Planting in Metallized Reflective Mulch Did Not Significantly Benefit Development of New Hybrid Citrus Seedlings

The U.S. Department of Agriculture citrus scion breeding program is urgently working on developing huanglongbing (HLB; pathogen Candidatus Liberibacter asiaticus)-tolerant cultivars with excellent fruit quality and productivity when HLB-affected. The slow process of assessing new citrus hybrids is a major impediment to delivery of these much-needed cultivars. We generate thousands of hybrids each year, germinate the seedlings, grow them for 2 years in the greenhouse, plant them at high density in a field where the disease HLB is abundant, grow them for 5 to 10 years, and make selections based on tree performance and fruit quality of these HLB-affected trees. Based on promising reports of accelerated citrus growth when grown in a metallized reflective mulch (MRM) system, we tested the hypothesis that the MRM system may accelerate growth and selection of new hybrid seedlings compared with conventional soil culture (CSC). In the MRM system, tree rows are covered with a layer of metallized plastic film and drip irrigation is installed beneath the plastic. In 2 years of analysis, tree canopy volume was significantly greater with MRM in 2020 (27% greater than CSC) but not in 2021, and MRM tree height was greater in 2021 (7% greater than CSC). Mortality was significantly greater with MRM in both 2020 and 2021(in 2021: 32% vs. 17% under CSC), and MRM trees had more chlorotic leaves. Because of staff limitations, plant debris and soil were not routinely cleared from MRM, thus diminishing any benefit from the reflective surface. Better maintenance might have resulted in more sustained evidence of MRM growth benefits. With the current resource availability, the MRM system does not appear to accelerate the assessment of hybrid seedling trees.

Apple Fruit Growth and Quality Depend on the Position in Tree Canopy

Modern apple orchard systems should guarantee homogeneity of fruit internal and external qualities and fruit maturity parameters. However, when orchards reach productive age, a variation of these parameters takes place and mostly it is related to uneven light distribution within the tree canopy. The aim of the study was to evaluate the canopy position’s effect on fruit internal and external quality parameters. This is the first study where all the main fruit quality and maturation parameters were evaluated on the same trees and were related to the light conditions and photosynthetic parameters. Four fruit positions were tested: top of the apple tree, lower inside part of the canopy, and east and west sides of the apple tree. Fruit quality variability was significant for fruit size, blush, colour indices, total sugar content, dry matter concentration, accumulation of secondary metabolites and radical scavenging activity. Fruit position in the canopy did not affect flesh firmness and fruit maturity parameters such as the starch index, Streif index and respiration rate. At the Lithuanian geographical location (55°60’ N), significantly, the highest fruit quality was achieved at the top of the apple tree. The tendency was established that apple fruits from the west side of the canopy have better fruit quality than from the east side and it could be related to better light conditions at the west side of the tree. Inside the canopy, fruits were distinguished only by the higher accumulation of triterpenic compounds and higher content of malic acid. Light is a main factor of fruit quality variation, thus all orchard management practices, including narrow two-dimensional tree canopies and reflecting ground covers which improve light penetration through the tree canopy, should be applied.

CLASSIFICATION OF TRANSLATIONAL LANDSLIDE ACTIVITY USING VEGETATION ANOMALIES INDICATOR (VAI) IN KUNDASANG, SABAH

This paper introduced a novel method of landslide activity mapping using vegetation anomalies indicators (VAIs) obtained from high resolution remotely sensed data. The study area was located in a tectonically active area of Kundasang, Sabah, Malaysia. High resolution remotely sensed data were used to assist manual landslide inventory process and production on VAIs. The inventory process identified 33, 139, and 31 of active, dormant, and relict landslides, respectively. Landslide inventory map were randomly divided into two groups for training (70%) and validation (30%) datasets. Overall, 7 group of VAIs were derived including (i) tree height irregularities; (ii) tree canopy gap; (iii) density of different layer of vegetation; (iv) vegetation type distribution; (v) vegetation indices (VIs); (vi) root strength index (RSI); and (vii) distribution of water-loving trees. The VAIs were used as the feature layer input of the classification process with landslide activity as the target results. The landslide activity of the study area was classified using support vector machine (SVM) approach. SVM parameter optimization was applied by using Grid Search (GS) and Genetic Algorithm (GA) techniques. The results showed that the overall accuracy of the validation dataset is between 61.4–86%, and kappa is between 0.335–0.769 for deep-seated translational landslide. SVM RBF-GS with 0.5m spatial resolution produced highest overall accuracy and kappa values. Also, the overall accuracy of the validation dataset for shallow translational is between 49.8–71.3%, and kappa is between 0.243–0.563 where SVM RBF-GS with 0.5m resolution recorded the best result. In conclusion, this study provides a novel framework in utilizing high resolution remote sensing to support labour intensive process of landslide inventory. The nature-based vegetation anomalies indicators have been proved to be reliable for landslide activity identification in Malaysia.

Evaluation on the phenotypic diversity of Calamansi (Citrus microcarpa) germplasm in Hainan island

Calamansi or Philippine lime (Citrofortunella macrocarpa) is an important crop for local economic in Hainan Island. There is no study about Calamansi germplasm evaluation and cultivar development. In this study, Calamansi data were collected from 151 of Calamansi seedling trees, and 37 phenotypic traits were analyzed to investigate their genetic diversities. The cluster analysis and principal component analysis were conducted aiming to provide a theoretical basis for the Calamansi genetic improvement. The results of the diversity analysis revealed: (1) the diversity indexes for qualitative traits were ranged from 0.46–1.39, and the traits with the highest genetic diversity level were fruit shaped and pulp colored (H′ > 1.20); and the diversity indexes for quantitative traits ranged from 0.67–2.10, with the exception of a lower in fruit juice rate (1.08) and lower in number of petals (0.67). (2) The clustering analysis of phenotypic traits have arranged the samples into 4 categories: the first group characterized by fewer flesh Segment number per fruit (SNF) and more Oil cell number (OCN); the second group had 7 samples, all characterized with larger Crown breadth (CB), higher Yield per tree (YPT), the lager leaf, the higher Ascorbic acid (AA), and less Seed number per fruit (SNPF); the third group had 25 samples characterized by smaller Tree foot diameter (TFD),smaller Fruit shape index (FSI) and higher Total soluble solids (TSS) contain; the fourth group had 87 samples, they were characterized by shorter Petiole length (PEL), larger fruit, higher Juice ratio (JR), multiple Stamen number (SN) and longer Pistil length (PIL). (3) The principal component analysis showed the values of the first 9 major components characteristic vectors were all greater than 3, the cumulative contribution rate reach 72.20%, including the traits of single fruit weight, fruit diameter, tree height, tree canopy width etc. Finally, based on the comprehensive main component value of all samples, the Calamansi individuals with higher testing scores were selected for further observation. This study concludes that Calamansi seedling populations in the Hainan Island holds great genetic diversity in varies traits, and can be useful for the Calamansi variety improvements.

Dominance of coniferous and broadleaved trees drives bacterial associations with boreal feather mosses

The composition of ecologically important moss-associated bacterial communities seems to be mainly driven by host species, but may also be shaped by environmental conditions related with tree-canopy dominance. The moss phyllosphere has been studied in coniferous forests while broadleaf forests remain understudied. To determine if host species or environmental conditions defined by tree-canopy dominance drives the bacterial diversity in the moss phyllosphere, we used 16S rRNA gene amplicon sequencing to quantify changes in bacterial communities as a function of host species (Pleurozium schreberi and Ptilium crista-castrensis) and forest type (coniferous black spruce versus deciduous broadleaf trembling aspen) in eastern Canada. Forest type, not host species, was the main factor affecting moss phyllosphere bacterial community composition, though the interaction of both variables was significant. Bacterial α-diversity was highest in spruce forests, while there was greater turnover (β-diversity) and higher γ-diversity in aspen forests. Unexpectedly, Cyanobacteria were much more relatively abundant in aspen than in spruce forests, with the bacterial family Nostocaceae (Cyanobacteria) differing the most between both forest types. Our results suggest that the increasing change in dominance from coniferous to broadleaf trees due to natural and anthropic disturbances is likely to affect the composition of moss-associated bacteria in boreal forests.

Feasibility study on hexacopter UAV based sprayer for application of environment-friendly biopesticide in guava orchard

Aim: To study the feasibility of hexacopter UAV based sprayer for application of environment-friendly biopesticide in guava orchard. Methodology: Field experiments were conducted in Punjab (India) during 2020. UAV was evaluated for spraying environment-friendly bio-pesticidein guava orchard. UAV was operated at 2.0 m height above the tree top.The water and oil sensitive papers were fixed on the outer side as well as inside of selected guava trees at four different canopies. Organic neem seed kernel based azadirachtin 0.15% EC biopesticide was used at recommended dose. After spraying, all water and oil sensitive papers were collected for further laboratory analysis. All spray quality parameters, i.e., coverage (%), droplet density (droplets cm-2), droplet size (µm) and uniformity coefficient were determined. For the efficacy of drone sprayer insects were counted before and 1, 2, 7 days after spray (DAS) and reduction in number of insects was calculated. Results: The on-flight field capacity of spraying with UAV was 3.0-3.3 ha h-1 whereas actual field capacity was found to be 2.0-2.3 ha h-1. The total mean coverage area was found in the range of 2.67-10.67%. The maximum coverage was at the top canopy (inner and outer) of tree which was significantly higher than all other observation points on the canopy. The mean droplet density was found in the range of 14.67-28.33 droplets cm-2. The highest droplet density (28.33 droplets cm-2) was found at the top outer side of the tree canopy. The volume median diameter was found in the range of 208.0-418.3 µm whereas, number median diameter was in the range of 138 to 269 µm. The percent reduction in aphid population 1, 2 and 7 days after spray (DAS) was 38.06, 68.28 and 62.69%, respectively whereas it was 47.95, 78.69 and 70.90% with knapsack sprayer. Interpretation: Hexacopter UAV sprayer is effective in terms of quality of spray and effective control of aphid population.

Changes in forest composition and associated biophysical climate feedbacks across boreal North America

Deciduous tree cover is expected to increase in North American boreal forests with climate warming and wildfire occurrence. This shift in composition can generate biophysical cooling effects via increased land surface albedo. Here we use newly derived maps of continuous tree canopy and fractional deciduous cover to assess change over recent decades. We find on average a small net decrease in deciduous fraction cover from 2000 to 2015 across boreal North America, and from 1992 to 2015 across Canada, despite extensive fire disturbance that locally increased deciduous vegetation. We further find a near-neutral net biophysical change in radiative forcing across the domain due to relatively small net changes in albedo. Thus, while there have been widespread changes in forest composition over the past several decades across the domain, the net changes in composition and associated post-fire radiative forcing have not yet induced systematic negative feedbacks to climate warming.

The Role of Trees in Winter Air Purification on Children’s Routes to School

Air pollution is now considered to be the world’s largest environmental health threat, accounting for millions of deaths globally each year. The social group that is particularly exposed to the harmful effects of air pollution is children. Their vulnerability results from higher breathing frequency and being subject to concentration peaks just above the ground. The negative effects of ambient particulate matter also depend on the time of exposure. A daily route to school can constitute an important component of children’s physical activity, but air pollution can pose a threat to their health. Numerous studies have proved that high loads of PM can be effectively reduced by vegetation. Little is known, however, on whether vegetation can also reduce PM during leaf dormancy. In this study we investigated the role of trees in air purification during the leafless period in children’s routes to selected schools located in Warsaw during winter. The results obtained show a weak impact of the tree canopy in winter.

Linking Tree Cover Change to Historical Management Practices in Urban Parks

ContextUrban parks provide critical ecological, health, and social benefits, constituting a substantial proportion of urban tree canopy (UTC) within a given city. As cities set ambitious UTC targets, it is critical to understand the social drivers of UTC changes in parks. ObjectivesWe sought to uncover the feedbacks between social processes, including historical events, and park UTC in a post-industrial city that experienced substantial population loss and urban park disinvestment. Methods Our mixed-methods approach involved quantifying spatiotemporal UTC changes and connecting those changes to historical management practices for three parks in Philadelphia, PA (US). We delineated UTC using aerial imagery between 1959 and 2018, and synthesized information from archival records and semi-structured interviews about historical management practices. ResultsWe found substantial UTC gains between 1959 and 1980, due to both: (a) budget cuts, mowing cessation, and associated unintended forest emergence; and (b) purposeful tree planting and reforestation activities. While some UTC gains were purposeful, others were unintentional and reflect successional processes on unmaintained lands. Contrary to literature suggesting that financial investment would lead to UTC gain, we saw declining UTC following an influx of new funding post-2000 due to construction and ecological restoration. ConclusionsWe found differing pathways leading to convergent outcomes of UTC gains. Across the three parks, differing historical processes and management goals for park landscapes had important ramifications for UTC. Our work suggests that landscape management could benefit from an improved understanding of how historical processes impact land cover.

Extinction risk modeling predicts range-wide differences of climate change impact on Karner blue butterfly

The Karner blue butterfly (Lycaeides melissa samuelis), an endangered species in decline due to multiple factors, including habitat loss, can be further threatened by climate change. Evaluating how climate shapes the population dynamics and distribution of the Karner blue (Kbb) is necessary for developing adaptive. Demographic models generally used for insect populations are often either density-dependent or applied to population presence-absence data in a density-independent manner. In contrast, we used scale-based, mixed density-dependent and density-independent (hereafter “endo-exogenous”) models for the Kbb, based on long-term count data of abundance during flight periods, to understand how different environmental variables, including climate, affected Kbb extinction risk through the middle of the 21st century. Our endo-exogenous models showed that density-dependent and environmental variables, including climate, topography, and tree canopy coverage, were essential drivers of Kbb population dynamics. We also found that Kbb’s response to climate differed between the species’ two annual generations and across its range: higher temperature and precipitation in summer generally benefited the second-generation populations, whereas there were uncertainties of the effects on the populations in different ecoregions during the first generation. These results imply that population-specific biotic/abiotic factors need to be incorporated into plans to manage the recovery of Kbb under climate change.