Canopy Health Research Articles

Stem canker caused by Phomopsis spp. Induces changes in polyamine levels and chlorophyll fluorescence parameters in pecan leaves

Pecan plants are attacked by the fungus Phomopsis spp. that causes stem canker, a serious and emerging disease in commercial orchards. Stem canker, which has been reported in several countries, negatively affects tree canopy health, eventually leading to production losses. The purpose of this study was to inquire into the physiology of pecan plants under stem canker attack by Phomopsis spp. To this end, pecan plants were inoculated with an isolate of Phomopsis spp. and several parameters, such as polyamines, proline, sugars, starch, chlorophyll fluorescence and canopy temperature were analysed. Under artificial inoculation, a high disease incidence was observed with symptoms similar to those in plants showing stem canker under field conditions. Furthermore, the infected stem showed dead tissue with brown necrotic discolouration in the xylem tissue. The free polyamines putrescine, spermidine, and spermine were detected and their levels decreased as leaves aged in the infected plants with respect to the controls. Chlorophyll fluorescence parameters, such as Sm, ψEO, and QbRC decreased under plant infection and therefore the K-band increased. Canopy temperature and proline content increased in the infected plants with respect to the controls while sugar content decreased. These data suggest that stem canker caused by Phomopsis spp. induces physiological changes that are similar to those observed in plants under drought stress. To our knowledge, this is the first study that documents the physiological and biochemical effects derived from pecan-Phomopsis interaction.

Chronic nociplastic pain affecting the musculoskeletal system: clinical criteria and grading system.

Chronic nociplastic pain affecting the musculoskeletal system: clinical criteria and grading system.

Dynamics of deforestation and forest degradation hotspots applying geo-spatial techniques, apalchand forest in terai belt of himalayan foothills: Conservation priorities of forest ecosystem

The forest cover or broadly forest health is gradually deteriorated day by day due to unexpected population growth, agricultural expansion and infrastructural development mainly in tropical and sub-tropical regions of the world. The Forest fragmentation rate as well as number of vulnerable forest hotspots is significantly intensified within Himalayan terai belt specifically in different pockets of Apalchand forest (India). This paper attempts to identify the vulnerable forest hotspots, fragmentation zone and forest canopy density. The relevant methods such as FCD model, spatial autocorrelation (Moran's I) and clustering (Getis-Ord Gi*statistics), forest fragmentation transformation matrix have been used to analyze the spatiotemporal changing patterns of forest fragmentation and canopy health of Apalchand forest. The result shows that the Z-score value is high in the year 1988 and comparatively low in the year 2020, so it has been observed that the forest condition in 2020 is more fragile in comparison with the year 1988. Meanwhile, the Getis-Ord Gi* statistics along with IDW method clearly illustrate the clustering of hot-spot and cold-spot regions with high level of significance (90%, 95% and 99%). Similarly, the areas of Patch and Perforated class have been considerably increased with respect to the years1988 and 2000. The hot spot zones are being enlarged in the south-eastern and middle parts of the Apalchand forest. The anthropogenic factors like expansion of tea gardens and agricultural land, infrastructural development, illegal timber trafficking are responsible for rapid fragmentation (Patch, Edge, Perforated areas) as well as reduction of canopy cover in different pockets of the study area. The alternative forest policy is highly required for the conservation of forest ecosystem as well as forest dwellers and forest fringe people.

Field Performance of ‘Hamlin’ Orange Trees Grown on Various Rootstocks in Huanglongbing-endemic Conditions

Most of the commercially important citrus scion cultivars are susceptible to Huanglongbing (HLB), which is the most devastating disease the citrus industry has ever faced. Because the rootstock can influence the performance of the scion in various ways, including disease and pest tolerance, use of superior rootstocks can assist citrus growers with minimizing the negative effects of HLB. The objective of this study was to assess rootstock effects on the horticultural performance and early production potential of ‘Hamlin’ sweet orange (Citrus sinensis) trees in commercial field settings under HLB-endemic conditions. Two field trials were conducted in different locations in Central and Southeast Florida. The trials were established in 2015 and included 32 diverse diploid and tetraploid rootstock cultivars and advanced selections. One trial was performed in Highlands County, FL, on a poorly drained flatwoods-type site. Another trial was performed in Polk County, FL, on a well-drained sandy Central Florida Ridge site. Horticultural traits including tree height, canopy volume, trunk diameter, canopy health, leaf nutrient content, yield, and fruit quality were assessed during the 2018–19 and 2019–20 production years. Significant differences were found among trees on different rootstocks for most of the measured traits, particularly tree vigor and productivity, but rootstock effects also varied by location. Rootstocks that induced large tree sizes, such as the diploid mandarin × trifoliate orange hybrids ‘X-639’, ‘C-54’, ‘C-57’, and ‘C-146’, also induced higher yield, but with lower yield efficiency. Most of the tetraploid rootstocks significantly reduced tree size, among which ‘Changsha+Benton’, ‘Green-3’, ‘Amb+Czo’, ‘UFR-3’, and ‘UFR-5’ induced high yield efficiency. Therefore, these rootstocks have the potential to be used in high-density plantings. However, trees on some of these small size-inducing rootstocks had a higher mortality rate and were more vulnerable to tropical force winds. This study provides important information for the selection of rootstocks with the greatest production potential in an HLB-endemic environment, especially during the early years of production.

Development and performance evaluation of a machine vision system and an integrated prototype for automated green shoot thinning in vineyards

AbstractGreen shoot thinning in vineyards is an essential, perennial operation for maintaining canopy health and optimizing yield and quality of wine grapes. Use of mechanized thinning system, which is essential to reduce labor dependency and associated cost, causes high variability in shoot removal efficiency due to difficulty in precisely positioning the thinning end‐effector along cordon trajectories. Automated/robotic solution for precise positioning of the thinning end‐effector could significantly improve the performance and efficiency of mechanical green shoot thinning. This study presents: (i) a machine vision‐based cordon detection system that can estimate cordon trajectories at different shoot growth stages in a vineyard; and (ii) evaluation of an integrated green shoot thinning system capable of automatically positioning the thinning end‐effector following vine cordon trajectories. The developed machine vision system uses deep learning‐based techniques that could accurately estimate cordon trajectories with root mean square error (RMSE) of 7.3, 10.3, and 16.1 pixels for canopy images captured in 2–4 weeks of shoot growth, respectively. Then, a control strategy was presented for the integrated system, which receives the computed cordon trajectories from machine vision system to automatically position the thinning end‐effector to cordon trajectories. Field evaluations in a research vineyard showed that the integrated system can achieve an RMSE of 1.47 cm in following the cordon trajectories at 6.6 cm·s−1forward speed. Future work will incorporate additional sensing system to detect individual shoot on cordon and integrating it with an existing system to achieve higher level of precision in green shoot thinning.

Aerial Application Methods for Control of Weed Species in Fallow Farmlands in Texas

Prolific growth of weeds, especially when followed by abundant rainfall, is common in Texas farmlands during early winter and progresses into spring when farmers begin chiseling and disking operations for spring-seeded cropping. This research sought to develop aerial application technologies designed to control unwanted vegetation in croplands left fallow until spring. The aerial nozzles used in the study were conventional hydraulic (CP), rotary atomizer, and electrostatically (ES) charged nozzles. Glyphosate at 0.4145 kg ae·ha−1 was applied on weeds using a fixed-wing aircraft equipped with various aerial nozzles used as treatments. The spray application rate for the conventional and rotary atomizer nozzles was 28.1 L·ha−1, while that for the ES charged nozzle was 9.4 L·ha−1. Aerial and ground-based remote sensing and visual estimates quantified weed vigor and canopy health. Both the CP and rotary atomizer nozzles were efficacious in suppressing weeds. ES charged on nozzles at one-third of the spray application rate of the CP and the rotary atomizer nozzles were equally effective in reducing weed vigor. More aerially applied replicated field research trials conducted over time and space are needed to unravel the differences between aerial spray nozzle technologies for controlling weed populations in Texas farmlands.

Societal issues and policy implications related to the use of cannabinoids, cannabis, and cannabis-based medicines for pain management.

Societal issues and policy implications related to the use of cannabinoids, cannabis, and cannabis-based medicines for pain management.

Detection of necrotic foliage in a young Eucalyptus pellita plantation using unmanned aerial vehicle RGB photography – a demonstration of concept

ABSTRACT Recent advances and commercialisation of unmanned aerial vehicle/red blue green (RGB) camera systems and digital photogrammetric techniques now provide a cheap and flexible alternative to higher-cost airborne platforms for routine monitoring of canopy health in timber plantations. Structure-from-Motion photogrammetry produces very dense three-dimensional (3D) point clouds which can be used to derive metrics for inventory estimation. Unmanned aerial vehicle RGB photography also captures data that can relate to tree health. In contrast to the more common use of orthorectified RGB photography to extract this spectral information, we used the software package Agisoft Photoscan to assign a simple Vegetation Index value directly to each point in the 3D point cloud. Using data acquired by a DJI Phantom 4 Pro, we present a simple processing and photogrammetric workflow solution for detecting dead and dying trees in a young Eucalyptus pellita plantation located in the provenance of Riau, Sumatra. Trees affected by the bacterial wilt Ralstonia sp. present symptoms of necrotic foliage on individual branches or the whole crown. Assigning the Visible Atmospheric Resistant Index Vegetation Index colour-coded values to individual points in the 3D point cloud significantly enhanced visualisation of necrotic foliage on individual trees in both the point cloud and the associated orthophoto compared to the RGB equivalent images. This approach could easily be operationally deployed for the rapid detection and mapping of unhealthy trees with symptoms of necrotic foliage.

Modelling of Wine Production Using Land Surface Temperature and FAPAR—The Case of the Douro Wine Region

The vegetative development of grapevines is orchestrated by very specific meteorological conditions. In the wine industry vineyards demand diligent monitoring, since quality and productivity are the backbone of the economic potential. Regional climate indicators and meteorological information are essential to winemakers to assure proper vineyard management. Satellite data are very useful in this process since they imply low costs and are easily accessible. This work proposes a statistical modelling approach based on parameters obtained exclusively from satellite data to simulate annual wine production. The study has been developed for the Douro Demarcated Region (DDR) due to its relevance in the winemaking industry. It is the oldest demarcated and controlled winemaking region of the world and listed as one of UNESCO’s World Heritage regions. Monthly variables associated with Land Surface Temperatures (LST) and Fraction of Absorbed Photosynthetic Active Radiation (FAPAR), which is representative of vegetation canopy health, were analysed for a 15-year period (2004 to 2018), to assess their relation to wine production. Results showed that high wine production years are associated with higher than normal FAPAR values during approximately the entire growing season and higher than normal values of surface temperature from April to August. A robust linear model was obtained using the most significant predictors, that includes FAPAR in December and maximum and mean LST values in March and July, respectively. The model explains 90% of the total variance of wine production and presents a correlation coefficient of 0.90 (after cross validation). The retained predictors’ anomalies for the investigated vegetative year (October to July) from 2017/2018 satellite data indicate that the ensuing wine production for the DDR is likely to be below normal, i.e., to be lower than what is considered a high-production year. This work highlights that is possible to estimate wine production at regional scale based solely on low-resolution remotely sensed observations that are easily accessible, free and available for numerous grapevines regions worldwide, providing a useful and easy tool to estimate wine production and agricultural monitoring.

Neighboring Tree Effects and Soil Nutrient Associations with Surviving Green Ash (Fraxinus pennsylvanica) in an Emerald Ash Borer (Agrilus planipennis) Infested Floodplain Forest

Few ash trees (Fraxinus spp.) have survived the initial devastation that emerald ash borer beetle (EAB) (Agrilus planipennis) has caused in natural populations. We studied green ash (Fraxinus pennsylvanica) trees in a floodplain population after >90% of ash had died from EAB infestation. We examined the relationship among the canopy health classes of surviving ash trees and their nearest neighboring trees (within 6 m) and available soil nutrients. A subset of focal ash trees was randomly selected within health classes ranging from healthy to recently deceased. Focal trees with the healthiest canopy class had significantly fewer ash neighbors compared to declining health classes. Other species of tree neighbors did not have a significant impact on surviving ash tree canopy health. Nutrients in soils immediately surrounding focal trees were compared among health classes. Samples from treeless areas were also used for comparison. There was a significantly greater amount of sulfur (ppm) and phosphorus (mg/kg) in ash tree soil compared to treeless area soil. The relationships between these soil nutrient differences may be from nutrient effects on trees, tree effects on nutrients, or microsite variation in flooded areas. Our data do not directly assess whether these ash trees with healthier canopies have increased resistance to EAB but do indicate that at neighborhood scales in EAB aftermath forests, the surviving ash trees have healthier canopies when separated at least 6 m from other ash trees. This research highlights scale-dependent neighborhood composition drivers of tree susceptibility to pests and suggests that drivers during initial infestation differ from drivers in aftermath forests.

The potential to characterize ecological data with terrestrial laser scanning in Harvard Forest, MA.

Contemporary terrestrial laser scanning (TLS) is being used widely in forest ecology applications to examine ecosystem properties at increasing spatial and temporal scales. Harvard Forest (HF) in Petersham, MA, USA, is a long-term ecological research (LTER) site, a National Ecological Observatory Network (NEON) location and contains a 35 ha plot which is part of Smithsonian Institution's Forest Global Earth Observatory (ForestGEO). The combination of long-term field plots, eddy flux towers and the detailed past historical records has made HF very appealing for a variety of remote sensing studies. Terrestrial laser scanners, including three pioneering research instruments: the Echidna Validation Instrument, the Dual-Wavelength Echidna Lidar and the Compact Biomass Lidar, have already been used both independently and in conjunction with airborne laser scanning data and forest census data to characterize forest dynamics. TLS approaches include three-dimensional reconstructions of a plot over time, establishing the impact of ice storm damage on forest canopy structure, and characterizing eastern hemlock (Tsuga canadensis) canopy health affected by an invasive insect, the hemlock woolly adelgid (Adelges tsugae). Efforts such as those deployed at HF are demonstrating the power of TLS as a tool for monitoring ecological dynamics, identifying emerging forest health issues, measuring forest biomass and capturing ecological data relevant to other disciplines. This paper highlights various aspects of the ForestGEO plot that are important to current TLS work, the potential for exchange between forest ecology and TLS, and emphasizes the strength of combining TLS data with long-term ecological field data to create emerging opportunities for scientific study.

Quantifying the Severity of Phytophthora Root Rot Disease in Avocado Trees Using Image Analysis

Phytophthora root rot (PRR) infects the roots of avocado trees, resulting in reduced uptake of water and nutrients, canopy decline, defoliation, and, eventually, tree mortality. Typically, the severity of PRR disease (proportion of canopy decline) is assessed by visually comparing the canopy health of infected trees to a standardised set of photographs and a corresponding disease rating. Although this visual method provides some indication of the spatial variability of PRR disease across orchards, the accuracy and repeatability of the ranking is influenced by the experience of the assessor, the visibility of tree canopies, and the timing of the assessment. This study evaluates two image analysis methods that may serve as surrogates to the visual assessment of canopy decline in large avocado orchards. A smartphone camera was used to collect red, green, and blue (RGB) colour images of individual trees with varying degrees of canopy decline, with the digital photographs then analysed to derive a canopy porosity percentage using a combination of ‘Canny edge detection’ and ‘Otsu’s’ methods. Coinciding with the on-ground measure of canopy porosity, the canopy reflectance characteristics of the sampled trees measured by high resolution Worldview-3 (WV-3) satellite imagery was also correlated against the observed disease severity rankings. Canopy porosity values (ranging from 20–70%) derived from RGB images were found to be significantly different for most disease rankings (p < 0.05) and correlated well (R2 = 0.89) with the differentiation of three disease severity levels identified to be optimal. From the WV-3 imagery, a multivariate stepwise regression of 18 structural and pigment-based vegetation indices found the simplified ratio vegetation index (SRVI) to be strongly correlated (R2 = 0.96) with the disease rankings of PRR disease severity, with the differentiation of four levels of severity found to be optimal.

Consideration of peg strength and disease severity in the decision to harvest peanut in southeastern USA

ABSTRACTThe indeterminate nature and underground fruiting habit of peanut (Arachis hypogaea L.) makes it a challenge to determine the optimal harvest time. The objectives of this study were (1) to gain additional information about how maturity and canopy health influence peg strength, yield, and grade and (2) to address anecdotal claims of differences in peg strength and digging losses among cultivars. Field trials were established in Citra, FL, and Tifton, GA. Two peanut cultivars (“Georgia-06G” and “Tifguard”) were grown under two fungicide programs (full program: every 14-day spraying interval; and reduced program: every 28-day spraying interval), and harvested at three different maturity levels (early, optimum, and late based on an accumulated growing degree day method). The fungicide program had a significant impact on yield only in 2013 at Citra, likely because the canopy structure was decreased because of fungal disease known as leaf spots (causal agents: Cercospora arachidicola and Cercosporidium personatum). The timing of the harvest had a significant impact on yield, grade, peg strength, and digging loss. In addition, yield, grade, peg strength, and digging losses differed between the peanut cultivars. These results show that reduced fungicide program might affect the yield because of the disease severity and that the optimal harvest time should consider the level of the defoliation. Although there was no correlation between peg strength and digging loss, over-maturity can cause more digging losses compared to optimal harvest time. Tifguard had higher digging loss than Georiga-06G. This study provides additional useful information on cultivars to growers.

Episodic Canopy Structural Transformations and Biological Invasion in a Hawaiian Forest.

The remaining native forests on the Hawaiian Islands have been recognized as threatened by changing climate, increasing insect outbreak, new deadly pathogens, and growing populations of canopy structure-altering invasive species. The objective of this study was to assess long-term, net changes to upper canopy structure in sub-montane forests on the eastern slope of Mauna Kea volcano, Hawai‘i, in the context of continuing climate events, insect outbreaks, and biological invasion. We used high-resolution multi-temporal Light Detection and Ranging (LiDAR) data to quantify near-decadal net changes in forest canopy height and gap distributions at a critical transition between alien invaded lowland and native sub-montane forest at the end of a recent drought and host-specific insect (Scotorythra paludicola) outbreak. We found that sub-montane forests have experienced a net loss in average canopy height, and therefore structure and aboveground carbon stock. Additionally, where invasive alien tree species co-dominate with native trees, the upper canopy structure became more homogeneous. Tracking the loss of forest canopy height and spatial variation with airborne LiDAR is a cost-effective way to monitor forest canopy health, and to track and quantify ecological impacts of invasive species through space and time.

Does the removal of Lantana camara influence eucalypt canopy health, soil nutrients and site occupancy of a despotic species?

Weed removal experiments provide strong evidence for weed impacts, validating management techniques and demonstrating the means by which biodiversity can be maintained. We examined the effects of removing Lantana (Lantana camara) through herbicide application in eucalypt-dominated sclerophyll forest and, then measured the response of soil carbon and nitrogen levels, tree canopy health and the density of Bell Miners (Manorina melanophrys) a bird species thought to amplify the negative impacts of Lantana on tree health. Four sites in northern New South Wales were monitored for 2.5years. We measured Lantana health, (index of height, number of stems and leaves present), soil nutrients (nitrogen and carbon at two depths: 0–10cm and 20–30cm), Bell Miner density (using acoustic methods) and eucalypt canopy health (5 trees/quadrat) in six 50×50m quadrats per site (n=24; 12 treated, 12 untreated). Lantana foliage in treated quadrats was sprayed with glyphosate. Lantana showed significant reductions in health within 6months of treatment and remained in a debilitated state compared to control quadrats for the duration of the project. Despite this, soil nutrients, Bell Miner density and canopy health did not differ between intact and treated quadrats for up to 2years after treatment. The lack of impact on soil nutrient level or tree canopy health despite large changes in Lantana abundance in treatment sites was unexpected, and may indicate that Lantana is unimportant in shaping these measures. However, a more likely explanation is that longer term monitoring is required before the full impact of Lantana removal can be detected. The level of habitat modification following herbicide application was insufficient to stimulate relocation of Bell Miner colonies. Further investigation is required into how Lantana removal affects Bell Miner density, soil nutrient levels and canopy health in the medium to long term.

Hemlock Woolly Adelgid (Hemiptera: Adelgidae) Abundance and Hemlock Canopy Health Numerous Years After Imidacloprid Basal Drench Treatments: Implications for Management Programs.

Hemlock woolly adelgid (Adelges tsugae [Annand]), an invasive insect in the eastern United States, has caused widespread decline of eastern hemlock, Tsuga canadensis (L.) Carriére. Imidacloprid basal drench treatments were assessed 4-7 yr after a single treatment to determine hemlock woolly adelgid population suppression and effects on hemlock canopy health. The effects of sampling site, years post-treatment, and hemlock diameter at breast height (DBH) size classes were evaluated relative to imidacloprid treatment on hemlock woolly adelgid populations and hemlock canopy health characteristics. The influence of hemlock woolly adelgid populations on canopy health characteristics was also assessed. Imidacloprid treatments resulted in low-level hemlock woolly adelgid populations 7 yr post-treatment. Hemlock woolly adelgid was present on more hemlocks 7 yr compared with 4-6 yr post-treatment. Smaller hemlocks, dosed with 0.7 g active ingredient (AI)/2.5 cm DBH, had higher populations of hemlock woolly adelgid than the largest size class, which were treated at twice that dosage. Concentrations of imidacloprid and its olefin metabolite below the LC50 were sufficient for suppression of hemlock woolly adelgid populations, which suggests an additive effect of imidacloprid and olefin that compounds hemlock woolly adelgid mortality over many generations. Hemlock woolly adelgid populations observed in this study were too low to have an observable effect on hemlock canopy health, indicating that application intervals of up to 7 yr may be adequate to protect hemlocks.

Large wood in central Appalachian headwater streams: controls on and potential changes to wood loads from infestation of hemlock woolly adelgid

AbstractLarge wood (LW) is an important component of forested headwater streams. The character of LW loads reflects a balance between adjacent valley processes that deliver LW to the channel (herein recruitment processes) and stream channel processes that either retain or transport LW through the reach (herein retention processes). In the central Appalachian Mountains, USA, LW characteristics in headwater streams located in eastern hemlocks (Tsuga candensis) forests are expected to change because of infestation of hemlock woolly adelgid (Adelges tsugae, HWA), an exotic, invasive insect. We examined LW characteristics in 24 headwater streams ranging from un‐infested to severe infestation, as determined by hemlock canopy health. The objectives of this work were to: (i) quantify wood loads; (ii) assess the relative importance of valley recruitment and in‐stream retention mechanisms in controlling reach‐scale wood loads; and (iii) assess if there was a detectable influence of HWA on LW loads. We hypothesized that LW loads would be similar to other forested streams in eastern USA and dominated by recruitment processes. In addition, higher LW loads would correspond with advanced HWA infestation. Mean wood frequency was 38 pieces/100 m ± 17 (standard deviation); mean wood volume was 3.69 m3/100 m ± 2.76. In general, LW load characteristics were influenced by both recruitment and retention parameters; jam (accumulations ≥ 3 pieces) characteristics were dominated by retention parameters. Results suggest that adjacent stand basal area influences LW loads and once LW is recruited to the channel, streams lack sufficient hydraulic driving forces, despite having lower resistance structures, to transport LW out of the reach. Sites in moderate decline had higher proportions of short (1–2 m and 1–4 m) and very long (>10 m) LW with higher frequency of jams that were low in volume. We present a hypothesized conceptual model of expected changes to LW loads associated with HWA infestation and hemlock mortality. Copyright © 2015 John Wiley & Sons, Ltd.

Effects of soil drenching of water-soluble potassium silicate on commercial avocado (Persea americana Mill.) orchard trees infected with Phytophthora cinnamomi Rands on root density, canopy health, induction and concentration of phenolic compounds

Avocado root rot, caused by Phytophthora cinnamomi Rands, remains a major constraint to avocado production worldwide. In the current study effects of successive soil drench applications of soluble potassium silicate on canopy health and root density of 13-year-old Persea americana Mill. trees infected with P. cinnamomi were investigated. Soil drenching with 20 l per tree of a 20 ml l-1 soluble potassium silicate solution (20.7% silicon dioxide) resulted in significantly higher root density when compared to untreated control trees, and trees injected with potassium phosphonate (Avoguard®) during most but not all evaluation dates. Three successive drenches of soluble potassium silicate resulted in the most significant increase in root density. A similar effect was seen on canopy health. In general, total soluble phenolic concentrations were significantly higher between March 2005 and January 2006 in those trees drenched three times with soluble potassium silicate per growing season (up to 72.62 µg l-1) compared to trees injected twice with potassium phosphonate per growing season (up to 68.77 µg l-1) and untreated control trees (51.62 µg l-1). This evidence suggests that multiple or even continuous applications of soluble potassium silicate to avocado trees will be required to effectively suppress Phytophthora cinnamomi over the entire growing season.

Effects of Acidic Deposition and Soil Acidification on Sugar Maple Trees in the Adirondack Mountains, New York

We documented the effects of acidic atmospheric deposition and soil acidification on the canopy health, basal area increment, and regeneration of sugar maple (SM) trees across the Adirondack region of New York State, in the northeastern United States, where SM are plentiful but not well studied and where widespread depletion of soil calcium (Ca) has been documented. Sugar maple is a dominant canopy species in the Adirondack Mountain ecoregion, and it has a high demand for Ca. Trees in this region growing on soils with poor acid-base chemistry (low exchangeable Ca and % base saturation [BS]) that receive relatively high levels of atmospheric sulfur and nitrogen deposition exhibited a near absence of SM seedling regeneration and lower crown vigor compared with study plots with relatively high exchangeable Ca and BS and lower levels of acidic deposition. Basal area increment averaged over the 20th century was correlated (p < 0.1) with acid-base chemistry of the Oa, A, and upper B soil horizons. A lack of Adirondack SM regeneration, reduced canopy condition, and possibly decreased basal area growth over recent decades are associated with low concentrations of nutrient base cations in this region that has undergone soil Ca depletion from acidic deposition.

Remote Sensing for Vadose Zone Hydrology—A Synthesis from the Vantage Point

Ground‐based, air‐borne, and space‐borne remote sensing techniques have evolved over the past several decades and provided many new techniques for estimating various land surface attributes at multiple scales related to mass and energy dynamics. The vadose zone, encompassing land surface, root zone, and the deeper soil profile down to the groundwater table, is a complex domain, particularly related to various hydrologic and biological processes across different scales. In this zone, spatial distributions and temporal dynamics of soil moisture and evapotranspiration (ET), including their interdependence, are critical to climate feedback, hydrology, and plant canopy health. Their temporal and spatial variability across catchments affect surface and subsurface runoff, modulates evaporation and transpiration, determines the extent of groundwater recharge and contaminant transport, and initiates or sustains feedback between the land surface and the atmosphere. With the recent development and deployment of various remote sensing platforms working with different techniques such as optical, microwave, gravitational, infrared, and other sensors, improved temporal and spatial measurement or estimates of soil moisture, evapotranspiration, soil hydraulic parameters, soil salinity, and vegetation attributes are possible. In this special section “Remote Sensing for Vadose Zone Hydrology,” 14 contributions on fundamental and applied studies using different remote sensing platforms, including satellite retrieval algorithm development, data assimilation techniques, scaling issues, ground validation, and field applications in the context of vadose zone hydrology are presented. The foci of these papers range across root zone soil moisture retrieval and variability, evapotranspiration dynamics and distribution, agricultural water management, soil hydraulic and mechanical property estimation, ecosystems assessment, land–atmosphere interaction, and land surface hazard assessment. Here we organized the summary of these papers in four overlapping sections including (i) estimation, variability, scaling, and data assimilation of soil moisture by microwave remote sensing; (ii) estimating evapotranspiration by remote sensing and water management applications; (iii) estimating vadose zone properties by remote sensing; and (iv) ground‐based soil moisture for calibration and validation of microwave remote sensing.