REPRINTED FROM Second Biennial Southern SiIvicultural Research Conference (GTR SE-24). AN OVERVIEW OF WATERSHED AND NUTRIENT CYCLING RESEARCH

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1 REPRINTED FROM Second Biennial Southern SiIvicultural Research Conference (GTR SE-2). AN OVERVIEW OF WATERSHED AND NUTRIENT CYCLING RESEARCH AT THE REYNOLDS HOMESTEAD RESEARCH CENTER ḻ/ T. R. Fox, J. A. Burger, R. E. Kreh, and J. E. Douglass 2/ Abstract. A project designed to quantify the changes brought about by clearcut harvesting and site preparation has been established on the Virginia Piedmont. Four forested watersheds were selected for study in Three of the watersheds were commercially clearcut during the summer of The fourth watershed remained undisturbed and serves as a control. The clearcut watersheds were site prepared in July Three separate treatments: chop and burn; sheardisk (1-pass); and shear, rake-pile, disk (3-pass), representing three levels of site preparation intensity were applied. The site prepared watersheds will be planted to loblolly pine in March H-flumes and ceramic cup lysimeters were installed to monitor changes in streamflow and soil solution. Preliminary results indicate that prior to site preparation, nutrient levels in both soil solution and stream water were higher in the clearcut watersheds. Suspended sediment levels in stormflow from the clearcut watersheds were also higher. Post site preparation nutrient levels in soil solution were higher than levels in the control. Levels of NO^-N in soil solution and stream water from both the clearcut and the site prepared watersheds were higher than NH^-N. This indicates that nitrification may be an important process in disturbed ecosystems on the Piedmont. INTRODUCTION The importance of the southeastern United States as a timber producing region is expected to increase substantially in the next 20 years. It has been estimated that by the end of this century the southeast will produce roughly 50% of the total roundwood harvest of the U.S. (USDA Forest Service, 1973). However, the current stand quality and age of much of the commercial forest land in the region _!/ Paper presented at the Southern Silvicultural Research Conference, November -5, 1982, Atlanta, Georgia. Financial support provided by Champion International Corporation, U.S. Forest Service, Mclntire-Stennis and the Reynolds Homestead Research Center. _2/ Graduate Research Assistant, Assistant Professor of Forest Soils and Research Associate, respectively, Department of Forestry, Virginia Polytechnic Institute and State University, Blacksburg, Virginia, and Principal Hydrologist, U.S. Forest Service, Coweeta Hydrologic Laboratory, Franklin, North Carolina. may not be adequate to meet future demands (Southern Forest Resource Analysis Committee, 1969). In addition, over,000 acres of potential pine forest land are lost each year because of inadequate regeneration following harvest or direct conversion of forest land to other uses (Knight, 1977). In order to meet the increasing demands on the forest resources of the southeast, intensive forest management practices will have to be applied to a larger acreage. On the Piedmont, this will probably include the conversion of mixed pinehardwood stands to short rotation pine plantations (Switzer and Nelson, 1973). Reported declines in productivity of intensively managed second rotation plantations in other parts of the world (Whyte, 1973; Will and Ballard, 1976) have generated concern about similar declines in productivity in the southeast. Agricultural experiences in the past have demonstrated that Piedmont sites are particularly susceptable to productivity declines under intensive management. -68-

2 A number of recent symposia have been held on the effects of intensive management on productivity (Tippin, 1978; Leaf, 1979 and Mann, 1980). Most of the deleterious effects of intensive forest management are associated with reductions in soil nutrient reserves or with the ability of the system to effectively cycle nutrients (Pritchett and Wells, 1978; Wells and Jorgensen, 1979; Pritchett, 1980) and with harm to the physical properties of the soil (Campbell, 1973; Haines et al., 1975; Nutter and Douglass, 1978; Greacen and Sands, 1980; Pritchett, 1980). Mechanical site preparation is used extensively in the southeast to eliminate logging slash, reduce competing vegetation and manipulate the site in an attempt to optimize survival and early height growth of planted seedlings (Duzan, 1980). There is no one site preparation prescription that is applicable to all areas. To improve their effectiveness and cost efficiency, site preparation prescriptions must be site specific. Social and environmental factors must also be considered (Balmer et_ al., 1976). Excessive soil disturbance during site preparation is a major factor influencing productivity declines (Pritchett, 1981). These same disturbances may also substantially increase sediment concentrations in stream water thus degrading water quality (Stone et_ al., 1978). The Federal Water Pollution Act (PL ) has classified harvesting and site preparation activities as non-point sources of pollution. As such, it is required by law to control discharges from forest land using "best management practices" (Rey, 1980). In light of these two factors, several research efforts in the southeast are actively investigating the effects of harvesting and site preparation. The small watershed technique has been used at Coweeta Hydrologic Laboratory since the early thirties to evaluate the effects of management practices on the timing, quantity and quality of streamflow from forested catchments (Douglass and Swi, 1977). Streamflow changes due to cutting and vegetation changes have been quantified and predictive equations developed for forested catchments subject to disturbance (Douglass and Swi, 1977). The current research effort at Coweeta emphasizes the effects of forest practices on stream water quality and nutrient cycling (Douglass and Swi, 1977). The U.S. Forest Service also maintains a hydrologic lab on the Coastal Plain at Oxford, Mississippi. The effects of intensive forest management practices on the upper Coastal Plain are being evaluated. It has been found that practices such as chopping, shearing, windrowing and bedding increase sediment losses. However, these losses tend to diminish aer the first year (Beasley, 1979). Sediments were also shown to be an important factor in the export of nitrogen from forested watersheds. Sediment-phase losses were found to equal aqueous-phase (dissolved) losses (Schrieber e al., 1980). A cooperative project between the University of Florida, the U.S. Forest Service and forest industry was installed to evaluate the effects of intensive management on the slash pine (Pinus elliotti) ecosystem of the lower Coastal Plain (Swindel e _!_., 1981). The Intensive Management Practices Assessment Center (IMPAC) has used paired watersheds to demonstrate increased water yield following harvesting and site preparation. Water quality changes, although variable, tend to increase with the level of site disturbance (Swindel et_ al., 1981). The effects of clearcutting and regenerating a southern Piedmont forest have been studied recently by Hewlett (1979). Results from this study indicate an increase in water yield following clearcutting and site preparation. However, large increases in nutrient export and sediment load in stream water were not reported. A site preparation study has recently been established by the Southern Regional Forest Center. This is a study designed to evaluate the effects of intensive management practices on loblolly pine (Pinus taeda) growth..i/ Sites have been selected on both the Piedmont and the Coastal Plain in an effort to provide basic information on the effects of intensive management on soil properties and nutrient cycling throughout the range of loblolly pine. Watershed research at the Reynolds Homestead Research Center is a cooperative project between the Department of Forestry at Virginia Tech, Champion International Corporation and the U.S. Forest Service. The objective of the project is to quantify the changes associated with clearcut harvesting and site preparation on the Virginia Piedmont. Specific emphasis is placed on 1) seedling survival and growth, 2) nutrient dynamics, 3) soil erosion and compaction, ) stream water quality and 5) organic matter transformations. This report presents an overview of the study site, treatments, methods, and preliminary results on the effects of harvesting and site preparation on stormflow and soil solution nutrient concentrations. MATERIALS AND METHODS 3/ Larry Morris, Personal communication. The Reynolds Homestead Research Center is located on the Piedmont in Patrick County, Virginia (fig. 1). The land use history of the Reynolds Homestead is typical of much of the southern Piedmont. Abusive agricultural practices associated with the production of tobacco caused severe erosion that was accompanied by substantial declines in productivity. Much of the eroded agricultural -69-

3 THE SOUTHERN PIEDMONT COUNTY BOUNDARIES SHOWN Afii Cl From Trimble. 197 Figure 1. Location of the Reynolds Homestead in relation to the Southern Piedmont. land was eventually abandoned and has since grown into low quality mixed stands of pine and hardwoods. In the summer of 1980, four small forested watersheds drained by ephemeral streams were selected for study. Watersheds 1 and 2 are approximately acres each, watershed 3 is approximately 8 acres and watershed is approximately 9 acres. Both the overstory and understory vegetation in each watershed were characterized. Overstory trees were measured using variable radius plots with a sampling intensity of one point per acre. The understory vegetation was sampled using the line transect method. The four watersheds were equipped with 1-foot H flumes to measure runoff (Douglass and Swi, 1977). A plywood trough 8 feet long, 27 inches wide and 19 inches deep served as a sediment trap and approach section to the flume. Stage height was measured by a strip chart recorder at a stilling well connected to the flume by rubber tubing. The volume of flow was calculated for each runoff event. A 2-foot diameter Coshocton wheel mounted below each flume collected approximately 0.5% of the flow. The Coshocton wheel was connected to a plastic barrel where the runoff was stored prior t:o sampling. When a large volume of flow was anticipated, a 10:1 sample splitter was placed between the Coshocton wheel and the plastic barrels which, reduced the stored sample to about 0.05% of i. lie total flow. Aer each event, the slormflow diverted to the plastic barrel wus sampled. Sediment was determined gravimetrically aer filtration through 0.2 micron fiberglass filter paper. The samples were analyzed for K, Ca, Mg, conductivity, ;nu'. p!! using the si.'indard methods employed in the Fores I Soils/Tree Nutrition lab at Virginia Tech. N)!, -N, NO. -N PO.-P were <UM rrmfned nl I he Virginia Tech Water Quality Lab using the methods described by Smolen et jd. (1978). Total N was determined by Kjeldahl digestion. Following a one year calibration period, three of the four watersheds were commercially clearcut. Conventional chainsaw felling and yarding with rubber tired skidders was used to harvest the timber. The harvesting operation was completed in October In late fall, 1981, soil solution lysimeters were installed at two depths, 6 and 12 inches, at ten random locations in each watershed. Soil solution samples were collected biweekly. NH^-N, N03-N, PO^-P, K, Ca, Mg, ph and conductivity were determined on the soil solution samples using the same analytic techniques as employed with the stream water samples. Soil moisture and temperature were also determined at biweekly intervals. Three separate site preparation prescriptions, representing three levels of intensity, were applied to the clearcut watersheds in July, The intensity of each prescription was classified on the basis of the amount of disturbance to the forest floor and residual biomass. Watershed 1, the uncut control, was not site prepared. It remains an undisturbed control. Watershed 2 was subjected to the least intensive treatment, chop and burn. A Harden double drum chopper weighing approximately 2,000 Ibs was pulled over the area by a Caterpillar D-7G tractor. The residual standing trees were knocked down and the smaller diameter material cut into pieces. Two months aer chopping, in September, 1982, the area was broadcast burned. The end result of this treatment was that the forest floor remained essentially intact and, except for elements volatized by the fire (primarily N), the nutrients present in the slash remained on the site distributed over the area in the ash. These nutrients were readily available and could rapidly move in the nutrient cycle. An intermediate level of site preparation intensity was applied to Watershed 3. The site preparation prescription consisted of the sheardisk, 1-pass operation. In a single jass over the site, the residual material was sheared and the forest floor was turned into the mineral soil. The results of this treatment differ from those of the chop and burn in that 1) the forest floor is disturbed and 2) although all the nutrients in the slash remain on the site, they are tied up in the residual material and are released to the active nutrient cycle at a much slower rate. The most intensive treatment was applied to watershed. This area was sheared, piled and disked in three separate passes with a Caterpillar D-7G. Windrows were located either on the contour or In erosion ditches and were burned two months aer site preparation. In this treatment, the -70-

4 nutrients contained in the slash were localized at the sites of the burned windrows. They are, for the most part, not available to the majority of trees in the next rotation. Following site preparation, sediment traps were constructed in each of the prepared watersheds to measure downslope soil movement. The sediment traps will be used to validate soil erosion losses from each site as predicted by the Universal Soil Loss Equation (Dissmeyer and Foster, 1980). Each of the site prepared watersheds will be planted with loblolly pine in the spring of Survival and growth will be measured periodically. Growth data will be correlated with results from the nutrient dynamics portion of the study to evaluate the impact of the three levels of site preparation on both short-and long-term site productivity. RESULTS AND DISCUSSION Site Characterization The principal soil mapping units in the study watersheds were: Watershed 1 Watershed 2 Watershed 3 Watershed Cecil Fine Sandy Loam, Cecil Clay Loam, Appling Fine Sandy Loam Hayesville Cobbly Loam, Hayesville Fine Sandy Loam, Cecil Fine Sandy Loam Cecil Fine Sandy Loam Cecil Clay Loam, Cecil Fine Sandy Loam, Appling Fine Sandy Loam Selected soil physical and chemical properties are presented in Table 1. A summary stand table of the overstory vegetation is presented in Table 2. Site Index data Js presented In Table 3, and the understory vegetation characterization data Is presented in Table. The soils of the four watersheds are derived from similar parent material and are quite similar. The major differences are in the depth of the A horizon, which is due to differential erosion. The vegetation on the watersheds was quite different. Pine dominated the overstory in watershed 2. The species composition in watersheds 1 and was more evenly distributed between pine and hardwoods. Watershed 3 was dominated by hardwoods. Differences in vegetation and topsoil depth can be traced to the past land use pattern of the individual watersheds and contributes to the inherent watershed differences. Clearcutting Effects The drought that occurred during 1980 and 1981 severely affected runoff from the gauged watersheds. The relative scarcity of streamflow data for the first half of 1981 (Table 5) can be attributed to the drought. Overall sediment concentrations in stormflow from the clearcut watersheds are greater than concentrations in the undisturbed watersheds. Most of the sediment in streamwater from the clearcut watersheds is associated with the construction of roads and landings in the upper parts of the drainage basin. Very little soil disturbance was observed in other areas of the clearcut. Nutrient concentrations, although variable, were generally greater in stormflow originating on Table 1. Selected soil properties for research watersheds at the Reynolds Homestead Research Center, Patrick County, Virginia. Watershed Site Preparation Prescription Soil To Be Applied Horizon Chop and Burn Shear-disk (1 pass) Shear, rake-pile, disk (3 pass) A B A B A B A B Depth (cm) BD OM PH K (g/cc) (%) Ca Mg (ppm) 1 / Double acid (0.05N HC N H 2 SO^) extraction. -71-

5 Table 2. Summary stand table of research watersheds at the Reynolds Homestead Research Center, Patrick County, Virginia. Watershed Site Preparation Prescription to be Applied Chop and burn Shear-disk (1 pass) Shear, rakepile, disk (3 pass) Va. Pine Other-^- S.W Oak!/ Tulip Poplar (trees/ Other^-/ H.W. \ Total S.W Total H.W Total 1, Species include white pine, Table-Mountain pine, Pitch pine and Eastern red cedar. I/ Species include white oak, northern red oak, chestnut oak and scarlet oak 3/ Species include black gum, sourwood, red maple, beech, green ash, black cherry, dogwood and black locust. the clearcut watersheds (Table 5). Both NH^-N and NC^-N concentrations are greater in stream water from the clearcut watersheds. It is interesting to note that NOj-N levels in streamwater from both the clearcut and control watersheds are greater than NH^-N levels. The relationship between streamflow PO^-P concentrations in the clearcut and control watersheds varies from month to month, although, on the average, higher concentrations do occur in streamflow from the clearcut watersheds. However, levels from both areas are quite low. K concentrations are higher in streamflow from the clearcut watersheds. Similar results were observed for Ca and Mg concentrations. The effect of clearcut harvesting on soil solution nutrient concentrations can be seen In Table 6. NH^-N and N03~N concentrations in samples from the clearcut watersheds were significantly greater than the control. In addition, NO^-N levels tend to be higher than NH^-N in the clearcut watersheds. The reverse occurs in the control watershed. This indicates that nitrification is a significant factor in the disturbed watersheds, but not In the control. Similar results have been observed by Likens, et al. (1970). PO^-P concentrations in soil solution from the clearcut watersheds were significantly greater than the PO^-P concentrations in soil solution from the control watershed. However, as with the streamwater samples, PO^-P concentrations from both Table 3. Site indices for selected species on research watersheds at the Reynolds Homestead Research Center, Patrick County, Virginia. Site Index^/ Watershed Prescription to be Applied Virginia Pine White Pine Tulip Poplar Chop and burn 66 3 Shear-disk (1 pass) Shear, rake-pile, disk (3 pass) Site index base age 50 years. -72-

6 Table. Understory vegetation characterization of research watersheds at the Reynolds Homestead Research Center, Patrick County, Virginia. Watershed Site Preparation Prescription to be Applied Chop and burn Shear-disk (1 pass) Shear, rake-pil disk (3 pass) e, Soil Grass Forb Species Vine Shrub H.W. dominance) A' Pine '3 Dominance is calculated as : dominance total intercept length of = species A total transect length x Table 5. Monthly and cummulative averages of selected research watersheds prior to site preparation. stream water properties from Date Feb Mar Apr May June o July Aug Sept Oct Nov Dec Jan Feb Mar o A P r - 1 May June July Sediment., NH-N C.C.- (g/ml) C.C N0 3 -N PO/,-P K C.C. C.C. C.C. ( ppni) Oil 2. 2 A Q umulative Average Clear cut. No run off event occurred during this month. -73-

7 Table 6. Mean soil solution values for research watersheds at the Reynolds Homestead Research Center, Patric County, Virginia, as affected by clearcut harvesting. Treatment NH^-N N0 3 -N PO-P K r(pp m) Ca Mg Conductivity (mmhos) PH Clearcut O.OSa^ 0.22b O.Ola 0.60b 0.008a 0.016a 1.96a 2.6b 2.09a 3. 19b 0.92a 1.30b 25..9a 37,.5b 5.3a 5.3a the clearcut and the control watersheds are quite low. This is probably due to the low level of water soluble P found in most Piedmont soils. Conductivity and cation concentrations in soil solution were also significantly higher in the clearcut watersheds (Table 6). These higher levels were probably responsible for the increased levels of nutrients in the stream water. Effects of Site Preparation Unfortunately, no runoff events have occurred since site preparation. Thus, it was not possible to determine the effects of site preparation on any stream water parameters. Soil solution data for the first three months since site preparation is presented in Table 7. Although there was a trend towards higher levels of NH^-N in the site prepared watersheds, there were no significant differences. A similar trend with NC>3-N values did indicate a significantly higher concentration of NO-j-N in the soil solution of the most intensive treatment. In the two more intensive treatments, the shear, pile, disk and the shear-disk, NC^-N levels were greater than NH^-N levels. In the chop and burn and control watersheds the reverse occurred. This seems to indicate that nitrification was an important process in the more intensive treatments, but not in the undisturbed and minimally disturbed areas. P0~P values were not significantly different among any of the site preparation treatments or the control. The low level of readily available P in Piedmont soils was again demonstrated by the low concentrations of P in soil solution. Conductivity and cation values In soil solution tended to increase with increasing Intensity of site preparation. K levels in each of the site prepared watersheds were greater than the control. Ca, Mg and conductivity values paralleled those of K, but only the most intensive treatment was actually significantly greater. CONCLUSIONS Preliminary results from this study showed that clearcutting and site preparation increased levels of nutrients in soil solution. This may be due to a combination of increased organic matter mineralization and a. decrease in nutrient uptake by vegetation. Clearcutting was also found to increase the nutrient concentration and sediment load of stormflow. The increased level of nutrients in Table 7. Mean soil solution values for research watersheds at the Reynolds Homes tea' Research Center, Patrick County, Virginia, as affected by site preparation. Site Preparation Prescription Chop and burn NH-N 0.57^ 0.66a 0.95a Shear-disk (1 pass) Shear, rake-pile 0.86a disk (3 pass) N0 3 -N 0.18a 0.32a 1.78a PO~ P f-~ (PIT 0. OlOa a a K 2.59a 5.OOb 5.3b Ca 1.31a 2.33a 3.1a Mg 1.36a 1.37a 1.77a Conductivity r i \ 27. 5a 58. 5a 67. 9a PH 5.26ab 5.25a 5.57ba.75b 0.012a 5.56b 7.92b 2.8b 10.8b 5.66c \J Values in a column with the same letter are not significantly different (< = 0.05), -7-

8 stream water draining from the clearcut watersheds is probably related to the higher levels of nutrients in soil solution in the clearcut areas. Increased sediment loads in streamflow from the clearcut watersheds were probably associated with the construction of roads and landings during the harvesting operation. The higher levels of both sediments and nutrients in streamflow originating on the clearcut watersheds may detrimentally affect downstream water quality. NOj-N levels were greater than NH/-N levels in the disturbed watersheds. Nitrification appeared to be an improtant process in the disturbed areas. This can have important consequences because of the great mobility of the nitrate anion. N03-N leached from the active rooting zone is no longer available to the tree crop. There are also potential health hazards associated with high nitrate levels in drinking water. Since forestry operations are classified as non-point sources of pollution, these potential impacts of intensive management should be of concern to forest managers, particularly since they may also be related to potential declines in long term site productivity. ACKNOWLEDGMENTS The authors are grateful for the assistance provided by Champion International's site preparation and equipment personnel in the installation of this study. The assistance of Jackson R. Bird, Stephen Schoenholtz, Douglas Lantagne, and John Torbert is also appreciated. LITERATURE CITED Balmer, W.E., H.L. Williston, G.E. Dissmeyer and C. Pierce Site preparation - why and how? For. Mgt. Bull. SE Area State and Private Forestry USDA For. Ser., 8 p. Beasley, R.S Intensive site preparation and sediment losses on steep watersheds in the Gulf Coastal Plain. Soil Sci. Soc. Am. J. 3: Campbell, E.G The impact of timber harvesting and site preparation on selected soil conditions and plant growth. Ph.D. dissertation, University of Georgia, 65 p. Dissmeyer, G.E. and G.R. Foster A guide for predicting sheet and rill erosion on forest land. USDA For. Ser. State and Private Forestry. SE Area Tech. Public. SA-TP11, 0 p. Douglass, J.E. and W.T. Swank Streamflow modification through management of eastern forests. USDA For. Ser. Res. Paper SE 9, 15 p. Douglass, J.E. and L.W. Swi Forest service studies of soil and nutrient losses caused by roads, logging, mechanical site preparation and prescribed burning in the southeast, p In Correll, D.L. (ed.) Watershed Research in Eastern North America. A Workshop to Compare Results. Smithsonian Institution, Edgewater, Md. Duzan, H.W Site preparation techniques for artificial regeneration, p _In Mann, J.W. (ed.) Proceedings of a Seminar on Site Preparation and Regeneration Management. Forestry Harvesting and Training Center. Clemson, SC. Greacen, E.L. and R. Sands Compaction of forest soils. A review. Aust. J. Soil Res. 18: Haines, L.W., T.E. Maki and S.G. Sanderford The effect of mechanical site preparation treatments on soil productivity and tree (Pinus taeda L. and Pinus elliotti var. elliottii) growth, p J_n Bernier, B. and C.H. Winget (eds.) Forest Soils and Land Management. Les Presses de 1'Universiti' Laval, Quebec. Hewlett, J.D Forest water quality: An experiment in harvesting and regenerating Piedmont forest School of Forest Resources, Univ. of Georgia. Athens, Georgia. 22 p. Knight, H.A The southern pine is losing ground. Ala. For. Prod. 20(9):-6. Leaf, A.L. (ed.) Proceedings - impact of intensive harvesting on forest nutrient cycling. College of Environmental Science and Forestry, State University of New York, Syracuse, NY. Likens, G.E., F.H. Bormann, N.M. Johnson, D.W. Fisher and R.S. Pierce Effects of forest cutting and herbicide treatment on nutrient budgets in the Hubbard Brook watershed-ecosystem. Ecol Monogr. 0:23-7. Mann, J.W. (ed.) Proceedings of a seminar on sit tion and regeneration management Harvesting and Training Center. Nutter, W.L. and J.E. Douglass Consequences of harvesting preparation in the Piedmonr, p. and site In Tippin T. (ed.) Proceedings: A Symposium on Principles of Maintaining Productivity on Prepared Sites. Atlanta, Georgia. Pritchett, W.L Soil amelioration: physical and chemical properties, p I_n Mann, J.W. (ed.) Proceedings of a Seminar on Site Preparation and Regeneration Management. Forestry Harvesting and Training Center. Clemson, SC. Pritchett, W.L Site preparation in the coastal flatwoods IMPAC Report 6(7). University of Florida. 21 p. prepara- Forestry Clemson, SC. -75-

9 Pritchett, W.L. and C.G. Wells Harvesting and site preparation increase nutrient mobilization, p In Tippin, T. (ed.) Proceedings: A Symposium on Principles of Maintaining Productivity on Prepared Sites. Atlanta, Georgia. Rey, M The effect of the clean water act on forestry practices in U.S. forestry and water quality: what course for the 80'si Water Pollution Federation. Richmond, VA. Schreiber, J.D., P.D. Duffy and B.C. McClurkin Aqueous- and sediment-phase nitrogen yields from five southern pine watersheds. Soil Sci. Soc. Am. J. : Smolen, M.D., J.G. Bruce, Jr. and V.L. Church A labor efficient water analysis system with computerized data handling, p In National Conference on Quality Assurance of Environmental Measurements. Information Transfer, Inc., Silver Springs, MD. Southern Forest Resource Analysis Committee The South's third forest. How can it meet future demands? Southern For. Resour. Anal. Comm. 11 p. Stone, E.L., W.T. Swank and J.W. Hornbeck Impacts of timber harvest and regeneration systems on stream flow and soils in the eastern deciduous region, p In Proc. Fih North Am. Forest Soils Conf. Colorado State University. Swindel, B.F., E.T. Sullivan, W.R. Marion, L.D. Harris, L.A. Morris, W.L. Pritchett, L.F. Conde and H. Riekerk Multi-resource effects of harvest, site Preparation and planting in pine flatwoods. IMPAC Report 6(6). Univ. of Florida, Gainesville, FL. Switzer, G.L. and L.E. Nelson Maintenance of productivity under short rotations, p In Int. Symp. on Forest Fertilization. OFAO/IUFRO, Paris. Tippin, T. (ed.) Proceedings: a symposium on principles of maintaining productivity on prepared sites. Southeastern Area State and Private Forestry, Atlanta, Georgia, 171 p. USDA Forest Service The outlook for timber in the United States. Forest Resources Report No. 20, 367 p. Wells, C.G. and J.R. Jorgensen Effects of intensive harvesting on nutrient supply and sustained productivity, p In Leaf, A.L. (ed.) Impact of Intensive Harvesting on Forest Nutrient Cycling. Syracuse, NY. Whyte, A.G.D Productivity of first and second crops of Pinus radiata on the Moutere gravel soils of Nelson. New Zealand J. Forestry 18: Will, G.M. and R. Ballard Radiata pine - soil degrader or improver? New Zealand J. For. 21: