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Synopsis: The goal of this study was to examine contaminant loadings associated with stormwater runoff from recently burned areas in urban fringe areas of southern California, to derive regional patterns of runoff and contaminant loadings in this context. Postfire stormwater runoff was sampled from five wildfires that each burned between 115 and 658 km2 of natural open space between 2003 and 2009. The area is characterized by classic Mediterranean climate conditions of relatively mild to cool wet winter and warm to hot dry summers. Between two and five storm events were sampled per site over the first one to two years following the fires for basic constituents, metals, nutrients, total suspended solids, and polycyclic...
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Synopsis: Researchers analyzed variation in crop pollination services provided by native, unmanaged, bee communities on organic and conventional farms situated along a gradient of isolation from natural habitat. Pollination services from native bees were significantly, positively related to the proportion of upland natural habitat in the vicinity of farm sites, but not to any other factor studied, including farm type, insecticide usage, field size and honeybee abundance. The scale of this relationship matched bee foraging ranges. Stability and predictability of pollination services also increased with increasing natural habitat area. This strong relationship between natural habitat area and pollination services...
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Synopsis: The individual species and aggregate community contributions of native bees to crop pollination are documented, on farms that varied both in their proximity to natural habitat and management type (organic versus conventional). On organic farms near natural habitat, we found that native bee communities could provide full pollination services even for a crop with heavy pollination requirements (e.g., watermelon, Citrullus lanatus), without the intervention of managed honey bees. Agricultural intensification diminished these pollination services by roughly 3- to 6-fold. The decline of native bee pollination services with agricultural intensification resulted in significant reductions in both diversity and...
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Synopsis: This study examines the influence of landscape fragmentation on trophic cascades in southern California. Results indicate that, as habitat fragmentation negatively affects the persistence of coyote populations, the abundance of smaller meso-predators increase, resulting in higher mortality rates in scrub-breeding birds. Fragment size was a strong indicator of coyote abundance, and coyote abundance was a strong indicator of bird diversity, as coyotes kept down the number of meso-predators that prey on birds. The positive effect of fragment area and the negative effect of fragment age were the strongest determinants of bird diversity in this system. Conclusions: Fragment size correlates with coyote abundance,...
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Synopsis: Wildfires can negatively affect water quality by altering watershed hydrology and increasing sediment and nutrient delivery to surface waters. The Angora Fire (summer of 2007) was the largest and most severe wildfire in recent history within the Lake Tahoe basin of the Sierra Nevada. The fire burned 839 ha within the watershed (56% of the total watershed area), with 22% of the watershed affected by a high severity burn. To determine the watershed response to fire and assess the potential for downstream impacts of nutrient and sediment delivery to Lake Tahoe, the post-fire hydrology and stream water chemistry was monitored for 2 years at four locations along the length of Angora Creek, a perennial stream...
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Synopsis: Because recent bark beetle population eruptions have exceeded the frequencies, impacts, and ranges documented during the previous 125 years, researchers have been prompted to determine what factors trigger broad scale outbreaks, and how do these factors interact? How do human activities, such as forest management, alter these interactions, and thus the frequency, extent, severity, and synchrony of outbreaks? Extensive host tree abundance and susceptibility, concentrated beetle density, favorable weather, optimal symbiotic associations, and escape from natural enemies must occur jointly for beetles to surpass a series of thresholds and exert widespread disturbance. Eruptions occur when key thresholds are...
    map background search result map search result map Water quality response to the Angora Fire, Lake Tahoe, California Cross-scale drivers of natural disturbances prone to anthropogenic amplification: the dynamics of bark beetle eruptions Crop pollination from native bees at risk from agricultural intensification The area requirements for an ecosystem serivce: crop pollination by native bee communities in California Stormwater contaminant loading following southern California wildfires Mesopredator release and avifaunal extinctions in a fragmented system. Water quality response to the Angora Fire, Lake Tahoe, California Crop pollination from native bees at risk from agricultural intensification The area requirements for an ecosystem serivce: crop pollination by native bee communities in California Stormwater contaminant loading following southern California wildfires Mesopredator release and avifaunal extinctions in a fragmented system. Cross-scale drivers of natural disturbances prone to anthropogenic amplification: the dynamics of bark beetle eruptions