Stephen H. Schoenholtz

A Review of Chemical and Physical Properties as Indicators of Forest Soil Quality: Challenges and Opportunities

Foresters have always relied on a knowledge of chemical and physical properties of soils to assess capacity of sites to support productive forests. Recently, the need for assessing soil properties has expanded because of growing public interest in determining consequences of management practices on the quality of soil relative to sustainability of forest ecosystem functions in addition to plant productivity. The concept of soil quality includes assessment of soil properties and processes as they relate to ability of soil to function effectively as a component of a healthy ecosystem. Specific functions and subsequent values provided by forest ecosystems are variable and rely on numerous soil physical, chemical, and biological properties and processes, which can differ across spatial and temporal scales. Choice of a standard set of specific properties as indicators of soil quality can be complex and will vary among forest systems and management objectives. Indices of forest soil quality which incorporate soil chemical, physical, and biological properties will be most readily adopted if they are sensitive to management-induced changes, easily measured, relevant across sites or over time, inexpensive, closely linked to measurement of desired values, and adaptable for specific ecosystems. This paper traces development of the concept of soil quality, explores use of soil chemical and physical properties as determinants of forest soil quality, and presents challenges and opportunities for forest soil scientists to play a relevant role in assessment and advancement of sustainable forest management by developing the concept of soil quality as an indicator of sustainability.

Response of radiata pine forests to residue management and fertilisation across a fertility gradient in New Zealand

New Zealand law requires sustainable forest management. International definitions of sustainability typically include maintaining the productive capacity of forest soils, and decision tools are needed for managing harvesting and site preparation practices. Trials were established between 1986 and 1994 in different physiographic regions of New Zealand to determine the effects of management on the second-rotation performance of Pinus radiata. Main harvesting and residue treatments at three North Island sites include: whole-tree harvest plus forest floor removal, whole-tree harvest, and stem-only harvest retaining a single layer of slash. These treatments were installed in a random block split-plot design (with and without fertiliser). Additional treatments were added at specific sites (e.g., double slash addition at Woodhill; topsoil removal at Tarawera) to test hypotheses that harvesting intensity is negatively correlated with second-rotation growth, that inadequate nutrition is the reason for the negative correlation, and that fertiliser additions can compensate for the negative impact of harvesting on nutrition. Stands were thinned-to-waste to reduce stocking by 50% at Woodhill (age 7 years), Tarawera and Kinleith (age 5 years). On recent coastal sand dunes at Woodhill, foliar analyses suggest that nutrient availability to trees of N, P, K, B, Mn, and Zn were reduced during critical periods of stand establishment by forest floor removal, and improved by retention of thinning slash. Diameter at 5 years declined as forest floor C:N ratio increased. Diameter after 11 years was reduced by forest floor removal, and positively related with residue retention. On approximately 100-year-old basaltic tephra gravel at Tarawera, foliar concentrations of K and B were positively related with slash and soil nutrient retention, however, the effect of harvest removals on tree nutrition and growth was substantially less than observed on recent sand dunes due to greater native fertility of basaltic gravel. Forest floor C:N ratio at Tarawera explained less variation in tree growth than at Woodhill. On the N-rich Taupo sandy loam of Kinleith Forest, there was no correlation between forest floor C:N ratio and tree diameter to age 5 years. Fertiliser additions have increased tree diameter at all sites, and can ameliorate harvesting-related reductions in growth. However, fertiliser additions caused significant reductions in foliar concentrations of most nutrients studied except N. These trials have been useful for identifying the benefits of residue retention among sites with varying levels of native fertility. Based on the results of this study, we recommend organic matter retention during harvest and site preparation on N-deficient sites such as Pinaki Typic Sandy Recent Soil.

AFFORESTATION OF BOTTOMLAND HARDWOODS IN THE LOWER MISSISSIPPI ALLUVIAL VALLEY: STATUS AND TRENDS

The Lower Mississippi Alluvial Valley (LMAV) originally supported at least 10 million ha of bottomland hardwood (BLH) forests. Many of these forests were wetlands and provided a diversity of values that were not recognized fully until at least one-half of the original forested area had been converted primarily to row-crop agriculture. Efforts to restore these forests have expanded in proportion to growing recognition of their unique values. This paper provides a summary resulting from a survey of BLH afforestation by all agencies and private entities in Arkansas, Louisiana, and Mississippi, the three states in the LMAV with the most restoration activity and, more specifically, by the U.S. Fish and Wildlife Service, the U.S.D.A. Natural Resources Conservation Service, and state wildlife management agencies, the three entities responsible for approximately 95% of the afforestation in this region. There is a promising trend in the annual increase of BLH afforestation across the LMAV. Approximately 71,000 ha have been planted with BLH species through 1998; however, this represents <1% of the BLH forests that have been lost, and afforestation does not ensure restoration of all ecological functions. No clear choice between planting stocks (bareroot seedlings or direct seeding) or among planting seasons (Fall, Winter, Spring, or Summer) is prevalent among those involved in BLH afforestation. Much of the early afforestation used oaks (Quercus spp.) to accelerate replacement of mast-bearing species. Recently, mixtures of species have been incorporated into afforestation regimes. More light-seeded species and a more diverse component of oak species have been planted to mimic a more natural regeneration process. Successful widescale afforestation is a critical link in restoration of functional BLH ecosystems in this region.

Initial responses of woody vegetation, water quality, and soils to harvesting intensity in a Texas bottomland hardwood ecosystem

Sustainable management of bottomland hardwood forest ecosystems requires a knowledge of responses to management impacts, including timber harvesting. The effects of clearcutting and partial cutting on woody vegetation regeneration dynamics, surface and groundwater quality, soil physical properties, and soil respiration were tested in a bottomland hardwood ecosystem in southeastern Texas, USA, through comparison with non-cut control areas. Overstory removal only slightly affected composition of woody vegetation regeneration 1 year after harvesting compared with pre-harvest composition. Initial composition in both cutting treatments appeared to be the strongest determinant of post-harvest composition, at least for the first year after harvesting. There were few significant differences in groundwater properties when harvesting treatments were compared with control areas during a 17-month period following harvest. Turbidity, temperature, electrical conductivity, dissolved O2, NH4-N, NO3-N, and PO4-P of streamwater did not vary significantly among treatments. Slight decreases in total and macroporosity were observed in association with higher bulk densities at 0–5 cm depth in the clearcut and partial cut treatments. Saturated hydraulic conductivity values did not decline significantly with treatment intensity. No significant differences among treatments in measured soil physical properties were observed at 5–10 cm depth. Although in situ soil respiration increased with harvest intensity, treatment had no significant effect on mineral soil respiration. In summary, most variables showed only slight response to harvesting, thereby indicating that harvesting practices can be conducted with minimal initial impacts on measured response variables.

Measuring the environmental effects of converting cropland to short-rotation woody crops: a research approach

Abstract Conversion of cropland to short-rotation woody biomass crops (SRWC) has received increasing interest as biomass utilization technologies have improved and concerns for effects of fossil fuel emissions on global climate have developed. Effects of this conversion on erosion, hydrology, water quality and soil productivity may be significant. A large cooperative research project began in the spring of 1995 at three sites representative of the lower Tennessee Valley to compare the environmental effects of growing traditional row crops with the production of SRWCs over 3- to 5-year rotations. This paper presents the research approach be used to evaluate these effects and a few preliminary results from the initial 3 months of the study. Small watersheds cultivated in row crops: corn ( Zea mays L.) or cotton ( Gossypium hirsutum L.), are being compared with small watersheds in tree crops: sycamore ( Platanus occidentalis L.), sweetgum ( Liquidambar styraciflua L.) or eastern cottonwood ( Populus deltoides Bartr.) with respect to: (1) erosion; (2) run-off quality (nutrients, pesticides) and quantity; (3) groundwater quality; (4) soil chemical changes (carbon, nutrients, pesticides); (5) soil physical changes (infiltration, bulk density, aggregate stability); (6) soil biological changes; and (7) wildlife populations. During the spring and summer of the first growing season, few differences in run-off quantity and erosion were observed between treatments. One exception was a tendency towards higher erosion under cotton than cottonwood. Larger differences are expected in later years as trees become established and a litter layer develops. At two sites during the first growing season, differences between row crops and SRWCs were observed in both the runoff and leaching of NO 3 -N, NH 4 -N, P, Ca, Mg and K in spring following fertilization of the row crops only at these two sites. Wildlife studies on small mammals and bird populations, as well as microfauna, are just getting under way.

The influence of flatworm predation on zooplankton inhabiting small ponds

Experiments were performed in 1977 to determine which large zooplankton in a series of high altitude ponds can be consumed by the predatory flatworm Mesostoma ehrenbergii. This predator consumes Daphnia at a high rate and the fairy shrimp Branchinecta at a low rate, but does not consume Diaptomus. Experiments were performed in 1978 and 1979 to determined the rate of predation on Daphnia in 30 liter tubs and to determine if predation rate is correlated with surface to volume ratio of experimental containers. There is a clear correlation between surface to volume ratio and predation rate. Determinations of Mesostoma and Daphnia densities were made in a series of eight high altitude ponds, and pond surface to volume ratios were determined. Examination of these parameters lends credence to the argument that Mesostoma predation affects Daphnia dynamics in some circumstances. The results suggest that benthic invertebrate predators may affect zooplankton dynamics, especially in shallow ponds.

Recovery status of a tupelo-cypress wetland seven years after disturbance: silvicultural implications

Abstract Three disturbance treatments were imposed on a palustrine forested wetland ( Nyssa aquatica-Taxodium distichum ) located in southwestern Alabama in 1986: (i) clearcutting with helicopter log removal (HELI), (ii) HELI followed by rubber-tired skidder traffic simulation (SKID) and (iii) HELI followed by removal of all vegetation during the first two growing seasons via glyphosate herbicide application (GLYPH). After two growing seasons, it was hypothesized that eventual woody plant growth would be best in the HELI-treated areas, because SKID plots had reduced rates of water movement and soil aeration. However, measurements at stand age seven years indicate that SKID actually has greater total above-ground biomass (65979 kg/ha) than HELI (46748 kg/ha) and SKID plots have a higher proportion of the most desirable timber species ( Nyssa aquatica ). GLYPH areas resemble freshwater marshes, although the areas are being invaded by Salix nigra seedlings. All disturbance treatments have significant groundflora components that have increased sediment accumulation 70–175% relative to an undisturbed reference area. By age seven years, regrowth of vegetation has lowered the water table during the growing season but has had little effect on soil redox potential and pH. Our observations suggest that this wetland system is rapidly recovering from logging disturbance seven years ago.

An assessment of structural attributes and ecosystem function in restored Virginia coalfield streams

As human populations continue to grow, expanding energy needs enhance freshwater resource conservation challenges. Mining for coal has significantly altered the landscape in the United States’ Appalachian region, with significant negative effects on downstream water quality and ecosystem function. With recent policy changes concerning the impacts of coal mining on aquatic ecosystems, many coal companies choose to restore sections of stream located on older coal mining areas as mandated compensatory mitigation for mining-related stream disturbances. We assessed such mitigation using measures of both structure and function in restored and unrestored streams affected by surface mining operations. Macroinvertebrate assemblages in streams affected by older mining and recent restoration practices were rated as “stressed” and “severely stressed,” with streams varying from fair to optimal in terms of habitat. All streams were net heterotrophic with varying levels of ammonium uptake. No site differences were found for any measured physicochemical or functional variables, while invertebrate community metric scores were higher in unrestored streams. There were also no significant relationships found between structural and functional measurements in these streams. Principal components analysis implicated the importance of measuring physicochemical, structural, and functional variables in further analyses of restoration success. This study was unable to document pre-disturbance conditions, and as a result, we were unable to find evidence that restoration is currently having a significant effect on ecosystem processes within these systems. Further research is needed to understand the changes in ecosystem structure and function that come with time.

Effects of logging debris treatments on five-year development of competing vegetation and planted Douglas-fir

Although considerable research has focused on the influences of logging debris treatments on soil and forest regeneration responses, few studies have identified whether debris effects are mediated ...

Nitrate-nitrogen, land use/land cover, and soil drainage associations at multiple spatial scales.

Managing non-point-source pollution of water requires knowledge of land use/land cover (LULC) influences at altering watershed scales. To gain improved understanding of relationships among LULC, soil drainage, and dissolved nitrate-N dynamics within the Calapooia River Basin in western Oregon, we selected 44 watersheds ranging in size between 3 and 33 km(2) for monthly synoptic sampling of surface water quality between October 2003 and September 2004. Seasonal associations were examined between dissolved nitrate-N and proportion of woody vegetation or poorly drained soils at differing scales (10, 20, 30, 60, 90, 150, 300 m, and entire watershed), which we defined as influence zones (IZs), surrounding stream networks. Correlations between nitrate-N and proportion woody vegetation or poorly drained soil at each IZ were analyzed for differences using the Hotelling-Williams test. We observed negative correlations (r = -0.81 to -0.94) between nitrate-N and proportion of woody vegetation during winter and spring. Poorly drained soils had positive correlations (r = 0.63-0.87) with nitrate-N. Altering the scale of analysis significantly changed correlations between nitrate-N and woody vegetation, with IZs <150 m being stronger than the watershed scale during winter. However, absolute differences in correlation values were small, indicating minimal ecological consequence for significant differences among scales. In contrast, nitrate-N correlations with poorly drained soil were stronger at the watershed scale than the 10- through 90-m IZs during winter and spring, and absolute differences were sufficient to suggest that scale is ecologically important when determining associations between dissolved nitrate-N and poorly drained soils.