Spatial Pattern Of Damage Research Articles

Spatial patterns of damage and tree mortality in a selectively logged Atlantic Forest

Selective logging, a common disturbance in mixed-species and uneven-aged forests, can cause substantial collateral stand damage and tree mortality. Here we explore damage patterns and some mechanisms that increase post-harvest tree mortality in a selectively logged subtropical Atlantic Forest in Argentina. We investigate the spatial relations of felled and damaged trees through spatial point pattern analysis and evaluate the relationships between mortality and different endogenous (size - diameter at breast height: DBH; and wood density: WD) and exogenous (damage and neighboring basal area: NBA) factors. The permanent plots were logged in 1999, and the fates of all pre-logging live trees ≥10 cm DBH were evaluated 20 years later. Of the monitored 3973 trees, 381 with damaged concentrated within 10.5 m of felled tree stumps. Over the next twenty years mean mortality was higher and more variable for damaged than undamaged trees (47 % ± 10 % SE and 39 % ± 2 % SE, respectively), and the presence of damage interacted with the other analyzed factors. For undamaged trees, the probability of mortality declined with DBH and NBA but not with WD. For damaged trees, instead, the probability of mortality was related to an interaction between DBH, WD, and NBA. For damaged trees <30 cm DBH, mortality increased with WD and NBA, whereas for damaged trees ≥30 cm DBH, mortality peaked at both extremes of the WD range. For these large trees with low WD, the probability of mortality decreased with NBA, whereas for trees with high WD, the opposite was observed. Our findings suggest that selective logging affects the dynamics of forests by spatially concentrating damage and may alter subsequent tree deaths. This could have, long-term effects on forest structure. Increases in logging intensity would increase overall damage and spatially isolate trees (i.e., lower NBA), rendering them more vulnerable to wind damage and other external factors. Increased tree mortality will reduce forest carbon stocks and thereby jeopardize global efforts to mitigate climate change.

Evaluation of debris-flow building damage forecasts

Abstract. Reliable forecasts of building damage due to debris flows may provide situational awareness and guide land and emergency management decisions. Application of debris-flow runout models to generate such forecasts requires combining hazard intensity predictions with fragility functions that link hazard intensity with building damage. In this study, we evaluated the performance of building damage forecasts for the 9 January 2018 Montecito postfire debris-flow runout event, in which over 500 buildings were damaged. We constructed forecasts using either peak debris-flow depth or momentum flux as the hazard intensity measure and applied each approach using three debris-flow runout models (RAMMS, FLO-2D, and D-Claw). Generated forecasts were based on averaging multiple simulations that sampled a range of debris-flow volume and mobility, reflecting typical sources and magnitude of pre-event uncertainty. We found that only forecasts made with momentum flux and the D-Claw model could correctly predict the observed number of damaged buildings and the spatial patterns of building damage. However, the best forecast only predicted 50 % of the observed damaged buildings correctly and had coherent spatial patterns of incorrectly predicted building damage (i.e., false positives and false negatives). These results indicate that forecasts made at the building level reliably reflect the spatial pattern of damage but do not support interpretation at the individual building level. We found the event size strongly influences the number of damaged buildings and the spatial pattern of debris-flow depth and velocity. Consequently, future research on the link between precipitation and the volume of sediment mobilized may have the greatest effect on reducing uncertainty in building damage forecasts. Finally, because we found that both depth and velocity are needed to predict building damage, comparing debris-flow models against spatially distributed observations of building damage is a more stringent test for model fidelity than comparison against the extent of debris-flow runout.

Exploring the Spatial Pattern of Damage Caused by Typhoon Meranti on the Urban Green Space on Xiamen Island

Typhoons are the main cause of disturbances in the natural environment of coastal cities. Typhoons often damage the urban green space (UGS) of coastal cities, and the spatial pattern of such damages provides important information for disaster recovery. For acquiring such information, remote sensing technology offers a fast and effective means. This study investigated the spatial pattern of typhoon damage to UGS using Sentinel-2 data. To this end, the damage caused by Typhoon Meranti to the UGS of Xiamen Island (including Gulangyu Island) in 2016 was taken as a case study. The results showed that the overall area without vegetation coverage increased by 1159.7 ha. Areas with high vegetation coverage experienced less damage than areas with low vegetation coverage. A coldspot map of damage clusters was generated, and the map showed that severely damaged green areas were distributed in a striped pattern, indicating serious damage to road greening. In terms of direction, east-west roads experienced a higher degree of damage than north-south roads. The determined spatial pattern of the damage caused by Typhoon Meranti on the UGS of Xiamen Island provides a basis for the post-disaster restoration of the landscape of Xiamen Island.

Feeding and damage-induced volatile cues make beetles disperse and produce a more even distribution of damage for sagebrush.

Induced plant responses to herbivory are common, and we have learned a lot about the mechanisms of induced resistance and their effects on herbivore performance. We know less about their effects on herbivore behaviour and especially on spatial patterns of damage. Theoretical models predict that induced responses can cause patterns of damage to become aggregated, random or even. A recent model predicted that informed herbivore movement coupled with communication between plants would make damage more even within individual plants. We tested these predictions in the field using a specialist beetle Trirhabda pilosa that feeds on sagebrush Artemisia tridentata. Both the beetle and the plant are well-documented to respond to damage-induced volatile cues. Beetle larvae were more likely to move from damaged leaves and leaves that had been exposed to volatiles from nearby damaged leaves compared to undamaged control leaves. Previous laboratory results indicated that beetles were more likely to choose undamaged leaves compared to damaged leaves or those exposed to volatile cues of damage. A comparison of damage patterns early in the season and after completion of beetle feeding revealed that variance in damage among branches decreased as the season progressed; that is, damage became more evenly distributed among the branches within a plant. Larvae damaged many leaves on a plant but removed relatively little tissue from each leaf. Herbivore movement and the spatial patterns of damage that it creates can be important in determining effects on plant fitness and other population processes. Dispersion of damage deserves more consideration in plant-herbivore studies.

Reduced Peripapillary and Macular Vessel Density in Unilateral Postgeniculate Lesions With Retrograde Transsynaptic Degeneration.

Retrograde transsynaptic degeneration (RTSD) of the retinal ganglion cells and retinal nerve fiber layer after postgeniculate injury has been well documented, but to the best of our knowledge, associated retinal microvascular changes have not been examined. The purpose of our study was to assess vessel density (VD) at macular and peripapillary regions in patients with RTSD. Cross-sectional study including 16 patients with homonymous visual field defects secondary to unilateral postgeniculate visual pathway injury and 18 age-matched controls. All participants were examined with AngioVue optical coherence tomography angiography to measure the peripapillary vessel density and macular vessel density (pVD/mVD) as well as the peripapillary retinal nerve fiber layer (pRNFL) and macular ganglion cell complex (GCC) thicknesses. The pRNFL and macular ganglion cell-inner plexiform layer (GCIPL) thicknesses also were evaluated using Cirrus OCT. A normalized asymmetry score (NAS) was calculated for GCIPL and GCC thickness, and mVD. Average pRNFL and macular GCIPL/GCC thicknesses were significantly thinner in both eyes of patients compared with control eyes (all P ≤ 0.05). Eight patients (50%), who showed a RTSD of the GCIPL map, had a relative thinning of the GCIPL/GCC ipsilateral to the brain lesion in both eyes (represented by a positive GCIPL-NAS/GCC-NAS). The mean pVD and mVD also were significantly reduced in patients (all P ≤ 0.05). There was a strong correlation between GCIPL-NAS/GCC-NAS and mVD-NAS index in both eyes (all r > 0.7, P = 0.001). Furthermore, there was a similar spatial pattern of damage for the macular GCC thickness and VD values. We demonstrated a significant VD decrease in peripapillary and macular areas of patients with RTSD because of postgeniculate lesions. The structural and microvascular asymmetry indexes were significantly correlated. These findings provide new insights regarding transsynaptic degeneration of the visual system.

Real time structural modal identification using recursive canonical correlation analysis and application towards online structural damage detection

A novel reference free approach for identifying structural modal parameters using recursive canonical correlation analysis (RCCA) is proposed in this paper. Using first order eigen perturbation (FOEP) approach, the method provides eigenspace updates at each instant of time from which the linear normal modes (LNMs) of a vibrating system can be determined. Modal assurance criterion (MAC), examined in a recursive framework, is utilized to compare the theoretical modes with the estimated LNMs in order to verify the accuracy of the obtained modes. The eigenspace updates provide basis vectors that can be subsequently utilized to determine potential damage induced to the system. The set of transformed responses obtained at each time stamp is fit using time varying auto regressive (TVAR) models in order to aid as damage sensitive features (DSFs) for identifying temporal and spatial patterns of damage. The proposed RCCA algorithm based on the FOEP approach can accommodate multi-directional dependencies of a system. Numerical simulations carried out on linear systems demonstrate the efficacy of the proposed method in recursively separating the structural modes. Comparative case studies with the batch CCA based method illustrate the superlative performance of the RCCA scheme towards recursively identifying the modes of a system, an aspect that is significantly missing in the context of online structural health monitoring (SHM) literature. The extension of the method in detecting spatio-temporal patterns of damage for both linear and nonlinear systems demonstrates the effectiveness of the proposed scheme as a real time damage detection technique. Application of the method towards experimental setups devised under controlled laboratory environment in identifying structural modes and determining the change of state of the structure greatly demonstrate the robustness of the method as an ideal candidate for baseline free, real time SHM.

Robust linear and nonlinear structural damage detection using recursive canonical correlation analysis

Abstract A novel approach for robust damage detection of linear and nonlinear systems using recursive canonical correlation analysis (RCCA) is proposed in this paper. The method generates proper orthogonal modes (POMs) at each time stamp that are recursively tracked to provide iterative eigenspace updates, using first order eigen perturbation (FOEP) method. The transformed responses obtained are subsequently fit using time varying auto regressive (TVAR) models, in order to aid as damage sensitive features (DSFs) for identifying temporal and spatial patterns of damage. As most of the past work utilize offline algorithms that gather data in windows and operate in batch mode, recursive algorithms that provide iterative eigenspace updates at each instant of time, are missing in the context of structural health monitoring (SHM). This greatly motivates the development of the present work, where the both uni and multi directional structural responses are considered to be available in real time. The transformed responses are obtained by using the proposed algorithm that utilizes FOEP for multi-directional block covariance structure to solve the recursive generalized eigenvalue problem. The TVAR coefficients modeled on the transformed responses obtained in real time using FOEP, and residual error examined in a recursive framework, act as efficient real time DSFs for detecting damage online. Numerical simulations carried out on nonlinear systems and backed by experimental setups devised in controlled laboratory conditions, demonstrate the efficacy of the RCCA algorithm. Application of the proposed algorithm on the combined ambient and earthquake responses obtained from the UCLA Factor Building, demonstrates the robustness of the proposed methodology as an ideal candidate for real time SHM.

The assessment of wildlife damage estimation methods in maize with simulation in GIS environment

Wildlife damage to agriculture causes significant economic losses worldwide. The amount of compensation payment is often determined by field damage evaluation, but there is little statistically sound information on the applied sampling and calculation methods of such losses. In this study, we tested the accuracy and bias of V-Track Method (VTM), W-Track Method (WTM), Double Diagonal Method (DDM), and Grid Arrangement Method (GAM) in GIS environment. Besides the accuracies and biases, the effects of the rate and spatial distribution of the damage (and the interaction of these factors) on the sampling results were examined. Simulations were conducted with four different spatial damage patterns [random, aggregated in patches (DAinP), furthermore aggregated in one and two field edges (DAinE-1, DAinE-2) to simulate the effect of an adjacent forest on the damage caused by big game species] and three levels of damage (10%, 20%, 30%). According to our results, the GAM provided the majority (58.3%) of best results for each statistical parameter (28/48), while gave the worst result three times. The WTM resulted in the highest number (17/48) of worst values and 8/48 best results. The DDM gave 14/48 poorest values, while provided 7/48 best results. The VTM resulted in 14/48 worst values, while provided the best result five times. The rate and spatial distribution of the damage, as well as the interaction of these factors, had a significant effect on the Percentage Relative Bias of the VTM, WTM and DDM estimations, while the GAM sampling was significantly affected only by the damage distribution.

Analysis of game damage estimation methods in winter wheat (Triticum aestivum) thruogh GIS simulations

Wildlife damage to agriculture causes significant economic loss worldwide annually. Game managers or hunters are responsible for the financial compensation of the crop damage caused by game species in several countries, including Hungary. Accredited experts estimate the level of the damage; however, currently, there are no standardised methods that would be obligatory to apply. In order to obtain information on the accuracy and bias of the different sampling methods, we designed GIS simulations in winter wheat (Triticum aestivum), which covers a significant proportion of the arable land not only in Hungary, but also globally.&#x0D; We tested two sampling methods with three sampling plot arrangements in a GIS environment. Our questions were the following: (1) How accurate and biased are the examined samplings? (2) Does the rate or the spatial distribution of the damage (or the interaction of these factors) affect the results of the investigated methods?&#x0D; We created 15 wheat field models with 1:2 side ratio, 12 cm row width and the area of 3 ha. We simulated 5 damage rates (10%, 30%, 50%, 70%, 90%) and 3 spatial damage patterns [random, aggregated in 1 and 2 field edges], of which the latter two follow the actual pattern of crop damage caused by big game species. V, W and X sampling tracks were allocated on each field model, and then they were sampled with square shaped, 1 m2 quadrats and 1 m long row sections (with 5 repetitions). The sample size was 20 and 25 plots, respectively (determined by the original description of the methods). At the sample plots, the total number of plants and the number of damaged plants were counted.&#x0D; According to our results, the statistical parameters of the different samplings were similar; the difference between the best and the poorest values was low. The rate and spatial distribution of the damage, as well as their interaction, had a significant effect on the estimation of each quadrat sampling, while the row sections were significantly affected only by the damage distribution (V and W tracks) or the damage rate (X track).&#x0D; According to our findings however, the difference between the labour-intensity of the two approaches can be decisive. With the sample sizes in our study, remarkably lower number of plants had to be examined along the row sections, than in the quadrats. This suggests that the experts can obtain similar quality results with less effort, if they choose the row section sampling over the quadrats.

Diffusion tensor imaging shows mechanism-specific differences in injury pattern and progression in rat models of acute spinal cord injury

We investigate the ability of diffusion tensor imaging (DTI) to distinguish between three experimental rat models of spinal cord injury mechanism – contusion, dislocation, and distraction. Ex vivo DTI scans were performed on cord specimens that were preserved at different time points of the acute injury (3 hr, 24 hr, and 7 days post-injury) across all three injury mechanisms. White matter was classified as abnormal if their DTI metric was substantially different from regional values measured from a set of uninjured controls, thus allowing generation of binary “white matter damage maps” which categorizes each pixel in the DTI image as “normal” or “damaged”. Damage classification was most robust using thresholds in the longitudinal diffusivity, which supports previous studies that show that longitudinal diffusivity is the most robust DTI metric in depicting damage in SCI. Furthermore, the spatial damage patterns from all subjects in the same group were consolidated into a "damage occurrence ratio map", which illustrates an average damage shape that characterizes the injury mechanism. Our analysis has yielded a dataset which highlights the differences in injury pattern due to the initial mode of mechanical injury. For example, contusion produced an initial injury that emanated radially outward from the central canal, with subsequent damage along the caudal corticospinal tract and rostral gracile fasciculus; dislocation injuries showed a high level of involvement in the lateral and ventral white matter which became less apparent by 7 days post-injury, and distraction injuries were found to be less focal and more distributed rostrocaudally. This work represents a first step in adopting the use of the primary injury mechanism as a clinical prognostic factor in SCI, which may help to inform the trialing of existing neuroprotective treatment candidates, the development of new therapies as well as personalize the management of SCI for the individual patient.

Extraordinary Claims Require Extraordinary Evidence: Centrally Mediated Preservation of Binocular Visual Field in Glaucoma is Unlikely.

We have read with interest the recent article by Sponsel et al.1 There is much evidence that glaucomatous damage occurs at the optic nerve head,2 and therefore we were surprised by the authors' conjecture that there may be a central mechanism that preserves the binocular visual field in advanced glaucoma. If indeed there were some central mechanism responsible for “interlocking” monocular visual field defects to preserve binocular function, patients' binocular damage should, on average, be less severe than would be expected if the spatial pattern of damage in both fellow eyes were independent. We tested this simple hypothesis as follows: visual field pairs (24-2, Humphrey Field Analyzer; Carl Zeiss Meditec, Dublin, CA) from patients with glaucoma (mean deviation worse than −2.5 dB in both eyes) were taken from the datasets of previous studies. One dataset (n = 2463) was from Halifax, Canada; the second (n = 854,5), from Rotterdam, the Netherlands, is freely available from http://www.orgids.com/ (last accessed 7/31/2014). From both datasets, we selected the most recent pair of right and left visual fields from each patient. Similar to Sponsel et al.,1 we calculated the integrated visual field6 as a proxy measure of the true binocular visual field for each of these patients (total n = 331). The greater of the two monocular sensitivities was used to represent the “binocular” sensitivity at each location, and the mean sensitivity (MSTRUE, in dB) was derived as a summary index. Then, for comparison, we derived the distributions of the binocular sensitivities (MSRANDOM, dB) that would have been obtained if the right visual field had been paired with the left visual field of 20 different patients who had left MS within ± 2.0 dB of the true left MS This was possible for n = 298 patients. By comparing MSTRUE with MSRANDOM, a distribution of differences (MSTRUE − MSRANDOM) is obtained for each individual patient. Under the null hypothesis of randomness, MSTRUE will be similar to MSRANDOM (mean difference ≈ 0). If indeed there existed a central mechanism that minimizes binocular damage, the MSTRUE should be systematically better than MSRANDOM (mean difference > 0). We found no evidence for such an effect (Fig. 1). In fact, true binocular visual fields were typically slightly worse than the integrated fields derived from randomly matched pairs (median difference between MSTRUE and MSRANDOM, −0.4 dB, Wilcoxon P < 0.001). This effect appeared to increase with visual field damage, and it is probably explained by the common disease process and predisposition of anatomically similar fellow eyes. Coexisting neurological damage (e.g., from strokes) would also cause homonymous visual field damage and contribute to this effect. Figure 1. MSTRUE versus mean difference in MS (MSTRUE – MSRANDOM) for 298 patients with glaucoma. Error bars representing ±1 SEM are shown for 50 randomly selected patients distributed across the range of MSTRUE. The data are not suggestive of binocular ... A power analysis (Fig. 2) suggests that, with our approach, samples of n = 100 would provide ample power to detect even small amounts (∼1 dB) of binocular visual field preservation if such an effect had existed. Thus, the small effect in the opposite direction suggests that centrally mediated binocular visual field preservation is unlikely in glaucoma. Figure 2. Power to detect differences between MSTRUE and MSRANDOM of varying magnitude when n = 100 and between-patient SD of differences is as shown, corresponding approximately to MSTRUE of 15, 20, and 25 dB. A study of this size is powered to detect even a small ... Extraordinary claims require extraordinary evidence. In a paper published nearly 10 years ago, Ioannidis7 explained “why most published research findings are false”: hypotheses with a low prior probability of being true require strong evidence to generate a post-study probability of being true greater than that of being false, but many researchers are mislead by hypothesis tests (P values) into overestimating the strength of their evidence.7 While we disagree on binocular visual field preservation in glaucoma, we thank Sponsel et al.1 for a stimulating paper. The question of how, and when, visual field damage impairs real-world visual performance is one of the most important topics in glaucoma, and we hope that many other groups will contribute to this discussion.

Short-wavelength infrared defect emission as a probe of degradation processes in 980 nm single-mode diode lasers

Infrared emission from 980-nm single-mode high power diode lasers is recorded and analyzed in the wavelength range from 0.8 to 8.0 μm. A pronounced short-wavelength infrared (SWIR) emission band with a maximum at 1.3 μm originates from defect states located in the waveguide of the devices. The SWIR intensity is a measure of the non-equilibrium carrier concentration in the waveguide, allowing for a non-destructive waveguide mapping in spatially resolved detection schemes. The potential of this approach is demonstrated by measuring spatially resolved profiles of SWIR emission and correlating them with mid-wavelength infrared (MWIR) thermal emission along the cavity of devices undergoing repeated catastrophic optical damage. The enhancement of SWIR emission in the damaged parts of the cavity is due to a locally enhanced carrier density in the waveguide and allows for an analysis of the spatial damage patterns. The figure shows a side view of a diode laser during catastrophic degradation as recorded by a thermocamera within 5 successive current pulses. The geometry of the device is given in grayscale. The position of the laser chip is indicated by the dotted line. The thermal signatures of the internal degradation of the diode laser are overlaid in color. The bi-directional spread of the damage along the laser cavity is clearly visible.

Simulating wind disturbance impacts on forest landscapes: Tree-level heterogeneity matters

Wind is the most detrimental disturbance agent in Europe's forest ecosystems. In recent years, disturbance frequency and severity have been increasing at continental scale, a trend that is expected to continue under future anthropogenic climate change. Disturbance management is thus increasingly important for sustainable stewardship of forests, and requires tools to evaluate the effects of management alternatives and climatic changes on disturbance risk and ecosystem services. We here present a process-based model of wind disturbance impacts on forest ecosystems, integrated into the dynamic landscape simulation model iLand. The model operates at the level of individual trees and simulates wind disturbance events iteratively, i.e., dynamically accounting for changes in forest structure and newly created edges during the course of a storm. Both upwind gap size and local shelter from neighboring trees are considered in this regard, and critical wind speeds for uprooting and stem breakage are distinguished. The simulated disturbance size, pattern, and severity are thus emergent properties of the model. We evaluated the new simulation tool against satellite-derived data on the impact of the storm Gudrun (January 2005) on a 1391 ha forest landscape in south central Sweden. Both the overall damage percentage (observation: 21.7%, simulation: 21.4%) as well as the comparison of spatial damage patterns showed good correspondence between observations and predictions (prediction accuracy: 60.4%) if the full satellite-derived structural and spatial heterogeneity of the landscape was taken into account. Neglecting within-stand heterogeneity in forest conditions, i.e., the state-of-the-art in many stand-level risk models, resulted in a considerable underestimation of simulated damage, supporting the notion that tree-level complexity matters for assessing and modeling large-scale disturbances. A sensitivity analysis further showed that changes in wind speed and soil freezing could have potentially large impacts on disturbed area and patch size. The model presented here is available as open source. It can be used to study the effects of different silvicultural systems and future climates on wind risk, as well as to quantify the impacts of wind disturbance on ecosystem services such as carbon sequestration. It thus contributes to improving our capacity to address changing disturbance regimes in ecosystem management.

Technical Note: Patterns of Urban Forest Debris from the 2004 and 2005 Florida Hurricane Seasons

Abstract Urban tree debris generation and damage resulting from seven hurricanes during the 2004 and 2005 Florida hurricane seasons was analyzed using a random sample of communities in highly affected counties. Woody debris amounts, rates, and costs for cleanup were quantified, as were the spatial patterns of damage across the state. Average debris volume per mile of street segment was 488 cubic yards, and cost of removal and disposal averaged $21.50 per cubic yard. Urban forest structure, community characteristics, and hurricane severity influenced debris and cost results. Spatial analyses indicated that debris results were clustered into northwest and southeast areas of the state, which represent two distinct ecoregions in Florida. Although southeastern Florida had much higher costs per cubic yard than the northwest, the debris volume per road mile was higher in the northwest portion of the state. On a per-mile basis, Hurricane Ivan was responsible for the greatest debris volume, and Hurricane Katrina was the most expensive. These results can be used to help communities plan for hurricane response and management activities and to estimate potential damage to their urban forest resource.

Reply to ‘Using remote sensing to assess the protective role of coastal woody vegetation against tsunami waves’

In a recent paper in the International Journal of Remote Sensing, Olwig et al. [28 (2007) 3153–3169] present a comprehensive, geographic information system (GIS)‐based description of the spatial distribution of damage from the 2004 Indian Ocean tsunami relative to coastal vegetation in Tamil Nadu, India, and conclude that ‘…mangrove forests and coastal shelterbelts provided protection from the [t]sunami.’ In this comment, we demonstrate that the complex spatial pattern of damage makes their observational approach unable to substantiate this claim. Contrary to the authors' assertions, other factors known to affect tsunami inundation, such as elevation, near‐shore bathymetry and patterns of land use, are shown to vary across their study site so as to create the appearance of a mitigating effect by vegetation on inundation and damage. We show that without explicitly quantifying and controlling for these confounding factors, it cannot be ascertained, even in principle, whether vegetation did ameliorate tsunami damage. We conclude with a call for analyses that can simultaneously assess the role of the discernibly manifold factors generating the pattern of inundation and damage of the 2004 tsunami.

Habitat use and spatial patterns of wild boar Sus scrofa (L.): agricultural fields and edges

Rapidly increasing populations of wild boar in Sweden and Europe cause much damage to crops, and there is a critical need for more knowledge about their habitat utilization, especially of agricultural fields. In our study, we first assess the spatial pattern of damage in relation to the edges of agricultural fields. Next, with the aid of global positioning system collars, we studied the pattern of movement of wild boar on agricultural fields. Finally, in order to understand the role of agricultural fields, we studied how habitat selection may vary throughout the year. We found edge effects on damage patterns in agricultural fields. During winter and spring, we found wild boar not only to follow edges, but also to move along narrow landscape elements within agricultural fields. In our habitat analysis, we found strong avoidance of exposed agricultural fields throughout the year, but significantly less when crops are ripe.

Topoedaphic and morphological complexity of foliar damage and mortality within western juniper (Juniperus occidentalis var. occidentalis) woodlands following an extreme meteorological event

AbstractAim An extreme early season freeze event in October 2002 resulted in significant foliar damage and/or mortality within western juniper woodlands. We identify the geographical patterns of tree damage based on morphological, topographical and edaphic parameters, and discuss the ecological implications of this event.Location Oregon, USA (44.0–44.2° N, 120.3–120.9° W).Methods We sampled trees on four matched pairs of disturbed and minimally disturbed study sites within the core area of tree damage. We collected information about age, morphology (height, basal area, level of foliar damage), and topographic position (elevation, slope, aspect) for each tree sampled using dendroecological and GPS/GIS procedures. We collected plot‐level data on tree density and degree of cover for shrubs and grasses. We used a series of Mann–Whitney, Kruskal–Wallis and Wilcoxon tests and graphical analyses to determine if significant differences exist in our collected variables both between matched pairs and within our disturbed sites.Results Topographically, we found that aspect was a critical element regulating damage, with trees in colder microenvironments (north‐westerly slopes) experiencing less damage because they were further along in the annual process of cold‐hardening. The majority of damaged trees were found in areas of higher density and more even age structure that are typical of recent juniper afforestation. Morphologically, we show that trees with greater basal areas and/or less stature were less likely to have foliar damage, consistent with winter cavitation.Main conclusions Our results show that the spatial pattern of damage was closely related to topography and tree morphology, parameters that, in turn, correspond closely to differences between the historical locales of western juniper and juniper woodlands that have emerged in a 100+ year period of rapid afforestation. This freeze event fits the criteria for a large, infrequent disturbance in that it was spatially complex and may act as an endogenous factor that can contribute to stand maintenance.

Effects of the Spatial Pattern of Leaf Damage on Growth and Reproduction: Whole Plants

Because of differences in their foraging patterns, different herbivores are likely to have different effects on plant fitness. We compared the effects of two contrasting patterns of leaf damage on the growth and reproduction of the wild gourd Cucurbita pepo ssp. texana. Plants were assigned to one of four damage treatments: (1) concentrated (15% damage on every third leaf); (2) dispersed (5% on each leaf); (3) high intensity (15% on each leaf); and (4) control (undamaged). We measured the growth rate of the main vegetative axis of the plants, internode length, the proportions of staminate and pistillate nodes, the proportions of staminate and pistillate buds that reached anthesis, the proportion of pistillate flowers that produced fruit, pollen production and pollen grain size, fruit production, fruit size, number of seeds per fruit, and seed size. Only one trait was significantly affected by the spatial pattern of damage: pollen production per flower increased under the concentrated but not the dispersed...

Effects of the spatial pattern of leaf damage on growth and reproduction: nodes and branches

1 We assessed the influence of the spatial pattern of leaf damage on growth and reproduction (through both male and female functions) of the wild gourd, Cucurbita pepo L. ssp. texana at three structural levels of the plant (nodes, primary branches and entire branch systems). 2 We applied concentrated or dispersed leaf damage treatments (removing 5% of original leaf area in both), and compared their effects on 12 traits, ranging from the production of new nodes through flower production to pollen performance and seed number/size. 3 Only one of the traits was affected by the spatial pattern of damage, and then only at the primary branch level, where pollen performance was greater in the concentrated than in the dispersed treatment. 4 Regardless of the spatial pattern of damage, we found that low to moderate levels of foliar damage significantly affected very few traits. This indicates a high tolerance of simulated herbivory. Overcompensation for one trait (pollen performance) occurred at the node and primary branch levels. 5 The results suggest that compensatory resources can be translocated within damaged branches.

Landscape patterns of hemlock decline in New England due to the introduced hemlock woolly adelgid

AbstractAim The hemlock woolly adelgid (HWA; Adelges tsugae Annand), a small, aphid‐like insect native to Japan, is currently migrating northward through eastern North America and threatens to eliminate eastern hemlock [Tsuga canadensis (L.) Carriere], one of the most abundant, long‐lived shade tolerant species, across its range. The major objectives of this study were: (1) to characterize the pre‐HWA distribution, composition, and structure of hemlock stands; (2) to characterize the spatial patterns of damage generated by HWA across southern New England since the time of its arrival in 1985; and (3) to examine environmental and stand factors that are associated with declines in crown vigour and mortality of hemlock.Location Our study was conducted in a 4900‐km2 study region extending from Long Island Sound northward to the Massachusetts border and including the Connecticut River Valley in Connecticut, USA.Methods Aerial photographs and extensive field study were used to map and develop GIS overlays of 1000 hemlock stands in our study region. Intensive sampling of a random selection of 114 hemlock stands across the study area was used to document patterns of hemlock infestation, vigour, and mortality in relation to stand and site characteristics. Mantel tests were utilized to assess the relative importance of environmental and stand variables in controlling the intensity of HWA infestation and damage.Results Most stands were located along ridge tops, steep hillsides and narrow valleys. Hemlock importance values ranged from 22 to 96% and stand densities varied from 300 to 1450 stems ha–1. Adelgid presence and adelgid‐induced hemlock mortality were found in 88 and 74% of the sampled forests, respectively. Approximately 25% of stands were logged recently, ranging in intensity from partial hemlock cutting to large clearcuts. A geographical trend in reduced HWA infestation intensity and tree mortality and enhanced crown vigour of overstory and understory hemlock occurs from south to north, coincident with the temporal colonization pattern of HWA. Mantel analyses indicated that patterns of HWA infestation, hemlock mortality, and crown vigour were most strongly correlated with latitude. Mortality was also weakly related to aspect and stand size. Average mortality was highest on western aspects but exceeded 20% on most slopes. Remaining trees averaged over 50% foliar loss, with no significant difference among aspects.Main conclusions Results suggest that as HWA becomes abundant, stands on xeric aspects succumb rapidly, but that stand and landscape variables such as overstory composition and structure, slope, and elevation, exert little control over susceptibility or eventual mortality. Ultimately, duration of infestation controls the intensity of hemlock decline and mortality. Over 4290 ha of hemlock forest have been eliminated by logging or HWA just within the southern part of our transect since the mid‐1980s, and we predict continued HWA infestation will lead to unprecedented hemlock loss throughout the north‐eastern USA, regardless of site conditions or location.