Treesearch

• The extent to which water availability can be used to predict the enlargement and final dimensions of xylem conduits remains an open issue. • We reconstructed the time course of tracheid enlargement in Pinus sylvestris trees in central Spain by repeated measurements of tracheid diameter on microcores sampled weekly during a 2 yr period. We analyzed the role of water availability in these dynamics empirically through time-series correlation analysis and mechanistically by building a model that simulates daily tracheid enlargement rate and duration based on Lockhart’s equation and water...

Conflicting evidence exists supporting linear and nonlinear density‐dependent population growth when species have slow life histories. The Ricker (linear) and θ‐logistic (nonlinear) models are commonly used to analyze survey data for these species, but no evaluation has examined whether these hypotheses can be differentiated with field data. We conducted a simulation exploring effects from shape of density dependence and variation in vital rates on the fit of these models. When vital rates had moderate to high variation, the models had similar fit. The θ‐logistic model differed from the...

Population and land management relies on understanding population regulation and growth, which may be impacted by variation in population growth parameters within and among populations. We explored the interactions between variation in carrying capacity (K), intrinsic population growth rate (r), and strength of density dependence (β) within and among elk (Cervus elaphus) herds in a small part of the geographic range of the species. We also estimated stochastic fluctuations in abundance around K for each herd. We fit linear Ricker growth models using Bayesian statistics to seven time series...

The non-indigenous colonial tunicate Didemnum vexillumplagues many shellfish aquaculture operations around the world by smothering crop and gear and displacing juvenile bivalves. There are two populations of D. vexillumin Oregon, but little is known regarding their spatial extent, seasonal dynamics, annual variability, reproductive biology, or ecology. SCUBA divers monitored the seasonal variation and spatial extent of the nascent D. vexillumpopulation in its current foothold at Umpqua Aquaculture, a longline oyster farm adjacent to Winchester Bay, Oregon. From May 2011 to November 2016,...

The early detection of plant pathogens at the landscape scale holds great promise for better managing forest ecosystem threats. In Hawai‘i, two recently described fungal species are responsible for increasingly widespread mortality in ‘ōhi‘a Metrosideros polymorpha, a foundational tree species in Hawaiian native forests. In this study, we share work from repeat laboratory and field measurements to determine if visible near-infrared and optical remote sensing can detect pre-symptomatic trees infected with these pathogens. After generating a dense time series of laboratory spectral reflectanc...

Climate change is expected to have heterogeneous effects on agriculture across the USA, where temperature and precipitation regimes are already changing. While the overall effect of climate change on agriculture is uncertain, farmers’ perceptions of current and future climate and weather conditions will be a key factor in how they adapt. This paper analyzes data from paired surveys (N = 817) and natural variation from baseline weather across the inland Pacific Northwest (iPNW), to determine if long-term, gradual changes in precipitation, and temperature distributions affect farmers’...

Farmers, particularly small farmers, are on the frontlines of climate change. In Oregon’s Southern Willamette Valley, a needs assessment was conducted of small farmers in 2017, where questions related to climate change risks, attitudes toward adaptation and climate beliefs were assessed. Out of all the respondents (n = 123), the majority (70%) believe that climate change is occurring, and is caused mostly by human activities. The majority (58%) also strongly agree with the statement that they will have to change practices to cope with increasing climate variability in order to ensure the...

There has been an increasing interest in the economic health cost from smoke exposure from wildfires in the past 20 years, particularly in the north-western USA that is reflected in an emergent literature. In this review, we provide an overview and discussion of studies since 2006 on the health impacts of wildfire smoke and of approaches for the estimation of the associated economic cost. We focus on the choice of key variables such as cost estimators for determining the economic impact of mortality and morbidity effects. In addition, we provide an in-depth discussion and guidance on the...

In this study, for five sites around the world, we look at the effects of different model types and variable selection approaches on forest yield modelling performances in an area-based approach (ABA). We compared ordinary least squares regression (OLS), k-nearest neighbours (kNN) and random forest (RF). Our objective was to test if there are systematic differences in accuracy between OLS, kNN and RF in ABA predictions of growing stock volume. The analyses are based on a 5-fold cross-validation at five study sites: an eucalyptus plantation, a temperate forest and three different boreal...

The flame length of a plume in incompressible cross-flow is analyzed and the results are compared with those obtained in a chemically reacting water tunnel experiment. It is argued that the axial vortex pair in the flow arises from the plume momentum normal to the free stream, the momentum flux being equivalent to the impulse from the buoyant force.