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ABSTRACT:Ecosystem response to site restoration depends in part on the physical, chemical, and biological properties of soils. Soil properties are influenced by the factors and processes of soil formation that determine soil profile characteristics and pedogenic pathways for soils. Loss of integrity of the original soil profiles or disruption of a past pedogenic pathway from site disturbance may limit the success of restoration if assessment is based on comparisons to previous ecosystems or mature reference systems. New profile characteristics and a pedogenic pathway will emerge over time if materials are used to construct soil profiles or if topsoil or organic matter amendments are added to enhance ecosystem development during site restoration. Ecosystem restoration should include the following pedogenic evaluation of soils: 1) the integrity of existing soil profiles of a degraded site; 2) the soil types (based on soil orders) and past pedogenic pathways for sites of intact soil profiles or sites that require only surface horizon modification; 3) the relative contributions of soil forming factors and processes on future pedogenesis; 4) the conditions that promote or hinder horizon development; and 5) predictions of pedogenic pathways and potential soil types after site restoration. Understanding pedogenesis as a component of ecosystem restoration will improve our understanding of how soils influence ecosystem development, as well as our ability to predict potential success of ecosystem restoration.

Abstract:Wetland restoration projects are often evaluated for success or failure by comparing attributes of restored ecosystems to undisturbed reference ecosystems. This method of evaluation has several flaws, including site-specific responses of restored ecosystems to topographic and geomorphic changes during degradation and restoration, the substantial differences in structure and function of early (restored) and mature (reference) ecosystems, and the inherent variability that exists for ecosystems that may not be represented in reference systems. We need a better framework for evaluating restoration success. Success could be demonstrated by using ecosystem attributes that indicate ecosystem integrity and maturation over time, such as: stable landforms, native plant community development, internal carbon and nutrient storage and cycling, connectivity within the broader landscape, ecosystem heterogeneity, and increasing complexity in species and community diversity. A more realistic role for reference areas in wetland restoration is useful information on structural and functional attributes of ecosystems and an indication of the natural variability that exists in ecosystems that we hope to emulate. Ultimately though, success in wetland restoration depends on our ability to establish conditions that promote ecosystem maturation and integrity and reference systems may be of limited value to evaluate this success.

A study was conducted to determine if surveys of hydric soils could be used as a historic baseline to estimate wetland losses. Soils were digitized from county soil surveys and wetlands were digitized from National Wetlands Inventory (NWI) maps for two adjacent coastal counties in North Carolina. The two counties were located on the lower Atlantic Coastal Plain and have extensive areas of hydric soils, as much as 96% of the land surface area. Using hydric soils from soil surveys and wetlands from NWI maps, wetland losses since settlement were calculated to be 65% for Washington County and 38% for Tyrrell County. The NWI wetlands were compared to a mid-1950s wetlands survey to determine recent wetland losses. A large percentage of the wetland losses occurred between 1950 and 1980 for Washington County compard to Tyrrell County. Wetland losses for both counties occurred primarily on mineral hydric soils and the current wetlands distribution corresponded well with the distribution of organic soils.

Soil chemistry gradients exist in wetlands but information on the spatial variability of wetland soil properties is limited. Soils were collected from a small, depressional wetland (Carolina bay) in South Carolina to determine spatial patterns along an elevational gradient. The bay was divided into four quadrants and a transect was established in each quadrant. Plots were sampled at every 10‐cm rise in elevation along the four transects. Samples from the A and B horizons were analyzed for soil texture, organic carbon (OC), pH, cation‐exchange capacity (CEC), and exchangeable Ca, Mg, and K. Significant difference were noted for OC, clay content, CEC, and base saturation for the A horizon across the elevational gradient. The OC content of the A horizon decreased from 4.7% in the center of the bay to 2.7% near the rim. The CEC decreased from 26.0 cmolckg−1in the center to 13.9 cmolckg−1near the rim. Significant differences also were observed for pH, OC, CEC, sand, silt, clay, exchangeable Mg, Ca, and base saturation among the four transects. In the B horizon, there were no significant differences for any parameter across the elevational gradient, or among the four transects. The clay content of the B horizon was about 20%, compared with <10% in the A horizon. The differences in soil parameters in the A horizon may be a reflection of vegetation patterns or hydrology of the bay. Sampling protocol for soils of depressional wetlands may require an evaluation of elevation, hydrology, and vegetation patterns to determine spatial patterns of nutrient cycling.

Multiple stable isotopes were used to determine the effectiveness of distinguishing among several dominant riparian species and aquatic macrophytes both spatially (three sites) and temporally (three seasons) along an 8-km reach of a blackwater stream. The differences in isotopic composition were used to assess contributions of various organic matter sources to the detrital pool of the stream. Samples of riparian and aquatic macrophyte vegetation and detritus were collected at three times to represent early leaf-out (April), mid-summer (August), and just prior to abscission (October). Each sample was analyzed for stable isotopes of carbon d13C, nitrogen d15N, and sulfur d34S Within a site and sampling date, d13C-values were significantly different among certain riparian species and detritus samples. Species differences persisted between seasons. d34S values were the most variable of the three elements examined although they remained fairly constant through time within each species and site. The results suggest that temporal changes in isotopic compositions of riparian species and aquatic macrophytes are site-specific. Discriminant analysis dissimilarity plots (based on all three isotopes) demonstrated that the contribution of species to the detrital pool depended on the site and season. At the upper site, detritus was isotopically most similar to Quercus laurifolia and Sparganium americanum in April, and the aquatic macrophytes (S. americanum and Potamogeton spp.) in August and October. At the middle site, detritus was most similar to Carpinus caroliniana and Q. nigra in April but no single source was similar to detritus in August or October. At the lower site, detritus was most similar to Taxodium distichum for all three seasons.

This paper reports the results of studies aimed at improved corrective fertilizer recommendations. The studies were conducted on soils from field plots, using a two-step alternative methodology involving exchangeable K and Bray-1 P. Computed exchangeable K and Bray-1 P at various rates added, based on quick-test recovery of added K and P after 2-h equilibration (one-step methodology), were highly associated with values obtained after 2 months' laboratory equilibration and with values obtained after field equilibration (r2 ranged from 0.960 to 0.994). From the above soil test values, the amounts of fertilizer K and P to reach sufficiency levels of soil-available K and P for maximum yields could be calculated. These quick-test values were converted to actual amounts for longer periods of equlibration by using regression analysis of data from laboratory and field equilibrations (two-step methodology). Exchangeable K and Bray-1 P were associated both with tissue contents of K and P and with corn and soybean yields, except where dry weather or no-tillage culture adversely affected the relationship.