Pine-oak Woodlands Research Articles

Differentiating Historical Open Forests and Current Closed Forests of the Coastal Plain, Southeastern USA

The southeastern United States was historically characterized by open forests featuring fire-adapted species before land-use change. We compared tree composition and densities of historical tree surveys (1802 to 1841) to contemporary tree surveys, with the application of a similarity metric, in the Coastal Plain ecological province of Mississippi, southeastern USA. We detected the boundary between historical pine and oak-pine open forests and differentiated historical and current forests. In the Coastal Plain, historical open forests converted from fire-tolerant longleaf pine (Pinus palustris) dominance, with pines comprising 88% of all trees, to loblolly (Pinus taeda) and slash (P. elliottii) pines within monocultures (45% of all trees). Wetland and successional tree species increased to 33% of all trees. Contemporary forests have greater tree densities, transitioning from closed woodlands (range of 168 to 268 trees ha−1) to closed forests (336 trees ha−1). In the ecotonal boundary of the northern Coastal Plain between historical pine and pine-oak woodlands, the pine component shifted over space from 88% to 34% of all trees due to a greater oak component. Fire-tolerant shortleaf pine and oak dominance converted to planted loblolly pine (52% of all trees), while successional tree species increased (20% of all trees). Historical tree densities represented woodlands (range of 144 to 204 trees ha−1) but developed into closed forests (400 trees ha−1). Historical Coastal Plain longleaf pine woodlands differed more from historical ecotonal oak-pine woodlands than contemporary forests differed from each other, demonstrating unique historical ecosystems and landscape-scale homogenization of ecosystems through forestation.

Discovery of a new tarantula species from the Madrean Sky Islands and the first documented instance of syntopy between two montane endemics (Araneae, Theraphosidae, Aphonopelma): a case of prior mistaken identity.

The Chiricahua Mountains in southeastern Arizona are renowned for their exceptional biodiversity and high levels of endemism. Morphological, genomic, behavioral, and distributional data were used to report the discovery of a remarkable new tarantula species from this range. Aphonopelmajacobii sp. nov. inhabits high-elevation mixed conifer forests in these mountains, but also co-occurs and shares its breeding period with A.chiricahua-a related member of the Marxi species group-in mid-elevation Madrean evergreen oak and pine-oak woodlands. This marks the first documented case of syntopy between two montane endemics in the Madrean Archipelago and adds to our knowledge of this threatened region's unmatched tarantula diversity in the United States. An emended diagnosis and redescription for A.chiricahua are also provided based on several newly acquired and accurately identified specimens. Phylogenetic analyses of mitochondrial and genomic-scale data reveal that A.jacobii sp. nov. is more closely related to A.marxi, a species primarily distributed on the Colorado Plateau, than to A.chiricahua or the other Madrean Sky Island taxa. These data provide the evolutionary framework for better understanding the region's complex biogeographic history (e.g., biotic assembly of the Chiricahua Mountains) and conservation of these spiders.

Cloacal microbiomes of sympatric and allopatric Sceloporus lizards vary with environment and host relatedness.

Animals and their microbiomes exert reciprocal influence; the host's environment, physiology, and phylogeny can impact the composition of the microbiome, while the microbes present can affect host behavior, health, and fitness. While some microbiomes are highly malleable, specialized microbiomes that provide important functions can be more robust to environmental perturbations. Recent evidence suggests Sceloporus virgatus has one such specialized microbiome, which functions to protect eggs from fungal pathogens during incubation. Here, we examine the cloacal microbiome of three different Sceloporus species (spiny lizards; Family Phrynosomatidae)-Sceloporus virgatus, Sceloporus jarrovii, and Sceloporus occidentalis. We compare two species with different reproductive modes (oviparous vs. viviparous) living in sympatry: S. virgatus and S. jarrovii. We compare sister species living in similar habitats (riparian oak-pine woodlands) but different latitudes: S. virgatus and S. occidentalis. And, we compare three populations of one species (S. occidentalis) living in different habitat types: beach, low elevation forest, and the riparian woodland. We found differences in beta diversity metrics between all three comparisons, although those differences were more extreme between animals in different environments, even though those populations were more closely related. Similarly, alpha diversity varied among the S. occidentalis populations and between S. occidentalis and S. virgatus, but not between sympatric S. virgatus and S. jarrovii. Despite these differences, all three species and all three populations of S. occcidentalis had the same dominant taxon, Enterobacteriaceae. The majority of the variation between groups was in low abundance taxa and at the ASV level; these taxa are responsive to habitat differences, geographic distance, and host relatedness. Uncovering what factors influence the composition of wild microbiomes is important to understanding the ecology and evolution of the host animals, and can lead to more detailed exploration of the function of particular microbes and the community as a whole.

Vegetación de la Sierra Madre Occidental, México: una síntesis

La Sierra Madre Occidental (SMO) es el complejo montañoso más grande de México, extendiéndose por casi 1200 km desde el noreste de Sonora (30°35' N) hasta el norte de Jalisco (21°00' N). A pesar de su gran importancia ambiental y económica, es todavía deficientemente conocida. Se presenta una sinopsis de los tipos de vegetación, con datos sobre la superficie que ocupan las comunidades reconocidas, intervalos de elevación y climas donde se localizan, así como un mapa. En la zona confluyen tres regiones, albergando ecosistemas templados y semifríos (región Madrense), semiáridos (Madrense-Xerófila) y cálido-secos (Tropical), respectivamente. La región Madrense, en el macizo de la sierra, incluye bosque de pino, bosque mixto de coníferas, bosque de pino-encino, bosque de encino y manchones de bosque mesófilo de montaña, además de comunidades como chaparral (primario y secundario) y vegetación de claros de bosque. La región Madrense-Xerófila, en el piedemonte norte y oriental y estribaciones al oriente de la sierra, presenta bosque bajo abierto (de encino o de pino-encino), matorral perennifolio y zonas de ecotonía hacia pastizal y matorral xerófilo, además de ecotonías con matorral subtropical hacia el sur del Archipiélago Madrense. En la región Tropical, a lo largo de la base occidental de la sierra e ingresando a esta a través de las barrancas y quebradas, predomina bosque tropical caducifolio y matorral subtropical, con pequeñas áreas de bosque tropical subcaducifolio. La alta diversidad de la SMO se ejemplifica con los tres géneros dominantes fisonómicamente en la vegetación: 24 especies de Pinus (46% del total nacional), 54 de Quercus (34%) y 7 de Arbutus (100%).

Not (only) poison pies - Hebeloma (Agaricales, Hymenogastraceae) in Mexico.

The species of Hebeloma have been little studied in Mexico, but have received attention as edibles and in trials to enhance production of edible fungi and tree growth through inoculation of seedlings with ectomycorrhizal fungi. Here we describe three new species of Hebeloma that are currently known only from Mexico. These species belong to separate sections of the genus: H.ambustiterranum is a member of H.sect.Hebeloma, H.cohaerens belongs to H.sect.Theobromina, while H.magnicystidiatum belongs to H.sect.Denudata. All three species were collected from subtropical pine-oak woodland; all records of H.cohaerens came from altitudes above 2500 m. Hebelomaambustiterranum is commonly sold in the local markets of Tlaxcala as a prized edible mushroom. An additional nine species are reported from Mexico, of which eight are new records for the country: H.aanenii, H.eburneum, H.excedens, H.ingratum, H.neurophyllum, H.sordidulum, H.subaustrale and H.velutipes. First modern descriptions of H.neurophyllum and H.subaustrale, originally described from the USA, are given here.

Rapid Ecological Integrity Assessment Metrics to Restore Wildlife Habitat and Biodiversity for Shortleaf Pine–Oak Ecosystems

Open woodlands dominated by shortleaf pine (Pinus echinata Mill.) and oak are historically an important component of the landscape across the southeastern United States. These ecosystems support numerous wildlife species, many of which have declined in recent years as the amount and condition of their habitat have declined. Land managers and private landowners need guidance on how to efficiently and accurately quantify the condition and wildlife habitat value of the pine stands that they manage. Here we provide a set of rapid assessment metrics, based on NatureServe’s ecological integrity assessment (EIA) method, to (a) identify exemplary tracts that provide the best habitat for key wildlife species, and (b) monitor restoration efforts to assess progress toward the improved quality of existing tracts. To ensure an ecologically appropriate scaling of metrics, we distinguished six types of shortleaf pine–oak woodland: A.—Interior Highlands shortleaf pine–oak (including A.1—shortleaf pine–oak forest and woodlands; A.2—shortleaf pine–bluestem woodlands); B—montane longleaf pine–shortleaf pine woodlands; C—southern Appalachian pine–oak woodlands; D—West Gulf coastal plain shortleaf pine–oak woodlands; and E—southeast coastal plain and Piedmont shortleaf pine–oak woodlands. We relied on a narrative conceptual model and peer review-based indicator selection to identify a core set of 15 stand-level metrics (two were optional). Individual assessment points (thresholds) and ratings (Excellent, Good, Fair, and Poor) were developed that were sensitive to the distinct attributes of each of the five shortleaf pine–oak and Appalachian pine–oak types. Values for the metrics can all be collected using rapid field methods, such as using basal area prisms and ocular (visual) estimates of cover. Protocols for the consistent application of these EIA methods are provided. A case study is presented from the Cherokee National Forest in Tennessee. These methods provide improved and rapid EIA metrics for all shortleaf pine–oak ecosystems in the southeastern US to help guide conservation-minded landowners in assessing the biodiversity and priority wildlife values of shortleaf pine–oak and southern Appalachian pine–oak ecosystems.

Even Simple Habitat Ontologies are Hard to Use

An essential component in describing, delimiting, and understanding the evolutionary context of a taxon is characterizing the habitats in which the taxon is found. We report on a simple habitat ontology that we have developed, and on our ongoing experience using volunteers to annotate legacy habitat descriptions with terms from the ontology. Our botanical informatics group is building the Canadian Flora Commons, a knowledge platform to aggregate, integrate and facilitate collaboration on information about Canadian plants. Species pages in the Commons are seeded with structured data extracted from authoritative sources such as the Flora of North America (FNA), Flora of British Columbia, etc. In previous TDWG talks (e.g., Sachs et al. 2019), we described our workflow for extracting and structuring morphological data. To understand why habitat descriptions are different and pose a unique set of challenges, consider the following (from Plectocephalus rothrockii in FNA): “Damp soil near streams, roadsides, open pine-oak woodlands and forests”. Here, the single field “habitat” is used to capture environmental conditions, canopy coverage, and taxonomic associations. We also find it often used for geology, climate, etc. Information in the habitat field is often detailed, but it is presented in free text with little editorial guidance, and comparison between treatments within a given flora and among floras is challenging. Environment ontologies that could aid in the standardization of habitat descriptors exist, notably ENVO (ENVironment Ontology; Buttigieg et al. 2016). However, ENVO’s goals have been primarily focused on describing the biomes, environmental features and environmental materials of molecular datasets, resulting in an ontology that thus far does not serve our needs. To our knowledge, no habitat ontology exists that supports species-level use cases (but see the habitat classification scheme developed by the IUCN). To address this, we developed a small and simple habitat ontology by examining over 3000 habitat descriptions across multiple families, and asked “what is the author trying to tell us?”. In our taxonomic treatment authoring tool, being developed as part of another project, we will use this ontology to replace or supplement the single “habitat” field with multiple habitat dimensions (“soil type”, “canopy coverage”, etc.), some with controlled vocabularies (e.g. {open, closed, partial} for canopy coverage). We are also “translating” legacy habitat descriptions into instance data for the ontology. This is a time-consuming process and has the potential to be dependent on interpretations made by the translator. The crowdsourcing experiment described below is aimed at addressing the first issue and quantifying the second. With our centre's support, we recruited a team of volunteers (6–8 at any given time), and taught them how to annotate habitat descriptions with WebProtegé (Horridge et al. 2014). We divided volunteers into two groups, with each group working with the same dataset, so that we could compare results. While a purpose-built habitat ontology offers advantages over existing environment ontologies and a consensus was reached on habitat class definitions (e.g., moisture, elevation, canopy coverage), we discovered that it is difficult to achieve consensus on the application of habitat classes. Between the two groups, shared annotations represented 57% of the total annotations added to terms and phrases and unique annotations represented 43%. This aligns with previous efforts to build a controlled vocabulary for FNA treatments, where differences between term categorizations represented 49% of the effort (Endara et al. (2017)). Amongst classes in our ontology, unique annotations varied between 11% and 76% (see Fig. 1). Our talk will describe our findings, discuss the subjectivity of habitat classes and other difficulties we’ve encountered while building our ontology, and demonstrate the power of a habitat-driven search interface. This interface will live alongside parsed morphological descriptions (see dev.floranorthamerica.org). We invite collaboration towards increasing the robustness and applicability of the ontology.

Genetic and morphological differentiation among populations of the Rivoli’s Hummingbird (Eugenes fulgens) species complex (Aves: Trochilidae)

AbstractGenetic variation and phylogeographic studies have been crucial for understanding mechanisms of speciation. We analyzed genetic variation and phylogeography to reconstruct the demographic history of the Rivoli’s Hummingbird (Eugenes fulgens) species complex and also evaluated their morphological differentiation. This widely distributed species inhabits the highlands of Mexico and northern Central America, with 2 subspecies separated by the Isthmus of Tehuantepec (west: E. f. fulgens, east: E. f. viridiceps). We surveyed genetic variation in 2 mitochondrial DNA markers (mtDNA, with 129 individuals) and nuclear DNA (6 microsatellites, with 85 individuals). We also inferred the demographic history, estimated divergence times, and analyzed morphological variation using 470 vouchered specimens. We modeled the current potential distribution of the species using ecological niche modeling and projected it into the past to model the effects of the Pleistocene climatic cycles. Haplotype networks, pairwise FST comparisons, AMOVA, and morphological analysis revealed differences between geographically isolated populations separated by the Isthmus of Tehuantepec (IT; corresponding to the 2 recognized subspecies: fulgens and viridiceps), and by the Motagua-Polochic-Jocotán (MPJ) system fault. Demographic scenarios revealed a contraction in distribution during the last interglacial, and expansion during the Last Glacial Maximum (LGM) with little change since the LGM. Divergence between groups separated by the Isthmus of Tehuantepec ~59,600 yr ago occurred in the presence of gene flow, suggesting that the Isthmus of Tehuantepec is a semipermeable barrier to gene flow. STRUCTURE analyses of microsatellite data detected 3 genetically differentiated groups. Several results fit a model of recent lineage divergence, including a significant signal of genetic differentiation, demographic expansion, decreased gene flow from past to present, and northward expansion during the LGM and contraction during the interglacial periods. We conclude that the genetic differentiation of E. fulgens in the Madrean Pine-Oak Woodlands resulted from recent geographical isolation of populations separated by natural barriers (IT and MPJ).

Trend and variability of NDVI of the main vegetation types in the Cape Region of Baja California Sur

The Cape Region (CR) of Baja California Sur is located in the southernmost tip of the Baja California peninsula, Mexico. The vegetation of this region is dominated by scrubland (SRB) and tropical dry forest (TDF), but oak (OW) and oak-pine woodland (OWP) are also found in Sierra La Laguna Biosphere Reserve. These vegetation types, in this relatively small area, make the CR a contrasting and highly biodiverse region. This research used the Normalised Difference Vegetation Index (NDVI) to describe spatiotemporal variability of the vegetation cover in the CR. The analysed NDVI data derived from Landsat 7 during the growing season (September-November) from 2001-2015. Its spatial distribution showed the highest values in the TDF, OW and OPW. Higher variability was observed in SRB. Temporal variations of the annual NDVI mean of the growing season fluctuated in a range from 0.292 to 0.522, and with the highest values in 2014 while the lowest were observed in 2011. A general increasing trend was observed for the growing season over the period 2001-2015 for all analysed vegetation types. Remote sensing change detection methods combined with Geographic Information Systems, suggested that the vegetation of the area was well conserved during the period of study.

Differences in leaf physiology among juvenile pines and oaks following high-severity wildfire in an Arizona Sky Island Mountain range

Recent increases in wildfire severity are converting pine-oak (Pinus-Quercus) woodland to oak shrubland in many sites in the southwestern United States. A key mechanism underlying this transition is the vigorous resprouting capacity of oaks compared to low regeneration rates in pines following wildfire. Differences among species in leaf physiological characteristics may also contribute to such vegetation type conversions, especially in the context of recent increased regional aridity. To that end, we evaluated variation in leaf functional traits in post-fire recruits five years after the 2011 Horseshoe Two in the Chiricahua Mountains, Arizona, USA. We measured a suite of functional traits in two pines (Pinus engelmannii and P. leiophylla) and two oaks (Quercus hypoleucoides and Q. arizonica), including leaf gas exchange, leaf pigment concentrations, leaf spectral reflectance, and wood xylem δ13C, δ18O isotopes, and integrated water use efficiency (iWUE). The four study species displayed a range of plant functional traits tied to desiccation tolerance. P. engelmannii seedling recruits presented invariably low maximum photosynthetic rate (Amax), stomatal conductance (gs), and transpiration (E), and high relative leaf water content during the peak of the May-June drought, a response strongly indicative of a desiccation-avoidant leaf that prioritizes water conservation over carbon fixation in arid conditions. In contrast, resprouts of both oaks displayed leaf desiccation tolerance, with high levels of gs and E and low relative leaf water content. Gas exchange in P. leiophylla resprouts was more similar to the oaks, except for relative water content, which was similar to that of P. engelmannii. Compared to the other two species, P. engelmannii and Q. hypoleucoides exhibited significantly higher δ13C, δ18O and iWUE values—a pattern that appears to have arisen from different mechanisms in the two species. In desiccation-avoidant P. engelmannii, low instantaneous gs and high δ18O suggested that low stomatal conductance rather than high photosynthetic rates led to high iWUE, whereas lower δ18O and very high pigment concentrations in Q. hypoleucoides suggest a more important role for Amax in this species. Neither fire severity nor physiography influenced the physiological responses in any of the four species, suggesting that the expression of resprout and seedling functional traits is fixed. These results raise the possibility that differences in leaf physiological characteristics contribute to the regeneration success of some oak species and the poor seedling establishment of obligate seeder pines, such as P. engelmannii, after high-severity wildfire in the American Southwest.

A new species of Aphonopelma (Araneae: Mygalomorphae: Theraphosidae) from the Madrean pine-oak woodlands of northeastern Sonora, Mexico

The tarantula spider genus Aphonopelma Pocock, 1901 has received considerable attention in recent years but the group's diversity remains poorly understood in Mexico, particularly in the pine-oak woodlands of the Sierra Madre Occidental and associated Madrean "Sky Islands". A pair of tarantulas discovered from an unsampled region in the Sierra de Bacadéhuachi (the westernmost range of the Sierra Madre Occidental) in northeastern Sonora was found to be closely related to four species from the Madrean "Sky Islands" in Arizona and New Mexico. An integrative approach for delimiting species (incorporating data from molecular phylogenetics, morphology, distributions, and breeding periods) suggests that the specimens from Sierra de Bacadéhuachi belong to an undescribed species that is herein named Aphonopelma bacadehuachi sp. nov. This new species adds to our knowledge of an increasingly diverse assemblage of Aphonopelma from the Madrean Pine-Oak Woodlands Hotspot. Collaborations between Mexican and American researchers are needed to accelerate discovery and description of the group's remaining diversity, particularly in light of the many threats facing the ecoregion including habitat degradation and climate change.

Reproductive ecology of Gould's Wild Turkeys (Meleagris gallopavo mexicana) in Arizona

Gould's Wild Turkeys (Meleagris gallopavo mexicana) are the least-studied subspecies of Wild Turkey. Restoration efforts to establish sustainable populations of the subspecies continue throughout portions of the historical range in New Mexico and Arizona. Wild Turkey population viability is driven by reproductive success, yet information on aspects of the reproductive ecology of Gould's Wild Turkey is either scant or nonexistent. We used GPS telemetry to detail reproductive ecology of 23 females during 2017 in southeastern Arizona. We observed a nest initiation rate of 65% and nest success of 58%. Average estimated date for the onset of laying for initial nests was 17 May, which was later than for other subspecies of Wild Turkey. Estimated clutch size (x = 5.6 eggs) across 14 nests and vegetative characteristics at nests were comparable to nest sites selected by Eastern and Rio Grande subspecies, but did not appear to influence nest fate. Mean size of incubation recess ranges was 21 ha (SD = 99), but was highly variable across individual females and we found no evidence of habitat sampling by female Gould's Wild Turkeys before initiating laying of eggs. Females used open/herbaceous habitats and pine-oak woodlands throughout the reproductive period but type of conditions used varied between the laying, incubation, and brooding period. While based on 1 year of field data, our work represents the only assessment of the reproductive ecology of the Gould's Wild Turkey in the United States and should prompt further investigations into the biology of this iconic southwestern species.

Understory Vegetation Responses to 15 Years of Repeated Fuel Reduction Treatments in the Southern Appalachian Mountains, USA

Decades of fire exclusion in the Southern Appalachian Mountains led to fuel accumulation and conversion from open oak-pine woodlands to closed-canopy mesic forests dominated by shade-tolerant hardwoods and shrubs that often do not support a diverse understory. Southern Appalachian forest managers and scientists recognize this and are implementing silvicultural treatments such as prescribed burning, mechanical treatments or a combination of these to restore forest structure. In this study, conducted at the Southern Appalachian Fire and Fire Surrogate Study site in Green River Game Land, North Carolina, we assessed the effects of four fuel reduction methods: burned 4x (B), mechanical treatment 2x (M), mechanical treatment 2x + burned 4x (MB), and control (C) on the changes in understory vegetation guilds from pretreatment to post-treatment years (2001–2016). The MB treatment was most effective at meeting the restoration objectives, as it resulted in increases in oak (ΔMB = 23,400 stems/ha) and pine (ΔMB = 900 stems/ha) stem density, importance value - calculated as the sum of relative cover and frequency - for graminoids (ΔMB = 26.0), and density of oak stems >50 cm in height (ΔMB = 7133 stems/ha). The B and M treatments were generally less effective, but nonetheless met a subset of the restoration objectives. The B treatment reduced ericaceous shrub cover (ΔB = −1.2%) and increased oak stems 10–50 cm in height (ΔB = 10,017 stems/ha), while the M treatment resulted in only modest increases of mesic hardwoods, specifically for yellow-poplar (ΔM = 200 stems/ha) and blackgum (ΔM = 200 stems/ha) as compared with other treatments, but significantly increased mountain laurel and rhododendron cover (ΔM = 10.0%). Overall, these fire and fire surrogate treatments had some success in restoring understory structure, but our findings suggest a slow response in understory herbaceous vegetation.

INFLUENCIA DEL FUEGO SOBRE LA RIQUEZA Y DIVERSIDAD DE AVES EN UN BOSQUE TEMPLADO EN PUEBLA


 
 
 Desde el punto de vista ecológico, los incendios tienen efectos positivos sobre la vida silvestre y su hábitat en ecosistemas mantenidos por el fuego y bajo regímenes poco alterados. En México prácticamente no se ha estudiado su impacto en la avifauna. En el presente trabajo se evaluó su influencia en la riqueza y diversidad de aves en un bosque de encino-pino de Chignahuapan, Puebla, bajo tres condiciones: 1a. No quemado recientemente (más de cinco años, C1); 2a. Quemado un año antes a baja severidad (C2) y 3a. Quemado un año antes con alta severidad (C3). Para llevar a cabo el muestreo, se aplicaron los métodos de parcelas circulares y de red de niebla, además, se siguieron las claves correspondientes para identificación de avifauna. Los resultados condujeron al registro de 30 especies de aves, pertenecientes a seis órdenes y 20 familias; 22 de dichas especies se agrupan en C1, 12 en C2 y 10 en C3. Se estimó la diversidad de la avifauna con el índice de Shannon-Wiener para cada condición. Con base en la prueba t Hutchenson, se verificaron diferencias en diversidad entre C2 (2.079) y C3 (1.040) a partir de la red de niebla; y, con las parcelas circulares, C1 (2.198) difirió de C3 (1.850). Con base en los resultados encontrados, se concluye que el fuego es un factor ecológico que provoca cambios importantes en la diversidad y riqueza de aves a corto plazo.
 
 

Effects of pine-oak woodland restoration on breeding bird densities in the Ozark-Ouachita Interior Highlands

Restoration is underway to restore lost or degraded remnants of savanna and woodland in the Midwestern United States in the hopes of restoring floristic and wildlife diversity. Information is needed on the effects of pine savanna-woodland restoration on bird abundance to inform management decisions. We conducted point-count surveys for 19 bird species across the gradient of savanna, woodland, and forest in restored and non-restored areas throughout the Ozark-Ouachita Highlands in parts of Missouri, Arkansas, and Oklahoma during the 2013–2015 breeding seasons. We estimated densities of 16 species using distance sampling to account for detection probability, and we determined relationships of bird abundance with management and vegetation variables by evaluating support for a priori models. Densities of early-successional and generalist species were positively related, and interior-forest species negatively related, to restoration. Densities of Brown-headed Nuthatch (Sitta pusilla), Eastern Towhee (Pipilo erythrophthalmus), Eastern Wood-Pewee (Contopus virens), Pine Warbler (Setophaga pinus), Prairie Warbler (Setophaga discolor), Red-headed Woodpecker (Melanerpes erythrocephalus), White-eyed Vireo (Vireo griseus), and Yellow-breasted Chat (Icteria virens) were positively related to prescribed fire activity. Blue-winged Warbler (Vermivora cyanoptera), Kentucky Warbler (Geothlypis formosa), and Yellow-breasted Chat densities were positively related to tree thinning. Many species had higher densities in areas with less canopy cover, tree density, and forest cover. Acadian Flycatcher (Empidonax virescens), Black-and-white Warbler (Mniotilta varia), Ovenbird (Seiurus aurocapilla), Wood Thrush (Hylocichla mustelina), and Worm-eating Warbler (Helmitheros vermivorum) were negatively related to one or more aspects of restoration treatment and generally preferred areas with greater tree density and canopy cover. Summer Tanagers (Piranga rubra) were abundant but density was not strongly related to management or vegetation variables. Restoration provided breeding habitat for disturbance-dependent species and woodland generalists, many of which are species of conservation concern, but canopy cover generally remained too great for species that require more open savanna.

Host preference of ectomycorrhizal fungi in mixed pine–oak woodlands

Many ectomycorrhizal fungi (EMF) are generalists, but most plant genera that form ectomycorrhizas have at least some fungal partners that are specific to that host genus. Because shared mycorrhizal fungi mediate plant community interactions, host preference has implications for plant succession and competition. We studied the EMF of oaks (Quercus spp.) and pines (Pinus spp.) in a forest in northern Florida, USA, focusing on symbionts shared with longleaf pine (Pinus palustris Mill.). Longleaf pine is an important species in the southeastern USA, both for timber plantations and for restoring savanna and woodland habitat. However, we found no research on the composition of naturally occurring EMF on longleaf pine roots. A lower proportion of EMF operational taxonomic units (OTUs) were found colonizing both oaks and pines than expected, providing evidence of host preference within the community. Although most EMF were detected only on either oaks or pines, the OTUs found on both tended to be frequently occurring and abundant. Cenococcum OTUs were found to be significantly associated with oaks, an unexpected finding as this genus is widespread, with a broad host range. These results suggest that host preference of EMF may structure EMF communities and therefore influence ecosystem effects of mycorrhizal networks.

Epilithic diatom communities of selected streams from the Lerma-Chapala Basin, Central Mexico, with the description of two new species.

The Lerma-Chapala Basin, in Central Mexico, is geologically heterogeneous, climatically diverse and boasts high biodiversity, lying within two Biodiversity Hotspots, namely Mesoamerica and the Madrean Pine–Oak Woodlands. Epilithon and water samples were collected in the basin from 14 sampling sites three times each, two sampling campaigns during the rainy season and one in the dry season. A total of 274 infrageneric taxa in 48 genera were recorded. The taxonomic composition observed was dominated by taxa from the genera Nitzschia, Gomphonema, Pinnularia, Navicula, Sellaphora and Eunotia. About a third of the taxa found could not be identified to the species level. From those unidentified morphodemes, two are described as new species, namely Brachysira altepetlensis and Sellaphora queretana. Furthermore, Eolimna rhombica is transferred to Sellaphora. Canonical Correspondence Analysis (CCA) revealed that specific conductivity and pH were the main environmental factors driving the community composition observed. Three groups of samples were identified after the CCA: 1) characterized by acidic waters and low conductivity; 2) with circumneutral waters, low specific conductivity and high temperature and phosphorous concentrations; and 3) characterized by circumneutral waters, high conductivity and low nitrogen concentrations. The indicator value method (IndVal), based on the relative abundance and relative frequency of the most abundant taxa was calculated based on the groups observed in the CCA, identifying the characteristic taxa for each of the three groups.

How can prescribed burning and harvesting restore shortleaf pine-oak woodland at the landscape scale in central United States? Modeling joint effects of harvest and fire regimes

Abstract Historical fire regimes in the central United States maintained open-canopy shortleaf pine-oak woodlands on xeric sites. Following large-scale harvest and fire suppression, those woodlands grew denser with more continuous canopy cover, and they gained mesic species at the expense of shortleaf pine. There is high interest in restoring shortleaf pine-oak woodlands; most have been converted to other forest types but those that remain are valued for high stand-scale and landscape-scale diversity. Prior stand-scale studies suggest that prescribed burning and harvesting could be effective for restoring pine-oak woodlands. However, previous short-term, stand-scale studies provided little insight into long-term, landscape-scale outcomes. To estimate outcomes of alternative restoration treatments on future species composition and forest structure, we employed an integrated field and modeling approach to simulate effects of prescribed burning and harvesting on the restoration of shortleaf pine-oak woodland composition and structure in the Mark Twain National Forest for a 100-year period. Six scenarios were modeled: no management, burn only, harvest only, and a combination of harvest with burns treatments followed by fire-free intervals of differing starting times or durations to facilitate regeneration recruitment. Both no management and prescribed burn only scenarios cannot restore current forest to historical woodland condition (i.e., 40–80% percent canopy cover or less than 55% stocking); however, scenarios including harvest can restore current forest to woodland condition in late 2020s. Under a no management scenario, total basal area would increase to a maximum around 31 m 2 ha −1 , and white oak group remained the most dominant species group throughout the simulation. Under the burn only treatment, total basal area was not reduced substantially as compared to that under no management scenario, however, there were small increases in the basal area and density of shortleaf pine. All of the treatments that included a combination of burning and harvesting reduced total basal area, which fluctuated around 13 m 2 ha −1 throughout the simulation than those under no management and prescribed only scenarios. The simulations suggested that shortleaf pine would become the most dominant group, followed by white, red oak groups, and other species with combined prescribed burning and harvesting. When coupled with harvest, the prescribed burning regime affected species composition: increasing the number of burns increased the basal area and density of shortleaf pine and decreased the basal area and density of white oak group species.

Comparative Nest-Site Habitat of Painted Redstarts and Red-Faced Warblers in the Madrean Sky Islands of Southeastern Arizona

Conservation of avian species requires understanding their nesting habitat requirements. We compared 3 aspects of habitat at nest sites (topographic characteristics of nest sites, nest placement within nest sites, and canopy stratification within nest sites) of 2 related species of ground-nesting warblers (Red-faced Warblers, Cardellina rubrifrons, n = 17 nests; Painted Redstarts, Myioborus pictus, n = 22 nests) in the Sky Island mountain ranges of southeastern Arizona. These species nested in several forest and woodland cover types that occurred along an elevational gradient. Red-faced Warblers nested primarily toward the upper end of that gradient, in pine (Pinus spp.)—oak (Quercus spp.) and mixed-conifer forests. Painted Redstarts nested primarily at lower elevations, in riparian forest, oak-pine woodlands, and pine-oak forest. The 2 species both nested in cover types that occurred at mid-elevations. Within these shared cover types, Red-faced Warblers nested at higher elevations and at nest sites with greater canopy cover >10 m aboveground than Painted Redstarts. Nest placement within nest sites was similar between species; both placed their nests in concealed locations. Our results suggest that managers should consider the entire elevational gradient surveyed here to best conserve habitat for both species, and should maintain at least some areas with relatively dense understory cover across that gradient to provide cover for nest sites. Managers should emphasize lower overstories in lower-elevation oak-pine woodlands, taller overstories in higher-elevation pine-oak and especially mixed-conifer forests, and a mixture of overstory heights in mid-elevation pine-oak forests. We recommend additional detailed studies of nesting habitat and the effects of disturbance processes on nesting habitat. Such studies will add to our understanding of the ecology of these 2 bird species and habitat conservation in this ecologically important area.

Effect of initial seedling size, understory competition, and overstory density on the survival and growth of Pinus echinata seedlings underplanted in hardwood forests for restoration

There is interest in restoring shortleaf pine (Pinus echinata) in pine–oak woodlands where it once was abundant. Because of its shade intolerance and slow initial growth rate, shortleaf pine restoration has remained a challenge because competition from hardwoods exhibits greater initial growth following canopy removal but greater shade tolerance with canopy retention. The study objective was to examine the survival and growth of underplanted shortleaf pine seedlings relative to competing hardwoods as a function of initial seedling size, overstory density, and understory competition. In the Ozark Highlands of southeastern Missouri, USA, 48, 0.4-ha experimental units were each harvested from below to a uniform stocking level from 0 to 90 % and 30, 1–0 improved shortleaf pine seedlings were planted on a 3.7 × 7.3 m spacing. Linear or logistic regression was used to determine how shortleaf pine seedling (1) survival, (2) basal diameter growth, and (3) shoot growth were related to initial seedling size, overstory stocking, and understory competitor height during the first 5 years after underplanting. After five growing seasons, the survival rate of shortleaf pine seedlings was 50 % and was positively related to the initial basal diameter but was not related to overstory stocking or competitor height. Increasing overstory stocking decreased the basal diameter and height growth of shortleaf pine seedlings, explaining >51 % of the variation in basal diameter and 54 % of the variation in seedling height. Although competing hardwood seedlings were consistently taller than the shortleaf pine seedlings throughout the study, shortleaf pine seedlings maintained similar growth rates as competitors from the second to the fifth growing season. The eventual release of shortleaf pine is essential for recruitment, but releases can be delayed for several years after underplanting.