Treesearch

The Ozark Highlands Plateau of southern Missouri and northern Arkansas is home to more than 2,000 vascular plant species and at least 15,000 species of various animals of which over 150 are endemic. The Nation's most significant karst region occurs here, boasting the most springs of any state and more than 6,000 caves. Missouri's Ozark biota is sorted into 65 distinctive mappable natural communities. Misconstrued as "oak-hickory forest", analysis of Missouri's historic vegetation, fire history studies, plant adaptations, and responses to fire management reveal that the Ozark's was a...

We investigated effects of a human-altered fire regime and wind storms on persistence of disjunct oak-shortleaf pine vegetation occurring along 5.5 km of xeric habitat on the east bluffs of the Mississippi River in Union County, IL. In 2009, we resampled vegetation transects established in seven stands in 1954 and obtained 26 cross sections containing fire scars from pines downed by windstorms in 2008 and 2009. These scars revealed 81 years with fires between 1767-1991. Only presettlement fire years corresponded with drought conditions indicated by the Palmer Drought Severity Index. After...

Over the last 40 years, prescribed fire programs on National Forest lands have grown from relatively insignificant to a major emphasis area of natural resource management. During this same period, social, economic, and cultural values have greatly changed. The public's environmental awareness has likewise grown. How prescribed fire programs in Arkansas and Oklahoma have fared during this time is a subject of some interest. Scientific research in fire ecology and fire history has aided managers, enabling them to better explain the need for prescribed fire programs.

Sonic anemometers are capable of measuring the wind speed in all three dimensions at high frequencies (10­50 Hz), and are relied upon to estimate eddy-covariance-based fluxes of mass and energy over a wide variety of surfaces and ecosystems. In this study, wind-velocity measurement errors from a three-dimensional sonic anemometer with a nonorthogonal transducer orientation were estimated for over 100 combinations of angle-ofattack and wind direction using a novel technique to measure the true angle-of-attack and wind speed within the turbulent atmospheric surface layer. Corrections to the...

Recent bark beetle outbreaks in western North America have been widespread and severe. High tree mortality due to bark beetles affects the fundamental ecosystem processes of primary production and decomposition that largely determine carbon balance (Kurz et al. 2008, Pfeifer et al. 2011, Hicke et al. 2012). Forest managers need accurate data on beetle-induced tree mortality to make better decisions on how best to remediate beetle-affected forests and restore healthy ecosystem services (Negron et al. 2008). Discrete-return LiDAR measures canopy height and density, and LiDAR intensity...

A fundamental equation of eddy covariance (FQEC) is derived that allows the net ecosystem exchange (NEE) Ns of a specified atmospheric constituent s to be measured with the constraint of conservation of any other atmospheric constituent (e.g. N2, argon, or dry air). It is shown that if the condition [equation, see PDF] is true, the conservation of mass can be applied with the assumption of no net ecosystem source or sink of dry air and the FQEC is reduced to the following equation and its approximation for horizontally homogeneous mass fluxes: [equation, see PDF]. Here w is vertical...

Different analytical techniques used on the same data set may lead to different conclusions about the existence and strength of genetic structure. Therefore, reliable interpretation of the results from different methods depends on the efficacy and reliability of different statistical methods. In this paper, we evaluated the performance of multiple analytical methods to detect the presence of a linear barrier dividing populations. We were specifically interested in determining if simulation conditions, such as dispersal ability and genetic equilibrium, affect the power of different analytica...

Restoration projects can have varying goals, depending on the specific focus, rationale, and aims for restoration. When restoration projects use project-specific goals to define activities and gauge success without considering broader ecological context, determination of project implications and success can be confounding. We used case studies from the Middle Rio Grande (MRG), southwest USA, to demonstrate how restoration outcomes can rank inconsistently when narrowly-based goals are used. Resource managers have chosen MRG for restoration due to impacts to the natural flood regime, reduced...

Lizards from the Sceloporus undulatus complex have been the subject of many studies on lizard ecology (Hager 2001; Rosenblum 2006; Rosenblum et al. 2007), behavior (Hein and Whitaker 1997; Robertson and Rosenblum 2009), and reproduction (Vinegar 1975; Robertson and Rosenblum 2010). However, genetic data (Leache and Reeder 2002) support reallocation of the subspecies of the S. undulatus complex (e.g., S. undulatus consobrinus, S. u. tristichus, and S. u. cowlesi) as distinct species (e.g., S. consobrinus. S. tristichus, and S. cowlesi). One of these species, S. cowlesi, occupies a variety...

Herbivory by domestic and wild ungulates can dramatically affect vegetation structure, composition and dynamics in nearly every terrestrial ecosystem of the world. These effects are of particular concern in forests of western North America, where intensive herbivory by native and domestic ungulates has the potential to substantially reduce or eliminate deciduous, highly palatable species of aspen (Populus tremuloides), cottonwood (Populus trichocarpa), and willow (Salix spp.). In turn, differential herbivory pressure may favor greater establishment of unpalatable conifers that serve as...