The cold weather has arrived along with the need to grab an extra sweater in the morning, frost glistening on spider webs, and of course, crunchy leaves decorating the ground.
As a young child I never thought too hard about where the leaves end up after playtime was over. My family would rake them up, package them into a large bag then bring them to the compost center. But what about all of the leaves that were not destined to become garden mulch? No one (to the best of my knowledge) goes off into the forest to clean all the dead leaves, so, where do they go?
As busy humans, we seldom take the time to think about the role dead things play in the ecosystems around us. We like things to be neat and tidy not dead and decomposing! The leaves that have taken their leave (pun intended) from the plants from which they grew do not pile up year after year. Despite what we as humans sometimes think, nature does have a plan for all of its components, dead things included. Fallen leaves begin to decay with the help of our good friends bacteria.
Now bear with me for a moment, I know you are skeptical of my giving any positive connotation to bacteria. But it’s true! Bacteria does not mean just the nasty kinds that give rise to all sorts of upsets in our bodies; it also includes essential bacteria that live in our digestive tracts to help us break down food. Bacteria is in fermented dairy products such as yogurts, although those are normally given the name probiotics which is a much less frightening term to many of us. Bacteria is even responsible for the delicious kombucha that has taken Victoria by storm. Bacteria is essential not just for humans, but for all living creatures and processes.
Along with bacteria, fungus is another all-star saprotroph responsible for breaking down plant material. If you look closely at the dead leaves you may be lucky enough to see the characteristic hyphal tips, which frequently look like thin threads, extending to engulf the nutrient rich leaves. Saprotrophs, literally meaning the rotten (sapros) nourishment (trophe), live up to their name by externally digesting dead material with the use of enzymes then taking up some of the nutrients they released. Once the fungus has begun the first steps of decomposition, we look towards the many legged and legless to continue the process; our humble detritivores.
Just a few of the many creatures we have to thank for so effectively decomposing include detritivores such as pill bugs, millipedes, beetles slugs, snails and worms. And these are just some of the creatures we can easily see. If we were to take some of the leaves and soil and station them under a microscope we would be rewarded with incredible creatures that are typically alien to us: springtails, booklice and mites—oh my! By consuming and digesting plant material, detritivores are converting the components of their meal into a form that living plants will be able to take up. Elements including carbon, nitrogen and phosphorus are released back into the soil; allowing for new growth. I had an astute student of mine observe that “The dead leaves feed the ‘wormies’ the wormies make soil for the trees and the trees make air for us,” before looking around in awe at the leaves she had been traipsing through a few minutes earlier. Much to my delight this same student now regularly collects dead leaves she deems impressive and proudly brings them to me before relinquishing them to the wormies.
The processes described do not happen overnight; it can take months or even years for plant matter to fully decompose. While the decomposers are gradually working on cycling nutrients back into the soil, the plant matter is still providing shelter for all sorts of creatures over winter. Solitary bees being a major one. Although it is the charismatically social honey bee that tends to get our attention, solitary bees are frequently more efficient pollinators and are native to Vancouver Island. If their high level of efficient pollination doesn’t help you love solitary bees, the fact that they only ever rarely sting might help their case. As they do not have a nest to defend, they are very difficult to provoke into stinging. As with all stinging bees, it is also only the ladies that can sting you. Certain solitary bee species such as leaf cutter and mason bees will lay their eggs inside hollow plant stems holes in trees with a stash of pollen for the eventual larvae to eat.
Larvae of certain moths and butterflies are also not immune to the cold of winter. Many species in their larval form will curl themselves up in a dead leaf during the winter months and go dormant. It is easy for us to appreciate these pollinators in the spring and summer without realizing all of the components, both living and dead, that go into their life cycle. Instead of removing all of the dead plant matter in your yard and garden, try leaving a portion (or all) of it so that the organisms that rely on the plant matter for safety over winter have a chance of surviving. You garden will thank you two-fold, for the nutrients released during decomposition and for the pollinators emerging in the spring.
On your next walk, I implore you to take a moment and appreciate not just the stunning colours of autumn, but also the host of organisms benefiting from the seasonal change. Admire the slimy slugs, tip your hat to the armoured pill bugs and understand that they are all working towards a healthy environment for the benefit of all.