Amount Of Foliage Research Articles

A Portable Photocollector for the Field Collection of Insects in Biodiversity Assessment.

Arthropod biodiversity research usually requires large sample collections. The efficient handling of these samples has always been a critical bottleneck. Sweep netting along transects is an effective and commonly used approach to sample diverse insects. However, sweep netting requires the time-consuming task of sorting insects from the large amounts of debris and foliage that end up in the sweep net along with the insects. To address this, we introduce a robust, portable, and inexpensive photocollector device with an LED light source to extract insects from sweep net samples in a standardized way. Timed field trials tested the photocollector's efficiency in extracting live insect samples from debris, focusing on Hymenoptera and Diptera. We found that 73% (±13%) of undamaged specimens moved toward the collection bottle within the first hour and 79% (±13%) after four hours. Of the insects failing to move after four hours, most (81%) were damaged and likely unable to move. Accounting only for undamaged specimens, 83% (±11%) moved after 1 h and 90% (±11%) moved after 4 h. We found significant differences in when families of Hymenoptera and Diptera moved. We suggest that the photocollector can be a useful tool in standardized biodiversity assessments.

Evidence for widespread thermal acclimation of canopy photosynthesis.

Plants acclimate to temperature by adjusting their photosynthetic capacity over weeks to months. However, most evidence for photosynthetic acclimation derives from leaf-scale experiments. Here we address the scarcity of evidence for canopy-scale photosynthetic acclimation by examining the correlation between maximum photosynthetic rates (Amax,2,000) and growth temperature ( ) across a range of concurrent temperatures and canopy foliage quantity, using data from >200 eddy covariance sites. We detect widespread thermal acclimation of canopy-scale photosynthesis, demonstrated by enhanced Amax,2,000 under higher , across flux sites with adequate water availability. A 14-day period is identified as the most relevant timescale for acclimation across all sites, with a range of 12-25 days for different plant functional types. The mean apparent thermal acclimation rate across all ecosystems is 0.41 (-0.38-1.04 for 5th-95th percentile range) µmol m-2 s-1 °C-1, with croplands showing the largest acclimation rates and grasslands the lowest. Incorporating an optimality-based prediction of leaf photosynthetic capacities into a biochemical photosynthesis model is shown to improve the representation of thermal acclimation. Our results underscore the critical need for enhanced understanding and modelling of canopy-scale photosynthetic capacity to accurately predict plant responses to warmer growing seasons.

Dissecting the biochemical and hormonal changes of thidiazuron on defoliation of cotton CO17 (Gossypium hirsutum) to enhance mechanical harvest efficiency

Using chemical defoliants to remove cotton leaves represents a groundbreaking shift in cotton cultivation. The mechanization of cotton harvest is increasing, but a substantial amount of foliage that remains on the plant even at maturity is the major barrier for mechanical harvest. Properly completing mechanical and manual harvests requires artificial leaf detachment through defoliants. Still there is no proper defoliant concentration, application times and mechanism of action available. Therefore, the present study aimed to find an effective defoliant and application time to enhance mechanical harvest efficiency, along with a clear description of the mechanism of actions in cotton CO17 (Gossypium hirsutum). The field experiment was conducted during the year 2019-20 and used five concentrations of Thidiazuron defoliant (100, 150, 200, 250 and 300ppm) and Ethephon@0.5% (T2) in cotton variety CO17 to study the physiological, biochemical and hormonal responses at 120, 127 and 134 days after sowing. As a result, the concentrations of plant growth hormones, indole-3 acetic acid (4.9 fold), zeatin (32.7%) and gibberellic acid (7 fold) reduced. In contrast, abscisic acid (48.6%), jasmonic acid (34.9%), salicylic acid (2.15 fold) increased in the T7- Thidiazuron + Diuron (300 ppm) treatment followed by T5-Thidiazuron + Diuron (200 ppm). Additionally, the antioxidant enzymes ascorbate peroxidase, peroxidase, catalase, superoxide dismutase, cellulase in leaves, petiole and bolls were decreased due to defoliant T5- Thidiazuron + Diuron (200 ppm) followed by T7-Thidiazuron + Diuron (300 ppm), indicating that the hormone concentration, antioxidative and hydrolytic enzymes are ruled out and forces the defoliation process.

FIRST OCCURRENCE OF THE EXOTIC GASTROPOD Melanoides tuberculata IN THE STATE OF AMAPÁ (BRAZILIAN AMAZON REGION)

This study reports the first occurrence of the invasive gastropod Melanoides tuberculata (Müller, 1774) in the state of Amapá. M. tuberculata was first detected in a lake in Praça Floriano Peixoto, a city park located in Macapá, the state capital, on May 2, 2022. The lake has a substantial amount of foliage on the banks and relatively turbid water (with a green tint). This environmental characteristic is similar to that found in existing literature. As a consequence of this detection, it can be surmised that M. tuberculata is spreading through the Amazon region – thus far, its presence was restricted to the states of Pará, Mato Grosso, and Tocantins. Due to the potential ecological and economic impact, it is considered necessary to monitor the population density of M. tuberculata in Amapá, as well as to investigate possible mitigation measures, such as the introduction of a native fish that is capable of feeding itself on this invasive species.

Foliage consumption of the Honshu white admiral Limenitis glorifica Fruhstorfer, 1909 (Lepidoptera: Nymphalidae) on Japanese honeysuckle Lonicera japonica Thunb. (Dipsacales: Caprifoliaceae) in Aotearoa / New Zealand

Aotearoa / New Zealand harbours more naturalised non-native plant species than almost any other island group in the world, some of which are serious threats to indigenous biodiversity. Japanese honeysuckle (Lonicera japonica), a non-native climbing vine, is widespread across the country, and is considered a serious threat due to the nature of its growth habits and smothering effects upon indigenous flora. In 2014, the Honshu white admiral butterfly (Limenitis glorifica) was released in Aotearoa / New Zealand as a biological control agent, as this species has been shown to be narrowly oligophagous to Japanese honeysuckle. It is believed that the larva of this butterfly could cause substantial feeding damage; sufficient to reduce the plants’ fitness. However, the amount of foliage that could be consumed by Honshu white admiral larvae is unknown. This study monitored 30 larvae from egg to pupation, and found that a single larva could consume 2.13g of Japanese honeysuckle foliage before pupating. This equates to approximately 5.6 leaves (based on the mean weight of a mature honeysuckle leaf). These findings give an insight into the defoliation potential this biocontrol agent could have upon Japanese honeysuckle, although further research is needed to determine the physiological response of the invasive plant based on this level of herbivory.

Investigating accuracies of WorldView-2, Sentinel-2, and SPOT-6 in discriminating morphologically similar savanna woody plant species during a dry season

Accurate assessment of woody species diversity using remote sensing can assist ecologists by providing timely information for ecosystem management. The increasing availability of remotely sensed data necessitates the investigation of accuracies of different sensors in classifying plant species, especially during the dry season when foliage amount is low. WorldView-2, SPOT-6, and Sentinel-2 images were compared in detecting woody species (n = 27) and three coexisting land cover types in a savanna environment during a dry period. Random Forest (RF) and Support Vector Machine (SVM) classifiers were applied to each imagery to make a strong case for the comparison. The overall classification accuracies ranged between 52% and 65% for all images, with the WorldView-2 image performing the best followed by Sentinel-2 and SPOT-6 images. These accuracy rankings were similar for both the RF and SVM classifiers, with the former faring better. Pairwise comparison of the images using McNemar’s test showed significant differences between images in their ability to correctly identify woody species. Analysis of band importance revealed better contributions to the classifications of infrared bands for all images. Overall, the findings showed the potential of optical imagery in classifying and monitoring woody species hotspots in savanna environments even during a low photosynthesis season.

Impact of camphor on the in vitro mixed ruminal microorganism fermentation from goats selected for consumption of low and high levels of Juniperus spp. 1.

Encroaching plant species in West Texas continues to significantly reduce livestock production capacity and cause an imbalance between plant and livestock ecology. Juniperus ashei and Juniperus pinchotii are encroaching species rarely used by browsing animals, mainly due to phytochemical defenses. Juniperus spp. contain large concentrations of monoterpenes in their essential oil profiles to deter herbivory. Since 2003, two divergent bloodlines of meat goats have been selected to consume low or high (LJC or HJC) amounts of juniper foliage, through screening fecal samples with near-infrared reflectance spectroscopy. However, it remains unclear whether HJC goats expressed a physiological ability to consume a greater amount of juniper or if they were colonized by a ruminal microbial population that could detoxify juniper phytochemicals. Therefore, this study aimed to investigate the impact of 0.00 and 1.97 mM of camphor on the mixed ruminal microorganism fermentation after 0, 1, 2, 4, 12, and 24 h of incubation. Five LJC and five HJC goats were fed a juniper-free diet (n = 10) and five LJC and five HJC goats (n = 10), were fed a diet containing 30% fresh J. ashei leaves for 21 days prior to ruminal fluid collection. In vitro fermentations used LJC and HJC, ruminal fluid inoculum was added (33% v/v) to anoxic media in sealed Balch tubes. Total short-chain fatty acid (SCFA) production and acetate to propionate ratio were increased (P < 0.05), but there was no effect on pH (6.56 ± 0.09). Goats that received the juniper-free diet had higher (P < 0.05) SCFA production than juniper-containing diets. There was no consistent difference in LJC and HJC microbial fermentation end products caused by the addition of 1.97 mM of camphor, and goats receiving a juniper-free diet consistently generated more SCFAs in the presence of 1.97 mM of camphor. Furthermore, bloodline differences in juniper consumption were likely related to physiological adaption capacities within the animal and not a ruminal microbial detoxification advantage.

Abundance and Distribution of Foliage on Balsam Fir and White Spruce in Reference to Spruce Budworm Ecology and Absolute Population Density Estimation

We describe the distribution and amount of foliage, expressed as foliated branch surface area, weight, or number of buds in the live crown of healthy open-grown and closed-canopy balsam fir and white spruce trees. Balsam fir and white spruce have very similar total foliage surface area and weight. The live crown of white spruce trees contains fewer buds than balsam fir of similar dimensions. Thus, bud density per unit foliage weight or surface area is higher in balsam fir than in white spruce. We also observed that buds tend to grow in clusters more often on balsam fir than on white spruce, and that larvae of the spruce budworm preferentially attack buds that grow in clusters. Equations were developed to predict the total surface area and weight of foliage as well as number of buds in the live crown for estimation of absolute population density of spruce budworm. These equations use diameter at breast height (DBH) and the number of nodes in the live crown as predictors. When data on the number of live nodes are unavailable, it can be estimated from tree height. Equations were also developed from which to estimate foliage area, weight or bud numbers from DBH only.

Population Fluctuation of Disonycha teapensis Blake (Coleoptera: Chrysomelidae) in Crotalaria longirostrata Hook. &amp; Arn. (Fabales: Fabaceae) in Huimanguillo, Tabasco, Mexico

Objective: To establish the population fluctuation of Disonycha teapensis adults and larvae and to determine its relationship with the amount of damaged foliage, temperature, and precipitation. Methodology: The study was carried out in a n=48 Crotalaria longirostrata plant crop. The following data was recorded every week: number of adults and larvae, damaged leaflets percentage, plant phenology, temperature, and precipitation. Based on these data, monthly averages were calculated, and correlation analysis were performed between the population fluctuation of D. teapensis and the fluctuation of the damaged foliage percentage, temperature, and precipitation. Results: All the phenological stages of C. longirostrata were affected by the pest, which showed a constant population growth. The population fluctuation resembled the fluctuation of the damaged foliage percentage, with a significant positive correlation between both variables. Regarding temperature and precipitation, the correlation was negative but not significant; therefore, the relationship between population fluctuation and these climatic factors is not clear. Study Limitations: It was not possible to conduct the study for a full year. Conclusions: The population development of D. teapensis depends on the increase in the amount of foliage of its host plant. This insect attacks plants in all their phenological stages and the amount of damaged foliage is considerable.

Woody and Foliage Biomass, Foliage Traits and Growth Efficiency in Young Trees of Four Broadleaved Tree Species in a Temperate Forest.

The main goal of this study is to analyse and interpret interspecific differences in foliage biomass/area and woody parts biomass as well as the ratio between quantities of foliage and woody components (i.e., branches, stem and roots). The study was principally aimed at determining basic biomass allocation patterns and growth efficiency (GE) of four broadleaved species, specifically common aspen (Populus tremula L.), European hornbeam (Carpinus betulus L.), silver birch (Betula pendula Roth.) and sycamore (Acer pseudoplatanus L.) in young growth stages. We performed whole-tree sampling at 32 sites located in central and northern parts of Slovakia. We sampled over 700 trees and nearly 4900 leaves to quantify biomass of woody parts and foliage traits at leaf and tree levels. Moreover, we estimated specific leaf area in three parts of the crown, i.e., the upper, middle and lower thirds. We found that hornbeam had the largest foliage biomass and the lowest foliage area of all investigated species, while its biomass of woody parts did not differ from aspen and sycamore. Birch had the lowest biomass of woody parts, although its foliage properties were similar to those of aspen. Intraspecific differences of foliage were related to tree size and to leaf position along the vertical crown profile. Growth efficiency (GE), expressed as woody biomass production per foliage area unit, was evidently larger in hornbeam than in the other three broadleaves. We suggest that future GE modelling should utilize real values of stem diameter increment measured in a current year, bio–sociological position of trees and competition indicators as inputs. Such an approach would elucidate the role of stand structure and tree species mixture for ecological and production properties of forest stands.

Duration of response to nitrogen and phosphorus applications in mid-rotation Pinus taeda

We quantified the response duration to one-time applications of 112, 224, and 336 kg ha−1 of elemental nitrogen (112 N, 224 N, and 336 N, respectively) combined with 28 or 56 kg ha−1 of elemental phosphorus in mid-rotation Pinus taeda L. stands. Post-application measurements continued for 10 years at 32 sites in the southeastern United States and one site in Argentina, and we fit a Ricker model to data from each treatment in the event that a zero growth response was not observed in our measured data. The response duration was eight (measured), 14 (modeled), and 16 (modeled) years after treatment for the respective 112 N, 224 N, and 336 N treatments. The corresponding growth response per unit of applied nitrogen estimated from fertilization to when the growth response was not different from zero (whether measured or modeled) was 0.20, 0.16, and 0.13 m3 kg−1 for the 112 N, 224 N, and 336 N treatments, respectively. We hypothesized that the mechanism controlling the response duration was related to the amount of fertilizer nitrogen remaining in the foliage over time after treatment; previous studies found that nitrogen application had large impacts on the foliage amount and foliar nitrogen content. Based on retranslocation rate estimates from the literature of 67% of fertilizer nitrogen per year, our results suggest that a good correlation exists between the growth response and the amount of fertilizer nitrogen remaining in the foliage.

Field Measurement of Effective Leaf Area Index using Optical Device in Vegetation Canopy

Leaf area index (LAI) is an essential canopy variable describing the amount of foliage in an ecosystem. The parameter serves as the interface between green components of plants and the atmosphere, and many physiological processes occur there, primarily photosynthetic uptake, respiration, and transpiration. LAI is also an input parameter for many models involving carbon, water, and the energy cycle. Moreover, ground-based in situ measurements serve as the calibration method for LAI obtained from remote sensing products. Therefore, straightforward indirect optical methods are necessary for making precise and rapid LAI estimates. The methodological approach, advantages, controversies, and future perspectives of the newly developed LP 110 optical device based on the relation between radiation transmitted through the vegetation canopy and canopy gaps were discussed in the protocol. Furthermore, the instrument was compared to the world standard LAI-2200 Plant Canopy Analyzer. The LP 110 enables more rapid and more straightforward processing of data acquired in the field, and it is more affordable than the Plant Canopy Analyzer. The new instrument is characterized by its ease of use for both above- and below-canopy readings due to its greater sensor sensitivity, in-built digital inclinometer, and automatic logging of readings at the correct position. Therefore, the hand-held LP 110 device is a suitable gadget for performing LAI estimation in forestry, ecology, horticulture, and agriculture based on the representative results. Moreover, the same device also enables the user to take accurate measurements of incident photosynthetically active radiation (PAR) intensity.

Greening drylands despite warming consistent with carbon dioxide fertilization effect.

The rising atmospheric CO2 concentration leads to a CO2 fertilization effect on plants-that is, increased photosynthetic uptake of CO2 by leaves and enhanced water-use efficiency (WUE). Yet, the resulting net impact of CO2 fertilization on plant growth and soil moisture (SM) savings at large scale is poorly understood. Drylands provide a natural experimental setting to detect the CO2 fertilization effect on plant growth since foliage amount, plant water-use and photosynthesis are all tightly coupled in water-limited ecosystems. A long-term change in the response of leaf area index (LAI, a measure of foliage amount) to changes in SM is likely to stem from changing water demand of primary productivity in water-limited ecosystems and is a proxy for changes in WUE. Using 34-year satellite observations of LAI and SM over tropical and subtropical drylands, we identify that a 1% increment in SM leads to 0.15% (±0.008, 95% confidence interval) and 0.51% (±0.01, 95% confidence interval) increments in LAI during 1982-1998 and 1999-2015, respectively. The increasing response of LAI to SM has contributed 7.2% (±3.0%, 95% confidence interval) to total dryland greening during 1999-2015 compared to 1982-1998. The increasing response of LAI to SM is consistent with the CO2 fertilization effect on WUE in water-limited ecosystems, indicating that a given amount of SM has sustained greater amounts of photosynthetic foliage over time. The LAI responses to changes in SM from seven dynamic global vegetation models are not always consistent with observations, highlighting the need for improved process knowledge of terrestrial ecosystem responses to rising atmospheric CO2 concentration.

Influences of living and dead nematodes of Aphelenchoides besseyi (Aphelenchida: Aphelenchoididae) and artificial defoliation on rice seed ripening

Aphelenchoides besseyi Christie (Aphelenchida: Aphelenchoididae) is a seed-borne ectoparasite of rice Oryza sativa Linnaeus and the causative agent of white tip disease. To evaluate effects that the amount of substances translocated to seeds and the consumption by nematodes exert on seed size, 20 μL water containing 100 living or dead nematodes or no nematodes was inoculated individually into florets in bloom that appeared on culms with the amount of foliage modified: culms with no blades, half-cut blades, or intact blades of the three uppermost leaves. Inoculation of living A. besseyi nematodes into rice florets resulted in the highest proportion of light seeds (specific gravity < 1.0) whereas the removal of leaf blades had no effects on the occurrence of light seeds. Seed swelling, volume, weight, and volume density were the smallest for seeds derived from florets inoculated with living nematodes, indicating the effects of feeding by living nematodes. By contrast, those traits of seeds were not affected by the removal of leaf blades. Intriguingly, a positive correlation was found between nematode load per seed (total number of nematodes recovered) and seed weight when florets had been inoculated with living nematodes. Effects of nematodes on seed development was discussed.

Estimating cover fraction from TLS return intensity in coniferous and broadleaved tree shoots

Terrestrial laser scanning (TLS) provides a unique opportunity to study forest canopy structure and its spatial patterns such as foliage quantity and dispersal. Using TLS point clouds for estimating leaf area density with voxel-based methods is biased by the physical dimensions of laser beams, which violates the common assumption of beams being infinitely thin. Real laser beams have a footprint size larger than several millimeters. This leads to difficulties in estimating leaf area density from light detection and ranging (LiDAR) in vegetation, where the target objects can be of similar or even smaller size than the beam footprint. To compensate for this bias, we propose a method to estimate the per-pulse cover fraction, defined as the fraction of laser beams’ footprint area that is covered by vegetation targets, using the LiDAR return intensity and an experimental calibration measurement. We applied this method to a Leica P40 single-return instrument, and report our experimental results. We found that conifer foliage had a lower average per-pulse cover fraction than broadleaved foliage, indicating an increased number of partial hits in conifer foliage. We further discuss limitations of our method that stem from unknown target properties that influence the LiDAR return intensity and highlight potential ways to overcome the limitations and manage the remaining uncertainty. Our method’s output, the per-beam cover fraction, may be useful in a weight function for methods that estimate leaf area density from LiDAR point clouds.

Transformation of western hemlock (Tsuga heterophylla) tree crowns by dwarf mistletoe (Arceuthobium tsugense, Viscaceae)

AbstractDwarf mistletoes (Arceuthobium species) are arboreal, hemiparasitic plants of conifers that can change the structure and function of the tree crown. Hemlock dwarf mistletoe (Arceuthobium tsugense subsp. tsugense) principally parasitizes western hemlock (Tsuga heterophylla) and effects 10.8% of all western hemlock trees in Oregon, USA. In this study, we climbed 16 western hemlock trees (age 97–321 years, height 33–54.7 m) across a gradient of infection (0%–100% of branches infected) and measured occurrence of all dwarf mistletoe infections, dwarf mistletoe caused deformities, foliage, branch and crown metrics, and sapwood area. We then modelled over 25 different response variables using linear and generalized linear models with three metrics of severity as explanatory variables: total infection incidence, proportion of all live branches infected, and proportion of all live, infected branches with 33 per cent or more foliage distal to infection. A strong effect of dwarf mistletoe intensification was the reduction of branch foliage and an increase in the proportional amount of foliage distal to infections, with severely infected trees having the majority of foliage distal to infections. Increasing severity led to an apparent crown compaction as crown volumes decreased and became increasingly comprised of deformities. Sapwood area was unrelated to infection severity. Branch length and diameters were unrelated to increasing infection severity despite severely infected branches supporting 1–70 infections. The most severely infected tree had 3,615 individual plants in the crown. Our results suggested that shifts in crown structure and branch deformation, foliage amount, and foliage distal to infection, reflected a likely reduction of capacity for tree growth that coincided with a hypothesized increase in resource demand by dwarf mistletoe plants as infection severity intensified.

MODELIZACIÓN ESPACIAL DE LAS POBLACIONES DE Oligonychus perseae (TUTTLE, BAKER Y ABATIELLO, 1976) EN EL ESTADO DE MÉXICO

Oligonychus perseae es un ácaro conocido como araña cristalina que afecta al cultivo de aguacate (Persea americana), prácticamente a nivel mundial. En países como Estados Unidos de América y España se reporta como la principal plaga que afecta el follaje del aguacatero. Los daños incluyen afectación de los tejidos celulares de las hojas debido a la alimentación del ácaro, defoliación y hasta daños por mancha de sol debido a la baja cantidad de follaje en el árbol. El umbral económico de esta plaga se reporta entre 100 y 500 ácaros por hoja. La finalidad del presente estudio fue modelizar el comportamiento de las poblaciones de araña cristalina en cuatro municipios productores de aguacate en el Estado de México. Los resultados mostraron que los municipios más afectados por esta plaga fueron Donato Guerra y Temascaltepec. Se observó que el estrato más afectado fue el bajo con 40 arañas por hoja, en el que se encontraron hasta 130 ácaros por árbol. Las poblaciones de araña cristalina se distribuyen de manera agregada en los municipios muestreados y se apegan a modelos esféricos y gaussianos principalmente. Todos los muestreos se validaron adecuadamente mediante el proceso de validación cruzada. La distribución de las poblaciones se ilustró mediante mapas de densidad que muestran la ubicación precisa de los centros de agregación en los municipios muestreados. Con base en los mapas se calculó la superficie infestada, la que supera el 57 % de la superficie de los municipios evaluados

Factors controlling individual branch development during early growth of an experimental plantation of Eucalyptus pilularis in sub-tropical Australia

Branch sizes and their vertical orientation increase progressively further up the lower stem to support a newly developing crown. Diameter at base, orientation, and height up the stem of live branches on the lower 5 m of tree stems were measured several times over 2.5–5.7 years of age in an experimental plantation of blackbutt (Eucalyptus pilularis) in sub-tropical eastern Australia. Stocking density at planting varied over 816–1667 stems ha-1 and rectangularity of planting (ratio of distance between rows to distance between trees within rows) over 1–6. Tree stem diameters, heights and crown dimensions were also measured. The height above ground at which branches emerged from the stem was a primary factor determining their growth; the higher they were, the greater was their diameter and the more vertical their orientation. This was believed to reflect both a need for newer branches to grow larger than older branches, to support greater amounts of foliage as the crowns expanded towards full size, and for branches to be better oriented to seek sunlight as the crowns of surrounding trees also expanded. Secondary factors determining branch size were tree size and spacing between trees, factors that are likely to interact with each other. Larger trees tended to have larger branches, to support more leaf weight in larger crowns. The direction of emergence of branches from stems seemed little affected by tree or stand characteristics at these early stages of tree development. The results did not suggest any need to modify existing pruning regimes that have been developed for fast-growing eucalypt plantations in Australia.

Long-term dynamics of loblolly pine crown structure and aboveground net primary production as affected by site quality, planting density and cultural intensity

Crown attributes respond readily to silvicultural manipulations and mediate many aspects of stand structure, consequently they dynamically influence stand production. Numerous studies reported crown structure responses to intensive cultures or stand density and the relation between foliage quantity and growth efficiency at early stages of stand development. Long-term temporal patterns of crown structure and its relation to growth have been much less studied. With long-term remeasurement data from two loblolly pine culture-by-density studies, the roles of planting density, cultural intensity and site quality on crown structure, stand aboveground net primary production (ANPP), and growth efficiency were investigated using ANCOVA and linear mixed-effects modeling approaches. Using data from 480 destructively sampled trees, the Dirichlet regression modeling approach was used to analyze foliage and crown biomass allocations among the lower-, middle- and upper-third crown sections. Stands under different cultural intensities showed different temporal patterns of foliage biomass. Increased planting density or higher site quality enhanced wood production of loblolly pine. ANPP generally increased with increasing site quality, due to increased stand foliage biomass in the early stage of stand development, and mainly due to increased growth efficiency in the late stages of stand development. More intensive cultural treatments increased foliage biomass, thus increased ANPP at early ages; thereafter cultural intensity did not affect foliage biomass, ANPP, and growth efficiency. The trend of early age increases in both foliage biomass and ANPP resulting from increased planting density did not hold true with stand development. After correcting for the effects of tree size and dominance, cultural intensity still altered the vertical distribution of foliage biomass. More intensive culture resulted in an upward shift of foliage biomass.

Shifts in Foliage Biomass and Its Vertical Distribution in Response to Operational Nitrogen Fertilization of Douglas-Fir in Western Oregon

Nitrogen (N) fertilization is a commonly applied silvicultural treatment in intensively managed coast Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco var. menziesii) plantations. Field trials were established in a randomized complete block design by Stimson Lumber Company (Gaston, Oregon), to test the economic viability of N fertilization on their ownership and to better understand Douglas-fir growth responses. The 23 stands comprising the trials were Douglas-fir dominated, had a total age of 16–24 years, had been precommercially thinned, and had a density of 386–1021 trees ha−1. Fertilizer was applied aerially at a rate of 224 kg N ha−1 as urea during the 2009–2010 dormant season. In the dormant season of 2016–2017, seven growing seasons following application, 40 trees were felled and measured with the objective of assessing crown attributes and aboveground allometrics. Branch-level foliage mass equations were developed from 267 subsampled branches and were applied to the 40 felled sample trees on which the basal diameter and height of all live branches were measured, allowing estimation of both the total amount of foliage and its vertical distribution. A right-truncated Weibull distribution was fitted to data, with the truncation point specified as the base of live tree crown. The resulting tree-level parameter estimates were modeled as functions of tree-level variables. Stand-level factors not explicitly measured were captured through the use of linear and nonlinear mixed-effects models with random stand effects. Fertilization resulted in more total crown foliage mass in the middle crown-third and caused a downward shift in the vertical distribution of foliage, with implications for feedback responses in crown development and photosynthetic capacity. Defining the morphological responses of Douglas-fir crowns to nitrogen fertilization provides a framework for studying influences on stand dynamics and should ultimately facilitate improved site-specific predictions of stem-volume growth.