Pine-oak Forest Research Articles

О новой находке редкого вида Neottianthe cucullata (L.) Schlechter (Orchidaceae) в Брянской области

In the course of a geobotanical survey of the forests of the Klyukovensky district forestry in the Bryansk Region, the author discovered a new locality of the rare species Neottianthe cucullata (L.) Schleichter (Orchidaceae). To identify the phytocoenotic relationships of the studied species, relevés of the forest vegetation were carried out, which is assigned to the association of acidophylous herbaceous pine-oak forests of Polesye landscapes of the Southern Nechernozemye of Russia Vaccinio myrtilli–Quercetum roboris Bulokhov et Solomeshch 2003. The main recommendation for the protection of the species is the maximum limitation of the impact of anthropogenic factors (clear felling, collection of plants, trampling, fires) by creating specially protected natural areas and allocating especially protective forest areas during forest management in places of growth of N. cucullata.

A Dynamical Model Based on the Chapman–Richards Growth Equation for Fitting Growth Curves for Four Pine Species in Northern Mexico

Tree growth models describe the growth and development of forest ecosystems by considering how the dimensions of each simulated tree change within a certain time. These models have commonly used three growth parameters that describe various biological processes and behaviours, considering a sigmoid growth function: (i) the upper asymptote (θ1), which is the maximal yield indicated by a final dimension (such as the maximal stem diameter); (ii) the maximum specific growth rate (θ2), defined as the slope of the tangent at the inflexion point; and (iii) the time elapsed (θ3), defined by the intercept of this tangent with the abscissas. To the best of our knowledge, however, associations between the three parameters have not been documented for tree species. Using diameter growth data from pine trees located in typical mixed and uneven-aged pine-oak forests in the Sierra Madre Occidental, Mexico, our study aims were: (i) to quantify the putative associations between the three growth parameters and (ii) to test the accuracy of a proposed Hybrid Chapman-Richards growth model based on associations between the three growth parameters, but including only one single parameter, relative to the widely used Generalized Algebraic Difference Approach (GADA) based on the Chapman-Richards, Lundqvist and Hossfeld models and the Hybrid Weibull Model. For statistical comparison of the quality of the models, we used the mean relative percentage error, root mean square error, coefficient of determination and Akaike information criterion to assess the quality of the fit. Although the quality of the five growth models studied was similar, from a practical point of view, the proposed Hybrid Chapman-Richards Model (CR-H) is easier to apply than the other models and has a lower data collection and computational cost. The parameter of CR-H can be easily obtained, by measuring just the dominant trees, especially in coniferous forests with irregular ages. Moreover, in contrast to the Chapman-Richards-GADA factor χ0, when θ2 is assumed to be site-specific, the CR-H has always a closed-form solution.

The family Opilioacaridae (Parasitiformes: Opilioacarida) in Mexico, description of two new species, new records, and geographical distribution

Two new species of Neocarus (Opilioacarida: Opilioacaridae), N. haicolous n. sp. and N. queretanus n. sp., are described from mesophyll and pine-oak forests in the state of Querétaro, central Mexico. One species was described from adults and tritonymphs. Distribution and habitat preferences of all known collections of Opilioacarida are reviewed. In Mexico, they have been collected in all habitats, from semideserts areas to tropical forest and from to sea level in dunes to high temperate and cloud forest.

Nutrients (N, P, K, Na) and warming affect heterotrophic respiration in temperate forest litter

At present, ecosystems are facing changes caused by global warming and anthropogenic impacts on geochemical cycles. Both temperature and nutrient availability affect litter decomposition; however, little is known about their simultaneous effect on litter decomposition in temperate forests, especially for nutrients such as Na and K. To address this perspective, we investigated how changes in N, P, Na and K supply and increased temperature affect litter decomposition measured as respiration. Moreover, the study determines what changes can be expected in the functioning of two forest types of different fertility (deciduous and coniferous). The respiration measurements were conducted in the laboratory in mesocosms filled with litter from deciduous (oak-hornbeam) and coniferous (mixed pine-oak) forests fertilized by N, P, K, and Na. The experiment was conducted at ambient (14 °C; oak-hornbeam and mixed pine-oak litter) and increased temperatures (22 °C; oak-hornbeam litter). The respiration of oak-hornbeam litter increased with increasing temperature, with Q10 values ranging from 1.49 to 2.14. Our results showed different responses of respiration to nutrient addition between temperatures and litter types. In oak-hornbeam, at 14 °C, the addition of N, P and K decreased respiration, whereas at 22 °C, such an effect was noted only under N application, and P and Na addition increased respiration. In mixed pine-oak litter at 14 °C, respiration decreased after Na addition, and other nutrients had no effect. Together, our results suggest that forecasting the impact of nutrient deposition on ecosystem functioning should consider temperature rise as a factor altering ecosystem responses to fertilization in future research.

Relative abundance, habitat selection, and diet of the coyote in northern México

The coyote (Canis latrans) is a widespread predator with a high degree of adaptation to different ecosystems. The objective of this study was to estimate the relative abundance index, habitat selection, and diet of C. latrans through scent stations, in two types of vegetation located in northwestern Chihuahua. From April 2018 to March 2019, ten fixed scent stations (SS) were placed in pine-oak forest and other ten in semi-open grassland, with a linear separation of 500 meters between each station to achieve a five km transect in each vegetation during 12 samplings (two sampling night per month) for totaling 420 SS after discarding inactive SS. The relative abundance index of coyote showed that both types of vegetation, pine-oak forest (0.30) and semi-open grassland (0.23) were used in a similar way. The habitat selection test (Chi2) showed that coyote abundance and type of vegetation were independent (χ2 = 2.96, P > 0.05), not showing statistically significant differences in annual relative abundance index of coyotes between the two vegetation types. The food items detected in thirty-four scats collected belonged to mammals (55.9 %), fruits (35.3 %) and arthropods (8.8 %). Rodents and lagomorphs were the main source of food. Throughout the sampling period, the pine-oak forest showed the greatest relative abundance index of C. latrans. This may be because the forest provides them with shelter from climatic situations and a greater variety of seeds, fruits and insects. In this study the two seasons with the highest relative abundance were spring and autumn in both ecosystems, coinciding with an increase in rainfall, resulting in an abundance of potential prey (rodents and lagomorphs), and other food items like fruits. Regarding annual diet the most consumed prey were mammals. We found differences in diet between seasons, that can be explained by the variation in food availability among seasons.

A Tool for the Assessment of Forest Biomass as a Source of Rural Sustainable Energy in Natural Areas in Honduras

Forest biomass as a rural sustainable energy source has received much attention in recent years due to its major economic, social, and environmental benefits. This research focuses on an adapted methodology based on parameters of the Evaluation of Ecological Integrity for using site-specific information as a tool for the assessment of forest biomass as a source of rural sustainable energy in Honduras, focusing on the Central American Pine–Oak Forests. The parameters used were Percentage of Forest Cover (FC), Patch Area (AREA), Fractal Dimension Index (FRAC), and Proximity Index (PROX). The goal was an average index rating of 5 for an ecosystem which is intact or in its natural state. The findings showed an ecosystem degradation that was outside the range of acceptable variation with a simple average of 1.75, which is far lower than the target rating of five (5.0); the forest cover loss was 40% of the total area. This surprising finding shows that immediate intervention is required to maintain this ecosystem, and that if action is not taken, the ecosystem will suffer severe degradation. Decision makers must consider this methodology for using site-specific information and ensure that local communities are involved in restoring the ecosystem.

Fire history and vegetation data reveal ecological benefits of recent mixed-severity fires in the Cumberland Mountains, West Virginia, USA

BackgroundWithout periodic fire, fire-adapted plant communities across the Central Hardwood Forest Region (CHF) in the USA have undergone significant changes in forest structure and species composition, most notably a decrease in oak regeneration and herbaceous diversity and an increase in shade-tolerant, fire-sensitive tree species. In this study, we conducted a comparative analysis of two mixed pine-oak (Pinus-Quercus) forests with different land management histories in the Cumberland Mountains of southern West Virginia where fire ecology and fire effects are understudied. We reconstructed the fire history of both sites from fire-scarred shortleaf pine (Pinus echinata Mill.) and pitch pine (Pinus rigida Mill.) trees to describe variation in the fire regimes over time. We also made plant community measurements that spatially coincided with fire-scarred pines to assess present-day plant community structure in relation to recent fire history.ResultsBefore 1970, fires at Hite Fork and Wall Fork occurred frequently and almost exclusively in the dormant season, every 7–8 years on average. The fire regimes diverged in the Post-Industrial era (1970–2020), during which there was a single fire at Wall Fork, while six major fires, scarring more than 40% of sampled trees, occurred between 1985 and 2017 at Hite Fork. Four of these dormant-season fires correspond to late fall incendiary fires in the observational record. These differences in recent fire history had large effects on plant community structure. Recent mixed-severity fires at Hite Fork likely caused mortality of pole-sized trees and opened the canopy, creating conditions favorable for pine recruitment and resulted in significantly higher species richness in the herbaceous layer compared to Wall Fork, which exhibited the effects of mesophication.ConclusionsOur results suggest that frequent mixed-severity fire in pine-oak forests of the Cumberland Mountains can meet management objectives by reducing mesophytic tree abundance, increasing herbaceous diversity and pine recruitment, and generally promoting forest heterogeneity.

Estimating maximum stand density for mixed-hardwood forests among various physiographic zones in the eastern US

Quantifying maximum stand density is important to evaluate the potential stand density of the target population in forest management. However, most of the past research in the eastern US was mainly focused on planted monocultures, coniferous forests, a few commercially important species at the stand level, or in a particular geographic region. This study aimed to estimate the maximum stand density for mixed-hardwood forests across physiographic zones in the eastern US between two decades (1996–2009 and 2010–2021). Data used in analyses were collected from the US national forest inventory established and maintained by the USDA Forest Service’s Forest Inventory and Analysis (FIA) program.Results showed that the slope of the self-thinning lines varied among forest types. Estimating maximum stand density index (SDImax) from size-density relationships produced more precise estimates than using SDI-size curves. Among all forest types, elm-ash-cottonwood (Ulmus-Fraxinus-Populus) showed consistent SDImax estimates whereas other forest types varied by regions. New England had considerably higher SDImax in aspen-birch (Populus-Betula), oak-hickory (Quercus-Carya) and oak-pine (Quercus-Pinus) forests than other physiographic zones. Most of the combinations showed consistent SDImax between two time periods. Only six combinations showed a significant gain (4–14% increase), which was likely driven by the growth of the same dominant species groups. The findings of this work provided not only additional insights of maximum stand density in the region, but also a methodology for forest ecologists and managers to quantify SDImax for a variety of forest types.

Palynological analysis of an archaeological chinampa in Xochimilco (Basin of Mexico). Construction technology and agricultural production

In order to better understand the construction techniques used in archaeological chinampas excavated at San Gregorio Atlapulco, Xochimilco (located in the southern Basin of Mexico), modified standard techniques for the extraction of palynomorphs were applied. The palynological assemblage recovered from the archaeological chinampa and adjacent canal profiles suggests that the local and regional vegetation present in the Basin of Mexico consisted of halophilic and aquatic vegetation, grassland, pine-oak forest and Abies forest. The abundant Amaranthaceae pollen observed could come from different species and have diverse origins, however, it may indicate the cultivation of Suaeda sp., a highly prized food plant in Mexican cuisine. The analyses suggest that the construction technique in the archaeological chinampa is similar to the models previously proposed, but this particular variant incorporates some modifications described in other examples. According to radiocarbon determinations, it is suggested that the chinampa was constructed following the Classic period, after around 1640 BP (340–540 cal CE), and was probably utilized initially during the Aztec I-II periods. Therefore, we conclude that the elaboration and maintenance techniques of the SGAX-CH02 chinampa at Xochimilco were more diverse than previous research on archaeological chinampas suggests.

The cultural role played by the ethnomycological knowledge of wild mushrooms for the peoples of highlands and lowlands in Tlaltenango, Zacatecas, Mexico

ABSTRACT The greatest diversity of culturally relevant fungi in Mexico has been recorded in temperate forests. Likewise, it has been proven that people who live in such environments possess greater ethnomycological knowledge, compared with people in the lowlands. In this study, we investigated whether the uses and perceptions of fungi were different between people living near forests in highlands and those living in lowlands near grasslands and subtropical scrublands. We selected seven communities from the municipality of Tlaltenango, Zacatecas, Mexico, where we conducted guided tours, 35 semistructured interviews, and free lists to 420 people. Since highlands surrounded by temperate forests give rise to high species diversity, we expected that the inhabitants, in comparison with those of the lowlands where there is less diversity, would recognize a larger number of fungi. To test this hypothesis, we employed discriminant function analysis, principal coordinate analysis, Mann-Whitney U test, and linear regression. The cultural importance of each species was calculated based on the frequency with which it was mentioned and the first principal coordinate. Although the highlanders have a deeper knowledge of mushrooms, lowlanders and highlanders had similar fungal backgrounds and preferred the same species, regardless of the fungi surrounding their territory. The lack of differences among communities was due in part to the fact that the most culturally important species were those that grew in grasslands and subtropical scrub areas. Agaricus campestris was the most culturally prevalent and only commercialized species both in the highlands and lowlands, followed by Pleurotus djamor and Volvariella bombycina. None of the mushrooms growing in the pine-oak forest had a high cultural importance value, even for the communities living in the vicinity of this forest, forcing them to travel long distances to collect Agaricus campestris. Further investigations are needed in order to assess the relevance of sociocultural factors, and their potential influence in the preference for particular mushrooms in this region.

Taxonomy of the Mexican species of Belonuchus Nordmann (Coleoptera: Staphylinidae).

Belonuchus is a diverse genus in the subtribe Philonthina (subfamily Staphylininae, tribe Staphylinini), with some of its species being frequently collected. For the majority of the Mexican species of Belonuchus, little or no taxonomic information has been reported after their original description. For this reason, the Mexican species of Belonuchus were taxonomically revised based on the study of specimens deposited in several Mexican and international collections. We propose eight species groups to accommodate the Mexican species, five of them supported by one unique diagnostic character. Keys to species groups and species in each group, together with photos and drawings of diagnostic structures, are included. Redescriptions of the 29 known species, descriptions of 16 new species, with information about intraspecific variation in terms of secondary sexual dimorphism and size, two new country records (Mexico and Guatemala) and 26 new state records are also included. We propose B. xanthopus Solsky, 1868 and B. celatus (Sharp, 1885) as new synonyms of B. connexus (Say, 1830); B. iteratus (Sharp, 1887) as a new synonym of B. xanthomelas Solsky, 1868; B. latecinctus (Sharp, 1885) as a new synonym of B. iridescens Solsky, 1868; and B. mexicanus Solsky, 1864 as a new synonym of B. viridipennis Baudi di Selve, 1848. Lectotypes were designated for: Belonuchus cariniventris Bernhauer, 1918; Philonthus trochanterinus Sharp, 1885; Philonthus zunilensis Sharp, 1885; Belonuchus jalappensis Bernhauer, 1917; Philonthus iteratus Sharp, 1887; Belonuchus nigerrimus Bernhauer, 1918; and Belonuchus pectinipes Bernhauer, 1910. The Mexican species of Belonuchus are mostly recorded from cloud forest (60%), oak forest (51.1%) and oak-pine forest (46.6%).

Oribatid mites in agricultural and natural soils: a case study of vertical distribution

The vertical distribution of oribatid mites was evaluated in a natural soil (pine-oak forest) in the municipality of San Juan Nuevo and an agricultural soil (avocado crop) in the municipality of Uruapan in Michoacán, Mexico. Samples were taken in seven layers distributed in a 100 cm deep trench. A total of 466 oribatid mites/cm3, representing 37 species of 29 genera were identified. In both sites, the highest abundance and biodiversity were found in the top 5 cm layer. Nothrus anauniensis Canestrini & Fanzago, 1877 (Nothridae), Ramusella (Insculptoppia) merimna Balogh & Mahunka, 1977 (Oppiidae), Allogalumna (Acrogalumna) sp. 1 (Galumnidae) and Scheloribates sp. 2 (Scheloribatidae) were found at the greatest depths (10–25 cm in natural soil and 25–50 cm in agricultural soil).

Different xylogenesis responses to atmospheric water demand contribute to species coexistence in a mixed pine–oak forest

Seasonal patterns of wood formation (xylogenesis) remain understudied in mixed pine–oak forests despite their contribution to tree coexistence through temporal niche complementarity. Xylogenesis was assessed in three pine species (Pinus cembroides, Pinus leiophylla, Pinus engelmannii) and one oak (Quercus grisea) coexisting in a semi-arid Mexican forest. The main xylogenesis phases (production of cambium cells, radial enlargement, cell-wall thickening and maturation) were related to climate data considering 5–15-day temporal windows. In pines, cambium activity maximized from mid-March to April as temperature and evaporation increased, whereas cell radial enlargement peaked from April to May and was constrained by high evaporation and low precipitation. Cell-wall thickening peaked from June to July and in August–September as maximum temperature and vapour pressure deficit (VPD) increased. Maturation of earlywood and latewood tracheids occurred in May–June and June–July, enhanced by high minimum temperatures and VPD in P. engelmannii and P. leiophylla. In oak, cambial onset started in March, constrained by high minimum temperatures, and vessel radial enlargement and radial increment maximized in April as temperatures and evaporation increased, whereas earlywood vessels matured from May to June as VPD increased. Overall, 15-day wet conditions enhanced cell radial enlargement in P. leiophylla and P. engelmannii, whereas early-summer high 15-day temperature and VPD drove cell-wall thickening in P. cembroides. Warm night conditions and high evaporation rates during spring and summer enhanced growth. An earlier growth peak in oak and a higher responsiveness to spring–summer water demand in pines contributed to their coexistence.

Variación en diversidad y composición de especies macrofúngicas a través de diferentes tipos de vegetación en Oaxaca, México

Background: Macromycetes play relevant roles in ecosystem functioning as pathogens, mutualists, and organic matter decomposers. Their diversity and distribution are strongly related to environmental conditions and vegetation types, however, there is a lack of ecological studies assessing which biotic and abiotic factors affect macrofungal communities.
 Questions: Which vegetation type harbors the highest macromycete diversity? Do macromycete diversity and species composition change among forest types? Which are the main environmental factors related to diversity and distribution patterns along the study area?
 Data description: Macromycete species richness and abundance, and environmental variables recorded in temperate forests.
 Study site and dates: Ayoquezco de Aldama, Oaxaca. June-November 2019.
 Methods: Macromycetes were collected twice a month in oak, oak-pine, pine-oak and pine forests, and environmental variables were recorded at each site. Species diversity and composition turnover were calculated using diversity and similarity indexes. The relation between diversity and species composition with environmental variables was determined with statistical analyses.
 Results: A total of 186 species were collected. Oak-dominated forests showed the highest similarity in macromycete diversity and species composition. The observed patterns of diversity and distribution were related mainly to air and soil humidity and temperature, topographic factors, and vegetation structure.
 Conclusions: Macromycete diversity and species composition can conspicuously change in short distances owing to the heterogeneity of habitats and resources provided by woody plants, and the topographic characteristic of the landscape. Vegetation type affects both macromycete diversity and distribution due to its influence on local temperature and humidity.
 
 
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First record of the bryophilous fungi Paruephaedria heimerlii (Dactylosporaceae, Ascomycota) for Mexico

Background and Aims: The briofilous fungi are a diverse and polyphyletic group of symbiotic mushrooms associated specifically with few bryophyte species, genera or families. Paruephaedria heimerlii stands out as a species with a bryophilous habit in Jungermanniales; it is known from Alaska, Europe, Japan and Tasmania. Therefore, the objective of this work is to present the first record of this species in Mexico, its first known tropical locality.Methods: The studied specimens were collected in the vegetation of pine-oak forest and tropical cloud forest in the state of Veracruz, Mexico. The material was herborized and decontaminated by cooling, followed by determination from histological sections of the ascomas and observed with an optical microscope. Finally, the material was deposited in the fungal collections of the herbaria ENCB of the Instituto Politécnico Nacional and XALU of the Facultad de Biología of the Universidad Veracruzana.Key results: Using morphological characteristics and measures of sexual structures like spores, asci and hymenial structures, the studied material was determined as Paruephaedria heimerlii, representing the first record of this species both in Mexico and for the tropics. Conclusions: According to our observations and comparisons with reports in literature, it is probable that the presence of P. heimerlii is not conditioned to the temperature or altitude of the habitat in which it is found, but to the availability of hosts.

Insect infestations and the persistence and functioning of oak-pine mixedwood forests in the mid-Atlantic region, USA.

Damage from infestations of Lymantria dispar L. in oak-dominated stands and southern pine beetle (Dendroctonus frontalis Zimmermann) in pine-dominated stands have far exceeded impacts of other disturbances in forests of the mid-Atlantic Coastal Plain over the last two decades. We used forest census data collected in undisturbed and insect-impacted stands combined with eddy covariance measurements made pre- and post-disturbance in oak-, mixed and pine-dominated stands to quantify how these infestations altered forest composition, structure and carbon dynamics in the Pinelands National Reserve of southern New Jersey. In oak-dominated stands, multi-year defoliation during L. dispar infestations resulted in > 40% mortality of oak trees and the release of pine saplings and understory vegetation, while tree mortality was minimal in mixed and pine-dominated stands. In pine-dominated stands, southern pine beetle infestations resulted in > 85% mortality of pine trees but had minimal effect on oaks in upland stands or other hardwoods in lowland stands, and only rarely infested pines in hardwood-dominated stands. Because insect-driven disturbances are both delaying and accelerating succession in stands dominated by a single genus but having less effect in mixed-composition stands, long-term disturbance dynamics are favoring the formation and persistence of uneven age oak-pine mixedwood stands. Changes in forest composition may have little impact on forest productivity and evapotranspiration; although seasonal patterns differ, with highest daily rates of net ecosystem production (NEP) during the growing season occurring in an oak-dominated stand and lowest in a pine-dominated stand, integrated annual rates of NEP are similar among oak-, mixed and pine-dominated stands. Our research documents the formation of mixedwood stands as a consequence of insect infestations in the mid-Atlantic region and suggests that managing for mixedwood stands could reduce damage to forest products and provide greater continuity in ecosystem functioning.

A strikingly ornamented fossil alligator lizard (Squamata:Abronia) from the Miocene of California

AbstractExtant alligator lizards of the genus Abronia are found in montane cloud forests and pine-oak forests of Mesoamerica and are iconic among the public and scientific communities. Here, we describe a fossilized partial skull from the Miocene of southern California (~12.5–11.0 Mya) that is the first definitive fossil and only recognized extinct species of Abronia. The locality of the fossil is substantially removed from the range of extant species of Abronia. This remarkable biogeographical discovery corroborates previous speculation that Abronia was distributed north of Mexico during the Neogene, a scenario that could not be inferred from the geographical ranges and phylogeny of the extant species alone. Additionally, the fossil preserves a distinctive morphology, osteoderm sails, that appears unique to the new taxon among alligator lizards. The finding emphasizes the importance of the fossil record for historical biogeography and could motivate new avenues of biogeographical research in Mesoamerica and the USA.

Bess Beetle (Coleoptera: Passalidae) Species Composition Across the Altitudinal Gradient of Montecristo National Park, El Salvador.

Bess beetle species tend to be endemic and are useful indicators for the designation of conservation areas. However, little is known about the diversity and distribution of these beetles in El Salvador. Here, we present results from a study testing if species segregated along the altitudinal gradient of Montecristo National Park, El Salvador. The survey was done between September and December 2015. Beetles were collected at nine transects from three ecosystems, which included cloud, mixed-pine, and dry forests that occur along the altitudinal gradient of Montecristo. We sampled a total of 696 trees, finding 79 galleries of bess beetles, belonging to 13 species, which included: Arrox agassizi (Kaup), Chondrocephalus granulifrons (Bates), Chondrocephalus sp., Chondrocephalus salvadorae (Schuster), Heliscus eclipticus (Truqui), Odontotaenius striatopunctatus (Percheron), Ogyges politus (Hincks), Oileus sargi (Kaup), Passalus punctatostriatus Percheron, Passalus punctiger Lepeletier & Audinet-Serville, Verres hageni Kaup, Vindex sculptilis Bates, and Chondrocephalus gemmae Reyes-Castillo & Castillo which is a new species record for El Salvador. We found that species segregated by altitude, with the highest species richness observed in the cloud forest (n = 6), followed by the dry (n = 5) and mixed pine-oak (n = 4) forests. Most species were randomly associated with different tree species trunks, with the exception of V. hageni which was associated with trunks of Cecropia sp. Loefl. (Rosales: Urticaceae), and P. punctastriatus and P. punctiger which were associated with trunks of Cordia alliodora (Ruiz & Pav.) Oken (Boraginales: Boraginaceae). Our results show that species segregate by habitat, as only two species (C. gemmae and H. eclipticus) were found in more than one ecosystem.

Changes in forest structure and composition in a pine-oak forest in Jaumave, Tamaulipas, Mexico

The pine-oak forest is distributed from the north to the south of Mexico, it has high susceptibility to degradation due to the increasein forest fires, pests, and other extremenatural events, which makes the need to conserve and sustainably use its resources relevant.Even when these forests are in a wide ecological niche (300 to 2500 m altitude), their populations are affected by the interaction ofextreme natural events and anthropogenic disturbances, causing changes in their structure and species composition. The floristiccomposition and forest structure of a pine-oak forest in Jaumave, Tamaulipas, were analyzed over 15 years, with three alternatesamplings in this period. A systematic samplingwas conducted in thirty-two circular plots of 1,000 m². In each plot, all trees with adiameter> 7.5 m were identified and measured. Basalarea (BA), density and species richnesswere calculated. In addition, the type offorest and disturbance type were identified. 3,567 individuals of sixteen distinct species (six familiesand six genera) were registered;the Quercus genus was the most abundant, representing 60% of the arboreal individuals. Three types of forests were defined: pine,oak, and pine-oak, based on the dominance of the basal area. Significant differences were found between measurement dates andfamilies(Pinaceae and Fagaceae, p <0.01). The BA increased with respect to the first and last measurement, increasing the BA of theoaks, while in pines it decreased. The differences were explained by the possible increase in pests, associated with prolongeddroughts registered between the years 2004 and 2010; causing a decrease in AB. Additionally, BA was affected by silviculturaltreatments applied in the control of debarker beetle (Dendroctonus sp.)

Long-term plant community responses to resource objective wildfires in montane coniferous forests of Grand Canyon National Park, USA

Interest in use of naturally ignited wildland fires managed to meet multiple resource objectives (resource objective wildfire) is increasing among U.S. public forest managers; however, only a limited number of studies have examined this approach for conserving or restoring understory plant diversity, productivity, and community structure. We analyzed understory community changes two andtwelve yearsafter resource objective fire, using permanent sample plotsin three montane contrasting forest types in Grand Canyon National Park,AZ.Our findingsindicatedthat species compositionin the pine-oak forest rebounded to be similar to that observed before the fire, but plant cover did not recover to pre-fire levels by the twelfth year post-fire. Plant cover showed mixed results post-fire in mixed-conifer and spruce-fir forests, and species composition was still characterized by ruderal species twelve years later. Patterns observed in this study likely reflect interacting factors of burn severity, periodic drought, large ungulate herbivory, and inherent site variability. Other than cheatgrass (Bromus tectorum), we found no non-native speciesoccurring with high frequency. Continued monitoring with increased frequency and intensity could lead to better understanding of long-term changes in these forests after resource objective fire, and enhance our understanding of important drivers of variation including interactions ofclimate, burn severity and herbivory by large ungulates.