Forest Fertility
A tree falls in a forest, then what? ...Fertility begins.
There are cycles in the forest, a long-term absorption of nutrients and long-term giving of nutrients. No need to apply manure, compost, or nitrogen— the forest can create a monumental amount of growth and biomass, if available. How?
Perhaps you are familiar with wood ash, the remaining material after you have been burning logs in your wood stove - the same amendment farmers can use on the land or in the garden. It is typically known for how it can contribute potassium – a macronutrient for plant growth.
Figure 2 is an example of the nutrients in wood ash; note the high amount of calcium, potassium, calcium carbonate equivalent (a neutralizing value of acidity – similar to lime). The wood ash of course is missing one of the pivotal inputs that can limit the growth of the next generation on the land-- and that is carbon. It is a necessary staple ingredient on the recipe of a healthy forest.
If we take the time to look at the forest soil profile (or dig a bit), we will see very different residual organic matter as well as carbon in the forests that have been managed for utilitarian purposes. You can see the carbon in a forest floor that has been allowed to accumulate without removal, it is a black distinct line just below the leaf litter (it looks like wood ash but darker like soot from the chimney). If the forest carbon has been utilized through: historical overgrazing, clear cutting, and removal of wood (carbon) off-site, earth worms that digest carbon into rich nitrogen excretions, or land leveling for a homestead it will be seen in the soil profile. We also influence the forest floor without even removing material, just our decision process of what to drop and what to keep in the forest can influence the soil ecology. By choosing select species and cutting the other ‘unwanted’ species we are scripting the chemical makeup of the forest floor, each tree is contributing their leaves and litter to one degree or another. We are cultivating what we want to see and are choosing to change the composition of the soil ecology. Perhaps we can work with the inherent intelligence of the land?
How important is it to leave wood on the forest floor or manage for diversity? Can we break it down into a tangible number or make connections to the forgone value? Absolutely! If you can imagine the unraveling of a sweater by just the pull of its thread, there is a visible cascade. In the scenario of all wood removed: now the land is newly exposed to the elements, the fungal population has minimal carbon to actively digest and will regress, residual seed bank from the forest starts to grow but begins to draw carbon reserves from the soil to do so, the land is exposed with little resistance to erode from intense high rainfall events and valuable topsoil is washed downstream off the land. Fertility of the forest moves into an extraction phase, losing nutrients for regrowth by way of erosion and the nutrients required to regrow what was there.
You will see the difference on the forest floor if you visit an area that was historically timbered or in agriculture, versus one that has been minimally grazed, timbered, unmanaged, or adjacent to agriculture that introduced worms at some point. If we acknowledge the past management and recognize how much carbon has been removed and not added back, it can create an understanding of how we move forward for our forest production and watersheds – principally to keep, add, maintain the carbon that was extracted in the past. Of course, we can utilize the forest for the all the reasons we may want to manage it – maple, timber, foraging, grazing, recreation, and wildlife goals!
There is a rule of thumb when we graze animals on the landscape, “Take half-leave half.” The farmer and backyard gardener practice this intent when they apply manure or compost after their harvest. Carbon that we leave will benefit production and us via the: forest food web, watershed, future forest ‘nutrients,’ filtering of ground water and a clear way to create diversity and complexity on our landscapes.
Perhaps there is wisdom in leaving some residual for the next ‘crop’ while remembering our forests are on a longer time span as well. There are remarkable payoffs to considering the nutrient needs of our forests, consider all the additive benefits to balancing our needs with the needs of your land!
Give and take, the true barter system!
