Long-Term Soil Productivity
The USDA Forest Service’s Long-Term Soil Productivity (LTSP) program began in 1989 in the Southern Research Station to address land managers’ concerns about the long-term consequences of soil disturbance on fundamental forest productivity. It eventually grew into a national program of the USDA Forest Service. Today, the LTSP program comprises more than 100 LTSP and affiliated sites and is the world’s largest research network addressing basic and applied science issues of forest management and sustained productivity. LTSP research also addresses short-term consequences of site and soil disturbance on forest productivity but the research mostly focuses on two key properties affecting a site’s long-term productive capacity---site organic matter and soil porosity, each of which is readily influenced by management. Studies range from applied growth and yield monitoring, through elucidating mechanisms controlling carbon capture above and below ground, to developing indices of soil quality practicable in monitoring.
Forest Service managers and researchers recognized that clear and objective definitions were significant and defined “land productivity” as the “carrying capacity of a site for vegetative growth.” They also recognized that soil properties are valuable as an independent basis for monitoring potential productivity. In 1987 a program of soil quality monitoring was based on the following rationale was adopted by the Watershed and Air Management division of National Forest Systems:
- Management practices create soil disturbances.
- Soil disturbances affect soil and site processes.
- Soil and site processes control site productivity.
Although monitoring soil and site processes directly is not feasible, monitoring can be based on measurable soil variables that either reflect (or are correlated with) important site processes. Key soil monitoring variables were identified that (1) had a known or presumed correlation with potential productivity, and (2) could be measured operationally within a reasonable degree of statistical confidence (e.g. ± 15% of the true site mean). Presumably, any appreciable change in a key soil monitoring variable suggests a change in the potential productivity of a site.
Soil disturbance effects on tree growth have been widely studied. The Missouri LTSP is designed to investigate the effects of organic matter removal and soil compaction on various aspects of the above- and below-ground Ozark forest ecosystem. The growth and development of planted red oak (Quercus rubra), white oak (Q. alba), and shortleaf pine (Pinus echinata) are being evaluated for different levels and combinations of organic matter removal and soil compaction and with and without vegetation control. Understory vegetation species type, abundance, and growth are being studied. Both micro-flora and micro-fauna in the study continue to be evaluated for type and abundance. At the Missouri site, shortleaf pine is taller and larger in diameter on compacted plots than on plots not compacted, but the opposite was true for red oak. Soil compaction had no significant effect on the diameter of white oak, but it increased its height. Height and diameter of white oak decreased with an increase in the amount of organic matter left on the site but the treatment had no effect on red oak or shortleaf pine. The regional biomass in only a few sites has shown a response to organic matter removal, but in many sites it has shown a response to soil compaction. We are cooperating with the University of Missouri, the Missouri Department of Conservation, and the North America LTSP Network.
Expected outcomes include a comprehensive examination of the long-term consequences of soil disturbance on fundamental forest productivity of Ozark forests and guidelines to minimize site productivity losses resulting from nutrient and porosity changesand to maximize gains associated with treatments in regenerating central hardwood forests.
Ponder, F., Jr. 2008. Nine-year response of hardwood understory to organic matter removal and soil compaction. Northern Journal of Applied Forestry 25:25-31.
Ponder, F., Jr.; Eivazi, Freida. 2008. Activities of five enzymes following soil disturbance and weed control in a Missouri forest. Journal of Environmental Monitoring & Restoration 5:68-76.
Page-Dumroese, D.S.; Jurgensen, M.F.; Tiarks, A.E.; Ponder, F., Jr.; Sanchez, F.G.; Fleming. R.L.; Kranabetter, J.M.; Powers, R.F.; Stone, D.M.;Elioff, J.D. ;Scott, D.A. 2006. Soil physical property changes at the North American Long-Term Soil Productivity study sites: 1 and 5 years after compaction. Canadian Journal of Forest Research 36: 551-564.
Fleming, R.L.; Powers, R.F.; Foster, N.W.; Kranabetter, J.M.; Scott, D.A.; Ponder, F. , Jr.; Berch, S.; Chapman, W.K.; Kabzems, R.D.; Ludovici, K.H.; Morris, D.M.; Page-Dumroese, D.S.; Sandborn, P.T.; Sanchez, F.G.; Stone, D.M.; Tiarks, A.E. 2006. Effects of organic matter removal, soil compaction and vegetation control on 5-year seedling performance: a regional comparison of Long-Term Productivity sites. Canadian Journal of Forest Research 36:529-550.
- Dan Dey, Project Leader/ Research Forester, US Forest Service, Northern Research Station
- Felix Ponder, Jr., Research Soil Scientist (deceased), US Forest Service, Northern Research Station
- Randy Jensen, Missouri Department of Conservation
- D. Andrew Scott, Research Soil Scientist, US Forest Service, Southern Research Station
- Robert Fleming, Canadian Forest Service
Last Modified: 03/06/2015