Sunday morning I took a couple of hours at Jericho Park; it was lovely even though it was a bit rainy. It was reassuring to hear some tree frogs, and it’s always nice to see the ducks (and hear them guffawing at their little private duck jokes).
The lovely folks at Evergreen and the Jericho Stewardship Group take care of areas in this park (as well as monitoring water quality of ponds and attracting beneficial insect species, and lots of other great projects) and about once a month they take some volunteers and show them how to help out. On Sunday, we were pulling Himalayan blackberries (which are invasive and very successful…also pretty delicious when contained – I love picking them in summer). Ivy, morning glory, and scotch broom were some other ones that need to be removed, although they weren’t today’s focus.
The thing about invasive plants is that they choke out other species (especially native ones) by taking up too much sunlight or nutrients or water. What makes them invasive is often that they have been artificially introduced to areas where they do not normally grow (sometimes intentionally and sometimes accidentally), and so because they’re ‘aliens’, there aren’t enough animals or insects that eat them, or the other plants don’t know how to cooperate or compete with them, so the alien plants grow out of control. The result is that the amount of invasive plants gets too large for the area, and over time, all kinds of imbalances to the other plant populations, and even to the soil and to insect populations, can happen.
Today I learned that a good way to remove broom is by cutting them a bit below the level of the soil, so that the soil bacteria will actually start to rot the roots, thereby killing the plant for good. Often people just yank the broom right out, but apparently (I didn’t realize this before today) this can actually help distribute the seeds, so that the broom will just come back. So there you have it! Broom will also die off if there is too much shade covering it.
Evergreen folks reminded us of the importance of reclamation. When we pull out invasive species, it’s important to ‘reclaim’ that space by re-establishing native species, for example by planting trees. It’s also good to remember that even though plants like Ivy can choke out trees and cause safety hazards (trees die, rot and fall over eventually), they do provide functions like preventing soil erosion. This means that when we remove Ivy, we should put something else in its place to prevent the topsoil from blowing or washing away. There’s a really interesting group that does this in an artistic way; they actually dry out the removed ivy and blackberries, and then weave the dried plants into netting (‘bionetting’, or biodegradable rather than plastic netting), and put the netting down over the soil protect it from erosion temporarily. More on that here.
We then went and tested the water in one of the ponds as part of the ‘uncover your creeks‘ program (yay for Citizen Science!). We looked at turbidity (how clear is the water, as opposed to having lots of suspended particles or silt in it), pH, which was about 6.4 – a little acidic and a hair lower than we’d like to see; 6.5 would have been OK since the waters in the area are naturally a bit acidic, especially in winter due to decay and fallen tree needles – as well as nitrate and phosphate levels. In water ecosystems, phosphorous is more important for promoting plant growth, whereas on land, nitrogen is more important (it depends on what your limiting factor is, I think). We found that the levels of these in the pond water we tested were good – phosphate was 0.02 parts per million, and nitrate was 0.2 parts per million. It seems like very little, but if there had been more (especially more phosphate) then the pond could end up with algal blooms that would shield everything below it from sunlight, and prevent normal plant growth.
Want to take part? Look up the uncover your creeks program in MetroVancouer, Vancouver Island, and Toronto area as well.