Modifying Shoot Tip Management to Reduce Cluster Compactness and Lateral Emergence in ‘Cabernet franc’ Grapevines

To manage excessive vine vigor, Vitis vinifera L. ‘Cabernet franc’ grapevines were subjected to shoot wrap, shoot tuck, and hedge (control) techniques at one of two growth stages (shoot tips at 30 cm or at 90 cm above the top catch wire) in the Finger Lakes region of New York from 2016 to 2019. Shoot tuck and shoot wrap both reduced fruit zone lateral counts, with reductions up to 33% and 56% compared with the control, respectively. Shoot wrap reduced fruit zone lateral lengths by up to 50% and cluster compactness by up to 2.4 fewer berries per centimeter rachis. Although shoot wrap improved spray penetration to the clusters by up to 28% in one year of the study, enhanced point quadrat analysis indicated that occlusion layer number was not affected by the treatments. Shoot tip management treatments did not affect yield or fruit composition consistently. Phenological timing of shoot tip management had little impact on vine growth. Although the impacts of these modified shoot tip management practices on lateral emergence and cluster morphology were generally positive, the required hand labor to apply the treatments on a large scale may discourage the use of these management practices.

Variations in the coverage of biological soil crusts along a gradient of aridity in the center-west of argentina

The biological soil crusts (biocrust) play a fundamental role in the arid and semiarid areas of South America. However, little attention has been paid to the distribution and coverage of them. In Argentina, studies about biocrust are still scarce. The goal of this contribution is to analyze the coverage of the biocrust and each of the functional component along a gradient of aridity in the center-west of Argentina. The gradient included three differentiated sites: semiarid, arid, and hyperarid sites. The coverage was recorded using the Point-quadrat method on 30 transects through a gradient consisting of three sites: semiarid, arid, and hyper-arid sites. The arid site was the system with the highest coverage of biocrust followed by the hyper-arid site. The semiarid site had the lowest values of coverage and showed significant differences among the three systems were found. Cyanobacteria’s dominate in the hyper-arid site. On the other hand, cyanobacteria and lichens were dominant in the arid site. The coverage of studied organisms showed variations in the semiarid site. These results support the idea that the coverage has a strong relationship with the features of the studied ecosystem and the environmental factors both at a mesoscale and a microscale in a determined community.

Cambios florísticos y fisonómicos de la vegetación y su relación con la capa carbonatico-cálcica, en área vitivinícola, Mendoza, Argentina.

Introducción: La provincia de Mendoza se caracteriza por un creciente desarrollo del cultivo de vid. Su expansión, ha llevado a la ocupación de áreas con presencia de una capa de carbonato de calcio, el “caliche”, planteando problemas agrícolas. Nuestro objetivo fue determinar la profundidad a la que se encuentra el “caliche” a través de la identificación de comunidades vegetales y zonificarlas para su uso con destino al cultivo de vid. M&M: Se trabajó en un terreno de 60 ha, Dpto. Tupungato. Se realizaron 27 censos fitosociológicos y 27 transectas de Point-quadrat para determinar cobertura vegetal. En cada punto de muestreo se midió la profundidad del caliche mediante la técnica de barrenado y se evaluó la altura de la vegetación dominante.Resultados: Se registraron 68 especies vegetales. La matriz dominante estuvo representada por Larrea divaricata. Se identificaron 5 UV florísticas y 5 UV fisonómicas, encontrándose una relación positiva entre ambas. La profundidad de caliche osciló entre 0-150 cm. Las UV florísticas mostraron un solapamiento en la profundidad del caliche, no así las fisonómicas. Geoffroea decorticans y Senna aphylla fueron indicadoras de la presencia de caliche. Conclusiones: El presente trabajo ofrece una alternativa de bajo costo, alto potencial y efectividad de uso, para el muestreo de profundidad de caliche.

Effects of Piliostigma reticulatum on the Vegetation Dynamic in Sudanian Zone of Burkina Faso

This study aims at identifying the effect of P. reticulatum on the vegetation regeneration dynamic in Sudanian fallows of Burkina Faso. Two fallows of about twenty years old have been considered. The point quadrat method was used for herbaceous inventory. Aboveground biomass has been estimated. Moreover, effect of P. reticulatum on the regeneration of others woody species has been studied under, at the limit and out of the shrub canopy. In north Sudanian zone, inventory recorded 39 herbaceous species of which 23 species under the canopy and 16 in open grassland, distributed in 12 families and 22 genera. In south Sudanian zone, species diversity is 41 species from which 23 under the canopy and 18 out of, spread in 16 families and 26 genera. Species higher than 80 cm have been observed only under P. reticulatum canopy in south and north Sudanian zone. In addition, no species of striga met in open sunlight has been observed under the shrub canopy. East and West directions recorded the important proportions of species with individuals belonging to the stratum superior to 100 cm (3.13 and 4.81 % in north direction, 1.47 and 1.73% in south directions).

Effect of residual leaf area index on spatial components of Tifton 85 pastures and ingestive behaviour of sheep

This study compared the effect of residual leaf area index (rLAI) on the spatial distribution of morphological components of Tifton 85 (Cynodon spp.) pastures and the ingestive behaviour of grazing sheep. Also, it was investigated whether any specific correlation could be found between pasture structural characteristics and sheep ingestive behaviour. Four rLAI treatments (0.8; 1.4; 2.0 and 2.6) with four replications were evaluated per period. Sheep grazed under rotational stocking management and they grazed for 4 days in each pasture while pasture regrowth period was determined by the 95% light interception requirement. Pasture structure was evaluated using inclined point-quadrat, LAI estimates, light interception and leaf : stem ratio. The 2.6 rLAI yielded the highest proportion of dead material in the lower canopy. In the post-grazing period the proportion of leaves increased with increasing rLAI, especially on the canopy surface during the rainy season. In the pre-grazing average pasture height ranged between 19 and 26 cm with dead material and stem observed up to the canopy surface in the dry season. The animals grazed longer on the last day (89.72%) compared with the first day (80.25%) in the dry season. However, they spent less time (11.45%) ruminating in the dry season compared with the rainy season (15.38%), regardless of the grazing day. Grazing time decreased and rumination time increased as rLAI increased. Sheep grazing time correlated negatively with pasture height, before and after grazing. The sheep tend to graze longer on Tifton 85 pastures when rLAI was lower and forage supply was possibly less as on the last grazing day and in the dry season.

Impacts of horse grazing on botanical composition and diversity in different types of heathland

Plant dynamics under horse grazing was studied in a three-year field experiment in heather-gorse shrublands in NW Spain. The experimental design consisted of three vegetation types with four replicates (paddocks): (1) heather (Ericaceae)-dominated (H), (2) gorse (Ulex gallii Planch.)-dominated (G), and (3) co-dominated by gorse and heath-grasses (GG). Each paddock (1.2 ha) was grazed from May to October by two crossbred mature mares (310 ± 52 kg bodyweight), one dry and one lactating (plus foal). Two other paddocks (one in H and one in GG) were excluded from grazing. Plant cover and height were sampled three times a year (spring, summer, and autumn) with a point-quadrat method. Floristic composition and diversity were annually sampled at 10 25-m2 quadrats per paddock. Data were subjected to mixed models for repeated-measures and redundancy analyses. Horse grazing resulted in overall increases (P < 0.001) in heather and herbaceous cover (from 13% to 27%, and from 16% to 23%, respectively), and decreases (P < 0.001) in gorse cover and height (from 35% to 17%; from 30 to 25 cm), with scarce differences among vegetation types. Floristic diversity (species richness and Shannon index) increased more over time in grazed than in ungrazed paddocks. Redundancy analyses revealed that grazing effects on plant species assemblages depended on vegetation type, and that plant communities evolved differently between grazing treatments for both abundance and frequency data. Some herbaceous species characteristic of heathlands were favoured by horse grazing. Horse grazing reduced gorse dominance in G and GG vegetation, controlling excessive accumulation of combustible material and reducing fire risk, and promoted the presence of species of conservation interest, so it offers a promising management tool for the restoration of heathlands and their biodiversity.

Top of the World Collaborations: Lessons from above Treeline

My involvement at the Niwot Ridge Long-Term Ecological Research (LTER) site began when I was an undergraduate summer research assistant, and it has extended through a postdoctoral fellowship, a tenured professorship, and now a leadership role in the program. I focus on alpine tundra plant diversity, plant–soil interactions, and how environmental changes may influence community dynamics over time and space. Cross-site synthesis work has been one of the most valuable experiences of my career, enabling me to ask more general questions and produce more influential work than I could have done with a focus at a single site. Such comparative research has allowed me to interact with a fabulous group of scientists that has strongly influenced my professional development. These scientists remain strong role models for me. My experiences in the LTER program have formed my model of education and training, emphasizing experimental and observational approaches, quantitative methods, and data management and sharing. I think it is the best way to approach the difficult and complex ecological questions facing our society today. My involvement in the LTER program started in college, when I decided to study for one semester at the University of Colorado. During that semester, I took a class from Marilyn Walker, who was part of the Niwot Ridge (NWT) LTER program. Marilyn’s class did not go to the tundra or even focus on alpine systems. However, when time came to figure out what to do over the summer, I asked her if I could be her research assistant. She gave me the chance to work at Niwot Ridge (Figure 29.1). I spent the summer before my senior year at 3,500-m elevation, recording point quadrat vegetation data in permanent plots. The snow was late to melt that year, so I spent much of June in the Institute of Alpine and Arctic Research’s loading dock, painting thick black stripes on 2.5-m long PVC poles to be used to measure snow depth. When snow melted enough to allow access on the entrance road, I went up to Niwot Ridge for the first time.

Measurement of grapevine canopy leaf area by using an ultrasonic-based method

<p style="text-align: justify;"><strong>Aim</strong>: Measurement of leaf area in grapevine has always been a critical point in researches focused on irrigation management, training systems, source-sink interrelationships and efficiency of spray application to canopies. In this work, we propose the use of ultrasonic sensors as a fast and accurate tool for the estimation of large portions of leaf canopy area.</p><p style="text-align: justify;"><strong>Methods and results</strong>: Through outputs of ultrasonic sensors installed on a tractor moving along vineyard rows, we calculated an ultrasonic-based leaf density index that we correlated with three measurements or estimates of canopy area: I) direct measurement of the area of a canopy portion (LAØ), assessed by summing the areas of all the leaves, where each single-leaf area was assessed by regressing the leaf diameter (the maximum width perpendicular to the main rip) against the related leaf area calculated on the basis of a relation between the leaf diameter and the leaf area, previously assessed through an area meter on a 20-leaf sample; II) the point quadrat output (LApq); and III) the canopy leaf area index (LAI) obtained through LAI-2000 (Li-Cor) technology. The measurements were assessed on six cultivars in three replicate rows (8-12 plants per cultivar per row) in a vineyard trained to a vertical trellis system.</p><p style="text-align: justify;"><strong>Conclusion</strong>: When we correlated the three independent control parameters with each other, we obtained highly significant correlations between LApq and LAØ, but less significant correlations between these two and LAI-2000 outputs. Also, the correlations between ultrasonic outputsoutputs and LAØ and LApq were significant, with R2 ranging between 0.84 and 0.85. On the contrary, no significant correlation was found between ultrasonic outputs and LAI-2000 outputs. These results were obtained by averaging all the values belonging to each replicated cultivar (10.5 m along the row, i.e., twelve contiguous vines); on the contrary, when the analysis was done over a shorter distance (3.5 m, i.e., four contiguous vines), the reliability of the ultrasonic-based method decreased.</p><p style="text-align: justify;"><strong>Significance and impact of the study</strong>: These results point to the ultrasonic technology as a powerful tool to estimate large-scale leaf canopy area, with potential applications in precision farming. At the moment, however, the limitation of this approach is the requirement of reference values for leaf area (e.g., assessed by point quadrat) to obtain absolute and not only relative outputs. With this application we can quantify, in a few hours, the canopy of a whole vineyard, in order to analyze different vegetation zones or to follow canopy development.</p>