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91 results for “defoliation”
Leaf and Soil Nitrogen Following Lymantria dispar Defoliation in Central Massachusetts 2018-2019
In this study we investigated relationships between ecosystem nitrogen (N) cycling and tree defoliation during a recent 2015-2018 irruption of invasive Lymantria dispar caterpillars, which can cause tree stress and sometimes mortality following multiple years of defoliation. Nitrogen is a critical nutrient that limits the growth of caterpillars and plants in temperate forests. We assessed the associations between N concentrations, soil solution inorganic N availability, and defoliation intensity by L. dispar at the scale of individual trees in the Amherst, MA area and forest plots in the Quabbin Reservoir area.
Lymantria dispar Defoliation and Mortality Survey at the Quabbin Watershed in Central Massachusetts 2017-2022
For most of the 20th century, the invasive Lymantria dispar was the most serious insect threat to forests and shade trees in the northeastern United States, but outbreaks have been sporadic and light since 1989, after the successful establishment of a fungal pathogen, Entomophaga maimaiga. However, in 2016 a surprising new outbreak of Lymantria dispar began in southern New England, resulting in dramatic oak (Quercus spp.) mortality across thousands of forested hectares by 2018. In 2017, during the height of the outbreak, a rapid assessment of defoliation across 486 plots in six clusters (aka ‘hotspots’) across the Quabbin Watershed Forest in central Massachusetts was conducted. These sample points can be related to satellite-based defoliation estimates, and the tree and site data analyzed for predictors of defoliation severity. In 2022, we returned to 204 of these plots to assess oak mortality, understory vegetation, and oak regeneration.
Nonstructural Carbohydrates in Defoliated Oaks in Central Massachusetts 2019-2020
Carbon starvation posits that defoliation- and drought-induced mortality results from drawing down stored nonstructural carbohydrates (NSCs), but evidence is mixed and mortality is often observed prior to full drawdown of NSCs. We tested the relationship between defoliation severity, NSC drawdown, and tree mortality by measuring NSCs in mature oak trees defoliated by Lymantria dispar across a natural experimental gradient of defoliation severity. We collected stem and root samples from oaks (Quercus rubra and Q. alba) in interior forests (n=34) and forest edges (n=47) in central Massachusetts, USA. Total NSC (TNC; sugar + starch) stores were analyzed with respect to tree size, species, and defoliation severity, which ranged between 5 and 100%. Forest edge trees had higher TNC stores that were less sensitive to defoliation than interior forest trees. However, TNC stores declined significantly in both groups with increasingly severe defoliation. Furthermore, we observed a mortality threshold of 1.5% dry weight TNC. Our study draws a direct link between insect defoliation and TNC reserves and defines a TNC threshold below which mortality is highly likely. These findings advance understanding and improve model parametrization of tree response to insect outbreaks, an increasing threat with globalization and climate change.
Oak Forest Response to Lymantria dispar Defoliation in Central Massachusetts since 2019
Invasive forest insects are a major global change driver, and the Northeastern U.S. is an invasion hotspot. Lymantria dispar is one of the region’s most destructive defoliators. After thirty years of quiescence, a surprisingly severe outbreak began in 2015 in southern New England, and by 2018 had caused dramatic oak mortality across thousands of forested acres. Lymantria dispar is considered a generalist, but in New England, oaks (Quercus sp.) are its preferred host trees. Oaks are key overstory trees in eastern North America. In New England, they have been a dominant component of the forest for thousands of years, and play a leading role in providing habitat, timber, and carbon sequestration. However, oak prominence is declining throughout New England. The reasons for oak’s decreasing abundance are the subject of lively debate but the role of L. dispar is likely underappreciated. Therefore, we need to understand the causes and consequences of oak dieback and mortality to this disturbance event, so that we can better predict responses to future outbreaks. To address this need, we established a set of permanent plots in central Massachusetts, chosen to capture a range of defoliation severity.
Black Rock Forest Spring Freeze Defoliation Radial Growth and Leaf-Level Gas Exchange
These data are from a study conducted at Black Rock Forest in Cornwall, New York, USA during 2020 and 2021. This study was conduct to assess the ecophysiological responses of red oak (Quercus rubra) and red maple (Acer rubrum) trees in a temperate broadleaf forests to a spring frost in 2020 that that defoliated red oak trees, but not red maples. We used 2021—a year without a defoliation event—as a reference year. The datasets include tree-level measurements of (1) basal area increment for the early growing season, late growing season, and entire growing season and (2) leaf-level gas exchange (Amax, gsw, and WUE) for red oak (Quercus rubra) and red maple (Acer rubrum). These data are associated with the manuscript “Compensatory Responses of Leaf Physiology Reduce Effects of Spring Frost Defoliation on Temperate Forest Tree Carbon Uptake” by Reinmann et al.2023 in Frontiers in Forests and Global Change.
Bonanza Creek Experimental Forest Defoliating Insect Population Levels Per Leaf 1975-2012 - Werner
Defoliating insect population levels were monitored at Bonanza Creek Experimental Forest, Fairbanks, Alaska, USA from 1976 to 202012. Total number of insects per square meter of foliage is archived in this dataset.
Forest defoliator outbreaks disrupt nutrient cycling in northern waters
<p>Datasets for manuscript Forest defoliator outbreaks alter nutrient cycling in northern waters. IO_df is the main insect outbreak dataframe used to generate the bulk of the figures and results. It contains measures of monthly lake chemistry, insect disturbance, and catchment characteristics. Defoliator_Bark-Wood-Beetle_df is used to generate figure S1 and contains yearly measures of defoliator and bark/wood beetle outbreaks. ndvi_lai_data is used to generate figure S6 and contains the relationship between MOIDS LAI and Landsat NDVI. Outbreak_History is used to generate figure 5 and is a record of catchment-level disturbances in our study region. </p>
Defoliator outbreaks track with warming across the Pacific coastal temperate rainforest of North America
<p>The biogeography of irruptive insect herbivores is determined by host availability and climate conditions. As such, outbreak distributions are sensitive to climatic change, especially across large latitudinal gradients. Here, we investigate the outbreak distributions of two understudied defoliators, hemlock sawfly (Hymenoptera; <em>Neodiprion tsugae</em>) and western blackheaded budworm (Lepidoptera; <em>Acleris gloverana</em>), that have both recently impacted the greatest land area recorded across the Pacific coastal temperate rainforest since the establishment of aerial survey programs. We compiled polygon-based estimates of insect damage collected by aerial observers, forest inventory, and downscaled climatic data to develop gridded estimates of bioclimatic conditions across the extent of the Pacific coastal temperate rainforest, including the continental United States, British Columbia, and Alaska. We leveraged these data to develop ensemble machine learning models with the goal of predicting the outbreak distribution of each insect. In this manuscript we: (1) describe the historical patterns of defoliator outbreaks, (2) identify and describe climatic conditions associated with outbreaks in both species, and (3) assess whether historic outbreaks have tracked geographic shifts in climate conditions across the region. We demonstrate that outbreaks of hemlock sawfly and western blackheaded budworm have been observed across the Pacific coastal temperature rainforests of North America in each decade since the establishment of the Canadian and United States aerial survey programs. The distribution of outbreaks by both insects were best explained by host availability, a limited range of spring, summer, and winter temperatures, and minimum precipitation. Finally, we demonstrate that outbreaks have tracked the poleward shift in suitable climate over the last century. This study establishes a baseline understanding of the climatic constraints and biogeographic patterns of historic sawfly and budworm outbreaks across the Pacific coastal temperate rainforest and emphasizes the overarching importance of climate in driving the irruptive dynamics of these defoliator species.</p>
Fig. 2 in Foraging activity of Palmistichus elaeisis (Hymenoptera: Eulophidae) at various densities on pupae of the eucalyptus defoliator Thyrinteina arnobia (Lepidoptera: Geometridae)
Fig. 2. (A) Duraton of life cycle (egg to adult) and (B) numbers of Palmistichus elaeisis progeny with a density of 1, 3, 6, 9, 12, 15, 18, or 21 ovipositng females per Thyrinteina arnobia pupa at 25 ± 2 °C, 70 ± 10% RH, and a 12:12 h L:D photoperiod.
Fig. 1 in Foraging activity of Palmistichus elaeisis (Hymenoptera: Eulophidae) at various densities on pupae of the eucalyptus defoliator Thyrinteina arnobia (Lepidoptera: Geometridae)
Fig. 1. Percentage of pupae parasitzed and percentage of emergence of Palmistichus elaeisis with a density of 1, 3, 6, 9, 12, 15, 18, or 21 ovipositng females per Thyrinteina arnobia pupa at 25 ± 2 °C, 70 ± 10% RH, and a 12:12 h L:D photoperiod. Statstcal significance: parasitsm, P = 0.3770; emergence, P = 0.034.
Fig. 2 in Environmental determinants affecting the occurrence of defoliator caterpillars on Eucalyptus (Myrtaceae) plantations in the Brazilian Amazonian region
Fig. 2. Average annual growth of Eucalyptus urophylla (Myrtaceae) trees (m3 of wood per ha per yr) as a function of the total number of Lepidoptera individuals collected per light trap (Almeirim Municipality, Pará State, and Laranjal do Jari Municipality, Amapá State, Brazil).
Fig. 3 in Environmental determinants affecting the occurrence of defoliator caterpillars on Eucalyptus (Myrtaceae) plantations in the Brazilian Amazonian region
Fig. 3. Total number of individuals of the 2 Lepidoptera primary pests, Misogada bleura (Lepidoptera: Notodontidae) and Sarsina violascens (Lepidoptera: Lymantriidae), collected with light traps in Eucalyptus urophylla (Myrtaceae) plantations as a function of the distance from the area of native vegetation (Almeirim Municipality, Pará State, and Laranjal do Jari Municipality, Amapá State, Brazil).
Fig. 1 in Environmental determinants affecting the occurrence of defoliator caterpillars on Eucalyptus (Myrtaceae) plantations in the Brazilian Amazonian region
Fig. 1. Number of Oxydia vesulia (Lepidoptera: Geometridae) and Sarsina violascens (Lepidoptera: Lymantriidae) adults collected with light traps in Eucalyptus urophylla (Myrtaceae) plantations as a function of the number of rotations of this plant in the same area. (Almeirim Municipality, Pará State, and Laranjal do Jari Municipality, Amapá State, Brazil).
Data for: Tracking the temporal dynamics of insect defoliation by high-resolution radar satellite data
<p><span>1. Quantifying tree defoliation by insects over large areas is a major challenge in forest management, but it is essential in ecosystem assessments of disturbance and resistance against herbivory. However, the trajectory from leaf-flush to insect defoliation to refoliation in broadleaf trees is highly variable. Its tracking requires high temporal- and spatial-resolution data, particularly in fragmented forests. </span></p> <p><span>2. In a unique replicated field experiment manipulating gypsy moth <i>Lymantria dispar</i> densities in mixed-oak forests, we examined the utility of publicly accessible satellite-borne radar (Sentinel-1) to track the fine-scale temporal trajectory of defoliation. The ratio of backscatter intensity between two polarizations from radar data of the growing season constituted a canopy development index (CDI) and a normalized CDI (NCDI), which were validated by optical (Sentinel-2) and terrestrial laser scanning (TLS) data as well by intensive caterpillar sampling from canopy fogging. </span></p> <p><span>3. The CDI and NCDI strongly correlated with optical and TLS data (Spearman's ρ=0.79 and 0.84, respectively). The ∆NCDI<sub><sub>Defoliation</sub><sub> (</sub><sub>A</sub><sub>-</sub><sub>C</sub><sub>)<i> </i></sub></sub>significantly explained caterpillar abundance (R<sup>2</sup>=0.52). The NCDI at critical time-steps and ΔNCDI related to defoliation and refoliation well discriminated between heavily and lightly defoliated forests. </span></p> <p><span>4. We demonstrate that the high spatial and temporal resolution and the cloud independence of Sentinel-1 radar potentially enable spatially unrestricted measurements of the highly dynamic canopy herbivory. This can help monitor insect pests, improve the prediction of outbreaks, and facilitate the monitoring of forest disturbance, one of the high priority Essential Biodiversity Variables, in the near future.</span></p>
Defoliator outbreaks track with warming across the Pacific coastal temperate rainforest of North America
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Data from: Host plant phenology drives risky larval dispersal in an outbreaking insect defoliator
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Data for: Tracking the temporal dynamics of insect defoliation by high-resolution radar satellite data
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Stand inventory data (overstory and understory) in northern New Mexico forests affected by western spruce budworm (Choristoneura freemani Razowski) defoliation, 2012-2013
Stand Selection Stands were selected based on data provided by the United States Forest Service insect and disease aerial survey maps. The following criteria was used for stand selection: 1. At least 50% of pre-2000 species composition comprised of the same host tree; 2. No forest treatments within previous 20 years; and 3. Similar slope, aspect, vegetation association and elevation. Stands ranged from west-central New Mexico to north-central New Mexico. Sampling was completed in the summers of 2012 and 2013 in the Mount Taylor stands and the summer of 2013 for the remainder of the stands. Plots A randomized, systematic grid of ten clusters of two 0.02 ha plots were established using GIS software and exported to a handheld GPS. One plot of each cluster was located on the intersection of the grid (‘grid plots’) and the second located 50m at a random azimuth from the established grid plot (‘cluster plots’). This methodology was shown to improve sampling efficiency for stand characteristics pertaining to western spruce budworm within a set allowable error (Lynch 2003). Five 0.001 ha nested regeneration plots were also established (described below). Plot Characteristics Vegetation association was assessed using the Plant Associations of Arizona and New Mexico habitat typing guide. Canopy cover was recorded using a GRS densiometer in 1m increments on two 15.96 m transects bisecting plot center running north to south and east to west. Measurements will begin at 1m and extend to 15m totaling 15 measurements on the north to south transect. The east to west transect will exclude the measurement at 8m to avoid repeated measurements. Canopy cover was calculated by the number of canopy “hits” divided by the total number of measurements taken Overstory Measurements Species and diameter at breast height (DBH) was measured for all trees greater than 12.7 cm in diameter occurring in plot. DBH was considered to be 1.37 meters above ground. The height and canopy base height of each t
Bonanza Creek Experimental Forest Defoliating Insect Population Levels Per Leaf Beginning in 1975 - Kruse
The datafile has more detailed information including host species, a wider array of target species, date of sampling etc then the previous method of reporting found in Bonanza Creek Experimental Forest Defoliating Insect Population Levels Per Leaf Beginning in 1975 -Werner. The more detailed information was recorded starting in 2010.
Tracking invasions of a destructive defoliator, the gypsy moth (Erebidae: Lymantria dispar): population structure, origin of intercepted specimens, and Asian introgression into North America
Genetic data can help elucidate the dynamics of biological invasions, which are fueled by the constant expansion of international trade. The introduction of European gypsy moth (<i>Lymantria dispar dispar</i>) into North America is a classic example of human-aided invasion that has caused tremendous damage to North American temperate forests. Recently, the even more destructive Asian gypsy moth (mainly <i>L. d. asiatica</i> and <i>L. d. japonica</i>) has been intercepted in North America, mostly transported by cargo ships. To track invasion pathways, we developed a diagnostic panel of 60 DNA loci (55 nuclear and 5 mitochondrial) to characterize worldwide genetic differentiation within <i>L. dispar</i> and its sister species <i>L. umbrosa</i>. Hierarchical analyses supported strong differentiation and recovered five geographic groups that correspond to 1) North America, 2) Europe plus North Africa and Middle East, 3) the Urals, Central Asia, and Russian Siberia, 4) continental East Asia, and 5) the Japanese islands. Interestingly, <i>L. umbrosa</i> was grouped with <i>L. d. japonica</i>, and the introduced North American population exhibits remarkable distinctiveness from contemporary European counterparts. Each geographic group, with the exception of North America, shows additional lower-level structures when analyzed individually, which provided the basis for inference of the origin of invasive specimens. Two assignment approaches consistently identified a coastal area of continental East Asia as the major source for Asian invasion during 2014–2015, with Japan being another source. By analyzing simulation and laboratory crosses, we further provided evidence for the occurrence of natural Asian-North American hybrids in the Pacific Northwest, raising concerns for introgression of Asian alleles that may accelerate range expansion of gypsy moth in North America. Our study demonstrates how genetic data contribute to bio-surveillance of invasive species with results that can inform regulatory management and reduce the frequency of trade-associated invasions.
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Allen Brain Atlas
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