate climate regions, little is known about the soil insects causing pasture damage in these areas. In Brazil, 1,008 species of melolontids (Coleoptera: Melolonthidae) have been reported. The larvae of these species live in the soil, and are commonly called "white grubs" (MORÓN, 2004

In this study we tested whether the root biomass of mixtures composed by grass species is greater than their respective monocultures. The treatments were monocultures of Arrhenatherum elatius, Festuca arundinacea, Dactylis glomerata, and a mixture of them, cultivated in a rich-soil environment. Root biomass was evaluated on a single evaluation per season at three soil depths (0-5, 5-10, and 10-20 cm). Mixed swards presented the greatest root biomass, and this was explained by a greater concentration in the topsoil layer (0-5 cm). These findings reinforce the need for permanent soil conservation practices to not jeopardize the benefits of the more abundant root biomass reported in the mixed swards.

The diversity of traits plays a key role in the maximization of ecosystems' multi‐functionality, but interspecific competition in defoliated swards can lead to unpredictable changes in the functional traits over the plant community. However, we hypothesize that interrupting canopy regrowth at a height corresponding to critical leaf area index (LAI), associated with moderate intensity of defoliation, can be an effective management to preserve the functional traits of contrasting growth strategy grasses cultivated as a mixture. A 2‐year experiment was conceived to assess continuously several traits of three cool‐season perennial grasses (Arrhenatherum elatius [exploitative], Dactylis glomerata [moderately exploitative] and Festuca arundinacea [conservative]) cultivated as single species stand or as a mixture. Dactylis glomerata was the less productive stand but no difference was observed between the mixture and the most productive monocultures. No change was observed in functional traits, whether the species were cultivated as monoculture or as a mixture. The dissimilarities over traits and, therefore, the functional identity of contrasting growth strategy grasses growing in multi‐specific swards was preserved when canopy regrowth was interrupted at a height corresponding to the critical LAI associated with moderate intensity of defoliation. Since the diversity of traits maximizes ecosystem multi‐functionality, our findings provide a step forward towards designing management practices that enhance ecosystems services delivered by cultivated multi‐specific grasslands.