Impacts of thinning on structure,growth and risk of crown fire in a Pinus sylvestris L. plantation in northern Spain

We studied the combined effects of thinning on stand structure, growth, and fire risk for a Scots pine thinning trial in northern Spain 4 years following treatment. The thinning treatments were: no thinning, heavy thinning (32–46% of basal area removed) and very heavy thinning (51–57% of basal area removed). Thinning was achieved via a combination of systematic and selective methods by removing every seventh row of trees and then by cutting suppressed and subdominant trees in the remaining rows (i.e., thinning from below). Four years after thinning, mean values and probability density distributions of stand structural indices showed that the heavier the thinning, the stronger the tendency towards random tree spatial positions. Height and diameter differentiation were initially low for these plantations and decreased after the 4-year period in both control and thinned plots. Mark variograms indicated low spatial autocorrelation in tree diameters at short distances. Diameter increment was significantly correlated with the inter-tree competition indices, and also with the mean directional stand structural index. Two mixed models were proposed for estimating diameter increment using a spatial index based on basal area of larger trees (BALMOD) in one model versus spatial competition index by Bella in the other model. As well, a model to estimate canopy bulk density (CBD) was developed, as this variable is important for fire risk assessment. Both heavy and very heavy thinning resulted in a decrease of crown fire risk over no thinning, because of the reduction in CBD. However, thinning had no effect on the height to crown base and thus on the flame length for torching. Overall, although thinning did not increase size differentiation between trees in the short term, the increase in diameter increment following thinning and the reduction of crown fire risks support the use of thinning. Also, thinning is a necessary first step towards converting Scots pine plantations to more natural mixed broadleaved woodlands. In particular, the very heavy thinning treatment could be considered a first step towards conversion of overstocked stands.     

Loblolly pine growth and soil nutrient stocks eight years after forest slash incorporation

Incorporation of forest slash during stand establishment is proposed as a means of increasing soil carbon and nutrient stocks. If effective, the increased soil carbon and nutrient status may result in increased aboveground tree growth. Eight years after study installation, the impact of forest slash incorporation into the soil on soil carbon and nutrient stocks, foliar nutrients and loblolly pine growth are examined on mineral and organic sites on the North Carolina Lower Coastal Plain. Treatments include leaving forest slash on the surface and flat planting (control); V-shear and bedding (conventional), mulch forest slash followed by bedding (strip mulch) and mulch forest slash and till into the soil followed by bedding (strip mulch till). After eight years, mulching and/or tillage did not have a significant impact (p > 0.05) on soil bulk density or soil chemical properties (pH, cation exchange capacity, soil nutrients). Additionally, neither tree foliar nutrients nor stand volume were significantly impacted. However, significant effects were observed for soil phosphorus contents and stand volume between the control plots and the other treatment plots. For example, the mean stand volumes on the mineral site were 24.49 ± 1.28, 38.16 ± 2.90, 44.59 ± 3.07 and 46.96 ± 2.74 m³ ha⁻¹ for the control, conventional, strip mulch and strip mulch till plots. These observations are more likely due to the effect of bedding rather than mulching or tillage of the forest slash. These results are consistent for the mineral and the organic sites. Considering the greater expense to install the mulch and tillage treatments, the lack of a treatment effect on soil carbon and nutrient stocks and tree growth does not justify these treatments on these sites.     

Comparative efficiency of chemical compounds for in vitro and in vivo activity against Clavibacter michiganensis subsp. michiganensis, the causal agent of tomato bacterial canker

Bacterial canker of tomato caused by Clavibacter michiganensis subsp. michiganensis produces considerable economic losses in many countries because effective control measures are lacking. The extent to which bactericides control this disease effectively is low and has not yet been well documented for Southern European conditions. In this study the bactericidal effect of several products on this pathogen was assessed in vitro and in vivo in tomato plants under greenhouse conditions. Seven antibacterial substances (bronopol, copper sulphate, kasugamycin, oxolinic acid, oxytetracycline, streptomycin and 8-hydroxy-quinoline), three commercial formulates (Antibak RZ, an oligoelements mixture containing copper plus zinc; Orthopol, a potassium soap; and Param, a resistance inductor) and combinations thereof were tested. In vitro assessment showed that minimal inhibitory concentration (MIC) of antibacterial substances was between 4–8 μg ml⁻¹, except for copper sulphate with a MIC value of 150 μg ml⁻¹ and kasugamycin, which was not active at 500 μg ml⁻¹. MIC values of commercial formulates ranged between 5 and 40 μl ml⁻¹. Furthermore, combinations of 8-hydroxy-quinoline+copper sulphate, 8-hydroxy-quinoline+Antibak RZ, streptomycin+Antibak RZ and streptomycin+Orthopol showed a synergistic effect at sub-inhibitory concentrations. Treatments containing copper sulphate greatly reduced disease symptoms on plants sprayed with the bacteria, whereas streptomycin was less effective. In two independent trials, the percentage of leaves showing symptoms was significantly lower (2.4% and 11.9%) after treatment with copper sulphate combined with 8-hydroxy-quinoline at half-dose, than in inoculated controls (75.1% and 59.6%). These results were better than copper sulphate alone. However, plants inoculated by pricking rapidly developed systemic infection, which no product managed to control significantly, although several treatments did reduce symptoms. We conclude that copper sulphate combined with 8-hydroxy-quinoline may be useful in controlling external symptoms of this disease in greenhouses, and is environmentally friendly, reducing the amount of copper applied to crops.     

Dry and Rainy Seasons Significantly Alter the Gut Microbiome Composition and Reveal a Key Enterococcus sp. (Lactobacillales: Enterococcaceae) Core Component in Spodoptera frugiperda (Lepidoptera: Noctuidae) Corn Strain From Northwestern Colombia

Spodoptera frugiperda is a polyphagous pest of several crops of economic importance. Nowadays, the insect is broadly distributed in America and, recently, in Africa, Asia, and Australia. The species has diverged into corn and rice strains. The role of the gut microbiota in insect physiology is relevant due to its participation in crucial functions. However, knowledge of seasonal variations that alter the gut microbiome in pests is limited. Gut microbiome composition between the dry and rainy seasons was analyzed with cultured and uncultured approaches in S. frugiperda corn strain larvae collected at Northwest Colombia, as seasonal microbiome changes might fluctuate due to environmental changes. On the basis of culture-dependent methods, results show well-defined microbiota with bacterial isolates belonging to Enterococcus, Klebsiella (Enterobacteriales: Enterobacteriaceae), Enterobacter (Enterobacterales: Enterobacteriaceae), and Bacillus (Bacillales: Bacillaceae) genera. The community composition displayed a low bacterial diversity across all samples. The core community detected with uncultured methods was composed of Enterococcus, Erysipelatoclostridium (Erysipelotrichales: Erysipelotrichaceae), Rasltonia (Burkholderiales: Burkholderiaceae), and Rhizobium (Hyphomicrobiales: Rhizobiaceae) genera, and Enterobacteriaceae family members. Significant differences in microbiome diversity were observed between the two seasons. The relative abundance of Erysipelatoclostridium was high in the dry season, while in the phylotype ZOR0006 (Erysipelotrichales: Erysipelotrichaceae) and Tyzzerella (Lachnospirales: Lachnospiraceae) genus, the relative abundance was high in the rainy season. The overall low gut bacterial diversity observed in the S. frugiperda corn strain suggests a strong presence of antagonist activity as a selection factor possibly arising from the host, the dominant bacterial types, or the material ingested. Targeting the stability and predominance of this core microbiome could be an additional alternative to pest control strategies, particularly in this moth.     

Pigmentation,carotenoids, lipid peroxides and lipid composition of red porgy (Pagrus pagrus) skin reared under open‐cage conditions

Pigmentation capability of red porgy (Pagrus pagrus) skin reared under open sea‐cage conditions and fed an astaxanthin‐enriched diet was studied. Skin lipid peroxide levels and lipid composition were also evaluated to establish the antioxidant role of astaxanthin under these sunlight‐exposure conditions. Fish placed either in an offshore sea cage system (SC) or in an inland tank facility (T) housed inside a ‘shade‐house’ enclosure were fed a commercial diet supplemented with 22 mg kg^?1 astaxanthin. No differences in growth or survival were found. Both groups displayed a red skin, but SC fish presented a darker pigmentation, which externally reflected the higher deposition of melanin, astaxanthin and tunaxanthin found in its skin. The lower level of lipid peroxides found in SC fish might be related with the higher level of astaxanthin mentioned above. Nevertheless, lipid and fatty acid profiles did not show significant differences between groups. Our results indicate that sustainable production of red porgy with a natural red hue is possible on the basis of proper adjustment of two factors illumination and dietary astaxanthin.     

Effect of pressure and pH in ammonium retention for nanofiltration and reverse osmosis membranes to be used in recirculation aquaculture systems (RAS)

Recirculation systems are becoming widely used in the aquaculture industry, where ammonium removal results are crucial for a proper performance considering its high toxicity on fish. The objective of this study was to assess the ammonium retention, when the transmembrane pressure (TMP) in nanofiltration (NF) and reverse osmosis (RO) membranes are changed. Two pH levels were tested: pH 5, where ammonium is as NH⁴⁺, and pH 7 which is an average of the most common range in aquaculture (pH 6-8). In this study a model solution of ammonium-water and commercial membranes of polyamide supplied by Alfa Laval (DSSHR98PP) and Dow (NF90, NF200 and NF270) were used, with a membrane area of 0.01018 m². A critical TMP was determined, where the repulsive electrochemical forces at the active layer were exceeded by the transmembrane pressure, causing an irreversible decrease of the retention values. The maximum TMP values for NF and RO membranes were 16 bar and 24.5 bar, respectively. Ammonium retention at pH 7 was higher than pH 5 for all assessed membranes before the critical TMP was reached, with average values of 100, 99.7, 98.4 and 87.5% for membranes NF90, DSSHR98PP, NF200 and NF270, respectively. It may be concluded the ammonium retention mechanism in the studied membranes basically corresponds to an electrochemical mechanism, where pH and critical TMP influence the retention values of ammonium.     

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.     

Post-emergence application of herbicides and growth regulators on soybean growth and agronomic performance

Journal of Crop Science and Biotechnology - Plant lodging is among the factors that limit the productive potential of the soybean crop. Growth regulators or even herbicides may be used in pre- and...     

Haemorrhagic septicaemia in the hybrid surubim (Pseudoplatystoma corruscans×Pseudoplatystoma fasciatum) caused by Aeromonas hydrophila

Intensive culture of the hybrid surubim (Pseudoplatystoma corruscans × Pseudoplatystoma fasciatum) in Brazil is responsible for the occurrence of diseases and consequent economic losses. However, the causative agents are not well known. The objective of this study was to isolate and to characterize the pathogenic agent responsible for mortalities in cultured surubim and to demonstrate its virulence. Ten fish from a fish farm located in the Mato Grosso do Sul State (Brazil) were collected and 14 haemolytic bacteria characterized as Aeromonas hydrophila were isolated from the kidneys (eight) and brain (six). As an experimental challenge, fish weighing 98.1±23.6 g were injected with 1 mL of saline solution and 2 × 10², 2 × 10⁴, 2 × 10⁶ and 2 × 10⁸ CFU A. hydrophila mL^?1. Fish infected with 2 × 10⁸ CFU showed increased external and internal symptoms and mortality of 50±12.5% after 96 h. Increased A. hydrophila concentration was responsible for a decrease in haematocrit percentage and erythrocyte number, lymphocytes and eosinophils, as well as an increase in monocytes, neutrophils, serum agglutination titre and serum antimicrobial activity. It was concluded that A. hydrophila was responsible for characteristic symptoms of bacterial haemorrhagic septicaemia as well as important haematological and immunological alterations, which led to surubim mortality.     

Nitrogen Fertilizers and NH3 Volatilization: Effect of Temperature and Soil Moisture

ABSTRACT

The volatilization of ammonia is the main reaction that decreases the efficiency of nitrogen fertilization and in order to reduce losses. new technologies such as addition of N-n-butyltriamide thiophosphate (NBPT) to the conventional urea granule (UNBPT) or the covering with polymer and sulfur (UPS) have been developed with the aim to optimize nitrogen fertilization. This work aimed to evaluate the volatilization of ammonia (NH₃) in conventional urea (CU) and fertilizers with associated technology under: (a) three temperature conditions (b) and three soil moisture management. The fertilizer CU presented the highest losses by volatilization of 25.93 mg dm^?3 while fertilizers with associated technology registered 23.93 mg dm^?3 and 8.26 mg dm^?3 for UNBPT and UPS. respectively. The highest volatilization of NH₃ was registered at 45°C for all fertilizers. Fertilizers with associated technology extended the N-release time. delaying the volatilization peak up to the 6^th day or even promoted the gradual release of fertilizer in the soil. such as UPS. The UNBPT showed the lowest volatilization values in the 1^st water application. while the CU had lower volatilization values at 25°C (14.48 mg dm^?3 NH₃) and 35°C (16.99 mg dm^?3 NH₃) when the matric potential was increased from ?100 to ?50 kPa in the 1^st application of water. The UPS did not differ from the volatilization values for the three times of water application.