Valentine Herrmann

Smithsonian Institution · Smithsonian Conservation Biology Institute

Free‐roaming cats are a conservation concern in many areas but identifying their impacts and developing mitigation strategies requires a robust understanding of their distribution and density patterns. Urban and residential areas may be especially relevant in this process because free‐roaming cats are abundant in these anthropogenic landscapes. Her...

Accurate field data are essential to understanding ecological systems and forecasting their responses to global change. Yet, data collection errors are common, and data analysis often lags far enough behind its collection that many errors can no longer be corrected, nor can anomalous observations be revisited. Needed is a system in which data quali...

As the climate changes, warmer spring temperatures are causing earlier leaf-out1–3 and commencement of CO2 uptake1,3 in temperate deciduous forests, resulting in a tendency towards increased growing season length3 and annual CO2 uptake1,3–7. However, less is known about how spring temperatures affect tree stem growth8,9, which sequesters carbon in...

As the climate changes, warmer spring temperatures are causing earlier leaf-out1–6 and commencement of net carbon dioxide (CO2) sequestration2,4 in temperate deciduous forests, resulting in a tendency towards increased growing season length1,4,5,7–9 and annual CO2 uptake2,4,10–14. However, less is known about how spring temperatures affect tree ste...

Allometric equations for calculation of tree aboveground biomass (AGB) form the basis for estimates of forest carbon storage and exchange with the atmosphere. While standard models exist to calculate forest biomass across the tropics, we lack a standardized tool for computing AGB across boreal and temperate regions that comprise the global extratro...

Tree rings provide an invaluable long‐term record for understanding how climate and other drivers shape tree growth and forest productivity. However, conventional tree‐ring analysis methods were not designed to simultaneously test effects of climate, tree size, and other drivers on individual growth. This has limited the potential to test ecologica...

Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological, energy, and carbon budgets at the land–atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observatio...

Camera trap surveys use infrared-flash camera traps more frequently than white-flash camera traps due to claims that white-flash cameras impact animal behaviour and reduce capture rates. While several studies have examined the impact of white-flash on individual behaviour, few have assessed the effect of flash type on probability of detection. We u...

Forests are major components of the global carbon (C) cycle and thereby strongly influence atmospheric carbon dioxide (CO2) and climate. However, efforts to incorporate forests into climate models and CO2 accounting frameworks have been constrained by a lack of accessible, global-scale synthesis on how C cycling varies across forest types and stand...

Carbon (C) fixation, allocation, and metabolism by trees set the basis for energy and material flows in forest ecosystems and define their interactions with Earth’s changing climate. However, while many studies have considered variation in productivity with latitude and climate, we lack a cohesive synthesis on how forest carbon fluxes vary globally...

The effects of climate change on tropical forests will depend on how diverse tropical tree species respond to drought. Current distributions of evergreen and deciduous tree species across local and regional moisture gradients reflect their ability to tolerate drought stress, and might be explained by functional traits. ●We measured leaf water poten...

Exotic forest insects and pathogens (EFIP) have become regular features of temperate forest ecosystems, yet we lack a long-term perspective on their net impacts on tree mortality, carbon sequestration, and tree species diversity. Here, we analyze 3 decades (1987–2019) of forest monitoring data from the Blue Ridge Mountains ecoregion in eastern Nort...

As human activities expand globally, there is a growing need to identify and mitigate barriers to animal movements. Fencing is a pervasive human modification of the landscape that can impede the movements of wide‐ranging animals. Previous research has largely focused on whether fences block movements altogether, but a more nuanced understanding of...

As climate change drives increased drought in many forested regions, mechanistic understanding of the factors conferring drought tolerance in trees is increasingly important. The dendrochronological record provides a window through which we can understand how tree size and traits shape growth responses to droughts. We analyzed tree‐ring records for...

Plant transpiration links physiological responses of vegetation to water supply and demand with hydrological,energy and carbon budgets at the land-atmosphere interface. However, despite being the main land evaporative flux at the global scale, transpiration and its response to environmental drivers are currently not well constrained by observations...

To constrain global warming, we must strongly curtail greenhouse gas emissions and capture excess atmospheric carbon dioxide1,2. Regrowing natural forests is a prominent strategy for capturing additional carbon³, but accurate assessments of its potential are limited by uncertainty and variability in carbon accumulation rates2,3. To assess why and w...

Field-measured soil respiration (RS, the soil-to-atmosphere CO2 flux) observations were compiled into a global soil respiration database (SRDB) a decade ago, a resource that has been widely used by the biogeochemistry community to advance our understanding of RS dynamics. Novel carbon cycle sciences questions require updated and augmented global in...

The diverse large mammal communities found in Asian dry forests and savannas should segregate based on their diet selection. We examined the diet composition of sympatric ungulate species using metabarcoding to determine whether their diet was segregated and whether obvious attributes (i.e., body size, phylogeny, ecology) explained the structure. W...

Birds that depend on grassland and successional‐scrub vegetation communities are experiencing a greater decline than any other avian assemblage in North America. Habitat loss and degradation on breeding and wintering grounds are among the leading causes of these declines. We used public and private lands in northern Virginia, USA, to explore benefi...

1.The climate sensitivity of forest ecosystem woody productivity (ANPPstem ) influences carbon cycle responses to climate change. For the first time, we combine long-term annual growth and forest census data of a diverse temperate broadleaf deciduous forest, seeking to resolve whether ANPPstem is primarily moisture- or energy-limited and whether cl...

Forests play an influential role in the global carbon (C) cycle, storing roughly half of terrestrial C and annually exchanging with the atmosphere more than ten times the carbon dioxide (CO2) emitted by anthropogenic activities. Yet, scaling up from field‐based measurements of forest C stocks and fluxes to understand global scale C cycling and its...

Mammalian herbivory and exotic plant species interactions are an important ongoing research topic, due to their presumed impacts on native biodiversity. The extent to which these interactions affect forest understory plant community composition and persistence was the subject of our study. We conducted a 5-year, 2 × 2 factorial experiment in three...

Drought disproportionately affects larger trees in tropical forests, but implications for forest composition and carbon (C) cycling in relation to dry season intensity remain poorly understood. In order to characterize how C cycling is shaped by tree size and drought adaptations and how these patterns relate to spatial and temporal variation in wat...

Nutria (Myocaster coypus), invasive, semi-aquatic rodents native to South America, were introduced into Maryland near Blackwater National Wildlife Refuge (BNWR) in 1943. Irruptive population growth, expansion, and destructive feeding habits resulted in the destruction of thousands of acres of emergent marshes at and surrounding BNWR. In 2002, a par...

Stem diameter is one of the most commonly measured attributes of trees, forming the foundation of forest censuses and monitoring. Changes in tree stem circumference include both irreversible woody stem growth and reversible circumference changes related to water status, yet these fine-scale dynamics are rarely leveraged to understand forest ecophys...

List of all trees equipped with ADBs. (DOCX)

Relationship between Tband and Tair. (DOCX)

Thermal expansion experiment. (DOCX)

TreeHugger failures. (DOCX)

Many morphological, physiological, and ecological traits of trees scale with diameter, shaping the structure and function of forest ecosystems. Understanding the mechanistic basis for such scaling relationships is key to understanding forests globally and their role in Earth's changing climate system.Here, we evaluate theoretical predictions for th...

The Aquatic Warbler Acrocephalus paludicola is the only endangered songbird in continental Europe. This trans-Saharan migratory bird significantly transits along the French Atlantic coastline during post-breeding migration and the right bank of the Gironde estuary has been identified as an important stopover site. We studied the spatial occupancy s...

The Aquatic Warbler Acrocephalus paludicola is one of the most threatened passerines in the world and the only under risk of extinction in mainland Europe. The goal of this work is to determine the relevance of wetlands of the Bay of Biscay for the Aquatic Warbler, during the autumn migration period. To test this we used ringing data on migrants ca...

Musseau R., Herrmann V., Herault T. (2014)-Stratégies d'occupation spatiale du Phragmite Aquatique Acrocephalus paludicola sur une importante escale migratoire et orientations de gestion des espaces sur un site clef pour l'espèce. Alauda, 82: 313-326.

The Aquatic Warbler is the most threatened passerine in continental Europe (according IUCN scale). The species is a long-distance migrant which migrates along the French Atlantic coast in August during postnuptial passage. One of the major staging area is the right bank of the Gironde estuary in southwestern France. We started a research project in...

The Afro-Palearctic migrant Aquatic Warbler Acrocephalus paludicola has been known as an abundant breeding bird in eastern Europe until the 20th century, after which it began to decrease in a number of countries due to several threats (essentially anthropogenic) changing the ecological functioning of its key sites (de By 1990, Flade & Lachmann 2008...

Along the French Atlantic coastline, the right bank of Gironde estuary has been identified as an important migration stopover site for the Aquatic Warbler. We analyzed radio-tracking, capture-mark-recapture and dropping contents data to identify habitats used by birds, to assess their stopover duration, their fuel deposition rate and to characteriz...

During August 2011, BioSphère Environnement has been conducting ringing operations at Gironde estuary, Charente-Maritime, France. Subject of this project under the scientific coordination of the Muséum National d’Histoire Naturelle is the stop-over ecology of Aquatic Warbler Acrocephalus paludicola. In early August, 216 m of mistnets were installed...