EVALUATING INCENTIVE PAYMENT PROGRAMS THROUGH AGGREGATE PRODUCTION RESPONSE: THE CASE OF MOHAIR

Production Economics,

The Problem of Planting Louisiana Swamplands when Nutria (Myocastor Coypu) are Present

Logging of baldcypress (Taxodium distichum) in the swamps of the southeastern United States is once again becoming common and an area of particular concern in Louisiana is the regeneration of cypress in its natural environment. One way to ensure the proper stocking of cypress is to plant seedlings, but nutria usually damage or destroy newly planted seedlings and are a deterrent to cypress regeneration in flooded areas. In 1985 cypress seedlings were planted in a flooded logged area and in an area where flooding was preventing the establishment of natural seedlings. Nutria destroyed 86% of the seedlings in the Barataria watershed (logged area) and 100% in the Lake Verret watershed. One-half of the Barataria seedlings were protected with Vexar seedling protectors, but these were no deterrent to nutria. A second planting was made in the Lake Verret basin and the seedlings surrounded by chicken wire fencing. Nutria did no damage to the protected seedlings. A third planting was made in the Lake Verret area in September 1985 to determine if nutria would destroy late planted seedlings. Once again no nutria damage was observed. Implications are that spring-planted seedlings need protection to allow them to establish a root system making them more difficult for the nutria to pull up. Fall-planted seedlings appear to be less susceptible to damage because of the abundant food supply provided by aquatic plants that grow during the summer and fall. Once firmly established, cypress seedlings are less susceptible to nutria damage

Vexar Seedling Protectors did not Reduce Nutria Damage to Planted Baldcypress Seedlings

Vexar seedling protectors were tested for preventing nutria damage to baldcypress (Taxodium distichum (L.) Rich) seedlings planted in Louisianaswamp forests. Five areas were planted with 1-year-old baldcypress seedlings. Half the seedlings in each area were protected with Vexar seedling protectors. The protectors slowed down the rate of destruction in some areas, but after 3 months, 85% of the guarded seedlings and 87% of the unguarded seedlings were destroyed

Correlation between fracture surface morphology and toughness in Zr-based bulk metallic glasses

Fracture surfaces of Zr-based bulk metallic glasses of various compositions tested in the as-cast and annealed conditions were analyzed using scanning electron microscopy. The tougher samples have shown highly jagged patterns at the beginning stage of crack propagation, and the length and roughness of this jagged pattern correlate well with the measured fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, are attributed to the formation of shear bands inside the sample. This observation provides strong evidence of significant “plastic zone” screening at the crack tip

Bottomland Hardwood Management Demonstrations for South Carolina\u27s Lowcountry Forest Conservation Project

Southern bottomland hardwood forests occur on river floodplains of the southeastern United States, and ecological processes are driven by seasonal floodwaters from the river. Conservation and management of southeastern US coastal plain ecosystems is a priority in South Carolina’s Lowcountry Forest Conservation Project. The project is a partnership of Clemson University, Ducks Unlimited, the Joseph W. Jones Ecological Research Center, Lowcountry Open Land Trust, South Carolina Coastal Conservation League, The Conservation Fund, and The Nature Conservancy. A goal of this project is to create and disseminate economically and ecologically viable methods for conservation-based bottomland hardwood management on private lands, including restoration of degraded forests. Southern bottomland forests have been extensively altered by past cutting practices, as well as past agricultural use, indiscriminate cattle grazing, uncontrolled fires, and lack of attention to regeneration. Early harvest practices included high-grading to remove the most valuable stems, leaving behind the poorest. Repeating this practice through the years has resulted in under-stocked stands of low-quality trees in many forests. Four sites have been selected to establish demonstration areas to show people different management techniques that are currently being used to enhance timber and wildlife values. Funding for the project is provided by the Doris Duke Charitable Foundation. One model of bottomland hardwood management that can be used to achieve conservation goals in the southeastern United States is the system currently practiced by the Anderson-Tully Corporation in bottomland forests of the Mississippi River. The adaptation of this management method is presented here

Siviculture and Management Strategies Applicable to Southern Hardwoods

Southern hardwood forests stretch from the Virginias to Florida and from the mid-Atlantic to Missouri. They can generally be grouped into upland forests and bottomland forests. The upland hardwood forests of the southern region are usually associated with the mountainous topography of the Appalachians and Ozarks. Bottomland hardwoods are found along the floodplains of larger rivers in the Atlantic and Gulf Coastal Plains, including the Mississippi River floodplain. Southern hardwood forests are owned by a variety of governmental and private owners, but the vast majority of owners are nonindustrial private individuals. These owners seldom engage in intensive forest management, often exploiting the resource. The silvicultural systems applicable to the management of hardwoods are the same as those recommended for pines, but in hardwood management, reliance on natural regeneration is more common than use of plantation silviculture. Oak species are very important in the southern hardwood forests, and lack of oak regeneration in present-day forests is a major concern. Lack of fire and the resurgence of white-tailed deer throughout the southern region are proposed as reasons for poor oak regeneration. Many stands, either due to their stage of development or neglect, are in need of intermediate management operations such as thinning and improvement cutting. Crop-tree management is a method that is particularly useful in southern hardwoods. It was concluded that although hardwoods make up a significant part of the southern forest resource, they are generally managed with less intensity than pines, and hardwood management is an opportunity area for the South in the future

How Do Tiger Moths Jam Bat Sonar?

The tiger moth Bertholdia trigona is the only animal in nature known to defend itself by jamming the sonar of its predators – bats. In this study we analyzed the three-dimensional flight paths and echolocation behavior of big brown bats (Eptesicus fuscus) attacking B. trigona in a flight room over seven consecutive nights to determine the acoustic mechanism of the sonar-jamming defense. Three mechanisms have been proposed: (1) the phantom echo hypothesis, which states that bats misinterpret moth clicks as echoes; (2) the ranging interference hypothesis, which states that moth clicks degrade the bats\u27 precision in determining target distance; and (3) the masking hypothesis, which states that moth clicks mask the moth echoes entirely, making the moth temporarily invisible. On nights one and two of the experiment, the bats appeared startled by the clicks; however, on nights three through seven, the bats frequently missed their prey by a distance predicted by the ranging interference hypothesis (∼15–20 cm). Three-dimensional simulations show that bats did not avoid phantom targets, and the bats\u27 ability to track clicking prey contradicts the predictions of the masking hypothesis. The moth clicks also forced the bats to reverse their stereotyped pattern of echolocation emissions during attack, even while bats continued pursuit of the moths. This likely further hinders the bats\u27 ability to track prey. These results have implications for the evolution of sonar jamming in tiger moths, and we suggest evolutionary pathways by which sonar jamming may have evolved from other tiger moth defense mechanisms

Processes Contributing to Resilience of Coastal Wetlands to Sea-Level Rise

The objectives of this study were to identify processes that contribute to resilience of coastal wetlands subject to rising sea levels and to determine whether the relative contribution of these processes varies across different wetland community types. We assessed the resilience of wetlands to sea-level rise along a transitional gradient from tidal freshwater forested wetland (TFFW) to marsh by measuring processes controlling wetland elevation. We found that, over 5 years of measurement, TFFWs were resilient, although some marginally, and oligohaline marshes exhibited robust resilience to sea-level rise. We identified fundamental differences in how resilience is maintained across wetland community types, which have important implications for management activities that aim to restore or conserve resilient systems. We showed that the relative importance of surface and subsurface processes in controlling wetland surface elevation change differed between TFFWs and oligohaline marshes. The marshes had significantly higher rates of surface accretion than the TFFWs, and in the marshes, surface accretion was the primary contributor to elevation change. In contrast, elevation change in TFFWs was more heavily influenced by subsurface processes, such as root zone expansion or compaction, which played an important role in determining resilience of TFFWs to rising sea level. When root zone contributions were removed statistically from comparisons between relative sea-level rise and surface elevation change, sites that previously had elevation rate deficits showed a surplus. Therefore, assessments of wetland resilience that do not include subsurface processes will likely misjudge vulnerability to sea-level rise

Processes Contributing to Resilience of Coastal Wetlands to Sea-Level Rise

The objectives of this study were to identify processes that contribute to resilience of coastal wetlands subject to rising sea levels and to determine whether the relative contribution of these processes varies across different wetland community types. We assessed the resilience of wetlands to sea-level rise along a transitional gradient from tidal freshwater forested wetland (TFFW) to marsh by measuring processes controlling wetland elevation. We found that, over 5 years of measurement, TFFWs were resilient, although some marginally, and oligohaline marshes exhibited robust resilience to sea-level rise. We identified fundamental differences in how resilience is maintained across wetland community types, which have important implications for management activities that aim to restore or conserve resilient systems. We showed that the relative importance of surface and subsurface processes in controlling wetland surface elevation change differed between TFFWs and oligohaline marshes. The marshes had significantly higher rates of surface accretion than the TFFWs, and in the marshes, surface accretion was the primary contributor to elevation change. In contrast, elevation change in TFFWs was more heavily influenced by subsurface processes, such as root zone expansion or compaction, which played an important role in determining resilience of TFFWs to rising sea level. When root zone contributions were removed statistically from comparisons between relative sea-level rise and surface elevation change, sites that previously had elevation rate deficits showed a surplus. Therefore, assessments of wetland resilience that do not include subsurface processes will likely misjudge vulnerability to sea-level rise

Can screening for genetic markers improve peripheral artery bypass patency?

AbstractObjective: Three genetic mutations have been associated with an increased risk of thromboembolic events: factor V Leiden R506Q, prothrombin G20210A, and methylenetetrahydrofolate reductase C677T (MTHFR) mutations. The aim of this study was to determine the effect of these mutations on patency of peripheral bypass procedures and preoperative and postoperative thromboembolic events. Methods: Two hundred forty-four randomly selected volunteers participating in the Veterans Affairs Cooperative Study #362 were tested for factor V Leiden, prothrombin, or MTHFR mutations with polymerase chain reaction. Patients enrolled in the study were randomized to receive aspirin therapy or aspirin and warfarin therapy after a peripheral bypass procedure. The frequencies of preoperative and postoperative thromboembolic events and primary patency (PP), assisted primary patency (APP), and secondary patency (SP) rates were compared among carriers of the various mutations. Results: Fourteen patients (5.7%) were heterozygous for the factor V Leiden mutation, seven (2.9%) were heterozygous for the prothrombin mutation, and 108 (44.6%) were heterozygous and 15 (6.2%) homozygous for the MTHFR mutation. After surgery, patients homozygous for the MTHFR gene mutation had increased graft thrombosis, compared with patients who were heterozygous (33.3% versus 11.1%; P = .01), and lower PP, APP and SP rates (P < .05). Furthermore, patients heterozygous for the MTHFR mutation had fewer graft thromboses (11.1% versus 24.4%; P = .01), fewer below-knee amputations (0.9% versus 7.6%; P = .02), and higher PP, APP, and SP rates (PP, 79.6%; APP, 88.9%; SP, 90.7%; P < .05) compared with wild-type control subjects (PP, 63%; APP, 75.6%; SP, 76.5%; P < .05). Conclusion: Patients with either factor V Leiden or prothrombin mutations were not at an increased risk for postoperative graft occlusion or thromboembolic events. Patients heterozygous for MTHFR mutation had a lower risk of graft thrombosis and higher graft patency rates compared with both homozygous and wild-type control subjects. Patients homozygous for the MTHFR mutation had lower graft patency rates compared with patients who were heterozygous, and a trend was seen toward lower patency rates compared with wild-type control subjects. Therefore, screening for the MTHFR gene mutation before surgery may identify patients at an increased risk of graft thrombosis. (J Vasc Surg 2002;36:1198-206.