Effects Of Defoliation Research Articles

Simulation of Defoliation Effects on Relay Strip Intercropping Soybean: Elucidating Foliar Shedding and Leaf-to-Nodule Growth Plasticity.

Extensive foliar shedding in monoculture soybeans post-anthesis negatively impacts yield, whereas relay strip intercropping prolongs leaf area duration, enhancing productivity. However, little is known about the causes of leaf shedding in monoculture and its impact on physiological functions and plasticity of source and sink organs, we conducted a 4-year field experiment and leaf-removal simulations in relay intercropped soybeans. Results revealed that monoculture soybeans experienced severe self-shading and defoliation, while relay intercropping maintained better light conditions, supporting higher leaf area, nodule numbers, and carbon allocation. Increasing leaf removal initially increased leaf area but eventually reduced it. Extensive leaf-removal reduced Rubisco and sucrose phosphate synthase (SPS) activity, as well as sucrose, malate, ATP, and energy charge (EC) in nodules, revealing a trade-off between leaf growth and nodule development. Moderate leaf-removal (L30), however, balanced compensation and consumption, increasing total non-structural carbohydrates (TNC) in roots and N and ureide in leaves and pods. Network analysis showed that L30 improved the synergies of functional traits in leaves and nodules, ultimately benefiting overall plant growth and nutrient accumulation in pods. This study elucidates a mechanism of foliar shedding and highlights how relay strip intercropping optimizes source-sink coordination to enhance photosynthesis and nitrogen fixation.

Effects of defoliation on the development of clonal seedlings of Tectona grandis L.f

Objetivo: O objetivo deste estudo é investigar analisar as consequências das desfolhas artificiais, de 0%, 25%, 50%, 75% e 100% na estratégia de desenvolvimento em mudas clonais de Tectona grandis. Referencial Teórico: A produção de teca vem aumentando no Brasil em paralelo aos estudos para a seleção de melhores materiais genéticos em experimentos de campo, porém se forem considerados o seu comportamento após danos causados em situações reais de campo, possibilitará uma melhor seleção e produtividade do plantio. Método: Os testes foram realizados em sete clones, utilizando-se mudas com dois meses de plantio em vasos de 10 L, avaliados até 75 dias após as desfolhas. Para a análise de danos foram coletados dados da altura (cm), do diâmetro do coleto (mm), mensalmente, e da matéria seca (g) ao final do experimento. Posteriormente, foram avaliadas as consequências na qualidade das mudas através da razão da massa seca da parte aérea e massa seca da parte radicular e a estabilidade do comportamento genético entre os testes de desfolha. Resultados e Discussão: Os materiais genéticos tiveram resultados distintos, desde perda até estímulo no desenvolvimento das partes da planta. A análise da parte aérea da planta é insuficiente para identificar as consequências da desfolha. Os clones que apresentaram maior estabilidade comportamental genética, obtiveram resultados mais significativos estatisticamente em relação à testemunha. Implicações da Pesquisa: As mudas que foram submetidas ao maior percentual de desfolha não foram obrigatoriamente as que sofreram maior perda de incremento. Originalidade/Valor: Este estudo contribui para a literatura por apresentar as qualidades e instabilidades dos clones replicados de matrizes de Tectona grandis. A relevância e o valor desta pesquisa são evidenciados pelos resultados serem distintos nos materiais genéticos da mesma espécie quando induzidos a um estresse.

Herbivory can reduce perennial grass seedling survival, but temperature and cumulative precipitation are more important predictors in the first growing season

Successful establishment of desired species during restoration is challenging in drylands. Much research has focused on the importance of the critical life stages such as germination and emergence, but factors influencing survival through the seedling stages of perennial grasses may be equally important. We asked whether seedling defoliation by insects and/or mammals could cause restoration failure. We quantified the degree of defoliation on seedlings of common perennial grass species at 46 restoration sites throughout Oregon, Idaho, and Nevada, and calculated survival probabilities during the first growing season after planting. At each site, we excluded small mammals and insects for 6 weeks and compared defoliation and survival probabilities with seedlings in controls without exclusions. Seedlings were classified as either: large perennial grasses (LPG), primarily from the Triticeae tribe, or Bluegrasses (Poa spp.). Defoliation of LPG reduced seedling survival, but the effect was small compared to the influence of meteorological variables, such as precipitation and temperature. Based on bite patterns, most defoliation resulted from insects. Only a small percentage of vegetation was removed (36% of individuals were defoliated, mean = 13.2% vegetation removal). Defoliation of bluegrasses was less common than that of LPG seedlings, with only 16% experiencing defoliation, primarily from insects (mean = 4.3% vegetation removal). Some defoliation did occur within the exclusion treatments, but the effect of defoliation on seedling survival did not appear to interact with treatment. Based on the results of this study, seedling herbivory is unlikely to be a major factor in restoration failure in the Northern Great Basin.

The effect of pinching and leaf defoliation on plant root architecture and bulb characteristics in lilium

In plants, leaves are the most important organs together with roots in terms of plant development. The effects of leaf defoliation and pinching on root architecture and bulb development were determined in lilies 'Vong' cultivar. For this purpose, leaf defoliation was determined as 0, 25%, 50%, 100%, and pinching was performed. Root length (cm), root surface area (cm2), root volume (cm3), root diameter (mm), number of tips, number of forks, and number of crossings in root architecture were measured. The effect of bulb properties was also determined in main bulb diameter (mm), bulb fresh weight (g), bulb dry weight (g), and bulbil diameter (mm). Leaf defoliation was found to affect root growth negatively. As the defoliation rate increased, the root architectural features decreased compared to the control. In contrast to leaf defoliation, the pinching application significantly increased root length (7568 cm), root surface area (9254 cm2), root volume (176 cm3), number of tips (8553), number of forks (40106), and number of crossings (7950). However, it had no effect on root diameter in two applications. In addition, while leaf defoliation decreased bulb characteristics, pinching application significantly increased bulb fresh weight (54.24 g), bulb dry weight (4.43 g), and bulb diameter (19.43 mm). It was also determined that the application that reduced the bulb fresh weight, bulb dry weight and bulb diameter the most was 100% leaf defoliation. As a result, it was found that pinching is the best method to ensure healthy root growth and bulb development, suggesting that it can be recommended for growing lilium bulbs.

The systemic herbicide glyphosate affects the sporulation dynamics of Rhizophagus species more severely than mechanical defoliation or the contact herbicide diquat.

Arbuscular mycorrhizal fungi (AMF) are totally dependent on a suitable host plant for their carbon resources. Here, we investigated under in vitro conditions, the impact of defoliation practices, i.e., mechanical defoliation or chemical defoliation with a contact herbicide (Reglone®, containing the active ingredient diquat) or systemic herbicide (RoundUp®, containing the active ingredient glyphosate),on the dynamics of spore production of Rhizophagus irregularis and Rhizophagus intraradices associated with Solanum tuberosum and/or Medicago truncatula. Glyphosate affected the spore production rate more rapidly and severely than diquat or mechanical defoliation. We hypothesize that this effect was related to disruption of the C metabolism in the whole plant combined with a possible direct effect of glyphosate on the fungus within the roots and/or perhaps in soil via the release of this active ingredient from decaying roots. No glyphosate could be detected in the roots due to technical constraints, while its release from the roots in the medium corresponded to 0.11% of the active ingredient applied to the leaves. The three defoliation practices strongly affected root colonization, compared to the non-defoliated plants. However, the amount of glyphosate released into the medium did not affect spore germination and germ tube growth. These results suggest that the effects of defoliation on the dynamics of spore production are mainly indirect via an impact on the plant, and that the effect is faster and more marked with the glyphosate-formulation, possibly via a direct effect on the fungus in the roots and more unlikely on spore germination.

Effects of Pneumatic Defoliation on Fruit Quality and Skin Coloration in ‘Fuji’ Apples

Effects of Pneumatic Defoliation on Fruit Quality and Skin Coloration in ‘Fuji’ Apples

Effects of mechanical defoliation and pinching applications on plant growth and root system analysis with machine learning in boxwoods

The effects of mechanical defoliation and pinching (1 cm tip cutting) on Buxus plant growth, nutrient mobilization, and root architecture were determined. When 100% defoliation was applied, the highest increase rates of 80.3% in shoots and 88% in leaves were observed compared to the control group. In contrast, the overall effects of defoliation and pinching were negative, with 100% defoliation having the most negative effects. The chlorophyll content of the newly formed young leaves was also 50% lower with 100% defoliation. Leaves and root nutrient mobilization changed significantly, depending on the effects of defoliation and pinching. Apart from a very small increase in root length and number of forks, the effects of the treatments were negative, with 100% defoliation having the greatest negative effect on root development. Most affected was the number of crossings, which was 78% lower than in the control. In addition, machine learning (ML) algorithms were used in the study, including multilayer perceptron, J48, PART, and logistic regression. The input variables were evaluated to model and predict the root features. The performance values of the ML algorithms were noted in the following order: Logistic Regression> PART> J48> MultilayerPerceptron. As the severity of defoliation increased, the losses of the plant also increased. However, boxwood has mechanisms to compensate for these losses even when it suffers complete defoliation.

Response of stream habitat and microbiomes to spruce budworm defoliation: New considerations for outbreak management.

Defoliation by eastern spruce budworm is one of the most important natural disturbances in Canadian boreal and hemi-boreal forests with annual area affected surpassing that of fire and harvest combined, and its impacts are projected to increase in frequency, severity, and range under future climate scenarios. Deciding on an active management strategy to control outbreaks and minimize broader economic, ecological, and social impacts is becoming increasingly important. These strategies differ in the degree to which defoliation is suppressed, but little is known about the downstream consequences of defoliation and, thus, the implications of management. Given the disproportionate role of headwater streams and their microbiomes on net riverine productivity across forested landscapes, we investigated the effects of defoliation by spruce budworm on headwater stream habitat and microbiome structure and function to inform management decisions. We experimentally manipulated a gradient of defoliation among 12 watersheds during a spruce budworm outbreak in the Gaspésie Peninsula, Québec, Canada. From May through October of 2019-2021, stream habitat (flow rates, dissolved organic matter [DOM], water chemistry, and nutrients), algal biomass, and water temperatures were assessed. Bacterial and fungal biofilm communities were examined by incubating six leaf packs for five weeks (mid-August to late September) in one stream reach per watershed. Microbiome community structure was determined using metabarcoding of 16S and ITS rRNA genes, and community functions were examined using extracellular enzyme assays, leaf litter decomposition rates, and taxonomic functional assignments. We found that cumulative defoliation was correlated with increased streamflow rates and temperatures, and more aromatic DOM (measured as specific ultraviolet absorbance at 254 nm), but was not correlated to nutrient concentrations. Cumulative defoliation was also associated with altered microbial community composition, an increase in carbohydrate biosynthesis, and a reduction in aromatic compound degradation, suggesting that microbes are shifting to the preferential use of simple carbohydrates rather than more complex aromatic compounds. These results demonstrate that high levels of defoliation can affect headwater stream microbiomes to the point of altering stream ecosystem productivity and carbon cycling potential, highlighting the importance of incorporating broader ecological processes into spruce budworm management decisions.

Simulated fire injury: effects of trunk girdling and partial defoliation on reproductive development of apple trees (Malus domestica)

Fire damage can significantly impact fruit productivity in orchards. However, the effects of nonlethal fire injuries on the reproductive development of apple trees remain poorly understood. To investigate these effects, we implemented three treatments: trunk girdling to simulate fire injury to xylem, defoliation of a third of the canopy (simulated crown fire injury), and a combined treatment (simulated surface fire injury), alongside a control. The experiment was conducted during the 2021–22 growing season using a randomised block design with four biological replicate plots. Girdling was less effective than crown and surface fire treatments in influencing fruit composition during the current growing season, and flowering and fruiting in the following season. The crown and surface fire treatments induced localised detrimental effects on fruit sugar and titratable acidity while stimulating peel blush. Additionally, these treatments led to reduced starch reserves by harvest, which likely disrupted subsequent flowering and crop load near the previously defoliated sections of the canopy. When surface fires damage leaves near the base of the canopy in addition to the trunk, fruit production in the lower part of the canopy is more likely to be compromised in the following season. Crown fires, which cause leaf loss near the apex of the canopy, appear to be particularly detrimental to tree productivity, as the top defoliation treatment impaired carbohydrate reserves in shoot terminals and roots. In conclusion, fire-induced loss of leaf area during fruit growth alters fruit composition in the current growing season and may lead to lower yields in the subsequent season.

Reduced seed viability in exchange for transgenerational plant protection: Does the defensive mutualism concept pass the fitness test?

Epichloë endophytes are vertically transmitted via grass seeds and chemically defend their hosts against herbivory. Endophyte-conferred plant defence via alkaloid biosynthesis may occur independently of costs for host plant growth. However, fitness consequences of endophyte-conferred defence and transgenerational effects on herbivore resistance of progeny plants, are rarely studied. The aim of this study was to test whether severe defoliation in mother plants affects their seed production, seed germination rate, and the endophyte-conferred resistance of progeny plants. In a field study, we tested the effects of defoliation and endophyte symbiosis (Epichloë uncinata) on host plant (Festuca pratensis) performance, loline alkaloid concentrations in leaves and seeds, seed biomass and seed germination rates. In a subsequent greenhouse study, we challenged the progeny of the plants from the field study to aphid herbivory and tested whether defoliation of mother plants affects endophyte-conferred resistance against aphids in progeny plants. Defoliation of the mother plants resulted in a reduction of alkaloid concentrations in leaves and elevated the alkaloid concentrations in seeds when compared with non-defoliated endophyte-symbiotic plants. Viability and germination rate of seeds of defoliated endophyte-symbiotic plants were significantly lower compared to those of non-defoliated endophyte-symbiotic plants and endophyte-free (defoliated and non-defoliated) plants. During six weeks growth, seedlings of defoliated endophyte-symbiotic mother plants had elevated alkaloid concentrations, which negatively correlated with aphid performance. Endophyte-conferred investment in higher alkaloid levels in seeds -elicited by defoliation- provided herbivore protection in progenies during the first weeks of plant establishment. Better protection of seeds via high alkaloid concentrations negatively correlated with seed germination indicating trade-off between protection and viability.

Nitrogen sources and defoliation levels in cowpea bean

This study was aimed at evaluating the effect of artificial defoliation and different nitrogen sources on production traits of cowpea using mixed generalized linear models. The experiment was developed in a 3x5x2 factorial arrangement, being: three Nitrogen sources; five levels of artificial defoliation; and two defoliation seasons, with four repetitions. The plots were distributed in the Randomized Block Design, developed in a greenhouse and in the field. The following characteristics were evaluated: number of pods produced per plant; number of grains produced per pod; number of grains produced per plant; average length of pods; average weight of 100 grains; and estimated production. The GLIMMIX procedure was used because it allows the probability distribution of the response variable to take the appropriate distribution model. Production per Hectare (PHA) of plants subjected to leaf loss area can be increased up to 50% defoliation level, the variety Tumucumaque overcompensates in productivity, with maximum yields at 27.03% of defoliation and significant decrease above 75%, regardless of phenological stage. Even with losses above these levels, this cultivar had high indexes of productivity, revealing its high resistance to leaf loss injury. The use of chemical nitrogen fertilization and inoculation of cowpea seeds, variety Tumucumaque with Bradyrhizobium is unnecessary in the edaphoclimatic conditions of Bom Jesus – PI; The use of nitrogen fertilization with ammonium sulfate and inoculation of cowpea seeds with Bradyrhizobium does not influence the resistance of the Tumucumaque variety to defoliation levels; Defoliation levels above 75% impair the performance of production traits of cowpea, Tumucumaque.

Forage legume responses to climate change factors

AbstractIncorporating forage legumes into grasslands is a recommended climate change mitigation strategy, but accruing desired benefits from legumes is contingent upon their resilience when exposed to climate change factors (CCF). Our objective was to synthesize literature describing responses to CCF of a broad array of forage legume species, including annuals and perennials from both temperate and tropical/subtropical regions. Most‐represented species in the related literature include alfalfa (Medicago sativa L.), various Trifolium and Lotus species, rhizoma peanut (Arachis glabrata Benth.), and capitata stylo (Stylosanthes capitata Vogel). The data indicate that while CCF effects on forage legumes can be generalized, interactions among CCF, species, and site‐specific soil/climate conditions may cause variation from expected responses. In most instances, exposing forage legumes to CO2 enrichment (eCO2) increased forage accumulation (FA), but elevated temperature (eT) often reduced the magnitude of the positive response to eCO2. Photosynthetic acclimation to eCO2 occurs in non‐N‐fixing plants, but legume nodules are large C sinks and drive sustained increases in legume FA to eCO2. Legume N2 fixation and the proportion of legume N derived from N2 fixation increase with eCO2, but the magnitude of the increases lessens with eT. Legume nutritive value (NV) responses to eCO2 are less pronounced than FA responses, but decreased herbage N and greater nonstructural carbohydrate concentrations are common. Exposure to eT negatively affects NV unless intervals between defoliation events are shortened. Limited data on reproductive performance show CCF affect flower number, pollen grain morphology and viability, and behavior of pollinators, potentially influencing legume reproductive success.

Ungulate herbivores promote beta diversity and drive stochastic plant community assembly by selective defoliation and trampling: From a four‐year simulation experiment

Abstract Ungulate herbivores shape grassland plant communities at multiple scales, ultimately affecting ecosystem function. However, ungulates have complex effects on grasslands, including defoliation, trampling, excreta return and their interactions. Moreover, the effects of ungulate density on grasslands are regulated by these three mechanisms. Nevertheless, how these three mechanisms affect biodiversity at multiple scales and community assembly remains poorly understood. Here, we conducted a 4‐year novel field experiment to disentangle the effects of defoliation, trampling, and excreta return by ungulates on plant community assembly in a temperate grassland in Inner Mongolia, China. This experiment set two different scenarios: moderate ungulate density (Moderate, characterised by selective defoliation and moderate trampling) and high ungulate density (Intense, characterised by non‐selective defoliation and heavy trampling), including different combinations of defoliation, trampling and excreta return in each scenario. We found that defoliation and trampling increased stochasticity in community assembly and promoted alpha and beta diversity under both scenarios. Specifically, defoliation promoted the coexistence of species with multiple resource acquisition strategies (higher functional trait diversity) by reducing interspecific competition; trampling tended to facilitate random species colonisation. Conversely, excreta return favoured grasses, promoting deterministic assembly and impacting species coexistence. Notably, selective defoliation in the Moderate scenario led to a dominance of stochastic processes during community assembly, whereas non‐selective defoliation still did not change the dominance of deterministic processes. Further, communities subject to selective defoliation were insensitive to changes in soil properties caused by trampling and excreta return, maintaining a high‐level beta diversity and the stochastic of community assembly. Synthesis: Our study provides important insights into the mechanisms by which ungulate herbivores influence plant community assembly, suggesting that defoliation and trampling have the potential to drive stochastic processes, while excreta return plays the opposite role. Our study also suggests that selective foraging by ungulates acts as stronger stochastic forces during community assembly compared to non‐selective defoliation. These results imply that considering ungulate feeding preferences and foraging behaviour in grassland management will help prevent biodiversity loss and biotic homogenisation.

Effects of defoliation on root traits, nitrogen fixation, soil nitrogen availability, soil enzyme activities and soil bacterial communities of forage legumes

Effects of defoliation on root traits, nitrogen fixation, soil nitrogen availability, soil enzyme activities and soil bacterial communities of forage legumes

Effects of needle cast diseases on the growth of a 33-year-old Douglas-fir provenance plantation in northwestern Bulgaria

Abstract In this study, the effects of defoliation caused by fungal pathogens on the tree vitality and growth of a 33-year old Douglas-fir (Pseudotsuga menziesii) provenance plantation in northwestern Bulgaria was presented. The results of the conducted surveys in 2011 and 2020 showed that there were significant differences between the individual provenances of Douglas-fir concerning their susceptibility to the needle cast diseases, caused by the fungal pathogens Rhabdocline pseudotsugae and Phaeucryptopus gaeumannii. The extent of damage, expressed as the amount of Douglas-fir needles cast, varied among provenance groups in individual years. A serious degree of defoliation was assessed among all continental provenances. In 2011, all examined trees from the group of continental provenances had severe symptoms of the needle cast disease. In 71.5% of them, the defoliation of the crowns was over 25% – moderately to severely affected. The average degree of defoliation varied from 18.3% (32 Wаrm Springs) to 89.3% (55 Alamogordo). In 2020, severe defoliation was found among all continental provenances. Both fungal pathogens were found as causes of the defoliation of 64.3% of the trees. The growth indicators: average height, average diameter at breast height, average height- and diameter increment for survived provenances in 2011 (at age 24) and 2020 (at age 33) were evaluated. The loss of needles and the reduced physiological function of the trees affected their vitality in the following years. Relationships between the average current annual height and diameter increment by provenance groups for 2003–2011 and 2011–2020 were calculated. It was found that with an increase in the degree of defoliation, the height and diameter increment of the provenances decreases.

Mesocarnivore sensitivity to natural and anthropogenic disturbance leads to declines in occurrence and concern for species persistence.

Understanding mesocarnivore responses to both natural and anthropogenic disturbance is crucial for understanding species' potential to maintain landscape persistence into the future. We examined the response of five mesocarnivore species (bobcat, coyote, fisher, gray fox, and red fox) to both types of disturbances and climatic conditions. The Northeastern U.S. has experienced multiple large-scale disturbances, such as a mass defoliation event following larval spongy moth outbreak and high densities of infrastructure that divide the natural landcover into roadless zones where these species inhabit. Using dynamic occupancy models in a Bayesian framework, we aimed to (1) examine variation in species' responses over a 4-year study by estimating variation in site-level occupancy, colonization and extirpation of each species in the state of Rhode Island relative to natural disturbance (i.e., defoliation event), anthropogenic disturbance (i.e., parceling of natural landcover bounded by roads, distance to roads), and climate (i.e., seasonal precipitation) and (2) compare current occurrence trends to predicted asymptotic occupancy to identify key variables contributing to distribution instability. Our findings indicated declines in the occurrence of both fox species, and fisher. There was variation in mesocarnivore response to disturbance among the species. We found gray fox and fisher occupancy dynamics to be sensitive to all forms of disturbance and coyote occurrence was positively associated with anthropogenic disturbance. Although bobcat and red fox were predicted to respond positively to future climate scenarios, fisher and gray fox were not, and persistence of fisher and gray fox in a landscape of disturbance relies on large areas with high forest and shrubland cover. With the wide-spread spongy moth outbreak across much of southern New England, our findings indicate that efforts to conserve forested lands may be crucial in maintaining the persistence of several mesocarnivore species in this region experiencing large-scale disturbance.

Defoliation level and timing affect popcorn yield traits in the Midwestern United States

Popcorn [Zea mays (L.) var. Everta] is an important field crop in the Midwestern United States. However, hailstorms are a major threat to ensuring high yield because of their effects on leaf photosynthesis, pollination, and stalk lodging. A multi-state study spanning six site-years (2020–2023) was conducted in two locations (Ohio and Nebraska) to determine how defoliation intensity at different stages affects yield loss in popcorn and compare these losses with current values in the National Crop Insurance Service (NCIS) Corn Loss Instructions. At each location the study was conducted in a randomized complete block design with four replicates. The treatments consisted of the combination of four levels of leaf loss (25, 50, 75 and 100 % leaf blade area removal) imposed at five developmental stages: V8 (10-leaf), V13 (15-leaf), VT, R2, and R4. The evaluated traits were plant population, grain yield, stalk lodging, and 100-kernel weight. All evaluated traits were affected by defoliation, except plant population. The treatments 100 % defoliation at VT and R2 stages were the most damaging in terms of grain yield reduction, number of ears per plant and 100-kernel weight for both locations. In Ohio, the greatest stalk lodging was observed at 100 %-R2 and in Nebraska, at 75 %-VT. For both locations, the actual yield losses in the defoliated treatments were lower than values currently listed in the NCIS Popcorn Leaf Loss Chart. These results indicate leaf loss chart values should be updated to accurately reflect yield losses from popcorn defoliation events. This evaluation did not impose damage to stalks (e.g., bruising) or to plant whorls as may be expected in natural events. Future research should incorporate other forms of plant damage such as those described to provide a better emulation of hail damage.

Effect of Defoliation on Growth, Yield and Forage Quality in Maize, as a Simulation of the Impact of Fall Armyworm (Spodoptera frugiperda)

This study assesses the impact of defoliation applied to three developmental stages across three cropping seasons from 2021 to 2023 on growth, yield and forage quality in maize. The experimental design included three treatments: defoliation of three expanded leaves at the 3rd–4th leaf stage (DF1), the 5th–6th expanded leaves by leaf punch (DF2) and expanding leaves with the DF2 treatment (DF3) at the 6th–7th leaf stages, compared with no defoliation (control). Over three years, the most significant decrease in dry matter (DM) yield occurred in DF1 during spring sowing, while in summer sowing, the largest reduction was in DF3, both of which were correlated with changes in the number of grains per ear. The DM yields at harvest were positively correlated with plant leaf areas at the silking stage. The digestibility of forage in in vitro DM decreased concomitantly with an increase in acid detergent fiber content, indicating a decrease in forage quality. Given the frequent severe damage observed in summer sown maize and the detrimental effects of early growth stage leaf feeding on quality and quantity of spring sown maize, the application of registered insecticides is advised to reduce pest damage to maize crops.

Defoliation decreases soil aggregate stability by reducing plant carbon inputs and changing soil microbial communities

Soil aggregation and its stability are fundamental in ensuring soil function and ecosystem service provision, which can be greatly altered by ungulate disturbance, particularly the indirect effects from biomass removal by defoliation and direct effects from hoof trampling, but the mechanisms underlying the effect of defoliation and trampling on soil aggregation remains largely unexplored. Here, we conducted a 3-year manipulative experiment to investigate the effects of defoliation and trampling of ungulates and their interaction on soil aggregate stability in a semiarid grassland of Inner Mongolia, China. We found that defoliation rather than trampling dominantly affected soil aggregate stability. Defoliation disintegrated macroaggregates, reducing aggregate stability (-5 %), mainly attributed to the direct influence of a decline in plant inputs (aboveground biomass: −32 %) and the indirect effects of soil microbial biomass (-5 %). Moreover, compared to no defoliation plots, defoliation significantly decreased soil fungal diversity and altered fungal communities, particularly decreasing the relative abundance of Glomeraceae fungal taxa favorable to the formation of soil aggregates. Trampling only slightly attenuates the involvement of microorganisms (indirectly, −7 %) in aggregate formation by increasing soil compaction (directly, −4 %), and the positive effects from accelerating litter-derived C inputs due to trampling disturbance may counteract these limited negative effects. Our results highlight the negative effect of biomass removal by ungulates on soil aggregation, and suggest that the role of plant inputs and soil microbial properties on soil function and their correlation with soil aggregate stability needs to be explored under a diversity of grazing management strategies to refine management to improve soil conservation, C persistence and restore grasslands.

Effects of spruce budworm defoliation on in-stream algal production and carbon use by food webs

Insect defoliation is a widespread cause of forest disturbance in Canada, and it has the potential to alter terrestrial carbon contributions to stream consumers and thus affect stream ecosystems. Although defoliation by spruce budworms ( Choristoneura fumiferana) is considered a natural disturbance with importance to forest succession, the magnitude and duration of outbreaks are increasing, and there is a growing need to understand their downstream consequences. To examine this, algal productivity and autochthonous (in-stream) energy supporting macroinvertebrate and fish consumers (using δ13C, δ15N) were examined in 12 streams in the Gaspé Peninsula, Québec, Canada, that ranged in watershed defoliation from spruce budworm. Hierarchical partitioning models were used to assess the contributions of watershed and stream variables to these endpoints. Total seasonal algal production ranged fourfold among sites, and cumulative defoliation was the strongest predictor. Consumers from streams with greater defoliation (cumulative or annual) had lower reliance on autochthonous carbon, despite increased algal production, and this effect was greater for brook trout than macroinvertebrates. These findings demonstrate for the first time that insect outbreaks—which alter forest structure and function—also similarly affect downstream aquatic ecosystems by causing changes in the production and contributions of carbon sources. This suggests that insect control strategies and forest management decisions should also consider implications for downstream aquatic ecosystems.