Aspen is considered a keystone species, and aspen communities are critical for maintaining biodiversity in western landscapes. Inventories of aspen stand health across the Eagle Lake Ranger District (ELRD), Lassen National Forest, California, U.S.A., indicate that 77% of stands are in decline and at risk of loss as defined by almost complete loss of mature aspen with little or no regeneration. This decline is due to competition from conifers establishing within aspen stands as a result of modification of natural fire regimes coupled with excessive browsing by livestock. Restoration treatments were implemented in four aspen stands in 1999 using mechanical equipment to remove competing conifers to enhance the growth environment for aspen. Recruitment and establishment of aspen stems were measured in treated stands (removal of competing conifers) and non-treated stands (control) immediately prior to treatment and 2 and 4 years post-treatment. There was a significant increase in total aspen stem density and in two of three aspen regeneration size classes for treated stands compared to controls. Pre-treatment total aspen density was positively associated with total aspen density and density in all size classes of aspen (p < 0.001). The results demonstrate that mechanical removal of conifers is an effective treatment for restoring aspen.
[1] Applying a trading ratio system similar to that proposed by Hung and Shaw (2005), we estimate the potential cost savings of a phosphorus emissions trading program that meets overall total maximum daily load allocations among 22 wastewater treatment plants (WWTPs) in the Passaic River watershed (United States) to be a modest 2-3% relative to a no-trade baseline. These results may be typical of those in relatively small watersheds such as the Passaic, where there are limited numbers of potential traders and relatively homogeneous abatement technologies across WWTPs. More substantial gains from trade may accrue to a concentrated group of WWTPs, suggesting that watershed managers should focus on a targeted set of traders within a watershed. Under certain conditions, additional gains may be achieved by aggregating WWTPs into zones within which there can be one-to-one allowance trading. Background and Objectives[2] Water quality trading has been met with mixed success in the United States. Despite the theoretical promise of water quality markets, substantial financial and technological support by the United States Environmental Protection Agency (EPA), and more than 70 established and pilot programs, ''only 100 facilities have participated in trading'' [EPA, 2008] (E-S 1). Moreover, 80 of these 100 trades have occurred in a single market, the Long Island Sound Nitrogen Credit Exchange program, which operates more like an exceedence tax abatement subsidy than a market with endogenously determined prices. For the more ''typical'' watershed trading programs without such a generous credit exchange to absorb imbalances between supply and demand, reallocation of abatement levels across firms through the buying and selling of pollution allowances or credits has been much more limited (see King and Kuch [2003], Breetz et al. [2004], and EPA [2008] for discussions). Thus the extent of cost savings in a ''typical'' total maximum daily load (TMDL)-governed watershed associated with market trading remains an open, empirical question.[3] In this paper, the nontidal Passaic River watershed in the state of New Jersey is used as a case study to investigate the size of potential cost savings associated with allowing phosphorus emissions trading among wastewater treatment plants (WWTPs) to achieve a significant reduction in ambient phosphorus levels. On 24 April 2008, a final TMDL rule was promulgated, calling for a more than 80% reduction in the total phosphorus concentration emissions from 22 WWTPs in the watershed. It is estimated that the average (flow weighted) total phosphorus emissions are 2.13 mg/l (402,000 lbs (1 lb = 0.4536 kg)). The TMDL document calls for a long-term average year-round effluent concentration of 0.40 mg/l of total phosphorus, equivalent to 75,650 lbs of phosphorus at existing flow.[4] To measure cost savings, we specify a trading-ratio system similar to one proposed by Hung and Shaw [2005] that minimizes the abatement cost of meeting environmental standards throughout the watershed. Under trading, e...
Watershed groups, individuals, and land management and regulatory agencies are collecting streamtemperature data in order to understand, protect and enhance cold-water fisheries. While great quantities of data are being generated, its analysis and interpretation are often not adequate to identify stream reaches that are gaining or losing temperature, or to correlate temperature changes with factors such as vegetative canopy cover or stream-flow levels. We use a case study from the Lassen and Willow creek watersheds in northeastern Modoc County to demonstrate graphical methods for displaying, analyzing and interpreting stream-temperature data.
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