Influence of soil physicochemical properties on hydrology and restoration response in Carolina Bay wetlands.

Carolina Bays are shallow depression wetlands found in the southeast US that have been severely altered by human activity. The need to restore these complex and diverse systems is well established, but our understanding of basic wetland hydrological processes is limited, hence our ability to predict the need for and/or assess the effectiveness of bay restorations is hindered. Differing physicochemical properties of soils within bay interiors may control bay hydrology. However, previous efforts to establish relationships between soil characteristics and bay hydrology have been inconclusive and the question still remains as to why some bays are ponded throughout the year while others, within a similar landscape unit, are predominantly dry. An assessment of soil and hydrologic characteristics was initiated in restored and unrestored control bays to determine if a relationship exists. Soil morphology was described and permanent monitoring wells were installed at each site. Soil samples were collected by horizon to a depth of 2 meters at the topographic center of each site, and then analyzed. After three years, multiple regression analysis (stepwise backward and forward) was used to establish relationships between the soil physicochemical characteristics and bay hydroperiod in the undisturbed sites. Results from surface soils indicated that exchangeable acidity (EA) was the best single predictor of hydrology. The best double predictor was EA and total N and EA, total N and total C as the best triple predictor. A significant relationship (r2 = 0.96) between hydroperiod and clay content in the argillic horizon (Bt) was also observed. Subsequently, this relationship was utilized to predict hydrologic response using pre-restoration hydroperiod data. The model accurately identified sites that did not need hydrologic restoration (too wet), and effectively showed sites that responded well to restoration activities

Effects of Willow Overstory on Planted Seedlings in a Bottomland Restoration

Various treatments were applied to control overstory willow in the riparian area of the Pen Branch system in order to determine the effects of competition control on seedling survival and growth. Four species, bald cypress, water tupelo, green ash, and swamp chestnut oak, were planted under four levels of willow canopy (intact, 60% removal, 100% removal with herbicide, 100% with mechanical). Species were more important in determining survival than treatment. Bald cypress and green ash survived best. The willow canopy appeared to provide minor benefits during the first two years

Spatial and Temporal Patterns of Carbon Storage and Species Richness in Three South Carolina Coastal Plain Riparian Forests

Micro-topographic variations in carbon storage and their spatial distribution with respect to vegetation were studied in the Pen Branch system as well as intermediate and late successional forests. Overall measurements of above-ground biomass, soil carbon, and stand structure indicate rapid convergence with the patterns in late successional forests. Micro-site differences were small

Analysis of airborne LiDAR surveys to quantify the characteristic morphologies of northern forested wetlands

A new technique for quantifying the geomorphic form of northern forested wetlands from airborne LiDAR surveys is introduced, demonstrating the unprecedented ability to characterize the geomorphic form of northern forested wetlands using high-resolution digital topography. Two quantitative indices are presented, including the lagg width index (LWI) which objectively quantifies the lagg width, and the lateral slope index (LSI) which is a proxy measurement for the dome shape or convexity of the wetland ground surface. For 14 forested wetlands in central Ontario, Canada, northwestern Ontario, Canada, and northern Minnesota, United States, these indices were systematically correlated to metrics of topographic setting computed from LiDAR digital elevation models. In particular, these indices were strongly correlated with a Peatland Topographic Index (PTI, r2 = 0.58 and r2 = 0.64, respectively, p < = 0.001) describing the relative influence of upslope contributing area on the hydrology and biogeochemistry of individual wetlands. The relationship between PTI and the LWI and LSI indices was interpreted as geomorphic evolution in response to the spatially varying influence of upslope runoff on subsurface hydrochemistry. Spatial patterns of near-surface pore water chemistry were consistent with this interpretatio

Radiocarbon Analyses Quantify Peat Carbon Losses With Increasing Temperature in a Whole Ecosystem Warming Experiment

Climate warming is expected to accelerate peatland degradation and release rates of carbon dioxide (CO2) and methane (CH4). Spruce and Peatlands Responses Under Changing Environments is an ecosystem-scale climate manipulation experiment, designed to examine peatland ecosystem response to climate forcings. We examined whether heating up to +9 °C to 3 m-deep in a peat bog over a 7-year period led to higher C turnover and CO2 and CH4 emissions, by measuring 14C of solid peat, dissolved organic carbon (DOC), CH4, and dissolved CO2 (DIC). DOC, a major substrate for heterotrophic respiration, increased significantly with warming. There was no 7-year trend in the DI14 C of the ambient plots which remained similar to their DO14 C. At +6.75 °C and +9 °C, the 14C of DIC, a product of microbial respiration, initially resembled ambient plots but became more depleted over 7 years of warming. We attributed the shifts in DI14 C to the increasing importance of solid phase peat as a substrate for microbial respiration and quantified this shift via the radiocarbon mass balance. The mass-balance model revealed increases in peat-supported respiration of the catotelm depths in heated plots over time and relative to ambient enclosures, from a baseline of 20%–25% in ambient enclosures, to 35%–40% in the heated plots. We find that warming stimulates microorganisms to respire ancient peat C, deposited under prior climate (cooler) conditions. This apparent destabilization of the large peat C reservoir has implications for peatland-climate feedbacks especially if the balance of the peatland is tipped from net C sink to C source. © 2021 The Authors.Open access articleThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Warming response of peatland CO2 sink is sensitive to seasonality in warming trends

Peatlands have acted as net CO2 sinks over millennia, exerting a global climate cooling effect. Rapid warming at northern latitudes, where peatlands are abundant, can disturb their CO2 sink function. Here we show that sensitivity of peatland net CO2 exchange to warming changes in sign and magnitude across seasons, resulting in complex net CO2 sink responses. We use multiannual net CO2 exchange observations from 20 northern peatlands to show that warmer early summers are linked to increased net CO2 uptake, while warmer late summers lead to decreased net CO2 uptake. Thus, net CO2 sinks of peatlands in regions experiencing early summer warming, such as central Siberia, are more likely to persist under warmer climate conditions than are those in other regions. Our results will be useful to improve the design of future warming experiments and to better interpret large-scale trends in peatland net CO2 uptake over the coming few decades