Girdled Trees Research Articles

Effect of branch girdling on berry traits, chemical and sensory characteristics of ‘Italia’ and ‘Victoria’ table grapes

ABSTRACT Girdling is an ancient agronomic technique that causes a change in the distribution of photosynthates, mineral nutrients and plant hormones. The aim of this study was to assess the effect of girdling technique on ‘Italia’ and ‘Victoria’ table grape cultivars. In this study, the carpological, physico-chemical and sensory data were evaluated. In order to assess the effect of girdling on grape volatile compounds, a headspace solid-phase microextraction was also performed. Results showed the effects of girdling on morphological, physico-chemical and sensory characteristics of table grapes with a different change of berry size and colour depending on the cultivar. The girdling treatment produced a significant decrease of sugar content and total soluble solids/titratable acidity ratio only for ‘Italia’ cultivar. The analysis of volatile compounds revealed that ‘Italia’ cultivar had three more compounds than ‘Victoria’ and that the samples taken from the girdled grapevines had fewer compounds than their ungirdled ones. The results exhibited that the girdling treatment was more effective on the ‘Italia’ cultivar. This study showed that girdling efficacy strongly depends on the cultivar. The samples from the girdled grapevines had fewer volatile compounds than the ungirdled ones. The Principal Component Analysis totally differentiated both cultivar and treatment without overlap.

Influences of girdling and potassium treatments on fruit quality and some physiological characters of ‘Fremont’ mandarin variety

Abstract Growing citrus involves cultural treatments such as girdling and foliar potassium treatment to increase fruit size, yield and quality. The aim of the study was to evaluate the effects of single and double stem girdling, potassium nitrate (KNO3) treatment on leaves and combinations of these treatments on the fruit yield, size and quality characteristics, leaf chlorophyll concentration and leaf nitrogen content, leaf fluorescence (PSII) and leaf sugar content of the ‘Fremont’ mandarin variety. Girdling treatments were applied on the stem by removing 4 mm wide ring of bark at the end of anthesis and after the June fruit drop. Foliar KNO3 applications were applied at a concentration of 4% twice (90 days and 120 days after full anthesis) in the experiment. The single girdling (SG) and double girdling (DG) treatments on stems increased fruit yield (kg · tree−1) by approximately 40% relative to the control (C). Treatments did not significantly affect the internal fruit quality of the ‘Fremont’ mandarin variety except in fruit colour and appearance. The highest impact on fruit size was found in the DG + KNO3 treatment. According to treatments and periods, the SPAD values varied between 62.08 and 70.67, whereas the PSII values varied between 0.698 and 0.756. The treatments significantly increased the leaf nitrogen (N) concentration and the fructose, glucose and sucrose concentrations relative to the control. The highest N concentration content was detected in the foliar potassium treatment, and the highest total sugar content was detected in the SG treatment.

Spruce girdling decreases abundance of fungivorous soil nematodes in a boreal forest

The relative importance of belowground and aboveground energy inputs for the decomposer communities in soil remains largely unknown. In particular, no research has been done on the significance of root-derived resources for nematode communities in boreal forests. In two spruce stands in the taiga zone, we set up a field experiment in which girdling of spruce trees and clipping of dwarf shrubs was performed. Root-derived resources were hypothesized to be highly important; accordingly, we expected to observe a suppression of the nematode community after experimental manipulations. To obtain information on the nature of changes in the soil food web, nematode community structure indices were applied. In partial confirmation of our hypothesis, spruce girdling decreased mycorrhizal hyphae biomass as assessed via in-growth mesh bags, as well as the abundance of fungivorous nematodes, mostly of the Aphelenchoides and Filenchus genera. The enrichment index (EI) value decreased, indicating reduction of organic matter inputs into the soil food web, whereas nematode channel ratio (NCR) index value increased, indicating a shift towards domination of the bacterial energy channel. Total nematode abundance, genera richness, and abundance of herbivores, omnivores, and predators did not change in response to spruce girdling. Clipping of dwarf shrubs decreased fungal and bacterial PLFA biomarkers, but did not affect nematode communities. Thus, the resources channeled in soil by the roots of canopy trees are of different relative importance for nematodes having different trophic habits. Fungivorous nematodes are at least partly dependent on root-derived resources, suggesting feeding on ectomycorrhizal mycelium. Rhizodeposits of understory vegetation are likely of low importance for nematodes.

Eighth-year survival and growth of planted replacement tree species in black ash (Fraxinus nigra) wetlands threatened by emerald ash borer in Minnesota, USA

Black ash (Fraxinus nigra) is native to lowland forests of the western Great Lakes region, USA, where it often comprises a majority of trees. Like all native ash in North America, black ash is threatened by emerald ash borer (EAB; Agrilus planipennis), but the impacts from EAB mortality may be particularly severe in these forests given the foundational role of black ash at regulating ecosystem function. Compounding the problem is that associated tree species occur in low abundance and their abundance may be further reduced as habitat declines with climate change. These converging threats point to the need for silvicultural intervention to establish replacement tree species in anticipation of EAB invasion. Here we report on a large-scale management experiment from Minnesota, USA that includes different silvicultural approaches for establishing replacement tree species in black ash forests. Specifically, we examined eighth-year survival and growth of planted seedling in treatments that included clearcutting, group selection, uncut forest, and emulation of EAB mortality by girdling black ash. Species included nine that are native to the ecosystem, two from the next southern climate zone, and one exotic species, Manchurian ash (Fraxinus mandshurica). Among species and treatment combinations, survival was highest for American elm (Ulmus americana), averaging around 81% in uncut, group selection, and girdle treatments. Swamp white oak (Quercus bicolor), a species from the next southern climate zone, also had high survival in these treatments (ranging from 61% to 79%). Both species had survival under 60% in the clearcut treatment. Most native southern boreal species, as well as Manchurian ash, had low survival (0% to less than 40%) in most treatments. In the clearcut, girdle, and group selection treatments relative diameter and relative height growth was highest for balsam poplar (Populus balsamifera), averaging, respectively, around 0.25 mm mm−1 yr−1 and 0.20 cm cm−1 yr−1, followed by swamp white oak and red maple (Acer rubrum). Non-native Manchurian ash had consistently low growth in all treatments compared to other species. All species had low growth rates in the uncut treatment. An integration of survival and diameter growth pointed to group selection as the treatment that provides the best balance between survival and growth. Our results indicate promising survival and growth of at least some replacement species, including several predicted to be future climate-adapted, as well as a silvicultural approach in group selection that is an effective method to regenerate these species.

Girdling of young Robinia pseudoacacia trees on the Tama River terrace, central Japan

Robinia pseudoacacia L. has been widely planted worldwide for a variety of purposes, but it is an aggressive invader in many regions. To control invasion by the species, we examined the effectiveness of girdling young trees to ground level to kill trees and preclude sprout development through comparison among girdling, clearcut and control treatments on the Tama river terrace, Tokyo. More than 99% of R. pseudoacacia trees were killed by girdling. The number of sprouts that developed from roots and stumps after girdling was distinctly reduced compared with that observed after clearcutting. We also conducted girdling of young trees of Ailanthus altissima (Mill.) Swingle, which shows similar developmental and ecological characteristics to R. pseudoacacia, and the two species are often sympatric. More than 98% of A. altissima trees were killed, but a higher number of sprouts developed from A. altissima stumps compared with that from R. pseudoacacia stumps. These results indicate that girdling young trees to ground level is an effective method of controlling R. pseudoacacia by killing the stem and precluding sprout development. The girdling method is simple to apply and imposes a low burden on the surrounding environment.

Effect of Girdling on Anthocyanin Content and Quality of Spine Grape Berries

Girdling can promote anthocyanin accumulation in grape berries. However, the underlying mechanism is unclear. In this study, we explored the effects of girdling on the accumulation of anthocyanins and the transcript levels of key genes in anthocyanin synthesis in spine grape skins. We also determined the effect of girdling on the contents of vitamin C, titratable acids, soluble sugars, and aroma compounds, and the transcript levels of genes related to sugar transport and aroma compound synthesis. The girdling treatment promoted anthocyanin accumulation in spine grape skins by increasing the transcript levels of genes related to anthocyanin synthesis. Girdling also increased the transcript levels of genes related to sugar transport in leaves, petioles, and flesh, promoted the transport of photosynthetic products to berries, and increased the soluble sugar content in berries. The transcript levels of genes related to aroma compound synthesis and the contents of aroma compounds in flesh were also increased by the girdling treatment. Together, our results show that a girdling treatment can increase the contents of anthocyanins, soluble sugars, vitamin C, and aroma compounds, decrease the titratable acid content, and significantly improve the quality of spine grape berries.

Vegetative rescue of Cedrela fissilis Vell. by the rooting of cuttings from epicormic and canopy sprouts

ABSTRACT: Cedrela fissilis is a species of great genetic diversity, with low population density and seminal propagation, which causes difficulties in the vegetative propagation process. This research evaluated the vegetative rescue and propagation of stem cutting rooting originated from epicormic and canopy sprouts of C. fissilis. For this, the induction of epicormic sprouts was evaluated 52 days after the complete girdling and semi-girdling 20 and 40 cm from the ground, and no girdling treatment, during spring (2018), summer (2018) and autumn (2019). The variables evaluated were, survival (%), sprouting (%), number, length (cm) and diameter (mm) of sprouts. The cuttings were made from spring epicormic sprouts, divided in two categories: 10 cm cuttings placed vertically in pits and 5 cm cuttings placed horizontally in furrows. The canopy sprouts were collected in the summer, then cut in apical and intermediate cuttings (15 cm). After 60 days, the cuttings were evaluated in survival (%), rooting (%), callus (%), average number and length of roots (cm). Results showed that only the complete girdling produced sprouts (average >67%) with no difference between 20 and 40 cm heights, with a greater number of sprouts during spring. The cuttings from epicormic sprouts, planted vertically in pits presented higher percentage of rooting (44%) than cuttings planted horizontally in furrows (17%). Cuttings from the canopy had inconsiderable rooting (apical - 2%; intermediate - 0%). The girdling periods influences the number of epicormic sprouts and its use for cutting was more efficient in rooting.

Predicting tropical tree mortality with leaf spectroscopy

AbstractDo tropical trees close to death have a distinct change to their leaf spectral signature? Tree mortality rates have been increasing in tropical forests, reducing the global carbon sink. Upcoming hyperspectral satellites could be used to predict regions close to experiencing extensive tree mortality during periods of stress, such as drought. Here we show, for a tropical rainforest in Borneo, how imminent tropical tree mortality impacts leaf physiological traits and reflectance. We measured leaf reflectance (400–2500 nm), light‐saturated photosynthesis (Asat), leaf dark respiration (Rdark), leaf mass area (LMA), and % leaf water across five campaigns in a six‐month period during which there were two causes of tree mortality: a major natural drought and a co‐incident tree stem girdling treatment. We find that prior to mortality, there were significant (p < 0.05) leaf spectral changes in the red (650–700 nm), the NIR (1,000–1,400 nm), and SWIR bands (2,000–2,400 nm) and significant reductions in the potential carbon balance of the leaves (increased Rdark and reduced Asat). We show that the partial least squares regression technique can predict mortality in tropical trees across different species and functional groups with medium precision but low accuracy (r2 of .65 and RMSE/mean of 0.58). However, most tree death in our study was due to girdling, which is not a natural form of death. More research is needed to determine if this spectroscopy technique can be applied to tropical forests in general.

Aboveground Wood Production Is Sustained in the First Growing Season after Phloem-Disrupting Disturbance

Carbon (C) cycling processes are particularly dynamic following disturbance, with initial responses often indicative of longer-term change. In northern Michigan, USA, we initiated the Forest Resilience Threshold Experiment (FoRTE) to identify the processes that sustain or lead to the decline of C cycling rates across multiple levels (0, 45, 65 and 85% targeted gross leaf area index loss) of disturbance severity and, in response, to separate disturbance types preferentially targeting large or small diameter trees. Simulating the effects of boring insects, we stem girdled > 3600 trees below diameter at breast height (DBH), immediately and permanently disrupting the phloem. Weekly DBH measurements of girdled and otherwise healthy trees (n > 700) revealed small but significant increases in daily aboveground wood net primary production (ANPPw) in the 65 and 85% disturbance severity treatments that emerged six weeks after girdling. However, we observed minimal change in end-of-season leaf area index and no significant differences in annual ANPPw among disturbance severities or between disturbance types, suggesting continued C fixation by girdled trees sustained stand-scale wood production in the first growing season after disturbance. We hypothesized higher disturbance severities would favor the growth of early successional species but observed no significant difference between early and middle to late successional species’ contributions to ANPPw across the disturbance severity gradient. We conclude that ANPPw stability immediately following phloem disruption is dependent on the continued, but inevitably temporary, growth of phloem-disrupted trees. Our findings provide insight into the tree-to-ecosystem mechanisms supporting stand-scale wood production stability in the first growing season following a phloem-disrupting disturbance.

Foraging Activity of Woodpeckers on Various forms of Artificially Created Deadwood

Many woodpecker species rely on different forms of deadwood for nesting and foraging. However, the knowledge of the effect of enrichment of their habitat with different types on deadwood of this species group is lacking. Complex conservation-oriented management, including deadwood enrichment, was applied in a 20 ha even-aged oak-dominated woodland in Hungary. The foraging activities of woodpecker species were documented on selected treated trees over one, two and three years since these measures were implemented. The 109 individual oak trees examined represented five deadwood types: damaged-, girdled-, felled trees, and low- and tall stumps. We analysed the relationships between three variables (depth of foraging work, type of deadwood, and year) and foraging activity. Our results illustrated the prompt responses of woodpeckers to the treated trees. The woodpeckers used the five deadwood types in very different ways, and foraging activity was found to vary greatly in terms of depth of foraging and between years. More activity was carried out on both low- and tall stumps than on any other type one year after the treatment, whilst work on girdled trees and tall stumps predominated two and three years after the treatment. The utilisation of felled- and damaged trees by woodpeckers proceeded at a markedly slower pace than that of girdled trees and stumps, but the utilisation increased gradually. Most of the foraging activity was found to be on the outer bark, however, work on the inner bark and in the sapwood increased between the three years. The measures to conserve the woodpecker species should include the permanent creation and maintenance of various forms of deadwood to provide diverse and continuous foraging sites for woodpeckers.

Effects of Light Intensity and Girdling Treatments on the Production of Female Cones in Japanese Larch (Larix kaempferi (Lamb.) Carr.): Implications for the Management of Seed Orchards

To ensure sustainable forestry, it is important to establish an efficient management procedure for improving the seed production capacity of seed orchards. In this study, we evaluated the effects of girdling and increasing light intensity on female cone production in an old L. kaempferi (Lamb.) Carr. seed orchard. We also evaluated whether there is a genotype-specific reproductive response to these factors among clones. The results showed that female cone production was augmented by girdling and increasing light intensity. There was a difference in the effectiveness of girdling treatment levels, and the probability of producing female cones increased markedly at higher girdling levels. At light intensities where the relative photosynthetic photon flux density was higher than 50%, more than half of the trees tended to produce female cones, even in intact (ungirdled) trees, and the genotype-specific response to light intensity was more apparent in less-reproductive clones. These findings suggested that girdling less-reproductive trees combined with increasing light intensity was an effective management strategy for improving cone production in old seed orchards.

Uso de imágenes hiperespectrales para la predicción del marchitamiento de Pinus halepensis (Mill.) en el bosque mediterráneo

<p>The increasing negative effects of climate change and the emergence of invasive species in forests around the world require the development of innovative methods to monitor and quantitatively measure the health status of woodlands. These effects are especially notable in the Mediterranean area, where the decline of stands due to recurrent droughts has increased the damage caused by secondary pests whose populations would otherwise be in balance. Remote sensing technologies allow us to work on large surfaces with reasonable precision. In particular, new spectral indices obtained from high-resolution hyperspectral and thermal images have been shown to be good predictors for the early detection of physiological changes related to diseases. In this pilot study developed in a stand of Pinus halepensis in the Comunitat Valenciana, a controlled simulation of a decay is carried out by means of sequential girdling of trees, making a subsequent field monitoring of the caused decay. Through a hyperspectral camera, the spectral information of each of these trees is analyzed in relation to their discoloration and state of observed decay. The proposed methodology allows the detection of affected trees three months before the appearance of visual symptoms, obtaining a precision higher than 0.9 with Random Forest and Support Vector Machine classifiers. The vegetation indices with better results were PRI, VGO1, VGO2, GM1 and OSAVI. This pilot study allows us to think that some of these indices can be used in the early detection of general pine wilt and, therefore, have application in the monitoring of the main threats to European forests, borer pests or quarantine organisms such as <em>Bursaphelenchus xylophilus.</em></p>

The effect of overwood competition on the long-term survival, growth and stocking of underplanted tree species in logged tropical rainforest in north Queensland, Australia

Enrichment of selectively logged rainforest by planting seedlings of commercially valuable species is often recommended to improve productivity, ecological functioning, and biodiversity. However, the survival and subsequent growth of enrichment plantings depend on how they respond to competition from neighbours. For successful forest restoration or commercial forest management, the challenge is to determine appropriate frequencies and intensities of silvicultural interventions, principally competition reduction. In this study, we use long-term data (49–60 years) from four enrichment planting experiments established after selective logging and girdling of non-commercial trees in a tropical rainforest in north Queensland, Australia, to assess the effects of competition on the survival and growth of enrichment plantings. We found that residual overwood development severely reduced the survival, diameter and volume growth of two widely planted rainforest species - Flindersia brayleyana (Rutaceae) and Agathis robusta (Araucariaceae). Both species responded well to overstory removal, either as an initial treatment or thereafter. Use of Hegyi’s competition index confirmed the strong suppressive effect of neighbours. The most abundant competitor was the fast-growing, early-secondary species Acacia aulacocarpa, which only became apparent after cessation of silvicultural treatments, 7 years after planting. Our results reaffirm the importance of an initial or early-age removal of the competing overstory for the success of enrichment planting. Further silvicultural treatments may be required for extended periods to control excessively increased overwood basal area and to remove late emerging pioneer or early secondary species.

The cambial response of Scots pine trees to girdling and water stress

Abstract We monitored six healthy dominant trees and six girdled Scots pine trees for two successive growing seasons (2014 and 2015) to investigate the seasonal dynamics, cambial activity, and morphology of the new xylem and phloem cells formed under environmental stress when girdling was applied during the dormant period (15 January 2014). Microcore (1.8 mm) samples were collected weekly using a Trephor tool above and below the girdling area, and weather data were measured on site. Drought stress in combination with girdling reduced the total number of differentiation days cell formation. In 2014, no significant differences in tracheid dimensions were observed between the girdled area and the control trees, while in 2015, the control trees showed significantly smaller cell wall thickness and radial dimensions of the latewood tracheids (LW) compared to 2014 and girdled trees had no occurrence of LW. Under stressful heat waves and prolonged periods of no precipitation, the trees tended to reduce the number of tracheids that were formed and exhibited smaller radial dimensions (narrower tree rings) to increase their hydraulic efficiency. Trees responded to limited water availability by forming intra-annual density fluctuations (IADFs L) in the zone of the LW to overcome stressful conditions. Although xylem cell differentiation was affected by stressful conditions, no significant variability in phloem cell dimensions was observed. Thus, the phloem tissue was less sensitive to exogenous factors.

Assessment on the growth performance of planted Dryobalanops beccarii at reforestation sites after implementation of selective girdling

Abstract. Wasli ME, Ambun DB, Kalu M, Sidi M, Nahrawi H, Elias H. 2020. Assessment on the growth performance of planted Dryobalanops beccarii at reforestation sites after implementation of selective girdling. Biodiversitas 21: 1880-1889. This study was conducted to evaluate the growth performance of planted Dryobalanops beccarii Dyer at reforestation sites after silvicultural practices in Gunung Apeng National Park (GANP), Sarawak. The assessed area was planted with D. beccarii in 2005 and undergo silvicultural treatment by understory clearing which implemented annually. Due to the suppressed growth rate of the planted trees, an additional silvicultural treatment, the selective girdling on selected pioneer species, was implemented once, in 2012. In this study, study plots with two treatments were established: T1: understory clearing only (control plot), and T2: additional selective girdling of existing pioneer species in addition to the understory clearing practice applied in T1. The growth performance of the planted D. beccarii in terms of DBH, height, survival and mean annual increments in diameter (MaiD) and height (MaiH) were assessed and monitored at the initial stage when the selective girdling treatment was applied and 4, 24, 36, 48, 60 and 72 months after girdling. Our findings showed that the survival rates of planted trees at 72 months under treatments T1 and T2 were 82.9% and 79.2%, respectively. The average tree DBH in T2 was significantly higher than that in T1, and the average tree DBH values for T1 and T2 were 7.5 cm and 9.4 cm, respectively. The average tree heights for T1 and T2 were 8.3 m and 9.2 m, respectively. In terms of the mean annual increments in height (MaiH) and diameter (MaiD), those in T2 were significantly higher than those in T1. Our findings indicated that T2 started to show better growth performance than T1 after a period of 36 months. In conclusion, the additional silvicultural treatment by selective girdling at the reforestation site had a long-term, progressive effect on the growth performance of the planted trees.

Testing the Effect of Snag and Cavity Supply on Deadwood-Associated Species in a Managed Boreal Forest

Standing deadwood is an important attribute of old-growth boreal forests and it provides essential microhabitats for deadwood-associated species. In managed boreal forests, short rotations tend to limit the amount and diversity of standing deadwood. This study evaluates if the anthropogenic supply of deadwood attributes through tree girdling or by providing nest boxes may favor deadwood-associated species. We studied the short-term response of saproxylic beetles, foraging woodpeckers, and secondary cavity users to snag and cavity supply in 50 to 70-year-old black spruce stands. In spring 2015, we girdled 8000 black spruce according to two spatial distributions (uniform and clustered), and we also installed 450 nest boxes of six different sizes at three distances from the forest edge. Using trunk window traps, we captured significantly more beetles in sites with girdled trees than in control sites in both 2015 and 2016. We also recorded a trend of a greater abundance of beetles in clusters of girdled trees than within uniformly distributed girdled trees. Trypodendron lineatum (Oliver) dominated beetle assemblages, representing 88.5% of all species in 2015 and 74.6% in 2016. The number of beetles captured was 7× higher in 2015 than in 2016. In contrast, we observed greater amounts of woodpecker foraging marks in fall 2016 than in either fall 2015 or spring 2016. Woodpeckers foraged significantly more in clusters of girdled trees than within uniformly distributed girdled trees. Woodpeckers’ foraging mark presence was positively associated with the proportion of recent cuts at 1 km around the study sites. Five Boreal Chickadee (Poecile hudsonicus Forster) pairs used nest boxes and occupied smaller box sizes that were located away from the forest edge. Our study showed that structural enrichment can be effective in rapidly attracting deadwood-associated species within managed forest stands.

Bionomics ofScolytus schevyrewi(Coleoptera: Curculionidae) in Saskatchewan and Manitoba, Canada

AbstractThe invasive alienScolytus schevyrewiSemenov (Coleoptera: Curculionidae: Scolytinae) was detected in Saskatchewan and Manitoba, Canada, in 2007. BecauseS. schevyrewiis a potential vector of the Dutch elm disease pathogen (Ophiostomanovo-ulmiBrasier; Fungi: Ophiostomataceae), the natural history of the beetle was studied from 2009 to 2012 in the two provinces, where the disease is managed to protectUlmus americanaLinnaeus (Ulmaceae). Typically, healthy trees become infected when their xylem is contacted during feeding by spore-bearing scolytine adults that have flown from a diseased tree; adults emerging from brood galleries in diseased trees frequently carry spores. We caught flyingS. schevyrewiadults from May to October; adults were weakly attracted to healthyUlmusLinnaeus but were strongly attracted toUlmus pumilaLinnaeus stressed by girdling.Scolytus schevrewicolonised and completed development in girdled trees and trap logs ofU. pumila. In contrast to other studies,U. americana– the major source of pathogen spores in the area – was never colonised as a brood host. Our results suggest thatS. schevyrewiwill primarily useU. pumila, which, in Manitoba and Saskatchewan, seldom exhibits symptoms of Dutch elm disease. Thus, arrival ofS. schevyrewidoes not appear to require changes to Dutch elm disease management programmes.

Girdling of shoots at flowering reduces shatter in grapevine cv. Malbec

Background and Aims Some grapevine cultivars such as Malbec have unstable yield, due to poor fruitset or fruitlet abscission. The phenomenon is known as ‘shatter’ and this study aims to explore the potential of applying the shoot girdling technique at flowering, to direct the carbohydrate partitioning towards inflorescences and reduce shatter. Methods and Results Fruitful Malbec shoots were girdled above the apical bunch, below the basal bunch, double girdled or not girdled (Control) during 2017 and 2018. Most vegetative growth parameters were unaffected, but shoots widened and the leaf expansion improved in the fruit zone. Fruitset doubled compared to that of the Control, ovary abortion was reduced, and fruit yield increased, mainly due to a greater number of small berries in the base and double girdled treatments. In addition, base girdling increased TSS per berry, reducing the concentration of phenolic substances in the normal size berries. Girdling effects were consistent during both seasons. Conclusions Shoot girdling below the basal bunch proved to be effective in reducing shatter. The increase in carbohydrate supply available to the inflorescences during flowering was able to augment their weak sink strength relative to the perennial organs. Significance of the Study The study contributes to an understanding of the importance of the photoassimilates flow towards inflorescences in reducing shatter and increasing yield in Malbec vines.

Effect of simulated emerald ash borer infestation on nitrogen cycling in black ash (Fraxinus nigra) wetlands in northern Minnesota, USA

Black ash (Fraxinus nigra) wetlands are an important economic, cultural, and ecological resource in the northern Great Lake States, USA, and are threatened by the invasive insect, emerald ash borer (Agrilus planipennis Fairmmaire [EAB]). EAB-induced ash mortality can increase air temperatures, alter understory vegetation communities, and modify wetland hydrology by elevating the water table following canopy dieback, which may, in turn, alter nitrogen cycling in wetland soils and affect plant N uptake, N export to watersheds, and N emissions to the atmosphere. We sampled soils in replicated 1.6-ha plots six years after the following treatments were applied: girdling all ash greater than six cm diameter to simulate EAB-induced mortality, clearcutting with removal of all trees, and an unharvested control. In situ samples were collected from soil cores and from adjacent bulk areas influenced by vegetation to measure the concentration and rates of accumulation of inorganic nitrogen over the 2017 growing season. In the soil cores, the greatest nitrogen accumulation occurred in the unharvested control treatment and nitrate/nitrite were the dominant species of inorganic N. In contrast, in bulk soils, the clearcut treatment had greater overall nitrogen mineralization than both the control and girdle treatments, and ammonium had a greater relative abundance than nitrite/nitrate. Potential N mineralization (assessed with a lab incubation) was not affected by treatment, indicating that treatment effects observed in the field were likely due to changes in the microenvironment. Overall, the effect of simulated EAB on net nitrogen mineralization rates was minimal as mineralization was greatly constrained by ecosystem conditions compared to suitable, laboratory conditions, under which potential N mineralization was an order of magnitude greater than measured in the field. However, canopy treatment influenced water table levels, soil temperature, and vegetation communities, all of which influenced the relative abundance of inorganic N species. Our findings indicate limited indirect effects of EAB on net N mineralization in black ash wetlands.

Effects of girdling and defoliation on the growth of female cones and branches and nutrient content in different tissues and organs of Pinus koraiensis.

To explore the nutrient source and supply-demand relationship of the female cone deve-lopment and new shoot growth of Pinus koraiensis, reproductive mother branches were experimentally girdled, defoliated, and under the combination of both treatments. The effects of different treatments on the female cones development, branch growth and the content of carbohydrate (NSC), nitrogen (N) and phosphorus (P) in different tissues and organs were measured. The results showed that girdling significantly affected female cone development, new shoot growth, and the contents of NSC, N and P in different tissues and organs, while defoliation treatment had limited effect. The NSC content in the mother branch xylem and phloem after girdling were significantly lower than that of the control (CK, ungirdling+0% defoliation), and decreased significantly with the increases of the degree of defoliation. The NSC content in mother branch xylem and phloem of girdling+100% defoliation was 59.0% and 64.8% lower than that of CK, respectively. The deficiency of NSC resulted in the death of mother branches and new shoots and the abortion of female cone. Under girdling treatment, the contents of N and P in xylem and phloem of mother branches of 0%, 50% and 100% defoliation treatment were significantly higher than that of CK. The contents of N and P in xylem of mother branches were 17.3%, 18.2% and 24.3% and 17.9%, 7.1% and 3.6% higher than those of CK, respectively. The contents of N and P in phloem of mother branches was 39.3%, 35.2% and 48.9% and 31.0%, 28.2% and 14.8% higher than those of CK, respectively. The female cone development and new shoot growth of P. koraiensis consumed a large amount of NSC, N and P. The carbohydrates and mineral nutrients manufactured or stored in the mother branches could not meet the needs of female cone development and new shoot growth, and thus they need to be imported from other tissues.