C4 Perennial Grass Research Articles

Solar arrays create novel environments that uniquely alter plant responses

Societal Impact StatementGlobally, the combustion of fossil fuels represents the vast majority of greenhouse gas emissions, and as such, a transition to renewable forms of energy provides the greatest potential for mitigating climate warming. Although solar photovoltaic energy generation is a leading climate solution, these energy facilities have a significant spatial footprint. Naturally, concerns regarding the coexistence of solar development in agriculturally productive and pristine native ecosystems remain. This study offers insight for how plants respond to novel environmental conditions within a solar array and contextualizes results to inform future array siting, design, and management to realize a sustainable solar energy future.Summary Photovoltaic (PV) solar arrays impose dynamic shading regimes and redistribute precipitation to the ecosystems beneath, leading to spatial and temporal heterogeneity in plant growth environments. Although PV are known to alter ecosystem‐level processes in managed and native landscapes, the control of PV‐induced microenvironments on plant ecophysiological responses are largely unexplored. A more robust and mechanistic understanding of how PV microenvironments control plant response will inform management of existing solar arrays and provide insight for future arrays designed to enhance ecosystem services. Here, we evaluated carbon (photosynthetic parameters) and water relations (daily patterns of leaf water potential (ψL) and stomatal conductance (gsw)) in a C3 perennial grass (Bromus inermis) across PV microsites within a 1.6 ha (1.2 MW) array in semiarid Colorado, USA. Light‐saturated photosynthetic rate was surprisingly consistent spatially, not differing between plants growing in near full sun (between PV rows) versus those growing in shadier microsites beneath panels (~28% of full sunlight). Additionally, plants located in microsites receiving only direct sunlight in the morning, when air temperature and vapor pressure deficits (VPD) were low, had greater ψL and gsw than plants receiving direct sunlight primarily in the hotter drier afternoon. Thus, while soil moisture is a primary control of plant productivity in most water‐limited grasslands, we found that VPD was a better predictor of daily patterns of leaf‐level photosynthetic and water relations responses that control aboveground biomass production in a PV array. These findings provide new mechanistic insight for evaluating vegetation management strategies in semiarid PV arrays.

Cell wall composition and nutritional quality through seasons of the saltgrass Distichlis laxiflora growing in halophytic and mesophytic meadows

The genus Distichlis comprises halophytic perennial C4 grasses which grow in very extreme conditions. It is distributed throughout almost the entire American continent. Despite these interesting characteristics, studies on these plants are relatively scarce, and their ecological and productive value deserves to be further explored. In this work, nutritional aspects, and composition of the cell walls of the aerial part (leaves and shoots) of D. laxiflora Hack were studied. Their changes over four samplings in different seasons, in two nearby sites: a halophytic meadow (H), and a mesophytic meadow (M), were analyzed. Photosynthetic efficiency and K/Na ratio were determined as stress indicators. Plants of sites H and M have similar cell wall content except for spring when plants from site H show lower values. Also, the spring samples present a markedly higher in vitro digestibility for site H. In agreement, samples from site H contain lower amounts of glucuronoarabinoxylans and β-glucans. The protein content is lower in site H, except for spring, and with a maximum in summer for site M. This work shows some changes in the cell walls of D. laxiflora in response to salinity, and these changes influence the digestibility of this material. Spring, coinciding with the regrowth cycle of this plant and with the worst stress indicators, is the season when plants of the halophytic site show the highest nutritional quality for grazing cattle.

Remote sensing reveals fire-driven enhancement of a C4 invasive alien grass on a small Mediterranean volcanic island

Abstract. The severity and the extent of a large fire event that occurred on the small volcanic island of Stromboli (Aeolian archipelago, Italy) on 25–26 May 2022 were evaluated through remotely sensed data to assess the short-term effect of fire on local plant communities. For this purpose, the differenced normalized burned index (dNBR) was also used to quantify the extent of early-stage vegetation recovery dominated by Saccharum biflorum Forssk. (Poaceae), a rhizomatous C4 perennial grass of Paleotropical origin. The burned area was estimated to have an extension of 337.83 ha, corresponding to 27.7 % of the island surface and to 49.8 % of Stromboli's vegetated area. On the one hand, this event considerably damaged the native plant communities, hosting many species of high biogeographic interest. On the other hand, Saccharum biflorum clearly benefited from fire. In fact, this species showed a very high vegetative performance after burning, being able to exert unchallenged dominance in the early stages of the postfire succession. Our results confirm the complex and probably synergic impact of different human disturbances (repeated fires and the introduction of invasive alien plants) on the natural ecosystems of small volcanic islands.

Early impacts of marginal land‐use transition to Miscanthus on soil quality and soil carbon storage across Europe

AbstractMiscanthus, a C4 perennial rhizomatous grass, is a low‐input energy crop suitable for marginal land, which cultivation can improve soil quality and promote soil organic carbon (SOC) sequestration. In this study, four promising Miscanthus hybrids were chosen to evaluate their short‐term potential, in six European marginal sites, to sequester SOC and improve physical, chemical, and biological soil quality in topsoil. Overall, no differences among Miscanthus hybrids were detected in terms of impacts on soil quality and SOC sequestration. SOC sequestration rate after 4 years was of +0.4 Mg C ha−1 year−1, but land‐use transition from former cropland or grassland showed contrasting SOC sequestration trajectories. In unfertilized marginal lands, cultivation of high‐yielding Miscanthus genotypes caused a depletion of K (−216 kg ha−1 year−1), followed by Ca (−56 kg ha−1 year−1), Mg (−102 kg ha−1 year−1) and to a lesser extent of N. On the contrary, the biological turnover of organic matter increased the available P content (+164 kg P2O5 ha−1 year−1). SOC content was identified as the main driver of changes in biological soil quality. High input of labile plant C stimulated an increment of microbial biomass and enzymatic activity. Here, a novel approach was applied to estimate C input to soil from different Miscanthus organs. Despite the high estimated plant C input to soil (0.98 Mg C ha−1 year−1), with significant differences among sites and Miscanthus hybrids, it was not identified as a driver of SOC sequestration. On the contrary, initial SOC and nutrients (N, P) content, as well as their elemental stoichiometric ratios with C, were the key factors controlling SOC dynamics. Introducing Miscanthus on marginal lands impacts positively soil biological quality over the short term, but targeted fertilization plans are needed to secure crop yield over the long term as well as the C sink capacity of this perennial cropping system.

A review of grass species yields and growth rates in Northland, New Zealand

ABSTRACT Pastoral farming is a major land use in New Zealand's Northland region, with 3,171 farm holdings and a total area of 637,500 hectares in 2022. The region's pasture grasses include temperate (C3) and subtropical and tropical (C4) grasses which support dairy, and sheep and beef production from grazing. In lowland areas, C3 and some annual C4 grasses are prevalent where cultivation occurs, while perennial C4 grasses dominate areas with low soil fertility and summer dry conditions. Grass-based pasture growth rates (kg dry matter/ha/day) from published and unpublished sources were assembled into the AgYields database. Among the resident and sown grasses tested in Kaitaia, Kaikohe, Whangarei and Dargaville, perennial ryegrass represented ∼60% of the total data points. Dominant kikuyu pastures represented 23% and the remaining species represented 17%. Rates of growth ranged from 5 to 120 kg DM/ha/day, being lowest in late autumn-winter and highest in early summer. Data were compared and agronomic traits (i.e. drought tolerance, biomass production and tillering) are discussed to assess species suitability for the Northland environment. The medium-term prospect suggests an urgent need to improve research into management of cocksfoot and tall fescue-based pastures to provide viable alternatives to overcome the decreasing persistence of perennial ryegrass.

Response of endophyte‐infected and endophyte‐free tall fescue plants to partial submergence at two developmental stages

AbstractTall fescue (Festuca arundinacea Schreb.) is a perennial C3 grass species usually associated with the endophyte fungus Epichloë coenophiala that enhances tolerance to biotic and abiotic stresses. Given that the proportion of infected tall fescue plants in the grasslands of the Flooding Pampa (Argentina) has been progressively increasing, it is proposed that endophytes confer tolerance to the stresses characteristic of that environment, especially flooding. Plants from a naturalized population and a commercial cultivar were grown, both with and without endophyte (wild type and AR584 respectively). The plants were subjected to two submergence treatments (i.e., control and partial submergence) in two development stages (5‐leaf stage and beginning of the elongation of internodes). Plant performance (aerial and root biomass, root aerenchyma formation, total root length and root diameter, proportion of reproductive tillers, number of panicles and seeds produced) and endophyte transmission to progeny were evaluated. Endophytes did not alter the ecological fitness of plants under partial submergence. Independently of the water condition, the symbiosis was linked to low biomass in plants from the naturalized population, while the opposite occurred in plants from the cultivar. Partial submergence did not affect the germination of the seeds produced, nor the transmission of the endophyte to the seedlings that originated from them. Our work suggests that the invasion ability of tall fescue in the Flooding Pampa grasslands is not related to an endophyte‐mediated improvement of plants to tolerate water excess.

Prescribed fire and exotic plant responses in phreatophytic Sarcobatus vermiculatus rangelands with contrasting degradation

The effects of fire seasonality and prescribed burning on exotic species invasion are poorly understood in black greasewood (Sarcobatus vermiculatus) plant communities of North America. The impacts of reintroducing fire in the fall and spring on community composition and current-year biomass were evaluated at two such sites, one dominated by exotic annual C3 grasses in Miles City, Montana, USA, and one dominated by native perennial C4 grasses in Laramie, Wyoming, USA. Study sites were assessed based on existing Ecological Site Description (ESD) and State-and-Transition Models (STMs) and the Montana site was determined to be more degraded than the Wyoming site. Experimental design was a randomized complete block design with burns conducted in the fall of 2020 and spring of 2021. Exotic species such as Bromus arvensis were reduced by 56% in spring burned plots the following year and by 25% in the fall burned plots over the course of the study in Montana (58.3–43.5%) and Bromus tectorum did not increase in spring or fall burned plots in Wyoming. Accordingly, the proportion of native species in both plant communities remained constant and native perennial C4 grasses such as Sporobolus airoides were resilient to fire. Moreover, burn treatment had no negative effects on plant species richness, evenness, or diversity in either location. Fire treatments had variable effects on current-year biomass with variable influences of drought and season of burn. Prescribed fire, regardless of season, did not exacerbate exotic plant species spread or reduce native species dominance in either location – suggesting that phreatophytic S. vermiculatus rangelands near the eastern terminus of their range are resilient to anthropogenic burning. Future research should investigate the use of prescribed fire with other methods such as revegetation and herbicide application for reducing exotic plant dominance and increasing native plant species.

Plant, insect, and soil microbial communities vary across brome invasion gradients in northern mixed‐grass prairies

Species interactions shape native plant communities, influencing both composition and ecosystem processes, with invasion by non‐native species threatening these dynamic relationships, native species, and function. The consequences of invasive plants in particular may stretch across taxa to impact plant, insect, and soil microbial communities directly and indirectly, with consequences for ecological functioning. In northern mixed‐grass prairies in the United States, invasion by two annual brome grasses, Bromus arvensis and B. tectorum, negatively impacts rangeland plants; however, the simultaneous effects on insects and soil microbes (bacteria and archaea), and the implications for ecological function, have received less attention. Here, using observational field studies conducted at two mixed‐grass prairie sites in Montana and Wyoming, we assessed the relationships between plants, insects, and soil microbes across gradients of invasion by B. arvensis and B. tectorum. Overall, we found differences in plant and insect communities and functional groups with increasing invasion abundance for both brome species. However, associations between invasion and the soil microbial community were species specific, as we only saw these relationships under B. tectorum invasion, implying B. tectorum may have more substantial consequences for rangeland management. While invasion by annual bromes may cause changes in certain plant and insect functional groups, such as C4 perennial grasses and certain insect herbivores, soil microbial functional groups may be less impacted, especially under B. arvensis invasion. This work sheds light on the need to explore changes in natural communities across taxa and to all invasive species, as ecosystem effects are likely to be contingent upon both.

Physiological Responses of C4 Perennial Bioenergy Grasses to Climate Change: Causes, Consequences, and Constraints.

C4 perennial bioenergy grasses are an economically and ecologically important group whose responses to climate change will be important to the future bioeconomy. These grasses are highly productive and frequently possess large geographic ranges and broad environmental tolerances, which may contribute to the evolution of ecotypes that differ in physiological acclimation capacity and the evolution of distinct functional strategies. C4 perennial bioenergy grasses are predicted to thrive under climate change-C4 photosynthesis likely evolved to enhance photosynthetic efficiency under stressful conditions of low [CO2], high temperature, and drought-although few studies have examined how these species will respond to combined stresses or to extremes of temperature and precipitation. Important targets for C4 perennial bioenergy production in a changing world, such as sustainability and resilience, can benefit from combining knowledge of C4 physiology with recent advances in crop improvement, especially genomic selection.

Biomass yield potential on U.S. marginal land and its contribution to reach net‐zero emission

AbstractBioenergy with carbon capture and geological storage (BECCS) is considered one of the top options for both offsetting CO2 emissions and removing atmospheric CO2. BECCS requires using limited land resources efficiently while ensuring minimal adverse impacts on the delicate food‐energy‐water nexus. Perennial C4 biomass crops are productive on marginal land under low‐input conditions avoiding conflict with food and feed crops. The eastern half of the contiguous U.S. contains a large amount of marginal land, which is not economically viable for food production and liable to wind and water erosion under annual cultivation. However, this land is suitable for geological CO2 storage and perennial crop growth. Given the climate variation across the region, three perennials are major contenders for planting. The yield potential and stability of Miscanthus, switchgrass, and energycane across the region were compared to select which would perform best under the recent (2000–2014) and future (2036–2050) climates. Miscanthus performed best in the Midwest, switchgrass in the Northeast and energycane in the Southeast. On average, Miscanthus yield decreased from present 19.1 t/ha to future 16.8 t/ha; switchgrass yield from 3.5 to 2.4 t/ha; and energycane yield increased from 14 to 15 t/ha. Future yield stability decreased in the region with higher predicted drought stress. Combined, these crops could produce 0.6–0.62 billion tonnes biomass per year for the present and future. Using the biomass for power generation with CCS would capture 703–726 million tonnes of atmospheric CO2 per year, which would offset about 11% of current total U.S. emission. Further, this biomass approximates the net primary CO2 productivity of two times the current baseline productivity of existing vegetation, suggesting a huge potential for BECCS. Beyond BECCS, C4 perennial grasses could also increase soil carbon and provide biomass for emerging industries developing replacements for non‐renewable products including plastics and building materials.

δ13C of bulk organic matter and cellulose reveal post-photosynthetic fractionation during ontogeny in C4 grass leaves.

The 13C isotope composition (δ13C) of leaf dry matter is a useful tool for physiological and ecological studies. However, how post-photosynthetic fractionation associated with respiration and carbon export influences δ13C remains uncertain. We investigated the effects of post-photosynthetic fractionation on δ13C of mature leaves of Cleistogenes squarrosa, a perennial C4 grass, in controlled experiments with different levels of vapour pressure deficit and nitrogen supply. With increasing leaf age class, the 12C/13C fractionation of leaf organic matter relative to the δ13C of atmosphere CO2 (ΔDM) increased while that of cellulose (Δcel) was almost constant. The divergence between ΔDM and Δcel increased with leaf age class, with a maximum value of 1.6‰, indicating the accumulation of post-photosynthetic fractionation. Applying a new mass balance model that accounts for respiration and export of photosynthates, we found an apparent 12C/13C fractionation associated with carbon export of -0.5‰ to -1.0‰. Different ΔDM among leaves, pseudostems, daughter tillers, and roots indicate that post-photosynthetic fractionation happens at the whole-plant level. Compared with ΔDM of old leaves, ΔDM of young leaves and Δcel are more reliable proxies for predicting physiological parameters due to the lower sensitivity to post-photosynthetic fractionation and the similar sensitivity in responses to environmental changes.

Environmental influence on reproductive traits of buffel grass facultative apomictic genotypes and its implication in plant breeding

AbstractCenchrus ciliaris L., a perennial C4 grass, is one of the most widely used forage species in warm and dry regions worldwide. The widespread use of the cultivar Texas raises concerns about genetic homogeneity and vulnerability. Hybridizations among facultative individuals could widen the genic pool. Therefore, a reproductive characterization of available genotypes is required. The objective of this study was to determine the reproductive mode, potential sexual expressivity, and seed fertility of four facultative apomictic genotypes throughout the flowering season, considering the influence of bioclimatic variables. We assessed the reproductive mode and potential sexual expressivity using the pistil clearing technique and seed fertility based on the production of seeds per panicle under open pollination and self‐pollination. All the assessed genotypes behaved mainly as out‐crossers throughout the flowering season and showed the highest potential sexual expressivity at the beginning of flowering. We confirmed the environmental influence on reproductive traits. At the beginning of the flowering season, the facultative apomictic genotypes exhibited the highest potential as female parent for hybridizations programs.

Insights into the Ecotoxicology of Radicinin and (10S,11S)-(-)-epi-Pyriculol, Fungal Metabolites with Potential Application for Buffelgrass (Cenchrus ciliaris) Biocontrol.

Buffelgrass (Cenchrus ciliaris L.) is an invasive C4 perennial grass species that substantially reduces native plant diversity of the Sonoran Desert through fire promotion and resource competition. Broad-spectrum herbicides are essentially used for its control, but they have a negative environmental and ecological impact. Recently, phytotoxicity on C. ciliaris has been discovered for two metabolites produced in vitro by the phytopathogenic fungi Cochliobolus australiensis and Pyricularia grisea. They were identified as (10S,11S)-(-)-epi-pyriculol and radicinin and resulted in being potential candidates for the development of bioherbicides for buffelgrass biocontrol. They have already shown promising results, but their ecotoxicological profiles and degradability have been poorly investigated. In this study, ecotoxicological tests against representative organisms from aquatic ecosystems (Aliivibrio fischeri bacterium, Raphidocelis subcapitata alga, and Daphnia magna crustacean) revealed relatively low toxicity for these compounds, supporting further studies for their practical application. The stability of these metabolites in International Organization for Standardization (ISO) 8692:2012 culture medium under different temperatures and light conditions was also evaluated, revealing that 98.90% of radicinin degraded after 3 days in sunlight. Significant degradation percentages (59.51-73.82%) were also obtained at room temperature, 30 °C or under ultraviolet (254 nm) light exposure. On the other hand, (10S,11S)-epi-pyriculol showed more stability under all the aforementioned conditions (49.26-65.32%). The sunlight treatment was also shown to be most effective for the degradation of this metabolite. These results suggest that radicinin could provide rapid degradability when used in agrochemical formulations, whereas (10S,11S)-epi-pyriculol stands as a notably more stable compound.

Grazing Intensity and Seasonality Manipulate Invasive Annual Grasses and Native Vegetation

Simultaneous desires for greater livestock production and reduced purchased feed inputs are further complicated by potential for rangeland degradation and weed invasion. Grazing management that emphasizes greater use of dormant rangeland forages may provide solutions. We tested grazing season (summer or fall) and intensity (moderate or heavy) combination effects on plant community composition and productivity to determine whether rangelands can sustain heavy dormant-season use without reducing native perennials. Treatment combinations were randomly assigned to 20, 60 × 30 m plots that were grazed from 2013 through 2017. Total current-yr biomass was greatest with moderate fall grazing (1 350 ± 41 kg ha−1) and similar among heavy fall, heavy summer, and moderate summer grazing (1 206 ± 41 kg ha−1). Heavy summer grazing had the lightest native species standing crop. Heavy summer grazing reduced perennial C3 grass standing crop 22%, primarily through effects on needle-and-thread (Hesperostipa comata [Trin. & Rupr.] Barkworth) and threadleaf sedge (Carex filifolia Nutt.). Moderate dormant fall grazing increased perennial C3 grass standing crop 15% but also increased the invasive annual, Japanese brome (Bromus japonicus Thunb.). Heavy dormant fall grazing effects did not differ from that of moderate summer grazing for perennial C3 grass or total native species standing crop, but heavy fall grazing reduced cheatgrass (Bromus tectorum L.) 51%. Where B. japonicus and B. tectorum co-occur, moderate growing season grazing combined with heavy dormant fall grazing may be needed to affect both species. Diversity and native species standing crop were similar between heavy fall and moderate summer grazing, but heavy fall grazing caused the least non-native species standing crop. Heavy fall use is recommended as potential treatment to be rotated among pastures over time or focused on pastures that could benefit from effects observed. Effects likely vary with differences in climate or species composition.

Seasonal water source patterns in a northern Arizona pine forest

The relationships among stand density and seasonal plant water source patterns in ponderosa pine (Pinus ponderosa) forests are important for informed management decisions in a bimodal climate with increasing variability in winter and monsoon precipitation inputs. Winter precipitation recharges soil moisture, yet it has declined over the past 20 years in the southwestern United States, and monsoon precipitation is becoming more variable in both magnitude and timing. Near Flagstaff, Arizona in August 2013 (monsoon), October 2013 (post-monsoon), and May 2014 (post winter snow melt), we measured soil moisture, soil water δD at five depths, and xylem water δD in Muhlenbergia montana (a perennial C4 grass), Festuca arizonica (a perennial C3 grass), and P. ponderosa seedlings (< 2 years old), saplings (2–5 cm basal diameter), and mature trees (> 60 cm diameter at breast height) in treated (thinned and burned) and untreated (no thinning, no burning) stands. We found that soil moisture was higher at all soil depths in treated stands in May, after snow melt, and this pattern persisted through August in the deepest soil (60 cm). We also found that, in all sampling months, δD in xylem water of grasses and pine seedlings indicated use of shallower soil water than for pine saplings and mature trees, presumably due to differences in rooting depths. Additionally, in August, δD in xylem water of pine saplings and mature trees indicated greater reliance on a deeper water source in untreated stands than in treated stands, likely due to greater competition for shallow water in untreated stands. Our isotopic data indicate that grasses and seedlings used predominantly monsoon water in August and October, while pine saplings and mature trees used predominantly winter water during all sampling months. Importantly, our data indicate that regenerating trees (seedlings and saplings) used both winter and monsoon seasonal water sources, suggesting an increasingly important role for monsoon precipitation if winter precipitation inputs continue to decline. Collectively, these findings demonstrate that management actions can benefit forests via increased soil moisture, that overstory trees rely predominantly on winter precipitation, and that monsoon precipitation is important for herbaceous species and younger, regenerating overstory trees.

Photosynthetic resource-use efficiency trade-offs triggered by vapour pressure deficit and nitrogen supply in a C4 species

Trade-offs in resource-use efficiency (including water-, nitrogen-, and light-use efficiency, i.e., WUE, NUE, and LUE) are an important acclimation strategy of plants to environmental stresses. C4 photosynthesis, featured by a CO2 concentrating mechanism, is believed to be more efficient in using resources compared to C3 photosynthesis. However, response of photosynthetic resource-use efficiency trade-offs in C4 plants to vapour pressure deficit (VPD) and N supply has rarely been studied. Here, we studied the photosynthetic acclimation of Cleistogenes squarrosa, a perennial C4 grass, to controlled growth conditions with high or low VPD and N supply. High VPD increased WUE by 12% and decreased NUE by 16%, the ratio of net photosynthetic rate (A) to electron transport rate (J) (A/J) by 7% and the apparent quantum yield by 6%. High N supply tended to reduce NUE and increased maximum phosphoenol pyruvate carboxylation rate by 71% and slightly increased WUE. Stomatal conductance showed acclimation to VPD according to the Ball-Berry model, while a balanced cost of carboxylation and transpiration capacity was found across VPD and N treatments based on the least-cost model. WUE correlated negatively with NUE and LUE indicating that there was a trade-off between them, which is likely associated with acclimations in stomatal conductance and CO2 concentrating mechanisms.

Rehabilitating Invaded Rangeland in Central South Dakota with Grazing, Seeding, and Herbicides

Rangelands in the northern Great Plains are threatened by invasive C3 annual and perennial grasses that displace native C4 grasses. Rehabilitating these rangelands by reintroducing native C4 grass species could extend the season in which relatively higher-quality forage is available for livestock grazing and improve wildlife habitat. Three seeding treatments, four herbicide treatments, and two stocking densities were applied to a pasture in central South Dakota, United States, that was dominated by invasive C3 grasses. Grazing and herbicide treatments were designed to suppress exotic cool season grasses. Drought limited establishment during the first 2 yr, but C3 grasses were successfully controlled during this time. Plots drill-seeded and sprayed with glyphosate established a mean of 1.0 seeded grasses m−2 by the third yr. Unseeded plots and plots that did not receive glyphosate failed. This trend continued into yr 5, when the most successful treatments were composed of 10−14% seeded C4 grasses, as determined by a modified step-point count technique. Stocking density did not affect establishment success. It is possible to suppress C3 invasive grasses with herbicide and establish native C4 tallgrasses in central South Dakota, but drought makes it a risky proposition in this semiarid region.

Effect of Seawall Embankment Reclamation on the Distribution of Cr, Cu, Pb and Zn Pollution in Invasive Spartina alterniflora and Native Phragmites australis Coastal Saltmarshes of East China.

Coastal reclamation by seawall embankments and the spread of invasive C4 perennial grass Spartina alterniflora have recently become more prevalent in eastern China's coastal wetlands. While trace metals (TMs), carbon, and nitrogen dynamics concerning reclamation have extensively been explored across China's coastal wetlands, to date, the impact of reclamation by coastal embankment and exotic plant invasion on TMs' pollution dynamics in coastal marshes remains largely unexplored. We compared TMs Cr, Cu, Pb, and Zn cumulation in coastal embankment-reclaimed versus unreclaimed S. alterniflora and Phragmites australis saltmarshes in eastern China coastal wetlands. In both S. alterniflora and P. australis marshes, coastal embankment reclamation spurred an increase in Cr, Cu, Pb, and Zn concentrations by 31.66%, 53.85%, 32.14%, 33.96% and by 59.18%, 87.50%, 55.55%, 36.84%, respectively, in both marsh types. Reclamation also reduced plant biomass, soil moisture, and soil salinity in both plants' marshes. Our findings suggest that the impact of coastal embankment reclamation and replacement of native saltmarshes by invasive S. alterniflora had a synergistic effect on TM accumulation in the P. australis marshes, as corroborated by bioaccumulation and translocation factors. Reclamation by coastal embankments and invasive alien plants could significantly impair the physico-chemical properties of native plant saltmarsh and essentially weaken the accumulation of Cr, Cu, Pb, and Zn potential of the coastal saltmarshes. Our findings provide policymakers with an enhanced knowledge of the relationship between reclamation, plant invasiveness, and TM pollution dynamics in coastal wetlands, providing a baseline for attaining future goals and strategies related to the tradeoffs of various wetland reclamation types.

Effect of irrigation on biomass production and components of dallis grass (Paspalum dilatatum) and Bahia grass (P. notatum) in Uruguay

Use of irrigation in forage production systems based on perennial C4 grasses has been limited because of inconsistent responses of biomass production to water. The effects of three different levels of irrigation on growth of Paspalum notatum (Bahia grass) and P. dilatatum (dallis grass) over two consecutive growing seasons were studied. The phenological state of the plants was inferred by the proportion of lamina and non-lamina components. While irrigation failed to increase annual dry matter yield of forage, phenological composition of forage was affected by irrigation with both species showing changes in distribution of dry matter accumulation among different above-ground plant parts. Future research on these species should study the effects of moisture deficit on phenology to better understand the effects of irrigation.

Yield performance of 14 novel inter‐ and intra‐species Miscanthus hybrids across Europe

AbstractMiscanthus, a C4 perennial rhizomatous grass from Asia is a leading candidate for the supply of sustainable biomass needed to grow the bioeconomy. European Miscanthus breeding programmes have recently produced a new range of seeded hybrids with the objective of increasing scalability to large acreages limited by current clonal propagation. For the EU‐GRACE project, new replicated field trials were established in seven locations across Europe in 2018 with eight intraspecific M. sinensis hybrids (sin × sin) and six M. sacchariflorus × M. sinensis (sac × sin) from Dutch and UK breeding programmes, respectively, with clonal Miscanthus × giganteus. The planting density of the sin × sin was double that of sac × sin (30,000 & 15,000 plants ha−1), creating commercially relevant upscaling comparisons between systems. Over the first 3 years, the establishment depended on location and hybrid. The mature sin × sin hybrids formed tight tufts of shoots up to 2.5 m tall which flower and senesce earlier than the taller sac × sin hybrids. Following the third growing season, the highest yields were recorded in Northern Italy at a low altitude (average 13.7 (max 21) Mg DM ha−1) and the lowest yielding was on the industrially damaged marginal land site in Northern France (average 7.0 (max 10) Mg DM ha−1). Moisture contents at spring harvest were lowest in Croatia (21.7%) and highest in Wales, UK (41.6%). Overall, lower moisture contents at harvest, which are highly desirable for transport, storage and for most end‐use applications, were found in sin × sin hybrids than sac × sin (30% and 40%, respectively). Yield depended on climate interactions with the hybrid and their associated planting systems. The sin × sin hybrids appeared better adapted to northern Europe and sac × sin hybrids to southern Europe. Longer‐term yield observations over crop lifespans will be needed to explore the biological (yield persistence) and economic costs and benefits of the different hybrid systems.