Microclimatic Conditions Mediate The Effect of Deadwood and Forest Characteristics On a Threatened Beetle Species, Tragosoma Depsarium

While climate change has increased interest in the influence of microclimate on many organisms, species inhabiting deadwood have rarely been studied. Here we explore the relationships between characteristics of forest stands, deadwood and microclimate, and analyse how the microclimate inside deadwood affects the occurrence of wood-living organisms, exemplified by the red-listed beetle Tragosoma depsarium. Some of the measured deadwood and forest variables explain much of the variation in temperature, but little of humidity aspects of the microclimate within deadwood. Several variables known to influence habitat quality for deadwood-dependent species were found to correlate with microclimate viz.: warmer conditions in standing deadwood and open canopy than in downed logs and under a closed canopy; higher humidity and more stable daily temperatures in shaded habitats and in downed and large-diameter wood, than in sun-exposed locations and standing, small-diameter wood.T. depsarium occupancy and abundance were negatively correlated with daily temperature fluctuations, and positively related to spring and summer temperature and humidity. This can explain why the species occurred more frequently in deadwood items with characteristics associated with these microclimatic conditions, i.e. downed large-diameter logs occurring in open conditions. Since microclimatic conditions are important for T. depsarium and related to several habitat characteristics, we expect the effects of these characteristics to interact with each other, and for species’ habitat requirements to vary due to local and regional climate conditions, and to changes due to climate warming.

Radial variations in wood density, and their implications for above-ground biomass estimations, in a tropical high-andean forest

Wood density (WD) is a central trait to explain tree functioning, and is also an important predic­tor of tree above-ground biomass (AGB). Therefore, radial trends in WD (i.e., from pith to bark) may have important implications in understanding tree life-history variations, as well as in forest biomass and carbon estimations. The occurrence of these radial trends in WD is thought to vary among forests, particularly with canopy openness and stratification. Yet, most of the studies on this topic in tropical forests have been conducted on lowland closed-canopy forests, while very little is known about the prevalence and magnitude of these trends among trees from open-canopy forests, such as high-mountain forests. I examined radial gradients in WD and explored their implications for AGB estimations. Radial wood cores were taken with increment borers from 69 trees belonging to 18 species from a high-An­dean forest. Each wood core was cut every 1-cm, and WD was measured for every 1-cm segment. Errors in AGB estimations that resulted from not considering radial trends in WD were estimated for each tree and species. Eight out of eighteen species had significant radial trends in WD. Among these species, two species showed decreases of WD towards the bark, one species showed increments of WD from pith to bark, and five species showed U-shaped gradients (i.e., high WD near the pith and bark, and relatively low WD at inter­mediate diameters). The prevalence of U-shaped radial trends in WD may be related to the relatively open and less stratified canopy of the study forest. Not taking into account radial trends in WD led in general to under-estimations of AGB (averaging −7.66 % when using mean WD, and −5.56 % for outer WD) in most of the study species, suggesting that tropical high-Andean forests may possibly store more biomass carbon than has been previously estimated. These findings are important to expand our knowledge on wood allocation patterns during tree ontogeny, and also to improve the accuracy of biomass and carbon estimations in tropical high-Andean forests.

Burrow Densities of Primary Burrowing Crayfishes in Relation to Prescribed Fire and Mechanical Vegetation Treatments

Fire suppression and other factors have drastically reduced wet prairie and pine savanna ecosystems on the Coastal Plain of the southeastern United States. Restoration of these open-canopy environments often targets one or several charismatic species, and semi-aquatic species such as burrowing crayfishes are often overlooked in these essentially terrestrial environments. We examined the relationship between primary burrowing crayfishes and three vegetation treatments implemented over at least the past two decades in the Mississippi Sandhill Crane National Wildlife Refuge. Vegetation in the 12 study sites had been frequently burned, frequently mechanically treated, or infrequently managed. Creaserinus spp., primarily C. oryktes, dominated the crayfish assemblage in every site. We counted crayfish burrow openings and coarsely categorized vegetation characteristics in 90, 0.56-m2 quadrats evenly distributed among six transects per site. The number of active burrow openings was negatively, exponentially related to both the percent cover of woody vegetation and the maximum height of woody vegetation in quadrats, and to the number of trees taller than 1.2 m per transect, indicating that woody plant encroachment was detrimental to the crayfishes. Results were consistent with several other studies from the eastern US, indicating that some primary burrowing crayfishes are habitat specialists adapted to open-canopy ecosystems.

Effect of Vegetation on the Abundance of Tick Vectors in the Northeastern United States: A Review of the Literature

Tick-borne illnesses have been on the rise in the United States, with reported cases up sharply in the past two decades. In this literature review, we synthesize the available research on the relationship between vegetation and tick abundance for four tick species in the northeastern United States that are of potential medical importance to humans. The blacklegged tick (Ixodes scapularis) (Say; Acari: Ixodidae) is found to be positively associated with closed canopy forests and dense vegetation thickets, and negatively associated with open canopy environments, such as grasslands or old agricultural fields. The American dog tick (Dermacentor variabilis) (Say; Acari: Ixodidae) has little habitat overlap with I. scapularis, with abundance highest in grasses and open-canopy fields. The lone star tick (Amblyomma americanum) (Linnaeus; Acari: Ixodidae) is a habitat generalist without consistent associations with particular types of vegetation. The habitat associations of the recently introduced Asian longhorned tick (Haemaphysalis longicornis) (Neumann; Acari: Ixodidae) in the northeastern United States, and in other regions where it has invaded, are still unknown, although based on studies in its native range, it is likely to be found in grasslands and open-canopy habitats.

Are Juglans neotropica Plantations Useful as a Refuge of Bryophytes Diversity in Tropical Areas?

Neotropical montane forests are considered biodiversity hotspots, where epiphytic bryophytes are an important component of the diversity, biomass and functioning of these ecosystems. We evaluated the richness and composition of bryophytes in secondary successional forests and mixed plantations of Juglans neotropica. In each forest type, the presence and cover of epiphytic bryophytes was registered in 400 quadrats of 20 cm × 30 cm. We analyzed the effects of canopy openness, diameter at breast height (DBH) and forest type on bryophyte richness, using a generalized linear model (GLM), as well as the changes in species composition using multivariate analysis. Fifty-five bryophyte species were recorded, of which 42 species were in secondary forests and 40 were in mixed plantations. Bryophyte richness did not change at forest level; however, at tree level, richness was higher in the mixed plantation of J. neotropica compared to the secondary forests, due to the presence of species adapted to high light conditions. On the other hand, bryophyte communities were negatively affected by the more open canopy in the mixed plantation of J. neotropica, species adapted to more humid conditions being less abundant. We conclude that species with narrow microclimatic niches are threatened by deforestation, and J. neotropica plantations do not act as refuge for drought-sensitive forest species present in secondary forests.

Extinction at the end-Cretaceous and the origin of modern Neotropical rainforests

The end-Cretaceous event was catastrophic for terrestrial communities worldwide, yet its long-lasting effect on tropical forests remains largely unknown. We quantified plant extinction and ecological change in tropical forests resulting from the end-Cretaceous event using fossil pollen (>50,000 occurrences) and leaves (>6000 specimens) from localities in Colombia. Late Cretaceous (Maastrichtian) rainforests were characterized by an open canopy and diverse plant–insect interactions. Plant diversity declined by 45% at the Cretaceous–Paleogene boundary and did not recover for ~6 million years. Paleocene forests resembled modern Neotropical rainforests, with a closed canopy and multistratal structure dominated by angiosperms. The end-Cretaceous event triggered a long interval of low plant diversity in the Neotropics and the evolutionary assembly of today’s most diverse terrestrial ecosystem.

Accuracy and Precision of Commercial Thinning to Achieve Wildlife Management Objectives in Production Forests

Tree stocking and the associated canopy closure in production forests is often greater than optimal for wildlife that require an open canopy and the associated understory plant community. Although mid-rotation treatments such as thinning can reduce canopy closure and return sunlight to the forest floor, stimulating understory vegetation, wildlife-focused thinning prescriptions often involve thinning stands to lower tree densities than are typically prescribed for commercial logging operations. Therefore, we quantified the accuracy and precision with which commercial logging crews thinned pre-marked and unmarked mid-rotation loblolly pine (Pinus taeda) stands to residual basal areas of 9 (low), 14 (medium), and 18 (high) m2/ha. Following harvest, observed basal areas were 3.36, 1.58, and 0.6 m2/ha below target basal areas for the high, medium, and low basal area treatments, respectively. Pre-marking stands increased precision, but not accuracy, of thinning operations. We believe the thinning outcomes we observed are sufficient to achieve wildlife objectives in production forests, and that the added expense associated with pre-marking stands to achieve wildlife objectives in production forests depends on focal wildlife species and management objectives.