Treesearch

Most studies of fire-regime changes in western North American forests rely on a reference period that pre-dates Euro-American settlement. Less is known about fire-regime changes relative to the early onset of major change agents, i.e. fire suppression and timber harvesting. We digitised ledgers that contained over 18 000 individual fire records from 1911 through 1924 (early suppression period). We performed analyses comparing a subset of these fire records, largely in mixed-conifer forests, to similar records from 2002 through 2015 (contemporary period). Mapped ignition frequencies...

Montane forests in the High Tatra Mountains are exposed to high ambient ozone (O3) concentrations that may adversely affect the physiological processes and health of plants. This study presents the modelled results of the phytotoxic ozone dose (POD) for dwarf mountain pine (P. mugo) in 2016. POD metrics were calculated using the deposition model DO3SE, with O3 concentration and meteorological data measured in three altitudinal zones. In addition, maximal stomatal conductance (Gmax) derived from gasometric field measurement in local conditions was included in the model. Field measurements...

Tall trees and vertical forest structure are associated with increased productivity, biomass and wildlife habitat quality. While climate has been widely hypothesized to control forest structure at broad scales, other variables could be key at fine scales, and are associated with forest management. In this study we identify the environmental conditions (climate, topography, soils) associated with increased tree height across spatial scales using airborne Light Detection and Ranging (LiDAR) data to measure canopy height. The study was conducted over a large elevational gradient from 200 to...

Knowledge of how tree groups and gaps are formed and maintained in frequent-fire forests is key to managing for heterogeneous and resilient forest conditions. This research quantifies changes in tree group and gap spatial structure and abundance of ponderosa pine (Pinus ponderosa) and California black oak (Quercus kelloggii) with stand development after wildfires in 1990 and 1994 in an old-growth forest in the Ishi Wilderness, southern Cascades, California. Forest demography and tree group and gap structure were quantified by measuring, mapping, and aging trees in six 1-ha permanent plots...

Ecological restoration projects that include reforestation require that land managers select appropriate source of seeds for long-term persistence. In California, the standard approach for making this choice is based on seed zone and elevational band, both geographically-based measures. However, given the pace of contemporary climate change, populations previously adapted to local conditions may become increasingly mismatched to the changes in climate. If there is a lag in adaptation, current seed zones which assume local is best, would be less useful for reforestation guidelines. Here we...

Prescribed (i.e., controlled) burning is a common practice used in many vegetation types in the world to accomplish a wide range of land management objectives including wildfire risk reduction, wildlife habitat improvement, forest regeneration, and land clearing. To properly apply controlled fire and reduce unwanted fire behavior, an improved understanding of fundamental processes related to combustion of live and dead vegetation is needed. Since the combustion process starts with pyrolysis, there is a need for more data and better models of pyrolysis of live and dead fuels. In this study,...

To forestall loss of ecological values associated with forests, land managers need to consider where and when to prioritize active reforestation following major disturbance events. To aid this decision-making process, we summarize recent research findings pertaining to the Sierra Nevada region of California, USA to identify contexts in which active reforestation or passive recovery may best promote desirable post-fire ecological trajectories. Based on our synthesis, we suggest conceptual frameworks for assessing landscape conditions and determining areas that may be the highest priorities...

Estimating nitrogen (N) deposition to terrestrial ecosystems is complicated by the multiple forms and routes of N loading from the atmosphere.We used the integrated total nitrogen input (ITNI) method, which is based on the principle of isotope dilution within a plant-liquid-sand system, to quantify N inputs to coastal sage scrub ecosystems in Riverside, California. Using the ITNI method, we measured atmospheric N deposition of 29.3 kg N ha−1 yr−1 over a range of aboveground plant biomass of 228 to 424 g m−2. From 85 to 96% of the atmospheric N inputs were taken up by plants in the ITNI...

In this paper, we propose that spiritual approaches rooted in the practice of Hawai‘i ritual provide a powerful portal to revealing, supporting, and enhancing our collective aloha (love, fondness, reciprocity, as with a family member) for and dedication to the places and processes that we steward. We provide a case study from Hawai‘i, where we, a group of conservation professionals known as Hālau ‘Ōhi’a, have begun to foster a collective resurgence of sacred commitment to the places and processes we steward through remembering and manifesting genealogical relationships to our landscapes...

Using 27 years of point count data collected at the San Joaquin Experimental Range, Madera County, California, we modeled the importance of weather and climate variables on annual variability in the abundance of 35 bird species, to assess the potential responses of birds to changing environmental conditions. We used semi-parametric Poisson generalized additive models (GAM) with smoothing functions to explore relationships between bird abundance and the independent climatic and weather variables and to extract the best parametric polynomial model. We then selected among three parametric...