Phillip E. Pope

Characterization of coarse woody debris across a 100 year chronosequence of upland oak–hickory forests

In most forest ecosystems, the total amount of coarse woody debris and its distribution into decay classes change over time from harvest to old growth stages. The relationship of decomposition classes to substrate quality is important to determine the contribution of woody debris to ecosystem nutrient cycling and forest development. The two objectives of this study were: (1) to determine if down dead wood (DDW) nutrient content varied with decomposition class or forest stand age; (2) to determine if DDW decomposition classes were related to indicators of substrate quality. Volume, mass, and indicators of substrate quality, such as N content and lignin:N ratio, were determined for woody debris from several decomposition classes in upland hardwood forest stands of different ages in southern Indiana, USA. Results showed a large decrease in volume and mass of DDW from recently harvested to mature stands. The dominant decomposition class shifted from Class II to Classes III and IV with increasing stand age. No Class I woody debris was found within any of the study plots. Nutrient concentration (N, S, and P) and carbohydrate fractions (soluble, hemicellulose, cellulose, and lignin) all varied significantly among certain decomposition classes, but N and P concentration and the C:N ratio were the best indicators of decomposition class. Patterns of P retention in decomposition classes suggested a strong potential for immobilization of this nutrient in woody debris. Based on substrate quality groupings, there were three distinguishable decomposition classes: Classes II and III, Class IV, and Class V.

Concurrent establishment of ground cover and hardwood trees on reclaimed mined land and unmined reference sites

Abstract A reclaimed mined site and an unmined reference site were compared to assess the effectiveness of reclaiming land according to United States Public Law 95-87, The Surface Mining Control and Reclamation Act of 1977, for forest land use. Red oak (Quercus rubra L.) and black walnut (Juglans nigra L.) seedlings were planted concurrently with K-31 fescue (Festuca arundinacea Schreb.) and red clover (Trifolium pratense L.), and maintained under the same levels of management on mined and unmined sites in Sullivan County, Indiana. Soil chemical and physical properties were evaluated, and ground-cover productivity was assessed for 4 years. Survival and growth of bareroot and container seedlings as influenced by chemical control of competing ground cover was followed for 7 years. After liming and fertilization, mine soil physical properties rather than chemical properties were apparent factors affecting survival of tree seedlings and productivity of both tree species and ground-cover vegetation. Survival percentage of black walnut and red oak seedlings on the mine site was adequate to meet the 450 trees acre−1 (≈ 1112 trees ha−1) stocking level specified by current laws only when ground cover vegetation was controlled. Survival and height growth of both tree species was greater on the reference site than on the mine site, especially when ground-cover vegetation was controlled. The poorer growth on the mine site was due to severe stem dieback on plots with no ground-cover control. The results show the importance of controlling the competing ground-cover vegetation during seedling establishment on reclaimed mine soils, particularly during the first 4 years following outplanting.

Biomass and nitrogen dynamics in an irrigated hybrid poplar plantation

Abstract A 3-year study measured the effects of ground cover treatments and N fertilization on biomass and nitrogen dynamics in an irridiated hybrid poplar (Populus deltoides Bartr. X P. trichocarpa Torr. and Gray, clone NC-9922) plantation in northern Wisconsin, U.S.A. Annually fertilized (112 kg N ha−1 year−1) and unfertilized plots were maintained weed free (bare soil), allowed to revegetate with native weeds, or seeded to birdsfoot trefoil (Lotus corniculatus L.). Biomass and N in trees and ground-cover vegetation were sampled before and after each growing season. Trees in bare-soil plots responded to fertilization primarily in the third growing season, but total biomass of 3-year-old trees was not increased by annual fertilization. In plots with a ground cover,fertilization increased tree growth but cover crop treatment had no effect. Ground cover biomass peaked during the second growing season, but declined thereafter, primarily due to reductions in below-ground biomass. Estimated recovery of fertilizer N was low in bare soil plots after 3 years, with 2% in the ‘perennial’ portion of the trees and 13% in the leaf litter. In contrast, recovery in the cover crop plots was 44%–51% in years 2–4. During that period, both biomass and N pool dominance shifted from primarily cover crop to primarily trees. The ground cover appeared to reduce tree growth in years 1–3, but total tree biomass after 4 years was greater in fertilized plots with ground cover (22.7 Mg/ha) than in fertilized bare soil plots (16.7 Mg/ha). Biomass production in fertilized trefoil plots in the fourth year (15.1 Mg ha−1 year−1, excluding leaves) exceeds that of local forests by 50%, and may be comparable to corn productivity in the area.

Fine root dynamics across a chronosequence of upland temperate deciduous forests

Following a major disturbance event in forests that removes most of the standing vegetation, patterns of fine root growth, mortality, and decomposition may be altered from the pre-disturbance conditions. The objective of this study was to describe the changes in the seasonal and spatial dynamics of fine root growth, mortality, and decomposition that occur following removal of standing forest vegetation. Four upland temperate deciduous forest stands in southern Indiana, USA were chosen for this study. The ages of the stands, as represented as the number of growing seasons since forest overstory removal, were 4, 10, and 29 years at the beginning of the study in 1995. A mature stand, about 80-100 years since last harvest, was chosen to represent the pre-harvest conditions. A combination of soil cores and ingrowth cores were used to assess stand-level rates of fine root growth, mortality, and decomposition. Results show that fine root growth increases significantly after harvesting, but declines as the stand matures. In all stands, fine root mortality and decomposition are nearly equal to or greater than fine root growth. Fine root growth in the A horizon (0-8 cm) is significantly greater than in the B horizon (8-30 cm) in the 4, 29, and 80-100-year-old stands. In the 4- and 10-year-old stands fine root growth in the A horizon peaks earlier in the year than in the B horizon. Fine root biomass recovers rapidly in these upland hardwood stands following forest removal due to high rates of fine root growth; however, the distribution of fine root growth between the A and B soil horizons differs from pre-harvest conditions during the first 10-30 years.

Alfalfa N2-fixation enhances the phosphorus uptake of walnut in interplantings

Walnut tree seedlings exhibited greater phosphorus (P) uptake from32P-labelled hydroxyapatite when interplanted with alfalfa than with other walnuts, black locust, or orchard grass. Three mechanisms are proposed as possible explanations of this enhnaced P uptake by walnut. In this study, diffusion of solubilized apatite-P to the roots of walnut at points of walnut-alfalfa root intersection is believed to be the operative mechanism. Phosphorus is solubilized due to rhizosphere acidification of alfalfa during nitrogen fixation. These results underscore the interdependence of nutrient cycles. Enhancement of the phosphorus cycle through manipulation of the nitrogen cycle has important implications for world food and fiber production.

Intensive culture of European black alder in central Indiana, U.S.A.: biomass yield and potential returns to farmers

Abstract Growing interest in woody biomass for energy in the midwestern U.S. will require information on species and site productivities. We investigated 3, 6 and 14 year yields of the nitrogen-fixing tree species. European black alder, at three spacings on a marginally productive soil in central Indiana, U.S.A. The highest yield was 10 Mg ha −1 yr −1 at age three at the closest spacing of 0.5 × 1 m. Other spacings and ages provided smaller yields. Fertilization with phosphorus and potassium only provided a response in the initial 3 year rotation. Whole-tree and stem-only harvests removed varying levels of nutrients from the site. However, on these marginally productive sites where N and sometimes P are limiting, sustainable harvesting could be maintained due to the nitrogen-fixing capability of this species and the effects of N fixation on P availability. Preliminary economic analyses indicated that growing biomass on farms could be profitable, but only with farm or forestry program cost-sharing assistance. Where establishment expenses could be reduced by wider spacings, the use of seed rather than seedlings, or farmer-substituted labor, returns to the farmer were competitive with row-crop and timber production.

A comparison of three rock phosphates for use in forest soils.

The use of rock phosphates in forestry is an important and economic alternative to soluble phosphorus sources for some soils. Interactions of tree rhizosphere processes and rock phosphates may increase availability and uptake efficiency, but interactions of rock phosphates in different forest soils may reduce availability. This study examined phosphorus diffusion rates in three forest soils fertilized with either of three rock phosphates of varying solubility. Diffusion rates were calculated from phosphorus buffer powers determined by desorption in pH adjusted solutions. Diffusion rates and rock phosphate solubilities were compared to quantities of phosphorus in whole-seedlings of black locust (Robinia pseudoacacia L.) grown in the experimental soils fertilized with the experimental rock phosphates. Results indicated that phosphorus uptake varied by rock phosphate solubility, but the pattern was different for each soil. Increasing solubility did not always increase phosphorus uptake. Diffusion rates with and without pH adjustment proved superior in predicting phosphorus availability in each soil and therefore may provide a better index for forestry use than rock phosphate solubility.

Pisolithus tinctorius increases the size of nursery grown red oak seedlings

Inoculation of nursery beds with vegetative mycelia of P. tinctorius (Pt) significantly increased the number of salable 1–0 red oak seedlings produced in two of three years and the average stem height and diameter each year. The percentage of Pt mycorrhizal primary lateral roots on seedlings in the inoculated plots was significantly correlated with stem diameter and weight of lateral roots. The high rates of colonization of short roots by Pt in inoculated plots suggested the test fungus could successfully compete with indigenous fungi in forming mycorrhizae.