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Environmental Effects of Energy Crops Research |
Objective: To develop background soils conditions within sites on which hybrid poplar plantations were established in Minnesota in order to assess changes in carbon sequestration through time.
Approach/Background: Because of widespread interest in the role that tree plantations may play in sequestration of atmospheric carbon, it is important to establish reliable baseline data which can be used to assess long-term changes in soil carbon and other chemical characteristics over time resulting from conversion of agricultural land to hybrid poplar. It is equally important to begin development of reliable recommendations for selection of future planting sites based on soils data. This project involves sampling of recently-planted hybrid poplar plantations and establishment of permanent tree growth and soil sampling plots to allow remeasurement of changes at the micro-site level over time. Particular attention is given to quantifying the carbon content of surface soils. The objectives of the project are to: 1) Sample soils to characterize baseline physical and chemical properties of the plantation sites, 2) permanently reference the sampling points to allow resampling in subsequent years to determine crop-induced changes in soil characteristics, 3) calculate water-holding capacity of the upper five feet of soil based on particle size distribution and organic matter content using relations developed from similar soils throughout Minnesota. Data gathered as part of this project will be integrated with similar data collected from hybrid poplar plantations in other locations in Minnesota and Wisconsin to form a region-wide database from which to develop soils- and climate-based growth models.
Status/Accomplishments: All sites have been sampled and soil samples submitted to the laboratory. A total of thirteen sites have been measured and permanent sampling transects established at these sites. Soil bulk density and total soil mass with depth have been determined for all sites. Because the primary objective of this study is accurate determination of soil carbon, particular attention is being paid to quality control on analyses of soil organic matter and carbon. Initial laboratory analysis of soil carbon showed unacceptable variation in soil organic matter among samples. We submitted a subset of samples for soil carbon and organic matter analysis and obtained higher repeatability. A high correlation (R2=0.95) was found between soil organic matter as measured by loss on ignition and soil carbon measured by combustion. Because of high analysis costs for organic carbon, this relationship allows us to accurately estimate the total soil carbon pool size in our soils in a cost-effective manner. A larger set of samples will be resubmitted to the laboratory for analysis of soil organic matter. A report detailing soil carbon pool sizes on the thirteen sites will completed by November.
Summary Date: September 1997
Objective: To evaluate the suitability of short-rotation hybrid poplar plantations for breeding birds: assess the effects of plantation size and shape on breeding birds within and adjacent to plantations; determine affects of plantation on artificial nest predation in habitats surrounding plantations; and understand landscape level consequences of replacing areas of traditional land uses with hybrid poplar plantations.
Approach/Background: All objectives are addressed with field studies on scale-up plantations in western Minnesota. Breeding birds are surveyed in plantations and in habitats surrounding plantations. Comparisons of breeding bird diversity and individual species numbers are made across habitat types to determine the effects of adjacent habitat on birds that occur in plantations and vice versa.
The second effort is addressed with the use of artificial nests baited with quail eggs. Nests this year were placed within the plantation and adjacent CRP or wooded habitat types and rates of predation were compared.
The final task will be addressed with habitat specific breeding bird associations that we have identified within different landuse types in western Minnesota. These data will be coupled with air photos of the plantations and surrounding areas to predict current bird species occurrence and relative abundance patterns and to develop models to predict changes in these patterns if different percentages of the landscape are developed for hybrid poplar.
Status/Accomplishments: We continued to collect baseline data on the large plantations that have been established in the Alexandria area. Three sites have been surveyed for five years, six sites for four years, and four sites for three years. One site, Nelson was surveyed this year, but will be included in the analyses. This site has failed completely and has not been replanted.
We observed a linear growth in mean numbers of individuals and species on plantations as they have aged up to five years. After that, species diversity leveled off. As expected, plantations that have had partial tree failure had greater species diversity.
The largest proportion of bird individuals in plantations in the first six years were short-distance migrants. Numbers of individuals that migrate long-distances to Central and South America increased slightly as the plantations aged. Very few permanent resident birds were found in plantations at any age. Most individuals observed in the plantations at all ages were ground feeding birds associated with open field and pasture habitats. Very few foliage gleaners individuals and those associated with forested habitats were observed in the plantations at any age. An exception was the presence of two Red-eyed Vireos on a five year old plantation in the area where trees are > 36 feet in height.
Studies were conducted on predation rates of artificial bird nests to test the hypothesis that predation rates in adjacent forests and grasslands were not different than predation rates in the plantations. Data collected on predation rates this past summer support this hypothesis. We found no difference in predation rates in the plantation and adjacent habitats.
Summary Date: August 1997
Objective: To conduct comparative studies of small mammal abundance and species composition on hybrid poplar plantations and other land-use types in the landscapes where plantations are being deployed; to assess the nature of habitat represented by hybrid poplar plantation; to understand vegetative and other features of plantations that affect mammal abundance and species composition, including plantation-size and other landscape-scale interactions; to evaluate ways that mammal populations on hybrid poplar plantations and adjacent land-use types interact; to monitor changes in mammal populations and communities on large plantations in the year of establishment and subsequent years; to continue developing an information base and to assess data gathered throughout our studies as input for a landscape model of bird and small mammal responses to plantation establishment. These issues are critical to understanding biodiversity aspects of the possible environmental effects of large-scale biomass development, and for designing and deploying plantations to optimize environmental considerations.
Approach/Background: Since 1992, we have been addressing a variety of questions about potential biodiversity implications of hybrid poplar establishment. These questions have been approached through monitoring and through focused studies on birds and small mammals inhabiting hybrid poplar plantations and nearby and adjacent habitats. Since 1994, most of our research effort has been directed at studies on large, commercial-scale plantations in the Alexandria, Minnesota demonstration scale-up project.
Our research has focused on birds and small mammals. Birds are useful indicators of canopy-habitat conditions and, by virtue of their high mobility, of landscape-scale environmental conditions. Variation in small mammal numbers and species composition are more reflective of smaller-scale environmental variation and of different structural and vegetative habitat conditions. The status of bird studies has been outlined in another report; the mammal studies are summarized here. The small mammal studies have addressed a variety of questions, with the precise methodology (live-trapping or kill-trapping) depending on research needs and feasibility. Mammal sampling has been coupled with vegetation, habitat, or other measurements.
During the past year, we directed considerable effort to integrating the various small-mammal studies conducted since 1992 into a hierarchical landscape perspective. Small mammals in agricultural systems have proven an ideal model for understanding landscape dynamics. Other studies have identified processes that occur at different spatial scales. Our research on small mammals inhabiting hybrid poplar plantations and their interactions with adjacent and nearby habitats provides an excellent real-world application of these ideas.
Status/Accomplishments: Small mammal sampling continued in 1997 on 10 hybrid poplar plantations in Minnesota that had been sampled during 1994, 1995, and 1996. Field work on these sites was completed only in late summer, and only general impressions are available at the time this report is being prepared. In general, we have observed only slight changes in species composition of dominant small mammal species, but a tendency for declining abundance of less-common species. Prairie deer mice continued to be the dominant species on most plantations, indicating that plantations are continuing to function primarily as cropland habitat. We have observed considerable variation in species composition and in temporal patterns of species change. Although we have not been monitoring non-hybrid poplar vegetation on plantations, our subjective impression is that the intensity and effectiveness of weed control is a significant source of this variation. This impression is fully in accord with our earlier focused studies showing that the occurrence on plantations of several mammal species depends heavily on vegetation development. Thus, as we have suggested previously, vegetation management on plantations will continue to be an important determinant of habitat quality.
The 1997 field season produced a number of new observations of mammal use of plantations. Several plantations experienced an outbreak of cottonwood leaf beetles during the summer. On one such plantation (Kreyer), we observed an influx of white-footed mice, which had previously been infrequent on that plantation; it is possible that these animals were responding directly to the availability of a food source (beetles). We observed some beaver damage on one plantation, where these animals had dammed a drainage ditch on the plantation border and cut about 20 trees. Two white-tailed jackrabbits (Lepus townsendii) were observed on plantations, and sitings and tracks of fox (Vulpes vulpes) and deer (Odocoileus virginianus) were common this year.
The prairie vole (Microtus ochrogaster), a state-listed species in Minnesota, was captured on newly established plantations in one complex in both 1995 and 1996. Indeed, this species was captured in notably large numbers on plantations, suggesting that young hybrid poplar plantations may provide suitable habitat if a nearby source population is present. In 1997, we sampled these plantations again, as well as an adjacent tract of native prairie (Regal Meadows, owned by The Nature Conservancy; sampling by live-trapping). We captured no prairie voles on plantation in 1997, suggesting the possibility that these plantations have aged to the extent that they no longer provide suitable habitat. However, we captured only one prairie vole on the adjacent prairie, and very low numbers of meadow voles in all areas. Thus, we are uncertain whether the apparent disappearance of prairie voles from plantations reflects a habitat change or, instead, an annual fluction in numbers of both species of vole. We are interested in determining the possible linkage between this adjacent prairie and the plantation, as well as interactions between prairie voles and the meadow vole, which is more abundant, widespread, and often behaviorally dominant, but more dependent on dense, moist vegetation cover.
We have continued to structure our sampling on these large plantations to address edge effects and the question of whether large plantations have a significant central core area that has reduced abundance and diversity. To date, we have detected subtle patterns (reduced species richness and lower abundance of prairie voles in interior habitats), but these effects do not appear to be as strong as those of vegetation condition.
Our integration of results into a landscape perspective indicates clearly that hierarchical principles apply to the abundance and diversity of mammals on plantations. In previous studies, we showed that mammal abundance and species composition on plantations depends in part on vegetation composition and structure on the plantation (habitat-scale effects). We also have shown that movements between plantation and adjoining habitats are a function of the neighboring habitat (adjacency effects; greater interchange between plantation and grassland than between plantation and forest). Finally, our studies indicate that dominant mammal species on plantations are "blends" of those in other major habitats in agricultural landscapes, suggesting a particular role at the landscape scale. Thus, this work suggests that mammal use of plantations and the function of plantations in agricultural areas involves processes and patterns at a variety of spatial scales.
Summary Date: August 1997
Objective: To determine the habitat value to migratory birds of perennial plantings that can serve as models of biomass energy plantations. Currently, the emphasis is on breeding-season abundance, species richness, and habitat-use patterns of birds in short-rotation hardwood plantations in southeastern Virginia and northeastern North Carolina, in comparison to other dominant local land uses. These hardwood plantations (sweet gum and sycamore) are good models of potential biomass plantations. Understanding the value and limitations of energy crops as wildlife habitat will be necessary in determining their appropriate placement and dominance in the landscape. Opportunities may exist for improving landscapes as wildlife habitat through deployment of short-rotation plantations, while helping to meet national energy needs. Conversely, deployment of biomass plantations without adequate understanding of their habitat attributes could adversely affect regional biodiversity.
Approach/Background: Union Camp corporation established plantations of sycamore and sweetgum in the service area of its Franklin, Virginia paper mill over 20 years ago. The plantations are managed on a rotation of approximately 20 years; some sites are replanted after harvest, and others are allowed to coppice. As these plantations are structurally similar to proposed biomass energy plantations, Union Camp generously allowed their use for this study. The plantations are single-species, with the trees planted in rows, 8' to 10' apart; trees within rows are 6' to 10' apart.
The study is designed to compare bird use of sweetgum (young and mature plantings) to sycamore (young and mature), pine plantations (mature), naturally regenerating hardwoods (young mature and old) and annual row- crop land. Fixed-radius plot surveys of breeding birds were conducted in May and again in June 1996, and twice in each site in June 1997. Some sites were changed between the two years.
The bird surveys were conducted in early morning, when activity levels are maximal. A series of plots (usually 6), 40 meters in radius, were established in each study stand. The observers stood quietly a the center of each plot and recorded all birds seen or heard during a 5-minute count period. Additional bird species detected within the stands but not on the plots, or not in the count periods, were also recorded for use in the richness analyses.
The vegetation of each plot was characterized as to species composition (planted trees and natural regeneration or volunteer), and coverage at canopy, midstory, and shrub levels. Presence of water in the plots was also recorded.
The study is designed for analysis by ANOVA. We attempted to survey three sites in each block (stand type/age) In 1996 we surveyed 41 sites; in 1997, 49 sites in 16 blocks.
Status/Accomplishments: Two full seasons of breeding bird surveys (1996 and 1997) have been completed. In this landscape, annual row-crop farmland is extremely poor habitat for birds at this season, receiving minimal use. In this region, the dominant annual crops are peanuts and cotton, with lesser acreages of soybeans and corn. The peanuts, cotton, and soybeans typically are planted in late May, so the fields are practically bare at the time of the surveys, providing minimal cover, no sheltered nest sites, and few if any insect prey. This result was so clear-cut in the 1996 surveys, that it was decided to drop annual-crop surveys in 1997.
The plantations provide habitat for similar numbers of species and individuals as do the natural hardwood sites. Bird species composition differed more with stand age than with stand type. Young plantations and young regenerating hardwood stands supported a community of early successional birds, including Yellow- breasted Chat, Prairie Warbler, Common Yellowthroat, Indigo Bunting, and Eastern Towhee. Older sites, with establishment of a closed canopy, had fewer of these birds, but were characterized by more of a forest community, including Acadian Flycatcher, Red-eyed Vireo, Ovenbird, and Hooded Warbler. The sycamore and sweetgum differed very little in patterns of bird use.
The older natural-hardwood sites did contain a few bird species not found in the plantations (e.g. Louisiana Waterthrush), but overall their birds were neither more species-rich nor more abundant.
Summary Date: September 1997
Objective: Investigate the effect of hybrid poplar plantations and switchgrass on water quality and compare these effects to both an agronomic crop (wheat) managed under a typical fertilizer/herbicide regime and naturally occurring forest stands.
Approach/Background: A potential benefit associated with changing land use from traditional agriculture to hybrid poplar or switchgrass is water quality enhancement. Inputs of chemicals in managing most agronomic crops are considerably greater than those required for producing hybrid poplar or switchgrass. The goals of this project are to develop agroforestry and riparian management alternatives in the Upper Midwest that can reduce non-point pollution compared to current management practices, and produce goods and services desired by farmers and resource managers (e.g., woody biomass). The continuing research is designed to quantify and contrast the capabilities of short-rotation woody culture (SRWC) plantations and natural forest communities to modify the export of water and non-point source pollutants (e.g., nitrate, phosphorus, and pesticides) compared with traditional agronomic crops.
Four questions are under investigation. (1) Do differences in chemical export exist between standard agricultural cropping systems and a tree crop during establishment? (2) What is the chemical export of a hybrid poplar agroforestry crop over the course of a complete management cycle (e.g., during establishment, maturity and during and following harvesting)? (3) Are natural mature forest communities in the region statistically different from planted poplar stands in the export of chemicals? (4) Do soil physical and chemical properties differ between natural forest communities and hybrid poplar plantations?
Status/Accomplishments: The winter flood of the Red River of the North and the wet spring-summer of 1997 required that soil-water nutrient instrumentation be replaced at the Red Lake County, MN site. Planting of all the crops (hybrid poplar, switchgrass and wheat) has occurred. Our management of the establishment phase is designed to mimic typical producer activity with similar crops; identical cropping practices (planting densities, timing and herbicide applications) are being maintained. Soil solution instruments, damaged by the flood and the subsequent saturated conditions, are being re-installed for monitoring of nutrient and herbicide export in both matrix and macropore flow.
Measurements of the hydrologic regimes and nutrient cycles in the mature plantations and natural forest stands are underway. Established poplar plantations throughout the Red River Valley were identified in 1996. Three natural forest stands were also identified for comparison with the three hybrid poplar sites. Each was instrumented in 1996 with lysimeter nests (tension and zero-tension) to monitor soil solution chemistry. A meteorological network was established to monitor potential evapotranspiration, solar radiation, air temperature, dewpoint temperature, and rainfall. Current soil solution samples suggest that there is no statistically significant difference in nitrogen or phosphorus concentrations exported from natural forests and hybrid poplar plantations. The meteorological data are now being used to convert soil solution concentrations to mass loadings to groundwater.
Flooding conditions this spring and early summer precluded sampling for soil chemical and physical properties at the cropping site in Red Lake County, MN. Sampling and analysis of soils will resume this fall. Soil chemical and physical properties, including soil calcium, carbon, nitrogen, and phosphorus concentrations, pH, cation exchange capacity, infiltration capacity are being determined. These initial values will be compared with values at the end of the study to evaluate the impact of different plant communities on physical and chemical properties of the soil. Comparisons of soil calcium and carbon are expected to be particularly informative.
Summary Date: September 1997
Objective: This research is assessing the effects of biomass crop development on surface and subsurface water quality, runoff and erosion. Hardwood crops grown under different fertigation regimes will be compared to agricultural crops to determine differences in subsurface water quality for the different treatments. Data from this larger-scale production level study will be compared with results from ongoing research-scale studies located in three different areas of the Southeast to help determine how differences in soil types and cropping practices affect water resources. This study builds upon ongoing cooperative research projects, located on the same site, including the development, parameterization and validation of the hydrologic model WATRCOM (developed at North Carolina State University).
Approach/Background: The research is being conducted on a forest products industry site near Sumter, South Carolina. The site is of sufficient size to support a minimum of three replicate experimental plots of 3-5 acres each, and is designed and located to minimize the potential for root interaction and subsurface water interconnectedness.
This research is a larger sale component of ongoing research being conducted by the Biofuels Feedstock Development Program (BFDP) in cooperation with the Tennessee Valley Authority (TVA), and will incorporate information gained from current cooperative research between the Center for Forested Wetland Research (CFW) and the BFDP at this site comparing hardwood crops grown under different fertilization regimes with agricultural crops to determine differences in subsurface water quality for the different treatments. Data is being collected to address chemical and water movement on production level plantings and the study builds upon model development currently underway by the CFW and North Carolina State University (NCSU). Data collected from this study will be used for model validation and, through linkages with geographic information system data, to assist management in selecting the best locations for biomass crop productions based on the potential impacts to water resources associated with these crops.
This project benefits from cooperation among ORNL, CFW, NCSU and the forest products industry. Current cooperative research between ORNL and the CFW is measuring subsurface water quality on irrigation and fertilization research plots on these land holdings. The CFW and NCSU are currently conducting research on a nearby coastal plain site to identify suitable hydrologic models to predict potential effects of hardwood crop production. The forest products industry, the National Council for Air and Stream Improvement (NCASI), Clemson University, and ORNL are currently cooperating on a research project at the Sumter site that is addressing the potential to use pulp and paper wastes and residues either alone or in conjunction with lime or agricultural residues to enhance hardwood tree crop growth. This study is building upon and benefiting from interaction with these three projects.
This research effort is addressing five tasks:
Status/Accomplishments: Water quality sampling for soil and shallow ground water began in February 1996. Samples are collected on a monthly basis. Often the lysimeters and wells are dry, particularly during the summer and fall periods. The lack of water reflects the limited volume of soil water. It is important to note this effect despite the continuous operation of the irrigation system during these periods. This indicates that water applied through irrigation is insufficient to sustain soil moisture levels in the sampling range of the lysimeters (approximately 1 ATM of tension) at the 0.5 to 1 m soil depths. Irrigation levels appear to meet evapotranspirational demands without resulting in excessive infiltration of the applied water. Continued analysis of soil moisture regimes within the trials is needed to confirm this observation.
Preliminary results also indicate a seasonal cycle in NO3 concentrations that coincides with available soil water and growing season. This observation needs to be verified by continued study. Nitrate concentrations were greatest during the winter, presumably a result of soil water derived from precipitation moving the accumulated NO3 through the surface soil. The source of the nitrate appears to be the applied fertilizer, however, specific data on application rates is needed to confirm this.
One year’s data is typically insufficient to address the temporal variation in water quality data that is common with soil water samples. Subsequent analyses will be formulated to consider potential leaching losses, nutrient use efficiency and soil accumulation. Monthly collections will be continued through the next two years with analyses focused on nitrate, cations, pH, and conductivity. The analyses will be integrated with measurements of crop productivity to assess nutrient use efficiency by species within treatments. “Event-based” sampling will be conducted to assess movement of nitrates through the soil profile using the lysimeters.
Summary Date: September 1997
Objective: Determine environmental impacts of converting agricultural land to bioenergy crops. This research focuses primarily on impacts on (1) erosion; (2) runoff quality (nutrients and agrochemicals): (3) runoff quantity and timing (hydrology); (4) groundwater quality; and (5) changes in the soil resource (storage pools of nutrients and agrochemicals, below-ground carbon sequestration, and soil physical properties). A second objective is to evaluate the feasibility of the use of cover corps in reducing erosion in short-rotation hardwood plantations during the establishment period. Feasibility is evaluated by comparing reduction in erosion versus reduction in productivity associated with competition by the cover crop.
Approach/Background: The primary objectives concerning hydrology, runoff and leaching are being accomplished through the use of metered artificial watersheds. Watersheds were created using soil berms to divert all runoff through an H-flume located at the down-slope end of each plot. The flumes are metered using solar powered flow meters and flow proportional samples. All runoff is thus monitored and a proportion sampled for total suspended solids and nutrient content.
There are two blocks in the study with four treatments per block: no-till production corn, switchgrass, sweetgum trees maintained competition free, and sweetgum trees with a tall fescue cover crop strip between tree rows. Plots in each block are matched in size, slope, and slope position. Plots in block one are approximately 1.1 acres in size and plots in block two are approximately 0.5 acres. In addition to the runoff, four pan lysimeters in each plot are sampled after each rain event.
The secondary objective concerning the feasibility of various cover crops is essentially a screening study using several cover crops. Sweetgum seedlings were planted and cover crops established at around the same time, with the objective of providing soil stability during the establishment phase of stand development. Four cover crops, winter rye grass (Lolium multigeonum L., a winter annual grass); tall fescue (Fescuta eliator L., a winter perennial grass); crimson clover (Trifolium incarnatum L., a winter annual legume); and interstate sericea (Lespedeza ameata L., a growing season perennial legume), are compared at two different strip widths (1.22 and 2.44 m) as well as a control with complete competition control. There are three blocks in this study with 9 treatments per block (four cover crops at two strip widths each plus a control).
Each plot is surrounded by a 20 to 25 cm (8-10 in) high soil berm to direct runoff to a sediment fence install at the down slope end of each plot. Erosion was measured as sediment accumulation near the fence. Height, ground-line diameter (gld) and crown width (cr) of trees were measured on a monthly basis.
Status/Accomplishments: Samples of runoff and leachate from the main study are collected after each significant rainfall event. Samples are sent to the TVA lab in Muscle Shoals, Alabama for analysis. Analysis of runoff shows that, except for early in the first growing season when switchgrass was poorly established, erosion was highest in the plots where trees were grown with complete weed control. This effect is persistent at least through the first two growing seasons. Crowns of sweetgum are not fully closed at the end of the third growing season, with bare ground between rows providing poor protection for the soil.
The low erosion of the corn plots compared to the tree plots shows that conversion of agricultural land to SRIC hardwood plantations where weed control is very intensive might not provide better erosion protection, at least prior to crown closure. We expect this relationship to change somewhat as crowns close. The use of a cover crop between rows reduces erosion to levels similar to switchgrass or no-till corn.
While the cover corps provide extra erosion control, the second study also shows they may significantly reduce growth of the trees, a problem considering the high productivity of these stands required to make this operation economically feasible. Growth of sweetgum was reduced to a greater extent by growing season perennials than by winter annuals. Legumes provided no benefit to the growth of sweetgums during the first two years. These results indicate that competition for nitrogen is not driving the growth reductions due to cover crops but soil moisture competition is the mechanism. After two growing seasons, the only cover corp not to significantly reduce volume growth was rye grass. Volume of sweet gum trees was greatest in the control plots followed by rye grass, crimson clover, tall fescue, and interstate sericea.
Erosion protection was significant for all cover crops, with no significant differences among cover crops. 2.44m cover strip widths provided more protection than 1.22 m strips. These results indicated that the best cover crop regime during the establishment phase from the standpoint of reducing erosion while maintaining growth is the 2.44 m strip of rye grass. Since fertilization is normally practiced in SRIC plantations, no benefit from legumes is expected under operational circumstances.
Summary Date: September 1997
Objective: To determining how hardwood energy crops may benefit or impact native wildlife populations. This is a key consideration in the development of a large-scale biofuels industry in the United States. The extensive areas needed to grow trees and grasses for this industry would come from lands converted from other uses across rural America, most likely annual row crops on poor quality sites, pine plantations, and previously harvested hardwood forests. As an indicator of potential wildlife affects, this project surveyed birds during the breeding season on various tree crop, forest, pine plantation and annual row crop sites on the southeastern coastal plain to compare results. Another objective is to determine how growth stage and habitat variables of the tree crops affect bird use. Results are expected to provide useful energy crop guidelines to help integrate native wildlife benefits with productive energy crops.
Approach/Background: An industrial collaborator has made their diverse tree crop plantings available to us for research. This makes possible comparisons between different tree crop types, ages, and acreages that were not previously available. These sites are located in close proximity to each other on the southeastern coastal plain. Sweetgum and sycamore, two tree species likely to be used for energy crops in the southeastern U.S., are represented in these plantings. These sweetgum and sycamore crops range in age from 1 to 21 years old, and in area from 7 to over 400 acres. This opportunity has made it possible for the exploration of differences in bird use that would otherwise have taken years if we had to wait for the trees to grow to reflect ages from planting to harvest, or for sites of different acreage to be planted.
To organize bird and habitat surveys, a research design matrix was developed based on tree crop variability and desired comparisons between alternate land uses. Three sweetgum and sycamore plantings each for categories of age (young and old) and acreage (small and large) were selected from the collaborator’s database. Nearby regenerating hardwood forests of similar age and acreage (three each) were also selected for survey, as were pine plantings and annual row crops.
The research strategy was to survey birds twice during the breeding season using five-minute duration early morning counts at four to six survey points per site. Habitat structure and composition variables (canopy, midstory, shrub layer, ground layer, etc.) were assessed at each of these survey points to link these data to bird survey results, and to the site-level variables (cover type, age, acreage).
Survey data will be statistically analyzed to draw conclusions. Data has been input into spreadsheets in a statistical software package, and dependent variables for bird abundance, species richness, and the ratio of forest interior bird abundance to total bird abundance have been developed for testing. Shannon’s diversity index will also be developed as a dependent variable. Site level characteristics (crop or cover type, age, acreage) and point-specific data (habitat structure and composition) are being used as predictive variables. Tests being run include T tests, multiple linear regression, factor analysis, canonical correlation, and discriminant analysis.
Status/Accomplishments: Preliminary data at these sites were collected and analyzed last year by a similar team, including this year’s PI (then on assignment at ORNL), The National Audubon Society, and Oak Ridge National Laboratory researchers. This provided some interesting results, and helped improve this year’s research design and data collection protocol.
From last year’s preliminary data collection, analysis suggested that sweetgum and sycamore tree crops had statistically similar bird use to each other, and to similarly aged hardwood forests. There was no significant difference in bird use between hardwood tree crops and forests. Tree crops and hardwood forests both experienced significant bird composition, abundance and richness changes as the sites aged, but they did so similarly. Canopy and midstory closure were significant variables in predicting species composition and richness changes. Annual row crops were found to be significantly worse as bird habitat than either hardwood tree crops or regenerating hardwood forests. Acreage of the stands themselves (not including possible contiguous tree covered areas) was not a good predictor of bird use. Data collection was not consistent for all treatments, however, and we had no habitat composition (just structural) data for the survey points.
This year, pine plantations comparable to the older age category for tree crops (around 20 years) were added to the research design, as were very old (40+ years) hardwood forests. These older hardwood forests represent an extension of a probable alternative land use for tree crops – forests that become much more mature. We are curious to find if bird use differences exist between hardwood forests much older than tree plantings ever get, due to harvesting of tree crops around 20 years of age in this region of the country. Annual row crops were not re-surveyed, as last year’s data made it clear these sites are far inferior to other surveyed treatments for birds.
Habitat composition data was collected in addition to the habitat structure data this year, and the research design was more consistant (three replicates were achieved) for each treatment type and category. We are curious to find if older hardwood tree crops surrounding small, existing natural forest fragments in the landscape can act to improve habitat for forest interior birds within these otherwise isolated fragments by buffering them from row cropped and other open areas. This year’s survey included three replicates each of forest fragments 1) surrounded by extensive older hardwood tree crops, and 2) fragments recently exposed to field conditions by harvest of previously surrounding hardwood tree crops. Analysis of the data from this survey are currently being done, and a full report will be developed by October 1, 1997.
Summary Date: September 1997
Objective: The overall objective of this project is to enhance the productivity of hardwood plantations by utilizing papermill residuals as nutrient sources and soil amendments while maintaining high environmental quality standards. Specific objectives are:
Approach/Background: Field, greenhouse, and laboratory experiments were conducted to address these objectives. Specifics are given in the status/accomplishments section.
Status/Accomplishments: The rate of reaction of causticizing residuals (lime mud, green liquor dregs, and slaker grits from two different papermills) were examined in a 28 day laboratory incubation experiment in four soils (Troup, Blanton, Norfolk, and Coxville). All three causticizing residuals reacted faster and achieved higher pHs than agricultural dolomitic limestone. A second incubation experiment was set up to examine the effects of causticizing residuals on soil pH for a longer period of time. Soil pH was determined at 1, 2, 6, 9, and 12 months after the incubation began. Differences in efficacy of the liming materials noted in the short- term incubation remain after 12 months of incubation.
A greenhouse experiment was conducted to determine the effects of soil pH on germination and early seedling growth of corn, cotton, and wheat. Lime mud, grits/dregs combined, and agricultural limestone were utilized to adjust the pH of two soils (Coxville and Norfolk) in the range of 4.8 to 7.6. Application rates ranged from 1,300 to 6,600 lb CaCO3 equivalence per acre on the Coxville soil and from 500 to 3,200 lb CaCO3 equivalence per acre on the Norfolk soil. Ten seeds of each crop plant were planted per pot 1.5 inches below the soil surface and watered daily with 60 ml. Germination counts were performed daily. After a period of 4 to 6 weeks, dependent on the crop, seedlings were harvested, dried at 70 oC, and weighed. Roots were removed from the soil and frozen for later inspection. There was no effect of soil pH or liming material on germination of corn or wheat in either soil. However, application of limestone, lime mud, and grits/dregs delayed and reduced the emergence of cotton in both soils. In some instances increased soil pH increased the strength of the surface crust.
Soil pH was adjusted to six levels in two soils (Coxville and Norfolk) with dolomitic limestone or a combination of grits and dregs. Unlimed soil pH was 4.5 for both soils. The pH established ranged from 4.8 to 6.0 with limestone and 4.9 to 6.8 with grits/dregs. Bare-root seedlings of sycamore and green ash and cuttings of cottonwood were transplanted into the soil and watered daily. Trees were grown for 90 days. The trees were harvested and separated into leaves, stems, and roots. Stem tissue of the original transplant was kept separate from new stem growth, but the old growth of sycamore and green ash roots could not be separated from the new growth. Cottonwood roots were all initiated after planting the cutting. Root appearance was recorded and dry weight determined. All tissues were dried in a forced air oven at 70 oC, weighed, and ground in preparation for nutrient analysis.
Increasing pH of the Norfolk soil increased branch number, weight and length, and root weight. The effects of liming were generally maximal with the first or second increment of liming material and soil pH in excess of 5.0. Liming the Coxville soil had little effect on tree growth. Differences in response to liming between the two soils are likely related to differences in aluminum activity in the soil solution. Although both soils had similar initial pH, the activity of aluminum in the soil solution was likely greater in the Norfolk than in the Rains soil because the Rains soil had a higher organic matter content. Organic matter generally complexes aluminum reducing its phytotoxicity. The source of the liming material, grits and dregs versus agricultural limestone, did not alter the growth response to liming.
The type of liming materials greatly altered available levels of Ca and Mg in the soil and plant tissue contents of these nutrients. Soil and tissue Ca was substantially greater with grits and dregs, than with dolomitic limestone. Whereas, soil and tissue Mg was substantially less with grits and dregs, than with dolomitic limestone. Tissue levels of Mg with grits and dregs may be approaching deficient levels.
A field experiment was conducted to examine nitrogen mineralization and movement with primary clarifier sludge, poultry litter, and Ca(NO3)2 fertilizer. Treatments were unamended soil, sludge and poultry litter to C:N ratio of 60:1, sludge and poultry litter to C:N ratio of 40:1, sludge and poultry litter to C:N ratio of 20:1, sludge and Ca(NO3)2 to a C:N ratio of 40:1, poultry litter alone, and Ca(NO3)2 alone. Poultry litter (7,700 kg ha-1) and Ca(NO3)2 fertilizer provided 168 kg available N ha-1. The poultry litter and sludge had C:N ratios of approximately 10:1 and 100:1, respectively. Sludge was applied at 968, 3861, and 9680 kg ha-1 for C:N ratios of 20:1, 40:1, and 60:1, respectively.
Soil samples were obtained fifteen times between 10 July 1996 and 4 March 1997 (237 days) in 15-cm increments to a depth of 90 cm. Soil samples were extracted with 1 N KCl and NH4 and NO3 determined colorimetrically with an AutoAnalyzer. Mercury tensiometers to record soil moisture tension were installed in 10-cm increments to a depth of 90 cm at five locations in the field. Tensiometers were read three to five times per week. Water flux through the upper 90 cm of soil will be calculated later from the soil moisture tension data.
Total inorganic N and NO3-N in poultry litter treatments was reduced by sludge during the first 42 days after application, indicating a brief period of immobilization. Thereafter, there was no difference in soil inorganic N among sludge amended and unamended treatments. Because of limited rainfall during the period of immobilization there were no effects of the sludge on NO3- leaching. The leaching of NO3-N was well correlated with rainfall. Depth of movement was approximately equal to 15 plus rainfall, times 1.2 (all units in cm).
An incubation experiment was conducted under controlled conditions with the same soil, sludge, and poultry litter used in the field experiment, to limit the extent of soil and environmental variability encountered. Sludge application resulted in greater N immobilization in the laboratory incubation experiment, than in the field experiment. Smaller particle sizes and greater contact between sludge and poultry litter in the laboratory incubation, in comparison to the field experiment, are likely the cause of greater N immobilization.
Summary Date: September 1997
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File Created: October
13, 1997; Last updated: Thursday, 11-Nov-1999 10:23:31 EST