Stoichiometry of needle litterfall of Pinus hartwegii Lindl. in two alpine forests of central Mexico

Introduction: It is essential to have baselines on nutrient dynamics in forests, due to disturbances that climate change may cause.Objective: To quantify the annual production of needles of Pinus hartwegii Lindl. and the proportion of nutrients in the alpine forests of Jocotitlán (JO) and Tláloc (TL) mountains, Estado de México.Materials and methods: A total of 12 circular needle litter traps (30 cm diameter) were placed at ground level, in each forest, distributed in four topographically contrasting sites. For one year, 228 leaf mass measurements and 1 140 chemical determinations were made to determine needle stoichiometry. Measurements were subjected to a longitudinal analysis of variance, by testing trends over time (P < 0.05).Results and discussion: Needle production in JO were 67 % higher (11.2 Mg∙ha-1∙year-1) than in TL (6.7 Mg∙ha-1∙year-1); needle litterfall was higher during summer (June and July, months with higher precipitation). For JO, nutrient flux was 98.0, 5.2, 8.7, 24.6, and 5.6 kg∙ha-1∙year-1 for N, P, K, Ca, and Mg, respectively; for TL it was 55.3, 3.4, 7.8, 14.4, and 4.7 kg∙ha-1∙year-1 in the same order of nutrients. Nutrient concentrations were lower from March to May. Except for K, nutrient concentrations and needle production showed quadratic and cubic seasonal trends. Mg dynamics and N:Mg and N:K ratios in TL were more positive for tree growth.Conclusions: Jocotitlán and Tláloc forests produce significant needle mass (compared to other ecosystems) with high dynamic in nutrient transfers.

Does the severity of a forest fire modify the composition, diversity and structure of temperate forests in Jalisco?

Introduction: Forest fires are natural disturbances that influence structure, dynamics, performance, composition and diversity of species. Objective: To compare composition, structure and diversity of temperate forest vegetation affected by different levels of severity of a forest fire in Jalisco. Materials and methods: Composition, horizontal structure, importance value index (IVI), diameter class, diversity indexes of Shannon, Simpson, Margalef richness and Bray-Curtis similarity were evaluated in three regions (Bosque La Primavera and Sierra de Tapalpa and Sierra de Quila) of temperate forest with three levels of severity (no fire, moderate and extreme). Results: Twelve species from six families were recorded. Pinaceae and Fagaceae were the most dominant. Dominance ranged from 0.2 to 50 m2∙ha-1 in moderate and extreme severity sites. Pinus devoniana recorded the highest IVI (71 %) in Sierra de Tapalpa. The highest number of trees was recorded in diameter class ≤30 cm. Diversity and richness indices showed significant differences (P < 0.05) for Sierra de Tapalpa and Sierra de Quila and among fire levels; the highest indices were recorded in sites of moderate severity. Tree composition similarity between regions was low (<33 %). Conclusions: Moderate severity of forest fire favored composition, structure and diversity of vegetation in temperate forests of Jalisco, indicating that the level of severity influences resilience of forest ecosystem communities.

Wood anatomy of Magnolia rzedowskianaVázquez, Domínguez & Pedraza, endemic species of the Sierra Madre Oriental, Mexico

Introduction: Magnolia rzedowskianaVázquez, Domínguez & Pedraza is a tree species endemic to the cloud forest of the Sierra Madre Oriental; its scanty (distributed) and isolated populations are considered at danger of extinction.Objective: To describe the microscopic anatomical characteristics of M. rzedowskiana wood to contribute to the biological knowledge of this species.Materials and methods: Wood samples were determined by a non-destructive method, extracting two growth cores from five adult trees in each of the four sampling sites located in Chilijapa and Zotictla in Hidalgo, La Yesca in Querétaro and ejido La Trinidad in San Luis Potosí. Cores were sectioned into subsamples to elaborate fixed preparations from tangential, transversal and radial cuts. Characteristics were identified using an optical microscopy and described according to IAWA (International Association of Wood Anatomists) criteria.Results and discussion: Growth zones, diffuse porosity, solitary and multiple radial pores in intermediate arrangement between radial and tangential; scalariform perforation plate and libriform fibers; diffuse and scanty paratracheal and apotracheal axial parenchyma; biseriate rays combined with triserial, uniseriate and heterocellular rays composed of procumbent cells with a row above and below of marginal square cells with oil bodies. The wood is distinguished by mesomorphism and resistance to drought.Conclusion: The anatomical description of M. rzedowskiana is a contribution to biological knowledge. From an economic point of view, this wood has potential use to produce pulp for paper.

Water supply and water runoff quality in the sub deciduous forest of the Coast of Oaxaca, Mexico

Introduction: Land use change and waste discharge from coffee processing may be affecting quantity and quality of water supplying urban areas in the coastal region of Oaxaca.Objective: To determine the level of contamination of aquifers and estimate surface water runoff in micro-watersheds of Pluma Hidalgo and Santa María Huatulco in Oaxaca, Mexico.Materials and methods: Seven water supply points were analyzed during the rainy season of 2019. The following physicochemical parameters were determined: pH, total dissolved solids, electrical conductivity, hardness, total solids, chlorides, and chemical oxygen demand (COD). Surface runoff was estimated using the Raws and Prevert methods.Results and discussion. Water bodies are within the permissible limits for human use. The Chacalapilla spring was classified as moderately hard (85 mg CaCO3∙L-1), while the seven water bodies exceeded the permissible limit for COD (40 to 200 mg∙L-1); therefore, water is in a contaminated classification range and is not suitable for human consumption. Surface runoff values suggest a medium conservation condition of vegetation cover; areas with higher cover recorded lower runoff coefficients.Conclusions. The physicochemical parameters indicated that water from Pluma Hidalgo and Santa María Huatulco is suitable for human use, but not for drinking

Genetic parameters of a progeny trial of Pinus greggii Engelmann ex Parlatore var. australis Donahue & López in the Mixteca Alta of Oaxaca, Mexico

Introduction: The Mixteca Alta of Oaxaca has high environmental degradation. Several species have been planted to recover vegetation cover; Pinus greggii Engelmann ex Parlatore var. australis Donahue & López has grown successfully even without selected material.Objective: To determine growth performance and genetic parameters of 90 families at early ages, for use in the selection of superior trees.Materials and methods: In San Miguel Achiutla, Oaxaca, genetic variation in growth, conformation and straightness of 90 selected open-pollinated families of P. greggii var. australiswas evaluated in a progeny trial five years after planting in two different quality sites. Additive genetic variation, heritability (h2) and genetic and phenotypic correlations were calculated.Results and discussion: h2 were superior in the more fertile site. Height, whorls, straightness and volume had greater genetic control (0.09 < h2i < 0.18). h2i of stem straightness was higher when evaluated as a whole than when divided into three sections. Genetic correlations were high and positive among growth variables (rg > 0.81; diameter vs. volume = 0.99) and low to moderate for the rest. Volume had a higher genetic correlation with other traits and higher genetic variation and heritability, so it could be used as a selection criterion for breeding cycle. Some genetic correlations differed contrastingly between sites in equal pairs of variables.Conclusion: Differences between families and heritability will allow the identification of superior individuals for germplasm sources for regional use.

Type, effects and cause of injuries suffered by workers in the sawmill industry of El Salto, Durango, Mexico

Introduction: Sawmill work is a dangerous occupation because it involves handling materials and equipment that exposes workers to many risks that can affect their health and safety.Objective: To identify injuries, parts of the body affected and agents that cause accidents in sawmill workers in the region of El Salto, Durango.Materials and methods:A structured survey was applied to 300 workers in 26 sawmills and pallet mills to determine typology, damages and cause of injuries suffered in the last five years.Results and discussion: In the sawmills of El Salto, the most important positions are occupied by people of older age and work experience, regardless of their level of schooling; they have suffered one to five accidents in the last five years and only 32 % have received occupational safety training. The most frequent injuries were caused by hits and crushing body parts of assistants (57 %), open wounds in operators (16 %) and sprains (15 %). The mechanisms causing these injuries were getting stuck by moving objects (30 %), hitting against moving objects (23.3 %), falling objects (14.3 %) and false moves (13.7 %). Fingers were the most affected (35 %) due to a hit and by getting stuck. Conclusions: Safety training is limited, leading to 95 % of workers with injuries with different degrees of severity. It is necessary to implement actions to reduce the risk of accidents and injuries.

Fertilization of two genetic groups of Pinus patula Schiede ex Schltdl. & Cham. in a four-year progeny trial

Introduction: Genetic improvement and nutritional management are used to increase productive capacity. Objective: To analyze the effect of traditional and controlled-release fertilizers, as well as the way to define the doses (technically or empirically), on growth of 20 tree families of Pinus patulaSchiede ex Schltdl. & Cham. Materials and methods: Four fertilization treatments were applied: 1) control; 2) “technical”, based on foliar analysis; 3) controlled release (18-6-12 + 2CaO + 3.5 Mg + 2.1 Si + microelements); and 4) mixture of agricultural fertilizers in nutrient concentrations similar to the controlled-release treatment. Height, diameter, biomass index, number of whorls, leaf mass, and growth initiation and cessation were evaluated in a group of 10 superior and 10 inferior three-year old families in Chignahuapan, Puebla. Data were analyzed with the MIXED procedure of SAS. Results and discussion: Trees showed no significant differences in growth, biomass production and growth initiation by fertilization effect, but showed significant differences by genetic quality (P ≤ 0.05). The genotype*fertilization interaction was significant; after one year of controlled-release fertilizer application, inferior genotypes had the highest values of relative rates of biomass production, diameter at root collar and height. Conclusions: Controlled-release fertilizers at appropriate doses and environmental conditions are a viable option to promote growth of young P. patula trees in the field.

Antioxidant phytochemicals and modulation of oxidative stress from infusions and ultrasound-assisted extractions of Coffea leaves

Introduction: Beyond the commercial value of coffee grains there is recent interest for the non-timber benefit and traditional medicinal properties of the Coffea tree leaves.Objective: To determine the phytochemical composition, antioxidant properties and inhibition of oxidative stress by extracts from Coffea leaves obtained by ultrasound assistance as an opportunity for production of plant bioactives. Material and methods: The phytochemical composition of ten extracts of Coffea arabica L. leaves cv. Catimor 5000 was evaluated in their phenolic and methylxanthines contents as well their antioxidant activity in vitro through nitric oxide (NO), absorbance capacity of oxygen radicals (ORAC), ferric reducing antioxidant power (FRAP), and radical ABTS (2,2'-azino-bis [3-ethylbenzothiazoline-6-sulfonic acid]) assays, and their effect on inhibition of oxidative stress induced by hydrogen peroxide in human colon adenocarcinoma cells (HT-29). Extracts were obtained by ultrasound assistance under different conditions (wave amplitude, solvent ratio, and extraction time). Results and discussion: The higher phenolics and caffeine contents, as well the greater oxidative stress inhibition response in the HT-29 model, ORAC and NO assays were obtained at 60/40 water/methanol, 40 % amplitude and 6 min of extraction time. In this work, identification of two flavanones have been reported for the first time in Coffea leaves: neohesperidin and naringenin. Regarding phenolic acids, it was detected and identified a group of hydroxybenzoic acids not previously reported in coffee leaves, such as vanillic, shikimic, syringic, and ellagic acids, along with 2,4,6 trihydroxybenzaldehyde and 2,3 dihydroxybenzoic acid.Conclusion: The novel phytochemical composition of bioactive extracts from Coffee leaves by ultrasound assistance is significant, representing a potential source of food nutraceuticals.

Yield and vivipary of pecan nut (Carya illinoinensis[Wangenh.] K. Koch) in relation to soil moisture

Introduction: Viviparity in pecan nut (Carya illinoinensis [Wangenh.] K. Koch) has increased considerably. This genetic-environmental phenomenon can be controlled with soil moisture management and other quality variables.Objective: To determine the effect of soil moisture content on yield, nut size, kernel percentage and germinated nut on the tree.Materials and methods: Forty-year-old pecan nut trees were irrigated by 40 emitters with an output of 3.2 L∙h-1. From the phenological stage of shell hardening, irrigation time was 4, 6 and 8 h, corresponding to moisture levels of 0.257, 0.327 and 0.380 m3 of water per m3 of soil, at depths of 40 to 80 cm. Yield per tree, germinated nut percentage, fruit size and kernel percentage were evaluated during the production cycles of 2016 and 2017 production cycles.Results and discussion: During the two production cycles, when soil moisture level increased from 0.257 to 0.380 m3∙m-3, nut yield per tree, fruit length and diameter, and kernel percentage increased on average 23.8 %, 25.3 and 10 %, and 1.8 %, respectively; however, vivipary increased 11.2 %, which was reflected in the decrease of commercial pecan nut percentage. Treatments 0.327 and 0.380 m3∙m-3 had a similar effect (P > 0.05) on these variables.Conclusions: The lower moisture level (0.257 m3∙m-3), starting at the kernel filling stage, decreased vivipary and increased commercial kernel percentage.

Risk of infestations by Dendroctonus mexicanus Hopkins and Dendroctonus frontalis Zimmermann bark beetles in forests of Michoacán

Introduction: Severe Dendroctonus spp. infestations are reported in North and Central America. Dendroctonus mexicanus Hopkins and Dendroctonus frontalis Zimmermann are recognized as forest pests and are common in the state of Michoacán, Mexico.Objective: To model current and future (2015-2039) spatial distribution of risk D. mexicanus and D. frontalis infestation in forests of Michoacán, Mexico.Materials and methods: Multicriteria evaluation techniques, including the analytic hierarchy process and fuzzy membership functions, were combined with climate and biophysical variables to obtain forest infestation risk maps for D. mexicanus and D. frontalis under current and future climate scenarios.Results and discussion: Climate, fire, tree density and topography were identified as relevant criteria influencing bark beetle outbreaks. The maximum risk value estimated for D. mexicanus was 0.78 and 0.83 for the current and future scenarios, respectively; for D. frontalis these values correspond to 0.84 and 0.85, respectively. In terms of area, high risk of infestation by D. mexicanus increased from 3.9 % (current scenario) to 5.0 % (future scenario); for D. frontalis it decreased from 10.8 % to 9.6 %. The very high-risk value remained constant (0.35 %) for both species and scenarios.Conclusions: Forests of the Transversal Volcanic Belt (in the northeastern part of Michoacán) have the highest risk of bark beetle infestation in the two modeled scenarios.