Treesearch

Fire in high-elevation forest ecosystems can have severe impacts on forest structure, function and biodiversity. Using a 105-year data set, we found increasing elevation extent of fires in the Sierra Nevada, and pose five hypotheses to explain this pattern. Beyond the recognized pattern of increasing fire frequency in the Sierra Nevada since the late 20th century, we find that the upper elevation extent of those fires has also been increasing. Factors such as fire season climate and fuel build up are recognized potential drivers of changes in fire regimes. Patterns of warming climate and...

Forests are a significant part of the global carbon cycle and are increasingly viewed as tools for mitigating climate change. Natural disturbances, such as fire, can reduce carbon storage. However, many forests and dependent species evolved with frequent fire as an integral ecosystem process. We used a landscape forest simulation model to evaluate the effects of endangered species habitat management on carbon sequestration. We compared unmanaged forests (control) to forests managed with prescribed burning and prescribed burning combined with thinning. Management treatments followed...

Temporal variation represents an important component in understanding the structure of ecological communities and species coexistence. We examined calling phenology of an assemblage of anurans in the Gran Chaco ecoregion of Bolivia by deploying automated recording devices to document nocturnally vocalizing amphibians nightly at seven ponds from 20 January 2011 until 31 October 2011. Using logistic regression, we modelled the relationships between temperature, rainfall and photoperiod with calling activity. There was a distinct seasonal effect with calling activity concentrated in the rainy...

Forests are vital components of the urban landscape because they provide ecosystem services such as carbon sequestration, storm-water mitigation, and air-quality improvement. To enhance these services, cities are investing in programs to create urban forests. A major unknown, however, is whether planted trees will grow into the mature, closed-canopied forest on which ecosystem service provision depends. We assessed the influence of biotic and abiotic land management on planted tree performance as part of urban forest restoration in New York City, U.S.A. Biotic treatments were designed to...

Drosophila suzukii Matsumura, often called spotted wing drosophila, is an exotic vinegar fly that is native to Southeast Asia and was first detected in the continental United States in 2008. Previous modeling studies have suggested that D. suzukii might not survive in portions of the northern United States or southern Canada due to the effects of cold. As a result, we measured two aspects of insect cold tolerance, the supercooling point and lower lethal temperature, for D. suzukii summer-morph pupae and adults and winter-morph adults. Supercooling points were compared to adults of Drosophil...

Laurel wilt disease (LWD), caused by the fungus Raffaelea lauricola and transmitted by Xyleborus glabratus (Redbay Ambrosia Beetle [RAB]), has killed millions of Persea borbonia (Redbay) trees throughout the southeastern Coastal Plain. Laurel wilt also has been detected in Sassafras albidum (Sassafras) in widely dispersed locations across the southeastern US. We established long-term laurel wilt disease-progression plots in Redbayand Sassafras stands in southeastern Georgia and monitored them through 4 years to document mortality rates and investigate long-term...

The East Bay Regional Park District maintains the largest urban park system in the United States, comprising over 45 000 ha, and more than 1900 km of trails, with extensive forests bordering residential areas. Sudden oak death (SOD), caused by the introduced oomycete Phytophthora ramorum, was first detected in a district park in 2001. Both increased fire risk and structural failure of large trees located near sites with heavy public usage are concerns for managers. Management requires reliable data about the location and severity of the disease. To produce disease incidence and risk maps,...

From 2000 through 2012, we collected annual observations on disease symptoms and stand conditions in 128 coast live oak plots in forests affected by sudden oak death (SOD), caused by the introduced pathogen Phytophthora ramorum. Elevated rainfall in one or both of the previous wet seasons was associated with pulses of new infections. However, persistent differences in infection rates between nearby locations and among plots within locations show that tree and site specific factors influence disease risk on the local scale. Because California bay is the primary source of P. ramorum spores...

In response to the wave of sudden oak death (SOD), caused by Phytophthora ramorum, sweeping the redwood forest ecosystems of California's North Coast, the role of foresters and other ecosystem managers is being tested. On Bear Flat Tree Farm, near Healdsburg, California, Forest, Soil & Water, Inc. (FSW) has conducted a multi-year, multi-treatment approach to take advantage of SOD. Because the seral stage of tanoak is a component of hardwood dominance intermediary between brush and conifers, FSW has used the oncoming wave of SOD to accelerate the ecosystem towards redwood (Sequoia sempervire...

The unmitigated risk potential of the introduction of exotic insects and pathogens to Hawai'i was evaluated for its impact on native plants, specifically Acacia koa, Cibotium spp., Dicranopteris linearis, Diospyros sandwicensis, Dodonaea viscosa, Erythrina sandwicensis, Leptecophylla tameiameiae, Metrosideros polymorpha, Myoporum sandwicense, Pandanus tectorius, Scaevola spp., Sophora chrysophylla, and Vaccinium spp. Assessments were made by estimating the likelihood and consequences of introduction of representative insects and pathogens of concern. Likely pathways of introduction were...