Pine Oak Research Articles

Elucidating the composition of organic matter in water-repellent forest soils using analytical pyrolysis combined with gas chromatography–mass spectrometry (Py-GC–MS)

Soil water repellency (SWR) is an inability of soil to spontaneously absorb water. It affects the spatial distribution of soil moisture, may cause formation of preferential flow, increase surface runoff and the risk of water erosion, or affect nutrient availability for crops. Although there is a general agreement among published data that SWR is caused by hydrophobic components of soil organic matter (SOM), more comprehensive information is needed. Additionally, the link between SWR occurrence and SOM genesis has not been studied sufficiently. In this work, we analyzed SOM in water-repellent soils by pyrolysis combined with gas chromatography and mass spectrometry (Py-GC–MS). The samples were taken from two forest ecosystems in Slovakia: relatively dry pine–oak forest, located in the Záhorská nížina lowland (Záhorie), and spruce forest in the High Tatras with a colder and more humid climate. The results showed that the composition of SOM at both sites is dominated by partially decomposed residues of plant biomass. Whereas most compounds detected in the Záhorie samples were identified as pyrolysis products of lignin, the pyrolysates of the High Tatras soils originated mainly from polysaccharide-like substances. Although lauric (12:0), myristic (14:0) and palmitic (16:0) fatty acids were detected in pyrograms of water-repellent samples, the results suggest that the residues of lignin decomposition may contribute to SWR as well. Pyrolysates such as methylguaiacol, vinylguaiacol, dimethylphenol, or the methyl ester of vanillic acid are examples of less polar lignin-like moieties. Py-GC–MS data, as well as other soil properties, suggest that SWR at both sites is associated with the accumulation of certain SOM components in the topsoil. Acidic pH, higher C/N ratio and coarse soil texture prevent organic carbon stabilization in the studied soils. As a result, SOM is in great part composed of accumulated particulate residues with lignin-like origin and lipidic coatings, which contribute to SWR development during drier conditions.

Infection intensity shapes specialization and beta diversity of haemosporidian–bird networks across elevations

AbstractHost–parasite distribution and interactions depend on geography, evolutionary associations, species composition, and their response to environmental variables. In this sense, host specificity as a key parasite's life history trait may determine parasite community composition but can be difficult to identify in nature. The haemosporidian–avian host communities of tropical mountain systems offer an opportunity to better understand how network interactions influence parasite–host specialization. By using frequency (i.e., prevalence) and interaction intensity (i.e., number of parasites per infected host) data, we calculated two quantitative indices to evaluate haemosporidian host specialization at both community (H2′) and haemosporidian lineages and bird species levels (d′). Additionally, we evaluated alpha (SI) and beta diversity (βWN) of haemosporidian–bird interactions along four distinct elevations (representing different vegetation types) in Central Veracruz, Mexico. We recorded 607 birds from 88 species in two sampling years, registering 78 haemosporidian cytochrome b lineages by PCR in 125 positive samples from 38 bird species. Haemosporidian–bird interactions showed high specialization and modular network structure for each vegetation type. The degree of specialization and modularity was stronger when considering interaction intensity (i.e., parasitemia). Species‐level specialization was higher for birds than for haemosporidians at the two vegetation types with highest interaction richness (i.e., pine–oak forest and tropical deciduous forest). There were high interaction beta diversity values (~1) among vegetation types, reflecting turnover in both avian and parasite communities. Our findings suggest that vegetation type (proxy for the local environmental conditions) constrains the distribution of hosts and parasites, and that intraspecies infection intensity plays an important role in the transmission dynamics and interactions of the haemosporidian community.

Regional Drivers behind the Burning of Remanent Forests in Michoacán Avocado Belt, Central Mexico

The state of Michoacán in central Mexico supplies nearly 50% of the global avocado trade in a region known as the Michoacan Avocado Belt or Avocadoland. Fire has been a component associated with regional land-use change processes. We documented fire regime attributes for the period 2000–2017, discussed the use of fire related to the expansion of avocado orchards, and evaluated the role of atmospheric variables and human infrastructure. There was a mean of 276 fires covering 3287 ha of forest per year. Over 80% of the burned area was covered by pine and pine–oak forests, with a strong correlation of ignitions with the distance to urban settlements, roads, agricultural plots, and avocado orchards. There is a median fire return interval of 2–3 years, and the distance to avocado orchards and main roads was highly correlated with fire recurrence. Final users of the international marketing of this fruit may be unaware of the fire-related land-use changes, namely, the damage to biodiversity, forest health, and water bodies, as well as to producers’ well-being, behind the great demand for avocados. The present conditions of insecurity and social conflict must be addressed to guarantee, among other things, the conservation of these diverse forests.

A new species of Mutinus (Phallaceae, Phallales) from Shandong Province, China

A new species, Mutinus taishanensis (Phallaceae, Phallales, Basidiomycota), was found growing in a forest of Phyllostachys flexuosa and Quercus palustris in Zhulin Temple, Mount Tai Scenic Area (Tai’an City, Shangdong Province, China). It is described as new based on morphological, molecular and ecological evidence. Our phylogenetic analyses based on DNA sequences of the large subunit of nuclear ribosomal DNA (LSU), subunit 6 of ATP synthase (atp6) and the second largest subunit of RNA polymerase II (RPB2) support the inclusion of this new species in the genus Mutinus as it forms an independent clade in the phylogenetic tree. Morphologically, M. taishanensis differs from any known species by the combination of light red to red pseudostipe, red conical fertile portion (covering about 1/4–1/5 of the total length of pseudostipe), and relatively small basidiospores. We present this new species with illustrated morphological description. phylogeny and comparison with morphologically similar or phylogenetically related species.

Nelsonia goldmani(Rodentia: Cricetidae)

AbstractNelsonia goldmani Merriam, 1903 is a cricetid rodent commonly called Goldman’s diminutive woodrat. It is a woodrat of medium size with grayish dorsal pelage; the characteristic long tail is covered with long hairs and ends with a black tip. Nelsonia goldmani is one of two species in the genus Nelsonia. It is endemic to the central-west highlands of Mexico, recorded in a few localities of the Trans-Mexican Volcanic Belt at elevations from 2,000 to 3,100 m. It inhabits areas near rocky ravines, cliffs, and hillsides with coniferous, pine–oak, and cloud forests. Nelsonia goldmani is listed as “Endangered” (EN) by the International Union for Conservation of Nature and Natural Resources due to its fragmented distribution and the decrease in the quality and extent of its habitat.

Wood Colour Variations of Quercus Species in Romania

Wood colour metrics are increasingly being used in wood technology and ecology studies. Researchers usually determine the colours of the wood after treatment or in different habitats. There is very little research dedicated to the problem of colour variations among one specific species harvested in different forests or regions. The main purpose of the current research is to reveal and estimate the colour variability of oak species. For this study, a total of 89 samples were taken from the heartwood of seven oak species (Quercus robur L., Quercus cerris L., Quercus rubra L., Quercus pedunculiflora K. Koch., Quercus pubescens Willd., Quercus petraea (Matt.) Liebl., and Quercus palustris Muenchh.). The CIELAB system was used for the assessment of the colour differences. To determine the colour groups and variations, K-means clustering was used. The results show that colour variations do exist. According to the cluster analysis, at least five types of oak wood can be distinguished (because in some clusters, very few samples were present) in the investigated forests. The differences are mainly observed in terms of the lightness (L*) and yellowness (b*). Redness is not a feature by which oak wood differs, but the wood can be brighter or more yellow in some of the samples. The density of the Romanian oaks in the sample does not influence the colour coordinates. The only coordinate affected is a*, but with a very small probability.

Seasonal Dynamics of Soil Microbial Biomass C, N and P along an Altitudinal Gradient in Central Himalaya, India

This study was conducted in a temperate mixed oak–pine forest of Central Himalaya, India to (i) evaluate altitudinal and seasonal variations in the microbial biomass carbon (C), nitrogen (N) and phosphorus (P) and (ii) analyse the relationships between soil microbial biomass C, N and P and physico-chemical properties of soil. Three permanent plots were established in natural forest stands along an altitudinal gradient, three replicates were collected seasonally from each site, and microbial biomass (C, N and P) were determined by a fumigation extraction method. Microbial biomass C, N and P decreased significantly (p < 0.01, correlation coefficient 0.985, 0.963, 0.948, respectively) with increasing altitude having maximum values during rainy season and minimum values during winter season. Microbial biomass C, N and P showed positive correlations with silt particles, water holding capacity, bulk density, soil moisture, organic C, total N and P and negative correlations with sand particles, porosity and soil pH. Microbial biomass C was strongly associated with soil microbial N (r = 0.80, p < 0.01) and P (r = 0.89, p < 0.01) content and soil microbial biomass N and P also showed a strong linear relationship (r = 0.92, p < 0.01). Soil microbial biomass exhibited weak seasonality and was highly influenced by altitude and abiotic variables. The significantly high microbial C, N and P during the rainy season (p < 0.01) and low microbial biomass during the winter season may be due to higher immobilization of nutrients from decomposing litter by microbes as the decomposition rate of litter and microbial activity are at their peak during the rainy period. The microbial C:N ratio indicated that soil fertility is influenced by species composition. Our findings suggested that high microbial biomass and low C:N ratios during the rainy season could be considered a nutrient conservation strategy of temperate mixed oak–pine forest ecosystems.

Responses of natural and artificial pin oak (Quercus palustris) reproduction to a sequence of silvicultural release treatments in bottomland hardwood forests in southern Missouri

Developing competitive oak advance reproduction prior to canopy disturbance is understood to be important for oak regeneration success. In the early 2000s, a study was installed in southeastern Missouri to examine the effects of midstory and understory release on natural and artificial sources of pin oak (Quercus palustris Muenchh.) advance reproduction. The findings obtained three years after midstory and understory release indicated photosynthetically active radiation increased from 3 to 15 % and a corresponding increase in density of pin oak reproduction as well as the survival and growth of both natural and artificial pin oak reproduction compared to control. In 2010, eight years after the midstory and understory was removed, three different overstory harvests were applied to release the established pin oak advance reproduction. Here, we investigated the effects of the midstory and understory removal and the subsequent overstory harvests on underplanted and naturally regenerated oak advance reproduction. We also tested effects of a later midstory release on the density of natural pin oak advance reproduction. Results indicate that the survival of bareroot pin oak seedlings increased with increasing initial basal diameter. The survival of Root Production Method (RPM®) container pin oak seedlings, however, was not dependent on the size at the time of planting. The early understory removal with triclopyr herbicide was ineffective in ensuring survival of planted pin oak seedlings. Shelterwood increased the growth of oak advance reproduction but did not eliminate competition from other species. A late release also failed to increase the growth of oak advance reproduction. Given shelterwood also favored oak competitors in our study, multiple applications of midstory and understory competition control treatments following the shelterwood treatment will be imperative for successful oak regeneration.

Diversity and Genetic Structure of Scarlet Plume (Euphorbia fulgens), an Endemic Plant of Mexico.

Euphorbia fulgens is an ornamental species cultivated in Europe and endemic to Mexico; its ecological, genetic, and evolutionary aspects are not known. The objectives of this study were to determine its distribution, describe the places it inhabits, and analyze the diversity and genetic structures of wild populations of E. fulgens. A bibliographic review of the herbarium specimens and a field evaluation were carried out to develop a potential distribution map based on a multi-criteria analysis of the climatic and topographic variables. Three populations (forty-five individuals) from pine–oak and cloud forests located in the Southern Sierra of Oaxaca were analyzed using ten microsatellite loci. The analysis was conducted using Arlequin v. 3.5, Mega v. 10, and Structure v. 2.3 programs. Eight loci were polymorphic, and a total of thirty-eight alleles were obtained. The average number of alleles per polymorphic locus was 4.6. The average heterozygosity of the three populations was high (Ho = 0.5483), and genetic differentiation between populations were low, with a high genetic flow, suggesting that it could be an ancestral population that became fragmented and was just beginning to differentiate genetically. The information generated on this restricted distribution species can be used in conservation programs pertaining to human activities that endanger the habitats where it is found.

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.

Recurring wildfires provoke type conversion in dry western forests

AbstractRecent wildfires across western North America have burned with uncharacteristically high severity, representing a substantial departure from natural fire regimes. In mixed‐conifer and pine–oak ecosystems of the southern Cascade Range, widespread shifts in stand structure and composition have led to a diversity of post‐wildfire vegetation responses. When recent wildfire “footprints” reburn in subsequent fires, their recovery pathways are complex. In order to understand the effects of overlapping mixed‐severity fires, we quantified changes in overstory and midstory structure and species composition for time periods prior to and following two large overlapping wildfires in the southern Cascades: the 2000 Storrie and 2012 Chips Fires. Plots were stratified into 16 severity combinations (unburned, low, moderate, and high in the Storrie Fire combined with the same four categories in the Chips Fire: e.g., moderate Storrie/high Chips) across the 9000‐ha overlapping burned area. Following the two fires, tree quadratic mean diameter and stand density declined for most species, but changes were species‐specific. Compared with preburn values, importance values for fire‐sensitive white fir (Abies concolor) were reduced by 66%, while resprouting fire‐resilient California black oak (Quercus kelloggii) importance values increased by 37% in severity combinations that included at least one high‐severity fire. Greatest shifts were documented in sites that burned twice at high severity, where resulting vegetation was dominated by oak sprout clumps and resprouting and fire‐stimulated montane chaparral species, while unburned and low‐severity strata retained a substantial component of Douglas‐fir (Pseudotsuga menziesii) and white fir. Results suggest that repeated moderate‐ and high‐severity fires can result in ecosystem state shifting toward fire‐resilient oak‐shrub communities in this fire‐prone landscape. Managers seeking greater landscape resilience can implement treatments such as thinning and prescribed burning, while taking advantage of fire‐created patches such as these in areas where the likelihood of a hotter and drier future makes the reestablishment of continuous forest cover unrealistic.

Phylogenomics of arboreal alligator lizards shed light on the geographical diversification of cloud forest‐adapted biotas

AbstractAimThe proximate ecological and evolutionary processes underlying the high biodiversity of neotropical montane cloud forests are still very poorly understood. Climatic oscillations may have contributed to vicariance and cladogenesis, but also promoted secondary contact and erosion of genetic divergence. Here we tested whether geographical diversification – or its lack thereof – in a complex of arboreal alligator lizards is explained by range shifts during Quaternary climatic oscillations.LocationPine–oak and cloud forests, central Mexico.TaxonAbronia taeniata–gramineaspecies complex (Squamata: Anguidae: Gerrhonotinae).MethodsWe generated genomic data (ddRADseq) to infer patterns of geographical diversification in the complex, reconstruct its demographic history, estimate the timing of lineage split, and test for the presence of contemporary and/or historical hybridization. We evaluated whether the tempo and mode of diversification (i.e. strict isolation vs. secondary contact with introgression) are explained by the contemporary distribution of suitable habitats and/or range shifts experienced by the complex since the Last Glacial Maximum (LGM), as inferred from environmental niche modelling (ENM).ResultsGenomic data supported a marked genetic structure within the complex, and phylogenomic and dating analyses revealed cryptic lineage diversification starting at the onset of the Pleistocene followed by secondary contact with limited introgression. ENM pointed to considerable range expansions of the complex during the LGM and a marked fragmentation and scarce connectivity among contemporary populations, which was supported by genomic‐based demographic reconstructions.Main ConclusionsThe geographical diversification of the complex has been moulded by vicariant events promoted by Pleistocene geologic and climatic changes impacting the distribution of their pine–oak and cloud forest habitats. Our data supported a model of divergence with introgression, indicating that pulses of population fragmentation and expansion during the Quaternary have led to multiple opportunities for both allopatric isolation and secondary contact.

Evaluation of Multiple Forest Service Based on the Integration of Stand Structural Attributes in Mixed Oak Forests

In order to understand forest services at stand level through the integration of structural attributes, forest structures in three main stand types were analyzed based on various structural attributes relating to the services of habitat conservation, timber production and soil water conservation in Loess Plateau, China. Forty sample plots with similar site and environment conditions were established in three types of oak stands. Twenty-two indexes such as stand density, mean DBH, mean height, etc., were selected to analyze the relationship between structural attributes and forest service. With a core set of structural attributes selected by principal component analysis, the link between the service and structural attributes and the compatibility between each service was analyzed using correlation analysis. The results show that the oak–broadleaf mixed forest has the highest structural complexity index (SCI), indicating the best habitat conservation among others, while the oak–pine mixed forest and pure oak forest have the highest timber value in different scenarios of timber price, indicating the largest potential for timber production. Little differences were found between stand types regarding the indicators for soil water conservation. The structural attributes that had a positive correlation with habitat conservation (e.g., number of shrub species, species richness of canopy layer, the proportion of broadleaves and snag density) were identified to be negative for timber production; while the attributes that had a positive correlation with timber production (e.g., stand density and proportion of pine and oaks) were found to be negative for habitat conservation. The results of the trade-off analysis showed that timber production tends to be conflicting with the other two non-timber forest services. In order to enhance the provisioning of multiple services, it was suggested to implement the interventions that could balance these services, such as structural retention and single-tree selective logging. This study could contribute to the theoretical base for the decision making in the multi-purpose sustainable management of oak forests in China.

Decadal trends in 137Cs concentrations in the bark and wood of trees contaminated by the Fukushima nuclear accident

Understanding the actual situation of radiocesium (137Cs) contamination of trees caused by the Fukushima nuclear accident is essential for predicting the future contamination of wood. Particularly important is determining whether the 137Cs dynamics within forests and trees have reached apparent steady state. We conducted a monitoring survey of four major tree species (Japanese cedar, Japanese cypress, konara oak, and Japanese red pine) at multiple sites. Using a dynamic linear model, we analyzed the temporal trends in 137Cs activity concentrations in the bark (whole), outer bark, inner bark, wood (whole), sapwood, and heartwood during the 2011–2020 period. The activity concentrations were decay-corrected to September 1, 2020, to exclude the decrease due to the radioactive decay. The 137Cs concentrations in the whole and outer bark samples showed an exponential decrease in most plots but a flat trend in one plot, where 137Cs root uptake is considered to be high. The 137Cs concentration ratio (CR) of inner bark/sapwood showed a flat trend but the CR of heartwood/sapwood increased in many plots, indicating that the 137Cs dynamics reached apparent steady state within one year in the biologically active parts (inner bark and sapwood) and after several to more than 10 years in the inactive part (heartwood). The 137Cs concentration in the whole wood showed an increasing trend in six plots. In four of these plots, the increasing trend shifted to a flat or decreasing trend. Overall, the results show that the 137Cs dynamics within forests and trees have reached apparent steady state in many plots, although the amount of 137Cs root uptake in some plots is possibly still increasing 10 years after the accident. Clarifying the mechanisms and key factors determining the amount of 137Cs root uptake will be crucial for predicting wood contamination.

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.

Movement, spatial ecology, and habitat selection of translocated Gould's wild turkeys

AbstractTranslocations have aided restoration of wild turkeys (Meleagris gallopavo) across North America and are used to help establish sustainable, local populations even now. Because successful restocking relies on individuals remaining close to the release site to reduce movement‐based mortalities, a close examination of behaviors and factors affecting site selection can improve survival of translocated birds and enhance translocation success. Therefore, we assessed movements and habitat selection following translocation of 16 Gould's wild turkeys (M. g. mexicana) radiotagged with GPS‐VHF transmitters in Arizona. We assessed daily distance traveled, range size, distance from release site, and habitat selection from release to 120 days post‐release. Turkeys increased space use ~35 days post‐release. After 70 days post‐release, individuals shifted their behaviors to exploitation and individual maintenance, which was characterized by decreasing movements and space use. Turkeys had high release site fidelity and remained 1,352.2 ± 318.7 m (x̄ ± SE) from the release site 120 days post‐release. Distance between daily roost sites stabilized around day 50, and turkeys were within 89.8 ± 49.9 m (x̄ ± SE) of the previous night's roosting site by day 120. Gould's wild turkeys selected for riparian areas throughout the study period and selected for pine (Pinus spp.)‐juniper (Juniperus spp.) woodland for the first 60 days post‐release; thereafter pine‐juniper woodland was used in proportion to availability. Gould's wild turkeys used open‐herbaceous areas and pine–oak (Quercus spp.) woodland in proportion to availability. Our results indicate that Gould's wild turkeys take about 70 days to integrate into a new local environment following translocation, and riparian areas are a critical component of Gould's wild turkey habitat within the southwestern United States. Managers should ensure riparian areas are protected and restored before translocating Gould's wild turkeys to facilitate translocation success and persistence of Gould's wild turkey populations.

Habitat-linked genetic variation supports microgeographic adaptive divergence in an island-endemic bird species.

We investigated the potential mechanisms driving habitat‐linked genetic divergence within a bird species endemic to a single 250‐km2 island. The island scrub‐jay (Aphelocoma insularis) exhibits microgeographic divergence in bill morphology across pine–oak ecotones on Santa Cruz Island, California (USA), similar to adaptive differences described in mainland congeners over much larger geographic scales. To test whether individuals exhibit genetic differentiation related to habitat type and divergence in bill length, we genotyped over 3000 single nucleotide polymorphisms in 123 adult island scrub‐jay males from across Santa Cruz Island using restriction site‐associated DNA sequencing. Neutral landscape genomic analyses revealed that genome‐wide genetic differentiation was primarily related to geographic distance and differences in habitat composition. We also found 168 putatively adaptive loci associated with habitat type using multivariate redundancy analysis while controlling for spatial effects. Finally, two genome‐wide association analyses revealed a polygenic basis to variation in bill length with multiple loci detected in or near genes known to affect bill morphology in other birds. Our findings support the hypothesis that divergent selection at microgeographic scales can cause adaptive divergence in the presence of ongoing gene flow.

Microbial extracellular enzyme activity with simulated climate change

It is critical to understand the consequences of environmental change for the microbial regulation of carbon and nutrient cycling. Specifically, understanding microbial community traits, such as extracellular enzyme activity, can help inform nutrient cycling models and address knowledge gaps. We analyzed data on extracellular enzyme activities and litter decomposition from an 18-month experiment in which microbial communities were reciprocally transplanted along a climate gradient in Southern California. Communities were from desert, scrubland, grassland, pine–oak, and subalpine ecosystems. We aimed to test how enzyme activities responded to climate change following transplantation and how those responses related to decomposition rates. We hypothesized that microbial communities would specialize on their native climate conditions, resulting in higher enzyme activities when transplanted back into their native climate. We investigated the relationship between extracellular enzyme Vmax values, substrate mass loss, and microbial biomass as well as variation in these variables across the climate gradient. We found little evidence for climate specialization, and there was rarely a reduction in enzyme functioning after microbial communities were transplanted into new climate conditions. Moreover, observed differences in decomposition were not related to changes in extracellular enzyme potential, although there were significant differences in enzyme activities and decomposition rates across sites. These results suggest that direct, physiological impacts of climate are likely to be important for enzyme-mediated decomposition, but climate specialization will not constrain the microbial response to climate change in our system.

Live Fences as Refuges of Wild and Useful Plant Diversity: Their Drivers and Structure in Five Elevation Contrast Sites of Veracruz, Mexico

Background and Research One noteworthy element found throughout the tropical anthropogenic mosaic is the live fence, which is established within agricultural matrices and its structure within the landscape retains ecological processes, but few are recognized as elements of biological and cultural conservation. Methods In this study, we have researched plant diversity and anthropic management of live fences in five sites surrounded by contrasting vegetation references: Tropical evergreen forest; tropical deciduous forest; cloud forest; and pine–oak and pine forests. We recorded the type of management by interviews with peasants. We established thirty 2 × 50 m transects within each site and sampled two strata: trees and saplings. Also, we documented seed dispersal mechanism, life form, local use, and origin of each species. Importance Value Index and diversity metrics were estimated for each site. Results 253 plant species were registered (181 genera/74 families). While fences associated with the tropical deciduous forest showed the greatest species richness (109 species), the pine forest fences showed the lowest richness (21 species). Zoochory was the main type of seed dispersal mechanism. Conclusions Independent to the site and the altitude, the configuration of living fences is structured by three processes: the selection of the initial trees, the availability of the arrival of zoochory species, and the tolerance of the owners for the plant species. Implications for Conservation Based on our results, live fences can be considered important tools for landscape management in Mexico.

Polycyclic aromatic hydrocarbons accumulation in soil horizons of different temperate forest stands

AbstractPollution due to polycyclic aromatic hydrocarbons (PAHs) is a serious environmental issue. The aim of this study was to determine the effect of stand species composition on PAH content. The research covered the stand soils of the Rybnik Forest District, which experiences some of the highest deposition of industrial emissions in Europe. Pine, pine–oak and oak stands growing in the same soil conditions were selected for the study. Samples for further analyses were collected from the organic, humus mineral and mineral soil horizons. The organic C and N concentrations, pH, alkaline cation content, microbiological biomass of C and N, soil enzyme activity, soil organic matter (SOM) fractions and PAH content were determined. The oak stand soils were characterised by the lowest accumulation of PAHs (2936.0 μg kg−1) with high biochemical activity expressed by enzyme activity (dehydrogenases, N‐acetyl‐β‐d‐glucosaminidase, phosphatase) and high microbiological biomass. In contrast, pine stand soils are acidified; hence, SOM decomposition is slowed, resulting in a high accumulation of PAHs (3805.0 μg kg−1). A strong correlation (r = 0.825) between PAH accumulation and SOM free light fraction (fLF) C concentration was noted. The stand species composition plays an important role in shaping the quality and quantity of SOM and soil acidification, which is reflected in the microbial activity and PAH accumulation in forest soils. Such accumulation in forest soils is related to the fractional composition of SOM, which is due to the influence of species composition through the supplied biomass.