Woody Crown Research Articles

Why not be random to build a woody crown network?

Why not be random to build a woody crown network?

Reemergence of Cylindrocladium Crown Rot of Roses in Florida

On April 2017, four out of 10,000 Double Knock Out Red roses were observed presenting partially wilted and chlorotic foliage in a commercial nursery in Gadsden Co., Florida. Closer examination of the plant crown revealed brown discoloration of the woody tissue. Under high temperature (85°F) and humidity (70%), shoots progressively turned chlorotic and necrotic, leading to plant death in 4 months. A rapid-growing fungus presenting orange-brown mycelium and abundant cylindrical spores was isolated from infected woody crown tissue. BLAST analysis of the resulting sequence (GenBank no. MT019606) of this pathogen had 100% identity to Calonectria cylindrospora β-tubulin gene (GenBank no. FJ918509.1). Koch’s postulates were conducted on healthy Double Knock Out roses. Two weeks after inoculation, shoots of inoculated plants turned progressively chlorotic and then necrotic, leading to plant death in 2 months. The same pathogen was reisolated from infected plant parts, which sequence also had 100% identity to C. cylindrospora β-tubulin gene (GenBank no. FJ918509.1). This pathogen is the same as one of three isolated from crown rot of roses back in 1994 and identified as Cylindrocladium scoparium (teleomorph: C. cylindrospora [Ellis & Everh.]). In this new occurrence, all infected plants were removed from the nursery, and no further infections were detected. This finding is important for commercial growers to be aware of the potential presence of this pathogen in their nurseries. Knowing the symptoms will help them recognize the disease and take action to prevent spread of the disease.

A network model for determining decomposition, topology, and properties of the woody crown

The acquisition of resources and airspace of woody crown occur by way of axes supporting annexes. Regardless of age, size, or branching system (monopodial or sympodial), the woody crown shows branched leafy axes implementing an aerial network. We propose here to represent the woody crown through a network comprised of two components, the segments of woody axes named connectors (CO) delimited by nodes (NO) as the branching regions. CO may link NO of different categories (regular, initial, final, and emission) as defined by the relative position of the NO in a crown and how many CO the NO has. The woody crown network (WCN) is similar to a random network with the probability of NO having some CO following an exponential decay. The absence of loops and real hubs weakened the robustness of WCN against failure or attacks on NO. The quantities of NO and CO and the proportions between them were the features of decomposition, and the distances measured in some CO between types of NO captured the topological characteristics of WCN. By combining decomposition and topology, we disclosed some properties of WCN, such as navigability, vulnerability, symmetry, and complexity. Navigability and complexity increased, while vulnerability and symmetry decreased exponentially as the size (ΣNO) of WCN enlarged. The behavior of properties as a function of ΣNO exposed some limits to mitigate the inherent hydraulic resistance during WCN development. Decomposition, topology, and properties of WCN in trees of Cerrado vegetation were interrelated to other crown traits revealing the strategies for acquiring airspace.

Assessment of crown woody biomass in Eucalyptus grandis and E. globulus plantations

Young trees were harvested to explore non-destructive methodologies to estimate live branch dry weights in young fast-growing Eucalyptus species under different spacing and fertilizer treatments. Branch growth can vary with silvicultural management such as spacing, fertilizing and thinning, and over relatively short periods in response to environmental conditions. Many published regressions based on standard measurements of height and diameter are site, age and treatment specific. The aim of this study was to improve our capacity to predict woody crown dry weight, based on stem measurements, and to minimize (or eliminate) treatment effects on the resulting model. In young trees, branches are temporary support structures for foliage and are often discarded as the base of the green crown rises. As temporary structures they represent an investment of biomass and nutrient elements, and are subject to selection pressures to maximize the return on investment by the tree. Trees were harvested from existing plantation experiments located in south-eastern Queensland for E. grandis W. Hill ex Maiden (ranging from 0.28 to 15.85 m in height, to 5 years old) and south-western Australia for E. globulus Labill. (0.10–34.4 m in height, to 10.2 years) in order to examine the impact of spacing, nitrogen and phosphorus fertilization on early growth. Relationships to estimate crown woody biomass from non-destructive measurements were developed, and these relationships tended to have different slopes and intercepts for trees with predominantly juvenile foliage and those with intermediate or adult foliage. Dry weight of whole-crown live branch wood (Wbranch) was related to heights and/or diameter at breast height (DBH), but the regressions parameters were different, depending on treatment. The relationships became more generic (i.e. less dependent on treatment effects) between Wbranch and stem sectional area at the height of the base of the green crown (SACB), consistent with the pipe model theory (R2 > 0.91 for the two species for trees with intermediate/adult leaves). However, Wbranch was more closely related again to the stem volume above the base of the green crown and treatment effects were not significant (VCon,gc, R2 > 0.93). Branches exit the stem below the green crown, and for E. grandis the best relationship was on stem volume above the lowest live branch (VCon,llb, R2 0.94). Limited sampling from four other species with similar or contrasting crown characteristics indicated that the relationship could be applied quite generally. Individual E. grandis branch woody dry weight was closely related to the conical volume of the main (first order) branch (Vcon,br, R2 0.98). The whole crown equivalent, branch woody dry weight plus stem dry weight above the lowest live branch, was also closely related to the stem volume within the woody crown (VCon,llb, R2 0.97–0.99). While the slope of this relationship was still significantly different between trees with juvenile and intermediate/adult foliage, it had a similar form, suggesting that trees with juvenile foliage allocated a different proportion of their woody biomass within the crown to branches than older trees.

Nutrient Management Practices in Perennial Strawberry are Informed by Understanding the Relationships among Carbohydrate Status, Nitrogen Availability, and Soil Composition

Strawberry (Fragaria ×ananassa) is a perennial plant with a compressed woody crown that responds to the environment in a similar way as other temperate fruit crops. Nutrient management practices are also similar, with a few exceptions. Levels of preplant amendments are determined based on soil test results, and are used to increase nutrient availability and modify pH as needed. Once plants are established, soil tests, coupled with foliar tissue analysis and observations of plant growth, are the best indicators of plant nutrient status and limitations. Drip irrigation is more efficient than granular applications for supplying soluble nutrients such as nitrogen (N). While most temperate fruit crops respond well to N in spring when growth resumes after winter, applications of spring N in strawberry can cause excessive vegetative growth, reduce fruit quality, and have only a marginal impact on yield. N is most efficiently taken up by plants when conditions favor root growth, and N applied in summer or fall is more effective at increasing yield the following spring, assuming that the carbohydrate status of the plant is good. However, if carbohydrate status is poor, supplemental N late in the season can reduce yield by requiring additional carbon (C) for N uptake. Many questions remain to better understand how to manage nutrients optimally in perennial strawberry.

Effect of photoscale, interpreter bias and land type on woody crown-cover estimates from aerial photography

Woody vegetation cover interpreted from aerial photography requires assessment against field data as the signature of woody vegetation cover may differ between photoscales, vegetation types and photo-interpreters. Measurements of aerial woody cover taken from aerial photography of four different photoscales were compared with a field dataset from Eucalyptus- and Acacia-dominated landscapes of semi-arid Queensland. Two interpreters employed a method that utilises a stereoscope and sample-point graticule for manual quantified measurements of aerial woody cover. Both interpreters generated highly significant models accounting for 77 and 78% of deviance. Photoscale appears to have a consistent effect whereby the signature of woody cover increases as the photoscale decreases from 1 : 25 000 to 1 : 80 000, although the magnitude of this effect was different between interpreters. The results suggest no substantial differences in the shape of models predicting crown cover between Acacia- and Eucalyptus-dominated land types, although the precision of the models was greater for the Acacia (90–91% of residual deviance) than for the Eucalyptus (50–56% of residual deviance) land type. The reduced accuracy in the Eucalyptus land type probably reflects the relatively diffuse crowns of the dominant trees. The models generated for this dataset are within the range of those from other calibration studies employing photography of a range of scales and methodologies. The effect of photoscale is verified between the available studies, but there may also be variations arising from methodological differences or image properties. The present study highlights the influence of photoscale and interpreter bias for assessing woody crown cover from aerial photography. Studies that employ aerial photography should carefully consider potential biases and cater for them by calibrating assessments with field measurements.

Two-phase sampling of woody and herbaceous plant communities using large-scale aerial photographs

A two-phase sample design employing large-scale aerial photographs was used to quantify early successional woody and herbaceous plant community structures. Two conventional 35-mm cameras were mounted on a boom and suspended from a helium-filled blimp to obtain low-cost 1:366 scale stereo photographs (1:80 scale prints) of seven experimental vegetation complexes. Estimates of woody crown volume index and herbaceous percent cover were generated for 5 × 5 m plots by calibrating photo measurements to a limited ground-truth sample. The method offered significant increases in estimation precision (>35%) over ground sampling alone, as well as attractive cost advantages (0 to 40%). The highest levels of precision were obtained by measuring entire plots on the photographs. This procedure added approximately 10% to the cost of photo evaluations but resulted in estimates with standard errors that were, on average, 78% smaller than those of ground samples. Simulation trials suggested that more than nine ground-truth sample units per vegetation community type provided only marginal increases in estimation precision. If individual species or species groups of interest are well represented in sample areas, large-scale photographs, employed in a two-phase sample design, can be an effective tool for quantifying and monitoring vegetation community structures in silvicultural and related field studies.

Response of woody eastern Canadian forest weeds to fall foliar treatments of glyphosate and triclopyr herbicides

Second-season post-treatment efficacy data are presented for a New Brunswick field study comparing three formulations of glyphosate (VISION®, MON14420, and TOUCHDOWN®) and a single formulation of triclopyr (RELEASE®). Five rates of each herbicide were broadcast applied to a 2-year-old clearcut in early September. Two growing seasons after treatment, percent control values (based on total woody crown area) ranged from 21% at glyphosate rates < 0.25 × label maximum to more than 80% at rates ≥ 0.75 × label maximum. Coefficients of variation for percent control values decreased from 104% at the lower glyphosate rates to 9% at the higher rates. Total woody control provided by triclopyr was generally equivalent to that of glyphosate at rates < 0.5 × label maximum. Beyond this rate, percent control values for triclopyr averaged only 59% and coefficients of variation remained high (40%). At the individual-species level, the three glyphosate formulations provided greater crown volume reduction than triclopyr for white ash (Fraxinusamericana L.), beech (Fagusgrandifolia Ehrh.), hazel (Coryluscornuta Marsh.), and sugar maple (Acersaccharum Marsh.). Control of mountain maple (Acerspicatum Lam.) by TOUCHDOWN® was found to be slightly inferior to that of the other two glyphosate formulations. Control of elderberry (Sambucuspubens Michx.) by MON14420 was inferior to that of the other three herbicides. Nonlinear regression curves relating second-season control and herbicide dose are presented as a guide for silvicultural use.

An Anatomical Study of Melampodium leucanthum, a Drouth Resistant Plant

L. D. VOLLE and W. A. HETZER University of Kansas, Lawrence One of the conspicuous drouth resistant plants found in the high plains and prairies of the southwestern fourth of Kansas and southwestern United States is Melampadiumleucanthum T. and G. It is an herbaceous perennial, with many slender stems rising from 6 to 12 inches from the woody crown, above a strong taproot. The remarkable drouth resistant properties of this plant made it seem worth while to investigate the anatomical structure.1