Plant Regrowth Research Articles

Combining a field experiment and literature to model the regrowth probability of perennial storage organs fragmented by tillage: Case study of Cirsium arvense (L.) Scop

Management of perennial weeds has become increasingly difficult with the reduction of herbicide use. Creeping perennials accumulate reserves in specialized belowground organs from which they regenerate new plants after a disturbance. Through tool selection, tillage operations could be optimized to reduce perennial-weed reserves and limit regeneration. In the present study, the effect of five tools on the fragmentation of the creeping roots of Cirsium arvense (L.) Scop. (Canada thistle), a major perennial weed in arable crops, were analysed. A field trial was set up to measure the lengths of the root fragments left after tillage. Five tools were tested: mouldboard ploughing, rotary harrow, disc harrow, rigid-tine cultivator and goose-foot cultivator. Fragment-length distribution varied according to the tool: rotary harrow left the smallest (3.7 cm on average) and least variable fragment lengths, mouldboard ploughing the longest (12.7 cm) and most variable ones. The other tools produced intermediate-sized fragments (8–10 cm). Based on these results and literature, a model was proposed to predict perennial-weed regeneration probability from storage-organ fragments after one tillage run. The effects of six factors, which were agronomic (tillage tool), environmental (soil conditions and temperature) and biological (storage-organ fragment diameter, maximal belowground-shoot length and pre-tillage storage-organ distribution), were tested through a sensitivity analysis. According to the model, the probability of fragment regeneration success is lower for the rotary harrow than for the mouldboard plough. The most important drivers of fragment regeneration success were the biological traits: fragment diameter and maximal belowground-shoot length per unit fragment biomass. The present model should be complemented to predict the effect of tillage on perennial-weed regrowth and help improving non-chemical weed-management strategies. To achieve this, further research is needed on plant regrowth potential from storage organs and their architecture in the soil.

Waterlogging‐Induced Changes in ABA, Carbohydrates and CBF6 Modify Freezing Tolerance in Prehardened Festuca pratensis

ABSTRACTChanges in precipitation and snow melt during warmer winters can increase low‐temperature waterlogging. Such conditions may bring about different effects when compared with a single stress trigger, such as low‐temperature or water excess. The effects of waterlogging are clearly related to water temperature, and the consequences of water excess might be less severe, as more oxygen is dissolved in colder water. The effect of waterlogging during cold acclimation (CA) is poorly understood; most experiments concerning water excess are performed at relatively high‐temperatures. In this study, we examined the effect of 3 weeks of waterlogging (approx. 2 cm above the soil level) on CA in Festuca pratensis Huds. (Fp), a cool‐season grass. Measurements were taken before CA (after prehardening, before flooding) and after 3 weeks of CA in waterlogged (treated) and non‐waterlogged (control) plants. The work included: (i) freezing tolerance test (regrowth after freezing), (ii) analysis of abscisic acid (ABA) content in the leaf, (iii) leaf stomatal conductance, (iv) leaf water content, (v) carbohydrates analysis, including fructans, and (vi) transcript levels of selected genes involved in freezing tolerance, ABA signalling and fructan biosynthesis. The aim of the study was to test a hypothesis that low‐temperature waterlogging in Fp enhances freezing tolerance (plant regrowth after freezing) related to increased ABA accumulation, increased C‐repeat‐binding transcription factor expression and/or increased carbohydrate accumulation, including fructans. Two out of four genotypes exhibited enhanced regrowth following freezing due to waterlogging relative to control. Principal component analysis (PCA) revealed a positive correlation between ABA levels and freezing tolerance in both treatments, with a more pronounced effect observed in the waterlogged plants. However, the phytohormone played different roles in these two treatments. In the context of low‐temperature waterlogging, ABA may be involved in the dehydration tolerance response in genotypes suffering from physiological drought, as well as the induction of C‐repeat‐binding transcription factors (CBFs) and sucrose, which may improve freezing tolerance. The increased fructan amount and polymerisation degree due to waterlogging may provide a carbohydrate sink to maintain a high photosynthetic efficiency, but are not directly responsible for freezing tolerance changes. The study indicates that tolerance mechanisms of Fp exposed to low‐temperature waterlogging involve maintaining a high photosynthetic rate, as well as oxidative and dehydration stress tolerance.

Warming effects on plant regrowth after clipping are modified by repeated clipping in Mongolian pasture species

Warming effects on plant regrowth after clipping are modified by repeated clipping in Mongolian pasture species

Winter survival in red clover: experimental evidence for interactions among stresses

BackgroundThere is a lack of knowledge on the combined effects of different stresses on plants, in particular different stresses that occur during winter in temperate climates. Perennial herbaceous plants in temperate regions are exposed to many different stresses during winter, but except for the fact that cold temperatures induce resistance to a number of them, very little is known about their interaction effects. Knowledge about stress interactions is needed in order to predict effects of climate change on both agricultural production and natural ecosystems, and to develop adaptation strategies, e.g., through plant breeding. Here, we conducted a series of experiments under controlled conditions to study the interactions between cold (low positive temperature), clover rot infection (caused by Sclerotinia trifoliorum) and freezing, in red clover (Trifolium pratense) accessions. We also compared our results with winter survival in field experiments and studied associations between stress and shoot growth.ResultsExposure to low positive temperatures (cold acclimation) induced resistance to clover rot. There was a clear negative interaction effect between freezing stress and clover rot infection, resulting in up to 37% lower survival rate compared to what would have been expected from the additive effect of freezing and infection alone. Freezing tolerance could continue to improve during incubation under artificial snow cover at 3 °C in spite of darkness, and we observed compensatory shoot growth following freezing after prolonged incubation. At the accession level, resistance to clover rot was negatively correlated with growth in the field during the previous year at a Norwegian location. It was also negatively correlated with the shoot regrowth of control plants after incubation. Clover rot resistance tests under controlled conditions showed limited correlation with clover rot resistance observed in the field, suggesting that they may reveal variation in more specific resistance mechanisms.ConclusionsWe here demonstrate, for the first time, a strong negative interaction between freezing and infection with a winter pathogen. We also characterize the effects of cold acclimation and incubation in darkness at different temperatures on winter stress tolerance, and present data that support the notion that annual cycles of growth and stress resistance are associated at the genetic level.

Dry Season Biomass Production of Leucaena lecocephala cv Tarramba at 4 months regrowth and from Several Longer Regrowth Plants on Sandy Vertisol Soil at Naibonat, West Timor-Indonesia

Dry Season Biomass Production of Leucaena lecocephala cv Tarramba at 4 months regrowth and from Several Longer Regrowth Plants on Sandy Vertisol Soil at Naibonat, West Timor-Indonesia

Immunological structure and yield of winter rye varieties bred by the Federal Agricultural Research Center of the North-East named N. V. Rudnitsky

The study was carried out in the conditions of Kirov region in 2019–2023. Against provocative and infectious backgrounds of snow mold, root rot, ergot, powdery mildew, leaf and stem rust, the immunological state and yield of 15 varieties of winter rye created over a 73-year period were studied. Taking into account the breeding methods, the source material used and the year of creation, they were conditionally distributed over five successive periods of breeding and variety change: I – Vyatka 2, Kirovskaya 89; II – Falenskaya 4, Snezhana, Rushnik; III – Flora, Grafinya, Batist; IV – Lika, Talitsa; V – Symphoniya, Garmoniya, Graphit, Graphit FP, Perepel. When recording diseases, well-known methods were used. Research has shown that as a result of breeding, on artificial infectious backgrounds newly created varieties showed a decrease in the development of root rot (Flora, Perepel, Garmoniya – degree of damage 14.6, 15.5 and 15.0 %) and ergot (Flora, Grafinya, Batist, Lika, Symphoniya, Graphit FP, Garmoniya – damage 11.4...15.9 %), grain contamination with sclerotia – 0.38...1.84 %. In varieties of the I period of breeding the degree of root rot infection was 18.8 %, ergot infection – 31.7 %. There is no progress in breeding for resistance to powdery mildew and rust types. The most productive varieties are Lika and Batist (769.3 and 738.7 g/m2), which significantly exceed the Falenskaya 4 standard (578.8 g/m2). A close and significant dependence (p ≥ 095) was revealed between the yield of winter rye varieties and regrowth of plants after snow mold infection (r = 0.693...0.830) as well as grain contamination with sclerotia (r = -0.531...-0.712). The relationship between the yield of winter rye and the development of other studied diseases is insignificant and weak. Considering the high harmfulness of snow mold and ergot in the research region, it is necessary to continue to carry out breeding improvement of varieties for these characteristics, as well as to increase resistance to powdery mildew and types of rust.

Restricted plant diversity limits carbon recapture after wildfire in warming boreal forests

Incomplete wildfire combustion in boreal forests leaves behind legacy plant-soil feedbacks known to restrict plant biodiversity. These restrictions can inhibit carbon recapture after fire by limiting ecosystem transition to vegetation growth patterns that are capable of offsetting warmth-enhanced soil decomposition under climate change. Here, we field-surveyed plant regrowth conditions 2 years after 49 separate, naturally-occurring wildfires spanning the near-entire climatic range of boreal Fennoscandia in order to determine the local to regional scale drivers of early vegetation recovery. Minimal conifer reestablishment was found across a broad range of fire severities, though residual organic soil and plant structure was associated with restricted growth of a variety of more warmth-adapted vegetation, such as broadleaf trees. This dual regeneration limitation coincided with greater concentrations of bacterial decomposers in the soil under increased mean annual temperature, potentially enhancing soil carbon release. These results suggest that large portions of the boreal region are currently at risk of extending postfire periods of net emissions of carbon to the atmosphere under limitations in plant biodiversity generated by wildfire and a changing climate.

Adapting service crop termination strategy in viticulture to increase soil ecosystem functions and limit competition with grapevine

Soil management and particularly service crops are a promising solution for addressing current challenges in viticulture as they limit the use of herbicides while increasing potential ecosystem services. Scientific literature barely considers the importance of service crop management to reach trade-offs between ecosystem services and disservices. This study evaluates during a three-year experiment, 6 service crop termination strategies for winter service crops, combining two service crops termination periods (early termination in February vs. termination at grapevine budburst) and three termination methods (mower (M), mower + tillage (T), roller-crimper (R)). Service crop (biomass, C:N ratio, weeds, and mulch following termination), soil ( soil organic matter, microbial biomass, and water and nitrogen stocks), and grapevines (predawn leaf water potential, yield components, δ13C, yeast assimilable nitrogen in juice, and pruning weight) were monitored from 2019 to 2022. Allowing service crops to develop until the budburst of the vine resulted in a two to three-fold increase in biomass compared to early destruction. Termination involving soil tillage was the most effective method, as treatments destroyed early with soil tillage exhibited almost no regrowth. Soil tillage termination led to the lowest biomass of weeds at the grapevine flowering two years out of three, and prevented the regrowth of certain sown plants, especially Poaceae. The roller was less effective in destroying service crop species but was the best method for maintaining plant residues on the soil surface. A higher soil microbial biomass was observed with termination at budburst, combined with no-till termination methods. Termination involving soil tillage was notably more effective in stopping service crop transpiration, increasing soil water stocks and improving grapevine water status. In 2020 and 2022, soil inorganic nitrogen stocks were almost 4 times higher in the T treatments compared to the other two termination methods, achieving a level of approximately 61 kg ha−1 that closely corresponds to the annual nitrogen requirements of grapevines. The yeast-assimilable nitrogen (YAN) content in grape juice mirrored this trend. Pruning weight varied significantly between different termination methods, with T treatments exhibiting a higher pruning weight per vine in comparison to R and M treatments. In general terms, the T treatment had a significantly higher number of bunches, the M treatment had the lowest, and the R treatment exhibited intermediate values. Overall, the average grapevine yield ranged from 7.25 to 13.7 t ha−1, corresponding to 52–98 hL ha−1 (with 4000 vines ha−1, 140 kg hL−1). This level of production may be accepted for Protected Designations of Origin that limit grapevine yield to 40 or 60 hL ha−1, but it could be a limitation for Protected Geographical Indications, which permit 90 hL ha−1, or unlabeled productions without yield limitations. Given the Mediterranean climate context, with rising frequencies of dry winters due to climate change, termination involving soil tillage appears to be the least risky strategy to preserve grapevine vigor and production while improving soil-based ecosystem functions. However, this might be contingent on the targeted yield and wine valuation.

Populus euphratica has stronger regrowth ability than Populus pruinosa under salinity stress.

Pest infestation and soil salinization levels are increasing due to climate change. Comprehending plant regrowth after insect damage and salinity stress is crucial to understanding climate change's multifactorial impacts on forest ecosystems. This study examined Populus euphratica and P. pruinosa regrowth after different defoliation levels combined with salinity stress. Specifically, the biomass and regrowth ability, non-structural carbohydrate (NSC) and nitrogen (N) pools in different organs and the whole plant, and the leaf Cl- concentration of both poplars were analyzed. Our results showed that after 50% defoliation and no salt addition, the regrowth of both species recovered similarly to the control level, while their regrowth was about 70% after 90% defoliation. However, under salinity stress, the regrowth (% leaf biomass) of P. euphratica was significantly higher than P. pruinose at either the 50% or 90% defoliation levels. Additionally, P. euphratica had more soluble sugar, starch, NSC and N pools in leaf, stem, root and whole plant than P. pruinose under salinity stress. The regrowth based on leaf biomass increased linearly with soluble sugar, starch, NSC and N pools, and decreased linearly with leaf Cl- concentration across different salinity and defoliation levels. These results indicated that defoliation significantly decreased NSC and N pools, limiting the growth of both poplars, and salinity stress exacerbated the negative effect. Furthermore, when suffering from salinity stress, P. euphratica with higher NSC and N pools exhibited stronger regrowth ability than P. pruinose.

Livestock farming sustainability and forage production in volcanic-hazard prone areas of Indonesia’s active volcano

Volcanic eruptions have varied and complex impacts on small-scale livestock farming located in volcanic hazard-prone areas due to diverse stock, rearing, and feeding practices. The study was aimed to clarify the critical factors for designing forage recovery and sustainable livestock production in highrisk-prone areas of active volcanic mountains. A total of seventy-five ruminant livestock farmers located in the eruption-impacted areas of five active volcanoes were surveyed on flock size, rearing, and feeding practices. They were interviewed about their experiences of the eruption's impact on the animals, forage feed, and livestock mitigation regarding survival efforts. Forage plants and soil samples were collected to analyze dry matter and crude nutrient composition and estimate the botanical composition, biomass production, and carrying capacity. Results showed that there were five species of ruminant animals reared in small flock size (< 7 heads/farm): beef cattle, buffalo, horses, goat, and sheep. Beef cattle and goats were the most popular farm animals raised in different breeds, rearing, and feeding systems. The volcanic eruption caused animal loss and health problems due to exposure to volcanic materials, forage damages, and animal mitigation constraints, resulting in flock size decrease and economic loss. The impact of the eruption on farm animals and forage plants varied among the volcanoes due to diverse eruptive characteristics, stock breed, rearing, and feeding practices. Livestock farming recovery post-eruption depended largely on the survival flock and the regrowth of forage plants. In conclusion, sustainable beef cattle farming in volcanic hazard-prone areas might be realized by effective livestock mitigation efforts, selecting appropriate types of animals and rearing/feeding systems based on agroecological conditions, and improving forage capacity and survival rate during and posteruption.

Maintaining grain yield of Th. intermedium across stand age through constant spike fertility and spike density: Understanding its response to various agronomic managements

Thinopyrum intermedium subsp. intermedium (Host) Barkworth & D.R. Dewey is a perennial grass proposed as a dual-use crop for both forage and grain. Being in the nascent stage of domestication, its grain yield potential is still low compared to annual counterparts. The understanding of Th. intermedium development and the resulting grain yield in field is limited along with its response to agronomic management. To identify the interrelations between development traits and their influence on grain yield, various crop measurements were evaluated during four growing seasons in field grown Th. intermedium conducted under various autumn defoliation operations and nitrogen (N) fertilizations. Under sufficient N treatments (i.e., 100 kg N ha−1), grain yield remained constant over the four years of the experiment with a mean of 1 t ha−1 resulting from a constant spike fertility and a spike density level above 400 spikes m−2. However, significant mortality and inhibition of reproductive growth of tillers can occur when number of tillers is too high and/or resources too scarce (e.g., unfertilized plots or water deficiencies). In addition, excessive aboveground production at the beginning of the reproductive phase can be detrimental to the final grain yield through the negative influence of tiller density and aboveground biomass (DM) on the yield per spike. The highest aboveground production was observed during the second year with 1415 tillers m−2 at the beginning of the reproductive phase and 16 t of DM ha−1 at grain harvest. Although grain yield response to N fertilization was positively associated to spike density, excessive aboveground biomass could be enhanced by N fertilization. The fertilization of 50 kg ha−1 in autumn combined with a fertilization of 50 kg ha−1 in early-spring could sustain tiller fertility without hampering grain production. In autumn, plant regrowth was low with the highest value of 1.3 t of DM ha−1 observed in the first year. Autumn defoliation could be used to maintain the yield per spike in case of excessive biomass production by the reduction of the DM and the final tiller density coupled with the increase of the grain weight the next year. Finally, shredding post-harvest crop residues at ground level to promote light penetration at the bases of plants may have a positive influence on the tiller fertility. Therefore, under fertile soil conditions (i.e., deep soils and sufficient N fertilization) combined with an optimal stand establishment (i.e., from 500 to 1000 tillers m−2 at the beginning of the growing season) we demonstrated that grain yield potential can be maintained as the crop ages. In the future, breeding should raise resource allocation to the grain by increasing yield per spike and avoid overproduction of new tillers through tillering or rhizome propagation without compromising the vigor of regrowth and its environmental performance.

Extrafloral Nectary-Bearing Plants Recover Ant Association Benefits Faster and More Effectively after Frost-Fire Events Than Frost.

The Cerrado confronts threats such as fire and frost due to natural or human-induced factors. These disturbances trigger attribute changes that impact biodiversity. Given escalating climate extremes, understanding the effects of these phenomena on ecological relationships is crucial for biodiversity conservation. To understand how fire and frost affect interactions and influence biological communities in the Cerrado, our study aimed to comprehend the effects of these two disturbances on extrafloral nectar (EFN)-bearing plants (Ouratea spectabilis, Ochnaceae) and their interactions. Our main hypothesis was that plants affected by fire would grow again more quickly than those affected only by frost due to the better adaptation of Cerrado flora to fire. The results showed that fire accelerated the regrowth of O. spectabilis. Regrowth in plants with EFNs attracted ants that proved to be efficient in removing herbivores, significantly reducing foliar herbivory rates in this species, when compared to the species without EFNs, or when ant access was prevented through experimental manipulation. Post-disturbance ant and herbivore populations were low, with frost leading to greater reductions. Ant richness and diversity are higher where frost precedes fire, suggesting that fire restores Cerrado ecological interactions better than frost, with less impact on plants, ants, and herbivores.

Unveiling the dual role of heterotrophic ammonia-oxidizing bacteria: enhancing plant regrowth through modulating cytokinin delivery.

This study aims to investigate the dual impacts of heterotrophic ammonia-oxidizing bacteria (HAOB) strains on the regrowth of Italian ryegrass by studying cytokinin delivery from roots to leaves. The dual impacts encompass both the "soil-inside-role" and "soil-outside-role," which refer to the HAOB operating inside and outside the rhizosphere soil within the rhizosphere microenvironment. The experimental design consisted of two sets of experiments, Exp-1 and Exp-2, involving different treatments. In Exp-1, various concentrations of NO3- were added to the roots to observe the soil-inside-role on cytokinin delivery from roots to leaves. In Exp-2, NO3- addition was combined with HAOB inoculation to observe the combined effects of the root-outside-role and root-inside-role on cytokinin synthesis and transport. The results indicated that NO3- concentrations ranging from 30 to 40 mmol L-1 had the most optimal effect on increasing leaf cytokinin content and delivery from roots to leaves, consequently promoting greater leaf regrowth biomass. When inoculated, the HAOB strain significantly increased rhizosphere soil nitrification rates under the soil-inside-role, leading to increased NO3- release from the soil and a subsequent boost in cytokinin delivery from roots to leaves. Additionally, the HAOB strain independently enhanced cytokinin delivery from roots to leaves outside the rhizosphere soil within the rhizosphere microenvironment, demonstrating its soil-outside-role. The combined effects of the soil-inside-role and soil-outside-role substantially increased leaf cytokinin content, playing a crucial role in promoting Italian ryegrass regrowth. The study's findings shed light on the mechanisms through which HAOB can enhance plant growth by performing dual roles in the rhizosphere, offering potential applications in agriculture. Understanding the interaction between HAOB, cytokinins, and plant growth could lead to more effective strategies for improving crop productivity and promoting sustainable agriculture.

Native and non‐native plant regrowth in the Santa Monica Mountains National Recreation Area after the 2018 Woolsey Fire

AbstractMediterranean‐type ecosystems are under chronic ecological stress. By assessing changes in plant species and functional groups across the landscape, identifying ecosystem degradation is possible. The Santa Monica Mountains are in close proximity to a densely populated urban area where non‐native species invasions are being driven by changing fire regimes, climate change, and anthropogenic disturbances. Non‐native growth impacts biodiversity levels and vegetation distributions of native plant communities that are critical for ecosystem health. This study uses analyses of line‐point data from the National Park Service Inventory and Monitoring Program to assess ecosystem health in the Santa Monica Mountains from 2014 to 2020 and, in particular, to assess the effects of the 2018 Woolsey Fire on the balance of native and non‐native species in the region. Results of this analysis show an increase in non‐native cover since 2014 and rapid regrowth of non‐native annual grasses and herbaceous cover after the 2018 Woolsey Fire while native communities regrew more slowly. A hotspot of non‐native cover was identified in the Northern Simi Hills region, and rapid regrowth was seen after the Woolsey Fire. The hotspot is dominated by non‐native annual grasses and annual herbaceous species, some of which returned to prefire populations within a year after the Woolsey Fire. These results raise concerns for the future of native vegetation composition and function throughout the park and highlight the damage densely populated non‐native plant communities accumulate in the wake of disturbance events.

Sandy silt loam soil may hamper the inoculation effect on lucerne (Medicago sativa L.) growth

ABSTRACT Despite newly approved lucerne cultivars, this has not led to increased use of this legume in high-latitude agriculture. Challenges with inoculation by Rhizobium meliloti have been identified as a bottleneck to adaptation. Here we tested inoculation sources (ISs) with soil types and cultivars in pot and field experiments. During a one-year outdoor pot experiment, we tested the impact of IS (wet peat slurry and Nitragin Gold dry inoculation) and three soil types (sand, sandy silt and /peat soil) on nodule development, shoot and root growth and winter survival of one hybrid lucerne cultivar (‘Ludvig’). The pot experiment revealed that dry inoculation led to significant better plant growth, flower and nodule development as well as plant regrowth after winter survival. Peat soil appeared as the best growth medium and silty soil limited inoculation efficiencies. In field trials at two locations differing in soil characteristics using similar ISs, and three hybrid lucerne cultivars (‘Lavo’, ‘Live’ and ‘Lotte’) biomass yield during two ley years showed site as well as cultivar differences. Such environmental interactions in the field trials justify the use of adapted cultivars, and dry inoculation should be recommended for practical use replacing peat slurry inoculation.

Growth characteristics and post trimming regrowth potential of tropical and sub-tropical landscape hedge plants in response to spacing

Spacing of landscape plants is one of the factors determining the outcome of a design in terms of canopy formation which is one of the variables for aesthetic appearance in terms of shapes and forms. This study was conducted between September 2016 and September 2017, to determine the appropriate intra-row spacing for five plant species in hedge formation. The plant species used were Duranta erecta, Hamelia patens, Ficus retusa, Buxus sempervirens and Acalypha wilkesiana. Transplanting was done at intra-row spacing of 30, 40, 50 and 60cm and a constant inter-row spacing of 100cm. The experiment was a Randomized Complete Block Design in split plot arrangement with three replicates. Plant height, number of leaves, number of branches and canopy space, as indices of species suitability for use as hedge, were measured fortnightly. Plant regrowth and aesthetic characteristics were assessed after periodic trimming. H. patens and B. sempervirens species had the tallest plants. B. sempervirens and D. erecta produced the highest number of leaves while D. erecta and H. patens had the highest number of branches. D. erecta had significantly (p<0.05) the fastest post-trimming shoot regrowth rate relative to other species following the 1st and 2nd trimming (25 and 28 WAT respectively). The effect of spacing on shoot regrowth length was significant after the 3rd, 4th and 5th trimmings (31, 34 and 37 WAT respectively). The highest shoot regrowth height was recorded at 40cm spacing followed by 30cm intra row spacing. All species responded best at 50cm intra-row spacing for the number of branches and canopy space as well as early hedge formation. The study concluded that B. sempervirens was suitable for ideal hedging at 40cm intra-row spacing while A. wilkiesiana and H. patens were only suitable as informal hedges. Hence, B. sempervirens species is recommended as the ideal hedge plant choice based on its early regrowth after trimming, high leaf and branch production as well as overall speed in hedge formation at 31WAT.

Low carrier volume herbicide trials and UAAS support management efforts of giant salvinia (Salvinia molesta): a case study

AbstractExpanding the current aquatic herbicide portfolio, reducing total spray volumes, or remotely delivering herbicide using novel spray technologies could improve management opportunities targeting invasive aquatic plants, where options are more limited. However, research on giant salvinia (Salvinia molesta Mitchell) response to foliar herbicide applications at carrier volumes ≤140 L ha−1 is incomplete. Likewise, no data exist documenting S. molesta control with unoccupied aerial application systems (UAAS). Following the recent >100-ha incursion of S. molesta in Gapway Swamp, NC, a case study was developed to provide guidance for ongoing management efforts. In total, three field trials evaluated registered aquatic and experimental herbicides using a 140 L ha−1 carrier volume. Select foliar applications from UAAS were also evaluated. Results at 8 wk after treatment (WAT) indicated the experimental protoporphyrinogen oxidase inhibitor, PPO-699-01 (424 g ai ha−1), in combination with endothall dipotassium salt (2,370 g ae ha−1) provided 78% visual control, whereas control when PPO-699-01 (212 g ai ha−1) was applied alone was lower at 35%. Evaluations also showed diquat (3,136 g ai ha−1) alone, glyphosate (4,539 g ae ha−1) alone, and metsulfuron-methyl (42 g ai ha−1) alone achieved 86% to 94% visual plant control at 8 WAT. Sequential foliar applications of diquat, flumioxazin (210 g ai ha−1), and carfentrazone (67 g ai ha−1) at 6 wk following exposure to in-water fluridone treatments were no longer efficacious by 6 WAT due to plant regrowth. Carfentrazone applications made from a backpack sprayer displayed greater control than applications made with UAAS deploying identical carrier volumes at 2 WAT; however, neither application method provided effective control at 8 WAT. Additional field validation is needed to further guide management direction of S. molesta control using low carrier volume foliar applications.

Physical and biogeochemical drivers of solute mobilization and flux through the critical zone after wildfire

A nine-year time series of nutrient cation and anion concentration and efflux from three forested catchments in the Jemez River Basin Critical Zone Observatory (JRB-CZO) in northern New Mexico was used to quantify the pulse of chemical denudation resulting from varying levels stand-replacing wildfire intensity in May-June of 2013. The 3 years of pre-fire and 6 years of postfire data were also probed to shed light on the mechanisms underlying the pulsed release and the subsequent recovery. The initial large solute pulse released to the streams—K+, Ca2+, Mg2+, SO42-, Cl−, dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), and total dissolved nitrogen (TDN)—was caused by leaching of hillslope ash deposits during the first monsoon storms post-fire. Debris flow following the wildfire likely redistributed much of the ash-containing sediments along streams and valley bottoms. Sustained elevated solute concentrations observed in the surface waters throughout the post-fire period relative to pre-fire baselines is consistent with these soluble materials being periodically flushed from the soils during wet seasons, i.e., snowmelt and summer monsoons. As microbial mediated reactions and biotic uptake—due to plant regrowth—recover after fire, nutrient ion export (e.g., NO3-, Cl− and SO42-) steadily decreased toward the end of the post fire period, but remained above pre-fire levels, particularly for NO3- and SO42-. Surface water concentrations of polyvalent cations (e.g., Al and Fe) decreased significantly after the fire. Our observations suggest that changes in organic matter composition after fire (e.g., increased humification index—HIX) and the presence of pyrogenic carbon may not favor organo-metal complexation and transport. Finally, differences in burn severity among the three watersheds presented in this study, provide insights of the relative impact of solute exports and resilience. The catchments that experienced high burn severity exhibited greater solute fluxes than the less severely burn. Moreover, despite these differences, toward the end of the post-fire period these surface waters presented low and similar solute effluxes, indicating system recovery. Nonetheless, magnitudes and rebounds were solute and process specific. The results of this study highlight the importance of surface and near surface physical and biogeochemical processes on the long-lasting geochemical denudation of forested catchments following wildfires of varying intensities.

Evaluation of fennel cultivars for use in breeding for productivity

Relevance. Common fennel is a perennial herbaceous plant, traditionally used as a one- or two-year-old. The culture is cultivated for the production of essential oil, as a medicinal plant and spice. The introduction of highly productive varieties adapted to cultivation conditions can ensure the necessary production volumes of raw materials for the pharmaceutical, food, paint and perfume and cosmetic industries. The creation of new varieties involves the study of the gene pool and the identification of promising genotypes based on valuable traits.Methods. 37 collection and selection varietals of various ecological and geographical origin were studied. The soil is ordinary medium–sized low-humus medium-loamy chernozem. The productivity of the green mass was taken into account in the phase of technical ripeness for greens (35th days from the beginning of spring regrowth of plants) and processing for oil (the beginning of fruit formation). The area of the plot (depending on the stage of the selection process) is 3–10 sq. m. The repetition is 1–4 times. The method of sowing is wide-row. Humidity and temperature conditions were very different during the years of research, which made it possible to give the studied material a comprehensive assessment.Results. In the conditions of the zone of unstable humidification of the Stavropol Territory, the greatest variation among the studied cultivars was revealed by the length of the growing season, height, productive longevity, leafiness of plants, yield of green mass and seeds. 8 cultivars distinguished by a complex of signs and properties were included in the selection study. Using the biotype selection method from the resulting hybrid combination with a subsequent series of improving selections, a new variety of fennel ordinary Bachata was created, introduced since 2015. to the State Register of Breeding Achievements of the Russian Federation.

Chemical management of aquatic macrophytes under simulated floodplain condition in mesocosms

Floating natives (Eichhornia crassipes and Pistia stratiotes) and emergent exotic invasives (Hedychium coronarium and Urochloa arrecta) macrophytes grow as aquatic weeds in both natural and artificial floodplain areas in Brazil, where the chemical control should be researched. The herbicides glyphosate and saflufenacil, alone or mixed, were tested for weed control under simulated floodplain condition in mesocosms. Glyphosate (1,440 g ha−1), saflufenacil (120 g ha−1), or glyphosate (1,440 g ha−1) + saflufenacil (42, 84, and 168 g ha−1) were applied firstly; and 75 days after treatment (DAT), glyphosate (1,680 g ha−1) was applied as a follow-up treatment to control plant regrowth. An herbicide-free check was also used. Echhinornia crassipes was the species most susceptible to the different herbicides. Saflufenacil alone presented the lowest control on the macrophytes (≤45%) from 7 to 75 DAT, and in most cases they presented high regrowth rates, i.e., this herbicide was the least effective treatment in reducing the dry mass production of the macrophyte community. Glyphosate alone presented low efficacy to control H. coronarium (30–65%), but for the other macrophytes, it presented control peaks ≥90%, maintaining control levels ≥50% until 75 DAT. Glyphosate + saflufenacil, regardless rate of saflufenacil, caused similar damage to glyphosate in E. crassipes and P. stratiotes; however, in U. arrecta it caused 20–30% less injury. In contrast, these treatments provided the best control of H. coronarium. The complementary application of glyphosate was essential to improve the level of control of the first application, after plant regrowth.