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Background: Due to causes such as small-scale earthquakes or the increasing amount of heavy rainfall extreme events, many slopes are potentially unstable. Soil bioengineering is an effective tool for treatment of a variety of unstable and/ or eroding sites. Question and hypothesis: Maximum force to breakage of the roots is influenced by diameter. Tensile strength and modulus of elasticity of roots is different between species of the two different ecosystems: Tamaulipan thornscrub and Pine-oak forest. Studied Species: Site 1: Acacia berlandieri, Cordia boissieri, Acacia rigidula, Havardia pallens, and Acacia farnesiana ; Site 2: Quercus rysophylla, Pinus pseudostrobus, Quercus canbyi, Quercus polymorpha, and Arbutus xalapensis . Study area and dates: Tamaulipan thornscrub in Northeastern Mexico (Linares, Nuevo León), from May to July 2016; and Pine-Oak forest in Sierra Madre Oriental, Iturbide, Nuevo Leon, from September to October 2016. Methods: The species considered were selected based on their native characteristics (natural distribution, abundance in the area and widespread existence on slopes). The tests were conducted with the Universal Testing Machine Shimadzu type SLFL-100KN. Results: The relationships between tensile strength (Ts) and diameters of the studied species, and root diameters and modulus of elasticity (Eroot) were negative. The minimum and maximum values of tensile strength varied from 1.86 N / mm2 in C. boissieri to 44.65 N/mm2 in A. rigidula . Conclusions: Acacia berlandieri showed the highest tensile strength among all species of the two ecosystems, in the diametric group I (0.1 to 2.9 mm).

In September 2007, rhizomorphs with morphological characteristics of Armillaria were collected from woody hosts in forests of Mexico State, Veracruz, and Oaxaca, Mexico. Based on pairing tests, isolates were assigned to five somatically compatible genets or clones (MEX7R, MEX11R, MEX23R, MEX28R, and MEX30R). These genets were all identified as Armillaria gallica based on somatic pairing tests against known tester isolates and nucleotide sequences of the translation elongation factor 1α (tef-1α; GenBank Accession Nos. KF156772 to 76). Sequences of tef-1α for all genets showed a max identity of 97 to 99% to A. gallica (ST23, JF313125) (3,4). However, A. gallica comprises a genetically diverse complex that likely represents multiple cryptic species (3). In Mexico, this species has been previously reported in northeastern Morelos on Quercus sp., eastern Mexico State on Pinus hartwegii, and southwestern Mexico State on Prunus persica (1,2). This study identified associations with 10 new hosts within three states of Mexico, but only five hosts were diseased. Genet MEX7R comprised seven isolates collected in the University of Chapingo forest near Texcoco, Mexico State (19°18′10.764″ N, 98°42′14.147″ W, elevation 3441 m). Four MEX7R isolates were collected from diseased Alnus sp. including the root ball of a 130 cm dbh, root-disease killed tree, one isolate from a symptomless Senecio sp. s.l. (Roldana sp.) shrub and two isolates from symptomless Abies religiosa. Genet MEX11R comprised four isolates from a cloud forest near Xalapa, Veracruz (19°31′14.628″ N, 96°59′22.812″ W, elevation 1496 m). MEX11R isolates were collected from the roots of a root-disease killed Carpinus caroliniana, and from trees with no obvious symptoms (Miconia mexicana, Quercus xalapensis, and Liquidambar styraciflua). Two isolates of genet MEX23R were collected from the Jardin Botanico Francisco Javier Clavijero, Instituto de Ecologia, A.C., Xalapa, Veracruz (19°30′49.067″ N, 96°56′32.999″ W, elevation 1344 m). These isolates were from root-diseased Eriobotrya japonica (non-native fruit tree) that showed obvious symptoms (flaccid, chlorotic, and senescing leaves) and from an adjacent, infected Platanus mexicana that did not show readily observable symptoms. Two collections near Oaxaca, Oaxaca, included a single isolate MEX28R from the root ball of a recently root disease-killed Arbutus xalapensis within a small root disease center at Peña Prieta, in Parque La Cumbre, near Ixtepeji (17°09′42.084″ N, 96°38′15.936″ W, elevation 2853 m) and a single isolate MEX30R from the base of an asymptomatic Alnus acuminata near the El Carrizal fish hatchery 10 km northeast of San Miguel del Valle (17°06′45.036″ N, 96°24′03.743″ W, elevation 2594 m). Armillaria gallica has a circumpolar distribution with an extremely wide host range, and its ecological behavior varies greatly. Continued surveys are needed to better understand the distribution and ecological impacts of this pathogen in relation to Armillaria root disease in Mexico and the potential influences of climate change. Although A. gallica displays diverse ecological behavior, trees infected with A. gallica are less likely to survive the stresses of human activity and a changing climate (4). References: (1) D. Alvarado-Rosales and R. A. Blanchette. Phytopathology 84:1106, 1994. (2) R. D. Elias-Roman et al. For. Pathol. 43:390, 2013. (3) M.-S. Kim et al. Phytopathology 102:S4.63, 2012. (4) B. Marcais and N. Breda. J. Ecol. 94:1214, 2006.

This study aimed to evaluate and compare the relationship between chemical properties, energy efficiency, and emissions of wood and pellets from madroño Arbutus xalapensis Kunth, tázcate Juniperus deppeana Steud, and encino colorado Quercus sideroxyla Humb. &amp, Bonpl. in two gasifiers (top-lit-up-draft (T-LUD) and electricity generation wood camp stove (EGWCS)) in order to determine the reduction of footprint carbon. In accordance with conventional methodologies, we determined the extracts and chemical components (lignin, cellulose, holocellulose), and the immediate analyses were carried out (volatile materials, fixed carbon, ash content and microanalysis of said ash), as well as the evaluation of emission factors (total suspended particulate matter (PM2.5), CO, CO2, CH4, black carbon (BC), elemental carbon (EC), and organic carbon (OC)). The results were statistically analyzed to compare each variable among species and gasifiers. The raw material analyzed showed how the pH ranged from 5.01 to 5.57, and the ash content ranged between 0.39 and 0.53%. The content values of Cu, Zn, Fe, Mg, and Ca ranged from 0.08 to 0.22, 0.18 to 0.19, 0.38 to 0.84, 1.75 to 1.90, and 3.62 to 3.74 mg kg−1, respectively. The extractive ranges from cyclohexane were 2.48–4.79%, acetone 2.42–4.08%, methanol 3.17–7.99%, and hot water 2.12–4.83%. The range of lignin was 18.08–28.60%. The cellulose content ranged from 43.30 to 53.90%, and holocellulose from 53.50 to 64.02%. The volatile material range was 81.2–87.42%, while fixed carbon was 11.30–17.48%, the higher heating value (HHV) of raw material and pellets presented the ranges 17.68–20.21 and 19.72–21.81 MJ kg−1, respectively. Thermal efficiency showed statistically significant differences (p &lt, 0.05) between pellets and gasifiers, with an average of 31% Tier 3 in ISO (International Organization for Standardization) for the T-LUD and 14% (ISO Tier 1) for EGWCS, with Arbutus xalapensis being the species with the highest energy yield. The use of improved combustion devices, as well as that of selected raw material species, can reduce the impact of global warming by up to 33% on a cooking task compared to the three-stone burner.

Arbutus xalapensis Kunth (Texas madrone, Ericaceae) is found in western and central Texas, but its ecological characteristics are little known. Mature A. xalapensis plants were found in the Albert and Bessie Kronkosky State Natural Area in Kendall and Bandera counties, central Texas (29.740278 N, –98.838333 W). Habitats studied included Acer grandidentatum Nutt. (bigtooth maple) canyon bottoms, Juniperus ashei J.Buchholz/Quercus L. sp. (Ashe juniper/mixed oak) hillsides, and J. ashei uplands. Population characteristics were compared to habitat and surface geology. A total of 98 A. xalapensis plants were found in the communities studied. Differences were found for all parameters except height. Upland A. xalapensis trees had the lowest mean (±SD) density (2 ± 3 plants/ha), highest basal area (210 ± 190 cm2/plant), community elevation (573 ± 14 m) and height (4.09 ± 1.70 m/plant). Hillside communities had the highest density (61 ± 38 plants/ha), but lower basal area (110 ± 170 cm2/plant). The canyon bottom plant basal area was 80 ± 100 cm2/plant and density was 10 ± 5 plants/ha. The canyon bottoms had the deepest soil (27.2 ± 20.4 cm) and lowest elevation (510 ± 16 m). When geological substrates were examined, 128 additional plants were found. The largest plants were on the Fort Terrett member of the Edwards limestone (hard limestone, 230 ± 220 cm2/plant), but density was the lowest (2 ± 3 plants/ha). Whereas greater density was on the Upper Glen Rose limestone (softer limestone, 16 ± 7 plants/ha), where plants were smaller (110 ± 150 cm2/plant). Community type and geological substrate seem critical for growth of this species.