Treesearch

Historical fire exclusion, intensive logging of large trees of fire-tolerant species, and even-aged management have contributed to widespread decline of mature/old-growth coniferous forests across the Western USA. To investigate silvicultural approaches for reducing disturbance risk while accelerating restoration of mature/old-growth forest characteristics, we used 20-year data from the Goosenest Adaptive Management Area study in Northern California, USA. Established to evaluate the alternatives for reducing fuels and accelerating the development of late-seral characteristics in ponderosa...

Many non-native tree species are recognized as problematic to ecosystems they have invaded, and subsequent control efforts have met with varying levels of success. Falcataria falcatais a fast-growing, N-fixing tree that has aggressively invaded landscapes across the Hawaiian Archipelago. Due to their ability to alter Hawaiʻi’s native forest ecosystems, large stature at maturity, and potential for catastrophic tree fall, F. falcatastands pose threats to Hawaiʻi’s native forests, residential communities, and agricultural lands. We investigated responses to chemical control of F. falcatastands...

In forested, seasonally dry watersheds, winter rains commonly replenish water storage deficits in the vadose zone before recharging underlying hillslope groundwater systems that sustain streamflow. However, the relative inaccessibility of the subsurface limits our understanding of how groundwater recharge is moderated by vadose zone storage deficits generated by plant-water uptake. Here, we compare groundwater recharge inferred from the storage-discharge relationship with independent, distributed estimates of deficits across 12 undisturbed California watersheds. We find accrued dry season...

The southwestern pine beetle, Dendroctonus barberi Hopkins (Coleoptera: Curculionidae: Scolytinae), is a significant pest of ponderosa pine (Pinus ponderosa) in the Southwestern United States. Pinyon pine (Pinus edulis) and Douglas-fir (Pseudotsuga menziesii var. glauca) have also been recorded as occasional hosts. The southwestern pine beetle occurs in Arizona, Colorado, New Mexico, Nevada, Utah, and Texas, and in the Mexican States of Chihuahua, Coahuila, Durango, Nuevo Leon, and Tamaulipas. Its largest impacts occur in Arizona, New Mexico, and Texas. Southwestern pine beetles play a...

Rapid changes in landscape structure can disrupt the ecology and life history of species of conservation concern. Shifting climate, land-use, and disturbance regimes are generating novel landscape patterns, and it is unclear how these novel conditions may affect imperiled species. In the Sierra Nevada of California, USA, extensive drought-induced tree mortality has rapidly altered forest structure and local microclimates, with potential implications for forest-dependent species. We evaluated the effects of shifting land cover, forest structure, and abiotic conditions on the space-use of...

Density management diagrams (DMDs) are a fundamental forest management tool. However, these tools were primarily developed for even-aged stands and may not incorporate important site effects. Accommodating different stocking constraints during stand development across broad ranges of site effects could help tailor reforestation and thinning prescriptions to local conditions. For that purpose, this report introduces a set of site-sensitive DMDs for managing both even- and uneven-aged California mixed-conifer stands. By consulting maps of aridity and nitrogen deposition summarized by...

Mechanistic habitat assessment models have long been used for stream fish, especially drift-feeding salmonids. Most of these models assess habitat value as the rate of net energy intake (growth) obtained by a fish feeding in a habitat unit. However, the fitness value of habitat and the willingness of fish to occupy it also depend on predation risk: habitat is not valuable if it offers high growth but also high risk. Methods for modeling how predation risk varies with characteristics of habitat and fish are much less developed than those for modeling net energy intake. We present approaches...

Climate change is reducing the extent of cold aquatic habitats and their unique biodiversity in mountain areas. However, a variety of cold rocky landforms (CRLs) are thermally buffered and feed cold springs (<2 °C) that may represent climate refugia for cold-adapted organisms. These landforms, hitherto overlooked by freshwater research, include rock glaciers, debris-covered glaciers, talus slopes, protalus ramparts, and young moraines. Here, we investigated the warm-season water temperature of 228 springs from clean (ice) glaciers, CRLs, and reference slopes (not sourced by any of these...

The stability of seasonally dry Western mixed-conifer forests is threatened by the history of fire suppression, logging, and now increasing climate-driven aridity. Durable aboveground carbon storage in living trees–a key ecosystem service of these fire-adapted forests–is at risk due to the disruption of natural fire cycles. Restoring the relationship between fire and forest structure is essential for long-term resilience. Fuel and density reduction treatments can help reestablish this balance by reducing fire severity and enhancing forest function. We evaluated the effectiveness of 216...

Socio-ecological resilience recognizes that humans and nature are inextricably connected, and humans play an increasingly central and active role in determining the fate of ecosystem resilience. For decades, managers and scientists have sought effective approaches for managing forest composition, structure, and processes to improve resilience properties. Management actions that encompass large landscapes tend to engage a broad spectrum of stakeholders and perspectives about resilience. Translating resilience concepts into concrete and measurable objectives and outcomes and effectively...