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Retained vegetation density of streamside management zones and stringers in southern intensively managed pine forests
Abstract
In the southern U.S. (hereafter, South), institutional forest owners engaged in forest certification programs often retain unharvested or less-intensively harvested vegetation when clearcut harvesting intensively managed pine (Pinus spp.) forests (IMPFs). As a result, IMPF landscapes consist of regenerating forests and associated retained streamside management zones (SMZs), stringers (buffer strips along ephemeral streams), and other forest types and structural classes. Although studies in the South have documented plant and animal communities associated with SMZs, there is a lack of information about stringers. To improve understanding of the potential for stringers to contribute to biodiversity-related management objectives, we characterized stem density and vegetation cover in SMZs and stringers associated with 60 IMPF management units (MUs) in the South Central Plains ecoregion of Arkansas and Louisiana, USA. Snag and log density, midstory pine density, understory deciduous cover, and ground cover were not statistically different in stringers and SMZs; however, overstory (pine and deciduous) and midstory (deciduous) tree density was significantly lower in stringers than in SMZs, and understory pine density was significantly greater in stringers.
... Retention of individual live trees or unharvested patches of vegetation (e.g., green tree retention) is commonly recommended to promote post-harvest structural diversity (Franklin et al., 1997;Gustafsson et al., 2012), and benefits include: (a) retention of biological legacies; (b) greater structural complexity; and (c) improved landscape connectivity (Abernethy and Turner, 1987;Franklin et al., 1997;Lindenmayer and Franklin, 2002;Aubry et al., 2009). Southern forest managers typically retain unharvested or less-intensively managed vegetation as buffers around perennial and intermittent streams, termed streamside management zones (SMZs), and as buffers around ephemeral drains, that are commonly called 'stringers' (Parrish et al., 2017). In addition to protecting water quality, this form of retention limits overtopping vegetation in the regenerating clearcut that could subsequently interfere with forest regeneration and later forestry operations. ...
... Although stringer vegetation is structurally similar to SMZ vegetation in several respects, the two cover types are distinct in ways that could potentially influence presence of associated bird species: stringers and SMZs in young IMPFs did not differ in ground cover, understory deciduous cover, or density of snags, logs, and midstory pines; but, SMZs had greater density of overstory deciduous and pine trees and slightly greater density of midstory deciduous trees, while stringers had greater understory pine stem density (Parrish et al., 2017). Land managers have expressed interest in better understanding associations between species diversity and retained structural elements on IMPF management units. ...
... We used a guild-based approach (Root, 1967;Blondel, 2003;Gray et al., 2006) towards assessing avian species diversity associations with management unit cover types, as areas exhibiting high withinguild species diversity can be inferred to be beneficial to most or all members of the guild (Bishop and Myers, 2005). Of particular interest, given the similarity of vegetation structure and close spatial proximity between SMZs and stringers (Parrish et al., 2017), was the degree of avian diversity overlaps between those cover types. ...
... Thus, our findings corroborate those of Peterman et al. (2011). Further, this result supports the idea that streams and their associated SMZs, along with stringers (i.e., vegetated buffers retained along ephemeral drainages/gullies; Parrish et al., 2017), may be important as refugia for species negatively affected by forest harvest. Similar larval abundances across stand age categories suggest that reproduction was not strongly influenced by stand age or mid-rotation silvicultural treatments including commercial thinning. ...
... This study demonstrates that SMZs extend beyond protection of water quality; they provide critical habitat for semi-aquatic and terrestrial amphibians and are effective for conserving salamander populations and communities in managed forests. Across the managed forest landscape of the southern Ouachita Mountains, average SMZ width generally follows Forestry Best Management Practice guidelines (11-24 m), although wider buffers occur, and up to 18% of the landscape is preserved through riparian SMZs and stringers (Parrish et al. 2017). We estimate that 1-5 (mean = 3) salamander species will occur within SMZs of the width recommended by local BMP guidelines; therefore, current BMPs are effective for maintaining occupancy of common species. ...
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.
... Regardless of the platform used, or the ecosystem of interest, SampleFreq can be used to measure plant frequency. As an example, vegetation point classification from nadir images using the closely-related program SamplePoint has been completed across many ecosystems with varying plant communities, including grasslands, temperate and tropical forests, alpine tundra, salt marshes and deserts (Guo et al., 2016, Parrish et al., 2017, Skipper et al., 2013, Goonan et al., 2009, Bacopoulos et al., 2018,Tabeni et al., 2014 as well as agricultural settings (Nielsen et al., 2015). We therefore think it reasonable to anticipate successful use of SampleFreq in these ecosystems, with the caveats that image resolution must be adequate for identification of the species of interest, and that the vegetation canopy allows determination of where a plant is rooted. ...
As our understanding of ecological systems grows, natural resource management becomes ever more dependent on timely, accurate, and inexpensively-collected monitoring data to support management decisions. Vegetation cover, density, and frequency are abundance metrics used in resource management; however, frequency data can be collected more quickly than density data and with more repeatability and less sensitivity to inter- and intra-seasonal variation in plant morphology. Moreover, frequency is perhaps the best method for monitoring invasive species across extensive areas. A limitation to the use of frequency data is that plot size affects frequency. The optimal plot size is one that yields measurements suitably removed from 0 or 100% to allow detection of both upward and downward frequency trends, yet the optimum plot size cannot be known before sampling. We addressed this conundrum by developing SampleFreq software that facilitates frequency measurements from digital nadir images of any scale with up to 10 nested plot sizes within the confines of the image dimensions. We conducted accuracy and agreement tests of the software using both artificial populations and field plots. Using artificial population plots, accuracy across all users was 93.4% with a repeatability coefficient of 1.4%, indicating high precision. In a field test, SampleFreq and standard field data averaged a 3.4% difference, and were within approximately 10.5% of each other 95% of the time. From the same field test, SampleFreq repeatability coefficient was 6.7%, while the field method was 4.3%, illustrating that both methods have relatively high precision. Because SampleFreq has high potential accuracy, high agreement with field data, and high precision across a range of users, we recommend using SampleFreq with nadir digital images as a suitable alternative method for monitoring plant frequency.
In the southern United States, some landowners have established plantations of eucalyptus (Eucalyptus spp.) and are managing them on short rotations (<15 years) to provide wood for fiber and other potential uses. Establishment of short-rotation woody crops dominated by nonnative species has implications for resident fauna in the United States that are largely unknown. We compared avifauna abundance, diversity, and community composition in newly established Camden white gum (Eucalyptus benthamii) plantations with slash pine (Pinus elliottii) plantations of the same age and height (one to two and six to seven years old, respectively) in southwestern Louisiana, USA. Species richness, diversity, and community composition in newly established eucalyptus plantations and six- to seven-year-old pines were similar. More birds were observed, and bird detections varied less in eucalyptus plantations. Indigo buntings (Passerina cyanea) and other shrub-associated species were detected more often in eucalyptus stands. In contrast, species that inhabit herbaceous-dominated communities, such as eastern meadowlarks (Sturnella magna), or that were associated with a dense graminoid community (e.g., Bachman’s sparrow [Peucaea aestivalis]) were detected less often in eucalyptus. Overall, breeding bird communities in eucalyptus plantations one to two years postestablishment differed little from plantations dominated by slash pine.
Southern US landowners participating in forest certification programs sometimes use green tree retention in intensively managed pine (Pinus spp.) forests (IMPF) to promote structural diversity and to benefit wildlife species. However, the operational extent of green tree retention practices is poorly understood. Therefore, we classified land cover on 1187 South Central Plains IMPF management units (“MUs”; totaling 51245.7 ha), defined as contiguous, forested areas containing one or more IMPF patches, harvested and established as a cohort, plus associated green tree retention areas. For each MU, we calculated green tree retention levels and generated land cover pattern metrics describing MU composition and configuration. As expected given our sampling frame, MU land cover was dominated by regenerating clearcut (mean ± sd: 80.5% ± 14.3% of land cover) and green tree retention cover (mean 18.6% ± 14.2% of land cover). Retention cover consisted mostly of streamside management zones (mean 14.0 % ± 13.1% of land cover) buffering perennial and intermittent streams and stringers (mean 3.4% ± 4.3% of land cover) buffering ephemeral streams. Green tree retention land cover represented a substantial proportion of the IMPF landscape in the region and potentially enhances habitat conditions for many wildlife species.
Using natural nests of eight bird species, we provide one of the first multispecies tests for edge effects on reproductive success in a forested landscape. Our primary objective was to assess whether distance to the edge of recent clearcuts was related to nesting success in intact northern hardwood forests. Estimated nest success was generally lower for the two ground-nesting species than for the six canopy-nesting species. Brood parasitism was <3% for species which typically accept eggs of the Brown-headed Cowbird (Molothrus ater), and nest predation was the most common cause of nest failure. Probability of nest failure was influenced by distance to forest edge for the ground-nesting Hermit Thrush (Catharus guttatus) and Ovenbird (Seiurus aurocapillus), but not for six canopy-nesting species. For the Hermit Thrush and Ovenbird, nest success relative to decreasing distance to the edge was reduced during the nestling stage, but not the incubation stage. Nest density appeared to be higher in forest zones near the clearcut edge for ground-nesting and for several canopy-nesting species. Our data suggest that the effect of proximity to edge on nest success for ground-nesting species may penetrate 300 m into intact forest, while the effect of proximity to edge on nest density may penetrate farther. These data suggest that the creation of openings in forested landscapes reduces nest success and increases nest density for some species of migratory birds in a zone adjacent to the opening. This pattern supports the notion that "ecological traps" may exist for ground-nesting birds in areas near recently created forest openings. Because areas of contiguous forest (e.g., publicly owned forest) in the Upper Great Lakes remain relatively intact, they may serve as source habitat for regional songbird metapopulations.
As a result of changes in natural and anthropogenic disturbance regimes, the extent of early-successional forest across much of eastern North American is near historic lows, and continues to decline. This has caused many scientists to identify the conservation of early-successional species as a high priority. In this synthesis, we discuss the conservation implications of this loss of early-successional habitats using examples from the literature on songbirds. Early-successional “shrubland” bird species require conditions and resources present in recently disturbed sites. These conditions are ephemeral and change rapidly over time as sites become dominated by later-seral species. Historical disturbance regimes such as wind-throw, fire and flooding have been altered or suppressed in eastern forests through human activity such as conversion of forests to younger aged stands more resistant to wind, fire suppression and mesophication of fire-adapted communities, and suppression of beaver activity and flooding. Furthermore, anthropogenic disturbance has shifted over much of the region to types of land use that provide less shrubland habitat of lower quality than historically. Despite scientific evidence in support of this concern, there is still misunderstanding about the role of disturbance in maintaining biodiversity, and public opposition to management remains a challenge to conserving these communities. Contemporary approaches use natural disturbance regimes to inform management practices that employ historical agents where possible or surrogates when necessary to achieve desired future conditions defined on the basis of regional population or community status. Conservation of early-successional communities occurs within the context of other potentially conflicting ecological values, such as the conservation and enhancement of biologically mature forest. Recent findings, however, show shrubland habitat can augment diversity in forested landscapes by providing seasonal resources for mature-forest species, such as food or predator-free space for juvenile forest songbirds that seek out early-successional habitats during the transition to independence. Balancing the conservation of early-successional shrubland species with other, sometimes conflicting values is an active area of current conservation research. In some cases the conservation of shrubland birds can be coordinated with commercial activities like silviculture or maintenance of infrastructure (e.g. powerline corridors), although our work indicates that deliberate efforts expressly directed at conservation of early-successional shrubland species are more effective.
With limited resources for habitat conservation, the accurate identification of high-value avian habitat is crucial. Habitat structure affects avian biodiversity but is difficult to quantify over broad extents. Our goal was to identify which measures of vertical and horizontal habitat structure are most strongly related to patterns of avian biodiversity across the conterminous United States and to determine whether new measures of vertical structure are complementary to existing, primarily horizontal, measures. For 2,546 North American Breeding Bird Survey routes across the conterminous United States, we calculated canopy height and biomass from the National Biomass and Carbon Dataset (NBCD) as measures of vertical habitat structure and used land-cover composition and configuration metrics from the 2001 National Land Cover Database (NLCD) as measures of horizontal habitat structure. Avian species richness was calculated for each route for all birds and three habitat guilds. Avian species richness was significantly related to measures derived from both the NBCD and NLCD. The combination of horizontal and vertical habitat structure measures was most powerful, yielding high R-2 values for nationwide models of forest (0.70) and grassland (0.48) bird species richness. New measures of vertical structure proved complementary to measures of horizontal structure. These data allow the efficient quantification of habitat structure over broad scales, thus informing better land management and bird conservation.
Rates of nest predation for birds vary between and within species across multiple spatial scales, but we have a poor understanding of which predators drive such patterns. We video-monitored nests and identified predators at 120 nests of the Acadian Flycatcher (Empidonax virescens) and the Indigo Bunting (Passerina cyanea) at eight study sites in Missouri and Illinois, USA, during 2007–2010. We used an information-theoretic approach to evaluate hypotheses concerning factors affecting predator-specific and overall rates of predation at landscape, edge, and nest-site scales. We found support for effects of landscape forest cover and distance to habitat edge. Predation by Brown-headed Cowbirds (Molothrus ater) increased, and predation by rodents decreased as landscape forest cover decreased. Predation by raptors, rodents, and snakes increased as the distance to forest edges decreased, but the effect was modest and conditional upon the top-ranked model. Despite the predator-specific patterns we detected, there was no support for these effects on overall rates of predation. The interactions between breeding birds, nest predators, and the landscapes in which they reside are scale-dependent and context-specific, and may be resistant to broad conceptual management recommendations.
Declines of migratory birds have led to increased focus on causative factors for these declines, including the potential adverse effects of habitat fragmentation on reproductive success. Although numerous studies have addressed how proximity to a habitat edge, patch size, or landscape context influence nest survival or brood parasitism, many have failed to find the purported effects. Furthermore, many have sought to generalize patterns across large geographic areas and habitats. Here, we examined evidence for effects of edge proximity, patch size, and landscape context on nest survival and brood parasitism of grassland birds, a group of conservation concern. The only consistent effect was a positive association between edge proximity and brood parasitism. We examined effects of patch size on nest survival (37 studies) and brood parasitism (30 studies) representing 170 and 97 different estimates, respectively, with a total sample size of > 14000 nests spanning eastern North America. Nest survival weakly increased with patch size in the Great Plains, but not in the Midwestern or Eastern United States, and brood parasitism was inversely related to patch size and consistently greater in the Great Plains. The consistency in brood parasitism relative to nest survival patterns is likely due to parasitism being caused by one species, while nest survival is driven by a diverse and variable suite of nest predators. Often, studies assume that predators responsible for nest predation, the main driver of nest success, either are the same or exhibit the same behaviors across large geographic areas. These results suggest that a better mechanistic understanding of nest predation is needed to provide meaningful conservation recommendations for improving grassland bird productivity, and that the use of general recommendations across large geographic areas should only be undertaken when sufficient data are available from all regions.
Bottomland hardwood forests support an abundant and diverse avifauna, but area of this forest type has been reduced, and current projections indicate continued declines. We compared breeding bird abundance indices and species richness among bottomland hardwood stands ranging in width from ~50 m to >l,OOO m and enclosed by forested habitat. We also compared avian abundance indices and richness among stands enclosed by pine (Pinzls spp.) forest and stands enclosed by field-scrub habitats. Total species richness and species richness of Neotropical migrants were associated positively (P < 0.05) with stand width in all years. Total bird counts differed among width classes in all years, with counts generally greatest in width classes l,OOO m. Counts of Neotropical migrants differed (P < 0.05) among width classes in 1993 and 1995 and followed the same general trend as total bird count. Acadian flycatcher (Empidonax uirescens), blue-gray gnatcatcher (Polioptila caerulea), and red-eyed vireo (Vireo oZiwceous) were more abundant in smaller width classes (P < 0.05), whereas the opposite was true for white-eyed vireo (Vireo griseus) and northern parula (Purula americana). Probability of occurrence was associated positively (P < 0.05) with stand width for 12 species and negatively with stand width for 1 species. Total bird count and the counts of blue-gray gnatcatcher in 1995 and of northern cardinal (Car&n&s cardinalis) in both years were higher in field-enclose d stands (FES) than in pine-enclosed stands (PES). N o s pecies analyzed was more abundant in PES than in FES. We conclude that even narrow riparian zones can support an abundant and diverse avifauna, but that conservation of wide (~500 m) riparian zones is necessary to maintain the complete avian community characteristic of bottomland hardwood forests in South Carolina.
In six 8- to 11-year-old plantations of longleaf pine (Pinus palustris Mill.) near Aiken, S.C., responses of understory vegetation, light, and soil water availability and litterfall were studied in relation to pine thinning (May 1994), herbicidal treatment of nonpine woody vegetation (1995-1996), or the combined treatments (treatment responses described below are in absolute units). Treatment differences in fifth-year (1998) herbaceous species density were as follows: pine thinning > woody control = combined treatments > untreated (33, 30, 30, and 25 species per 40 m(2), respectively). Forb and grass covers were 13 and 8% greater, respectively, after pine thinning and 7 and 9% greater after woody control. Pine thinning stimulated a large increase in third-year gap fraction (0.26), short-term increases in soil water content (1%), and a reduction in pine litterfall by half (-120 g.m(-2) per year). Woody control had no effect on gap fraction, decreased litterfall of nonpine woody vegetation (-32 g.m(-2) per year), and stimulated season-long increases in soil water content (1-2%). The ranking of factors affecting herbaceous vegetation responses was as follows: light > soil water > herbicides > litterfall. Herbaceous species density and cover can be promoted in longleaf pine plantations by intensive thinning of pines and herbicidal control of non-pine woody vegetation.
Forest certification programs require management of stand-level habitat elements supported by up-to-date science. Coarse woody debris (CWD) and snags have shown potential for impacting diversity, although their contributions in pine systems are not always well documented. We reviewed the scientific literature for information on relationships between wildlife communities and these habitat elements, with particular emphasis on southern pine systems, and offer analyses of information gaps and research needs. There is a need to improve knowledge of the impact of silvicultural actions, including herbicide use, on snag and CWD dynamics, and to develop reliable predictive models connecting management to stand-level habitat features and associated wildlife communities. Multivariate analyses should be used in studies of community ecology and response to habitat characteristics. We encourage long-term experiments to increase the power of hypothesis testing and account for temporal variation in wildlife populations. Wildlife responses should be measured using demographic characteristics rather than mere density.
In the 1950s there were vast acreages of cutover forestland and degraded agricultural land across the South. Less than 2 million ac of southern pine plantations existed at that time. By the end of the 20th century, there were 32 million ac of southern pine plantations in the US South and this region is the wood basket of the world. The success story that is southern pine forestry was facilitated by the application of research results generated through cooperative work of the US Forest Service, southern forestry schools, state forestry agencies, and forest industry. This article reviews the contributions of applied silvicultural research in tree improvement, nursery management, site preparation, weed control, and fertilization to plantation forestry in the South. These practices significantly increased productivity of southern pine plantations. Plantations established in the 1950s and 1960s, which produced less than 90 ft3 ac−1 yr−1, have been replaced by plantations established in the 2000s, which may produce in excess of 400 ft3 ac−1 yr−1. Currently, southern pine plantations are among the most intensively managed forests in the world. Growth of plantations managed using modern, integrated, site-specific silvicultural regimes now can rival that of plantations of fast-growing exotic species in the Southern Hemisphere.
We compared habitat use by forest migrant songbirds during the breeding and post-breeding periods in four Missouri Ozark habitats: mature upland forest, mature riparian forest, 9- to 10-year-old upland forest, and 3- to 4-year-old upland forest created by clearcutting. Adult forest-ground species showed a decrease in abundance in all habitats during the post-breeding period, but hatching-year birds of one of the two forest-ground species were most abundant in early-successional forest during this time. Adults of the two forest-canopy species tended to increase in abundance in 3- to 4-year-old forest from breeding season to post-breeding season. During the breeding season, some forest species were detected with mist-nets in the two early-successional habitats, but infrequently or not at all with point counts in those habitats. Forest birds captured in early-successional habitats during the breeding season may have been nonbreeding floaters, or may have been foraging there from nearby territories in mature forest. Dense shrubs or young trees in early-successional forest may provide habitat for nonbreeding and post-breeding forest migrant songbirds in the Missouri Ozarks.
Riparian buffers can be valuable refuge areas for wildlife in otherwise homogeneous agricultural landscapes. Government sponsored programs like the Cropland Reserve Program generally require the planting of specifi c vegetative spe-cies during buffer restoration, although the effectiveness of such an approach when compared to restoration by volunteer species is unknown. We studied the effect of differences in vegetation structure on avian habitat in riparian buffer zones. A 25 m (82 ft) wide planted woodland buffer, 30 m (98 ft) wide grass, shrub, and woodland three-zone buffer, and a 9 m (30 ft) wide shrub buffer were evaluated for habitat potential using breeding-bird counts and vegetation surveys. Bird density and spe-cies richness varied with the structure of the vegetative communities present at the three sites. Avian species richness and total detections were higher in the three-zone buffer than in both the shrub and planted buffer, likely a result of the diversity of vegetation at the site. These data suggest that restoration of riparian areas by allow-ing fallow vegetation to recolonize is at the very least equally benefi cial to avian wildlife as is restoration by planting specifi c grass, shrub, and tree species. Buffer restoration by natural revegetation using this method could be recommended as an alternative to implementation by planting riparian species due to its simplicity and cost effectiveness.
Summary 1. Riparian trees regulate aquatic ecosystem processes, such as inputs of light, organic matter and nutrients, that can be altered dramatically when these trees are harvested. Riparian buffers (uncut strips of vegetation) are widely used to mitigate the impact of clear-cut logging on aquatic ecosystems but there have been few experimental assess- ments of their effectiveness. 2. Forests along 13 headwater stream reaches in south-western British Columbia, Canada, were clear-cut in 1998, creating three riparian buffer treatments (30-m buffer, 10-m buffer and clear-cut to the stream edge), or left as uncut controls, each treatment having three or four replicates. 3. We predicted that periphyton biomass and insect consumers would increase as buffer width decreased, because of increased solar flux. We used two complementary studies to test this prediction. 4. In one study, we compared benthic communities before and after logging in all 13 streams; a second study focused on periphyton and insect colonization dynamics over 6-week periods in each of four seasons in four streams, one in each treatment. 5. Photosynthetically active radiation, and mean and maximum water temperature, increased as buffer width narrowed. 6. Periphyton biomass, periphyton inorganic mass and Chironomidae abundance also increased as buffer width narrowed, with the largest differences occurring in the clear- cut and 10-m buffer treatments. 7. Photosynthetically active radiation, water temperature, periphyton biomass and periphyton inorganic mass were significantly greater in the 30-m buffer treatment than in controls during some seasons. 8. Synthesis and applications. We have shown that a gradient of riparian buffer widths created a gradient in light and temperature that led to non-linear increases in periphyton biomass and insect abundance. For example, Chironomidae abundance was generally greater in the 10-m and 30-m buffer treatments than in controls, whereas this was not always the case in the clear-cut treatment. This pattern may be due to the high sediment content of the periphyton mat in the clear-cut treatment, which potentially limited the response of some insects to increased food resources. Overall, our results indicate that uncut riparian buffers of 30-m or more on both sides of the stream were needed to limit biotic and abiotic changes associated with clear-cut logging in headwater, forested watersheds.
We conducted a 3-year field experiment to measure the frequency of bird movements through riparian buffer strips before and after harvesting of adjacent forest. Our study was conducted in the boreal mixed wood forest of Alberta and was designed to determine empirically whether songbirds use riparian buffer strips of forest connecting forest reserves as corridors and if they move along these buffer strips more frequently than they cross adjacent clearcuts. We used mist nets to obtain an index of the frequency of bird movement in the forest, and we observed bird movements across adjacent clearcuts for comparison. We predicted that the frequency of movement would be greater (1) in buffer strips after harvesting of adjacent forest than before harvesting, (2) in buffer strips than across clearcuts and, (3) in buffer strips than at control sites (lakeshore forest with no adjacent clearcuts). After adjusting for year-to-year variation in abundance, we found that capture rates increased significantly from pre- to post-harvest, but only for juveniles. Capture rates of adults decreased immediately after harvesting, probably because of the removal of an adjacent source of birds that previously moved through the lakeside forest. Movement rates of forest species in clearcuts were significantly lower than capture rates in the forest. The number of adults captured was positively correlated with the number of territories in the buffer strips, indicating that most birds captured were probably residents. The number of local territories was a poor predictor of juvenile captures, supporting the notion that juveniles were likely dispersing individuals. Our results indicate that buffer strips enhanced movements of juveniles (i.e., acted as corridors) and maintained movement rates of adults. Furthermore, there appeared to be a threshold distance between reserves below which birds may be less reluctant to fly across openings, making corridor use less important.
Habitat loss and fragmentation are recognized as primary drivers of biodiversity loss worldwide. To understand the functional effects of habitat fragmentation on bird populations, data on movement across gaps in habitat cover are necessary, although rarely available. In this study, we used call playback to simulate a conspecific territorial intruder to entice birds to move through the landscape in a predictable and directional manner. We then quantified the probability of movement in continuous forest and across cleared gaps for two forest-dependent species, the grey shrike-thrush (Colluricincla harmonica) and the white-throated treecreeper (Cormobates leucophaeus). Fifty-four playback trials were conducted for each species across distances ranging from 25 to 480 m in continuous forest and 15–260 m across gaps in a forest-agricultural landscape in southern Victoria, Australia. The probability of movement was significantly reduced by gaps in forest cover for both species. Shrike-thrushes were six times more likely to move 170 m in continuous forest than to cross 170-m gaps. The mean probability that treecreepers would cross any gap at all was less than 0.5, and they were three times less likely to move 50 m across a gap than through continuous forest. Both species displayed non-linear responses to increasing gap distance: we identified a gap-tolerance threshold of 85 m for the shrike-thrush and 65 m for the treecreeper beyond which individuals were most unlikely to cross. The presence of scattered paddock trees increased functional connectivity for the shrike-thrush, with individuals crossing up to 260 m when scattered trees were present. We conclude that gaps in habitat cover are barriers to movement, and that characteristics of the intervening matrix influence landscape permeability.
Conservation of biodiversity on forest landscapes dominated by plantations has become an increasingly important topic, and opportunities to maintain or enhance biodiversity within these forests need to be recognized and applied. Riparian buffers of mature forest retained along streams in managed forest landscapes offer an opportunity to enhance biodiversity across these landscapes. However, influence of buffer width and structure of adjacent plantations on habitat use by birds is not well understood. We modeled probability of occupancy, while accounting for variable detection probabilities, for 16 bird species of regional conservation importance in the Ouachita Mountains of Arkansas, USA. We examined occurrence of breeding birds in streamside management zone (SMZ) buffers embedded in three structural classes of pine plantation: young open-canopy, closed-canopy, and older thinned plantations. Our occupancy models included a positive association with SMZ width for nine bird species associated with mature forests. Models for three early successional species (prairie warbler [Dendroica discolor], white-eyed vireo [Vireo griseus], and northern bobwhite [Colinus virginianus]) included a negative association with SMZ width. Occupancy models for Acadian flycatcher (Empidonax virescens), summer tanager (Piranga rubra), pine warbler (Dendroica pinus), prairie warbler, and northern bobwhite also included structural condition of adjacent plantations, but most species did not appear affected by condition of surrounding plantations. We found diverse responses among species to width of retained SMZs and structure of adjacent plantations; some species apparently benefitted from SMZs >100 m wide, while others benefitted from narrow buffers. Furthermore, most species traditionally associated with mature forests were common in narrow SMZs, regardless of width. Thus, optimal width of SMZs relative to avian conservation depends on the species of greatest conservation interest.
From 1995 to 1999, we mist-netted birds in regenerating clearcuts within a primarily forested landscape of West Virginia and Virginia to determine the extent that both resident and migrant birds and their young use this type of early-successional habitat during the post-fledging period. Our primary objective was to document whether or not birds typically considered mature or late-successional forest breeders were present in the clearcuts and if they were there with their young. Four mist-nets were located in each of six different forest clearcuts ranging in age from 1 to 7 years post-cut (at time of study initiation) and in size from 8.2 to 13.4 ha. We caught 613 adult birds and 206 juvenile birds of 46 different species within these six different sites. Species typically associated with mature forest, such as the Worm-eating Warbler (Helmitheros vermivorus), Red-eyed Vireo (Vireo olivaceus), Black-and-white Warbler (Mniotilta varia), Wood Thrush (Hylocichla mustelina), and Ovenbird (Seiurus aurocapillus) were among the most commonly captured (adults, juveniles, and family groups). Seven Worm-eating Warblers originally color-banded on territories in adjacent mature forest were recaptured in clearcuts during the post-fledging period, four with dependent young. Although it was apparent that both the adults and young of species of forest-interior breeders were using regenerating clearcuts during the post-fledging period, we are unsure as to the exact reasons why, and, more importantly, whether these habitats enhance their survival.
Although use of corridors by some wildlife species has been extensively examined, use by bats is poorly understood. From 1 June to 31 August (2004–2005), we used Anabat II detectors to examine bat activity and species occupancy relative to forested corridors on an intensively managed forest landscape in southern South Carolina, USA. We compared bat activity among corridor interiors, corridor edges, and stands adjacent to corridors. We also compared models relating occupancy of bat species to site-level characteristics using an information theoretic approach. We identified 16,235 call sequences of 8 species and detected bat presence at 89% (n = 320) of sites sampled. Our results indicate higher occupancy rates for bats along corridor edges compared to interior corridor or adjacent stands. Although we found few differences among species with respect to site-level characteristics, occupancy of all bat species was positively associated with corridor overstory height and negatively associated with adjacent stand age. The presence of roads adjacent to corridors positively influenced occupancy of Eptesicus fuscus, Lasiurus seminolus, and Perimyotis subflavus. Our results suggest management practices designed to create and enhance corridors may represent an ecologically sound method for maintaining important bat habitat features (i.e., edge) across managed forest landscapes.
We compared habitat use by forest migrant songbirds during the breeding and post-breeding periods in four Missouri Ozark habitats: mature upland forest, mature riparian forest, 9- to 10-year-old upland forest, and 3- to 4-year-old upland forest created by clearcutting. Adult forest-ground species showed a decrease in abundance in all habitats during the post-breeding period, but hatching-year birds of one of the two forest-ground species were most abundant in early-successional forest during this time. Adults of the two forest-canopy species tended to increase in abundance in 3- to 4-year-old forest from breeding season to post-breeding season. During the breeding season, some forest species were detected with mist-nets in the two early-successional habitats, but infrequently or not at all with point counts in those habitats. Forest birds captured in early-successional habitats during the breeding season may have been nonbreeding floaters, or may have been foraging there from nearby territories in mature forest. Dense shrubs or young trees in early-successional forest may provide habitat for nonbreeding and post-breeding forest migrant songbirds in the Missouri Ozarks.
In the United States, intensively managed forests (IMFs) comprise approximately 9% (27.9 million ha) of total forest area. These forests are primarily in highly productive areas and are managed primarily for wood and fiber production. Intensively managed forests provide both opportunities and constraints for conservation of vertebrate biodiversity. A comprehensive review of these opportunities and limitations within the U.S. is lacking, so we reviewed effects of typical silvicultural management regimes within IMFs on terrestrial vertebrate species. The typical silvicultural regime in IMFs includes practices associated with establishing forest management units (stands), weed control, intermediate thinning, and final harvest. Effects of intensive forest management on vertebrate diversity are mostly indirect through habitat modification. Terrestrial vertebrate responses to intensive forest management are species-specific and directly linked to intensity and extent of habitat modification. Shorter crop tree rotations compress suc-cessional stages and limit development and recruitment of mature forest structures (e.g., snags, den/roost trees, coarse woody debris). During stand establishment, increased intensification of site preparation and weed control tends to result in lower vertebrate diversity. Generally, vertebrate diversity of intensively managed stands is progressively reduced after stand establishment as canopy closure occurs and sunlight to the forest floor is restricted, reducing vegetation structural complexity. However, intermediate management practices like thinning, which reopens the forest canopy, generally have positive or neutral effects on most vertebrate taxa. Final tree harvest removes the overstory and, predictably, vertebrate taxa depending on older or undisturbed forest conditions decline and early seral species increase. To ameliorate negative effects of final harvest on terrestrial vertebrate diversity, land managers have instituted various practices, including retaining habitat elements, protecting riparian zones and sensitive ecological areas, and limiting final harvest unit size as well as how soon an adjacent forest patch can be harvested. Juxtaposition and interspersion of forest stands of varying ages are important determinants of terrestrial vertebrate responses to intensively managed landscapes. A typical intensively managed landscape contains a variety of stand ages, forest types, and other features (e.g., streams, mature forest stands, set-aside areas) that provide habitat for a diversity of terrestrial vertebrate species. Landscape context has direct ramifications for terrestrial vertebrate diversity in intensively managed landscapes, with negative effects more pronounced in forests imbedded in agriculture or anthropogenic landscapes. Most field studies have been of short duration (<5 years) and localized (e.g., multiple stands in an area), hence we call for a greater commitment to longer-term research and monitoring replicated across landscapes. Significant research gaps include how to improve functionality of retained structures, riparian zones, and unique ecological communities, whether vertebrates are evolving or adapting to the rapid changes in habitat conditions characteristic of IMFs, and how landscape context, including spatial distribution of varying stand ages, affects vital rates of terrestrial vertebrate species (hereafter wildlife).
Forestry best management practices (BMP) recommendations for streamside management zones (SMZs) are based on limited data regarding SMZ width, partial harvests, and nutrient movements after forest fertilization. Agricultural fertilization is commonly linked to increased stream nutrients.
However, less is known about effectiveness of SMZ options for controlling nutrient movements after silvicultural fertilization. Diammonium phosphate and urea were applied to 12 subwatersheds in 3-year-old loblolly pine (Pinus taeda L.) plantations in the Virginia Piedmont. Three replicates
of four SMZ treatments were superimposed on 12 subwatersheds in a previous SMZ harvest sediment study (7.6-m SMZ, 15.2-m SMZ thin, 15.2-m SMZ, and 30.5-m SMZ). Surface, near-surface, subsurface, and stream water samples were collected monthly for 1 year and analyzed for nitrate (), ammonium (), and orthophosphate (ortho-P). Transected measurements from streamside to fertilized plantations allowed interpretations
of spatial nutrient measurements across SMZs. When compared with wider SMZs, 7.6-m SMZs had 3‐10× surface water , 3‐6× near-surface water , and 1‐2× more stream water . No significant differences were detected for
for any SMZ treatment. The 15.2-m SMZ thin had small but significant increases (2‐8×) in surface runoff for ortho-P relative to other SMZ treatments, perhaps because of increased surface water movement along thinning corridors. Across all SMZ treatments, comparisons of stream
edges with fertilized stands indicated reductions of 33‐98%, reductions of 68‐97%, and ortho-P reductions
of 70‐98%. A 39% rainfall deficit during the study influenced results, but conventional SMZs ≥ 15.2 m protected streams from fertilization nutrient increases.
Resident songbirds in slash pine (Pinus elliottii) stands in southeastern Georgia were related to forest regeneration method, stand age, and fire history and compared to those in timber types of mixed composition. In fallow areas and young plantations, bird community composition changed predictably with the structure of vegetation. Abundance and diversity were related to residual trees and snags providing habitats for bole- and canopy-feeders. Bird numbers and diversity generally were lowest in 1-year-old plantations, temporarily recovered in plantations 2-6 years old, then declined again until about midrotation. In pine stands past midrotation (16-28 years), bird communities were unaffected by origin of the stand (site-prepared and planted or naturally regenerated), stand age, or years since burning. The understory in burned pine stands on flatwoods soils consists mainly of a single stratum of low-growing shrubs that rapidly recover from burning, and birds showed no detectable responses to fire on a 5-year frequency. The bird community, dominated by canopy-feeders and ground-feeding insectivores, was poorly correlated with measurements of stand density, understory characteristics, and fruit availability. Wet sites with mixed hardwoods supported 17 species that were absent or rare in the pine type, and were important in maintaining bird diversity.
Species richness, bird abundance, bird species diversity and equitability were all higher in plots with snags than in snagless plots. Cavity-nesting birds occurred on plots with snags but were virtually absent from snagless plots. Other species used snags for foraging and perching and were more abundant on plots with snags. -from Authors
Strips of mature trees along intermittent or permanent streams, called streamside zones (SZ), often are retained to protect water quality and accommodate wildlife when forest stands are harvested. The authors investigated the effects on breeding birds of 3 SZ widths (narrow 15-25 m, medium 30-40 m, and wide 50-95 m) in young pine (Pinus spp.) plantation in E Texas. Bird abundance was generally positively related to SZ width. Narrow SZ were inhabitted mainly by species associated with young brushy stands and habitat edge. Bird species frequenting the wide zones were mostly those associated with mature pine-hardwood and bottomland hardwood stands in the South. Species found in the medium zones were a mix of species. -from Authors
Many studies on avian diversity and forest structure have focused on finer scale forest variables such as foliage height diversity, foliage diversity, foliage density, vertical distribution of vegetation and horizontal vegetation density. From a conservation and forestry operational point of view it would be of great interest if tree variables influenced directly by forestry management decisions also had significant influence on avian richness and abundance. The species, age and size of a tree are examples of such tree variables. A great number of studies also have focused on avian diversity indices to reveal relationships with vegetation variables. However, it may be more appropriate for foresters and conservation officers to operate with richness and abundance measures directly, because indices complicate interpretations on the relative importance of the two variables (richness and abundance) constituting the index. Fourteen managed temperate forests in Denmark were investigated for avian species richness and abundance and related to measures on different tree variables influenced directly by forestry management decisions. A rapid assessment method of avian richness and abundance was employed. It consisted of point-counts of bird richness and abundance within 1 km2 of forest. General linear models were tested by analyses of variance statistics to reveal the tree variables most important to avian richness and abundance. It was found that more old trees, more tree species and more tree size-classes correlated with more bird species and individuals. However, some variation in bird richness and abundance was also related to site quality and/or chance colonization. Moreover, it was shown that the guild of cavity-nesting birds correlated positively to age of tree stand. The potential number of bird species in Danish forest is similar to that in nearly pristine forest in Poland, and much larger than that recorded in any of the forests investigated. Together with the results above, this indicates a high potential for squeezing in more avian species in a higher quality forest from a biodiversity point of view. Modern Danish forestry affects tree variables influenced directly by forestry management decisions. Such tree variables have great influence on avian richness and abundance, but simple measures in forestry practices can be taken to enhance the conservation of bird richness and abundance.
Timber harvest is an important extractive, economic activity to many human economies, but it can be detrimental to ecosystem function and species viability therein by degrading and fragmenting forest habitat. Salamanders comprise a significant amount of forest community biomass, and given their sensitivity to environmental stressors, including those caused by timber harvest, they often serve as important indicators of declines in forest ecosystem function. Several studies have focused on the impacts of timber harvest on salamanders inhabiting perennial and intermittent streams, the findings of which have helped inform best management practices for timber harvest in the U.S. Ephemeral headwater streams and associated riparia account for a small fraction of the total landscape, yet these features are critical to the functioning of forested ecosystems; however, few studies have examined how timber harvest impacts salamanders in or near these areas. Our objective was to investigate the effects of three different silvicultural treatments, each involving different streamside management zone (SMZ) characteristics, on salamander communities in southeastern Kentucky hardwood forest ephemeral streams. Data were collected by regular checks of pitfall traps, coverboards, and transect searches. Using both pre- and post-harvest data, abundance estimates were acquired using binomial mixture models. Declines in some species of terrestrial and stream-breeding salamanders were detected, and were shown to be likely related to characteristics of the corresponding silvicultural treatment. We suggest that application of modest SMZ regulations to ephemeral streams would likely reduce or alleviate salamander declines in these important headwater areas.
Many studies have compared songbird nesting success between forest edge and interior, but few have addressed potential factors underlying variation in nest predation pressure in relation to edge. We examined the relative abundance and species richness of songbird nest predators and the abundance of Brown-headed Cowbirds (Molothrus ater) in forest edge and interior within a fragmented, agricultural landscape in central Missouri, USA. Avian predators and cowbirds were more abundant in forest edges. There were no differences in small- or medium-sized mammalian predator abundance between edge and interior. Almost twice as many snakes were captured in edge as in interior. Predator species richness was significantly higher in forest edge. Forest vegetation structure was very similar between edge and interior, suggesting that differences in predator abundance and species richness were not driven by variation in habitat structure. Nest predator distribution in relation to habitat edge may therefore depend on factors at larger spatial scales, such as landscape context. We suggest that in areas fragmented by agriculture, nest predator assemblages in forest edges may differ from those in forest interior. Edges may attract a greater number of predator species, and some nest predators may be more abundant near the edges of forest patches, although the trend does not apply across all predator taxa. Generalizations about nest predators and edges should thus be made with caution, and conservation plans should consider the composition of local nest predator assemblages in order to predict potential impacts on nesting birds in edge habitat.
In regenerating southern pine, maintenance of riparian zones (RZs) is a major land concession for soil and water protection and wildlife habitat enhancement. However, there are few data quantifying the volume and value of residual timber in such areas. We inventoried merchantable timber in nine RZs of three widths in sapling-class East Texas pine plantations. Present, discounted, and projected volumes and values of residual timber were determined. Average per-acre volumes of narrow, medium, and wide RZs were 337, 1438, and 2542 board feet (Doyle log rule) and 4.6, 8.2, and 7.2 cords, respectively. At US57.00 per thousand board feet for pine and hardwood saw timber, respectively, and US5.00 per cord for pine and hardwood pulpwood, respectively, average present per-acre values were US209.93 and US4.52, US34.38, respectively. Stumpage values at the time of harvest projected at 7% compound interest for 30 years ranged US10.66–US3547.54 per acre and for 80 years ranged US313.93–US104 499.95 per acre. The impact of these results on wildlife is discussed.
Breeding birds in 2 pine-hardwood stands (>30 years old) and adjacent clear-cuts (
Gaps in forest cover, created by agriculture, forestry, and other anthropogenic activities, are assumed to impede the movements of many forest songbirds. Little is known, however, about the reluctance of different species of birds to cross habitat gaps. We studied this by inducing birds in the post-fledging period to cross gaps of varying widths and to choose between routes through woodland or across open areas by attracting them to a recording of mobbing calls by Chickadees ( Parus atricapillus). In 278 experiments conducted in boreal forest and agricultural landscapes near Québec city, 157 birds or flocks of birds of five species were attracted. Overall, birds were twice as likely to travel through 50 m of woodland than through 50 m in the open to reach the recording. When given a choice of traveling through woodland or across a gap, the majority of respondents preferred woodland routes, even when they were three times longer than shortcuts in the open. However, species differed greatly in their response to gaps. Our results show that woodland links significantly facilitate movements of birds across fragmented landscapes.Es considerado que los claros en la cobertura forestal creados por la agricultura y otras actividades antropogénicas impiden los movimientos de muchas especies de aves paserinas. De cualquier manera, se conoce poco acerca de la renuencia de diferentes especies de aves a cruzar claros en los hábitats. Estudiamos esto, induciendo aves en el periodo post-juvenil a cruzar claros de diversas dimensiones y a escoger rutas a través de areas boscosas o abiertas, mediante la atracción por llamadas grabadas de parvadas de Parus atricapillus. En 278 experimentos conducidos en paisajes de bosque boreal y agricultural, cercanos a la ciudad de Quebec, 157 aves o parvadas de cinco especies fueron atraídas. En general, las aves fueron mayormente atraídas a viajar a través de 50 m de area boscosa que a través de 50 m de claro, para encontrar la grabación. Cuando se dió la opción de viajar a través de bosque o claro, la mayoría de las aves que respondieron prefirieron las áreas arboladas, aún cuando estos viajes fueron tres veces mas largos que atajos por las areas abiertas. Sin embargo, las especies respondieron de diferente manera a los claros. Nuestros resultados muestran que uniones de areas boscosas facilitan significativamente los movimientos de aves a través de paisajes fragmentados.
A map of ecoregions of the conterminous United States has been compiled to assist managers of aquatic and terrestrial resources in understanding the regional patterns of the realistically attainable quality of these resources. The ecoregions are based on perceived patterns of a combination of causal and integrative factors including land use, land surface form, potential natural vegetation, and soils. A synoptic approach similar to that used to define these ecoregions is also useful for applications of the map. Initial efforts to use the framework are at the state level of resource management; they center on aquatic ecosystems — mainly attainable ranges in chemical quality, biotic assemblages, and lake trophic state.
Five forest floor weights (0. ID, 20, 30, and 40 MgJha), three forest floor compositions (pine, pine-hardwood, and hardwood), and two seed placements (forest floor and soil surface) were tested in a three-factorial. split-plot design with four incomplete, randomized blocks. The experiment was conducted in a nursery setting and used wooden frames to define 0.145-mZ subplots. Forest floor composition had no significant effect on emergence or establishment of loblolly pine (Pinus taeda L.) seedlings. Numbers of emerging and established seedlings displayed a negative exponential relationship with forest floor weight (fit indices of 0.62 and 0.62, respectively). Seed placement significantly affected the number of emerging seedlings (forest floor > soil surface) and their survival (forest floor < soil surface). However. seed placement had no overall significant effect on the number of established seedlings because effects on emergence and survival essentially canceled out. Germ~nation of herbaceous seeds in the soil bank also displayed a negative exponential trend with forest floor weight (fit indices of 0.46 and 0.50 for the weight of grasses and forbs, respectively) and was not significantly affected by forest floor composition. Results indicate that forest floor composition is not a factor in the natural regeneration of the pine component of mixed pine-hardwood stands and suggest that when pine seed production is adequate, moderate amounts of forest floor material will improve pine seedling development because of suppression of herbaceous vegetation. Resume : Cinq masses de couverture morte (0, 10, 20, 30 et 40 Mglha), trois compositions de couverture morte (pin. pin-feuillus, feuillus) et deux positions des semences (couverture morte et
Summary There are five key reasons why biodiversity conservation should be considered a part of plantation management. (1) The plantation estate is large, and balancing various land management values with wood and pulp production is important when extensive areas of land are involved. (2) The locations and management of new plantations will affect the biota that currently exist in such landscapes. (3) Maintaining some elements of biodiversity within plantations can have benefits for stand productivity and the maintenance of key ecosystem processes such as pest control. (4) The retention (or loss) of biota in plantations is relevant to the formulation of ecological standards and the certification of plantations in many parts of the world. (5) Plantation forestry has a narrow and intensive management focus on producing a forest crop for a limited array of purposes. It will not meet future societal demands for a range of outputs from plantations (in addition to wood and pulp supply), and will not be congruent with the principles of ecological sustainability. This paper briefly reviews the biodiversity conservation values of Australian plantations. It shows that almost all work in Australian plantations, whether conifer or eucalypt, highlights the importance of landscape heterogeneity and stand structural complexity for enhancing biodiversity. Management of plantations to promote landscape heterogeneity and stand structural complexity and enhance the conservation of biodiversity will, in many cases, involve tradeoffs that will affect wood and pulp production. The extent to which this occurs will depend on the objectives of plantation management and how far they extend towards the more complex plantation forestry models that incorporate social and environmental values. We argue that the widespread adoption of plantation forestry that leads to homogenous stands of extensive monocultures will risk re-creating the array of negative environmental outcomes that have been associated with agriculture in many parts of Australia.
We assessed the status of early successional forest conditions for 33 eastern states within the New England, Middle Atlantic, Great Lakes, Central Plains, Coastal South, and Interior South subregions. We used Forest Inventory and Analysis surveys to analyze trends from 1946 to 1998. Dramatic regional differences occurred in distribution of early successional forests. The northeastern region had the least proportion of young forest (16%), followed by the north-central (24%) and southern (29%) regions. The least amount of young forest occurred in the Central Plains (15%) and New England (16%), whereas the greatest occurred in the pine-dominated Coastal South (32%). Differences also existed among individual states, ranging from 3% (Illinois) to 38% (Alabama). Long-term declines also were evident within the northeastern and north-central regions. Selective harvesting, fire suppression, urban sprawl, and cessation of agricultural abandonment contributed to the present imbalance in distribution of young forests. Private ownership predominates in the East and presents a significant challenge to provide young forests. Absence of proactive management on private lands may promote continued declines in early successional forest within many eastern areas.
We used artificial nests to examine predation in riparian buffer strips created by commercial clear-cutting and in unharvested control areas on industrial forestlands in eastern Maine. Nests in riparian buffer strips were depredated more often than those in intact riparian forests. This pattern was similar for both ground and shrub nests and for both trials. Predation rate for nests in control stands was 15%, compared to 31% in 20-40m wide buffer strips along tributary streams (P = 0.016) and 23% in 60-80m wide buffer strips along mainstem streams (P = 0.045). Predation rates were similar (P = 0.41) in mainstem and tributary buffer strips. Greater predation rates documented for nests in riparian buffer strips likely resulted from an elevated number and diversity of predators associated with the narrow, linear forest stands. Remotely-triggered cameras placed on a subset of nests revealed 6 species of nest predators. Predators identified at nests were mostly forest species and not species directly associated with riparian habitats. Red squirrels (Tamiasciurus hudsonicus) and blue jays (Cyanocitta cristata) were responsible for >50% of the identified depredations Black bears (Ursus americanus) were photographed only in tributary buffer strips and may have been using them to travel between larger forested stands. Increased predation of eggs and young probably reduces the nesting success of birds in riparian buffer strips. Managers should leave wide (≤150-m) buffer strips along riparian zones to reduce edge related nest predation, especially in landscapes where buffer strips are an important component of the existing mature forest.
The majority of the world's forests are used for multiple purposes, which often include the potentially conflicting goals
of timber production and biodiversity conservation. A scientifically validated management approach that can reduce such conflicts
is retention forestry, an approach modeled on natural processes, which emerged in the last 25 years as an alternative to clearcutting.
A portion of the original stand is left unlogged to maintain the continuity of structural and compositional diversity. We
detail retention forestry's ecological role, review its current practices, and summarize the large research base on the subject.
Retention forestry is applicable to all forest biomes, complements conservation in reserves, and represents bottom-up conservation
through forest manager involvement. A research challenge is to identify thresholds for retention amounts to achieve desired
outcomes. We define key issues for future development and link retention forestry with land-zoning allocation at various scales,
expanding its uses to forest restoration and the management of uneven-age forests.
The southern United States has significant area in managed pine (Pinus spp.) stands that contribute to terrestrial biodiversity via maintenance of forested areas, varied silvicultural practices resulting in diverse plant communities, stands in multiple successional stages interspersed with mature natural forests, and reduction of pressure on natural forests for wood products. However, conservation value of managed forests is dependent on factors such as product target, landscape context, management intensity, rotation length, stocking density, and ownership philosophy. Potential limitations include loss of natural forests, reduction in dead wood, constraints on stand structure, age and size of plantation trees, and economic pressure to increase management intensity. We recommend that landowners develop plans, including metrics for gauging progress, to cost-effectively manage for biological diversity within working forests and communicate outcomes to stakeholders. Forest certification systems offer a formalized approach for meeting biodiversity goals and demonstrating accomplishments.
We analyzed 2 yr of bird population data in streamside management zones (SMZs) of three widths (50 ft, 100 ft, and 164 ft), adjoining ≤5 yr old pine plantations, and mature riparian areas in the Georgia Upper Coastal Plain. We evaluated relationships between SMZ width and bird abundance and density. Breeding and wintering avifaunal abundance were greater in SMZs than in the surrounding pine plantation. Breeding forest interior birds and forest interior neotropical migrant species were abundant in the mature forest control, but were essentially absent in SMZs and pine plantations. However, SMZs did provide habitat for an abundant avifauna community including several interior-edge and edge species not found in the pine plantations. Avian abundance was similar among SMZ widths, although densities were highest in the narrow SMZs. Forest managers should regard SMZs as important for maintaining avifauna abundance and diversity across pine dominated landscapes. South. J. Appl. For. 19(4):166-169.
Although clearcuts traditionally have been regarded as detrimental to birds associated with mature-forest, recent evidence suggests that during the post-breeding period regenerating clearcuts can provide habitat for many avian species associated with mature-forest. We examined use of regenerating clearcuts by mature-forest birds during the post-breeding period and evaluated the degree to which birds were sensitive to patch characteristics. From 15 June to 16 August in 2002–2003 we mist-netted and banded birds nine times each year in 12 regenerating hardwood clearcuts (4–7 years post-clearcut) that represented small (4.0–9.3 ha) and large (13.3–18.1 ha) clearcuts in southeast Ohio, USA. Nine nets were systematically deployed within each clearcut and placed 20, 50, and 80 m from mature-forest edges. At each net location, we measured habitat characteristics and sampled arthropod and fruit resources two-weekly. During the post-breeding period we captured 1648 mature-forest birds of 32 species, and several classic forest-interior species were among our most commonly captured species. Seventy-one percent of mature-forest captures were juveniles, which suggests that habitat provided by regenerating clearcuts may play an important role in post-fledging survival. Most post-breeding individuals avoided edges, and instead heavily used the clearcut interiors. Paradoxically, juveniles and post-breeding adults also avoided large clearcuts, and capture rates were up to four times greater in small than large regenerating clearcuts. Overall, our results suggest that regenerating clearcuts may be important resources for mature-forest birds during the post-breeding period, and forested landscapes containing a mosaic of successional stages may hold the most conservation promise for mature-forest birds.
Streamside management zones (SMZs), composed primarily of hardwoods in the southeastern United States, provide habitat diversity within intensively managed pine (Pinus spp.) plantations. However, effects of SMZ width and adjacent plantation structure on riparian wildlife communities are poorly understood. Therefore, during 1990–1995, we examined small mammal communities within 5 SMZ width classes (1–20 to >100 m) embedded within three types of pine plantations (young, open canopy; closed canopy; and thinned) and three natural riparian stands in the Ouachita Mountains of Arkansas, USA. We captured small mammals for 10 consecutive days each February using four to six traplines each consisting of nine trap stations with three snap traps at each station. We estimated relative abundance [catch-per-unit-effort (CPUE)], species richness, species diversity, and species evenness for all captures and captures just along the stream course. Within the SMZ/plantation settings and three natural stands, we captured 1701 small mammals of 11 species in 114,285 trapnights. Golden mice (Ochrotomys nuttalli), southern short-tailed shrews (Blarina carolinensis), and Peromyscus spp. comprised 88% of all captures. Our study suggests that narrow (≤20 m wide) SMZs in managed pine forests tend to have higher small mammal abundance and species richness than wider SMZs. Additionally, species richness and CPUE was greater in SMZs within young, open canopy and thinned plantations versus closed canopy plantations. Plantation structure appears to influence small mammal community structure within SMZs more than SMZ width. Shortening the amount of time plantations spend in closed canopy conditions would likely improve habitat conditions for small mammals existing in SMZs within intensively managed pine landscapes. Streamside management zones in the South designed to meet voluntary water quality standards are likely sufficient for small mammal conservation.
We studied six pine plantations in coastal South Carolina to determine the influence of clearcutting with corridor retention on small mammal abundance, richness, and diversity. Small mammals were live-trapped in recently clearcut stands that retained pine corridors 100 m in width and in adjacent pine plantations, 20–23-years-old. We compared small mammal communities between harvested stands with corridors and non-harvested pine stands. We captured 1158 small mammals, representing 844 unique individuals and seven different species in 94,080 trap nights. Rodent abundance, richness, and diversity indices were greater in harvested stands with corridors than in non-harvested pine stands. The early successional habitat created by clearcutting was used by many small mammal species, including cotton rats (Sigmodon hispidus) and marsh rice rats (Oryzomys palustris). Species composition of small mammals within the corridor habitats was similar to that in the non-harvested pine stands. The inclusion of corridors in pine plantation management enhances habitat diversity and ecosystem maintenance and contributes to local diversity of the small mammal community.
Agricultural land-use changes in Europe have taken two opposing directions: towards agricultural intensification or land abandonment. While in the Mediterranean region land abandonment is a main cause of avian diversity decline, in northern Europe species diversity often increases with successional age. We examined the hypothesis that the biogeographic origin of the avifauna determines whether abandonment brings conservation benefits or detriment by studying the bird community of agricultural land in northern Spain, at the boundary of the Mediterranean and Eurosiberian regions. Using a successional gradient, we examined landscape-scale effects of agricultural abandonment on birds during the breeding and non-breeding seasons.The trend in avian diversity with successional stage differed little between Mediterranean and Eurosiberian species in winter. In the spring, however, there was an increase in diversity with stage in abandonment for Eurosiberian birds but not for Mediterranean species. Analysis of individual species showed a preference among Eurosiberian birds for more wooded habitats whereas Mediterranean birds preferred open areas and shrubland.The introduction of agricultural policies to geo-political units that do not coincide with eco-regions cannot be assumed to bring uniform conservation benefits. In the Mediterranean region, agricultural mosaics of low intensity cultivation maintain the highest diversity of priority bird species. Agricultural land abandonment should not be assumed to benefit conservation.
The ability to move across and perhaps exploit resources in adjacent habitats may also allow a species to persist in marginal habitats until a better territory is found. Understanding how animals respond to the distribution of forest remnants may be useful in combining conservation efforts with landscape harvest designs. Studies have examined movements of birds within permanently fragmented habitats, but movement patterns may differ in temporarily fragmented landscapes. I examined the frequency of movements across river and forest-clearcut edges for several habitat and nesting guilds and individual species. Movements were almost four times higher at clearcut edges than river edges and were dominated by forest generalists, open-edge and ubiquitous species across both edges particularly those nesting in deciduous trees. Forest interior species were rarely observed crossing either boundary. Movements were positively related to abundances in buffers and negatively related to buffer width for deciduous tree nesters and those species associated with open-edge habitats. High movements in the narrow buffers suggests that these species incorporate this edge habitat as part of their territories. For forest specialists that are unwilling to cross-habitat boundaries, retaining wide buffers may provide valuable connections between unlogged patches in addition to breeding habitat. Narrow buffers that do not provide suitable habitat to support most forest-dwelling species may function as foraging sites or travel corridors that offer more protection from predators than flying across open spaces.
Streamside management zones (SMZs) in the Ouachita Mountains of Arkansas and Oklahoma are frequently established along headwater ephemeral and intermittent streams to protect water quality, provide wildlife habitat, and increase landscape diversity. To better understand the function of these riparian forest corridors, we characterized the tree density and composition, forest floor mass, and downed woody debris volume within SMZs located in undisturbed, mature, upper mid-slope shortleaf pine stands and then compared these attributes to those in upland portions of these stands. In addition to evaluate the impact of upland forest harvesting on these riparian corridors, we compared the amounts and distribution of forest floor, downed woody debris (DWD), snags, and windthrows in SMZs within shortleaf pine stands that had been clearcut, had a shelterwood harvest, and had no recent management activity (uncut stands). Total tree and hardwood basal area was significantly higher (4.4 and 4.2 m2 ha−1) while forest floor mass was significantly lower (0.5 kg m−2) in the SMZs than in the upland portion of the undisturbed stands. Five years following the reproduction cuttings tree basal area, DWD volume, and forest floor mass within SMZs did not significantly differ among stands that had or had not been harvested. Snag density was significantly lower within SMZs that occurred in clearcut stands compared to those in the uncut or shelterwood stands. Harvesting activities that retain few or no residual trees appear to increase the degradation of snags. This study provided evidence that clearcutting may also increase the risk of windthrow in SMZs as well. There was little difference in the distribution of forest floor within SMZs regardless of whether the stand was harvested or the type of harvesting that occurred in the stand. However, DWD amounts were higher near the SMZs edge than in the interior of the SMZs with the greatest differences in distributions in stands that were clearcut.
Standing dead trees, or snags, are natural components of forest stands and are important habitats for many wildlife species. We examined snag dynamics from 1982–1990 on 140 0.1 ha plots in the upper Piedmont of South Carolina. Plots were established in 10 stand type–age class combinations. Mean snag density was 28.4 snags/ha and mean snag diameter (DBH) and height were 20.3 cm and 9.9 m, respectively. Highest snag densities occurred in hardwood stand types; pine plantations had lower (p≤0.05) snag density than all other types. Within a particular stand type, snag densities, recruitment rates, and loss rates generally were lowest in the oldest age classes. Intermediate age classes of all stand types had higher snag densities and snag turnover rates than younger or older stands within that type. Young pine plantations had the lowest recruitment rate (x̄=1.79 snags/ha/year) and old pine plantations had the lowest loss rate (x̄=1.59 snags/ha/year) of all the stand type–age class combinations. Although twenty species of snags were observed, five species/species groups, shortleaf pine (Pinus echinata), red oaks (Quercus spp. ), white oaks (Quercus spp. ), loblolly pine (P. taeda), and yellow poplar (Liriodendron tulipifera), occurred most frequently. Snag DBH and cavities/snag were not significantly correlated. Stage of decay for cavity and noncavity snags (r=0.97 and 0.83, respectively; p≤0.05) and number of cavities/snag (r=0.78) increased with year since snag recruitment. Ten snag species contained cavities (x̄=0.1 cavities/snag), but shortleaf pine accounted for 56% of the cavity years observed (x̄=0.18 cavities/snag). Three other softwood species also contained equal to or above average numbers of cavities/snag. Approximately 30% of all snags fell within two years of recruitment, 55% within three years, and 95% within six years. Snag longevity was independent of diameter class (p=0.67). Hardwood snags, especially those in upland hardwood stands, appeared to persist longer than pine snags. As pine plantations managed on short rotations (<25 years) and older-aged stands (>50 years) of all types may not provide abundant snags in the South Carolina Piedmont, the potential for wildlife habitat might be enhanced if older, larger diameter trees, especially softwood species, are retained or designated as snag replacements.
In the Pacific Northwest (PNW) region of the contiguous United States, retention of live (green) trees in harvest units is an integral part of forest management practices on federal lands, yet the ecological benefits that result from various levels or patterns of retained trees remain speculative. The Demonstration of Ecosystem Management Options (DEMO) study was established to address these informational gaps. The experimental design consists of six treatments, each 13 ha in size, replicated at six locations (blocks) in western Washington and Oregon. Treatments represent strong contrasts in retention level (15–100% of original basal area) and pattern (trees dispersed vs. aggregated in 1-ha patches) in mature Douglas-fir (Pseudotsuga menziesii) forests. A wide variety of ecological responses and public perceptions of visual quality have been examined; this paper provides a comprehensive review of the short-term (1–7 years) results of these studies. Level of retention had a strong effect on many responses. At 15% retention, regardless of pattern, microclimate, ecological responses, and public perceptions of visual quality did not differ from those measured in the “clearcut” areas of aggregated treatments. In contrast to level of retention, pattern of retention had limited effect on most measures of biological response. Small changes within forest aggregates were balanced by large changes in adjacent harvested areas, thus on average, responses within aggregated treatments were comparable to those in dispersed treatments. Nevertheless, retaining trees in 1-ha aggregates provided several benefits over dispersed retention. Aggregates greatly reduced damage to and mortality of residual trees (particularly at lower levels of retention) and provided short-term refugia for forest organisms sensitive to disturbance or environmental stress (e.g., bryophytes and late-seral herbs). However, aggregates were susceptible to edge effects (e.g., elevated light and temperature), which may compromise their ability to serve as sources for recolonization of adjacent harvested areas. Collectively, our findings suggest that retention levels >15% are needed to effectively retain sensitive plants and animals, ameliorate harsh microclimatic conditions, and gain public acceptance of retention harvests in these forests. A combination of relatively large (≥1 ha) aggregates and dispersed trees at levels considerably greater than current minimum standards in the PNW may be the most effective strategy for sustaining a broad array of forest values in managed stands.