Non-destructive simple model to estimate the leaf area through midvein in cultivars of Vitis vinifera

Mathematical models are indirect and non-destructive methods for estimating the leaf area (LA), an important parameter associated with canopy vigor in Vitis viniferavineyards. This work aims to adjust and test mathematical models for estimating LA using the midvein length of the Vitis vinifera cultivars conducted in horizontal and vertical training systems in the Serra Gaúcha region, Brazil. Leaves were collected in ‘Chardonnay’, ‘Cabernet Sauvignon’ vineyards conducted in trellis and lyre training systems, and in ‘Merlot’ vineyards conducted in trellis and espalier systems. Models were tested for establishing the correlations among the parameters LA and midvein length, considering the cultivar/training system and the general data set. For validation, linear regression between the observed and estimated LA was defined. The relationship between the midvein length and LA was defined by non-linear potential equations (R2aj 0.95-0.98). The performances of the specific and general models were similar regardless of the cultivar/training system. The adjusted models showed excellent results in the validation step (correlation 0.95-0.98; Wilmott index >0.97 and confidence index>0.92). It is possible to estimate the LA of Vitis vinifera Chardonnay, Cabernet Sauvignon, and Merlot cultivars using a simple non-destructive model that employs one single measurement of the leaf blade, to optimize the vegetative canopy quantification in vineyards.

Woodlice change the habitat use of spiders in a different food chain

Background In old field systems, the common woodlouse may have an indirect effect on a nursery web spider. Woodlice and nursery web spiders feed in different food chains, yet previous work demonstrated that the presence of woodlice is correlated with higher predation success by nursery web spiders upon their grasshopper prey. This finding suggested a new hypothesis which links two seemingly disparate food chains: when woodlice are present, the spider predator or the grasshopper prey changes their location in the vegetative canopy in a way that increases their spatial overlap and therefore predation rate. However, warming temperatures may complicate this phenomenon. The spider cannot tolerate thermal stress, meaning warming temperatures may cause the spider to move downwards in the vegetative canopy or otherwise alter its response to woodlice. Therefore, we would expect warming and woodlice presence to have an interactive effect on predation rate. Methods We conducted behavioral experiments in 2015, 2017, and 2018 to track habitat domains—the use of the vegetative canopy space by grasshoppers and spiders—in experimental cages. Then, we used three models of spider movement to try to explain the response of spiders to woodlice: expected net energy gain, signal detection theory, and individual-based modelling. Results Habitat domain observations revealed that spiders shift upward in the canopy when woodlice are present, but the corresponding effect on grasshopper prey survival was variable over the different years of study. Under warming conditions, spiders remained lower in the canopy regardless of the presence of woodlice, suggesting that thermal stress is more important than the effect of woodlice. Our modelling results suggest that spiders do not need to move away from woodlice to maximize net energy gain (expected net energy gain and signal detection theory models). Instead spider behavior is consistent with the null hypothesis that they move away from unsuccessful encounters with woodlice (individual-based simulation). We conclude that mapping how predator behavior changes across biotic (e.g. woodlouse presence) and abiotic conditions (e.g. temperature) may be critical to anticipate changes in ecosystem dynamics.

Designing a network of critical zone observatories to explore the living skin of the terrestrial Earth

The critical zone (CZ), the dynamic living skin of the Earth, extends from the top of the vegetative canopy through the soil and down to fresh bedrock and the bottom of the groundwater. All humans live in and depend on the CZ. This zone has three co-evolving surfaces: the top of the vegetative canopy, the ground surface, and a deep subsurface below which Earth's materials are unweathered. The network of nine CZ observatories supported by the US National Science Foundation has made advances in three broad areas of CZ research relating to the co-evolving surfaces. First, monitoring has revealed how natural and anthropogenic inputs at the vegetation canopy and ground surface cause subsurface responses in water, regolith structure, minerals, and biotic activity to considerable depths. This response, in turn, impacts aboveground biota and climate. Second, drilling and geophysical imaging now reveal how the deep subsurface of the CZ varies across landscapes, which in turn influences aboveground ecosystems. Third, several new mechanistic models now provide quantitative predictions of the spatial structure of the subsurface of the CZ.Many countries fund critical zone observatories (CZOs) to measure the fluxes of solutes, water, energy, gases, and sediments in the CZ and some relate these observations to the histories of those fluxes recorded in landforms, biota, soils, sediments, and rocks. Each US observatory has succeeded in (i) synthesizing research across disciplines into convergent approaches; (ii) providing long-term measurements to compare across sites; (iii) testing and developing models; (iv) collecting and measuring baseline data for comparison to catastrophic events; (v) stimulating new process-based hypotheses; (vi) catalyzing development of new techniques and instrumentation; (vii) informing the public about the CZ; (viii) mentoring students and teaching about emerging multidisciplinary CZ science; and (ix) discovering new insights about the CZ. Many of these activities can only be accomplished with observatories. Here we review the CZO enterprise in the United States and identify how such observatories could operate in the future as a network designed to generate critical scientific insights. Specifically, we recognize the need for the network to study network-level questions, expand the environments under investigation, accommodate both hypothesis testing and monitoring, and involve more stakeholders. We propose a driving question for future CZ science and a hubs-and-campaigns model to address that question and target the CZ as one unit. Only with such integrative efforts will we learn to steward the life-sustaining critical zone now and into the future.

Effect of shoot topping intensity on 'Cabernet Franc' grapevine maturity in high-altitude region

The objective of this work was to evaluate the chemical composition of 'Cabernet Franc' grape subjected to different levels of shoot topping. The experiment was conducted in the 2008 and 2009 vintages, and the levels of shoot topping consisted of: control, without topping; and reductions of 15, 30, and 45% in total leaf area. The effect of shoot topping intensity on the chemical composition of the 'Cabernet Franc' grape berries was observed. A reduction of 26% in the vegetative canopy through a moderate shoot topping increased the total polyphenol index and the anthocyanin content. Shoot topping is a practice that must be carried out with caution, since severe shoot topping, i.e., a reduction greater than 26% of the leaf area, may negatively impact grape quality by reducing the content of soluble solids and decreasing the total polyphenol index and the content of anthocyanins of 'Cabernet Franc' grape berries.

Tolerance and Suppression of Weeds Varies among Carrot Varieties

Slow carrot emergence and canopy development render the crop a poor competitor with weeds. In this study, the ability to suppress weeds and maintain yield in the presence of weeds was compared among nine carrot varieties that included those selected by plant breeders for rapid vegetative canopy development compared to traditional varieties. Two weed management treatments were compared: handweeding for 21 d after carrot seeding versus handweeding for the entire carrot season. In years and locations with low to moderate weed pressure, such as in the 2014 study, differences among carrot varieties in weed competitiveness or tolerance were less apparent and therefore less relevant. Maximum carrot yield loss to weed competition among varieties was 28% in 2014. Yield loss in the presence of weeds was 15% or less with six of the nine carrot varieties. However, when weed pressure was intense in the 2015 study, both carrot plant density and carrot canopy development were inversely related to weed biomass. Carrot yield loss in the presence of weeds ranged from 38 to 87%. Despite correcting seeding populations for differences in germination among carrot varieties, carrot stand establishment varied greatly and would likely affect subsequent weed control measures such as timely cultivation or herbicide application. Future research efforts are warranted that consider carrot stand establishment factors and their relationship with integrated weed management programs.

Managing fescue toxicosis through forage canopy, limestone application, and novel endophytes

Tall fescue [Lolium arundinaceum (Schreb.) Darbysh.] infected with the endophytic fungus Epichlo coenophiala [(Morgan-Jones and W. Gams) C.W. Bacon and Schardl, comb. nov.] produces ergovaline and other alkaloids responsible for fescue toxicosis, a livestock disorder. Cultivars re-infected with endophytes that do not produce toxic ergot alkaloids, referred to as "novel endophytes," have been used to alleviate the symptoms of fescue toxicosis. This research includes a series of experiments with the overall objective of identifying management practices that reduce fescue toxicosis in order to provide recommendations to Missouri farmers. The fist experiment examined the distribution of ergovaline and total ergot alkaloids throughout the vegetative canopy of tall fescue, and concluded that toxin concentrations are highest in the bottom 5 cm of the plant. The second experiment documented that applying limestone decreased ergovaline concentrations by at least 20 [mu]g kg[superscript -1] dry matter. The third experiment evaluated cattle preference among novel endophyte-infected tall fescue cultivars. This experiment concluded that one cultivar, 'BarOptima,' was grazed first and most frequently.