Treesearch

Pollution of surface water with harmful chemicals and eutrophication of rivers and lakes with excess nutrients are serious environmental concerns. The U.S. Environmental Protection Agency (USEPA) estimated that 53% of the 27% assessed rivers and streams miles and 69% of the 45% assessed lakes, ponds, and reservoirs acreage in the nation are impaired (USEPA, 2010). In Mississippi, 57% of the 5% assessed rivers and streams miles are impaired (USEPA, 2010). These impairment estimates may increase when assessments of more water bodies are performed and water quality criteria are improved. The...

Based on cross-dated increment cores, yearly diameters of trees were reconstructed for 21 laurels (Cordia alliodora) growing in a natural secondary forest on Gigante Peninsula, Panama. From this sample of dominant-codominant trees, ages were 14–35 years with an average of 25 years. Growth typically slowed at 7 years old, indicating effects of competition from closure of gaps in the canopy. Rate of growth in diameter was modeled using the Bertalanffy-Richards growth function. Four patterns of growth were detected, of which 57% were sigmoidal, 19% were convex, 10% were monomolecular, and 14%...

Constructed wetland (CW) and constructed pond (CP) are commonly utilized for removal of excess nutrients and certain pollutants from stormwater. This study characterized shallow groundwater quality for pre- and post-CW and CP system conditions using data from monitoring wells. Results showed that the average concentrations of groundwater phosphorus (P) decreased from pre-CW to post-CW but increased from pre-CP to post-CP. The average concentrations of groundwater total Kjeldahl nitrogen and ammonium (NH4+) increased from pre-CW (or CP) to post-CW (or CP), whereas the average concentrations...

Invertebrates and plants are among the most ubiquitous and abundant macroscopic organisms in aquatic ecosystems; they dominate most habitats in both diversity and biomass and play central roles in aquatic food webs. Plants regulate and create habitats for a wide array of organisms (Cooke et al. 2005). Snail grazing and bivalve filtering profoundly alter habitats and communities (Harvey and Hill 1991; Vaughn and Hakenkamp 2001). Aquatic habitats in North America support extremely diverse floras and invertebrate faunas; groups such as crayfishes and freshwater mollusks reach their highest...

Duck has been used as a non-chemical control method against Pomacea canaliculata Lamarck, but little is known about its principles that underlie the control of snail populations. An indoor experiment was initially used to observe the predation potential of ducks, followed by replicated field trials. In the indoor studies, ducks effectively preyed on juvenile snails, but had a weak predatory effect on large snails and egg clusters. In the field, application of a rice-duck mutualism system significantly reduced the numbers of snails (especially number of immature individuals), number of...

Black-tailed prairie dogs (Cynomys ludovicianus) are considered a keystone species in grassland ecosystems. Through their burrowing activities, they conspicuously alter grassland landscapes and provide foraging, shelter and nesting habitat for a diverse array of grassland species, in addition to serving as prey for the endangered black-footed ferret (Mustela nigripes). Due to a combination of factors, the lands currently occupied by prairie dog colonies are thought to represent less than 10% of their historical range. Black-tailed prairie dogs have difficulty colonizing areas with tall...

The invasive non-native earthworm Amynthas agrestis (Goto and Hatai, 1899) has recently been documented invading forests of the Appalachian Mountains in the southeastern United States. This epigeic earthworm decreases the depth of organic soil horizons, and this may play a role in the decrease of millipede richness and abundance associated with A. agrestis invasion. To investigate the mechanisms behind these effects, A. agrestis and the millipede Sigmoria ainsliei (Xystodesmidae) were placed into microcosms with soil and either L horizon, F and H horizon, or a combination L/FH treatment....

Since adoption of the Northwest Forest Plan (NWFP) in the early 1990s, there has been a fundamental shift in forest management practices on federal lands in western Oregon and Washington. Commodity driven clearcut regeneration harvests have given way to thinnings intended to enhance development of late-successional forest habitats and to conserve important aquatic and riparian ecosystems. Density Management in the 21st Century: West Side Story presents abstracts and peer reviewed papers from a regional conference highlighting more than twenty years of research related to forest thinning in...

Pest risk maps are important decision support tools when devising strategies to minimize introductions of invasive organisms and mitigate their impacts. When possible management responses to an invader include costly or socially sensitive activities, decision-makers tend to follow a more certain (i.e., risk-averse) course of action. We presented a new mapping technique that assesses pest invasion risk from the perspective of a risk-averse decision maker. We demonstrated the method by evaluating the likelihood that an invasive forest pest will be transported to one of the U.S. states or...

Most modes of human-mediated dispersal of invasive species are directional and vector-based. Classical spatial spread models usually depend on probabilistic dispersal kernels that emphasize distance over direction and have limited ability to depict rare but influential long-distance dispersal events. These aspects are problematic if such models are used to estimate invasion risk. Alternatively, a geographic network model may be better at estimating the typically low likelihoods associated with human-mediated dispersal events, but it should also provide a reasonable account of uncertainties...