Fifty years of forest hydrology in the southeast

2008

Understanding the hydrologic processes is the first step in making sound watershed management decisions including designing Best Management Practices for nonpoint source pollution control. Over the past fifty years, various forest experimental watersheds have been instrumented across the Carolinas through collaborative studies among federal, state, and private organizations. One of the most notable theoretical hydrological advances that directly resulted from studies in this region perhaps was Variable Source Area Concept (VSAC) proposed by John Hewlett and others. VSAC offers a framework that explains the mechanisms of streamflow generation at the watershed scale and provides a basis for developing watershed management practices for minimizing negative impacts on stream water quality. Unfortunately, due to the dynamic nature of the variable source area, a zone that varies across space and time, it is rarely measured and quantified at the watershed scale. This paper presents findings from a stormflow monitoring study that spans a physiographic gradient from the mountain to the sea. This study suggests that the variable source area and stormflow flow characteristics were most influenced by antecedent soil moisture conditions, which reflect the controls of climate and topography. We found that the saturated area was rather small in the Appalachians and piedmont upland watersheds, but it could be rather large and variable in the lower coastal plain watersheds. Implications of these contrasting differences in VSA to watershed management are discussed.

2004, Ottawa, Canada August 1 - 4, 2004, 2004

Managing forested wetland landscapes for water quality improvement and productivity requires a detailed understanding of functional linkages between ecohydrological processes and management practices. Studies are being conducted at Center for Forested Wetlands Research (CFWR), USDA Forest Service to understand the fundamental hydrologic and biogeochemical processes linking aquatic and terrestrial eco-systems. The first study is based on the long-term experimental watersheds established in 1960s on the USDA Forest Service Santee Experimental Forest, with the purpose of quantifying the soil moisture dynamics, flow regimes, and water chemistry of low gradient forested wetlands in South Carolina. In a cooperative research with North Carolina State University, a long-term study is being conducted at Weyerhaeuser Company's managed pine forest in Carteret County, North Carolina to quantify the effects of various water and silvicultural management impacts on the hydrology and water quality. A third long-term ecosystem study on

2000

Managing forested wetland landscapes for water quality improvement and productivity requires a detailed understanding of functional linkages between ecohydrological processes and management practices. Watershed studies are being conducted at USDA Forest Service Santee Experimental Forest, South Carolina, to understand the fundamental hydrologic and biogeochemical processes and their linkages with soils, vegetation, topography, climate, and management practices in the low gradient

2012 Dallas, Texas, July 29 - August 1, 2012, 2012

2009

In a parallel study, ten small watersheds (about 5 ha) were installed in the Priest River Experimental Forest (PREF) in northern Idaho, and another ten were installed in the Boise Basin Experimental Forest (BBEF) in central Idaho. The long-term objective of the study is to compare the effects of different forest management activities on runoff and sediment delivery. This paper reports the observed runoff hydrographs and amounts and the sediment yields during the first 3 to 4 years of the study. During the first 3 years, none of the watersheds received any management treatments or natural disturbances. In the autumn of year 3, a simulated wildfire was carried out at four watersheds in PREF. There was still no runoff from these four watersheds the spring following the fire. These observations will be useful for evaluating the natural variability in hydrologic responses on forest landscapes.

Journal of Forestry

This paired watershed study tested the effects of timber harvest on water quantity and quality in the North Carolina Piedmont physiographic region. Four headwater watersheds at Hill Demonstration Forest (HF1, HF2, HFW1, and HFW2) and two at Umstead Research Farm (UF1 and UF2) were continuously monitored for discharge and water quality from 2007 to 2013. The HF1 and UF1 watersheds were clearcut (treatment), leaving a 15.2-m vegetated riparian buffer around the streams to protect water quality as described in the North Carolina Neuse River Basin Riparian Buffer Rule. HF2 and UF2 were uncut and used as reference watersheds. Merchantable timber was selectively removed from the riparian buffer, reducing tree basal area by 27% in HF1 and 48% in UF1. HF1 and HF2 were nested within HFW1; thus, HFW1 was considered a partial cut where 33% of the watershed area was harvested, and HFW2 was the reference. We found that discharge in treatment watersheds increased dramatically, averaging 240% in HF1 and 200% in UF1 and 40% in HFW1 during the postharvest period, 2011-2013. Total suspended sediment export in the treatment watersheds also increased significantly in HF1 after harvest, probably due to the increase of discharge and movement of in-channel legacy sediment. Stormflow peak nitrate reached its maximum concentration during the first 2 years after harvest in the treatment watersheds and then declined, corresponding to the rapid regrowth of woody and herbaceous plants in the riparian buffer and uplands. We found that 36% of the UF1 streambank trees were blown down but did not cause a measurable increase in mean daily stormflow total suspended sediment concentration. Most buffer tree blowdown occurred during the first few years after a harvest. Bioclassification of benthic macroinvertebrates indicated that stream water quality remained good/fair to excellent in the treatment watersheds after the harvest. We conclude that the temporary increases in discharge were relatively large for the Piedmont region compared with those for other regions in the southeastern United States. However, the increases in channel sediment transport and nutrient exports associated with the hydrologic change did not have a measurable impact on the indicators of aquatic invertebrate community health or bioclassification rankings.

Forest Ecology and Management, 2001

The objectives of this paper are to review the hydrologic impacts of various common forest management practices that include harvesting, site preparation, and drainage. Field hydrological data collected during the past 5±10 years from ten forested wetland sites across the southern US are synthesized using various methods including hydrologic simulation models and Geographic Information Systems. Wetland systems evaluated include red river bottoms, black river bottoms, pocosins, wet mineral¯ats, cypress domes, and pine¯atwoods. Hydrologic variables used in this assessment include water table level, drainage, and storm¯ow on different spatial and temporal scales. Wetland ecosystems have higher water storage capacity and higher evapotranspiration than uplands. Hydrologic impacts of forest management are variable, but generally minor, especially when forest best management practices are adopted. A conceptually generalized model is developed to illustrate the relative magnitude of hydrologic effects of forest management on different types of wetlands in the southern US. This model suggests that in addition to soils, wetland types, and management practice options, climate is an important factor in controlling wetland hydrology and the magnitude of disturbance impacts. Bottomland wetlands, partial harvesting, and warm climate usually offer conditions that result in low hydrologic impact. #

Forest Ecology and Management

The objectives of this paper are to review the hydrologic impacts of various common forest management practices that include harvesting, site preparation, and drainage. Field hydrological data collected during the past 5±10 years from ten forested wetland sites across the southern US are synthesized using various methods including hydrologic simulation models and Geographic Information Systems. Wetland systems evaluated include red river bottoms, black river bottoms, pocosins, wet mineral¯ats, cypress domes, and pine¯atwoods. Hydrologic variables used in this assessment include water table level, drainage, and storm¯ow on different spatial and temporal scales. Wetland ecosystems have higher water storage capacity and higher evapotranspiration than uplands. Hydrologic impacts of forest management are variable, but generally minor, especially when forest best management practices are adopted. A conceptually generalized model is developed to illustrate the relative magnitude of hydrologic effects of forest management on different types of wetlands in the southern US. This model suggests that in addition to soils, wetland types, and management practice options, climate is an important factor in controlling wetland hydrology and the magnitude of disturbance impacts. Bottomland wetlands, partial harvesting, and warm climate usually offer conditions that result in low hydrologic impact.

Hydrological Processes, 2021

Long-term watershed experiments provide the opportunity to understand forest hydrology responses to past logging, road construction, forest regrowth, and their interactions with climate and geomorphic processes such as road-related landslides. We examined a 50-year record from paired-watershed experiments in the H. J. Andrews Experimental Forest, Oregon, USA in which 125 to 450-year-old conifer forests were harvested in the 1960s and 1970s and converted to planted conifer forests. We evaluated how quickflow and delayed flow for 1222 events in treated and reference watersheds changed by season after clearcutting and road construction, including 50 years of growth of planted forest, major floods, and multi-decade reductions in snowpack. Quickflow runoff early in the water year (fall) increased by up to +99% in the first decade, declining to below preharvest levels (À1% to À15%) by the third to fifth decade after clearcutting. Fall delayed flow responded more dramatically than quickflow and fell below pre-treatment levels in all watersheds by the fifth decade, consistent with increased transpiration in the planted forests. Quickflow increased less (+12% to 70%) during the winter and spring but remained higher than pre-treatment levels throughout the fourth or fifth decade, potentially impacted by post-harvest burning, roads, and landslides. Quickflow remained high throughout the 50-year period of study, and much higher than delayed flow in the last two decades in a watershed in which road-related changes in flow routing and debris flows after the flood of record increased network connectivity. A long-term decline in regional snowpack was not clearly associated with responses of treated vs. reference watersheds. Hydrologic processes altered by harvest of old-growth conifer forest more than 50 years ago (transpiration, interception, snowmelt, and flow routing) continued to modify streamflow, with no clear evidence of hydrologic recovery. These findings underscore the importance of continued long-term watershed experiments.

Hjerdt N. 2009. Nature as the "natural" goal for water management: a conversation. Ambio 38: 209-214. Blenckner T. 2005. A conceptual model of climate-related effects on lake ecosystems. Hydrobiologia 533: 1-14. Brockerhoff EG, Jactel H, Parrotta JA, Quine CP, Sayer J. 2008. Plantation forests and biodiversity: oxymoron or opportunity? Biodiversity and Conservation 17: 925-951. Brooks RT. 2009. Potential impacts of global climate change on the hydrology and ecology of ephemeral freshwater systems of the forests of the northeastern United States. Climatic Change 95: 469-483. Buttle JM. 2002. Rethinking the donut-the case for hydrologicallyrelevant buffer zones. Hydrological Processes 16: 3093-3096. Chapin FS. 2009. Managing ecosystems sustainably: the key role of resilience. In Principles of Ecosystem Stewardship: Resilience-Based Natural Resource Management in a Changing World , Chapin FS, Kofinas GP, Folke C (eds). Springer: New York; 29-53. Creed IF, Sanford SE, Beall FD, Molot LA, Dillon PJ. 2003. Cryptic wetlands: integrating hidden wetlands in regression models of the export of dissolved organic carbon from forested landscapes. Hydrological Processes 17: 3629-3648. Creed IF, Sass GZ, Wolniewicz MB, Devito KJ. 2008. Incorporating hydrological dynamics into buffer strip design on the sub-humid Boreal Plain of Alberta. Forest Ecology and Management 256: 1984-1994. Creed IF, Sass GZ, Beall FD, Buttle JM, Moore RD, Donnelly M. In press (a). Hydrological principles for water conservation and sustainable forest management. A State of Knowledge report. Sustainable Forest Management Network, Edmonton, Alberta. Creed IF, Sass GZ, Beall FD, Buttle JM, Moore RD, Donnelly M. In press (b). Conserving water resources in our changing forested landscapes: a synthesis of the state-of-knowledge on scientific theory, data, and techniques. A State of Knowledge report. Sustainable Forest Management Network, Edmonton, Alberta. Creed IF, Sass GZ. 2011. Digital terrain analysis approaches for tracking hydrological and biogeochemical pathways and processes in forested landscapes. In Forest Hydrology and Biogeochemistry: Synthesis of Past Research and Future Directions, Levia D, Carlyle-Moses D, Tanaka T (eds). Springer-Verlag: New York. Creed IF, Beall FD. 2009. Distributed topographic indicators for predicting nitrogen export from headwater catchments. Water Resources Research 45: W10407. Croke JC, Hairsine PB. 2006. Sediment delivery in managed forests: a review.

2014

The link between healthy forests and watersheds and healthy streamflow and quality water is universally recognized. The major rivers of the USA originate in the forested mountains of the western and eastern USA and the glaciated regions of the Lake States and Great Plains and produce almost two-thirds of the nation's clean water supply. Original logging and mismanagement of upstream forested watersheds often resulted in degradation of land and water resources and adversely impacted aquatic and human populations. During the 30-year period, between the 1930s and 1960s, experimental forests, ranges, and watersheds were established on national forests and adjacent lands to study the impacts of land conditions on water yield, stormflow, water quality, and nutrient cycling. While the impact of sustained timber production was an original research focus, current efforts include research on nutrient cycling, carbon sequestration, climate change, fire effects, and the impacts of insects and diseases. The experimental forest network of long-term meteorological and biological records is invaluable for evaluations of potential climate change and its consequences on the forests and water resources. This chapter reviews hydrology Chapter 14

2011

• Forest conversion to agriculture or urban use consistently causes increased discharge, peak flow, and velocity of streams. Subregional differences in hydrologic responses to urbanization are substantial. • Sediment, water chemistry indices, pathogens, and other substances often become more concentrated after forest conversion. If the conversion is to an urban use, the resulting additional increases in discharge and concentrations will produce even higher loads. • Although physiographic characteristics such as slope and soil texture play key roles in hydrologic and sediment responses to land use conversion, land use (rather than physiography) is the primary driver of water chemistry responses. • Conversion of forest land to urban uses may decrease the supply of water available for human consumption and increase potential threats to human health.

2011