Herbaceous Understory Research Articles

Carbon stock estimation in halophytic wooded savannas of Uruguay: An ecosystem approach

Savannas constitute a mixture of trees and shrub patches with a more continuous herbaceous understory. The contribution of this biome to the soil organic carbon (SOC) and above-ground biomass (AGB) carbon (C) stock globally is significant. However, they are frequently subjected to land use changes, promoting increases in CO2 emissions. In Uruguay, subtropical wooded savannas cover around 100,000 ​ha, of which approximately 28% is circumscribed to sodic soils (i.e., subtropical halophytic wooded savannas). Nevertheless, there is little background about the contribution of each ecosystem component to the C stock as well as site-specific allometric equations. The study was conducted in 5 ​ha of subtropical halophytic wooded savannas of the national protected area Esteros y Algarrobales del Río Uruguay. This work aimed to estimate the contribution of the main ecosystem components (e.g., soil, trees, shrubs, and herbaceous plants) to the C stock. Site-specific allometric equations for the most frequent tree species and shrub genus were fitted based on basal diameter (BD) and total height (H). The fitted equations accounted for between 77% and 98% of the aerial biomass variance of Neltuma affinis and Vachellia caven. For shrubs (Baccharis sp.), the adjusted equation accounted for 86% of total aerial biomass. C stock for the entire system was 116.71 ​± ​11.07 ​Mg⋅ha−1, of which 90.7% was allocated in the soil, 8.3% in the trees, 0.8% in the herbaceous plants, and 0.2% in the shrubs. These results highlight the importance of subtropical halophytic wooded savannas as C sinks and their relevance in the mitigation of global warming under a climate change scenario.

Effects of tree canopy on herbaceous understorey throughout the developmental cycle of a temperate mountain primary forest

Temporal dynamics of temperate montane primary forests were described based on data from Central-European nature reserves in the 20th century as a long-term cycle involving tree regeneration, growth, maturation, and disintegration. However, the lack of chronosequences focusing on the herbaceous understory has limited our understanding of plant community dynamics within this developmental cycle. To address questions regarding whether the herbaceous understory follows the cyclic trajectory of the tree layer and if the properties of the tree layer drive the dynamics of the herbaceous understory, we investigated a 19-year chronosequence in ten plots (with five sampling periods) within an unmanaged primary beech-fir forest in the Western Carpathians. The vegetation data from the resampled plots, including herb species frequencies and dendrometric variables, covered a significant portion of the developmental cycle of a single plant community type. The results confirmed the cyclical nature of herbaceous understory development in terms of species composition and diversity trajectories, demonstrating transitions between developmental stages. Diversity was highest during the disintegration stage, with a rapid decline towards the growth stage, followed by a slow recovery as it progressed towards the optimum stage. Temporal responses of individual species, along with ordination analyses, allowed for the separation of taxa associated with the disintegration, growth, and optimum stages, as well as the most stable ones throughout the entire cycle. The proportion of therophytes slightly increased after gap-opening events during disintegration, geophytes were most represented during the growth stage, and hemicryptophytes culminated during the optimum stage. The composition of herb species was significantly affected by the above-ground tree biomass (AGTB), which explained 21.4% of the temporal variability. The sum of the diameter at breast height (Sum of DBH) described an additional 7.2%. The relationship between the frequency of the herbaceous understory and AGTB followed a “U” shape, while the relationship with Sum of DBH was negative and linear. The relationship between the herbaceous understory and the tree overstory is likely driven by competition for light, water, and nutrient resources. These findings provide new insights into the temporal relationships between the herbaceous understory and tree layer development, and they may inspire future studies and management strategies aimed at conserving or enhancing biodiversity in temperate forests.

Red-cockaded woodpecker habitat characteristics associated with partial brood loss in the Upper East Gulf Coastal Plain, USA

Some red-cockaded woodpecker (RCW) Dryobates borealis populations remain understudied. This is notable because management that incorporates population demographics and site characteristics may benefit RCW recovery. The Oakmulgee Ranger District of the Talladega National Forest (Alabama, USA) has no wiregrass Aristida stricta, small forest stand sizes, rolling topography, and contains an understudied RCW population. Our goal in the Oakmulgee was to characterize RCW habitat, possibly identify ways in which habitat differed from other regions, and estimate associations between habitat and reproductive output. We found that 70.2 and 92.5% of sampled stands met recovery standard thresholds for small and large pine basal area (BA) as defined in the United States Fish and Wildlife Service (USFWS) RCW Recovery Plan. While 74.6% of longleaf pine Pinus palustris-dominated stands met the threshold for overstory hardwood canopy composition, 60.0% of loblolly pine P. taeda-dominated stands did not. Few stands met the recommended percentage of herbaceous understory (19.8%) or recommended absence of hardwood midstory. A lower rate of partial brood loss was associated with a greater area of large pines (≥25.4 cm diameter at breast height; DBH), a smaller area of small pines (≥10 and <25.4 cm DBH), a larger area burned in the dormant season, and higher RCW density. In our models, hardwood overstory and midstory did not influence egg or hatchling production. Hardwoods in the Oakmulgee could contribute to unfavorable habitat, as indicated in the USFWS RCW Recovery Plan, as well as relate to variation in habitat across the RCW’s range. Regions of the RCW’s range are understudied, and limited staffing and funding impede advances in understanding and conservation.

A tree-ring record of historical fire activity in a piedmont longleaf pine (Pinus palustris Mill.) woodland in North Carolina, USA

BackgroundLongleaf pine (Pinus palustris Mill.) ecosystems were historically widespread in the North American Coastal Plain and in some southeastern piedmont and montane settings. The naval stores industry, deforestation, and other human activities resulted in an extensive loss (c. 97% loss) of the original woodlands and savannas. Longleaf pine ecosystems are maintained by frequent surface fire which promotes successful regeneration and maintains open canopy conditions and a largely herbaceous understory. Fire regimes (including the frequency and seasonality of fire) likely varied across the entire range of longleaf pine and through time; further research is needed to elucidate this variability.ResultsWe used fire scars in stumps and snags to reconstruct fire history in a piedmont longleaf pine ecosystem in North Carolina. For each tree sampled, we examined multiple cross sections to avoid omission of fire events recorded by smaller fire scars. Our samples revealed evidence of frequent fire (c. 3–4-year fire interval) beginning in the early eighteenth century and extending to the mid-nineteenth century. Fires occurred in the dormant and early earlywood positions of annual rings and were likely human ignited.ConclusionsTo our knowledge, this is the first tree-ring-based fire history in longleaf pine of the piedmont. As such, it offers a rare glimpse into historical fire activity in a now scarce but important ecological setting. More research is needed to develop additional fire chronologies in the piedmont region, including for longer periods of time and for larger spatial areas.

The Herbaceous Understory Plant Community in the Context of the Overstory: An Overlooked Component of Tropical Diversity

Lowland tropical rainforests harbor the most diverse plant communities in the world, but the herbaceous plants of the understory are often overlooked. To address this knowledge gap, we asked to what extent the understory herbaceous community contributes to the species richness and phylogenetic diversity of plant communities by surveying a neotropical rainforest at Los Tuxtlas, Mexico. We used Gentry transects to characterize the woody overstory community, and line-intercepts within the same transects to survey understory herbs and subshrubs. We also used published phylogenies to calculate community phylogenetic diversity with and without the understory stratum. We found that the understory contained a diverse (23 species, or 22.1% of all species surveyed) and phylogenetically distinct plant community dominated by aroids (13 species) and ferns (4 species). Inclusion of the understory stratum increased total species richness by 28.4% but increased phylogenetic diversity by 41.4%. Additionally, in contrast to temperate forests, the understory plant community was much less diverse than the overstory, which contained 81 species > 1 cm dbh (77.9% of all species surveyed). This survey adds to the hitherto small body of literature comparing understory and overstory strata in tropical rainforests and reveals previously overlooked patterns of floristic diversity.

Impact of different storm severity levels and post-storm management on understory vegetation richness, diversity and composition 19–20 years after wind disturbance

The herbaceous understory is a key component of forest biodiversity. Moreover, it holds the capability to alter the dynamics and composition of the overstory. Severe wind disturbance changes the conditions in a forest ecosystem radically, causing alteration of understory characteristics as well. In this paper we analyze impacts of different storm damage levels and post-storm management on understory vegetation richness, diversity and composition in mixed spruce–hardwood forest stands located in hemiboreal Estonia. We examined understory vegetation in moderately damaged (n = 4), heavily damaged (n = 4) and post-storm salvage-logged stands (n = 4) 19–20 years after storm disturbance. Mature mixed spruce–hardwood forests were included as a reference group (n = 4). Study plots were also assessed regarding canopy openness, richness of microhabitats and coverage of woody species. A total of 98 herbaceous and 2 dwarf shrub taxa were found on 208 vegetation quadrats (1 m2 square each). Total coverage of the herb layer and species richness were greatest at salvage-logged plots when compared to other treatments. However, we found no significant effect of treatment on diversity (Shannon’s H’) nor evenness (Pielou’s index) of herbaceous species. Our results indicate that approximately-two decades after wind disturbance, the understory communities differ from each other as a response to different storm damage levels and post-storm management. Compared to control plots, salvage-logged plots demonstrated greatest contrast regarding species composition. Salvage-logged plots had greatest light levels, but lowest estimates for microsite richness and woody species coverage. Moderately damaged plots demonstrated greatest within-group variation regarding light conditions and species composition. Our findings suggest that salvage logging after severe wind disturbance might induce delayed succession toward a closed canopy due to intense understory competition and lack of opportunity-providing microhabitats for tree regeneration.

Fire exclusion and fire return interval affect small mammal populations in longleaf pine forests

Longleaf pine (Pinus palustris) forests are among the most fire-dependent forest types in the world and once dominated much of the southeastern United States. Loss and fragmentation of longleaf pine shrank its distribution to approximately 4% of its historic range; as a result, longleaf pine forests currently receive much conservation and restoration emphasis. In all cases, this emphasis includes prescribed fire. Prescribed fires promote herbaceous understories which maintains habitat for some small mammals, but fires can also result in temporary declines of small mammal populations. Therefore, short return intervals may not allow small mammal populations to recover between fires, and long return intervals may result in declining habitat quality and reduced small mammal abundance. During the first phase of our research, we studied the long-term influence of prescribed fire on small mammals. We annually estimated small mammal abundance and species richness during 2001 – 2014 in eight longleaf pine-dominated plots in southwestern Georgia, USA. Plots were either biennially burned (reference) or had fire excluded during the study. Small mammal species richness was similar in fire-excluded and reference sites. Overall small mammal abundance was greatest in reference plots. Five species were captured with sufficient frequency to justify species-specific analyses. Of these, three (hispid cotton rats, Sigmodon hispidus; oldfield mice, Peromyscus polionotis; and house mice, Mus musculus) were more abundant in reference plots. For the second phase of our research, we reintroduced fire in half of the fire excluded plots (burned during 2015, 2016, and 2017) and began sampling small mammals in three additional plots that were burned annually since 2003. We collected data during 2017 and 2018 for this phase of the research to evaluate small mammal response to four prescribed-fire return intervals (annual growing season burns since 2003, biennial burns since 2001 (reference), fire excluded since 2001, and fire excluded since 2001 and then burned during 2015, 2016, and 2017). Small mammal species richness was not affected by burn interval. Cotton rat abundance was greater in reference plots than in other treatments, whereas cotton mice (Peromyscus gossypinus) and oldfield mice were most abundant in the annually burned treatment. Three prescribed fires occurred in fire reintroduced plots prior to sampling, but these fires were insufficient to restore small mammal abundance to that of annually or biennially burned plots. Our work provides further evidence that fire is important for maintaining habitat for some small mammals and that time between fires has a species-specific effect on small mammal abundances. Thus, manipulating fire return interval is a promising tool for managing relative abundance of small mammals and likely other wildlife.

Effects of frequency and season of fire on a metapopulation of an imperiled butterfly in a longleaf pine forest

AbstractMaintaining fire‐dependent habitat for species of conservation concern often requires a balancing act between the short‐term costs of direct mortality caused by fires and the long‐term benefits of ensuring high‐quality habitat. To reduce risk to threatened populations, land managers may need to adjust the frequency with which they burn sites and, likely, mitigate the short‐term costs of prescribed fires by not burning during a species' life stages that may be especially sensitive to fires. Few, if any, studies have investigated burn regimes for butterflies in longleaf pine forests—a once dominant habitat in the southeast United States—despite a long history and frequent usage of prescribed burns in these ecosystems. We surveyed a recently discovered metapopulation of frosted elfin (Callophrys irus) butterflies residing in longleaf pine forest over seven years at sites across nine management units with differing fire return intervals and fire seasonalities. We observed dramatic population declines after burns, with no adults observed at some sites in subsequent years. Our analyses demonstrate that populations may need at least three to 4 years to recover, and that burns in the spring, when frosted elfin eggs and larvae are found on hostplants, should be avoided if possible. In fact, our model suggests that the largest spring‐burned sites have fewer than 20% of the adult elfins the year following a fire than do sites burned in other seasons. Land managers seeking to conserve frosted elfins and other butterflies with similar life histories may need to burn at times of the year that reduce direct mortality and with fire return intervals that are longer than the one‐ to two‐year intervals recommended by some for maximizing the diversity of the herbaceous understory in longleaf pine forests.

Butterfly Assemblages Associated with Restored Riparian Uplands: Las Vegas Wash, Nevada, USA

The butterfly assemblage found at riparian upland plant restoration areas (after removal of the invasive plant, tamarisk (Tamarix ramosissima Ledebour)) along Las Vegas Wash was examined over four different months. Upland areas were planted with a variety of plants, however, those with a mesquite (Prosopis spp. Linneaus) component contained additional butterfly species relative to other plots. Detrended correspondence analysis demonstrated a gradient of butterfly species that corresponded with mesquite, age of stand, and homogenous areas of tamarisk. Some potential butterfly species went undetected; perhaps because required herbaceous understory plants were absent, or the need for greater densities of the hemiparasitic mistletoe (Phoradendron) (Nutt.) which is utilized by certain butterfly species. A single plot of exotic tamarisk, the near-past dominant shrub of the Wash landscape, was examined. An incursion of the beetle Diorhabda carinulata (Desbrochers), a phytophagous tamarisk control agent, appeared to affect tamarisk nectar production along with butterfly abundance at the plot. Butterfly response to nectar at inadvertent seep areas suggests these features are important for butterfly directed landscape restoration activities. Use of a characteristic butterfly community for identifying goals for upland restoration was valuable in describing end-points that incorporated assets of natural mesquite bosques.

Winners and losers in dryland reforestation: species survival, growth, and recruitment along a 33‐year planting chronosequence

Reforestation in the Lower Rio Grande Valley (LRGV) of Texas began in the 1960s and to date over 6,475 ha of land has been reforested. However, there has been minimal assessment to understand differential species success, compositional trends, and the aboveground carbon sequestration potential of these developing forests. We coupled quantitative planting information of >50 native woody tree and shrub species with surveys of 5,223 stems of 4,606 individuals in a chronosequence of restored forests ranging in age from 1 to 33 years to estimate species‐specific mortality rates, biomass accumulation and recruitment, as well as compositional trends in the herbaceous understory. We show that 7–15 years are required for mortality rates of the transplanted cohort to stabilize to background levels observed in other dry forests. A small number of species, mostly N‐fixing trees with a deep rooting habit, persisted on the landscape beyond 15 years. Even so, aboveground biomass (corrected for differences in initial planting density) accumulated at an average rate of 1.41 Mg ha−1 yr−1 compared to 0.35 Mg ha−1 yr−1 for a fallow old‐field. Species biomass growth rates increased with decreasing mortality, as did the abundance of recruits, suggesting a degree of reproduction by initial planted cohorts. However, a suite of highly competitive exotic grasses increases in density over a 25‐year period, which we link to suppressed seedling recruitment. This poses a serious challenge to the long‐term sustainability of planted forests in the LRGV. We highlight potential avenues of research and modification to restoration methodologies.

Twenty years of tallgrass prairie restoration in northern Illinois, USA

AbstractEcosystem restoration projects need to measure progress toward project goals and deliver desired outcomes.This study examines longitudinal plant community data collected from permanent transects at the Nachusa Grasslands preserve in northern Illinois, USA. Managers established permanent transects for repeated plant community monitoring beginning in the mid‐1990s.Native plant communities, including rare species, have persisted, or improved with management over two decades.Planted prairies have lower proportions of native species than native prairies but have generally maintained native‐dominated communities and in some cases, increased presence of native species.Savannas have shown a distinct transition from shrub‐dense communities to herbaceous understories dominated with native species.Restoration efforts at Nachusa Grasslands have been successful at sustaining unique native plant communities through management practices like prescribed fire, brush removal and aggressive invasive species control. As a disturbance‐dependent ecosystem that has developed with human management over millennia, tallgrass prairie and savanna can thrive through restoration and active management.

Influence of Juniper on Montezuma Quail Habitat Use in Texas

ABSTRACTMontezuma quail (Cyrtonyx montezumae) inhabit oak (Quercus spp.)‐juniper (Juniperus spp.) woodlands throughout Mexico and the southwestern United States. In Texas, USA, Montezuma quail occur in the Edwards Plateau and Trans‐Pecos Mountains and Basins (Trans‐Pecos), 2 ecoregions with contrasting juniper patterns. Ashe juniper (Juniperus ashei) dominates in the Edwards Plateau and has been increasing over decades, whereas alligator juniper (Juniperus deppeana) is a co‐dominant in the Trans‐Pecos and appears to have stable Montezuma quail populations. Our objectives were to compare between ecoregions the relative abundance and habitat use of Montezuma quail in relation to juniper and quantify the influence of juniper on key features of Montezuma quail habitat (grass height, grass cover, forb cover, and forb species richness). We conducted a study from March–August 2018‒2020 in the Edwards Plateau (Kinney and Edwards counties) and Trans‐Pecos ecoregions (Jeff Davis County) to evaluate these objectives. We conducted call‐back surveys to estimate relative abundance (number of detections/hr) of Montezuma quail and identify used locations. We collected vegetation data at a micro‐scale (16‐m) at used (n = 32–30 points) and random locations (n = 70–60 points) in each ecoregion. Relative abundance of Montezuma quail was considerably lower in the Edwards Plateau (0.06 ± 0.01 detections/survey hr; ± SE) than in the Trans‐Pecos (1.10 ± 0.30 detections/survey hr). In addition, Montezuma quail selected areas of low Ashe juniper cover (<23% cover), density (<7 trees/80 m2), and height (<2 m) in the Edwards Plateau but selected areas of high alligator juniper cover (>18% cover), density (>4 trees/80 m2), and height (2–8 m) in the Trans‐Pecos. Moreover, Ashe juniper cover had a significant, negative influence on herbaceous features, whereas alligator juniper exerted little to no influence. Our results suggest that these 2 juniper species have contrasting effects on Montezuma quail space use and their habitat, possibly as a result of the contrasting influence of these junipers on herbaceous understory. Creating habitat for Montezuma quail in the Edwards Plateau generally will involve the reduction of Ashe juniper and creating patches that possess juniper trees of small stature (<2 m) with low amounts of cover (<23%) and density (<7 trees/80 m2), whereas management in the Trans‐Pecos will require site‐specific assessments based on current alligator juniper influence. © 2021 The Wildlife Society.

The role of brush encroachment in Mediterranean ecosystems: a review

Abstract Encroachment of woody plants into grasslands and subsequent brush management are among the most prominent changes occurring in arid and semiarid ecosystems over the past century. The reduced number of farms, the abandonment of marginal land and the decline of traditional farming practices have led to encroachment of the woody and shrubby components into grasslands. This phenomenon, specifically in the Mediterranean region, which is followed by a reduction in herbage production, biodiversity and increased fire risk, is generally considered an undesirable process. Sarcopoterium spinosum has had great success in the eastern Mediterranean as a colonizer and dominant bush species on a wide variety of sites and climatic conditions. In the Mediterranean dehesa, the high magnitude and intensity of shrub encroachment effects on pastures and on tree production were shown to be dependent on temporal variation. Accordingly, there are attempts to transform shrublands into grassland-woodland matrices by using different techniques. The main management interventions that are commonly used include grazing, woodcutting, shrub control with herbicides or by mechanical means, amelioration of plant mineral deficits in the soil, and fire. However, the effects of these various treatments on the shrubs under diverse environmental conditions were found to be largely context-specific. As such, the most efficient option for suppressing encroachment of shrubs is combining different interventions. Appropriate management of grazing, periodic control of the shrub component, and occasional soil nutrient amelioration can lead to the development of attractive open woodland with a productive herbaceous understory that provides a wider range of ecological services.

Plant reproductive traits in old and recently-restored temperate forest understories

Recently-restored forests on former agricultural land have impoverished herbaceous understories. This is partly due to the poor colonizing capacity of understory plants, which makes them slow in responding to land use change. Functional traits can be used to compare old and recent understories and provide insight about which plant syndromes are missing after restoration intervention. In this work, we focus on the seed and germination traits of herbaceous understories, investigating how they influence community assembly in restored woodlands.We studied temperate deciduous oak forests in two locations at the centre and southern limit of the European Atlantic region (Loder Valley Nature Reserve, England; and Tragamón Oak Grove, Spain). In each location, we sampled a pair of old and recently-restored forest sites and established 10 permanent plots, where we surveyed understory species abundances every two months for one year. We recorded plant reproductive traits for the species found and measured germination traits in laboratory experiments with seeds collected in situ. Finally, we calculated community-weighted means (CWM) for each trait and plot.The reproductive traits of old and recent forest understory species had significant differences in both locations. Old forest communities had shorter plants that flowered earlier and were more dependent on vegetative reproduction. They produced less seeds, which were heavier and had higher terminal velocity. The germination of these seeds occurred at colder temperatures and was less dependent on light. However, some dormancy-related traits seem more related to bioclimatic differences between the two locations (England and Spain).Old and recently-restored communities vary consistently for several reproductive traits, with old community traits reflecting a poor dispersal capacity and a specialized germination niche in shaded habitats under a deciduous canopy. When designing species mixes for restoration efforts, plants with particular old understory traits should be given priority.

The vascular flora of Mettler's Woods, Somerset County, New Jersey

The objective of this study was to collect and identify the plant taxa at the 26 hectare Mettler's Woods during the 2010-2012 growing seasons. We identified 105 species, in 65 genera, and in 47 families. The largest families in the flora were the Poaceae (nine species), and the Cyperaceae (eight species). Carex was the largest genus in the flora with eight species. No rare taxa were observed at the study site. Non-native Microstegium vimineum now dominates the herbaceous understory. Additionally, the death of older trees has created gaps in the forest that has favored nonnative taxa such as Celastrus orbiculatus, Lonicera japonica, and Rosa multiflora.

Long-term evaluation of restoring understories in Wyoming big sagebrush communities with mowing and seeding native bunchgrasses

Restoring degraded plant communities is a global challenge and a major priority for land managers and conservationists. Degraded Wyoming big sagebrush communities (Artemisia tridentata ssp. wyomingensis [Beetle & A. Young] S.L. Welsh) have high sagebrush cover with a depleted perennial herbaceous understory. They are widespread in western North America and are a priority for restoration because they provide habitat for sagebrush-associated species and an important forage base for livestock production. Mechanically reducing sagebrush with mowing has been attempted to restore the understory in these communities but often fails because large native perennial bunchgrasses do not increase and exotic annual grasses proliferate. Seeding large native perennial bunchgrasses after mowing sagebrush may increase their density or cover and thereby limit exotic annual grasses. Native perennial bunchgrasses are slow growing; thus, long-term studies are needed to evaluate this treatment strategy. We evaluated mowing followed by drill-seeding large native perennial bunchgrasses in southeastern Oregon for 11 yr post treatment. Large bunchgrass cover and density were approximately 2 × greater with mowing followed by seeding compared with the untreated control. However, mowing, with and without seeding, increased exotic annual grasses and decreased biological soil crusts. Sagebrush cover was less in mowed treatments compared with the untreated control, but sagebrush cover increased over time. Mowing and seeding native bunchgrasses was less successful than desired, particularly since exotic annual grasses increased substantially. This treatment may be improved by reducing the disturbance associated with mowing and drill seeding, decreasing exotic annual grass competition, and increasing the establishment of native perennial bunchgrasses. The results of our study indicate that seeding native bunchgrasses into degraded Wyoming big sagebrush communities has potential as a restoration treatment but needs refinement to improve success.

Sagebrush Bird Communities Differ with Varying Levels of Crested Wheatgrass Invasion

AbstractSagebrush communities, covering millions of hectares in the western United States, are among our most imperiled ecosystems. They are challenged by various anthropogenic stressors, including invasion by nonnative grasses that degrade habitat quality and alter ecosystem function. Sagebrush restoration efforts are underway to improve habitat conditions to benefit a wide range of sagebrush-dependent species. Because birds are good indicators of habitat quality, monitoring avian metrics is an effective way to measure progress of sagebrush restoration. We compared avian community composition and individual species abundance among three sagebrush–steppe habitat types with varying degrees of invasion by nonnative crested wheatgrass Agropyron cristatum at the Camas National Wildlife Refuge in southeastern Idaho, USA. Sagebrush-obligate birds, such as sage thrasher Oreoscoptes montanus and sagebrush sparrow Artemisiospiza nevadensis, were most abundant in sagebrush habitats with an understory of native grass. Community composition was similar between sagebrush habitats with native and nonnative grasses, but quite different from bird communities occupying crested wheatgrass. The Habitats and Populations Strategies database, a conservation planning tool, predicts that restoration of crested wheatgrass sites to sagebrush in poor or fair condition will increase the density of sagebrush-obligate bird species. Taken together, these results suggest that restoration of crested wheatgrass near-monocultures back to sagebrush will improve habitat value for much of the bird community whether or not the understory can be converted to primarily native grasses, or a mix of natives and nonnatives. Of the sagebrush bird species of concern, Brewer's sparrow Spizella breweri occupied sagebrush habitats with native vs. nonnative understory at similar abundances, and this species could serve as a metric of intermediate restoration success. However, sagebrush sparrow and sage thrasher, which were significant indicators of sagebrush with native grasses, will likely benefit most from full restoration of a native herbaceous understory. Grassland-obligate birds such as horned lark Eremophila alpestris and grasshopper sparrow Ammodramus savannarum were most abundant at crested wheatgrass–dominated sites and may not benefit from restoration back to shrubland; managers should understand potential trade-offs.

Vegetation management on private forestland can increase avian species richness and abundance

AbstractConservation efforts on private lands are important for biodiversity conservation. On private lands in South Carolina, in the southeastern United States, forestry management practices (prescribed burning, thinning, herbicide application) are used to improve upland pine habitat for wildlife and timber harvest and are incentivized through U.S. Department of Agriculture Farm Bill cost-share programs. Because many forest-dependent avian species have habitat requirements created primarily through forest management, data are needed on the effectiveness of these management activities. We studied privately owned loblolly pine (Pinus taeda) stands in the South Carolina Piedmont region. Our objective was to understand how management practices influence avian species richness and abundance at local (forest stand) and landscape levels in relatively small stands (average ~28 ha). We surveyed 49 forest stands during 2 bird breeding seasons with traditional point counts and vegetation surveys. We evaluated the effects of management on pine stand characteristics, avian species richness, and abundance of state-designated bird species of concern. Repeated burning and thinning shifted stand conditions to open pine woodlands with reduced basal area and herbaceous understories. Stands with lower basal area supported greater avian species richness. Some species increased in abundance in response to active management (e.g., Brown-headed Nuthatch [Sitta pusilla] and Indigo Bunting [Passerina cyanea]), but relationships varied. Some species responded positively to increases in forest quantity at a landscape scale (1–5 km; e.g., Northern Bobwhite [Colinus virginianus]). We found species-rich avian communities and species of conservation concern on working timber lands, indicating that incentivized forest management on private lands can provide valuable habitat for wildlife.

Middle-Late Jurassic megaflora of Laguna Flecha Negra locality in Santa Cruz Province, Patagonia, and floristic assemblages of the Bahía Laura Complex

A Middle-Late Jurassic fossil plant assemblage is described from the Bahía Laura Complex at the Laguna Flecha Negra locality, Santa Cruz Province. The fossil assemblage is autochthonous, preserved in volcaniclastic sediments in the fringes of a geothermal landscape. Taxonomic study of the palaeoflora revealed 17 taxa. The recognized species have been previously described in Jurassic localities of Gondwana and illustrate the diversity of plant communities that lived in a volcanic setting. The dominant elements of this flora are microphyllous conifers of the families Araucariaceae and Cheirolepidiaceae. Fossil leaves of Cycadeoidales co-dominate the community. There is a low diversity and abundance of ferns. Composition of the plant community is compared to coetaneous floras of the Bahía Laura Complex to analyse geographical variations in the diversity of Middle-Late Jurassic assemblages of Santa Cruz Province, and a relative uniformity is recognized. Forest landscapes were dominated by conifer trees, with cycadeoids as small trees or shrubs. The herbaceous understory was dominated by fern communities with low species diversity; Equisetales and Isoetales appeared as subordinated elements. Microphyllous conifers and cycadophytes, as well as a low diversity of ferns, are indicative of relatively dry weather.

Effects of Disturbance on Understory Vegetation across Slovenian Forest Ecosystems

The herbaceous understory represents a key component of forest biodiversity across temperate forests of Europe. Here, we quantified changes in the diversity and composition of the forest understory layer in representative Slovenian forest ecosystems between 2004/05 and 2014/15. In total, 60 plots were placed across 10 different managed forest types, ranging from lowland deciduous and mid-altitude mesic mixed forests to mountain conifer forests. This network is part of an international network of sites launched within the ICP Forests Programme aimed to assess the condition of forests in Europe. To examine how disturbance influenced understory dynamics, we estimated the disturbance impacts considering both natural and/or anthropogenic disturbances that cause significant damage to trees and to ground-surface layers, including ground-vegetation layers and upper-soil layers. Species richness across 10 sites (gamma diversity) significantly decreased from 272 to 243 species during the study period, while mean species richness per site did not significantly change. The mean value of site level Shannon diversity indices and evenness significantly increased. The cover of most common plant species increased during the monitoring period. The mean value of disturbance estimates per site increased from 0.8% in 2004/05 (ranging from 0% to 2.5%) to 16.3% in 2014/15 (ranging from 5.0% to 38.8%), which corresponded to a reduction in total vegetation cover, including tree-layer cover. More disturbed sites showed larger temporal changes in species composition compared to less disturbed sites, suggesting that forest disturbances caused understory compositional shifts during the study period. Rather than observing an increase in plant diversity due to disturbance, our results suggest a short-term decrease in species number, likely driven by replacement of more specialized species with common species.