Thirty years of gap dynamics in a central european beech forest reserve

Investigation of gap characteristics and tree regeneration patternsis central for our understanding of forest dynamics. By integratingaerial photograph analyses and ground surveys, we provide astudy of long-term canopy gap dynamics and tree regenerationpatterns in a Hungarian beech forest reserve. We found (1) thatin spite of the overall increase of gap area during the investigated30-years (from 2.5 to 7.7 per cent), total gap area and averagegap size (40–93 m²) were remarkably similar to those foundin other temperate and tropical forests, (2) if the fate ofindividual gaps was followed, two to three times more intensivecanopy dynamics (gap creation, closure and expansion) couldbe recognized than simple change of gap area indicated, and(3) average seedling density was considered to be sufficientfor natural regeneration. However, it was apparent that recentincreased deer browsing had prevented establishment of youngertrees of 1–2 m in height, as taller saplings were recordedonly in old gaps. Our results not only provide useful informationon forest dynamics but can also contribute to understandingthe potential roles that small forest reserves can play in providingessential reference data for nature-based forest managementof this forest type.     

Screening and Evaluation of Alum and Polymer Combinations as Coagulation/Flocculation Aids to Treat Effluents from Intensive Aquaculture Systems

As the application of intensive aquaculture systems continues to grow worldwide, so does the need for environmentally sound waste management and waste disposal techniques. The use of coagulants and flocculants to assist in removing suspended solids has long been a standard in the waste treatment field. Recently, The Conservation Funds Freshwater Institute has continued its research into coagulation/flocculation aids by examining the performance of alum coupled with various commercially available polymers. Alum is efficient in sequestering phosphorus through chemical precipitation and coagulation of fine solids through charge neutralization. Synthetic polymers are efficient in flocculating small particles together but do not efficiently remove dissolved phosphorus. The specific intention of this work was to use the qualities that distinguish both the alum and the polymer individually and combine the two to optimize wastewater treatment for the removal of both suspended solids and phosphorus. The alum/polymer combinations were first screened to determine which polymers worked best with our waste and with the alum. Once the screening was completed, the six best performing combinations were further evaluated with triplicate tests in a jar test apparatus to determine a standard optimal dosage based on phosphorus and suspended solids removal. Using a combination of alum/polymer, the effluent total suspended solids (TSS) removal rate was close to 99%, with final TSS values ranging from 4 to 20 mg/L. Reactive phosphorus was reduced by 92 to 99% to as low as 0.16 mg/L‐P. Finally, total phosphorus was also significantly reduced (98%), with treated effluent concentrations from 0.9 to 3.0 mg/L‐P. Although not intended for nitrogen removal, total ammonia‐nitrogen (TAN), nitrite‐nitrogen, nitrate‐nitrogen, and total nitrogen in the effluent were reduced on average by 64, 50, 68, and 87%, respectively. Removal rates for both 5 d carbonaceous biochemical oxygen demand (CBOD₅) and chemical oxygen demand (COD) were also significant, with an average value of 97.3 and 96.4%.     

Screening and evaluation of polymers as flocculation aids for the treatment of aquacultural effluents

As environmental regulations become more stringent, environmentally sound waste management and disposal are becoming increasingly more important in all aquaculture operations. One of the primary water quality parameters of concern is the suspended solids concentration in the discharged effluent. For example, EPA initially considered the establishment of numerical limitations for only one single pollutant: total suspended solids (TSS). For recirculation systems, the proposed TSS limitations would have applied to solids polishing or secondary solids removal technology. The new rules and regulations from EPA (August 23, 2004) require only qualitative TSS limits, in the form of solids control best management practices (BMP), allowing individual regional and site specific conditions to be addressed by existing state or regional programs through NPDES permits. In recirculation systems, microscreen filters are commonly used to remove the suspended solids from the process water. Further concentration of suspended solids from the backwash water of the microscreen filter could significantly reduce quantity of discharge water. And in some cases, the backwash water from microscreen filters needs to be further concentrated to minimize storage volume during over wintering for land disposal or other final disposal options. In addition, this may be required to meet local, state, and regional discharge water quality. The objective of this research was an initial screening of several commercially available polymers routinely used as coagulation–flocculation aids in the drinking and wastewater treatment industry and determination of their effectiveness for the treatment of aquaculture wastewater. Based on the results of the initial screening, a further evaluation of six polymers was conducted to estimate the optimum polymer dosage for flocculation of aquaculture microscreen effluent and overall solids removal efficiency. Results of these evaluations show TSS removal was close to 99% via settling, with final TSS values ranging from as low as 10–17 mg/L. Although not intended to be used for reactive phosphorus (RP) removal, RP was reduced by 92–95% by removing most of the TSS in the wastewater to approximately 1 mg/L–P. Dosage requirements were fairly uniform, requiring between 15 and 20 mg/L of polymer. Using these dosages, estimated costs range from $4.38 to $13.08 per metric tonne of feed.