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Resprouting grasses are associated with less frequent fire than seeders

<ul> <li> Plant populations persist under recurrent fire via resprouting from surviving tissues (resprouters) or seedling recruitment (seeders). Woody species are inherently slow-maturing, meaning that seeders are confined to infrequent fire regimes. However, for grasses, which mature faster, the relationships between persistence strategy and fire regime remains unknown.</li> <li>Globally, we analysed associations between fire regimes experienced by hundreds of grass species and their persistence strategy, within a phylogenetic context. We also tested whether persistence strategies are associated with morphological and physiological traits.</li> <li>Resprouters were associated with less frequent fire than seeders. Whilst modal fire frequencies were similar (fire return interval of 4-6 years), seeders were restricted to regions with more frequent fire than resprouters, suggesting that greater competition with long-lived resprouters restricts seeder recruitment and survival when fire is rare. Resprouting was associated with lower leaf N, higher C/N ratios and the presence of below-ground buds, but was unrelated to photosynthetic pathway.</li> <li>Differences between the life histories of grasses and woody species lead to a contrasting prevalence of seeders and resprouters in relation to fire frequency. Rapid sexual maturation in grasses means that seeder distributions, relative to fire regime, are determined by competitive ability and recruitment, rather than time to reproductive maturity.</li> </ul>

Morphoecological characteristics of grasses used to restore degraded semi-arid African rangelands

Progressive loss of productivity and plant diversity has been a major concern for land managers of global arid and semi-arid rangelands. This is often attributed to heavy grazing by large livestock herds and wildlife leading to land degradation threatening millions of livelihoods that rely on rangeland resources. Consequently, combating land degradation has increasingly become important global agenda. Active restoration technologies such as indigenous grass reseeding has been identified as a viable ecological solution for restoring degraded rangeland landscapes and providing forage for sustainable livestock production. Grass species indigenous to African rangelands Cenchrus ciliaris L. (African foxtail grass), Eragrostis superba Peyr. (Maasai love grass), Enteropogon macrostachyus (Hochst. Ex A. Rich.) Monro ex Benth. (Bush rye grass), Chloris roxburghiana Schult. (Horsetail grass) and Chloris gayana Kunth. cv Boma (Rhodes grass) were established in an African semi-arid rangeland landscape under natural conditions to compare their morphoecological characteristics and suitability for ecological restoration. Seed viability, seedling emergence, biomass dry matter yields, plant densities, basal cover, seed production, tiller densities and plant height were determined. Chloris gayana cv Boma and E. superba produced significantly higher dry matter biomass yields and seed production. High biomass and seed production demonstrate their suitability to support livestock production and replenish depleted soil seed banks, respectively. Enteropogon macrostachyus and C. ciliaris displayed significantly higher values for plant densities, tiller densities and basal cover, also used to measure establishment and ecological restoration success. Chloris roxburghiana ranked lowest in all the measured morphoecological characteristics. This could be a strong indicator of ecological site-specific characteristic of C. roxburghiana. Active restoration of degraded African semi-arid rangelands and forage provision for herbivores using indigenous grass reseeding can best be achieved through careful selection of grass species to take advantage on their specific multiple morphoecological characteristics. Furthermore, selection of the grass species to use should primarily be informed by the intended use of the rangeland.

Overlap in the wing shape of migratory, nomadic and sedentary grass parrots

Bird wing shape is highly correlated with mobility, and vagile species have more pointed wing tips than sedentary ones. Most studies of bird wing shape are biased to the northern hemisphere, and consider only two migratory syndromes (north-south migrants or sedentary species). There are major gaps in knowledge about the wing shapes of different taxa with other movement strategies (e.g. nomads) in the southern hemisphere. Parrots are a prominent southern hemisphere bird order with complex movement patterns, but their wing shapes are mostly unstudied. We test whether three metrics of wing shape of grass parrots (Neophema and Neopsephotus spp.) correspond to their purported migration syndromes (and other factors). We show that two strongly migratory grass parrots and an arid-adapted nomad had pointed wings, with flight feather longer distally and shorter proximally. However, purportedly sedentary species overlapped extensively with migrants and nomads in all aspects of wing shape, and taxonomic relationships, purported migratory syndromes and ecological barriers did not explain the variation we recorded. The most distantly related species (Neopsephotus) had most dissimilar wing shape to the others, but broadly conformed to the expectations of long pointed wings of a nomad. Why purportedly sedentary grass parrots had unexpectedly pointed wings is unclear. We propose the hypothesis that this wing shape may persist in sedentary populations if individuals experience strong but intermittent selection to disperse when environmental conditions are poor. If pointed wings are not costly during good times when individuals are sedentary, this wing shape may persist in populations as a 'back up' in bad times. Our study highlights the interesting migration patterns in the southern hemisphere that remain largely unstudied. Wing shape offers an interesting way to identify potentially undiscovered capacity for movement in data deficient species, which may also have implications for conservation.

Spatial, climate and ploidy factors drive genomic diversity and resilience in the widespread grass Themeda triandra

This data set was used to assess the climate resilience of Themeda triandra, a foundational species and the most widespread plant in Australia, by assessing the relative contributions of spatial, environmental, and ploidy factors to contemporary genomic variation. Reduced-representation genome sequencing on 472 samples from 52 locations was used to test how the distribution of genomic variation, including ploidy polymorphism, supports adaptation to hotter and drier climates.

An invasive grass species has both local and broad-scale impacts on diversity: Potential mechanisms and implications

Questions The impact of invasive plant species on native diversity varies with spatial scale, with some invaders leading to broad-scale diversity declines and others only local declines. These discrepancies may reflect the invaders capacity to reduce niche opportunities across spatial scales which can be associated with their functional traits. We investigated impact-scale relationships and trait-based mechanisms, in areas invaded by the exotic perennial grass species, Bothriochloa pertusa. We examine root traits specifically, as belowground competition was considered particularly important to the success of this species. Location Grassy 'ironbark' woodlands of eastern Queensland, Australia Methods We examined plots with varying degrees of invasion by B. pertusa, at multiple spatial scales (up to 1000 m2) and analysed changes to the species area relationships (SARs) with increasing invader cover. Changes to SARs were assessed in relation to the invaders effect on rare (low-patch-occupancy) and common species in the community. In a separate analysis within the same habitat we collected root cores across a gradient of invader cover and analysed changes to community root traits that were considered important correlates of competition for space and nutrients. Results Invasion-induced reductions in diversity were pervasive at all scales investigated, and this was associated with a proportionally greater effect on rare species in the community. In the separate root analysis, changes in community root traits with increasing invader cover were potentially indicative of more intense competition for resources rather than space. Conclusions The observed regional-scale dominance of B. pertusa and associated declines in diversity warrant serious concern for the conservation of native plant communities and species in a region already at risk from other anthropogenic threats. Intense competition for belowground resources is likely a contributing mechanism to the success of B. pertusa in this study system. Experimental examination of this and other mechanisms would help to validate these findings.

opencc-zeroDec 2020View details →

Data from: With a little help from my friends – Physiological integration facilitates invasion of wetland grass Elymus athericus into flooded soils

Tidal wetlands worldwide are undergoing rapid invasions by tall-growing clonal grasses. Prominent examples are invasions by species of the genera Spartina, Phragmites, and Elymus. The responsible physiological and ecological drivers of these invasions are poorly understood. Physiological integration (PI) is a key trait of clonal plants, which enables the exchange of resources among ramets. We investigated PI in Elymus athericus, which has been rapidly spreading from high-marsh into low-marsh environments of European salt marshes during the last decades. We applied a nitrogen-stable-isotope approach to trace nutrient translocation between ramets in a factorial mesocosm experiment. The experiment was set up to mimic an invasion pattern commonly found in tidal wetlands, i.e. from high-elevated and rarely flooded into low-elevated and frequently flooded microenvironments. We tested for intraspecific variability in PI by including two genotypes of Elymus that naturally occur at different elevations within the tidal frame, a high-marsh (HM) and a low-marsh (LM) genotype. PI strongly increased offspring ramet aboveground and belowground biomass by 62 and 81%, respectively. Offspring ramets under drained conditions had 95% greater belowground biomass than those under flooded conditions. LM genotype offspring ramets produced 27% more aboveground biomass than HM genotypes. Offspring ramets were clearly more enriched in 15N under flooded vs. drained conditions; however, this positive effect of flooding on δ15N was only significant in the LM genotype. Our findings demonstrate the importance of PI for the growth of Elymus offspring ramets and thereby for the species' capacity for fast vegetative spread. We show that offspring ramets under stressful flooded conditions are more dependent on nutrient supply from parent ramets than those under drained conditions. Our data furthermore suggest a higher degree of adaptation to flooding via PI in the LM vs. HM genotype. In conclusion, we highlight the importance of assessing PI and intraspecific trait variability to understand invasion processes within ecosystems.

opennotspecifiedSep 2020View details →

FIGURE 1. NRM 8260, neotype for Coluber natrix. A in The taxonomic status of grass snake, Natrix natrix (Linnaeus, 1758) (Squamata: Colubridae), with designation of a neotype

FIGURE 1. NRM 8260, neotype for Coluber natrix. A) Dorsal view B) Ventral view. C) Immediately after being euthanized. D) Photo of the capture locality, Fada mill pond.

opencc-zeroJan 2021View details →

Field-based ecological studies to assess prospective biological control agents for invasive alien plants: an example from giant rat's tail grass

1. Biological control (biocontrol) of invasive alien plants is a widely utilised weed management tool. Prospective biocontrol agents are typically assessed through host-specificity testing and pre-release efficacy studies performed in quarantine. However, rearing of the potential biocontrol agents and/or test plants is often difficult or impossible under quarantine conditions. Moreover, practitioners may attain laboratory-artefacts in quarantine, which may result in the potential agent being needlessly rejected. Field-based studies in the weed's indigenous distribution could overcome these issues. 2. Sporobolus pyramidalis and Sporobolus natalensis (giant rat's tail grass; Poaceae) are indigenous in Africa but have become problematic invasive alien plants in Australia. A previous biocontrol programme was terminated because the candidate agent could not be reared and tested in quarantine. We performed field-based host-specificity and efficacy studies for prospective biocontrol agents in South Africa (indigenous distribution). Forty-seven non-target grass species were sampled during host-specificity assessments. Candidate agent efficacy was estimated based on damage to the target weeds, for each host-specific candidate individually and in combination with other host-specific candidates. 3. Three species of endophagous wasps were deemed host-specific. Efficacy assessments identified an undescribed stem-boring wasp (Tetramesa sp.) species as the most damaging candidate. A second Tetramesa species was much less damaging alone but had a cumulative impact on the plant in combination with the more damaging Tetramesa species. Both Tetramesa species are recommended for importation into quarantine in Australia for confirmatory host-specificity testing with a significantly reduced test plant list. 4. Synthesis and applications: Similar field-based assessments in the indigenous distribution of weeds targeted for biocontrol could be included in future programmes. Where rearing of potential agents and/or test plants is difficult or impossible under quarantine conditions, our field-based method provides an alternative. Where quarantine-based testing is feasible, this method ensures that only candidates that have passed an ecologically realistic host-specificity and potential efficacy screening are imported into quarantine. This may reduce the number of agents that are imported and the length of time each agent is kept in quarantine. This is advantageous because quarantine space is highly valuable and is usually a limiting factor in pre-release assessments of biocontrol agents.

Figure 5 in Hybridization patterns in two contact zones of grass snakes reveal a new Central European snake species

Figure 5. Cline analyses of mitochondrial DNA and microsatellite data. Transects (top) through the two different contact zones of grass snake lineages (helvetica/eastern lineages – left; yellow/red lineages – right) and associated Maximum Likelihood clines for microsatellites (centre) and mtDNA (bottom). Grey: fuzzy 95% credible cline region. Red points (top) indicate cline centres. Maps were created using ARCGIS 10.2 (http://www. esri.com/arcgis) and ADOBE ILLUSTRATOR CS6 (http://www.adobe.com/products/illustrator.html).

Figure 4. PCA axes 1–2 in Hybridization patterns in two contact zones of grass snakes reveal a new Central European snake species

Figure 4. PCA axes 1–2 for microsatellite data. Samples are coloured according to mitochondrial lineages (top) or STRUCTURE clusters (bottom). Admixed individuals were identified according to HYBRIDLAB results. PCAs for the yellow and red lineages correspond to the samples from Fig. 3c. Non-native samples were excluded. The oval outlines represent 95% confidential intervals. For helvetica and the eastern lineages (left) the x axis explains 16.6% and the y axis 4.5% of variation. For the eastern lineages (right) the x axis explains 3.8% and the y axis 2.9% of variation. Analyses along axes 1–3 produced nearly identical results (see Supplementary Fig. S4).

Figure 3 in Hybridization patterns in two contact zones of grass snakes reveal a new Central European snake species

Figure 3. Genotypic structuring of grass snakes. On the left, the mitochondrial lineage of each sample is shown above the STRUCTURE diagrams, with haplotypes of Natrix natrix helvetica indicated in blue and haplotypes of the eastern lineages in colours corresponding to Fig. 1 (yellow, red, lilac, grey, green; white = missing data). In (a), orange and dark blue corresponds to non-native snakes (Italian lineages). Samples in STRUCTURE diagrams are arranged within each country from west to east (a) or from north to south (b,c). In STRUCTURE diagrams, an individual sample is represented by a vertical bar reflecting its inferred ancestry. In (a), the blue cluster corresponds to N. n. helvetica and the light green cluster to all other lineages. The isolated red/light green block (first row) represents the allochthonous population from the Neander valley, Germany. In (b), samples with genetic impact of helvetica are excluded. The pink cluster corresponds to samples from the yellow and red lineages. Brown percentages indicate genetic impact of adjacent lineages (lilac, grey, green). In (c) only samples from the yellow and red lineages and their hybrids, without genetic signatures of other lineages, were processed. Country abbreviations: Ba – Balkans (Albania, Bosnia and Herzegovina, Montenegro, Serbia, Kosovo, Former Yugoslav Republic of Macedonia, Romania, Bulgaria, and Greece), CH – Switzerland, CRO – Croatia, CZ – Czech Republic, FI – Finland, H – Hungary, N – Norway, NL – Netherlands, PL – Poland, S – Sweden. Maps were created using ARCGIS 10.2 (http://www.esri.com/arcgis) and ADOBE ILLUSTRATOR CS6 (http://www.adobe. com/products/ illustrator.html).

Figure 1 in Hybridization patterns in two contact zones of grass snakes reveal a new Central European snake species

Figure 1. Distribution of mitochondrial lineages of 1,580 grass snakes used in this study. Total sample size of each clade shown in the legend. Eight allochthonous grass snakes with haplotypes of Italian lineages caught in southern Great Britain and Hesse, Germany, not shown. Map was created using ARCGIS 10.2 (http://www.esri. com/arcgis) and ADOBE ILLUSTRATOR CS6 (http://www.adobe.com/products/illustrator.html). Inset: Natrix natrix helvetica (Linz am Rhein, Germany); photo: Wolfgang Böhme.

Figure 2 in Hybridization patterns in two contact zones of grass snakes reveal a new Central European snake species

Figure 2. Parsimony networks of mtDNA sequences. Symbol sizes reflect haplotype frequencies. Small black circles are missing node haplotypes; each line connecting two haplotypes corresponds to one mutation step, if not otherwise indicated by numbers. Haplotype colours correspond to lineages, i.e. Natrix natrix helvetica (h) in blue; eastern lineages in yellow (y) and in red (r).

opencc-zeroJan 2021View details →

Herbicide effects on the establishment of a native bunchgrass in annual grass invaded areas: Indaziflam vs. imazapic

Annual grass invasion is transforming the western US and driving a need for restoration techniques that can both reduce exotic annual grass abundance and allow revegetation of native species. Pre-emergent herbicides can provide control of annual grasses, but when applied concurrently with direct seeding efforts, the herbicide can also impact seeded species. Indaziflam is a relatively new herbicide that may provide extended control of exotic annual grasses, but little is known about its effects when applied at the time of seeding. In this study, we compared indaziflam to imazapic, a popular herbicide used in restoration efforts, to understand how indaziflam affects plant establishment of a native species, bluebunch wheatgrass Pseudoroegneria spicata (Pursh) Á. Löve. We created furrows on half our treatments to limit herbicide concentrations and potentially create a safe-site for seeding bluebunch wheatgrass. During the two-year study, indaziflam provided consistent control of the annual weed, downy brome Bromus tectorum L., whereas imazapic control decreased sharply with time. Indaziflam and imazapic decreased bluebunch wheatgrass seedling emergence by 96 and 46%, and two-year plant density by 91 and 65%, respectively, compared to non-herbicide treatments. Both herbicides reduced aboveground biomass of bluebunch wheatgrass by over 85% two years after seeding/herbicide application. Furrow treatments mitigated imazapic effect on bluebunch wheatgrass, but did not limit the impacts by indaziflam. Herbicide can be used in conjunction with direct seeding efforts, but mitigation of the effects to native seeds will depend on herbicide specifics such as mode of action and soil mobility.

opencc-zeroDec 2017View details →

Data from: Jasmonic acid regulation of the anti-herbivory mechanism conferred by fungal endophytes in grasses

1. The most studied mechanism of protection against herbivores in grasses associated with Epichloë fungal endophytes has been the fungal production of alkaloids. However, the contribution of the plant immune responses on the level of resistance to herbivores in symbiotic grasses has been poorly explored. We studied the relationship between the plant hormone, jasmonic acid (JA), and Epichloë fungal endophytes on herbivore defenses in symbiotic grasses. We hypothesized that an exogenous application of methyl jasmonate (MeJA), an activator of the plant JA defense response, would increase the level of resistance of endophyte-symbiotic and non-symbiotic plants to a chewing insect. As Epichloë endophytes produce alkaloids, an enhancement of the JA defense would complement to the resistance given by these alkaloids. 2. Lolium multiflorum plants symbiotic and non-symbiotic with the endophyte Epichloë occultans were subjected to an exogenous application of MeJA followed by a challenge with the generalist chewing insect Spodoptera frugiperda. We measured the level of plant resistance to chewing insects, and the defenses conferred by host plants and fungal endophytes. 3. Symbiotic plants were more resistant to S. frugiperda than their non-symbiotic counterparts. However, despite the fact that the JA concentration significantly increased in all plants with the MeJA exposure, neither endophyte-symbiotic nor non-symbiotic plants showed an enhanced resistance to insects. Unexpectedly, the exposure of endophyte-symbiotic plants to MeJA led to a reduction in the concentration of loline alkaloids (i.e. N-formyllolines and N-acetylnorlolines), consequently decreasing the level of plant resistance to the herbivore. 4. Synthesis. Our results suggest that, rather than complementing the alkaloid-based defense, the JA hormone weakens the anti-herbivore mechanism conferred by endophytes. The present study highlights that the interaction between the JA hormone and the presence of leaf fungal endophytes can be of importance for the effectiveness of the anti-herbivore defenses of symbiotic plants.

opencc-zeroDec 2013View details →

Data from: Positive effects of non-native grasses on the growth of a native annual in a southern California ecosystem

Fire disturbance is considered a major factor in the promotion of non-native plant species. Non-native grasses are adapted to fire and can alter environmental conditions and reduce resource availability in native coastal sage scrub and chaparral communities of southern California. In these communities persistence of non-native grasses following fire can inhibit establishment and growth of woody species. This may allow certain native herbaceous species to colonize and persist beneath gaps in the canopy. A field manipulative experiment with control, litter, and bare ground treatments was used to examine the impact of non-native grasses on growth and establishment of a native herbaceous species, Cryptantha muricata. C. muricata seedling survival, growth, and reproduction were greatest in the control treatment where non-native grasses were present. C. muricata plants growing in the presence of non-native grasses produced more than twice the number of flowers and more than twice the reproductive biomass of plants growing in the treatments where non-native grasses were removed. Total biomass and number of fruits were also greater in the plants growing in the presence of non-native grasses. Total biomass and reproductive biomass was also greater in late germinants than early germinants growing in the presence of non-native grasses. This study suggests a potential positive effect of non-native grasses on the performance of a particular native annual in a southern California ecosystem.

opencc-zeroJul 2019View details →

Data from: Defoliation of a grass by reindeer is compensated by the positive effects of its soil legacy, dung deposition, and moss removal

Herbivory is one of the key drivers shaping plant community dynamics. Herbivores can strongly influence plant productivity directly through defoliation and the return of nutrients in the form of dung and urine, but also indirectly by reducing the abundance of neighbouring plants and inducing changes in soil processes. However, the relative importance of these processes is poorly understood. We, therefore, established a common garden experiment to study plant responses to defoliation, dung addition, moss cover, and the soil legacy of reindeer grazing. We used an arctic tundra grazed by reindeer as our study system, and Festuca ovina, a common grazing-tolerant grass species as the model species. The soil legacy of reindeer grazing had the strongest effect on plants, and resulted in higher growth in soils originating from previously heavily-grazed sites. Defoliation also had a strong effect and reduced shoot and root growth and nutrient uptake. Plants did not fully compensate for the tissue lost due to defoliation, even when nutrient availability was high. In contrast, defoliation enhanced plant nitrogen concentrations. Dung addition increased plant production, nitrogen concentrations and nutrient uptake, although the effect was fairly small. Mosses also had a positive effect on aboveground plant production as long as the plants were not defoliated. The presence of a thick moss layer reduced plant growth following defoliation. This study demonstrates that grasses, even though they suffer from defoliation, can tolerate high densities of herbivores when all aspects of herbivores on ecosystems are taken into account. Our results further show that the positive effect of herbivores on plant growth via changes in soil properties is essential for plants to cope with a high grazing pressure. The strong effect of the soil legacy of reindeer grazing reveals that herbivores can have long-lasting effects on plant productivity and ecosystem functioning after grazing has ceased.

opencc-zeroDec 2008View details →

Data from: A porous convection model for small-scale grass patterns

Spatial ecological patterns are usually ascribed to Turing‐type reaction‐diffusion or scale‐dependent feedback processes, but morphologically indistinguishable patterns can be produced by instabilities in fluid flow. We present a new hypothesis that suggests that fluid convection and chill damage to plants could form vegetation patterns with wavelengths ≈1–2 times the plant height. Previous hypotheses for small‐scale vegetation pattern formation relied on a Turing process driven by competition for water, which is thought to occur in large vegetation patterns. Predictions of the new hypothesis were consistent with properties of natural grass patterns in North Carolina, contradicting the Turing hypothesis. These results indicate that similarities in pattern morphology should not be interpreted as implying similarities in the pattern‐forming processes, that small‐wavelength vegetation patterns may arise from mechanisms that are distinct from those generating long‐wavelength vegetation patterns, and that fluid instabilities should be recognized as a cause of ecological patterns.

opencc-zeroDec 2016View details →

Data from: Root volume distribution of maturing perennial grasses revealed by correcting for minirhizotron surface effects

Aims: Root architecture drives plant ecology and physiology, but current detection methods limit understanding of root placement within soil profiles. We developed a statistical model of root volume along depth gradients and used it to infer carbon storage potential of land-use changes from conventional agriculture to perennial bioenergy grasses. Methods: We estimated root volume of maize-soybean rotation and three perennial grass systems (Miscanthus × giganteus, Panicum virgatum, tallgrass prairie mix) by Bayesian modeling from minirhizotron images, correcting for small images and near-surface underdetection. We monitored seasonal and inter-annual changes in root volume distribution, then validated our estimates against root mass from core samples. Results: The model explained 29% of root volume variation and validated well against core mass. Seventh-year perennials had greater belowground biomass than maize-soybean both in total (11-16×) and throughout the profile (2-17× at every depth < 120 cm). Perennials' relative depth allocations were stable over time, while total root volume increased through five years. In 2012 a historically hot, dry summer damaged maize while perennials appeared resilient, suggesting their large-deep root systems aid drought resistance. Conclusions: Perennial root systems are large, deep, and persistent. Converting row crops to perennial bioenergy grasses likely sequesters carbon in a large, potentially very stable, soil pool.