A global overview of drought and heat-induced tree mortality reveals emerging climate change risks for forests

Greenhouse gas emissions have significantly altered global climate, and will continue to do so in the future. Increases in the frequency, duration, and/or severity of drought and heat stress associated with climate change could fundamentally alter the composition, structure, and biogeography of forests in many regions. Of particular concern are potential increases in tree mortality associated with climate-induced physiological stress and interactions with other climate-mediated processes such as insect outbreaks and wildfire. Despite this risk, existing projections of tree mortality are based on models that lack functionally realistic mortality mechanisms, and there has been no attempt to track observations of climate-driven tree mortality globally. Here we present the first global assessment of recent tree mortality attributed to drought and heat stress. Although episodic mortality occurs in the absence of climate change, studies compiled here suggest that at least some of the world's forested ecosystems already may be responding to climate change and raise concern that forests may become increasingly vulnerable to higher background tree mortality rates and die-off in response to future warming and drought, even in environments that are not normally considered water-limited. This further suggests risks to ecosystem services, including the loss of sequestered forest carbon and associated atmospheric feedbacks. Our review also identifies key information gaps and scientific uncertainties that currently hinder our ability to predict tree mortality in response to climate change and emphasizes the need for a globally coordinated observation system. Overall, our review reveals the potential for amplified tree mortality due to drought and heat in forests worldwide.     

Night temperature and intercepted solar radiation additively contribute to oleic acid percentage in sunflower oil

Oil fatty acid composition of sunflower (Helianthus annuus L.) closely depends on the environmental conditions during grain filling. Temperature and solar radiation are main environmental factors driving oil chemical composition, as revealed by experiments in which the effects of these variables were investigated separately. The present work aims at investigating whether both temperature and irradiance act independently or they interact in exerting their effects on oleic acid percentage of sunflower oil. With this purpose, minimum night temperature (MNT) and intercepted solar radiation (ISR) per plant were together modified during the grain filling period of the traditional sunflower hybrid ACA 885. Two experimental approaches were performed: (a) radiation was modified in three locations at different latitudes (location × radiation experiments), (b) radiation and temperature were modified in a factorial design within one location by using field shelters (in situ temperature × radiation experiments). Regardless location or year effect, oleic acid percentage increased with ISR per plant up to a maximum value, which depended on MNT. In situ temperature × radiation experiments showed that plant heating increased oleic acid percentage under any radiation condition assayed, while plant shading produced a drop in oleic acid that was independent of MNT. Statistically significant interaction between MNT and ISR per plant was not detected. A mathematical relationship that considered that MNT and ISR per plant additively contribute to oleic acid percentage was established and verified using data from location × radiation experiments. This equation predicted well independent experimental data from in situ temperature × radiation experiments.     

Species of Botryosphaeriaceae associated on mango in Brazil

The aim of the present study was to assess diversity in the Botryosphaeriaceae on trees and fruit of mango (Mangifera indica L.) in a semi-arid region in northeastern Brazil in which most exported fruit in the country are produced. Using morphological characteristics and DNA sequence data (ITS-1, ITS-2 and 5.8S rDNA) we confirmed the presence of Lasiodiplodia theobromae in the region, and for the first time report Fusicoccum aesculi and Neofusicoccum parvum. L. theobromae was prevalent in the Assú Valley and F. aesculi and N. parvum were in the São Francisco Valley. In fruit inoculations, L. theobromae and N. parvum were more virulent than F. aesculi.     

Economic liberalization and external shocks. The hypothesis of convergence revisited for the Mexican states, 1994–2015

We study the convergence hypothesis for Mexican states during the period 1994–2015 considering the impact not only of NAFTA but also of other external shocks, such as China’s entry into the World Trade Organization (WTO) in 2001 and the global financial crisis of 2008. Using econometric panel data models with no fixed effects to avoid small sample bias, the main results indicate: (a) presence of absolute divergence, consistent with a sigma process divergence, particularly in the period after the outbreak of the global crisis of 2008; and (b) a process of weakening conditional convergence across the sub‐periods analyzed.     

Detection and characterization of Ralstonia pseudosolanacearum infecting Eucalyptus sp. in Brazil

Ralstonia solanacearum sensu lato causes bacterial wilt in many agronomic crops and tree species economically important worldwide. It is a species complex that has been divided into phylotypes and sequevars, commonly related to geographic distribution. Knowledge of the phylotype composition and genetic variability in populations of this phytopathogenic bacterium is useful for implementing effective control measures. In a survey conducted in 2019, six bacterial strains were obtained from wilted Eucalyptus urophylla trees in plantations located in the municipality of Dom Eliseu, Pará state, Brazil. Multiplex PCR based on the internal transcribed spacer (ITS) indicated that the bacterial strains belonged to two different species, namely R. pseudosolanacearum (phylotype I) and R. solanacearum (phylotype II). In a phylogenetic analysis, the nucleotide sequence of the endoglucanase (egl) gene from eucalypt strains of phylotype I clustered together with sequevar 18 sequences from GenBank. Separation of the strains into two different species was confirmed by repetitive element palindromic PCR (rep‐PCR). Pathogenicity tests demonstrated that the R. solanacearum and R. pseudosolanacearum strains recovered from E. urophylla cause disease in both tomato and eucalypt plants. Until now, only R. solanacearum (Phylotype II) has been reported causing wilt symptoms on Eucalyptus spp. in Brazil. Therefore, the presence of R. pseudosolanacearum and a need for better understanding of its genetic and aggressiveness variability as well as possible differences between the two species should be considered in breeding programmes aimed at the deployment of host resistance.     

<Emphasis Type="Italic">β</Emphasis>-Diversity and vegetation structure as influenced by slope aspect and altitude in a seasonally dry tropical landscape

Topography strongly affects the distribution of insolation in the terrain. Patterns of incoming solar radiation affect energy and water balances within a landscape, resulting in changes in vegetation attributes. Unlike other regions, in seasonally dry tropical forest areas the potential contribution of topography-related environmental heterogeneity to β-diversity is unclear. In Mt. Cerro Verde (Oaxaca), S. Mexico, we: (1) modelled potential energy income for N- and S-facing slopes based on a digital elevation model, (2) examined the response of vegetation structure to slope aspect and altitude and (3) related variations in plant diversity to topography-related heterogeneity. Vegetation survey and modelling of potential energy income (SOLEI-32 model) were based on 30 plots equally distributed among three altitudinal belts defined for each slope of the mountain; combining the three altitudinal belts and the two slopes produced six environmental groups, represented by five vegetation plots each. Potential energy income was about 20% larger on the S than on the N slope (9,735 versus 8,138 MJ/m²), but it did not vary with altitude. In addition, the temporal behaviour of potential energy income throughout the year differed greatly between slopes. Vegetation structure did not show significant changes linked to the environmental gradients analysed, but altitude and aspect did affect β-diversity. We argue that the classic model of slope aspect effect on vegetation needs reconsideration for tropical landscapes. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorised users.     

Spray and economics assessment of a UAV-based ultra-low-volume application in olive and citrus orchards

Precision Agriculture - Automation is a new frontier in specialty agriculture equipment. Specifically, unmanned aerial vehicles (UAV), machine vision and robotics will increasingly appear in...     

Nutritional Composition,Bioactive Compounds and Antioxidant Activity of Wild Edible Flowers Consumed in Semiarid Regions of Mexico

Plant Foods for Human Nutrition - In semiarid regions of Mexico, it is common to use the floristic richness of wild plants as food ingredients. Hence, flowers of Agave salmiana, Aloe vera,...     

An online operational alert system for the early detection of shrimp epidemics at the regional level based on real-time production

Diseases are among the greatest threats affecting the sustainability of shrimp aquaculture. In Ecuador, diseases of cultured shrimp have been quickly transmitted from one region to another. Therefore, an early detection system of impending epidemics could serve as an important management tool for the aquaculture sector. We developed a system for the early detection of shrimp epidemics for the largest shrimp zone of Ecuador based on production surveillance. The system, called Epidemiological Alert System and Aquaculture Management (SAEMA), uses a geographical information system (GIS) with an imaginary grid cartography (12,860 ha per grid) dividing the study area. A production and management index is calculated with the harvest data of each pond. A standardized deviation around the historical averages and an alert level is calculated per grid and month. Normal conditions of production and therefore the absence of disease are depicted in green and yellow. While, orange and red colours express a disease warning manifested through suboptimal production levels. As a result, a map of the study area with grid divisions is displayed, with a specific alert colour for each grid where information is available. SAEMA was developed as a Web application (http://www.saema.espol.edu.ec) that enables producers to record data via a worksheet format using any web browser. Instantaneously, the applications perform a calculation of the alert index and provide feedback to the alert levels displayed in an interactive map. A feedback process was initiated in May 2006 with 19 participating shrimp farms. The objective of this research is to develop a platform for an early detection of shrimp epidemics on a regional scale. The detection of an epidemic, expressed as suboptimal production in a specific region, can provide producers from other zones and government authorities to engage in time preventive and control measures in order to reduce the spread of diseases.     

Manipulating the soil microbiome to increase soil health and plant fertility

A variety of soil factors are known to increase nutrient availability and plant productivity. The most influential might be the organisms comprising the soil microbial community of the rhizosphere, which is the soil surrounding the roots of plants where complex interactions occur between the roots, soil, and microorganisms. Root exudates act as substrates and signaling molecules for microbes creating a complex and interwoven relationship between plants and the microbiome. While individual microorganisms such as endophytes, symbionts, pathogens, and plant growth promoting rhizobacteria are increasingly featured in the literature, the larger community of soil microorganisms, or soil microbiome, may have more far-reaching effects. Each microorganism functions in coordination with the overall soil microbiome to influence plant health and crop productivity. Increasing evidence indicates that plants can shape the soil microbiome through the secretion of root exudates. The molecular communication fluctuates according to the plant development stage, proximity to neighboring species, management techniques, and many other factors. This review seeks to summarize the current knowledge on this topic.