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Lycopodium Management
by Elizabeth Nauertz, USDA Forest Service and Colleen Matula, Wisconsin Department of Natural Resources
Introduction and Background
Lycopodium, or club moss, species occur relatively frequently in northern hardwood forests (Curtis, 1959; Kotar, Kovach, and Locey, 1988). Lycopodium comes from the Greek words "luko" (wolf) and "podos" (foot); thus the common name of "wolf's paw" or "wolf's foot."
Lycopodium species are not related to the mosses as some might think, but rather are related to the ferns and are considered to be fern-allies. They are evergreen, perennial, clonal, and rhizomatous in nature. Habitat range for each Lycopodium species may vary, but typically they are found in cool, moist conditions, can tolerate a range of nutrient availability, and can withstand a wide range of light conditions. Often they are found in maple-basswood or mixed pine-hardwoods.
A variety of species of Lycopodium occur in the northern forests. The most common to these forests are as listed: Lycopodium dendroideum (round-branched ground pine), Lycopodium obscurum (flat-branched ground pine), Lycopodium lucidulum (shining club moss), Lycopodium annotinum (bristly or stiff club moss), Lycopodium complanatum (ground cedar), and Lycopodium clavatum (running club moss or wolf's paw).
Of this group of species, the ground pines, also known as princess pine, are the most heavily harvested or gathered. Ground pines are allowed for harvest via a permitting process on federal national forest lands. Permits are also issued for harvest on Michigan and Minnesota state forest lands. Harvest by permit is not allowed on Wisconsin state forest land. Lycopodium complanatum (ground cedar) and Lycopodium clavatum (running club moss) are also often gathered, but only from privately owned lands and with landowner permission.
The Lycopodium species that are gathered are classified as non-timber or special forest products; that is, they are non-tree species that are collected or harvested for various uses. Examples of uses for Lycopodium include winter seasonal decorations, floral industry, medicinal and homeopathic remedies, historical aboriginal uses, whole plant harvest for naturalizing landscapes, and spores for pyrotechnics and special effects. In fact, the first photographic cameras used Lycopodium spores as flash powders. In addition, spores were used in toilet powders, coatings for pills, and pancake makeup.
Special forest products play an important role in many people's livelihood and in their economic strategies. This may be particularly true in northern regions where formal employment or income is not adequate. Many gatherers of these products have multi-generational ties to the regional forests and have acquired the ecological knowledge and harvesting skills needed to promote the growth of these products (Emery, 1998; Zasada, 1997; Lycopodium Issues Workshop, 1995).
(photo courtesy of Cloquet Forestry Center)
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Research interests on Lycopodium, particularly for the heavily harvested species of ground pines or princess pines, stemmed from varying perspectives. Matula's approach (1995) was spurred by some startling statistics. Approximately 170,500 pounds per year of princess pine (85.25 tons) were collected annually from just two buyers in Wisconsin and the Upper Peninsula of Michigan. The basis for Matula's study: What were the effects of harvest on the ground pines or what has been termed the Lycopodium obscurum complex? In addition, ground pines are considered to be a mid-seral species, occurring in forest stands 10 to 30 years in age and will decline in very old stands. In general, if temperatures become warmer and the forest becomes drier, these species would be expected to decrease.
Using Matula's work as a basis, Nauertz' research (1999) evolved. The project was initiated around a multi-agency workshop organized in 1995 to address issues of concern regarding the harvesting of the Lycopodium obscurum complex (ground pines). Few studies had been conducted to determine how these species could be regenerated, how fast they respond to harvesting, and how forest management practices may impact them. It was decided that more information was needed to determine whether forest management regimes and harvesting activities create conditions necessary for continued success. Nauertz' study concerned itself with the abundance and frequency of Lycopodium species under various forest management regimes in northern hardwood forests.
Morphology and Physical Features
Each of the Lycopodium species has a characteristic modular growth form (above- or below-ground rhizomes), common branching angle and pattern, characteristic method of vegetative reproduction (most commonly observed), and of sexual reproduction (rarely observed). An entire plant may have both above- and/or below- ground parts. Many aerial stems may make up a plant. Many plants may make up a clone in which all of the plants are genetically identical. The size range of each plant and/or clone may vary with resources available, disturbance factors, and age.
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For all Lycopodium species, the aerial stems have two primary functions. One function is for photosynthesis where photosynthates are produced and are then stored in the rhizomes for future use. The second primary function is spore production. When the aerial stems reach maturity between four and six years of age, they may produce strobili, or cones, that, in turn, form spores that are the necessary first step in the sexual reproductive cycle. Rhizomes, which are lateral branches and not roots, may grow above- or below-ground, depending on the particular species. Rhizomes get the entire plant where it "wants" or "needs" to go, in a sense foraging for new resources to exploit. This has been termed "guerrilla tactics." Lycopodium roots are considered to be adventitious and are formed from the rhizomes with their primary function being to anchor the plant in the soil and to absorb water and nutrients. Physiological integration or resource allocation allows the plant to share or allocate the carbohydrates from photosynthesis and water and nutrients from root uptake.
Plants with above-ground rhizomes, regardless of species, do not have to navigate the subterraneous environment; consequently they experience less resistance in taking an above-ground route. They would be able to travel or "leap" over hard-packed soil, or rocky and wet surfaces, which may enable them to locate new resources more quickly and thus begin to put energy into clonal expansion or vegetative growth. The rhizomatous nature of Lycopodium species allows a plant to optimize its resources both in the immediate vicinity and also out into the surrounding area.
Species with subterraneous rhizomes, such as do the Lycopodium dendroideum and L. obscurum (the commonly harvested ground pines), would be able to travel more easily through well-aerated organic matter conditions, conditions that may exist on a mound versus conditions that may exist in more heavily compacted soils such that may occur in logging roads. Nauertz has observed that typical upland Lycopodium species, such as ground pines, have an affinity for mounds rather than pits or level areas across the forest floor.
Lycopodium lucidulum (Shining club moss) is unique to the group included here. At around year six of age they will begin to produce gemmae or bulblets in the upper leaf axils. This is another method of dispersal in that, when the gemmae are mature and with plant movement, the gemmae may be catapulted or launched away from the existing plant. The gemmae may then act like a "seed" in a sort in that it may germinate and produce a new, genetically identical individual. This is a method of vegetative reproduction and an increase in frequency without creating any new genetic variation.
Alternation of Generations
Like ferns, fern-allies such as Lycopodium experience an alternation of generations. This is a sexual reproduction method where a spore may germinate-typically in mineral soil-a gametophyte may form below the soil surface, genetic recombination may take place, and a new individual sporophyte or plant may result, pending all growing conditions are optimal. It may take up to 20 years for this cycle to take place. This is an important time line to consider from a forest management perspective.
Spore germination and gametophyte formation occur within the soil surface layers. Exposed mineral soil and available organic matter (conditions that may exist after an overstory cut or blow-down) may offer prime conditions for spore germination and development. As a new plant develops, it will begin to rely more on vegetative reproduction for expansion of cover. A tip-up or blow-down could technically offer the ultimate in plant establishment for species needing mineral soil conditions for germination.
Graduate Work (Matula, 1995)
Introduction and Methods
In 1994 and 1995, Matula studied the life cycle and growth
rate as well as the effects of harvest on the Lycopodium
obscurum complex (L. dendroideum and L. obscurum). This
study took place on the Chequamegon National Forest near
Ashland, WI, USA. One hundred and sixty-five aerial shoots
were monitored from May through September of each year by
measuring the lateral branch, aerial stem, and strobili of
each plant.
The age of each shoot was determined by counting annual growth markers. Most growth of the aerial shoots was found to occur in year 2, and by years 3 to 4 the aerial shoots begin to produce strobili. The entire life cycle for an individual aerial stem is between four and six years. Once an aerial stem reaches maturity and the spores are released from the strobili, typically starting in September, the shoot will slowly begin to senesce.
Results and Conclusion
Growth was found to be substantially greater in 1994 than in
1995. The differences were enough to indicate other factors
may affect growth. The mean rainfall and mean temperature for
1994 and 1995 were correlated with the growth rate of the
morphological characteristics. Overall, only the 1994
rainfall data strongly correlated with the growth rate of
aerial shoots.
A total of 40 Lycopodium obscurum and L. dendroideum plants were excavated and the rhizomal branching patterns were observed. Most plants had many branches leading away from the main rhizome. This was particularly true when apical dominance appeared to be related due to dead or snipped apices. It appeared that harvesting aerial stems stimulated rhizomal branching. If the main rhizome is not damaged, it is thought that the entire plant could theoretically live indefinitely with aerial stems dying after five years or so.
Recovery of the Lycopodium obscurum complex after harvest was observed on 32 sites. The sites contained two one-meter square plots that were harvested at various levels. The levels of harvest included 0% (control), 10%, 50%, and 100% harvest of the total aerial stems. Recovery of aerial shoots on these plots was monitored for two years. The results were surprising. Plots that were harvested 0% and 10% recovered completely within the first year. Plots that were harvested 50% and 100% recovered over 50% within the two years of this study.
The question Matula raises is that, if we continue to harvest at 100% all of the time, do we need to consider what it is that we are doing to the rhizome, which is the main photosynthate (carbon) storage area for the plant? Lycopodium species are very opportunistic plants. Their modular growth form, which is common in clonal plants, allows them to respond to the micro-environment and to disturbance factors. Matula does not believe that Lycopodium obscurum complex can tolerate continued harvest on the same site, but if harvested at rates of <50% of total cover and allowed a time period of a few years between harvests to recover, it can be maintained as a sustainable forest resource.
Graduate Work (Nauertz, 1999)
Introduction and Methods
In 1998, Nauertz' project focused on all of the
Lycopodium species found in sugar maple-dominated
northern hardwood forests. The research objectives were to
compare the distribution of Lycopodium species under
different forest management regimes, including their
frequency and abundance. The following questions were asked.
1) Does combined or individual cover of Lycopodium
species depend on a specific management regime? 2) Does the
overall cover of Lycopodium depend on one or more
species of Lycopodium and their growth habit? 3) Is
the percent cover of individual Lycopodium species
correlated with stand basal area?
The study sites were located in the Ottawa National Forest near Watersmeet, Michigan, USA. Three managed-old growth (1), even-age (3), uneven-age (3)-and two unmanaged-old growth (3), second growth (3)- forest management regimes were used in this study. Ten 5x5 m2 plots were randomly located within each replicate stand of each management regime for a total of 130 plots. The survey was conducted during the first two weeks in June of 1998. Percent cover of each Lycopodium species present was recorded for each plot, and from plot center a 2m factor prism was used to estimate basal area of canopy trees. Diameter at breast height was recorded for all "in" trees, along with the respective tree species.
Results and Conclusion
Overall, Lycopodium species occurred in 10% to 67%
of the plots, with two-thirds of the Lycopodium
found to occur in the managed even-age and unmanaged
old-growth stands. For all Lycopodium species
combined, highest frequency and percent cover existed in the
managed even-age (67% of plots measured had
Lycopodium present; up to 9% cover value); unmanaged
old growth (67% of the plots measured had Lycopodium
present; up to 8% cover value); and unmanaged second growth
(50% of plots had Lycopodium present; up to 6% cover
value).
Lycopodium dendroideum (3-27%) and L. lucidulum (3-27%) occurred most often across management regimes with cover values found to range from 0.5-4% in unmanaged old-growth stands, 0.5-6% in unmanaged second-growth stands, and between 0.5-4% in managed even-age stands. Lycopodium annotinum did not occur as often, but did account for higher cover values recorded (3-9%) in the managed even-age and unmanaged old-growth management regimes.
Lycopodium dendroideum had the greatest average percent cover for all forest treatments combined (0.4% a), with mean cover significantly different than the other individual Lycopodium species. Lycopodium dendroideum did not occur in any of the study plots under the uneven-age treatment replicates (0.0% b) as compared to the other treatments, and hence was also statistically significantly different. Mean percent cover of Lycopodium lucidulum was highest (0.6% a) and significantly different in the old-growth management regime than in the other replicated treatments.
Mean percent cover for all Lycopodium species combined for managed stands (0.1% b) was significantly different than for the unmanaged stands (0.2% a). Lycopodium lucidulum mean percent cover was greater in the unmanaged stands (0.4% a) than in the managed stands (0.1% b) and was also significantly different.
Mean percent cover of all Lycopodium species combined was greater in the second-growth origin stands (0.2% a) and significantly different than in the old-growth origin stands (0.1% b). Lycopodium dendroideum showed significant cover responses to the second-growth origin stands (0.6% a) as compared to the old-growth origin stands (0.2% b).
Highest frequency and mean percent cover occurred under the management regimes with the highest residual basal area as was recorded in 1995-96. In this study, the management regimes that were statistically similar include the unmanaged old growth (a) at 27-32 m2/ha, managed even-age (a) at 17-25 m2/ha, and unmanaged second growth (a) at 25-27 m2/ha. Lycopodium obscurum percent cover (r2= 0.54;P<0.01) was correlated with total big-tooth aspen 2m factor basal area. Only L. dendroideum cover (r2= 0.74;P<0.01), L. annotinum cover (r2= 0.66;P<0.01), L. lucidulum cover (r2= 0.49;P<0.01), and total Lycopodium cover were correlated. Unmanaged old growth and managed even-age have the highest total Lycopodium cover with basal areas that appear to be comparable relatively speaking.
Frequency of occurrence for the combined and individual Lycopodium species among the management regimes used in this study was low. Small-scale patchiness in the landscape offers enough habitat diversity to allow the various Lycopodium species to co-habitat within a single major forest type and helps to explain the distribution and cover found. Individual growth form and reproduction method, both sexual and asexual, aid in explaining the frequency and cover found for the individual Lycopodium species. Lycopodium species spread vegetatively by creeping rhizomes, and they tend to form small clumps or colonies, resulting in a low to medium degree of aggregation on average. These clumps are so well distributed throughout the forest that they impact a certain amount of randomness in their distribution (Curtis, 1959).
The evergreen nature of Lycopodium species allow them to take advantage of the photosynthesis opportunity that occurs during the spring and fall light windows that exist in forest stands, independent of stand basal area and light conditions during the prime growing season. Among the management regimes used in this study, the degree of canopy removal and consequently the amount of light reaching the forest floor may not be much of a concern to the relative abundance or cover of Lycopodium species. Rather, the degree of extensive and intensive soil surface disturbance, along with the degree of soil compaction that may result from logging operations, may be more of a concern and may either benefit or hinder sporophyte (plant) development and clonal expansion.
If a higher frequency of occurrence for Lycopodium has been found to exist in previously managed stands (mineral soil conditions from disturbance), then perhaps some degree of disruption or disturbance is beneficial from the genetic diversity point of view. The higher Lycopodium cover values found are the result of vegetative expansion, which is what would occur with time following disturbance. From a forest management perspective, it appears that time (minimum of 80 years as has been noted in the stands of second-growth origin) following disturbance is what is needed to allow for higher levels of Lycopodium frequency to develop as well as for clonal expansion or a substantial increase in cover to occur.
Lycopodium Harvesting Guidelines and Management Recommendations
The most efficient way to harvest the ground pines (Lycopodium obscurum complex) is to pluck or clip the mature aerial stem near the base of the stem at ground level. Whether it is less stressful for the plant to have the aerial stem clipped with a sharp instrument or for it to be plucked has not been determined. Some are concerned that plucking may impact or disturb the below-ground portion of the plant. The particular method used for gathering is at the harvester's discretion. Harvesting of individual mature aerial stems in such a way as to not disturb the underground rhizome may enhance the survival of the plant and may increase or stimulate below-ground branching.
Typically a permit is required if one plans to harvest Lycopodium obscurum complex on public lands. Check with the particular public land agency in question to get the specific rules and regulations for that area. Only the mature aerial stems, the stems that have produced strobili or cones, are considered to be economically valuable. Most Lycopodium is gathered in the fall of the year; typically beginning around September. Most ground pine is used for holiday decorative purposes and so this would be an appropriate time to begin collecting in order to get the materials to the regional buyers in time for preparation for use. This time-frame also coincides with when the Lycopodium spores are mature and are ready for dispersal. The commotion created while gathering allows spores to be knocked out of the strobili, dispersed into the air, and fall onto the forest floor.
To ensure future Lycopodium harvest opportunities, take only the mature aerial stems and leave the immature stems for a future harvest. At least two years should be allotted between harvests in the same area to allow for enough time for an increase in vegetative expansion of cover that will provide good insurance for future harvest opportunities. In addition, by skipping a year or two between harvests in the same area, you will allow time without disturbance for possible spore germination and for the potential for new plant development and new genetic material. Any abrupt and intensive alteration of growing conditions could make it difficult for the survival of any type of existing ground vegetation. When considering whether to gather any forest products, it is important to consider taking it in moderate quantities.
To conclude, Lycopodium management implications may include the following.
- Consider the breeding system and start the harvest after spores are released.
- Estimate the land's potential-that is, what is the habitat type and ask how the harvesting and disturbance regimes used affect that area.
- Monitor the harvest, or, ask if it is necessary to monitor the harvest.
- Consider the potential threats to a species habitat (e.g., development).
- Gain the necessary knowledge regarding seed bank and germination ecology for the species in question.
- Understand the geographical range of habitat for the species in question.
- Determine if micro-site specialization needs to be considered for an individual or group of species.
- Consider short- and long-term habitat management.
- Develop and monitor zones of harvest.
Reference Literature
Curtis, J. T. 1959. The Vegetation of Wisconsin: An Ordination of Plant Communities. The University of Wisconsin Press.
Emery, M. 1998. "Livelihood Diversity: Non-timber Forest Products in Michigan's Upper Peninsula." Ph.D. dissertation. Department of Geography, Rutgers University.
Kotar, J., Kovach, J., and Locey, C. 1988. Field Guide to Forest Habitat Types of Northern Wisconsin. Published by the Department of Forestry, University of Wisconsin-Madison, and Wisconsin Department of Natural Resources.
Lycopodium Issues Workshop. Interagency - Industry Meeting. July 27-28, 1995. Florence, WI, USA.
Matula, C. 1995. "Growth Rate, Growth Patterns, and Effects of Harvest of the Lycopodium obscurum Complex in the Lake Superior Region." Master of Science thesis, University of Wisconsin, Eau Claire. Eau Claire, WI, USA.
Nauertz, E.A. 1999. "Impact of Various Silvicultural Practices on the Abundance and Frequency of Lycopodium Species in Northern Hardwood Forests." Master of Science in Forestry thesis, Michigan Technological University, Houghton, Michigan, USA.
Zasada, J. 1997. "The forest as a 'specialty.'" Better Forests. Vol II (3): 14-15.
