Search

At two affiliate sites of the North American Long-Term Soil Productivity Study (Matlock, WA and Molalla, OR, USA), soil chemical properties and stand characteristics of planted coast Douglas-fir (Pseudotsuga menziesii var. menziesii) were compared 15 years after forest harvesting and application of three logging-debris configurations (dispersed, piled, or removed) combined with either initial vegetation control (IVC; year 0) or annual vegetation control (AVC; years 0 to 5). At Matlock, soil carbon (C) and nitrogen (N) concentrations each were 17% greater after IVC than after AVC; at Molalla, soil N was 13% greater where debris was removed than where it was dispersed. At Matlock, cover of nonnative Scotch broom (Cytisus scoparius) after IVC was greater where debris was removed (61%) than where it was piled (27%) or dispersed (7%), despite a control treatment in year 4. Conversely, covers of the native shrubs, trailing blackberry (Rubus ursinus) and salal (Gaultheria shallon) were 20% to 30% greater where debris was dispersed than where it was piled or removed. With AVC versus IVC, Douglas-fir stand volume was 34% to 159% greater at Matlock depending on the logging-debris treatment, and it was 30% greater at Molalla independent of debris treatments. However, Douglas-fir survival and growth after AVC did not differ among logging-debris treatments at either site. Survival of Douglas-fir growing 1 m from debris piles. Debris dispersal or piling at Matlock strongly mitigated Scotch broom impacts to forest productivity compared to debris removal. Our findings demonstrate how disturbance characteristics associated with forest harvesting and regeneration practices can influence vegetation recruitment and competitive relationships to place limits on longer-term forest productivity. USDA National Institute for Food and Agriculture [GRANT11325729]; USDA Forest Service, Pacific Northwest Research StationUnited States Department of Agriculture (USDA)United States Forest Service; Port Blakely Tree Farms LLC; Green Diamond Resource Company Financial support for this research was provided by the USDA National Institute for Food and Agriculture (Grants.gov number: GRANT11325729) and the USDA Forest Service, Pacific Northwest Research Station. The authors are especially grateful to Randall Greggs, Green Diamond Resource Company, and Mike Warjone, Port Blakely Tree Farms LLC, for providing critical logistical and financial support that made this study possible. Thanks also to the helpful comments from the Associate Editor, two anonymous reviewers, and Kim Littke, University of Washington. Public domain – authored by a U.S. government employee

Coal mining in central Appalachia USA causes increased specific conductance in receiving streams. Researchers have examined benthic macroinvertebrate community structure in such streams using temporally discrete measurements of SC and benthic macroinvertebrates; however, both SC and benthic macroinvertebrate communities exhibit intra-annual variation. Twelve central Appalachian headwater streams with reference quality physical habitat and physicochemical conditions (except for elevated SC in eight streams) were sampled ≤fourteen times each between June 2011 and November 2012 to evaluate benthic macroinvertebrate community structure. Specific conductance was recorded at each sampling event and by in situ data loggers. Streams were classified by mean SC Level (Reference, 17–142 μS/cm; Medium, 262–648 μS/cm; and High, 756–1535 μS/cm). Benthic macroinvertebrate community structure was quantified using fifteen metrics selected to characterize community composition and presence of taxa from orders Ephemeroptera, Plecoptera, and Trichoptera. Metrics were analyzed for differences among SC Levels and months of sampling. Reference streams differed significantly from Medium-SC and High-SC streams for 11 metrics. Medium-SC streams had the most metrics exhibiting significant differences among months. Relative abundances of Plecoptera and Trichoptera were not sensitive to SC, as the families Leuctridae and Hydropsychidae exhibited increased relative abundance (vs. reference) in streams with elevated SC. In contrast, Ephemeroptera richness and relative abundance were lower, relative to reference, in elevated-SC streams despite increased relative abundance of Baetidae. Temporal variability was evident in several metrics due to influence by taxa with seasonal life cycles. These results demonstrate that benthic macroinvertebrate communities in elevated-SC streams are altered from reference condition, and that metrics differ in SC sensitivity. The time of year when samples are taken influenced measured levels and differences from reference condition for most metrics.

Expansion of ethanol production has led to regional-scale cultivation of cellulosic biofuel crops, such as switchgrass ( Panicum virgatum L.), on agriculturally marginal lands. A range of forest-based solutions are also being evaluated, especially in the southeastern U.S. However, there may be unanticipated environmental consequences, including changes in water export when managing forests to accommodate biofuel demands at a regional scale. We used the Soil Water Assessment Tool (SWAT) to simulate effects of regional-scale conversion of loblolly pine ( Pinus taeda L.) plantations to switchgrass biofuel production on stream flow in the ∼5 million ha Tombigbee River Watershed in the southeastern U.S. Greater than 50% of the Tombigbee Watershed is forested, with 20% of the watershed supporting primarily loblolly pine forests. We modified the SWAT model by adding five age classes of loblolly pine trees, to more accurately represent existing forested systems. We found that maximum conversion of loblolly pine to switchgrass, affecting 7% of the watershed, represented an extreme land-use change and resulted in a 4% increase in annual stream flow. The more operationally and economically feasible option of converting young (≤4 yrs) and old (≥16 yrs) loblolly pine stands to switchgrass on

The Valdivian rainforest ecoregion in Chile (35°–48°S) has a high conservation priority worldwide. These forests are also keys for social welfare as a result of their supply of timber as well as ecosystem services. Forests in the ecoregion have been extensively converted to fast growing Pinus radiata and Eucalyptus spp. plantations for timber production promoted by public policies and timber companies. This study describes the results of detailed measurements of hydrology and stream water chemistry in eight small watersheds in south central Chile, subjected to replacement of native temperate rainforest by exotic Eucalyptus plantations. In this system, watersheds have streamside buffers of native forest (SNFW) with varying widths. Results indicate that retention of SNFW counteracts hydrologic effects of Eucalyptus plantations, which are widely known to reduce water yields. A 1.4% rate of increase of the run-off coefficient for each metre of increase of SNFW was observed. In addition, a decrease in the concentrations of total nitrogen, dissolved inorganic nitrogen (DIN), nitrate-N, and different sized fractions of particulate organic matter were found in streams draining these plantations as a function of increasing SNFW. Streamside buffer widths of 17–22 m for total nitrogen and DIN concentrations and ≥36 m for sediments were required to provide comparable values to reference watersheds (100% native forest). The findings from this study suggest that SNFW may significantly reduce adverse effects from exotic species forestry plantations on water provision in an area of south central Chile where exotic forest plantations are rapidly expanding. Copyright © 2014 John Wiley & Sons, Ltd.

Elevated specific conductance (SC) in freshwater streams has been associated with alterations of benthic macroinvertebrate communities. Responses by dominant taxa to high salinity in streams can potentially complicate bioassessments. Taxonomic replacement is a method that can detect changes of community identities along an SC gradient as a supplement to conventional metrics that consider taxa richness or abundance. We assessed structural differences among benthic macroinvertebrate communities along an SC gradient in headwater streams influenced by coal mining in the central Appalachian coalfield. Benthic macroinvertebrate communities were sampled quantitatively in 15 southwestern Virginia streams up to six times over the course of a year. Sampled macroinvertebrates were identified to genus when possible and enumerated quantitatively, enabling determination of total-sample density and richness for various taxonomic and functional groups as assemblage structural response metrics. Multivariate methods were used to examine dissimilarities of taxonomic structure among samples along the SC gradient, and Spearman correlations were used to determine associations between SC and group response metrics for each sampling month. Dissimilarity analyses revealed distinct separations of assemblage structure between 1) spring and fall sampling months, and 2) low-SC and high-SC streams. Ephemeroptera richness and density declined with increasing SC, supporting findings by prior studies. Certain tolerant taxa were present at high densities seasonally, masking responses of other taxa within taxonomic and functional groups of which they were members. Leuctra, an SC-tolerant Plecoptera genus, increased in density with increasing SC, and comprised up to 85% of sample densities seasonally in high-SC streams. Richness displayed a strong negative response to SC regardless of season and was a robust indicator of salinity effects. Some functional feeding groups (including collector-gatherers and scrapers) showed seasonal declines in density and/or richness with increasing SC. Taxonomic replacement along an SC gradient was evident in several taxonomic and functional feeding groups during months when richness and density did not exhibit an SC response. Season and SC exerted strong influence over macroinvertebrate community structure in quantitative samples from mining-influenced headwater streams. Taxonomic and functional group composition metrics that do not consider taxonomic identity may not reflect clearly community structure alterations caused by responses of dominant taxa within those groups.

Logging debris remaining after timber harvest can modify the microclimate and growing conditions for forest regeneration. Debris also can influence tree seedlings indirectly through its effects on development of competing vegetation, although the mechanisms are poorly understood. At two sites in Washington and Oregon (USA) that differed in availability of soil water and nutrients, mechanisms were studied by which logging debris and competing vegetation interacted to influence performance of planted Douglas-fir ( Pseudotsuga menziesii (Mirb.) Franco var. menziesii ) seedlings. In a split-plot design, two levels of competing vegetation (presence and absence) and three covers of logging debris (0%, 40%, and 80%) were replicated eight times at each site on 2 × 2-m areas centered on individual Douglas-fir seedlings. Vegetation abundance, seedling growth, and resource availability were monitored for 4 years (2005–2008). Soil water depletion was lower and Douglas-fir water potential and foliar nitrogen were higher in the absence of competing vegetation, resulting in increased seedling growth. The highest seedling growth rates and foliar nitrogen contents occurred where absence of vegetation was combined with 80% debris cover. Where competing vegetation was present, 40% debris cover was associated with decreases in herb cover and soil water depletion and increases in seedling growth relative to 0% or 80% debris covers. At the Washington site where soil quality was lower, the combination of presence of vegetation and 80% debris cover was associated with a 2.4 °C average reduction in summer soil temperatures at 15 cm depth, reduced foliar nitrogen content, and the slowest rates of seedling growth. Potential effects of logging debris, such as mulching (i.e., reduced evaporation of soil water) and interception loss (i.e., reduced precipitation inputs), were minor to non-detectable from sensors buried at 20–40 cm soil depth. Results of the research suggest that retention of moderate levels of logging debris (i.e., 40% cover) after forest harvesting in the Pacific Northwest is likely to increase early growth of Douglas-fir by increasing soil water availability through reduced herb abundance. Where intensive vegetation control is practiced, retention of higher debris levels (i.e., 80% cover) may provide further benefits to seedling growth.

Despite widespread use of intensive vegetation control (VC) in forest management, the effects of VC on allocation of biomass and nutrients between young trees and competing vegetation are not well understood. On three Pacific Northwest sites differing in productivity, soil parent material, and understory vegetation community, we evaluated year-5 effects of presence/absence of 5 years of VC on allocation of aboveground biomass and nitrogen (N) between planted Douglas-fir (Pseudotsuga menziesii var. menziesii) and competing vegetation. Equations for predicting bole, branch, foliar, and total dry weights based on stem diameter at a height of 15 cm and total tree height did not differ significantly among sites or by presence or absence of VC. This contrasts with previous research, using diameter at breast height rather than at 15 cm, which found that separate equations were warranted for trees with and without competing vegetation. Estimated whole-tree biomass among the six site/VC combinations ranged from 0.8 to 7.5 Mg ha � 1

We compared stream ecosystem responses to two types of disturbances: flood and debris flows. A large storm in February 1996 disturbed four similarly sized sub-watersheds of the Calapooia River, in the Cascade Mountains of Oregon, USA. All sub-watersheds had flood and in two, 31 and 81% of the perennial channel, a debris flow affected the channel. For 8 years, we used a suite of approaches: stream temperature, nutrient regime, periphyton and macroinvertebrate assemblages, and resident trout abundance and habitat to evaluate the persistence of instream impacts. Differences in stream temperatures and nitrate-nitrogen concentrations were evident, probably, due to the removal of vegetation and modification of riparian soils at the debris flow sites. Instream biological responses varied. After the event, fish, including trout, were rare with no fish at the debris flow sites. Within 6 years, trout densities (Oncorhynchus mykiss and Oncorhynchus clarki) were similar and young-of-the-year trouts were common. In contrast, periphyton and macroinvertebrate assemblages differed. Periphyton biomass was lower and nitrogen-fixing periphyton was more abundant at the debris flow sites. Macroinvertebrate assemblage diversity was higher at the debris flow sites due to fewer dominant taxa. Macroinvertebrate functional feeding groups also differed with fewer gatherers and more scrapers at the debris flow sites. Debris flow impacts related to loss of riparian canopy will probably persist until mature red alder stands are re-established along stream-reaches affected by debris flows to provide nitrogen input and shade. Copyright © 2011 John Wiley & Sons, Ltd.

Belowground C and N storage is important in maintaining forest productivity and to CO 2 sequestration. How these pools respond to management is poorly understood. We investigated effects of repeated applications of complete fertilizer and competing vegetation control with herbicides on C and N storage in forest-floor, fine-root, and mineral-soil C and N pools to 1-m depth at three Pinus ponderosa P. Lawson & C. Lawson var. ponderosa plantations across a site quality gradient in northern California. Belowground C pools without treatment were 66, 153, and 199 Mg C ha -1 for the low-, intermediate-, and high-quality sites, respectively, and N pools were 5.1, 6.7, and 6.5 Mg N ha -1 , respectively. Treatments increased tree-bole volume at 20 yr as much as 400%, while changes in C and N pools belowground were less dramatic. Herbicide treatment increased forest-floor C pools 35% at the poorer quality site. Fertilization increased forest-floor C and N storage 46 to 106% at all sites. Fertilization decreased fine-root C pools at 0 to 0.3 m at the most productive site 43% and increased this N pool 43% at the least productive site, but did not influence fine-root pools to 1 m. Fertilization increased mineral-soil C pools on lower quality sites, resulting in 12 to 57% more belowground C storage. At the intermediate site, fertilization increased total belowground N storage 12%. Results of this study suggest that the major sequestration mechanism up to this point in stand development is through gains in tree biomass rather than storage in fine roots and soil belowground.

As erosion control and water conservation are almost always important issues, information on water use between different plantation species may be of significant management value for guiding decisions on species selection. The main and interactive effects of species and fertilisation on annual water loss and drainage in three-year old Cupressus lusitanica Mill. and Pinus radiata D. Don were examined across an environmental gradient at eight sites in New Zealand using small highly stocked plots designed to compress the rotation length. Annual average fractional available volumetric water content (θa), total annual water loss and total annual drainage for each treatment at each of the eight sites was determined using a daily water balance model, validated against two-monthly measurements of θa. Modelled annual average θa, total annual water loss and total annual drainage were all significantly influenced by site and species (P 0.05 for all variables). Averaged across the eight sites, annual average θa for C. lusitanica was higher than that of P. radiata by 0.15 (0.58 vs. 0.43). Total annual water loss for P. radiata was on average 104 mm higher, than that of C. lusitanica (893 mm vs. 789 mm), while total annual drainage for C. lusitanica was on average 129 mm higher than that of P. radiata (285 mm vs. 156 mm). Combining average values for drainage and water loss indicated that there was on average 233 mm more available water per annum in soils under C. lusitanica than P. radiata, which equated to an average of 22% of total annual rainfall.

Little is known about the spatial and temporal dynamics of abundance and habitat use of the goldstripe darter (Etheostoma parvipinne). We assessed population dynamics, species associates and habitat use of this rarely studied darter in 14 first-order streams within pine plantations in north-central Mississippi. The pattern of goldstripe darter abundance among sampling periods differed among streams. Three streams with the greatest abundance of goldstripe darters exhibited significant differences in abundance among sampling periods, while the remaining 10 streams did not differ in abundance among sampling periods. Goldstripe darters exhibited the greatest associations with creek chub (Semotilus atromaculatus), brown madtom (Noturus phaeus) and least brook lamprey (Lampetra aepyptera). Goldstripe darter abundance was positively correlated with canopy cover, water temperature and sand. Our results suggest that management plans designed to maintain and develop forested riparian zones adjacent to first-order streams would assist with the conservation of goldstripe darters.

Effects of flooding on survival and growth of three different types of Nuttall oak (Quercus texana Buckl.) seedlings were observed at the end of third and fifth growing seasons at Yazoo National Wildlife Refuge, Mississippi, U.S.A. Three types of seedlings were planted in January 1995 in a split-plot design, with four replications at each of two elevations on floodprone, former cropland in Sharkey clay soil. The lower of the two planting elevations was inundated for 21 days during the first growing season, whereas the higher elevation did not flood during the 5-year period of this study. The three types of 1-0 seedlings were bareroot seedlings, seedlings grown in containers (3.8 3 21‐cm plastic seedling cones), and container-grown seedlings inoculated with vegetative mycelia of Pisolithus tinctorius (Pers.) Coker. Survival of all the three seedling types was greatest at the lower, intermittently flooded elevation, indicating that drought and related effects on plant competition were more limiting to seedling survival than flooding. At the lower elevation, survival of mycorrhizal-inoculated container seedlings was greater than that of noninoculated container seedlings. Survival among bareroot seedlings and inoculated container seedlings was not significantly different at either elevation. At the higher, nonflooded elevation, however, bareroot seedling survival was greater than the survival of container seedlings without inoculation. Differences were significant among the inoculated and the noninoculated container seedlings, with higher survival of inoculated seedlings at both elevations, though differences were only significant in year 3. At the end of the fifth year, height of bareroot seedlings was significantly greater than the heights of both types of container-grown seedlings at both planting elevations. Because seedlings grown in the plastic seedlings cones did not survive better than the bareroot seedlings at either planting elevation, the bareroot stock appear to be the economically superior choice for regeneration in Sharkey soil.

We sampled fishes and measured physical habitat in 14 first-order streams in north-central Mississippi to document fish community characteristics and examine the relationships between the fish communities and physical habitat charac- teristics. We documented 36 species and 11 families from 6943 captures. The five most abundant species were creek chub (Semotilus atromaculatus Mitchell), least brook lamprey (Lampetra aepyptera Abbot), blackspotted topminnow (Fundulus olivaceus Storer), creek chubsucker (Erimyzon oblongus Mitchell), and green sun- fish (Lepomis cyanellus Rafinesque). We also observed that most streams (> 50%) were numerically dominated by: 1) Cyprinidae, 2) fishes having a maximum body size between 300-399 mm TL, 3) insectivores, and 4) guarder-nest spawners. Fish species composition of our study streams was similar to the species composition documented in other medium- and low-gradient headwater streams in the Gulf Coastal Plain. Additionally, fish community structure in first-order streams was significantly correlated with channel cross-section area, woody debris, canopy cover, water depth, velocity, wet width, and substrate types. The observed relationships between fish communities and physical habitat characteristics in first-order stream were similar to fish-habitat relationships observed by previous investigators working in northern Mississippi streams ranging in size from first to fifth-order.

New Zealand law requires sustainable forest management. International definitions of sustainability typically include maintaining the productive capacity of forest soils, and decision tools are needed for managing harvesting and site preparation practices. Trials were established between 1986 and 1994 in different physiographic regions of New Zealand to determine the effects of management on the second-rotation performance of Pinus radiata. Main harvesting and residue treatments at three North Island sites include: whole-tree harvest plus forest floor removal, whole-tree harvest, and stem-only harvest retaining a single layer of slash. These treatments were installed in a random block split-plot design (with and without fertiliser). Additional treatments were added at specific sites (e.g., double slash addition at Woodhill; topsoil removal at Tarawera) to test hypotheses that harvesting intensity is negatively correlated with second-rotation growth, that inadequate nutrition is the reason for the negative correlation, and that fertiliser additions can compensate for the negative impact of harvesting on nutrition. Stands were thinned-to-waste to reduce stocking by 50% at Woodhill (age 7 years), Tarawera and Kinleith (age 5 years). On recent coastal sand dunes at Woodhill, foliar analyses suggest that nutrient availability to trees of N, P, K, B, Mn, and Zn were reduced during critical periods of stand establishment by forest floor removal, and improved by retention of thinning slash. Diameter at 5 years declined as forest floor C:N ratio increased. Diameter after 11 years was reduced by forest floor removal, and positively related with residue retention. On approximately 100-year-old basaltic tephra gravel at Tarawera, foliar concentrations of K and B were positively related with slash and soil nutrient retention, however, the effect of harvest removals on tree nutrition and growth was substantially less than observed on recent sand dunes due to greater native fertility of basaltic gravel. Forest floor C:N ratio at Tarawera explained less variation in tree growth than at Woodhill. On the N-rich Taupo sandy loam of Kinleith Forest, there was no correlation between forest floor C:N ratio and tree diameter to age 5 years. Fertiliser additions have increased tree diameter at all sites, and can ameliorate harvesting-related reductions in growth. However, fertiliser additions caused significant reductions in foliar concentrations of most nutrients studied except N. These trials have been useful for identifying the benefits of residue retention among sites with varying levels of native fertility. Based on the results of this study, we recommend organic matter retention during harvest and site preparation on N-deficient sites such as Pinaki Typic Sandy Recent Soil.

Three disturbance treatments were imposed on a palustrine forested wetland ( Nyssa aquatica-Taxodium distichum ) located in southwestern Alabama in 1986: (i) clearcutting with helicopter log removal (HELI), (ii) HELI followed by rubber-tired skidder traffic simulation (SKID) and (iii) HELI followed by removal of all vegetation during the first two growing seasons via glyphosate herbicide application (GLYPH). After two growing seasons, it was hypothesized that eventual woody plant growth would be best in the HELI-treated areas, because SKID plots had reduced rates of water movement and soil aeration. However, measurements at stand age seven years indicate that SKID actually has greater total above-ground biomass (65979 kg/ha) than HELI (46748 kg/ha) and SKID plots have a higher proportion of the most desirable timber species ( Nyssa aquatica ). GLYPH areas resemble freshwater marshes, although the areas are being invaded by Salix nigra seedlings. All disturbance treatments have significant groundflora components that have increased sediment accumulation 70–175% relative to an undisturbed reference area. By age seven years, regrowth of vegetation has lowered the water table during the growing season but has had little effect on soil redox potential and pH. Our observations suggest that this wetland system is rapidly recovering from logging disturbance seven years ago.

Conversion of cropland to short-rotation woody biomass crops (SRWC) has received increasing interest as biomass utilization technologies have improved and concerns for effects of fossil fuel emissions on global climate have developed. Effects of this conversion on erosion, hydrology, water quality and soil productivity may be significant. A large cooperative research project began in the spring of 1995 at three sites representative of the lower Tennessee Valley to compare the environmental effects of growing traditional row crops with the production of SRWCs over 3- to 5-year rotations. This paper presents the research approach be used to evaluate these effects and a few preliminary results from the initial 3 months of the study. Small watersheds cultivated in row crops: corn ( Zea mays L.) or cotton ( Gossypium hirsutum L.), are being compared with small watersheds in tree crops: sycamore ( Platanus occidentalis L.), sweetgum ( Liquidambar styraciflua L.) or eastern cottonwood ( Populus deltoides Bartr.) with respect to: (1) erosion; (2) run-off quality (nutrients, pesticides) and quantity; (3) groundwater quality; (4) soil chemical changes (carbon, nutrients, pesticides); (5) soil physical changes (infiltration, bulk density, aggregate stability); (6) soil biological changes; and (7) wildlife populations. During the spring and summer of the first growing season, few differences in run-off quantity and erosion were observed between treatments. One exception was a tendency towards higher erosion under cotton than cottonwood. Larger differences are expected in later years as trees become established and a litter layer develops. At two sites during the first growing season, differences between row crops and SRWCs were observed in both the runoff and leaching of NO 3 -N, NH 4 -N, P, Ca, Mg and K in spring following fertilization of the row crops only at these two sites. Wildlife studies on small mammals and bird populations, as well as microfauna, are just getting under way.

The effects of spoil type, slow-release fertilization, and weed control using glyphosate on the degree of ectomycorrhizal colonization of container-grown white (Pinus strobus L.), loblolly (P. taeda L.), and Virginia (P. virginiana Mill.) pines were studied on two strip-mined sites (sandstone vs. siltstone overburden material) in southwestern Virginia. Although some seedlings were successfully colonized at both sites, the number of seedlings colonized and the proportion of short-root colonization per seedling were consistently higher on the sandstone spoil. On both sites, loblolly and Virginia pines had more ectomycorrhizal formation than white pine. Foliar P levels of all three species on the sandstone spoil and of loblolly pine on the siltstone spoil were significantly correlated with ectomycorrhizal development. The degree of ectomycorrhizal formation for any of the species on either spoil was not decreased by slow-release fertilization or glyphosate applications. These results indicate that natural mycorrhizal colonization is compatible with these cultural treatments, and that colonization from indigenous fungal species may be adequate, eliminating the need for artificial inoculation.

Experiments were performed in 1977 to determine which large zooplankton in a series of high altitude ponds can be consumed by the predatory flatworm Mesostoma ehrenbergii. This predator consumes Daphnia at a high rate and the fairy shrimp Branchinecta at a low rate, but does not consume Diaptomus. Experiments were performed in 1978 and 1979 to determined the rate of predation on Daphnia in 30 liter tubs and to determine if predation rate is correlated with surface to volume ratio of experimental containers. There is a clear correlation between surface to volume ratio and predation rate. Determinations of Mesostoma and Daphnia densities were made in a series of eight high altitude ponds, and pond surface to volume ratios were determined. Examination of these parameters lends credence to the argument that Mesostoma predation affects Daphnia dynamics in some circumstances. The results suggest that benthic invertebrate predators may affect zooplankton dynamics, especially in shallow ponds.