Forests are complex ecosystems comprised of biotic (living) and abiotic (non-living) components. Forests change constantly due to the interrelationships of different ecosystem components and the timing of environmental events. Some forest changes are dramatic, while most are quite subtle.
Germination is the process whereby stored energy in a plant seed is reactivated. The resulting metabolic activity leads to the development of a seedling. For germination of specific plant species to be successful, certain environmental conditions need to exist. Consequently, some seeds may lie dormant in the soil for years, only to be reactivated when appropriate environmental conditions arise. Seed storage in the soil is referred to as the “seed bank.”
Different tree species have different sizes of seed. Some tree species are termed “heavy-seeded” because their seeds are large and require the assistance of dispersal agents. American beech and red, white, black, and northern pin oaks are local examples. Blue jays and many other bird species can move acorns a long way. Rodents, such as gray, fox, and red squirrels, also disperse seeds farther from the parent tree than would otherwise occur.
Other tree species are termed “light-seeded” and produce very small seeds that can be dispersed significant distances by wind. For some light-seeded tree species that hold their seed into the winter, dispersal can be enhanced when seeds are blown across the crust that forms on top of snow; these tree species also function as natural winter bird feeders. Local examples of light-seeded tree species include paper birch, yellow birch, and ironwood.
Soil scarification is the process of preparing a site for seed germination by exposing mineral soil. And scarification can occur by different means. For instance, windthrow is the process in which whole trees are blown down. The result is exposed mineral soil where the roots once held the tree vertically in place. Windthrow is common on wetter or rockier sites because tree root depth is limited. Conversely, on drier sites with deep sands, fire can scarify the soil by removing the litter layer through the consumption of leaves (needles) and other organic matter. The resulting ash may function as fertilizer for seeds that germinate on the exposed mineral soil.
For some light-seeded tree species, such as paper birch, fire is critical. While fire may kill adult trees, it also prepares the soil for the next generation. Because paper birch seeds are small, they have little energy reserves and can desiccate quickly and become unviable if they fall on leaf litter. Fire removes the leaf litter and prepares a seedbed and increases seed viability. Not surprisingly, many natural fires occur in late summer and paper birch has evolved to drop seed in the fall or early winter when mineral soil is still exposed and moisture is abundant. Because of this, paper birch is one of the more fire-dependent tree species in Michigan. Fire suppression, along with climate change and secondary succession, has been reducing the abundance of paper birch in Michigan forests for decades.
Scarification can also be accomplished mechanically. Logging operations during the growing season can disturb the top layer of the soil when tracked machinery moves across the forest floor. And scarification can be enhanced when tree tops are dragged around the site. However, logging operations are not conducted during the growing season in many Michigan forests in an attempt to limit the spread of oak wilt. Oak wilt is a fungal pathogen that affects red, black, and northern pin oaks in our area. The pathogen moves below ground via comingled roots and above ground by beetles that respond to injured trees and carry fungal spores from tree to tree. To limit above ground spread of oak wilt, oak forests are often managed when snow covers the ground and beetles are inactive. During this time, soil scarification and its benefits are virtually nonexistent.
Forest landowners should consider the important role of soil scarification in some forest types. When done during logging operations, soil scarification can aid the development of diverse forests by promoting the establishment of many underrepresented tree species. Besides birch trees and ironwood, many pine species also regenerate better when scarification occurs. While eastern white pine seeds have the ability to regenerate across a range of soil types and even in the presence of a significant litter layer, red pine and jack pine benefit from exposed mineral soil.
The role of soil scarification in promoting successful tree germination is but one way in which the integration of biological and ecological concepts are incorporated into recommendations for managing for complex forests that are resilient and resistant.
Greg Corace is the forester for the Alpena-Montmorency Conservation District. For more information, including sources used in this article, Greg can be contacted via email (firstname.lastname@example.org) or phone (989.356.3596 x102).
What a simple word: science. Two short syllables, easily pronounced. Yet, to many, science is mystifying. As we cope with COVID-19, perhaps it is a good time to discuss how science works? According to the National Academies of Sciences, our most prestigious scientific organization, science is, "the use of evidence to construct testable explanation and prediction of natural phenomena, as well as the knowledge generated through this process." To practitioners, science is a process, a product, and a culture. As a human construct, science---by its very nature--is imperfect. But the scientific process acknowledges and addresses imperfections by specific actions aimed at improving data quality, reducing conflict of interest, and increasing repeatability. Science begins when curious individuals ask novel questions. These novel questions are then answered (imperfectly) through the structured collection of data, data analysis, and the preparation of a manuscript describing background, methods, results, and implications of findings. The manuscript is then subjected to peer-review. Peer-review is defined as, “the process of evaluating scientific work by a group of experts in the related field. It is also known as refereeing because the work or project must be critiqued before it is published, funded, or implemented.” Explicitly, peer-review takes into account conflicts of interest. Reviewers are expected to have no relationship with the authors of the submitted manuscripts, making peer-reviewed manuscripts quite different than a report coming from an individual organization or office. Reports often suffer by not being refereed by outside entities devoid of bias. Science is communicated among professionals in a written format. A good scientific moto is: beware what you hear, be skeptical of what you read. The product of peer-reviewed science is called a “paper”. Papers are published in “journals”. Journals, such as Forest Ecology and Management, The Journal of Wildlife Management, or the countless other journals in an array of disciplines compete for prestige either regionally, nationally, or internationally. Journals have a Board, an Editor, and a suite of Associate Editors. These scientists set the direction for the journal and oversee the selection of reviewers that evaluate the quality of submitted manuscripts. For some journals, acceptance rates (the proportion of submitted manuscripts done well enough to be accepted and represent the standards of the journal) can be as low as 20%. The more prestigious the journal, the higher its standards and lower its acceptance rate. For forest and wildlife ecologists, the entire process--from posing a question to seeing a paper through the peer-review process and published in a journal--may take years. Besides describing many aspects of the scientific process, papers also acknowledge the contributions of individuals and organizations. So, what are textbooks? One can think of textbooks as a compilation and summary of relevant papers on a topic. Because science changes, textbooks are updated fairly often. Each new version of a textbook summarizes and references recent papers and those whose findings have lasted the test of time. Science is a human enterprise aimed at serving society by advancing knowledge. Science does not make decisions, but allows decisions to be evidence-based. Not surprisingly, natural resources management guidelines change over time because the scientific foundation they are based on changes and the contexts in which the science is applied change. Natural resource management in 2020 is very different than management in 1950. If we think our knowledge of the natural world is complete, or if we think “one-size-fits-all” approaches apply, we may be fooling ourselves in many instances. Unfortunately, some decisions occur without the transparency of the science that is meant to guide the art that is management. This may occur because too few scientists are employed within our institutions or too few of our leaders are scientists. Scientists are needed to instill a culture of science. A culture of science encourages curiosity and rigorous debate based on data and methodology. At its core, a culture of science openly challenges dogma and rhetoric. Social vagaries, social sensitivities, group thinking, or politics can squash a culture of science. As a critical component of evidence-based decision making, the public should support a culture of science throughout all phases of society. While healthy skepticism is important, the public should also strive to be informed on the current state of science as it relates to issues that impact our lives. Always ask if findings being presented have been published and, if so, where. If interested, Google Scholar can be used to see what science is being done, where, and by which scientists (keywords can include topics of interest, locations, names of authors, or a combination). In science, process, product, and culture matter. Greg Corace is the forester for the Alpena-Montmorency Conservation District. For more information, including sources used in this article, Greg can be contacted via email (email@example.com) or phone (989.356.3596 x102).
Dr. Greg Corace
Want to hear about what is new in the science world? Maybe get more information on the birds around us? Or maybe you want to keep up to date on what is happening in our current environment and with the natural resources we love. Check out some interesting articles shared by our Forester, Dr. Greg Corace.