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Home , Longleaf pine, Plantation, Savanna

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P R A R U TME U LT Service NT OF AGRIC PNW Pacific Northwest Research Station

Inside Beginnings in a Planted Forest Setting...... 2 The Stands, the , and the Strategies...... 3 More Sun Isn’t Enough...... 4 Facilitating Savanna Restoration...... 5 FINDINGS issue one hundred fifty two / may 2013 “Science affects the way we think together.” Lewis Thomas Restoring a Disappearing : the Longleaf Savanna

IN SUMMARY Longleaf pine (Pinus palustris) savannas of the southeastern United

TimHarrington States contain some of the world’s most diverse communities, along with a unique complement of . Their traditionally open structure and rich under- story of grasses and herbs were crit- ical to their vigor. However, a long history of land-use practices such as , farming, and fire exclusion have reduced this once-widespread ecosystem to only 3 percent of its original range. At six longleaf pine plantations in South Carolina, Tim Harrington with the Pacific Northwest Research Station and collaborators with the Southern Research Station used various treatments (including pre- scribed burns, , and herbicide applications) to alter the crew collect data from a study site in a longleaf pine plantation in South Carolina. forest structure and tracked how successful each one was in advanc- “In ‘pine barrens’ most of the day. acres of the American South, from the Carolinas ing savanna restoration over a 14-year period. They found that typi- Low, level, sandy tracts; the to Texas. But when John Muir made his southeast- ern trek in 1867, the longleaf pine-wiregrass eco- cal planting densities for pro- wide apart; the sunny spaces between system he saw was already slipping away. duction in plantations create dense full of beautiful abounding grasses, understory shade that excludes many , long, wand-like , At least a century before, European settlement native herbaceous species impor- had gradually transformed the natural . saw palmettos, etc., covering the tant to savannas and associated Land was cleared for and other crops. As ground in garden style. Here I saun- wildlife. The scientists found that well, livestock grazing, urban development, fire although tree thinning alone did not tered in delightful freedom…” suppression, and the which result in sustained gains, a combina- —John Muir, 1867 harvested pine to maintain the wooden ships tion of controlled burning, thinning, of the day—took an ever-growing toll on the and herbicide treatments to reduce airy longleaf pine . Commercial logging, he longleaf pine (Pinus palustris) was woody plants was an effective strat- which began in the early 1700s, also drove the once one of the most abundant egy for recovering the savanna eco- steep decline. So prized was Pinus palustris for in the United States. Its realm—vast system. The scientists also found that T its straight, -hued timber and its superior savannas shaped by thousands of years of these efforts must be repeated peri- pitch and resin that forest botanist Roland Harper frequent fires set by lightning and Native odically for enduring benefits. in 1928 claimed the longleaf had “probably more Americans—stretched across some 90 million uses than any other tree in , if lands, mainly in southeastern coastal areas. the Pacific Northwest Research Station in not in the whole world.” These patches harbor nearly 200 types of Olympia, . (including listed species such as the red- When the Great Southern Company In 1993, when Harrington was a professor at cockaded ) and hundreds of other ran out of longleaf pine logs and shut down the University of Georgia, he began long-term animal species. Mature longleaf pine savan- in 1938, had already turned to cul- research on strategies for restoring this unique nas also contain some of the most diverse tivating other, faster growing types of trees. ecosystem. His continuing work, with multiple plant communities worldwide, with up to 40 Today fewer than 2 million acres of longleaf collaborators, has led to significant insights species per square yard. “That’s richer than pine savanna and their associated about how a waning biological system might most places in the American West,” notes (about 3 percent of the original expanse) be brought back from decline, but also about Tim Harrington, a research with survive. About half of this exists on public its remarkable complexity.

BEGINNINGS IN A PLANTED FOREST SETTING estoring any ecosystem requires and fire suppression upset this balance and understanding the elements and opened the way for such as , structure that enable it to function and hickories, and black cherry to move in, along R TimHarrington remain healthy. Historically, longleaf pine with the fire-intolerant loblolly pine.” These savannas had widely spaced trees of varying changes led to closed-canopy stands intermin- ages, from seedlings to centuries-old trees. gled with hardwoods and a tangled understory The understory included a rich variety of of woody shrubs and vines. The dense shade herbs and grasses dominated by wiregrass and deep accumulation of forest litter choked and bluestem. These species depend on out plant species critical to the longleaf pine regular burning to stimulate flowering and community. So, where to start in rebuilding production. They provide important a savanna composed of scattered trees and a food and cover for many birds, , and rich herbaceous understory? small mammals. Harrington turned to the 200,000- “Native grasses and longleaf pine perpetuated Savannah River Site, a U.S. Department of each other with the help of fire,” Harrington Energy defense facility near Aiken, South explains. “Longleaf pine needles, up to 18 Carolina, that also serves as a National inches in length, fall as they mature and accu- Environmental Research and a setting mulate as a drape over the understory veg- for ecological research. “We set up study sites etation. Along with the native grasses, these in longleaf pine plantations on former native ‘flashy’ fuels supported frequent, fast-moving savanna lands where loblolly pine had seeded Hardwoods and shrubs often crowd the under- fires that reduced woody and kept in naturally and was harvested in the 1980s,” story of young longleaf pine plantations. growing space open for wiregrass and new Harrington says. longleaf pine seedlings.” “Plantations such as these have successfully The ecosystem was well-adapted to the produced fiber and wood, but restoring the Purpose of PNW Science Findings underlying , which evolved from ancient savanna demands different practices,” he To provide scientific information to people who ocean beaches. “Grasses and nitrogen-fixing explains. For example, tree-farming opera- make and influence decisions about managing legumes kept the system in a relatively fertile tions use machines to prepare the and plant land. state; without them longleaf pine growth can straight rows of seedlings at densities often PNW Science Findings is published monthly by: be stunted,” he continues. “But tillage farming exceeding 600 trees per acre. “In the past, Pacific Northwest Research Station USDA Forest Service P.O. Box 3890 KEY FINDINGS Portland, Oregon 97208 Send new subscriptions and change of address • Thinning 8- to 11-year-old pine plantations to about 250 trees per acre (half their information to: original planting density) increased the diversity of herbaceous plants by six to eight [email protected] species and expanded their coverage by 13 to 22 percent for up to 8 years. However, Rhonda Mazza, editor; [email protected] these increases were nearly undetectable by year 14 because of increasing shade and root competition from overstory pines and understory shrubs and hardwoods. C. Hugh Luce, layout; [email protected] Science Findings is online at: http://www. • When and shrub densities were reduced with herbicide treatments, fs.fed.us/pnw/publications/scifi.shtml increases in diversity and cover were still evident 14 years To receive this publication electronically, after treatment. change your delivery preference here: http://www.fs.fed.us/pnw/publications/subscription. • A combined treatment of pine thinning and herbicides to control woody plants led shmtl to the largest and most prolonged increases in the abundance and diversity of birds. Small mammal populations increased with either pine thinning or woody plant United States Forest control; the beneficial effects from thinning lasted 5 to 7 years after treatment. Department Service of Agriculture

2 mortality of newly planted pine seedlings could approach 50 percent, but today’s survival rates are much higher, leading to tree densities up to 500 per acre. That’s about 10 times the levels on historical longleaf pine savannas,” he con- tinues. This crowding hastens the canopy clo- RobertSimmons sure that deprives savanna understory species of sun and gives a competitive edge to shade- tolerating woody shrubs and hardwoods. Harrington and his colleagues wanted to better understand the key processes limiting the abun- dance and diversity of herbaceous understory plants important to the savanna community and how management techniques could intervene to restore the ecosystem. Between 1994 and 2008, the researchers experimented with methods for manipulating the canopy layers of the forest and tracked how successful each one was in advancing restoration. For this study, prescribed fire was applied every 3 to 5 years to control growth of woody vegetation other than pine and reduce accumulations of needlefall, which prevents growth of herbaceous vegetation.

THE STANDS, THE PLANTS, AND THE STRATEGIES e had three basic research ques- on the plots. “The understory included about Further investigations on the effects of can- tions,” Harrington explains. 265 herb and woody species, with the cov- opy shading and root competition revealed “W “Given periodic applications erage of each group being roughly equal,” more detailed impacts on plant processes of of prescribed fire, first, how did pine thinning Harrington says. “Surprisingly, many of the about 20 different understory species, such influence the abundances of hardwoods and most common savanna species were still as flowering, seed production, and seed via- shrubs? Second, to what degree did herbicide there—but often at surprisingly low abun- bility. “In one case, an herbaceous species treatments reduce these target plant groups, dances.” produced more where all pines had and how long did the effect last? And, third, been removed, but the seeds had reduced “After 3 years, the canopy had expanded sig- how did these changes in the plant community viability,” Harrington notes. “More than nificantly over the plots where only moderate impact the diversity and numbers of herba- anything else, our studies demonstrated just thinning had occurred, and the developing ceous species?” how dynamic the system was, with all the shade gradually reduced the understory plant different life histories of the different spe- The six selected study sites had dense stands cover. In general, the abundance of herbs cies playing out and interacting within the of 8- to 11-year-old longleaf pines interspersed corresponded to the level of thinning around changing environment.” with many hardwoods. To set the stage for the any given plot,” Harrington says. experiments, a prescribed burn took place in 1994 (and again in 1998 and 2003) to reduce woody plants and encourage the fire-depen- dent germination of seeds from desirable her- baceous species.

Each site was divided into four treatment plots TimHarrington of roughly 7 to 17 acres to enable tracking of the responses of plant and animal species. In one-fourth (6) of the plots, no other interven- tions besides burning occurred. In a second group, about half of the longleaf pines were thinned manually, to achieve uniform spacing of about 250 trees per acre. In the third group of plots, workers applied several herbicide treatments to eliminate (as much as possible) nonpine woody vegetation such as vines, shrubs, and hardwoods. The fourth set of the plots received a combination of thinning and herbicide treatments. At the outset of the study, the researchers car- ried out baseline surveys of the plants present A technician estimates cover and species composition of the understory vegetation.

3 MORE SUN ISN’T ENOUGH he vegetation measurements following years 5, 8, and 14 showed that in plots 18 T that were thinned, the diversity of her- baceous plants increased by six to eight spe- Treatment cies and overall herbaceous cover rose by 13 16 to 22 percent. Although these gains lasted up Pine thinning to 8 years, by year 14, they were nearly unde- 14 Woody control tectable, and by the study’s end, there was little difference between these once-thinned plots and the nonthinned ones. 12 “Reducing the density of the pines without using herbicides gives the woody shrubs 10 and hardwoods a big advantage; opening up the canopy provides more sun exposure 8 and allows them to explode in growth, so Increase the understory herbs eventually lose out,” Harrington says. “In fact, herb species on 6 these plots actually dipped below their start- ing numbers by year 14, underscoring how 4 detrimental shade is for them.” However, in plots that were thinned and treated with her- bicides, the diversity and total area covered 2 by herbs increased and held throughout the 14-year period because of sustained cutbacks 0 in woody encroachment. Cover Number Cover Number (percent) of species (percent) of species There were parallel findings with respect to wildlife. In separate research carried out by Year 8 responses Year 14 responses University of Georgia professor Karl V. Miller Increases in cover and number of herbaceous species 8 and 14 years after pine thinning and non- from 1996 to 2003, the diversity of birds, pine woody control. By year 14, the gains had diminished in thinned plots. small mammals, amphibians and reptiles on the study sites was tallied and rechecked annually. Preliminary analyses indicate that were prolonged, persisting up to 7 years after and to the greater plant species richness in either thinning or woody control increased the treatments. these stands,” Miller says. However, benefits the abundance and diversity of songbirds, due to thinning lasted only 5 to 7 years after Similar patterns for small mammals such as including several Neotropical migrants, for treatment because by then the tree cover had shrews, mice, and voles also were observed. about 2 years—an effect that quickly waned returned to pretreatment levels. For amphib- “The gains were due in part to a higher and disappeared by year 8. When treatments ians and reptiles, there appeared to be no abundance of left on were combined, modest increases in the changes related to the treatments. abundance and diversity of populations the ground, compared to unthinned areas, Tim Harrington

Different management treatments led to very different understory conditions 17 years into the study. The study site on the left received periodic burning. The study site on the right received periodic burning plus pine thinning and non-pine woody control in years 1 and 2, respectively, of the study.

4 FACILITATING SAVANNA RESTORATION he findings point to two possible strate- gies for managing longleaf pine planta- LAND MANAGEMENT IMPLICATIONS T tions to facilitate savanna restoration. Thinning pines and hardwoods at an early stage of development and again later when the • Planting longleaf pines is essential in savanna restoration, however; typical plantation canopy has expanded to cover more than half densities (>600 trees per acre) create excessive shade and root competition for herba- the stand area may provide a reasonable com- ceous plants, reducing their abundance and species diversity. This in turn diminishes promise between production of wood products wildlife , resulting in fewer birds and small mammals. and savanna restoration, in Harrington’s view.

An alternative approach would employ a • Active management to regulate the density of overstory pines and limit abundance of combination of treatments. Fewer seedlings other woody plants with appropriate use of prescribed fire and herbicides will acceler- would be planted in the first place followed ate development of a savanna community structure composed of widely spaced pines by periodic burning, more aggressive thin- and a vigorous and diverse understory of herbaceous species. ning, herbicide control of woody vegetation, and even planting of selected savanna species. “These steps are important to transform a cur- • Woody debris created by the pine thinning provided an important habitat feature for rently fire-resistant ecosystem into one that several and amphibian species. The debris facilitated travel by the small verte- perpetuates and is perpetuated by frequent, brates through the dense of vegetation that developed in the absence of natural low-intensity fires. But regardless of the man- or prescribed fire. agement system, the dynamic canopy develop- ment of young pine and hardwood stands is likely to necessitate repeated treatments of • More birds were observed in pine stands that received combined thinning and woody pine thinning, woody control, and prescribed control treatments, creating open canopies similar to those of mature longleaf pine for- fire to fully restore and maintain a vigorous est maintained by frequent low-intensity fires. herbaceous community,” explains Harrington. John Blake is the assistant manager for Forest Service supported research at the Savannah levels in the recovery standard for the endan- scribed burning (2013) was carried out on the River Site where Harrington’s experiments gered red-cockaded woodpecker. six study sites to see if these treatments will are installed: “Tim’s work has helped to refo- re-stimulate increases in the diversity and “Longleaf pine seedlings are now generally cus managers and researchers on the critical cover of herbaceous species. planted at lower densities (<500 trees per importance of overstory density management acre), which delays or prevents crown closure and the impacts of woody plants in the under- and associated loss of herbaceous species. On “What thrills me most about the story as major constraints on restoration of existing pine plantations, more vigorous thin- native savanna grasses and forbs. Prior to his longleaf is how the pine trees sing. ning to lower densities is occurring to promote studies, the prevailing paradigm was that one Even in the fragments you can hear establishment of herbaceous plants critical to just needed to burn these stands periodically. wildlife habitat. And the value of reducing or music. Horizontal limbs of flattened Prescribed fire is just one tool in the tool box eliminating woody shrubs and hardwoods in crowns hold the wind as if they are for restoration of longleaf pine savannas.” recovery of the savanna community is recog- vessels, singing bowls, and stir in Blake also notes that the study results have nized,” explains Blake. them like a whistling kettle. ” prompted significant changes in silvicultural The next phase of the study is now underway. —Janisse Ray, “Ecology of management within areas targeted for savanna Another round of thinning (2012) and pre- a Cracker Childhood” restoration, and they have challenged stocking

FOR FURTHER READING Brunjes, K.J.; Miller, K.V.; Ford, W.M.; Harrington, T.B. 2006. Plant competition, Harrington, T.B.; Dagley, C.M.; Edwards, Harrington, T.B.; Edwards, M.B. 2004. facilitation, and other overstory—under- M.B. 2002. Above- and belowground Effects of thinning and herbicide applica- story interactions in longleaf pine eco- competition from longleaf pine planta- tion on vertebrate communities in longleaf systems. In: Jose, S.; Jokela, E.J.; Miller, tions limits performance of reintroduced pine plantations. Proceedings of the annual D.L. Longleaf pine : ecology, herbaceous species. Forest Science. 49(5): conference of the Southeastern Association management, and restoration. New York: 681–695. http://www.treesearch.fs.fed.us/ of Fish and Wildlife Agencies. 57: 252–267. Springer: 135–156. http://www.treesearch. pubs/20119. http://www.treesearch.fs.fed.us/pubs/20120. fs.fed.us/pubs/24493. Harrington, T.B.; Edwards, M.B. 1999. Harrington, T.B. 2011. Overstory and Understory vegetation, resource avail- understory relationships in longleaf pine ability, and litterfall responses to pine WRITER’S PROFILE plantations 14 years after thinning and thinning and woody vegetation control in Noreen is a science writer based in woody control. Canadian Journal of Forest longleaf pine plantations. Canadian Journal Port Townsend, Washington. She can be Research. 41: 2301–2314. http://www. of Forest Research. 29: 1055–1064. http:// reached at [email protected]. treesearch.fs.fed.us/pubs/42492. www.treesearch.fs.fed.us/pubs/1170.

5 PRSRT STD US POSTAGE PAID PORTLAND OR FINDINGS PERMIT N0 G-40 U.S. Department of Agriculture Pacific Northwest Research Station 333 SW First Avenue P.O. Box 3890 Portland, OR 97208-3890 Official Business Penalty for Private Use, $300

scientist profileS TIMOTHY B. HARRINGTON KARL V. MILLER is a professor of COLLABORATOR joined the Pacific Northwest wildlife ecology and management Research Station as a research for- at the University of Georgia. He John Blake, U.S. Forest Service, ester in 2002. He received a B.S. has been conducting research and Savannah River Site degree in botany from teaching courses on the relation- State University, an M.S. degree in ship between from Oregon State and wildlife habitat for 25 years. University (OSU), and a Ph.D. He has an M.S. from Ohio State degree in from OSU. From 1984 to University and a Ph.D. in wildlife management 1991, he worked as a researcher in the forest veg- from the University of Georgia. etation management cooperative at OSU. From 1992 to 2002, Harrington was a professor of Miller can be reached at: silviculture in the School of Forest Resources at Warnell School of Forestry the University of Georgia in Athens. His current and Natural Resources research focuses on forest regeneration, vegeta- University of Georgia tion management, and invasive plant biology and Athens, GA 30602 management. Phone: (706) 542-1305 Harrington can be reached at: E-mail: [email protected] USDA Forest Service Pacific Northwest Research Station Forestry Sciences Laboratory 3625 93rd Avenue SW Olympia, WA 98512 Phone: (360) 753-7674 E-mail: [email protected]

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