Treesearch

Plant growth can be limited by resource acquisition and defence against consumers, leading to contrasting trade-off possibilities. The competition-defence hypothesis posits a trade-off between competitive ability and defence against enemies (e.g. herbivores and pathogens). The growth-defence hypothesis suggests that strong competitors for nutrients are also defended against enemies, at a cost to growth rate. We tested these hypotheses using observations of 706 plant populations of over 500 species before and following identical fertilisation and fencing treatments at 39 grassland sites...

Ecosystem-based planning and management have stimulated the need to gather sociocultural values and human uses of land in formats accessible to diverse planners and researchers. Human Ecology Mapping (HEM) approaches offer promising spatial data gathering and analytical tools, while also addressing important questions about human-landscape connections. This article reviews and compares the characteristics of three HEM approaches that are increasingly used in natural resource management contexts, each focused on a particular aspect of human environmental interactions. These aspects include...

Current knowledge concerning the interactions between forest disturbances such as fire and insect defoliation is limited. Wildfires and prescribed burns may influence the intensity and severity of insect outbreaks by affecting the vigor of residual trees, altering aspects of stand structure and abundance of preferred hosts, and by changing the physical environment within forest stands. Prescribed burn timing and frequency are particularly important aspects of the fire regime to consider because they can alter numerous aspects of tree vigor, stand structure, and environmental conditions,...

Large river basins transfer the water signal from the atmosphere to the ocean. Climate change is widely expected to alter streamflow and potentially disrupt water management systems. We tested the ecological resilience—capacity of headwater ecosystems to sustain streamflow under climate change—and the engineering resilience—capacity of dam and reservoir management to overprint a climate change signal—in seven sub-basins of the Columbia River from 1950 to 2011. Sub-basins had a headwater gauge above dams with a long-term streamflow record and a nearby climate station with a long-term record...

Stem exclusion and understory reinitiation are commonly described, but poorly understood, stages of forest development. It is assumed that overstory trees exert strong controls on understory herbs and shrubs during the transition from open- to closed-canopy forests, but long-term observations of this process are rare. We use long-term data from 188 plots to explore patterns and correlates of variation in understory richness and abundance 15–45 years after clear-cut logging and burning of two experimental watersheds in western Oregon, USA. We test whether variation in the temporal dynamics...

We investigated scaling of conservative solute transport using temporal moment analysis of 98 tracer experiments (384 breakthrough curves) conducted in 44 streams located on five continents. The experiments span 7 orders of magnitude in discharge (10-3 to 103 m3/s), span 5 orders of magnitude in longitudinal scale (101 to 105 m), and sample different lotic environments—forested headwater streams, hyporheic zones, desert streams, major rivers, and an urban manmade channel. Our meta-analysis of these data reveals that the coefficient of skewness is constant over time (CSK = 1.18 ±0.08, R2 >...

In this technical note, a steady-state analytical solution of concentrations of a parent solute reacting to a daughter solute, both of which are undergoing transport and multirate mass transfer, is presented. Although the governing equations are complicated, the resulting solution can be expressed in simple terms. A function of the ratio of concentrations, In (daughter/parent + P), can be used as a metric of mass transfer and reaction if the reactions are mostly confined to the immobile domain, where P is the ratio of production of daughter to decay of parent. This metric is applied with...

Some Great Basin urban areas in Utah and Nevada exhibit climatic conditions that make it difficult for all but the toughest landscape plants to thrive without providing supplemental water. These areas are found at elevations from 4,000 feet to 6,000 feet in USDA cold-hardiness zones 6 and 7. Soils are often poor and gravelly, containing less than 1 percent organic matter. Soil pH ranges from 6.5 to over 7.5, and some areas have salinity levels that exceed the limits of tolerance for many plants. Precipitation is less than 10 inches per year, and drying winds are persistent much of the...

Basin wildrye (Leymus cinereus [Scribn. & Merr.] A. Love) is an important perennial, hardy, long-lived, cool season C3 native grass of rangeland plant communities throughout much of western United States and Canada. All classes of livestock and wildlife, including large and small birds and mammals, utilise the grass year round for food and protection due to its 2-3 m tall, stiff stature which pro-vides standing winter cover. Though occurring in precipitation areas of 150-500 mm and elevations of 600 to 3,000 m, it is usually found in deep, well-drained soils of high water holding capacity...

The microclimatic requirements for successful seedling establishment are much more restrictive than those required for adult plant survival. The purpose of the current study was to use hydrothermal germination models and a soil energy and water flux model to evaluate intra- and interannual variability in seedbed microclimate relative to potential germination response of six perennial grasses and cheatgrass. We used a 44-yr weather record to parameterize a seedbed microclimate model for estimation of hourly temperature and moisture at seeding depth for a sandy loam soil type at the Orchard...