Hal O. Liechty

Changes in microclimate after stand conversion in two northern hardwood stands

Abstract Changes in air temperature, soil temperature, and soil moisture were monitored for 5 years in two northern hardwood stands after whole-tree harvesting and conversion to red pine ( Pinus resinosa Ait.) plantations. Soil temperatures at a depth of 5 cm and maximum air temperatures 2 m above the soil surface were increased 5–25% after stand conversion. Soil moisture content at a depth of 5 cm was increased by 10–20% in one stand but not in the other. Differences in stand, soil, and topographical characteristics between the two stands did not have any apparent effect on the magnitude of air or soil temperature changes after stand conversion. However, higher initial stand density and soil water holding capacity appeared to be related to increased soil moisture content at one of the sites. The increased soil temperatures after conversion were not only a result of the removal of the northern hardwood canopy but also the removal and redistribution of the forest floor caused by whole-tree harvesting. Five years after stand conversion air temperature, soil temperature, and soil moisture showed no evidence of recovering from initial post-harvest levels.

A process-based growth model for young red pine

Abstract A carbon-balance, process-based growth model was developed to simulate the growth of young red pine ( Pinus resinosa Ait.). The dry weights of current, 1-year-old, 3-year-old needless, stems and branches, and roots of individual trees were considered as state variables. The hourly rate of photosynthesis was calculated with solar radiation, air temperature, leaf water potential, and leaf age as driving variables by assuming that the needles experience the same incident light density. Maintenance respiration rate was assumed to be a function of surrounding temperature. The seasonal allocation of assimilates to each compartment was determined by the activity of each compartment and was regulated by soilwater potential. The translocation of carbohydrate reserves, litter fall, and root turnover were incorporated in the model. The simulated results fit well with observed values from three plantations in the central Upper Peninsula of Michigan.

Productivity and growth efficiency in sugar maple forests

Abstract Sugar maple ( Acer saccharum Marsh.)-dominated northern hardwood forests were examined at four locations along an acid deposition and climatic gradient in the Great Lakes region of the USA. The study sites were matched in terms of physiography, soils, stand history, and vegetative characteristics. Measurements of basal area and biomass growth were made for the 1988–1991 growing seasons. There were no significant differences in either basal area of biomass increment among the four sites over the 4 year period. There was a great deal of year-to-year variability with relative basal area growth rates ranging from as low as 0.2% to as high as 2.4% on a single site in successive years. Growth efficiency measures reflected this variability with as much as an 800% difference between successive years on a single site. When coupled with year-to-year variability of up to 34% in leaf area related to heavy seed years and defoliation, this indicates that growth efficiency and leaf area measures are not consistent indicators of aboveground productivity for tolerant deciduous species, especially if derived from short-term measurements or temporary plots.

Effects of 76 Hz electromagnetic fields on forest ecosystems in northern Michigan: tree growth

Since 1984, the possible effects of extremely low-frequency electromagnetic (EM) fields generated by a 76 Hz communication antenna on the growth and productivity of four deciduous and one coniferous species have been studied in the Upper Peninsula of Michigan. Results from two research sites are discussed here: one site near an antenna element and a control site located 50 km from the communication system. Growth models for individual tree diameters were developed for northern red oak (Quercus rubra), paper birch (Betula papyrifera), aspen (Populus tremuloides with a few individuals ofP. grandidentata), and red maple (Acer rubrum). A growth model for individual tree height was developed for young red pine (Pinus resinosa). Average differences between the observed and predicted growth were calculated for each growing season and then compared between the study sites and across the study periods to evaluate changes in growth patterns which could be attributed to EM field effects. For aspen and red maple, the results showed a stimulation of diameter growth at magnetic flux density levels of 1 to 7 milliGauss; height growth of red pine was increased at about the same exposure levels. There are no clear indications of an EM field effect on total annual diameter growth for either of the other two species.

Impacts of annual weather conditions on forest productivity: a case study involving four North American deciduous tree species

The response of four northern deciduous tree species to annual climate variation is quantified at two intensively measured sites in northern Michigan, USA. Response to changes in temperature and moisture differ with the species and is dependent on other site conditions. Relationships identified in these field studies indicate that projected climate changes may have dramatic effects on the productivity of at least some commercially important tree species in the northern United States.

Soil Gas Efflux in Perennial Bioenergy and Conventional Agricultural Crops in the Lower Mississippi Alluvial Valley

ABSTRACT The Lower Mississippi Alluvial Valley (LMAV) has favorable attributes for producing biofuels. Two study sites were established on retired agricultural fields in the LMAV to explore switchgrass (SWITCH) and eastern cottonwood (CTWD) as biofuel feedstocks. A soybean-sorghum rotation (CROP) was also established as a conventional cropping system. Soil efflux gas (carbon dioxide [CO2], methane [CH4], and nitrous oxide [N2O]), microbial biomass carbon (Cmic) and dehydrogenase activity were measured for two years. Cumulative growing-season soil CO2 efflux of SWITCH exceeded that of CROP; SWITCH had higher daily CO2 efflux than CTWD and CROP in some months. SWITCH and CTWD had greater Cmic than CROP at both sites. Soil CH4 and N2O efflux rates were low for much of the study, with only short-term differences in soil CH4 observed. Converting these retired agricultural sites to SWITCH increased soil CO2 efflux relative to CROP, with increases attributable to greater plant and microbial respiration.

Assessment of Labile Organic Carbon in Soil Using Sequential Fumigation Incubation Procedures

Management practices and environmental changes can alter soil nutrient and carbon cycling. Soil labile organic carbon, a readily decomposable C pool, is highly sensitive to disturbance. It is also the primary substrate for soil microorganisms, which is fundamental to nutrient cycling. Due to these attributes, labile organic carbon (LOC) has been identified as an indicator parameter for soil health. Quantifying the turnover rate of LOC also aids in understanding changes in soil nutrient cycling processes. A sequential fumigation incubation method has been developed to estimate soil LOC and potential C turnover rate. The method requires fumigating soil samples and quantifying CO2-C respired during a 10 day incubation period over a series of fumigation-incubation cycles. Labile organic C and potential C turnover rate are then extrapolated from accumulated CO2 with a negative exponential model. Procedures for conducting this method are described.

Poultry Litter Fertilization Impacts on Soil, Plant, and Water Characteristics in Loblolly Pine (Pinus taeda L.) Plantations and Silvopastures in the Mid-South USA

Increasing global human populations and wealth have resulted in increased demands for animal protein and widespread use of confined animal feeding operations to meet added animal protein consumptive demands. Disposal of animal wastes from these operations can be ecologically and environmentally problematic (Kellogg et al., 2000; Roberts et al., 2004; Shober & Sims, 2003). Poultry production is an important source of this protein and is a major agricultural industry in the United States. The United States is the world’s largest producer and second largest exporter of poultry meat (UDSA Economic Research Service, 2009). Four-fifths of the United States poultry industry is comprised of broiler meat production. Broiler meat production is largely concentrated in Southeastern states (Alabama, Arkansas, Florida, Georgia, Kentucky, Louisiana, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas and Virginia), with 82% of U.S. broiler production occurring in these states (National Agricultural Statistic Service, 2008). Broiler production results in the generation of massive amounts of litter, a mixture of feces, feed, feathers and bedding materials such as straw, peanut or rice hulls, and wood shavings (Gupta et al., 1997; Weaver, 1998). The U.S.A. poultry industry produces more than 11 million Mg of litter per year (Cabrera & Sims, 2000). Broiler poultry litter contains several plant macroand micronutrients (Table 1), which makes it desirable as an agricultural fertilizer (Sistani et al., 2008). Following removal from poultry production facilities, litter is commonly applied to nearby pastures, hay meadows, and agricultural crops such as corn and cotton to increase crop production and quality (Harmel et al., 2004; Sims & Wolf, 1994). Applications of poultry litter ranging from 4.5 to 11.2 Mg ha-1 yr-1 are common to supplement or replace inorganic annual fertilizer additions to pastures (Adams et al., 1994). Thus, poultry litter application is an efficient and potentially cost-effective method for improving forage production within the vicinity of production facilities, which helps to sustain non-poultry related agriculture economies in poultry producing regions. Substitution of broiler litter for inorganic fertilizers continues to increase in the southeastern U.S.A. as prices of inorganic fertilizers escalate (Funderberg, 2009).

Soil Nitrogen mineralization under northern hardwood forests along a sulfate and nitrate deposition gradient in the Great Lakes region

Net N mineralization (ammonification and nitrification) in the 0–10 cm mineral soil zone of five northern hardwood forest sites along a gradient of SO42− and NO3− deposition from northeastern Minnesota to central lower Michigan was measured by anin situ buried bag technique at monthly intervals from September 1987 to April 1990. Soil nitrification rates (36.9 to 46.7 kg N · ha−1 · yr−1) increased from north to south among the five study sites and were strongly associated with soil temperature (r = 0.87,p < 0.001). The rates of soil ammonification (66.8 to 84.1 kg N · ha−1 · yr−1) and amounts of total N mineralized (103.7 to 130.6 kg N · ha−1 · yr−1) did not show a clear regional trend across the gradient sites. Significant correlations between SO42−(r = 0.82,p < 0.001), NO3−(r = 0.77,p = 0.003) deposition and the adjusted means of ammonium-N after removing the effects of soil temperature indicated that SO42− and NO3− deposition had significantly impacts on ammonification process. Soil pH did not correspond to the gradient of H+ deposition, which was not correlated with either ammonification or nitrification rates across the study sites.

Simulation of soil nitrogen mineralization and nitrification in two northern Hardwood forest ecosystems

A process-based, biological model is presented that simulates soil nitrogen (N) mineralization and nitrification in two northern hardwood forest ecosystems in the Upper Peninsula of Michigan. The soil system is divided into two compartments (forest floor and mineral soil) since quantity and quality of the organic substrate, and the important driving variables (temperature and moisture) for the model vary between these two compartments. The model focuses on the central position of microorganisms in the N mineralization and nitrification processes, and the use of multiplicative factors to account for the effect of temperature, moisture and carbon(C):N ratio on these processes. The model has been validated with data from two northern hardwood stands in the Upper Peninsula of Michigan. A close agreement between calculated and observed monthly means was obtained in both stands, especially for net N mineralization, which plays a very important role in determining available N. The nitrification rates had relatively larger variation than the N mineralization rates, but the model adequately described the seasonal trends of the observed values. A simple sensitivity analysis was performed to assess the response of the model to changes in important variables (temperature, moisture, organic N, and C:N ratio) between the two study sites. This analysis showed that increased temperature and higher organic N levels consistently increased N mineralization and nitrification in the both stands. The model’s results were most sensitive to moisture changes in forest floor, but were not sensitive to moisture changes in the mineral soil. In contrast, C:N ratio was influential in the mineral soil, but did not have any effect in the forest floor.