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Plant ecology

Science Spotlights

A picture of a small cage with abundant blanket flowers.
A recent meta-analysis collating global results from seed predation studies found that small mammals may structure plant communities around the world, with an interesting twist – in deserts where seeds are relatively small, they suppress large-seeded plants, but in systems like tropical forests, where seed sizes are much larger, they tend to suppress relatively small seeded plant species.
Risk factors for tree mortality in boxes, with color of boxes indicating species. Grouped by site and stand, radial growth, carbon isotopes, tree size, resin ducts, BAI-Δ13C relationships, and climate relationships.
Determining why some trees die while others survive both drought and insect outbreaks is valuable for forecasting tree mortality events, which are expected to become more frequent with further climate change. We collected stand and tree-level data on the Sierra and Los Padres National Forests in Central and Southern California, where tree mortality from the combination of drought and bark beetles was widespread. 
A measuring tool encircles a young ponderosa pine
Ponderosa pine seedling establishment can be constrained following especially large, high-severity wildfires. Young seedlings face high mortality levels in the first few years and remain vulnerable to the next fire until they are taller. Understanding attributes associated with the growth of naturally regenerating seedlings that survive 10+ years postfire is useful in developing post-fire management strategies.
A picture of a pine tree core with visible tree rings, and resin ducts visible as small dots within the rings.
Resin ducts are formed in the wood of pine trees and are a measure of the level of tree defense from insects and pathogens. We developed methods and software code to allow researchers to more easily quantify resin ducts.
A ponderosa pine forest with mature trees in the background and seedlings in the foreground.
Lick Creek is the longest running fuel treatment and restoration study of ponderosa pine forests in the northern U.S. Rocky Mountains. Through repeat photography and numerous published studies, we show how fuels and vegetation have changed over the 25 years since treatment and compare the effects of mechanical harvesting with and without prescribed burning.
A single standing tree surrounded by mostly fallen, dead trees and grass, and a few seedlings.
Fire refugia are places within high-severity burns that remain unburned or burn with low severity. They can be important for maintaining and regenerating fire-prone forested systems. We used satellite-derived imagery of fires to investigate where and when fire refugia are most likely to form and persist on a landscape. We then collected field data to better understand how fire refugia promote forest recovery and ecosystem resilience. 
A closeup of a seedling with roots on a white background.
Finding the best populations to use in restoration is a key part of project success. We present a case study of a partnership between scientists and restoration practitioners designed to select and screen local seed sources for large-scale restoration. 
Beetles crawling out of a white bucket into a tree.
Saltcedar (Tamarix spp.), an aggressively invasive Eurasian tree, is a dominant and widespread woody riparian species in the southwestern U.S. Biocontrol of saltcedar with the leaf beetle Diorhabda carinulata can be made more effective with semiochemicals (smells). 
A screenshot of the PhenoMap application.
PhenoMap monitors weekly changes in phenology (green-up and brown-down) across the western United States via satellite.  Weekly satellite values of “greenness” successfully tracked changes in phenology documented by phenology cameras in grasslands, shrublands, deciduous broadleaf, and mixed forests but demonstrated the difficulty of tracking changes in phenology of evergreen needleleaf forests.
Myrtle rust
At least three different biotypes (genetic groups) of the invasive myrtle rust pathogen (Austropuccinia psidii) were identified, each with different host associations, geographic distributions, and potential distribution (suitable climate space). Each biotype poses its own distinct invasive threats to diverse hosts in the Myrtaceae (e.g., eucalypts, guava, ‘ōhi’a) grown in different geographic areas.