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Interspecific trait divergence may reflect adaptation and reproductive isolation, particularly after the rapid differentiation that may follow the colonization of new environments. Although new lineages are generally expected to be morphologically and ecologically similar to their ancestors, environmental forces can also drive adaptive differentiation along specific phenotypic axes. We used climate niche models and comparative analyses based on a previously inferred phylogeny to examine the history of ecological and morphological divergence of Neotropical firs (Abies Mill., Pinaceae), a group of conifers that have recently colonized and diversified in the mountains of Mexico and northern Central America. We inferred past secondary contact zones by comparing current and past climate niche projections and looked for evidence of recent interspecific gene flow using genomic data. Neotropical firs have similar niches to each other and show a strong phylogenetic signal for most evaluated morphological traits. Analyses based on individual variables suggested a random walk model of differentiation. However, early adaptation to tropical conditions is inferred in the ancestor of the southernmost firs, as all modern southern taxa are differentiated climatically from Abies concolor, the northernmost species. In addition, observed autapomorphic traits for soil properties and the number of resin ducts in needles are consistent with possible species‐specific adaptations. Thus, a combination of nonadaptive and adaptive processes along different phenotypic axes, some related to the environment, likely operated after the southward migration of this plant lineage from North America and its subsequent radiation in the Neotropics. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chapingo Serie Ciencias Forestales is the property of Universidad Autonoma Chapingo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Forest inventory is the primary method for collecting and recording information regarding the volumetric quantification and yield of trees. However, this is difficult when the individual has been cut and only the stump remains, in which case inventory is achieved through regression techniques. The objective of this work was to adjust allometric equations for the estimation of normal diameter (dn), total height (at) and volume (v) using the stump diameter (dt) for Abies religiosa in different regions of Mexico. A total of 2,599 data points from 20 forest management units were used to analyze the variables and their respective predictions through eight allometric equations, which were evaluated with different statistical criteria. The adjusted coefficient of determination (R2 adj) explained 91 % of the normal diameter, together with the root mean square error (RMSE) of less than 4.75 cm with respect to the allometric equation (3). Another of the best options to estimate the total height is the Schumacher exponential (4) and the allometric (6) with values of R2 adj of approximately 50 %, accompanied by RMSE less than 5.03 m. However, for the volume of the forest, Schumacher's equation was considered pertinent since it has a RMSE ranging from 0.00001 to 0.0026 m3 with R2 adj that explains more than 74 % of the variation of the data observed in each UMAFOR. These regressions may be useful for the restoration of trees after an unplanned or unexpected felling event, as the results are statistically reliable. [ABSTRACT FROM AUTHOR]

Objective: To quantify and characterize the canopy rainfall interception of two dominant forest species of a coniferous forest in Mexico, in order to determine its magnitude and importance in the hydrological cycle and have a source of estimation of interception to improve the accuracy of water balance calculation. Methodology: Twenty-one rainfall events in the period May-June 2018 were analyzed in two 0.25-ha experimental plots, one with pine (Pinus hartwegii) and the other with oyamel (Abies religiosa), at the Zoquiapan Experimental Forest Station (EFEZ), located in the Sierra Nevada in the State of Mexico. Rainfall was measured with an automated weather station and interception was recorded by placing collectors under the canopy and collars on the trunks. Results: The pine tree P. hartwegii intercepted 16.37% of the precipitation, 79.86% of the throughfall, and 3.74% of the stemflow. For A. religiosa, recorded interception was 24.68%, throughfall 72.42%, and stemflow 2.90%. Precipitation had a linear relationship with both throughfall and stemflow, and an exponential one with canopy rainfall interception. Implications: The analysis should be extended to other rainy periods to strengthen the study. Conclusions: The intercepted volume depends on the forest measurement characteristics and leaf area index (LAI) of the species, and the rainfall amount. The fraction of rainfall intercepted is considerable and should be included in hydrological balances. [ABSTRACT FROM AUTHOR]

Abies hidalgensis is an endemic species from the state of Hidalgo, Mexico, that has been registered only in nine fragmented relict populations that have a total of 1 000 individuals among them. Intensive forest management takes place in five of the populations under specific programs focused on Pinus spp. Still, it is necessary to know the impact of these activities on the genetic diversity of the threatened species, if restoration and conservation strategies are to be proposed. The aim of this work was to estimate the effect of forest management on the genetic structure of A. hidalgensis using seven nuclear molecular markers developed for A. guatemalensis (Ab07, Ab08, Ab09, Ab12, Ab15, Ab20, Ab23). The species was sampled growing under two different conditions; (i) areas under forest management and (ii) conserved areas. Two indexes of genetic diversity were evaluated, observed and expected heterozygosity. The genetic structure was determined by an analysis of molecular variance and a Bayesian assignment model. A bottleneck analysis was also carried out. The populations were found to have a common genetic base (differentiation coefficient FST = 0.056, number of migrants per generation Nm = 43), which suggests recent fragmentation of the distribution, which in turn increases the bottleneck effect in managed areas (Wilcoxon probability Wp = 0.007 and 0.016). This explains the apparently high heterozygous level (He = 0.69) and low inbreeding. Our results are important as they may be used to design strategies for management and conservation of A. hidalgensis. [ABSTRACT FROM AUTHOR]

Height-diameter models are fundamental for the inventory of timber, biomass and carbon. Located in the central region of Mexico, Abies religiosa is a conifer with high timber value that lacks models to estimate its height as a function of diameter. The objective of this study was to determine a local height-diameter model for A. religiosa trees under a mixed-effects model approach in the region of Tlaxco, Tlaxcala, Mexico. The first step consisted in evaluating the quality of fit of three growth models and one power model. We used height-diameter data of 1,539 trees measured in 197 circular plots of 1,000 m². The selected model was the Weibull, which was adjusted in a second step under the mixed-effects modelling approach. Our results showed that the most accurate predictive capacity was obtained when using the sub-basin covariate as a clustering factor and the random effect in the parameter corresponding to the asymptote. Under this approach, the goodness of fit of the model was superior to the traditional one adjusted by nonlinear least square. Comparatively the gains in fit statistics R², RSME and AIC were of 12.19 %, 47.99 % and 8.46 %, respectively. The proposed model is robust, reliable, and biologically coherent for its operational application in the forest management of A. religiosa in the study region. [ABSTRACT FROM AUTHOR]

Secondary contact of recently diverged species may have several outcomes, ranging from rampant hybridization to reinforced reproductive isolation. In plants, selfing tolerance and disjunct reproductive phenology may lead to reproductive isolation at contact zones. However, they may also evolve under both allopatric or parapatric frameworks and originate from adaptive and/or neutral forces. Inferring the historical demography of diverging taxa is thus a crucial step to identify factors that may have led to putative reproductive isolation. We explored various competing demographypotheses to account for the rapid divergence of a fir species complex (Abies flinckii–A. religiosa) distributed in "sky‐islands" across central Mexico (i.e., along the Trans‐Mexican Volcanic Belt; TMVB). Despite co‐occurring in two independent sympatric regions (west and centre), these taxa rarely interbreed because of disjunct reproductive phenologies. We genotyped 1147 single nucleotide polymorphisms, generated by GBS (genotyping by sequencing), across 23 populations, and compared multiple scenarios based on the geological history of the TMVB. The best‐fitting model revealed one of the most rapid and complete speciation cases for a conifer species‐pair, dating back to ~1.2 million years ago. Coupled with the lack of support for stepwise colonization, our coalescent inferences point to an early cessation of interspecific gene flow under parapatric speciation; ancestral gene flow during divergence was asymmetrical (mostly from western firs into A. religiosa) and exclusive to the most ancient (i.e., central) contact zone. Factors promoting rapid reproductive isolation should be explored in other slowly evolving species complexes as they may account for the large tropical and subtropical diversity. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chapingo Serie Ciencias Forestales is the property of Universidad Autonoma Chapingo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Jalisco fir (Abies jaliscana) is an endemic tree with restricted distribution, and is considered a Pliocene relict inhabiting the cloud montane forests in the humid-temperate upper zone of western Jalisco Mountains. Despite its ecological importance, to date, there are no studies for this taxon aimed to understand its vulnerability to regional climate variability. We used dendrochronological techniques to investigate tree-ring patterns and the effects of climate variability on the radial growth of Jalisco fir through its elevational range in both southern and northern aspects. We developed tree-ring series that ranged in length from 79 to 152 years. High-elevation trees (2400 m.a.s.l.) showed higher annual radial growth compared to those present in low-elevation sites. Over the last 150 years, Abies jaliscana trees have had higher annual radial growth rates compared to those exhibited by other Abies species. Both winter and early spring precipitation are the main factors determining the growth rates at all the elevation sites for both aspects. In the cold season, mean maximum temperature negatively affected ring-width growth at most of the elevation zones except for two study sites. We conclude that the radial growth of A. jaliscana appears to be smaller during lower rainfall periods in the dry seasons (winter and early spring), and A. jaliscana annual radial growth responds differently to regional climate variability along the elevational gradient and mountain aspects. [ABSTRACT FROM AUTHOR]

Background: Recruitment after disturbance events depends on many factors including the environmental conditions of the affected area and the vegetation that could potentially grow in such affected areas. To understand the regeneration characteristics that occurs in temperate forests, we evaluated differences in the number of seedlings from trees and shrubs along an altitudinal gradient in Sierra Norte of Oaxaca, Mexico in different biological, climatic, edaphic, light, topographic, and disturbance regimes. Here, we aimed to test the hypothesis that the environmental disturbances influence on recruitment (positive or adverse influence). We sampled the vegetation to obtain recruitment and adult data, and species composition. Results: We identified three disturbance regimes: areas affected by forest harvesting, areas exposed to pest management, and undisturbed areas. We identified 29 species of trees and shrubs (9 species of the genus Pinus, 1 species of the genus Abies, 10 species of the genus Quercus, and 9 of other species of broadleaf). We found that both environmental conditions and disturbances influence the recruitment of vegetation in the study area. In particular, disturbances had a positive influence on the regeneration of oak and other broadleaf species by increasing the number of seedlings, and a negative influence on the regeneration of conifers by decreasing the recruitment. Because the recruitment of conifers is more likely in undisturbed areas (sites over 3050 m). Conclusions: Environmental factors and anthropogenic disturbances can alter the recruitment of forests. Consequently, knowing which factors are key for the recruitment of vegetation is fundamental for decision-making processes. This is particularly relevant in areas as the one in this study because it provides knowledge to local people on vegetation recovery for a proper management of their biological resources. [ABSTRACT FROM AUTHOR]

Aim: Estimating genetic diversity is key for understanging biogeographic and evolutionary processes. However, gathering genetic information is not feasible for all taxa or populations, particularly in the tropical regions. Identifying proxies for inferring such values has thus become essential. Here, we built on the niche centrality hypothesis (NCH; or central‐abundance hypothesis) and the nearly neutral theory of evolution (NNT) to identify some of such proxies using a montane tropical conifer species‐pair as model. The NCH predicts more genetic diversity under optimal ecological conditions, which should also allow for more efficient purifying selection, according to the NNT. Location: The Transmexican Volcanic Belt, central Mexico. Taxa: A fir species‐pair endemic to central Mexico, Abies flinckii and A.religiosa. Methods: We estimated patterns of genetic diversity from nuclear SSRs (A, HE), and gene‐coding sequences (πS, πN), together with the efficacy of purifying selection, measured as πN/πS. After testing for niche overlap, we used several geographic and ecological proxies (i.e. longitude, latitude, elevation, estimated area and distance to the niche centroid in the present and in the LGM) to predict genetic diversity and πN/πS using general linear models. Results: Populations at the west of the Trans Mexican Volcanic Belt (TVB) had lower genetic diversity than populations in the east of this mountain chain. Both species had significant niche overlap. The principal predictors for neutral genetic diversity (HE, A and πS) were longitude and latitude, followed by the current distance to the niche centroid; the efficiency of purifying selection was mostly accounted for by the current distance to the niche centroid (which was also correlated with elevation). No correlation was observed between genetic diversity or πN/πS and current population area. Main conclusions: Historical and ecological factors have to be taken into account for explaining the amounts of genetic diversity in mountain tropical species. Following the NTT, populations closer to the niche centroid are more efficient at eliminating slightly deleterious mutations than marginal stands, independently of their size or geographic location (longitude). Expanding the central‐abundance theory within the scope of the NTT might help reconciling conflicting views concerning the extent of its empirical support. [ABSTRACT FROM AUTHOR]

Interacting stochastic and selective forces drive population and species divergence. Such interaction may generate contrasting clines between genetic and phenotypic factors, which can be related to either geographical or environmental variation depending on the predominant evolutionary force (which in its turn is partly determined by population size). Here, we investigated whether the morphological and genetic differentiation across a species complex in Abies in central Mexico fits isolation by distance (IBD) or isolation-by-adaptation (IBA) frameworks. This complex includes two species (A. religiosa and A. flinckii) with discernible morphological and environmental differences and dissimilar range sizes. After comparing variation at nuclear SSR loci and diagnostic morphological traits of needles with the climate variables contributing to ecological differentiation, we found that the widely distributed A. religiosa has more genetic diversity and is morphologically more heterogeneous than the geographically restricted A. flinckii. Morphological differentiation at three physiologically important traits (needle thickness, number of stomata rows and location of the resin duct) is significantly correlated with geography in A. flinckii (indicative of IBD), but is significantly associated with climate variation in A. religiosa (suggesting IBA). In agreement with quantitative genetics theory, P ST (phenotypic differentiation)- G' ST (genetic differentiation) comparisons indicate contrasting contributions of putatively adaptive (A. religiosa) and stochastic (A. flinckii) factors to the morphological differentiation of species related to their population size. The integration of such quantitative genetic/evolutionary aspects may reinforce species descriptions and help in disentangling resilient taxonomic discordance. [ABSTRACT FROM AUTHOR]

Ongoing climate change is expected to alter forests by affecting forest productivity, with implications for the ecological functions of these systems. Despite its great dendrochronological potential, little research has been conducted into the use of wood density as a proxy for determining sensitivity to climate variability in Mexico. The response of Abies durangensis Martínez, in terms of wood density and growth ring width, to monthly climatic values (mean temperature, accumulated precipitation and the drought index SPEI) was analyzed through correlation analysis. Abies durangensis presents a high response, in terms of radial growth, to climatic conditions. Tree-ring widths are more sensitive to hydroclimatic variables, whereas wood density values are more sensitive to temperature. In particular, mean (MeanD) and minimum (MND) wood density values are more sensitive to climate than maximum (MXD). We found very marked spatial variations that indicate that A. durangensis responds differently to drought conditions depending on the indices of density. [ABSTRACT FROM AUTHOR]

Fir dwarf mistletoe (Arceuthobium abietinum, Viscaceae) parasitizes true firs (Abies spp.) in the Pacific Northwest through California, the Southwest, and into northern Mexico. At present, fir dwarf mistletoe consists of two special forms (formae speciales, f. sp.) and one subspecies that are morphologically similar, but exhibit a high degree of host specificity. However, A. abietinum has been treated as a subspecies of A. campylopodum or conspecific with it in some taxonomic treatments. Therefore, we undertook this study to compare the morphologies of these dwarf mistletoes; collecting morphological data from nearly 100 A. abietinum and 60 A. campylopodum populations collected across most of their geographic ranges and analyzing these data using univariate and multivariate statistical tests. Our results demonstrated that the special forms and subspecies of A. abietinum are morphologically distinct from A. campylopodum, thereby, supporting the continued recognition of A. abietinum as a separate species. Furthermore, our analysis found significant differences for several of the characters we examined between the special forms of A. abietinum. Therefore, we recombined the special forms as subspecies: A. abietinum subsp. abietinum (formerly f. sp. concoloris) and A. abietinum subsp. magnificae (formerly f. sp. magnificae). The previously described A. abietinum subsp. wiensii was morphologically distinct from subsp. abietinum and subsp. magnificae. The distinctiveness of these taxa was supported by their host affinities as well. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chapingo Serie Ciencias Forestales is the property of Universidad Autonoma Chapingo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The present study was based on determining the natural potential of Abies guatemalensis Redher (Guatemalan fir) in the Forest Management Unit (UMAFOR) 07 Sierra of the state of Chiapas, to identify the optimal sites for its establishment. Geographic information systems (GIS) were used as a technological tool to model the variables that determine the distribution of the species. The information collected in the field was: altitude, exposure, slope, coordinates, as well as thematic maps of soil, vegetation, climate, precipitation and a digital elevation model, with which slope, exposure and altitude cover were generated. The variables that showed the best results were: altitude, humid temperate climate and annual precipitation greater than 2,000 mm. The vegetation corresponds to coniferous and coniferous-broadleaf trees with a slope of 25 to 50%, respectively. This is due to the fact that the productivity of the forests is linked to the ecological attributes of the territory. In this context, the study showed an area of 15,380.71 hectares with the potential to establish A. guatemalensis Redher., in five municipalities of UMAFOR 07 Sierra. With the use of GIS technology, the results were reliable enough to establish reforestations or plantations for the recovery or conservation of the pine. [ABSTRACT FROM AUTHOR]

National Parks in Mexico are home to small communities. Whereas productive activities are by definition prohibited within park limits, restoration and conservation practices are encouraged. One way to benefit the inhabitants of these parks is to promote conservation practices that can be productive at the same time. This paper describes and evaluates the practice of regular pruning of Abies religiosa (HBK) in the Cofre de Perote National Park as both a measure to prevent forest fires and a means to obtain the raw material for the manufacturing of Christmas wreaths. Under the guidance of our university research team, over a period of 3 years, local women pruned trees over a total area of 36 ha and used part of the pruning waste (2.71 %) to make the wreaths. The income generated from pruning and from sale of the wreaths contributes significantly to household expenses. We describe the collaboration between the local Women's Group, the academic team, a federal government agency and the local authorities. The study concludes that the laws regulating national parks in Mexico should specifically stress the importance of allowing productive activities compatible with conservation. [ABSTRACT FROM AUTHOR]

In "El Chico", National Park, in Hidalgo, México is a study was carried out with the objective of estimating the biomass and carbon stored in the dead trees standing, in the live adult trees and seedlings established in natural form of Abies religiosa "oyamel" after 12 years of a forest fire of superficial type that affected 30,34 hectares. A forest inventory was made on 15 circular sites of 1000 m² each, distributed in a systematic way, in order to measure the variables of normal diameter and height. To determine the biomass the density value of fir wood was used (360 kg/m³) and for the carbon coefficient the Solids TOC Analyzer® was utilized, obtaining a value of 0,45. The generated equations to estimate the biomass and carbon in trees of Abies religiosa in an area affected by a forest fire were B=0,06463 * DN2,38322 and C=0,029083 * DN2,38322 respectively, showing a good adjustment (R²=0,99); these equations are considered to be suitable and reliable to be used in damaged areas with similar conditions, for the same species and for regions such as Natural Protected Areas where it is not possible to use destructive methods. In 30,34 damaged hectares of the "El Chico" National Park, there were a total of 665,05 tons of stock carbon not consumed by the fire, to which must be added a current capture of 297,33 tons of carbon by the seedling established in the twelve years from the disaster. [ABSTRACT FROM AUTHOR]

Carbon content of aboveground biomass of six types of vegetation cover in the Magdalena River basin, located in the conservation land in the Mexico City, was estimated. Hence, a map of cover vegetation and land use to the study area was made; a hierarchical stratified sampling design with distribution systematic with a mesh of sampling sites equidistant of 550 meters was used for field work. The method used for field data collection was based on a nested design, with an intensity of sample of 0,64%. There were generated 52 sites of 3000 m². The vegetation cover that showed the highest amount of carbon stored corresponds to the forest of the the Abies religiosa closed with 163 Mg C ha-1 in average; followed by the Abies religiosa - Pinus hartwegii closed with 107 Mg C ha-1, and Abies religiosa opened with 95 Mg C ha-1; about the covers of Pinus sp., Pinus hartwegii closed with 47 Mg C ha-1; Pinus hartwegii - Abies religiosa closed with 39 Mg C ha-1 and Pinus hartwegii opened with 21 Mg C ha-1. [ABSTRACT FROM AUTHOR]

The genus Abies has about 40 species, which are mainly distributed in boreal or subalpine areas. In Mexico as a diversity center for this genus, all eight species of Abies are protected. Six of them are endemic and mainly distributed in the Sierra Madre Occidental and Oriental. The often isolated relict Abies durangensis Martínez, also known as Durango Fir, is located in the states of Durango, Chihuahua, Sinaloa, and Jalisco and usually grows on slopes with well-drained and shallow lithosols, where the climate is humid and cool. A. durangensis is specifically associated with species such as Pseudotsuga menziesii, Pseudotsuga lindleyana, Pinus strobiformis, Picea chihuahuana, Pinus durangensis, Cupressus lusitanica (lindleyi), and Juniperus deppeana. In the state of Durango, the species has a restricted geographic distribution between 23.2° and 25.7°N and 105° to 107°W and elevations varying from 2,195 m to 2,955 m (mean 2,690 m). The species' habitat has a mean annual temperature that ranges from 8.6 °C to 12.2 °C (mean 10.6 °C) and a mean annual rainfall of 1,088 mm to 1,395 mm (mean 1,224 mm). According to the Red List of Threatened Species of the International Union for Conservation of Nature and Natural Resources, the species is in low risk and does not depend on conservation efforts. [ABSTRACT FROM AUTHOR]

Abstract: Abies religiosa (HBK) Schl. & Cham. (oyamel fir) is distributed in conifer-dominated mountain forests at high altitudes along the Trans-Mexican Volcanic Belt. This fir is the preferred host for overwintering monarch butterfly (Danaus plexippus) migratory populations which habitually congregate within a few stands now located inside a Monarch Butterfly Biosphere Reserve. Our objectives were to predict and map the climatic niche for A. religiosa for contemporary and future (2030, 2060 and 2090) climates, suggest management strategies to accommodate climate changes, and discuss implications for conservation of monarch butterfly overwintering sites in Mexico. A bioclimate model predicting the presence or absence of A. religiosa was developed by using the Random Forests classification tree on forest inventory data. The model used six predictor variables and was driven primarily by the mean temperature of the warmest month, an interaction between summer precipitation to and winter temperatures, and the ratio of summer to annual precipitation. Projecting the contemporary climate niche into future climates provided by three General Circulation Models and two scenarios suggested that the area occupied by the niche should diminish rapidly over the course of the century: a decrease of 69.2% by the decade surrounding 2030, 87.6% for that surrounding 2060, and 96.5% for 2090. We discuss assisted migration of A. religiosa upwards in altitude by 275m so that populations of 2030 would occupy the same climates as today. The projections also show that by the end of the century, suitable habitat for the monarch butterfly may no longer occur inside the Biosphere Reserve. We therefore discuss management options and associated research programs necessary for assuring perpetuation of future butterfly habitat. [Copyright &y& Elsevier]

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: Nurse-plant effects have been used as an effective reforestation and restoration strategy, and mulching has also effectively ameliorated soil-adverse conditions. However, use of nurse plants is limited by the presence of suitable nurse species before trees are planted, and use of mulching depends on availability of appropriate materials. The effects of Lupinus elegans as a nurse plant and pine-bark mulch were tested on three conifer species: Pinus montezumae, Pinus pseudostrobus, and Abies religiosa. We tested if nurse-plant type effects occurred if the lupines and the conifers were planted simultaneously. Overall survival was 53%, and significant differences among species were found. Survival regardless of cover type was significantly higher (P <0.01) for P. pseudostrobus 17-month-old seedlings at planting (81%), followed by P. montezumae 7-month-old seedlings at planting (71%), P. pseudostrobus 7-month-old seedlings at planting (42%) and finally A. religiosa 7-month-old seedlings at planting (17%) the differences among the treatments were significant (P <0.01). As a soil shading agent, lupines had a significant effect (P =0.02), because they increased survival of P. pseudostrobus and A. religiosa, the effect of mulching with pine bark was not significant. The effects of a shading agent on growth differed among species. In particular lupines reduced height and stem diameter for P. montezumae and P. pseudostrobus, between 22% and 33%, and had no effect on growth of A. religiosa. The positive effects of the simultaneous planting of L. elegans on the survival of the trees suggests that nurse-plant facilitation can be used in areas where no suitable nurse plants are already present. [Copyright &y& Elsevier]

Tropospheric ozone has been suspected to cause poor vitality and occasional massive mortality in sacred fir (Abies religiosa (Kunth) Schltdl. & Cham) from Desierto de los Leones National Park, in Mexico City, Mexico, since 1980's. This work searches for empirical evidences of ozone effects on health indicators of natural populations of sacred from August 2001 to January 2003. We monitored 31 selectively chosen sampling plots with passive monitors. Two additional fir forests with expected low exposure to ozone were used as control. Mean hourly ozone concentration per period (2 to 3 weeks each), fluctuated between 4,826 x10-7 and 0,0441 ppm. Most ozone readings were high, the mean hourly concentration in Desierto de Los Leones was 0,0186 ppm, but only three readings marginally exceeded a 0,0400 ppm toxic threshold. Ozone concentrations in control areas had a lower average (0,0145 ppm), with erratic wide fluctuations. We found no relationship between ozone concentrations and sampling plot location, elevation, temperature or region. Foliage retention, crown density, vigor and stand basal area follow weak, but constant and consistent worsening trends as ozone mean site concentration increases. This trend suggests fir health reduction with increasing ozone concentration; control values are consistent with this trend. This result differs from reports of ozone damages on fir, except the case of Switzerland where fir occurs at high elevations and shows clear anatomic damages due to chronic ozone exposure, just like the Mexican case. [ABSTRACT FROM AUTHOR]

Copyright of Revista Chapingo Serie Ciencias Forestales is the property of Universidad Autonoma Chapingo and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This morphometric study of the geographic variation in the Abies religiosa–hickelii–guatemalensis complex is based on samples from 15 Guatemalan and 12 Mexican populations, two populations of A. religiosa s.str. and A. hickelii s.str., and herbarium specimens of A. hickelii, A. vejarii and varieties of A. guatemalensis. The multivariate methods employed were principal components analysis, and UPGMA clustering. The multivariate and univariate analyses based on 231 operational taxonomic units imply that although morphological differences exist distinct morphospecies cannot be recognized within the A. religiosa–hickelii–guatemalensis complex. A Mantel’s test reports that taxonomic dissimilarities are significantly related to geographic distance. We suggest, therefore, that A. religiosa, A. hickelii and A. guatemalensis are merged so that A. hickelii is referred to as A. religiosa subsp. hickelii (Flous & Gaussen) U. Strandby, K.I. Chr. & M. Sørensen, comb. et stat. nov. and A. guatemalensis as A. religiosa subsp. mexicana (Martínez) U. Strandby, K.I. Chr. & M. Sørensen, comb. nov. According to our analyses A. vejarii cannot retain its status as a separate taxon as the material studied is nested within A. religiosa subsp. mexicana. [ABSTRACT FROM AUTHOR]

• We studied bark beetle outbreaks patterning (elevation and year) and climate in Mexico. • We used datasets of outbreak phytosanitary logging authorizations and TerraClimate. • Outbreaks on Abies religiosa occur on pure and better-preserved stands. • Outbreaks on Pinus pseudostrobus occur on the lower elevational limit (xeric limit) • Logging authorization coincides with driest Palmer Drought Severity Index anomaly. Climate change is an important risk factor for forest ecosystems through alteration of forest disturbance regimes such as bark beetle outbreaks, which in some places now are more successfully attacking host trees weakened by hotter drought events. In Mexico, ties between climate and amplified outbreaks of bark beetles have begun to be documented, although these relationships are not entirely clear. This project aims to identify the geographic patterning and relations between climate and bark beetle outbreaks in Abies religiosa and Pinus pseudostrobus populations located in the Trans-Mexican Volcanic Belt region. We used: 1) a database of phytosanitary logging authorizations and locations issued to enable salvage logging of trees infested or killed by bark beetle outbreaks from 2009 to 2018; 2) a previously developed gridded database of contemporary suitable climatic habitat of these tree species that will be lost by 2060 to determine if outbreaks occurred in sites with climatic habitat lost; and 3) elevation values to determine if outbreaks occur at xeric limits (drought limits) of tree hosts. Climate analysis was conducted with TerraClimate data using PDSI (Palmer's Drought Severity Index) values. We find that bark beetle outbreaks do not necessarily occur at sites where models project that both species will lose suitable climatic habitat. For A. religiosa (Sacred Fir), of the 4091 ha treated by sanitary logging , 40% occurs between 3000 and 3100 m of elevation, where the pure and relatively better-preserved Sacred Fir stands are found. For P. pseudostrobus, more than 54% of the sanitary logging area (4664 ha) ranges from 2200 to 2400 m a.s.l., which coincides with the lower elevation limit (xeric limit) of the natural distribution of the species. Regarding relationships with PDSI, for A. religiosa there was a one-year lag between the year of mortality (expressed by the year of the phytosanitary logging authorization) and the year with the most negative (driest) PDSI anomaly (one year before), while for Pinus pseudostrobus , phytosanitary logging authorizations were concentrated in the driest year. An investigation that considers more variables, especially anthropogenic factors, is necessary to be able to better understand the dynamics of forest pests and prevent unusual outbreaks induced by expected climate-change-amplified droughts. [ABSTRACT FROM AUTHOR]

The isoprenoid emission of sacred fir (Abies religiosa (Kunth) Schltdl. & Cham. ), patula pine (Pinus patula Schiede, Schltdl. & Cham. ) and net-leaf oak (Quercus rugosa Née) was investigated in Mexico City during the years 2002 and 2003. Chemical compound specific emission factors were obtained for different months of the year. Net-leaf oak is an isoprene emitter whereas the other tree species emit monoterpenes. -Pinene and linalool are the main compounds emitted from sacred fir and patula pine, respectively. In general, the emission of monoterpenes is temperature dependent, whereas-pinene emission of sacred fir is controlled by light and temperature like the isoprene emission of net-leaf oak. All isoprenoids show a strong seasonality which is plant species specific. Emission factors for the conifers were high in October and low in April (sacred fir: in October and in April; patula pine: in October and in June). Isoprene emission potential of net-leaf oak was very variable in the different seasons with low source strengths in July (rainy season: ) and November (cold/dry season: ) but high in May (warm/dry season: ). The results indicate that present biogenic emission inventories of the Mexico City area have to be revised by using the new emission factors of native tree species including the seasonal impact. [Copyright &y& Elsevier]

The reproductive capacity in nine Mexican Douglas-fir populations was determined by analyzing seed production traits from 144 trees collected in 2001. Significant variation was found for all traits among populations; they contributed between 21% and 43% of total phenotypic variation found in these traits, indicating broad differences in reproductive capacity for that particular year. Seed efficiency (filled seed/seed potential) varied from 14% to 42% among populations; all populations from Central Mexico had a seed efficiency below 25%. The proportion of developed that were empty seeds varied from 0.40 to 0.81 among populations, whereas seed size varied also from 0.88 to 1.21 g per 100 seeds among them. Average ratio of filled seed weight to cone weight (reproductive efficiency) was 29.6 mg g-1, but it varied three-fold between populations with extreme values. Populations with larger cones had greater seed potential and heavier seed but not necessarily higher reproductive or seed efficiency. Most reproductive indicators were significantly correlated with latitude, with lower values in the marginal populations from Central Mexico, in the southern extreme of the species range. Given these results, the need for conservation of Douglas-fir populations in Central Mexico is discussed. [ABSTRACT FROM AUTHOR]

Since the monarch butterfly overwintering habitat was discovered in the mountainous fir forests in central Mexico three presidential decrees have been issued (1980, 1986, 2001) to protect it. But these forests are the source of livelihood for many local people, whose activities (wood extraction and clearance for subsistence farming) represent a major threat to the forests, and thus to the butterfly population. This study identifies important deforestation, disturbance, and recovery processes caused by human activities in the protected areas and their surroundings. Contrary to our expectations, the protected areas have been most negatively affected by human activities, whereas areas devoted to multiple uses have been more adequately preserved. [ABSTRACT FROM AUTHOR]

Rainfall interception plays a role in the hydrological cycle and is a critical component of water balances at the basin level, which is why understanding it is very important; as a result, in recent years, various authors have proposed different models to explain this process and identify which of them adapts better to each forest species. In this context, the aim of this research was to evaluate the Gash model and the sparse Gash analytical model in Pinus hartwegii Lindl. and Abies religiosa (Kunth) Schltdl. et. Cham., using measurements from 20 precipitation events recorded in May and June 2018 at the Zoquiapan Experimental Forest Station, Mexico. The evaporation rate was calculated using the Penman–Monteith method (PM) and Gash's calculation procedure. The canopy parameters were also calculated with two methods, a graphical one (A) and a method proposed in this research (B), which is based on point cloud generated with drone photogrammetry. For P. hartwegii, the most accurate model to estimate interception per rainfall event was the Gash model with the A and Gash methods, which were used to calculate the canopy parameters and evaporation rates, respectively; for accumulated interception, the sparse Gash analytical model with the B and PM methods was used. For A. religiosa, the best fit for individual events was presented by the sparse Gash analytical model with the B and PM methods, and for accumulated interception, it was the Gash model with the B and Gash methods. The results allow concluding that the B method proposed in this research is a good alternative for the calculation of rainfall interception, since it tends to improve its estimation, shortening the time for acquiring information about the parameters of the canopy structure and thus minimizing the costs involved. [ABSTRACT FROM AUTHOR]

The oyamel forests, as Abies dominated forests are commonly known as, register their largest distribution (95% of their population) along the Trans-Mexican Volcanic Belt (TMVB). Although efforts have been made to study these forests with various approaches, dendrochronology-based studies have been limited, particularly in pure Abies forests in this region. The objective of this study was to reconstruct fire regimes in an Abies religiosa forest in the Sierra Norte in the state of Puebla, Mexico. Within an area of 50-ha, we collected 40 fire-scar samples, which were processed and analyzed using dendrochronological techniques to identify 153 fire scars. The fire history was reconstructed for a period of 118 years (1896–2013), with low severity surface fires occurring mainly during in the spring (92.8%) and summer (7.2%). Over the past century, fires were frequent, with an mean fire interval (MFI) and Weibull median probability of (WMPI) of five years when considering all fire scars and less than 10 years for fires covering larger areas (fires recorded by ≥25% of samples). Extensive fires were synchronized with drought conditions based on Ring Width Indexes, Palmer Drought Severity Index (PDSI) and El Niño Southern Oscillation (ENSO). After 1983, we observed a change in fire frequencies attributed to regulated management. Longer fire intervals within the last several decades are likely leading to increased fuel accumulations and could potentially result in more severe fires in the future, threatening the sustainability of these forests. Based on our finding, we recommend management actions (silvicultural or prescribed fire) to reduce fuels and the risk of severe fires, particularly in the face of climatic changes. [ABSTRACT FROM AUTHOR]

Presents an abstract of the study `Isozyme and foliar terpene variation in the Abies of northern Mexico,' by Glenn R. Furnier, Yolanda G. Nava et al, presented during the 1996 Annual Meeting of the Botanical Society of America at the University of Washington in Seattle, Washington.