Treesearch

Historical records show that over a century ago, fire-tolerant oaks dominated more than half of the forests across Kentucky and the southern Appalachian Mountains. Today, they account for barely a fifth. Species that historically occupied the margins, including red maple, eastern redcedar, and yellow poplar, have moved to the center. Ecologically, the shift happened relatively fast. Understanding why, and what it means for management, is aided by going back to the forest composition assessments produced by the U.S. Geological Survey and Forest Service surveyors in the early 1900s, before...

Multi-aged stands dominated by ponderosa pine (Pinus ponderosa) once occupied large areas of the American west at low to mid elevations. Much of this forest type is now even-aged after regenerating from past high-severity disturbance (i.e., wildfire or even-aged harvesting) or is transitioning toward even-aged structure in the absence of natural disturbance processes. Although even-aged forests are well-suited to a subset of management objectives and sites, multi-aged forest structures are often better aligned with the multi-objective framework under which public forestland is commonly...

As background, one approach for modeling species distributions is to model samples from distributions that are truncated to administrative or ecological boundaries, with predictor variables of climate. My objective was to examine the issue of truncation, which may not generate models that represent species ranges, even inside truncated extents, due to not incorporating the amplitude (i.e., range) of climate values where species occur. For methods, I modeled distributions of 14 wide-ranging tree species in North America and 40 combinations of the tree species truncated within 10 ecological...

Productive, large alluvial basins have been converted to agriculture, with limited retained vegetation and concomitant incomplete information about the historical vegetation before land use changes. The Yazoo Basin, a 1.7 million ha study extent as defined by 11 counties in the Mississippi Delta of the Lower Mississippi Alluvial Valley (LMAV) in the southeastern United States, currently is 70% croplands, but the historical forests of the region have not been quantified. Therefore, we recovered historical tree species composition and forest structure from land surveys conducted during years...

Range maps are time-consuming for experts to produce, but georeferenced records offer an alternative foundation for range mapping. To test data ranges from records for abundant species, I compared data ranges for 3,960 species globally to expert ranges, which are subjective approximations with errors. I produced kernels that contained 99% of georeferenced records, contributing high-certainty range areas limited to sampling extents. To extend kernels, I merged kernels with aggregated polygons of records, which provided undersampled areas. Selecting one of six different aggregation distances...

Range maps for most terrestrial invertebrates generally are not accessible as spatial data. My objective was to build global range maps for 11,844 terrestrial insect species, specifically pollinator species with at least 400 georeferenced records each, by applying species range kernels, which contained about 99% of the records, and polygons of aggregated georeferenced records. Depending on aggregation distance, point aggregation generates a range of polygons, in terms of shape and area. To illustrate, for 225 odonate species that had range maps developed by experts, I selected one of six...

Spatial thinning of samples to remove clustered georeferenced records at local scales has become standard practice for species distribution models. Alternatively, I demonstrated the sampling issue of unequal sampling at global scales, and provided and tested a solution by equalizing samples. First, I used 17,200 species to characterize intensity gradients, with kernel density grids of georeferenced records, for 12 taxa. Secondly, I developed a method to even sampling intensity, by dividing kernel density grids into 10 quantiles of sampling intensity classes by taxa, and for each species, I...

Understanding the relationship between climate and fitness will be important when predicting how plant populations respond to climate change. We conducted a replicated common garden experiment (4 sites × 2 yr) with 96 genotypes ( n = 22 492 individuals) of the invasive annual grass Bromus tectorum (cheatgrass) to understand how eco‐evolutionary context mediates this important relationship.We grew genotypes in varying soil microclimate conditions by manipulating surface albedo, and at two planting densities. We calculated a ‘climate mismatch’ for each genotype within each microclimate to...

Interferometric Synthetic Aperture Radar (InSAR) offers a potential pathway for measuring seasonal snow water equivalent (SWE) and snow depth at spatial and temporal scales needed for basin‐scale hydrology. First proposed for seasonal snow more than 25 years ago, InSAR uses repeat‐pass radar phase differences to estimate changes in SWE or depth caused by microwave propagation through snow. This review synthesizes InSAR‐based snow monitoring from early theoretical and satellite demonstrations through recent tower, airborne, and spaceborne studies. We summarize the retrieval physics,...

Wildfires drive ecosystem nitrogen (N) loss globally through combustion of plant biomass and by depositing Nrich ash onto soils to stimulate emissions of nitric oxide (NO) and nitrous oxide (N2O)—trace gases that affect air quality and climate. However, spatial and temporal variation in post-fire soil NO and N2O emissions remain under-explored, motivating our hypothesis that emissions would vary temporally with plant and microbial successional changes and spatially with burn severity, available N, soil physicochemical properties, and microbial activity. We sampled burned and unburned soils...