Treesearch

The representation of vegetative sub‐canopy wind is critical in numerical weather prediction (NWP) models for the determination of the air‐surface exchange processes of heat, momentum, and trace gases. Because of the relationship between wind speed and fire behaviors, the influence of the canopy on near‐surface wind speed is critical for prognostic fire spread models used in regional NWP models. In practice, the wind speed at the midflame point of fires (midflame wind speed) is used to determine the rate of fire spread. However, the wind speeds from most in situ measurements and NWP models...

Outbreaks of insects and diseases are part of the natural disturbance regime of all forests. However, introduced pathogens have had outsized impacts on many dominant forest tree species over the past century. Mitigating these impacts and restoring these species are dilemmas of the modern era. Here, we review the ecological and economic impact of introduced pathogens, focusing on examples in North America. We then synthesize the successes and challenges of past biotechnological approaches and discuss the integration of genomics and biotechnology to help mitigate the effects of past and...

This paper demonstrates how the slope of a production possibilities frontier (PPF) can be used to empirically identify the presence of an ecosystem externality. Complementarity between non-market ecosystem services implies the PPF between these services may be upward sloping. In contrast, private landowners that ignore these complementarities will treat non-market ecosystem services as competing products thereby ensuring a downward sloping PPF. Using data from 738 U.S. watersheds, we compare the slope of PPFs on predominately private and predominately public watersheds. We find evidence...

Soil respiration (Rs), the soil‐to‐atmosphere flux of CO2, is a dominant but uncertain part of the carbon cycle, even after decades of study. This review focuses on progress in understanding Rs from laboratory incubations to global estimates. We survey key developments of in situ ecosystem‐scale Rs observations and manipulations, synthesize Rs meta‐analyses and global flux estimates, and discuss the most compelling challenges and opportunities for the future. Increasingly sophisticated lab experiments have yielded insights into the interaction among heterotrophic respiration, substrate...

We examined the seasonality of photosynthesis in 46 evergreen needleleaf (evergreen needleleaf forests (ENF)) and deciduous broadleaf (deciduous broadleaf forests (DBF)) forests across North America and Eurasia. We quantified the onset and end (StartGPP and EndGPP) of photosynthesis in spring and autumn based on the response of net ecosystem exchange of CO2 to sunlight. To test the hypothesis that snowmelt is required for photosynthesis to begin, these were compared with end of snowmelt derived from soil temperature. ENF forests achieved 10% of summer photosynthetic capacity ∼3 weeks...

Balsam woolly adelgid (Adelges piceae; BWA) is an invasive forest pest in the US whose infestation in fir forests can cause widespread tree mortality. A growing body of evidence suggests that the severity of BWA’s effects is linked to climatic conditions, where sites featuring seasonally warmer temperatures tend to demonstrate higher degrees of insect-induced forest degradation. Thus, a warming climate may promote the expansion of BWAdriven damage, particularly in highly susceptible subalpine fir (Abies lasiocarpa) forests. The degree to which climate change may foster BWA infestation and...

Large and downed woody fuels remaining behind a wildfire’s flame front tend to burn in a smoldering regime, producing large quantities of toxic gases and particulate emissions, which deteriorates air quality and compromises human health. Smoldering burning rates are affected by fuel type and size, the amount of oxygen reaching the surface, and heat losses to the surroundings. An external wind has the dual effects of bringing fresh oxidizer to the fuel surface and porous interior, while at the same time enhancing convective cooling. In this work, a series of experiments were conducted on...

Background. As fire seasons in the Western US intensify and lengthen, fire managers have been grappling with increases in simultaneous, significant incidents that compete for response resources and strain capacity of the current system. Aims. To address this challenge, we explore a key research question: what precursors are associated with ignitions that evolve into incidents requiring high levels of response personnel? Methods. We develop statistical models linking human, fire weather and fuels related factors with cumulative and peak personnel deployed. Key results. Our analysis generates...

Changing fire regimes in western North America have raised the possibility of widespread loss of forest cover, making forest restoration a major priority. In one such ecosystem, the Sierra Nevada in California, the implications of forest management policy have been evaluated primarily via their potential effects on the California Spotted Owl (Strix occidentalis occidentalis). Yet the owl’s cryptic life history, large home range, and declining population all make it difficult to study. The Hermit Warbler (Setophaga occidentalis) may be a valuable proxy species for the Spotted Owl because...

Temporal variability in population growth rates is a fundamental property of natural populations with implications for almost any facet in ecology and evolution. Using the framework of nonlinear averaging, we test the hypothesis that the magnitude of short-term variability in population growth rates is influenced by the long-term means of climatic conditions.