Treesearch

The inter-annual variability of southerly low-level jets (SLLJs) over North America during the warm (April–September) and cool (October–March) seasons is investigated. SLLJ occurrences over a 31-year period (1979–2009) were identified from the North American Regional Reanalysis (NARR) vertical wind profiles. The first empirical orthogonal function (EOF) modes of the SLLJ frequency during the warm and cool seasons account for about 30 and 20% of the total variance, respectively. Both modes can be interpreted as a strengthening or weakening of the core area of SLLJ anomalies. The principal...

Quantitative measures of site productivity provide critical information for management of forests. In this study, models were developed to predict site index (the average height of dominant/codominant trees at a specified base age) using data that encompassed the entire northeastern United States and a wide range of stand conditions. Regression analyses were conducted for 22 tree species/groups, with models utilizing breast-height age being presented. For 15 remaining species/groups having relatively low frequency of occurrence, empirical evaluations were performed to determine which of...

There is an increasing need for approaches to determine reference emission levels and implement policies to address the objectives of Reducing Emissions from Deforestation and Forest Degradation, plus improving forest management, carbon stock enhancement and conservation (REDDC). Important aspects of approaching emissions reductions include coordination and sharing of technology, data, protocols and experiences within and among countries to maximize resources and apply knowledge to build robust monitoring, reporting and verification (MRV) systems. We propose that enhancing the multiple...

Several forest non-native pests and pathogens that are among the most frequently cited invasive species worldwide represent serious economic and conservation concerns for the forest ecosystems in their region of introduction. Such organisms can have adverse impacts on the yield of marketable wood products, such as timber and pulp, as well as non-wood forest products, such as nuts, fruits, and seeds. However, quantitative data about impacts on forest market resources are rare and usually restricted in time and space. Moreover, information on regional impacts, and aggregate data including...

The related challenges of predictions in ungauged basins and predictions in ungauged climates point to the need to develop environmental models that are transferable across both space and time. Hydrologic modeling has historically focused on modelling one or only a few basins using highly parameterized conceptual or physically based models. However, model parameters and structures have been shown to change significantly when calibrated to new basins or time periods, suggesting that model complexity and model transferability may be antithetical. Empirical space-for-time models provide a...

Swiss needle cast (SNC), a foliage disease of Douglas-fir (Pseudotsuga menziesii), is caused by the physical blockage of the stomata by pseudothecial ascocarps of the fungus Phaeocryptopus gaeumannii. Occlusion of the stomata results in a decrease in the ability of the host to exchange gases with the environment leading to reduced carbon assimilation (Manter et al., 2000). This results in premature foliage loss and subsequent growth reduction due to decreased photosynthetic leaf area (Manter et al., 2003). Prior to the 1980’s, it was known to cause severe disease only in exotic Douglas-fir...

Light Detection and Ranging (LiDAR) has become a common means for predicting key forest structural attributes. The aim of this study was to explore the relationship between individual tree LiDAR-based metrics and field data on tree attributes from a tropical rainforest in Peninsular Malaysia, to assess the correlation between LiDAR and field data at the individual-tree level for aboveground biomass (AGB) estimates. The model was developed using multiple regression analysis, with a non-linear power model being used to fit the predictive models. The AGB model was developed based on estimated...

Information on reproduction is essential to understanding population dynamics and developing conservation plans for wildlife. However, research on reproduction with species in the Martes Complex in wild settings can be challenging due to their low population densities, elusive behaviours, and tendency to hide young in cryptic den structures such as tree cavities or snow burrows. Answering basic questions about life history parameters in the Mattes Complex involves specialized techniques that have been increasingly refined by researchers over the last half-century. We present a review of...

Many western North American forest types have experienced considerable changes in ecosystem structure, composition, and function as a result of both fire exclusion and timber harvesting. These two influences co-occurred over a large portion of dry forests, making it difficult to know the strength of either one on its own or the potential for an interaction between the two. In this study, we used contemporary remeasurements of a systematic historical forest inventory to investigate forest change in the Sierra Nevada. The historical data opportunistically spanned a significant land management...

Quaking aspen (Populus tremuloides Michx.), a widespread and keystone tree species in North America, experienced heat and drought stress in the years 2002 and 2003 in the southwestern United States. This led to widespread aspen mortality that has altered the composition of forests, and is expected to occur again if climate change continues. Understanding interactions between aspen and its environments is essential to understanding future mortality risk in forests. Polyploidy, which is common in aspen, can modify plant structure and function and therefore plant–environment interactions, but...