Methods of Soil Resampling to Monitor Changes in the Chemical Concentrations of Forest Soils

Recent soils research has shown that important chemical soil characteristics can change in less than a decade, often the result of broad environmental ...

Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment

Phosphorus (P) is a critical limiting nutrient in agroecosystems requiring careful management to reduce transport risk to aquatic environments. Routine ...

University of Vermont

The goal of this study was to evaluate the periareolar injection of technetium 99m sulfur colloid to identify axillary sentinel nodes and compare the number of sentinel lymph nodes identified with preoperative lymphoscintigraphy to intraoperative biopsy using a handheld gamma probe. A total of 104 consecutive patients diagnosed with invasive breast cancer participated in this prospective study, with 81 patients receiving an intradermal periareolar injection and 23 patients receiving an intradermal peritumoral injection of filtered technetium 99m sulfur colloid. Preoperative lymphoscintigraphy was performed for sentinel node mapping and localization. In addition to selective sentinel node biopsy, axillary dissection was performed on all patients to determine false-negative rates. Routine histologic staining was performed on all identified nodes, along with immunohistochemical staining of sentinel nodes negative on initial routine staining. With an intradermal periareolar injection, the sentinel node identification rate was 91.4% (74/81), axillary metastatic rate 35.1% (26/74), sentinel node positive only 61.5% (16/26), and false negative 3.8% (1/26). With an intradermal peritumoral injection, the sentinel node identification rate was 91.3% (21/23), axillary metastatic rate 42.9% (9/21), sentinel node positive only 88.9% (8/9), and false negative 0% (0/9). A total of 241 sentinel nodes were identified with biplanar lymphoscintigraphy and 173 sentinel nodes were harvested during surgery, yielding a 28.2% increase in sentinel nodes identified with lymphoscintigraphy. This study demonstrates that intradermal periareolar injection of filtered technetium 99m sulfur colloid is successful in identifying axillary sentinel nodes with a low false-negative rate. Preoperative lymphoscintigraphy aids in the identification and surgical planning of sentinel node biopsy and provides an objective measure of surgical performance.

Periareolar injection for localization of sentinel nodes in breast cancer patients.

Atmospheric deposition of nitrogenous compounds to ombrotrophic peatlands (i.e., those that have peat layers higher than their surroundings and receive nutrients and minerals exclusively by precipitation) has the potential to significantly alter ecosystem functioning. This study utilized the acetylene inhibition technique to estimate the relative importance of denitrification in nitrogen removal from a primarily ombrotrophic peatland, in an attempt to estimate the threat of increased nitrogen loadings to these areas. Estimates of mean rates of denitrification ranged from -2.76 to 84.0 ng N(2)O-N cm(-3) h(-1) (equivalent to -150 to 4800 microg N(2)O-N m(-2) h(-1)) using an ex situ core technique and from -8.30 to 5.98 microg N(2)O-N m(-2) h(-1) using an in situ chamber technique. Core rates may have been elevated over natural field levels due to effects of disturbance on substrate availability, and chamber rates may have been low due to diffusional constraints on acetylene and N(2)O. Net nitrification was also measured in an attempt to evaluate this process as a source of nitrate for denitrifiers. The low rates of net nitrification measured, in combination with the low rates of in situ denitrification and the very low amounts of free nitrate measured in this peatland, suggests that inorganic N turnover in this wetland is low. Results showed that nitrate was a limiting factor for denitrification in this peatland, with mean rates from nitrate-amended cores ranging from 13.1 to 260 ng N(2)O-N cm(-3) h(-1), and it is expected that increases in nitrogen loadings will increase denitrification rates in this ecosystem.

Denitrification as a nitrogen removal mechanism in a Vermont peatland.

Wetlands are major sources of carbon dioxide, methane, and other greenhouse gases released during microbial degradation. Despite the fact that decomposition is mainly driven by bacteria and fungi, little is known about the taxonomic diversity of bacterial communities in wetlands, particularly Sphagnum bogs. To explore bacterial community composition, 24 bogs in Vermont and Massachusetts were censused for bacterial diversity at the surface (oxic) and 1 m (anoxic) regions. Bacterial diversity was characterized by a terminal restriction fragment length (T-RFLP) fingerprinting technique and a cloning strategy that targeted the 16S rRNA gene. T-RFLP analysis revealed a high level of diversity, and a canonical correspondence analysis demonstrated marked similarity among bogs, but consistent differences between surface and subsurface assemblages. 16S rDNA sequences derived from one of the sites showed high numbers of clones belonging to the Deltaproteobacteria group. Several other phyla were represented, as well as two Candidate Division-level taxonomic groups. These data suggest that bog microbial communities are complex, possibly stratified, and similar among multiple sites.

Comparison of bacterial communities in New England Sphagnum bogs using terminal restriction fragment length polymorphism (T-RFLP).

Mercury (Hg) is an atmospheric pollutant that, in forest ecosystems, accumulates in foliage and upper soil horizons. The authors measured soil and litterfall Hg at 15 forest sites (northern hardwood to mixed hardwood/conifer) throughout Vermont, USA, to examine variation among tree species, forest type, and soils. Differences were found among the 12 tree species sampled from at least two sites, with Acer pensylvanicum having significantly greater litterfall total Hg concentration. Senescent leaves had greater Hg concentrations if they originated lower in the canopy or had higher surface:weight ratios. Annual litterfall Hg flux had a wide range, 12.6 to 28.5 µg/m(2) (mean, 17.9 µg/m(2) ), not related to forest type. Soil and Hg pools in the Oi horizon (litter layer) were not related to the measured Hg deposition flux in litterfall or to total modeled Hg deposition. Despite having lower Hg concentrations, upper mineral soil (A horizons) had greater Hg pools than organic soil horizons (forest floor) due to greater bulk density. Significant differences were found in Hg concentration and Hg/C ratio among soil horizons but not among forest types. Overall, our findings highlight the importance of site history and the benefits of collecting litterfall and soils simultaneously. Observed differences in forest floor Hg pools were strongly correlated with carbon pools, which appeared to be a function of historic land-use patterns.

Mercury in litterfall and upper soil horizons in forested ecosystems in Vermont, USA.

Environmental change is monitored in North America through repeated measurements of weather, stream and river flow, air and water quality, and most recently, soil properties. Some skepticism remains, however, about whether repeated soil sampling can effectively distinguish between temporal and spatial variability, and efforts to document soil change in forest ecosystems through repeated measurements are largely nascent and uncoordinated. In eastern North America, repeated soil sampling has begun to provide valuable information on environmental problems such as air pollution. This review synthesizes the current state of the science to further the development and use of soil resampling as an integral method for recording and understanding environmental change in forested settings. The origins of soil resampling reach back to the 19th century in England and Russia. The concepts and methodologies involved in forest soil resampling are reviewed and evaluated through a discussion of how temporal and spatial variability can be addressed with a variety of sampling approaches. Key resampling studies demonstrate the type of results that can be obtained through differing approaches. Ongoing, large-scale issues such as recovery from acidification, long-term N deposition, C sequestration, effects of climate change, impacts from invasive species, and the increasing intensification of soil management all warrant the use of soil resampling as an essential tool for environmental monitoring and assessment. Furthermore, with better awareness of the value of soil resampling, studies can be designed with a long-term perspective so that information can be efficiently obtained well into the future to address problems that have not yet surfaced.

Measuring environmental change in forest ecosystems by repeated soil sampling: a north american perspective.

Streambank erosion is an important contributor to sediment and nutrient export. This study determined total P (TP), soil-test P (Modified Morgan's, MM-P), and the degree of P saturation (DPS) in eroding riparian soils along four Lake Champlain Basin stream corridors. We investigated the relationship between these data and soil texture and with a series of GIS-derived landscape metrics. We also quantified the potential P load from eroding streambanks using remote sensing. Soil samples were taken from 76 erosion features to a depth of 90 cm on four streams in Chittenden County, Vermont. Mean concentrations of TP and MM-P were similar among the watersheds and through depth. Neither TP, MM-P, nor DPS were well related to texture. Metrics from available spatial databases for parent material, soil series, and landscape position were somewhat useful in predicting TP and MM-P. Eroding streambank soil from 2004 through 2007 in the four streams was estimated to contain from 0.5 to 3.9 Mg of TP and 1.4 to 10.9 kg MM-P. The mean DPS in each watershed was <18% and, along with low MM-P concentrations, suggests that eroded streambanks may act as sinks rather than sources of P. The portion of total nonpoint P export potentially contributed by streambank erosion ranged from 6% in the stream with the lowest erosion rate to 30% in the stream with the highest erosion rate. Based on TP values, the P contribution of these streambanks could be considerable, and more information is needed on their actual contribution to bioavailable P in receiving waters.

Phosphorus Characterization and Contribution from Eroding Streambank Soils of Vermont's Lake Champlain Basin.

Riparian buffers can act as a phosphorus (P) source under active stream bank erosion. Using soil and landscape variables (soil series, drainage class, organic matter, and pH) to index P concentrations could improve P loss risk tools for buffers. The objectives of this study were (i) to determine if soil properties could predict total and labile P concentrations within a 10-ha riparian buffer and (ii) to quantify the degree of spatial dependence of P and related properties. Soil samples were taken in 15-cm increments to a depth of 60 cm using a grid ( = 71) from an established riparian buffer along the Rock River in Vermont. Total soil P (TP), plant-available P determined by Modified Morgan extraction (MM-P), pH, soil organic matter (SOM), soil texture, and select cations were measured. We found that TP (152-1536 mg P kg) and MM-P (0.4-14.6 mg kg) ranged widely, with distinct differences between soil series. Mean TP and MM-P were greater in alluvial and glaciolacustrine soils compared with glacial till. Across all samples, MM-P was weakly related to soil properties; however, total labile P (orthophosphate + organic P measured by ICP) and unreactive labile P (ICP-P - colorimetric-P) could both be predicted by SOM ( = 0.59 and 0.73, respectively). Strong spatial dependence was found for P and related properties as revealed by geospatial analyses. Results show that P availability in the buffer was strongly related to soil genesis and support site-specific approaches for P loss risk evaluation in buffers.

Donald S. Ross

Department of Plant and Soil Science

University of Vermont

Methods of Soil Resampling to Monitor Changes in the Chemical Concentrations of Forest Soils

Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment

Donald S. Ross

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Plant and Soil Science

University of Vermont

Methods of Soil Resampling to Monitor Changes in the Chemical Concentrations of Forest Soils

Measuring Phosphorus Release in Laboratory Microcosms for Water Quality Assessment

Department of Plant and Soil Science