Streamside Management Zones Research Articles

Ten-Year Response of Riparian-Associated Songbirds to Implementation of Streamside Management Zones in Watershed-Scale Harvests in the Appalachian Mountains

Abstract Streamside management zones (SMZs) are regulated components of actively managed forests in the eastern United States, but width and overstory retention requirements vary widely among states. Within watershed-scale harvests, we evaluated the relative abundances of three riparian-associated songbirds (Acadian flycatcher, Empidonax virescens; blue-headed vireo, Vireo solitarius; and Louisiana waterthrush, Parkesia motacilla) near Appalachian headwater streams receiving three SMZ treatments representative of a range of current state SMZ regulations in the eastern United States. Prior to harvest, all species were relatively abundant near all stream types, including ephemerals. Abundances of all species were largely similar among SMZ treatments at 3 years and 10 years postharvest and were higher along streams with greater residual canopy cover within 100 m. Forested SMZs as prescribed by current regulations can sustain these species in managed forests up to 10 years postharvest, but abundance appears to be driven largely by canopy cover retention in adjacent stands. Managing habitat for riparian-associated songbirds in harvested watersheds will require expanding the extent of focus beyond the local stream corridor to include consideration of silvicultural systems that retain greater canopy cover in surrounding forests. Where conservation of riparian-associated songbirds is a management objective, SMZ protection should be extended to all streams. Study Implications: The results of this study suggest that forested streamside management zones (SMZs) mandated by contemporary best management practices (BMPs) in Kentucky and other eastern US states can sustain similar abundances of three riparian-associated songbirds in managed watersheds up to 10 years after harvest. Overstory retention in SMZs along perennial and intermittent streams is common across the eastern United States, but state BMPs rarely require retention along ephemeral streams. Target songbird species occupied forests along all stream types prior to harvest, and their postharvest abundances were positively associated with canopy retention within 100 m of streams. If long-term occupancy of managed stands by riparian-associated songbirds is an objective, we recommend using SMZs around all streams, including ephemerals, and implementing at least moderate-retention silvicultural systems in areas within 100 m of streams.

Long-term changes in coarse woody debris abundance in three Appalachian headwater streams with differing best management practices

IntroductionTimber harvests influence coarse woody debris (CWD) dynamics both initially and long-term—contributing a significant amount of CWD as slash immediately after harvest, but also removing some or all of the mature trees necessary to produce CWD over time. Whereas shelterwood and other similar timber harvest systems retain varying amounts of the overstory, preserving CWD production after harvest, commercial clearcutting essentially eliminates sources of fresh CWD until regenerating trees are large enough to contribute CWD through fallen limbs or trunks, often decades after harvest. Forestry best management practices (BMPs) are critical for reducing the water quality impacts of timber harvest, but their effects on riparian and stream CWD are not well understood.MethodsThe current project explores CWD dynamics (surveyed in 2001, 2004, 2009, and 2020) in three eastern Kentucky watersheds receiving differing timber harvest treatments in 1983: unharvested control, BMPs (clearcut with a protected streamside management zone), and no BMPs (clearcut).ResultsAnalysis of hydrology data over the period of record demonstrated significant flooding in 2004 that likely “reset” CWD in the study watersheds. Coarse woody debris volume was higher in control (3.33 m3/ha) than no BMP (1.03 m3/ha) in 2020, with CWD accumulation rates ranging from 0.039 m3/ha in the no BMP watershed to 0.19 m3/ha in the control.DiscussionWhile not significantly different, CWD volume was nominally higher in the BMP watershed than the No BMP watershed, suggesting that, in addition to their many other benefits, streamside management zones help facilitate CWD provisioning during stand initiation after a commercial clearcut harvest. Furthermore, this study suggests that provisioning of CWD may not recover after clearcut harvesting for 100 years or more.

Best Management Practices, Estimated Erosion, Residual Woody Debris, and Ground Cover Characteristics Following Biomass and Conventional Clearcut Harvests in Virginia’s Mountains

Abstract Water quality best management practices (BMPs) developed for conventional forest harvests may be adequate for biomass harvests, yet quantitative data is lacking. This study compared estimated erosion, operational feature areas, BMP implementation rates, ground cover characteristics, and downed woody debris quantities following biomass and conventional harvests in the mountains of Virginia. Haul roads on biomass harvests had significantly higher estimated erosion rates (P = 0.064) and masses (P = 0.045) than conventional harvests, but conventional harvests had higher erosion contributions from skid trails (P = 0.089) and averaged more estimated erosion mass overall, despite being significantly smaller in size (P = 0.054). There was significantly less area in heavy slash (P = 0.076) and lower estimated mass of residual downed woody debris (P = 0.001) on biomass sites than conventional sites (10.98 and 27.95 tons/ac, respectively). Site-wide BMP implementation scores (P = 0.041), streamside management zones (SMZs) (P = 0.024), and skidding (P = 0.063) were significantly higher on biomass sites than conventional sites. BMP implementation scores were significant predictors of estimated erosion rates (P < 0.001, R2 = 59%), indicating that adequate levels of existing water quality BMPs are effective for erosion control on both conventional and biomass harvests.

Linkages between Forestry Best Management Practices and erosion in the southeastern U.S.

Numerous studies have concluded that forestry Best Management Practices (BMPs) are effective at mitigating erosion and sedimentation caused by forest operations; however, the complex relationship between forestry BMPs and erosion is largely unexamined. In this study, BMP implementation rates, which are percentages ranging from 0 to 100% that indicates how well an operator instituted recommended practices in the field, and predicted erosion rates, obtained by using USLE-Forest, were calculated for 108 recent harvests in twelve states and three physiographic regions in the southeastern U.S. BMP implementation rates were subdivided into three levels of application: BMP+ (>90% implementation), BMP-standard (80–90% implementation), and BMP− (<80% implementation). Skid trails (86.5 Mg ha−1 yr−1) and haul roads (90.3 Mg ha−1 yr−1) eroded at relatively high rates at the BMP− level across the southeast. This emphasizes the importance of adequate BMP measures such as utilizing water diversion structures and cover management at these features to better protect water quality. The overall weighted average erosion estimates for all regions at the BMP-standard (10.4 Mg ha−1 yr−1) and BMP+ (6.6 Mg ha−1 yr−1) levels were <11 Mg ha−1 yr−1, indicating that water quality and site productivity are largely protected when adequate BMPs are implemented, and Streamside Management Zones (SMZs) are utilized along streams. Approximately 94% of the sites sampled were classified as either BMP-standard or BMP+, demonstrating that BMPs are being implemented consistently throughout the southeast. Spearman ρ correlation analyses were performed for all variables. Forestry BMP implementation and erosion estimates had significant negative correlations, especially for skid trails (Spearman ρ = −0.59, p-value < 0.0001) and haul roads (Spearman ρ = −0.39, p-value = < 0.0001), as well as for all regions across the southeast. These variables, however, were poorly correlated for stream crossings, indicating that current audit questions in the southeast may not fully address erosion. Additionally, BMP implementation and erosion estimates exhibited a significant negative correlation (R2 = 0.28, p-value < 0.0001) based on a quadratic regression line for all features, reinforcing that as BMP implementation increases, predicted erosion generally decreases.

Relationship Between Riparian Buffers and Terrestrial Wildlife in the Eastern United States

Abstract When working forest stands are harvested, vegetated strips along streams are often retained as part of forestry best management practices (BMPs) to protect water quality. These riparian buffers, known as streamside management zones, when following forestry BMP recommendations, also likely provide benefits to various terrestrial wildlife species. To better understand the role of riparian buffers in contributing to biological diversity in working forest landscapes, we reviewed literature (n = 30) that reported on herpetofauna, bird, and mammal responses to riparian buffers in the eastern United States. Although few results were consistent among taxa, community composition commonly varied among riparian buffer widths. Narrower riparian buffers more commonly supported edge and disturbance-associated species whereas wider riparian buffers tended to support interior-associated species. We did not find a consistent width that supported all terrestrial wildlife species studied.

Implementation of Forestry Best Management Practices and Sediment Delivery in Three Regions of North Carolina and Virginia

Abstract Forestry best management practices (BMPs) were created in response to the Clean Water Act of 1972 to protect water quality from nonpoint source pollutants such as sediment. The objectives of this study were to quantify the relationship between BMP implementation and sediment delivery on 58 recently harvested sites across three physiographic regions and five forest operational features. BMP implementation rates, erosion rates, sediment delivery ratios, and sediment masses were calculated at 183 silt fences functioning as sediment traps adjacent to streams in Virginia and North Carolina. Major access system features, including stream crossings, skid trails, and haul roads, typically delivered the greatest sediment mass to streams and had the highest sediment delivery ratios on a per feature basis. When accounting for sediment mass delivered and area in each feature, harvest area accounted for approximately 70% of sediment delivered to streams for all regions. Most features had proportionally higher erosion rates than sediment masses collected at silt fences, indicating that most erosion generated by forest operations is being trapped by either harvest areas or streamside management zones. For most features and regions, as BMP implementation increased, erosion rates and the sediment masses delivered to streams decreased.

Increased growth rates of stream salamanders following forest harvesting.

Timber harvesting can influence headwater streams by altering stream productivity, with cascading effects on the food web and predators within, including stream salamanders. Although studies have examined shifts in salamander occupancy or abundance following timber harvest, few examine sublethal effects such as changes in growth and demography. To examine the effect of upland harvesting on growth of the stream‐associated Ouachita dusky salamander (Desmognathus brimleyorum), we used capture–mark–recapture over three years at three headwater streams embedded in intensely managed pine forests in west‐central Arkansas. The pine stands surrounding two of the streams were harvested, with retention of a 14‐ and 21‐m‐wide forested stream buffer on each side of the stream, whereas the third stream was an unharvested control. At the two treatment sites, measurements of newly metamorphosed salamanders were on average 4.0 and 5.7 mm larger post‐harvest compared with pre‐harvest. We next assessed the influence of timber harvest on growth of post‐metamorphic salamanders with a hierarchical von Bertalanffy growth model that included an effect of harvest on growth rate. Using measurements from 839 individual D. brimleyorum recaptured between 1 and 6 times (total captures, n = 1229), we found growth rates to be 40% higher post‐harvest. Our study is among the first to examine responses of individual stream salamanders to timber harvesting, and we discuss mechanisms that may be responsible for observed shifts in growth. Our results suggest timber harvest that includes retention of a riparian buffer (i.e., streamside management zone) may have short‐term positive effects on juvenile stream salamander growth, potentially offsetting negative sublethal effects associated with harvest.

The Harvest Operability Index (HOI): A Decision Support Tool for Mechanized Timber Harvesting in Mountainous Terrain

Forest operations have become increasingly reliant on mechanized harvesting equipment due to their increased production capacities in competitive markets. However, operating heavy machinery in mountainous terrain poses numerous operational and accessibility challenges from steep slopes, erosion risk, and poor road access. Geographic Information Systems (GIS) have effectively been used in various studies to identify areas in mountainous landscapes that pose no or reduced constraints for harvesting equipment operation. This study introduces the Harvest Operability Index (HOI), which rates a landscape for wheel-based equipment suitability (i.e., operability) and assesses its application in 13,118 ha of the Jocassee Gorges Natural Resource Area, situated on the Southern Blue Ridge Escarpment in Northwestern South Carolina, USA. The HOI incorporated slope, distance from roads, cost distance from major highways, primary Streamside Management Zones (SMZ), stand age, and soil suitability ratings for harvesting equipment operation. Upon reclassification to a 5-tier suitability scale, the HOI revealed 60% (7824 ha) of the case study area was in a Slope Exclusion Zone, or land area inoperable for wheel-based equipment due to steep slopes. Values of Very Poor and Poor Operability occupied less than 1% (213 ha) of land area whereas Moderate Operability values were 9% of the land area (1257 ha). Values of Good Operability occupied 18% (2442 ha) of the study area and values of Very Good Operability occupied 10% (1381 ha). These results reflected the challenges of mechanized harvesting in the study area due to a preponderance of steep slopes and poorly suited soil. Our model delineated areas of high equipment operability in two locations in the study area, despite a lack of recent logging activity around them. Results of the HOI analysis offer an accessible way for forest managers to better prioritize logging operations in areas that are highly operable and therefore more likely to possess lower overall harvesting costs, for wheel-based harvesting systems. The HOI can also be used as an asset for other forest management priorities, such as identifying highly operable areas that can use timber harvesting for fuel reduction and ecological restoration in fire-dependent forests. This model can be applied to various other regions where mountainous terrain poses a limitation to wheel-based harvesting equipment operation- and where wheel-based equipment is essential to advance the pace and scale of harvesting for ecological restoration.

Understanding dissolved oxygen concentrations in a discontinuously perennial stream within a managed forest

The concentration of oxygen dissolved in water affects aquatic organisms. Unrestrained logging and site preparation can depress dissolved oxygen (DO) concentrations in adjacent streams by elevating temperatures (with removal of riparian shade), impounding channels (reduced reaeration rates), and introducing fresh, oxygen-depleting slash. One of the first paired watershed studies investigating the use of streamside management zones, the Alsea Watershed Study (AWS) in coastal Oregon (1958–1973), highlighted the potential to depress DO concentrations in streams adjacent to harvest units. This and other studies spurred development of Best Management Practices (BMPs) and forest practice rules to maintain, among other things, favorable DO concentrations in streams. A new study of the Alsea watersheds (2006–2015) found little signal of management effects on DO concentrations. It did find that a discontinuously perennial stream (where reaches go subsurface during low flows) can experience naturally low DO concentrations. Forest managers can avoid exacerbating low DO conditions using simple BMPs, but discontinuously perennial forest streams are predisposed to low DO concentrations.

Influence of Timber Harvesting Operations and Streamside Management Zone Effectiveness on Sediment Delivery to Headwater Streams in Appalachia

Disturbances created by timber harvesting equipment and associated haul roads and skid trails can create overland sediment flows (sediment paths), especially in steeply sloping terrain, leading to stream sedimentation. This study investigated the effect of variables associated with GPS tracked harvest equipment movement, skid trail development and retirement, topography, and streamside management zone (SMZ) width and tree retention on sediment delivery to streams. While the intensity of harvest equipment traffic was not correlated with sediment path development, the presence and location of skid trails were. All of the sediment paths were found to originate at water control structures, influenced by microtopographic features, on the skid trails directly adjacent to SMZs. Mesic slopes were associated with increased sediment path development across all SMZ configurations. Two factors, the accumulation of coarse logging debris in the SMZ and the increased distance of skid trails to streams, were both correlated with decreased sediment path development. The study provides insight into how these variables interact and can be used to develop site-specific guidelines for SMZs in steeply sloping terrain that could improve their efficiency and effectiveness.

Financial Assessment of Future Stand Conditions Required to Recover the Opportunity Costs of a North Louisiana Streamside Management Zone

Abstract Understanding the costs that residual habitat spaces carry into future rotations can provide managers more complete information when financially assessing timber management options that often extend for many decades. This case study assessed a streamside management zone's (SMZ) opportunity costs for a timber harvest site in north Louisiana. Timber removal occurred in summer 2018 by clearcut. A wooded buffer extending 50 feet on each side of a streambank and totaling 7.52 acres was retained; partial harvesting of pine timber was allowed. A timber inventory revealed that 99.6 tons per acre of standing hardwoods resided within the SMZ. Excluding noncommercial species placed its current present value (opportunity cost) at $1,803. Two future active management scenarios, “controlled” and “intensive,” were modeled over the next rotation at a 4 percent real discount rate, where price changes occurred at 0, 1, 2, 3, and 4 percent annually. Both management strategies consistently produced positive land expectation values (LEV) when SMZ opportunity costs were not included in the assessment. However, inclusion of SMZ protection under “controlled” management required timber price changes of 4 percent annually, while the “intensive” management option required timber price changes of at least 3 percent annually to return positive LEVs.

Differential responses of amphibian and reptile assemblages to size of riparian buffers within managed forests.

Streamside management zones (i.e., riparian buffers; SMZs) are commonly implemented within managed forests to protect water quality but may also provide habitat for riparian-associated wildlife. Yet, little research has rigorously addressed the value of SMZs for wildlife, particularly for cryptic species such as amphibians and reptiles. Previous studies of herpetofauna within SMZs have focused on one or a few stream-associated species, and questions remain regarding variation among species or guilds and what role SMZs serve toward conservation of herpetofaunal diversity in managed forests. However, recent statistical advances have improved our ability to analyze large multi-species presence-absence data sets, accounting for low detection rates typical for some herpetofaunal species. Our study represents an extensive landscape-scale examination of herpetofaunal communities within SMZs using a multi-species occupancy approach. We conducted four replicate surveys at 102 headwater streams, spanning a gradient of SMZ widths and adjacent forest stand ages, within the Ouachita Mountains, Arkansas, USA. We used a hierarchical Bayesian community occupancy model to estimate species richness and species-specific occupancy responses to SMZ and overstory characteristics, accounting for variation in occupancy and detection attributable to site and sampling covariates. We documented high richness (37 species) within SMZs. Across the herpetofaunal community, occupancy and species richness were consistently positively associated with SMZ width, with maximum predicted richness of 30 species occurring at sites with buffers extending 51m on either side of the stream. However, we documented considerable variation among groups and species within groups, underscoring the potential for different responses to forest management among taxa. Reptile predicted richness increased more rapidly up to SMZs of ~35m, whereas maximum salamander predicted richness was not seen until an SMZ width of 55m. Estimated salamander richness was highest within SMZs embedded in mature managed pine stands and was higher in SMZs comprised of a deciduous or mixed overstory vs. a pine overstory. Compared to salamanders, more anuran species showed high mean estimated occupancy (>75%) at narrower SMZs (<30m). Collectively, our results indicate that SMZs surrounding small first-order streams in intensively managed forests not only protect water quality, but also can support diverse amphibian and reptile communities.

Changes in stream morphology protected by best management practices under effects of upstream disturbances

Stream channels are usually more stable in forested watersheds. However, intensive land disturbances in forested watersheds may disrupt the balance between flow and sediment supply, and result in variations in stream morphology even in the presence of well-designed best management practices (BMPs). This study evaluated the impacts of upstream land disturbances on downstream stream morphology where streamside management zones (SMZs) were present in two small adjacent watersheds in Auburn, Alabama, USA. Field surveys including the measurements of channel cross sections at bankfull stage were conducted at 12 survey sites over an 18-month period. Both in-stream sediment deposition and erosion were observed downstream of the disturbed areas in the study watersheds. As a result, channel cross sections exhibited very dynamic patterns changing frequently over short time periods. Overall, the dominant process was in-stream deposition in both watersheds due to large amount of sediment delivered from upstream-disturbed areas. In spite of the dynamic patterns of the channel cross sections in response to upstream disturbances, the commonly used parameters of Rosgen stream classification remained stable, suggesting that the upstream disturbances did not lead to changes in stream classification. In general, bank erosion was not observed. Therefore, it is likely that SMZs in each watershed were sufficient to stabilize streambanks by hindering in-stream bank erosion. Moreover, the poorly designed BMPs such as silt fences and straw bales near the disturbed area seemed insufficient to balance the variations in sediment supply under the impacts of upstream disturbances. This study emphasized that proper installation and continuous monitoring of BMPs should play a critical role on watershed management. It also indicated that watershed management should be handled using a holistic approach with well-distributed BMP applications within the entire watershed.

Streamside management zone effectiveness for water temperature control in Western Montana

ABSTRACTAn important function of Streamside Management Zones (SMZs) retained during harvest operations is shading for temperature control. SMZ width and allowable timber removal varies by state. In Montana, an SMZ law requires that timber be retained within 15.2 m of streams, with a steep-slope ground-based equipment exclusion area that can extend up to 30.5 m. The amount of timber removal in the SMZ is a function of pre-harvest tree size and stocking, with removals of 0–30% typical. The effectiveness of SMZs for stream temperature control in Montana has not been previously evaluated. Between 1999 and 2004, half-hourly stream temperature data were collected at 30 operational harvest sites bordering perennial fish-bearing streams in western Montana. Temperature data were collected at the upper and lower boundary of the harvest, for a minimum of one summer before and after harvest. Covariate data were collected to describe the harvest, and fish data collected to evaluate biological response that may be associated with temperature changes. Response measures were analyzed using a linear mixed effects model. The model structure was based on the experimental design and included terms for year, position, harvest-state, and a position × harvest-state interaction, with the latter term used to estimate the impact of harvest on stream temperature. Results found no significant harvest effect for the six evaluated temperature metrics, with estimates between –0.1 and 0.04°C. Fish population and biomass also had no significant harvest effect. These results suggest that operational SMZs being retained in Montana are protective of water temperature.

The effectiveness of forestry best management practices at skidder stream crossings in Virginia

Sediment is the most common nonpoint source pollutant associated with timber harvesting in the southeastern United States. Sediment is of particular concern at operational stream crossings because sediment delivery potential is increased by stream proximity and any compromised streamside management zone buffers. This study quantifies the effectiveness of water quality best management practices (BMPs) implemented at operational skidder stream crossings in three physiographic regions of Virginia. We located 79 operational skid trail crossings and assessed implementation of state BMP manual recommendations, percentage positive response to a Virginia Department of Forestry BMP audit questionnaire, and potential soil erosion as predicted by the Universal Soil Loss Equation (USLE)-Forest methodology and Water Erosion Prediction Project: Road interface. Estimated erosion rates decreased with increasing BMP scores for skid trails (p

Hydrological indicators of flow in headwaters for assessing farm management impacts: Streamside forestry management case study

Hydrological indicators have been used for interpreting stream flow patterns in large catchments. It would be useful to evaluate such indicators for use also in headwater catchments close to the source of on-farm management impacts. Reforestation of cleared farmland is encouraged internationally for water quality and biodiversity improvements. One practice option is to establish fast-growing plantations in streamside management zones (SMZs), but impacts on stream flows are not well understood. A eucalypt plantation was established in a steep headwater catchment in temperate Australia and stream flows compared 2 years pre- and 4 years post-establishment with an adjacent unplanted catchment. The flow ratio of SMZ to control was never significantly different from one (no SMZ effect) despite a significant decreasing trend during the six-years of monitoring. The decrease in flow ratio was attributable mainly to a reduction in some higher flows resulting from increased surface roughness and interception of overland flow. Nonparametric analyses also indicated a reduction of some low flows due to plantation establishment. Overall, changes in flow patterns appeared minor, but the value placed on such changes will depend on social and environmental contexts. Because of the rarity of such data and the importance of understanding water flows as affected by plantations established on farmland, similar studies should be conducted elsewhere. The range of flow indicators tested in this case were useful and should be considered for other similar applications. In addition, a simulation capability needs to be developed to enable the effects of SMZ plantations on stream flows to be predicted for a range of climate, landscape and management contexts and to contribute further to policy and practice discussions.

Influence of riparian buffers and habitat characteristics on salamander assemblages in headwater streams within managed forests

Streamside management zones (SMZs), buffers of forest retained along streams when adjacent areas are harvested, are a primary tool for maintaining ecological functions in managed forests. However, few studies have examined the influence of SMZs on salamanders, and none have examined variation in salamander occupancy, species richness, and abundance across a gradient of SMZ widths at a large spatial scale. Further, because previous studies had limited ability to detect responses of uncommon species, little is known about interspecific variation in salamander responses or whether SMZs serve as refuges for terrestrial species during harvesting. To evaluate the role of SMZs in maintaining salamander species, we conducted four replicate surveys at 102 headwater stream sites, spanning a gradient of SMZ widths and adjacent forest stand ages, within the Ouachita Mountains, Arkansas, USA. We used a hierarchical Bayesian community occupancy model to estimate salamander species richness and species-specific occupancy responses to SMZ and overstory characteristics, while accounting for variation in occupancy and detection attributable to site and sampling covariates. Additionally, we used Bayesian binomial mixture models to examine the influence of SMZ width and surrounding stand age on abundance of two stream-associated salamanders [Ouachita dusky salamander (Desmognathus brimleyorum) and many-ribbed salamander (Eurycea multiplicata)] and three terrestrial salamanders [red-backed salamander (Plethodon serratus), slimy salamander (P. glutinosus complex), and Caddo Mountain salamander (P. caddoensis)]. Occupancy, species richness, and abundance increased with increasing SMZ width, but the strength of responses varied among species. Occupancy of uncommon species was highest at sites with wide SMZs, likely because of the need for specific habitat elements (e.g., wetlands, rocky talus). Richness was lowest in SMZs dominated by pine overstory, and lowest in mid-aged stands, consistent with a lagged decrease in richness within SMZs following harvest. Finally, we documented patterns of abundance consistent with the evacuation hypothesis, indicating that salamanders may leave recently harvested areas seeking more suitable habitat and microclimate within SMZs. Collectively, results indicate that SMZs in intensively managed forests can support robust salamander communities, provided managers continue to retain wide SMZs at some key sites across the landscape (i.e., ≥55 m on each side of the stream), a value larger than current Forestry BMP guidelines.

Breeding bird communities associated with land cover in intensively managed pine forests of the southeastern U.S.

Abstract Intensively managed pine (Pinus spp.) forests (IMPFs) in the southern U.S. are often harvested by clearcutting in conjunction with green tree retention (i.e., retention of unharvested or less-intensively harvested trees and other vegetation), which is thought to promote structural diversity and to benefit wildlife. Management units in IMPFs thus primarily consist of regenerating pine clearcuts (RCCs) plus retained cover in streamside management zones (SMZs: vegetative buffers along perennial and intermittent streams) and/or stringers (forested buffers along ephemeral drains). To understand relationships between retained structures and avian communities, we documented and compared species diversity of breeding bird species and avian guilds in three-year-old RCCs and associated SMZs and stringers on 60 IMPF management units within the South Central Plains ecoregion of the southeastern U.S. We detected 5617 individuals of 60 species. Eight species were considered “common birds in steep decline,” one of which was frequently detected (Prairie Warbler, Setophaga discolor). Three of our 15 most frequently detected species were identified by Partners in Flight as “warranting management attention” for “moderate or high regional declines,” and 19 other species were listed as “warranting management attention” but were uncommonly detected. Forty-two of 44 species documented in RCCs were also observed accessing retention cover areas. SMZs and stringers comprised an average of 17.4% of management unit area, but 27% of species were detected solely in retention cover types. There was an 84% species overlap between SMZs and stringers. Stringers augmented SMZ contributions to site avian diversity by hosting forest specialist guilds. Diversity of early-successional specialists was similar between stringers and RCCs, suggesting stringers also enhanced RCC contributions to site bird diversity. Furthermore, we detected several species only within stringers. Green tree retention land cover contributed to stand scale avian diversity disproportionately to its area, and in particular, stringer cover appeared to enhance the value to avifaunal species diversity of RCC and SMZ patches.

Forestry Best Management Practices Relationships with Aquatic and Riparian Fauna: A Review

Forestry best management practices (BMPs) were developed to minimize water pollution from forestry operations by primarily addressing sediment and sediment transport, which is the leading source of pollution from silviculture. Implementation of water quality BMPs may also benefit riparian and aquatic wildlife, although wildlife benefits were not driving forces for BMP development. Therefore, we reviewed literature regarding potential contributions of sediment-reducing BMPs to conservation of riparian and aquatic wildlife, while realizing that BMPs also minimize thermal, nutrient, and chemical pollution. We reached five important conclusions: (1) a significant body of research confirms that forestry BMPs contribute to the protection of water quality and riparian forest structure; (2) data-specific relationships between forestry BMPs and reviewed species are limited; (3) forestry BMPs for forest road construction and maintenance, skid trails, stream crossings, and streamside management zones (SMZs) are important particularly for protection of water quality and aquatic species; (4) stream crossings should be carefully selected and installed to minimize sediment inputs and stream channel alterations; and (5) SMZs promote retention of older-age riparian habitat with benefits extending from water bodies to surrounding uplands. Overall, BMPs developed for protection of water quality should benefit a variety of riparian and aquatic species that are sensitive to changes in water quality or forest structure.

Water quality effects of short-rotation pine management for bioenergy feedstocks in the southeastern United States

Growing interest in renewable and domestically produced energy motivates the evaluation of woody bioenergy feedstock production. In the southeastern U.S., woody feedstock plantations, primarily of loblolly pine (Pinus taeda), would be intensively managed over short rotations (10–12years) to achieve high yields. The primary differences in managing woody feedstocks for bioenergy production vs for pulp/sawtimber production include a higher frequency of pesticide and fertilizer applications, whole-tree removal, and greater ground disturbance (i.e., more bare ground during stand establishment and more frequent disturbance). While the effects of pulp/sawtimber production on water quality are well-studied, the effects of growing short-rotation loblolly pine on water quality and the efficacy of current forestry Best Management Practices (BMPs) have not been evaluated for this emerging management system. We used a watershed-scale experiment in a before-after, control-impact design to evaluate the effects of growing loblolly pine for bioenergy on water quality in the Upper Coastal Plain of the southeastern U.S. Intensive management for bioenergy production and implementation of current forestry BMPs occurred on ∼50% of two treatment watersheds, with one reference watershed in a minimally managed pine forest. Water quality metrics (nutrient and pesticide concentrations) were measured in stream water, groundwater, and interflow (i.e., shallow subsurface flow) for a two-year pre-treatment period, and for 3.5years post-treatment. After 3.5years, there was little change to stream water quality. We observed a few occurrences of saturated overland flow, but sediments and water dissipated within the streamside management zones in over 75% of these instances. Stream nutrient concentrations were low and temporal changes mainly reflected seasonal patterns in nitrogen cycling. Nitrate concentrations increased in groundwater post-treatment to <2mgNL−1, and these concentrations were below the U.S. drinking water standard (10mgNL−1). Applied pesticides were almost always below detection in streams and groundwater. Overall, these findings highlight that current forestry BMPs can protect stream water quality from intensive pine management for bioenergy in the first 3.5years. However, groundwater quality and transit times need to be considered in these low-gradient watersheds of the southeastern U.S. that are likely to become an important location for woody bioenergy feedstock production.