Treesearch

Insect outbreaks are often assumed to increase the severity or probability of fire occurrence through increased fuel availability, while fires may in turn alter susceptibility of forests to subsequent insect outbreaks through changes in the spatial distribution of suitable host trees. However, little is actually known about the potential synergisms between these natural disturbances. Assessing interdisturbance synergism is challenging due to the short length of historical records and the confounding influences of land use and climate changes on natural disturbance dynamics. We used...

Twentieth-century land management has altered the structure and composition of mixed-conifer forests and decreased their resilience to fire, drought, and insects in many parts of the Interior West. These forests occur across a wide range of environmental settings and historical disturbance regimes, so their response to land management is likely to vary across landscapes and among ecoregions. However, this variation has not been well characterized and hampers the development of appropriate management and restoration plans. We identified mixed-conifer types in central Oregon based on...

Fire is an important global ecological process that influences the distribution of biomes, with consequences for carbon, water, and energy budgets. Therefore it is impossible to appropriately model the history and future of the terrestrial ecosystems and the climate system without including fire. This study incorporates the process-based prognostic fire module SPITFIRE into the global vegetation model ORCHIDEE, which was then used to simulate burned area over the 20th century. Special attention was paid to the evaluation of other fire regime indicators such as seasonality, fire size and...

Flowers with poricidally dehiscent anthers are typically nectarless but are avidly visited and often solely pollinated by bees that sonicate the flowers to harvest pollen. Sonication results from shivering the thoracic flight muscles. Honey bees (Apis) and the 4,000+ species of Megachilidae are enigmatic in their seeming inability to sonicate flowers. The oligolectic megachilid bee Osmia brevis was found audibly sonicating two of its beardtongue pollen hosts, Penstemon radicosus and P. cyananthus. The bees’ high-pitched sonication sequences are readily distinguishable from flight sounds in...

Differential resistance to stripe rust (Puccinia striiformis) in a planting of 111 wild collections of Basin wild rye (Leymus cinereus) was noted 2011-2013. In 2011, rust severity was rated on a scale of 1-9. Much lighter infection in 2012 and 2013 was rated as the number of symptomatic leaves per plant divided by plant circumference (to adjust for plant size). Effect of collection was significant in 2011 (P = 0.0042), 2012 (P = 0.0032), and 2013 (P = 0.0095), with a relatively weak (0.23) but significant (P = 0.0149) correlation between 2011 and 2012 and a stronger (0.38) and highly...

Rangeland management is largely focused on managing vegetation change. Objectives may include managing against change if the desired vegetation is in place, or attempting to create a shift in vegetation if the desired plant community is not present. There is a rich body of research documenting influences of disturbance and management on rangeland vegetation. However, in many cases the information is largely observational and does not identify mechanisms driving change. We propose using the regeneration niche concept to more effectively predict when vegetation change is possible and to...

Sunflower family (Asteraceae). Hoary tansyaster is a short-lived perennial forb with pale to dark purple flowers. Plants are 15 to 75 cm (6 to 30 in) tall with diffuse branching. Leaves are about 5 cm (2 in) long and 6 mm (0.25 in) wide, oblong or lance shaped with entire to sharply toothed margin. Flower heads have many subtending bracts that reflex away from the flower at the tip (Welsh et al., 2003). Flower heads and vegetation are very sticky and heavily scented. Bracts are white and membranous at the bottom and green at the tip. The pappus of the achene is dirty white and hair-like....

Hoary tansyaster is a short-lived perennial forb with pale to dark purple flowers. Plants are 6 to 30 inches tall with diffuse branching. Leaves are about 2 inches long and oblong or lance shaped with entire to sharply toothed margin. The flower heads have many subtending bracts that reflex away from the flower at the tip. These bracts are white and membranous at the bottom and green at the tip. Leaves and flower heads are very sticky and heavily scented. The pappus of the achene is dirty white and hair-like. There are approximately 1.3 million seeds/lb based on seed counts conducted by...

The red tubular flowers of Penstemon eatonii (Plantaginaceae) typify the classic pollination syndrome for hummingbirds. Bees are thought to diminish its seed siring potential, but we found that foraging female generalist bees (Apis, Anthophora) deposited substantial amounts of conspecific pollen on P. eatonii stigmas. In the absence of hummingbirds, bee pollination of cultivated P. eatonii annually generated massive seed yields from a 1.5 ha field. Most penstemons with red tubular flowers like P. eatonii present a symmetrically flared floral opening that facilitates landing by foraging...

Bark beetle-caused tree mortality affects important forest ecosystem processes. Remote sensing methodologies that quantify live and dead basal area (BA) in bark beetle-affected forests can provide valuable information to forest managers and researchers. We compared the utility of light detection and ranging (lidar) and the Landsat-based detection of trends in disturbance and recovery (LandTrendr) algorithm to predict total, live, dead, and percent dead BA in five bark beetle-affected forests in Alaska, Arizona, Colorado, Idaho, and Oregon, USA. The BA response variables were predicted from...