Treesearch

Ammonia (NH3), nitric oxide (NO), nitrogen dioxide (NO2), nitric acid (HNO3), and ozone (O3) were measured in summers of 2012 and 2013 with passive samplers. Nine monitoring sites were on W-E transect (511 to 3490 m) across central Sierra Nevada Mountains (SNM), and five sites on elevational gradient (1237 to 4346 m) in White Mountains (WM) of California. Levels of pollutants were similar in 2012 and 2013 in all sites. NH3, NO2, and HNO3 were highest near highly polluted Central Valley of California (CVC): maximum summer season means 7.8 μg m−3, 3.0 ppb, and 3.0 μg m−3, respectively....

Total nitrogen (N) deposition has declined in many parts of the U.S. and Europe since the 1990s. Even so, it appears that decreased N deposition alone may be insufficient to induce recovery from the impacts of decades of elevated deposition, suggesting that management interventions may be necessary to promote recovery. Here we review the effectiveness of four remediation approaches (prescribed burning, thinning, liming, carbon addition) on three indicators of recovery from N deposition (decreased soil N availability, increased soil alkalinity, increased plant diversity), focusing on...

Group-selection silviculture has many benefcial attributes and has increased in application over the past 30 years. One diffculty with group-selection implementation is the designation of group openings within a stand to achieve a variety of complex management goals. This study presents a new method for utilizing geospatial census stem map data derived from airborne lidar in a heuristic environment to generate and select from treatment solutions that best meet management objectives in an effcient manner. The method successfully generated candidate treatment solutions over two entries that...

Annually dated tree-rings of 509 live and deadwood limber pine (Pinus flexilis) samples from the semi-arid Wassuk Range, Nevada, yielded a 3996-yr record extending from 1983 BC to AD 2013. Correlations of radial growth with climate were positive for water relations and negative for summer temperatures. Long-term trends of ring-width corresponded to climate variability documented from other proxies, including low growth during the Late Holocene Dry Period and Medieval Climate Anomaly (MCA) and elevated growth during cool, wet periods of the Neoglacial and Little Ice Age. Spline fit of the...

Reforestation with native species and resulting understory succession can exert important influences on soil organic matter (SOM) storage and chemistry, but a mechanistic understanding of these effects is lacking. We studied different aged Masson pine (Pinus massoniana L.) plantations with and without the understory fern, Dicranopteris dichotoma (Thunb.) Berhn., in subtropical China to assess how SOM over a 30 year sequence of pine growth and fern expansion. To do this, we measured total SOM, lignin-derived phenols, soil carbon (total C and 13C), soil nitrogen (total N and 15N), and soil...

We studied benthic macroinvertebrate communities in 12 mid‐elevation mountain streams in the Sierra Nevada, California. Data were collected at nine times (seven springs and two autumns) over a 14‐year period of variable hydrological conditions, including years of flood and extreme unprecedented drought. The taxonomic and trait structures of communities were similar during wet and average springs but became increasingly different as drought continued and smaller streams became intermittent. The density of total invertebrates, primarily chironomids, increased during the drought years, but...

The lateral destination and potential decomposition of soil organic matter mobilized by soil erosion depends on factors such as the amount and type of precipitation, topography, the nature of mobilized organic matter (OM), potential mixing with mineral particles, and the stabilization mechanisms of the soil OM. This study examined how the relative distribution of carbon (C) and nitrogen (N) in different OM fractions varied in soils from eroding slopes and in eroded sediments in a series of low‐order forested catchments in the western Sierra Nevada, California. We found that precipitation...

La limitación de recursos para el manejo de incendios forestales requiere priorizar áreas forestales para su protección. Para ello se usan criterios como riesgo de incendios. Con los que se generan mapas temáticos para apoyar la toma de decisiones. Sin embargo, previo a esto, se requiere de su validación, bajo un proceso estadísticamente robusto. No obstante, actualmente no se cuenta con uno, por lo que se debe partir del aspecto básico, como es la definición de la unidad de muestreo. Lo cual fue el objetivo del presente trabajo, donde se probaron diferentes tamaños de sitios de referencia...

Los servicios ambientales y los bienes paisajísticos son raramente incorporados en la valoración de daños y perjuicios ocasionados por los incendios forestales, aunque pueden constituir una gran proporción del total. En algunos incendios ocasionados dentro de Parques Naturales se han datado daños muy superiores en estos recursos que en los recursos tangibles. La valoración económica de los daños ocasionados sobre los servicios ambientales y bienes paisajísticos requiere del empleo de técnicas indirectas, como la valoración contingente o el método coste viaje. El excedente del consumidor es...

La generación de información sobre ambientes del fuego y camas de combustibles forestales es fundamental para conocer el comportamiento de los incendios forestales. Desarrollar modelos experimentales en laboratorios puede ser costoso y tardado. Una alternativa es aprovechar el conocimiento empírico de personas con experiencia en el manejo del fuego y combate de incendios forestales. Con el objetivo de recuperar información empírica sobre el ambiente de fuego para evaluar y describir las camas de combustibles forestales en los diferentes ecosistemas de México, se llevaron a cabo cuatro...