Thursday, June 21, 2012

Native Seed Project

We have recently finished sowing 4 of our native seed collections into seedling trays!  There are just over 400 trays undergoing a stratification treatment at Pee Dee REC.

As you can see below, we still have a few gaps to fill before our next round of seed sowing.

We recently received Sorghastrum elliottii that was collected at Francis Marion NF, so that fills a big MAC gap for that species.  Thanks Robin and Vic!  Our most pressing needs are for Lespedeza capitata, Tephrosia virginiana, and Liatris pilosa from the SAC. Please let us know when you see those species beginning to set seed.

Wednesday, May 9, 2012

From One Forest to Another

From One Forest to Another
by Huifeng Hu and Bryan Mudder

Sunrise in the loblolly pine forest where our replicated field experiment was located. Photo by Bryan Mudder

Federal land managers across the country are being asked to provide more and more resources on fewer and fewer acres.  Timber and fiber production, clean air, clean water, and habitat for increasing numbers of endangered species are just some of the benefits these lands are expected to produce sustainably ad infinitum.

Natural resource managers at Camp Lejeune Marine Corps Base in North Carolina have realized that restoring longleaf pine forests and their associated native plant communities will help to meet this steadily increasing list of resource demands.  Currently, many of the base’s upland forest stands are composed of mature loblolly pine and are home to recovering populations of the endangered red-cockaded woodpecker.  Compared to longleaf pines, loblolly pine trees are considered “off-site” in these sandy, well-drained soils, but none-the-less do very well at producing the timber and fiber that are harvested at regular intervals. 

Forest Gentrification

So, how will longleaf pine be restored to the site?  Though the site’s red-cockaded woodpeckers would prefer stands of native, longleaf pine over the current stands of loblolly, conversion will not be easy, since their current loblolly homes will have to be cut down.  Changing from one forest to another without adversely affecting the successful recovery of an endangered species is a bit like re-modeling a kitchen without upsetting the busy chef.  Careful consideration for retaining habitat features and ecosystem function must be made.

To this end, the military called on Forest Service scientists and Clemson University researchers  to develop protocols for restoring longleaf pine and its characteristic native plant community in already established loblolly pine stands at Camp Lejeune.   This 3-year study was conducted in the moderately well- and well-drained soils of Onslow County, North Carolina.  What are optimal silvicultural practices for restoring longleaf pine and its related herbaceous dominated understory structure within loblolly pine stands? 

Study site Camp Lejuene, NC

Dr. Geoff Wang recruited Huifeng Hu, a graduate of the Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences in Beijing, China as a Ph. D student to conduct this aspect of the research.  Hu came to the United States in August 2006 under a student visa and only had a few months to get oriented in South Carolina before hitting the books at Clemson University.  Once Hu had a few classes under his belt, Forest Service scientist Dr. Joan Walker, sent him out with her crew for immersion into the field setting.

Huifeng in the field 2007. Photo by Zhiping Wang

The Onslow County Study

The researchers set out 3 objectives for their study:

        1) to quantify canopy treatment effects on the survival and growth of planted longleaf  
            pine seedlings, ground-layer vegetation composition and structure, and plant resources.
        2) to quantify cultural treatment effects on the survival and growth of planted longleaf pine
            seedlings, ground-layer vegetation composition and structure, and plant resources. 
        3) to determine the relationships between mortality and growth of planted longleaf pine
            seedlings and plant resources.

The researchers conducted a replicated field experiment from summer 2006 through fall 2010 (Table 1) to test the effects of two levels of silvicultural treatments on understory plants and selected resources that they depend on for life.  These two levels involve the overstory layer where we applied "canopy" treatments and the understory layer where we applied "cultural" treatments. 

Table 1: Time-line for Camp Lejeune field experiment

Aug. 2006 to Jan. 2007
     Plot selection and layout

Feb. to May 2007
     Harvest canopy trees
Jul. to Sep. 2007
     Site preparation by mechanical mowing and prescribed fires 
     then measuring plot characteristics with DBH and species

Dec. 2007
     Planting longleaf pine seedlings by hand
May to Oct. 2008
     Annual measurements of seedling growth and mortality 
     and environmental factors

Oct. 2008
     Applying herbicide cultural treatment
May 2009
     Applying fertilizer cultural treatment
May to Oct. 2009
     Annual measurements of seedling growth and mortality
     and environmental factors

Jan. to Mar. 2010
     Prescribed burning in the field based on local management
May to Oct. 2010
     Annual measurements of seedling growth and mortality 
     and environmental factors

Canopy treatments were applied to loblolly pine stands of similar age and size defined by a target residual basal area.  Basal area refers to the amount of space, expressed in square meters, taken up by trees on a given hectare of land.  A spectrum of treatment levels were used from “dense”, control (no treatment) plots to “medium” basal area, to “low” basal area, to “no canopy” at all in the clearcuts.  Single trees were removed from each stand to achieve uniform canopies.  Three circular gap treatments containing openings of targeted size were also used.  Large, medium, and small gaps as described below. 

Four uniform canopy treatments (left) from dense to open and three sizes of gap canopy treatments (right)

Within each canopy treatment, three cultural treatments were applied including “no treatment”, “herbicide”, and “herbicide with fertilizer”.

Three cultural treatments applied as square sub-plots (left) or as linear sub-plots (right)


Among uniform plots, the effect of canopy and cultural treatments on longleaf pine seedlings over the course of three growing seasons was varied and requires some explanation.  The metrics used were survival (the seedling is alive or dead) and root collar diameter.  

The root collar is measured at the base of a seedling at soil level with digital calipers and is an important metric associated with the health and vigor of an individual. Photo by Ben Knapp

The “dense” canopy treatment plots, especially with “no cultural treatment”, seemed to have the least vigorous seedlings (according to root collar measurements) along with low survival.  The “no canopy” treatment plots (associated with “fertilizer + herbicide” cultural treatment plots) had the largest root collar diameters and the best survival, thus the healthiest individual longleaf pine seedlings.  The “no canopy”, “medium”, and “low” canopy treatments all had significantly more seedlings in height growth than the “dense” treatment. 
 Longleaf pine seedlings have a unique adaptation, called a grass stage, that allows seedlings to invest energy and resources into the growth of an extensive root system while the bud and needles aboveground appear grass-like. Photo by Huifeng Hu Februray 2009

  This adaptation is thought to help seedlings recover quickly from the relatively frequent fires occurring in the ecosystem, then outcompete neighboring plants by a sudden spurt of height growth.
Photo by Bryan Mudder

Based on these results, it would seem that “no canopy” treatment is the silvicultural protocol best suited to restore longleaf pine.  But when associated with a “fertilizer + herbicide” cultural treatment the “no canopy” treatment plots had the greatest cover of woody, herbaceous, and graminoid (grasses and grass-like plants) vegetation groups and highest density of loblolly pine seedlings.  Such a competitive environment would not favor longleaf pine seedlings at all.

Natural loblolly pine regeneration is a major competitor with planted longleaf pine seedlings.  As many as 10,000 loblolly pine seedlings per acre appear in our stand soon after canopy removal. Photo by Huifeng Hu Februray 2009

There is so much diversity in these systems that it is not possible to measure every individual plant.  We organized plants into functional groups using biological and physically descriptive traits, then estimated the amount of area, or cover, each of those groups take up within measurement plots (above). Photo by Bryan Mudder 

Among the three circular gap treatments, size of gap did not affect survival or growth of planted longleaf pine seedlings, abundance of ground layer vegetation, or the density of midstory woody plants after the first three growing seasons.  The position of a given seedling within a gap did significantly affect individual growth.  This means that a seedling located in the center of the gap was likely to be larger and taller than a seedling located on the edge of a gap.  Both gap size and within-gap position significantly affected gap light index but did not affect surface soil moisture or soil temperature. 
Huifeng measures pre-dawn water potential with a Nitrogen gas chamber. Photo Bryan Mudder

Although within-gap position did affect phosphorous and potassium concentrations in longleaf pine seedling needles, these effects showed neither consistency over the two years, nor followed any expected pattern of change (i.e., higher closer to the center of a gap or lower at the edge of a gap).  Our results supported the hypothesis of light limitation on seedling growth in gaps [this hypothesis is that longleaf pine regeneration in canopy gaps is limited by competition for light].

Light is the most important limiting factor for the survival and growth of planted longleaf pine seedlings. A dense canopy will only allow a samll amount of light through the canopy. Photo by Huifeng Hu December 2007

The canopy treatments did not affect species richness (species richness is defined by the total number of species counted in an area regardless of abundance), but where herbicide was applied an effect on species richness was detected, especially for woody species richness.  Using the non-metric multidimensional scaling (one common method to analyze the similarity among vegetation plots) and multi-response permutation procedure (one common method to analyze the difference in vegetation structure among different groups), we found that variation in the understory vegetation can be best explained by soil characteristics, especially soil texture, rather than any experimental treatments.

The gap light index differed among the four uniform canopy treatments, increasing with decreasing basal area, meaning as more mature stems are removed more light is allowed to enter the forest floor.  “Herbicide” plots showed higher soil temperatures in both 2009 and 2010.  Concentrations of calcium, magnesium, zinc, and iron in longleaf pine seedling needles significantly increased after the prescribed fire of January 2010, while foliar concentrations of nitrogen, copper, and sodium significantly decreased.  The effects of canopy and cultural treatments on foliar nutrients of longleaf pine seedlings were not consistent over the two year measurement period. The root collar diameter of longleaf pine seedlings increased with higher gap light index and higher concentrations of foliar phosphorous, calcium, and zinc, but decreased with higher soil temperatures.

Why is this important?

Sunset in a longleaf pine forest. Photo by Bryan Mudder

Longleaf pine (Pinus palustris Mill.) historically dominated forests on the southern Atlantic and Gulf coastal plains, with its presettlement range occupying 37 million hectares from the border of Texas and Louisiana eastward to the Atlantic Ocean, and from the middle of Florida northward into Virginia (Frost, 2006).   The widespread range of the species was largely attributed to the high frequency, low intensity surface fire regime that occurred throughout this region (Frost, 2006). 

As a result of logging, the expansion of agriculture and developed land, the introduction of more vigorous pine species [e.g., loblolly pine (LBP; P. taeda L.)], and fire suppression, the extent of the LLP ecosystem has greatly declined since European settlement (Wahlenberg, 1946; Frost, 2006).  Currently, fragmented LLP stands are scattered across the southeastern landscape, on approximately 2.2% (or 1 million hectares) of the original acreage (Frost, 2006).  However, there is an increased interest in restoring areas that have been converted to other forest types or farmland.  The impressive diversity and large number of rare species found in this ecosystem provide ecological significance for restoration (Knapp, 2005).  In addition, LLP has several well-known economic and silvicultural benefits: high quality products; fire tolerance; insect and disease resistance; wind firmness; the ability to grow and thrive on harsh sites; and the ability to respond to thinning at virtually any time in its long life (Johnson and Gjerstad, 2006).


After completing the field experiment we found that the "no canopy" treatment, resulted in the best survival and growth of longleaf pine seedlings during our 3 growing seasons.  Removing the entire canopy allows for the most light, but also allows for the most competition, especially that of natural loblolly pine regeneration.  This silivcultural technique might be feasible to convert loblolly pine stands into longleaf pine forest when canopy retention is not a management objective. 
Of the other canopy treatments, "medium" basal area, "low" basal area, and the "small gap" treatment are the best options for converting loblolly pine to longleaf pine while retaining a mature canopy.  Application of an herbicide increased the growth of planted longleaf pine seedlings, but results varied based on canopy treatments.  The "herbicide+fertilizer" cultural treatment also increased the growth of planted longleaf pine seedlings, but at the same time stimulated growth in the seedlings of natural loblolly regeneration. 
Light was the single most important environmental factor affecting survival and growth of seedlings in our experiment.  Land managers (public and private) interested in planting longleaf pine seedlings or converting stands into longleaf pine forest on similar soils should consider our findings and incorporate these silvicultural protocols into their management. 
For more information see the full article in Forest Ecology and Management.

USDA Forest Service SRS (Restoring and Managing Longleaf Pine)
Camp Lejeune Marine Base
Clemson University Silviculture and Ecology Lab  
Funding for this project was provided by the Strategic Environmental Research and Development Program (SERDP) sponsored by the Department of Defense (DoD), Department of Energy (DoE), and Environmental Protection Agency (EPA) (SI-1474: Managing declining pine stands for the restoration of red-cockaded woodpecker habitat).

The authors would like to thank following field technicians for assistance with data collection: Seth Cook, K. Hunter Leary, Joe Ledvina, Bryan Mudder, Erik Pearson, Shawna Reid,
Lindsay Stewart, Carsyn Tennant, and Evelyn Wenk .

Friday, April 27, 2012

Long live longleaf pine...

I just returned from visiting State Forests in North Carolina and South Carolina that are part of our Regional Longleaf Pine Cone Production StudySandhills State Forest is in Chesterfield and Darlington counties of SC and Bladen Lakes State Forest is located just northeast of Lumberton, NC.  This is the 47th monitoring year of this work, which was initiated by Bill Boyer and is now coordinated by Dale Brockway

Longleaf pine (Pinus palustris) is monoecious (i.e., “one house”), which means that both male and female strobili reside on the same tree.  The male strobili, called catkins, produce all that wonderful pollen we see in the spring-time and are generally found in the lower portion of the tree crown. 

Male strobili
Photo courtesy of Forestry Images

The female strobili are initially called flowers (then conelets during the following spring and mature cones by the fall), are generally found in the upper portion of the tree crown. 
Female strobili
Photo courtesy of Forestry Images

Conelets turn into the seed-bearing cones, synonymous with members of the Pinaceae family, and typically shed their seed during October.

Photo courtesy of Forestry Images

During our survey, we count the number of female flowers (newly pollinated but undeveloped small conelets), conelets (pollinated about one year earlier and developed into large “green cones”), and brown cones currently on the tree (that shed their seed during the previous fall).  The female strobili emerge during January/February and are pollinated during the infamous spring pollen flush that occurs between late-February and April.  Those strobili are now pollinated, but don’t become conelets until the following spring when fertilization occurs.  Those conelets then become seed-bearing cones, maturing during mid-September and mid-October.

Cone count data from ten widely-dispersed locations in the Southern Region are compiled and then assembled into a report that forecasts the longleaf pine cone crop for each state and for the region. 

In the past, landowners and land managers had trouble naturally regenerating longleaf pine, because of what was thought to be erratic seed production.  Through research, we now know that longleaf cone crops are highly variable from year to year because of the interaction of many physical and biological variables.  The longleaf pine cone production survey helps predict when a good or poor seed year is coming.  This alerts forest managers so they can be prepared to implement site-preparation treatments when more seeds are likely to fall on a receptive seedbed.

For more information on longleaf pine ecosystems, please see our research page.

Friday, April 20, 2012

Big Time at Brosnan Forest!

We were invited by Norfolk Southern Railway to give a presentation on the amazing biodiversity in the ground-layer of longleaf pine forests.  Thanks to all those at Brosnan Forest who made this wonderful trip possible. The field tour was packed full of interesting information.

We were able to share a good bit of the longleaf pine story with an audience new to the subject.  Longleaf pine forests are special places!  We illustrated the incredibly high diversity of species with a set of nested plots, then talked about endemic plants, and the important role fire has in these forest systems.

Just another beautiful day in the woods!

"The land of the longleaf pine is a land of great beauty... swaggering over the Coastal Plain from southeastern Virginia to eastern Texas...Yet little is left of the longleaf pine ecosystem today: only 1.4% of the Atlantic and Gulf Coastal Plains still support longleaf, compared to 60% in presettlement times.  By 1996 only 2.95 million acres of longleaf remained out of the original 92 million acres ... Almost all of the old-growth forest is gone ... By any measure, longleaf's decline of nearly 98% is among the most severe of any  ecosystem on earth.  It dwarf's the Amazon rain forest's losses of somewhere between 13% and 25%.  It is comparable to or exceeds the decline in the North American tallgrass prairie, the coastal forest of Brazil, and the dry forests of the Pacific Coast of Central America." 

-from Looking for Longleaf: The Fall and Rise of an American Forest by Lawrence S. Earley

Monday, April 9, 2012

Monitoring Ramps Populations

We just enjoyed another week in the mountian coves of western North Carolina...

One of our many sampling transects...

A time lapse of Rod and I sampling an entire plot...

Monday, March 26, 2012

In Abundance or In Trouble?

In Abundance or In Trouble?
11 years of monitoring ramps populations
Article and photographs by Bryan Mudder 

        Since 2000, Joan Walker, research plant ecologist with the U.S. Forest Service Southern Research Station has been monitoring populations of ramps (Allium tricoccum) in the mountain coves of western North Carolina.   Sometimes referred to as wild leeks, these perennial plants are among the first spring ephemerals to emerge during March and April.  After a hard winter in the mountains, with food stores running low, you can just imagine what a treat these fresh ‘greens’ would have been to both Native Americans and settlers living throughout this region in years past.  With their electric green leaves, plump, white bulb, and distinct odor – think freshly peeled onion overcome by just-minced garlic – ramps are easy to distinguish from other early arrivers.  Today, locals still harvest ramps for food, medicinal preparations, and to sell at markets at spring festivals.  In the spring you’re apt to see ramps on the menus of fine restaurants across the East.

        National Forests are responsible for promoting and maintaining biological diversity in order to sustainably deliver the valuable ecosystem services we all need.  These include clean air, clean water, healthy soil, abundant wood, recreational opportunities and other commodities that include herbs and edible plants.  During the mid-1990’s, concern was raised about overharvesting ramps in Canada (their northern range), where they’ve been since designated a vulnerable species and are no longer available for commercial sale.  Concerns about harvesting effects in the southern range (north GA, AL, and western NC) prompted Walker’s monitoring study, which investigates the distribution and size of ramps populations in two areas of the Nantahala National Forest in western North Carolina.  Despite the popularity of these plants, relatively little is known about the abundance, density, and distribution of ramps in this area. 

        The goal of our monitoring project is to track these ramps populations over time and determine whether they’ve been adversely affected by local harvesting, all in the interest of conserving this important species for future generations.  I started working on the project in 2007 as a biological science technician continuing the data collection effort.  We have 25 plots consisting of a central transect - 50 to 100 meters in length - with perpendicular sampling transects - each 10 meters in length - extending along either side at randomly determined distances.  The plots are distributed between 3500 feet and 5000 feet in elevation.  We quantify ramps cover, stem density, and soil disturbance using a line intercept technique.  For 11 years now, these same plots and transects have been carefully measured.  The following is a series of photos associated with our sampling transects taken every year during the monitoring study from a sub-plot 0.5m X 0.5m in size.

        In the years 2000, 2001, and 2005 some digging and/or harvesting occurred in a portion of our photo plot.  Bare mineral soil is exposed in the center and upper right portion of the plot.




        In subsequent years the area where soil was exposed remains void of ramps.



        It isn’t until 2010 that we see a few small ramps coming back.


        National Forest ramps harvest policies have not changed substantially in the last 5 to 10 years across individual Southern Appalachian management units.  Results from our research suggest that it may be time to critically examine the current harvest policy and perhaps take corrective measures, especially as forests are increasingly stressed by human and natural pressures.

Wednesday, March 21, 2012

We are rampin' up for sampling!

Our 2012 sampling season for Allium tricoccum will be starting a little earlier than in the past.  We have just returned from doing a little reconaissance in our mountain plots and are surprised to find so many ramps already emerging...