Two of the other forest stewards and I were planning 2014 (the planning was fun and we’re looking forward to the activities), and the question of plant diversity came up. How much had we increased native plant diversity in North Beach Park? We had a couple plant lists handy, and were quickly able to come up with a pretty good idea. Other than the first order (made in 2011, before I barely knew anything), we’ve concentrated on ordering plants we knew to be under- or unrepresented in the park. Once I got home, I looked through previous lists and came up with a pretty definite figure.
But first, why does increased native plant diversity matter? It’s such a mantra for forest stewards the question deserves to be asked.
- It provides more food sources for the creatures that eat plants. That’s, basically, everything else. If a creature doesn’t eat plants directly, it eats things that eat plants. More insects eating plants means (we hope) more birds eating insects. Invasive plants don’t provide food for insects that eat plants, which is why native diversity is important.
- It also increases the length of the bloom season. Particularly helpful are plants that bloom early in spring or late in summer.
- The greater variety of food sources and extended bloom time are examples of functional redundancy. There isn’t just one plant blooming, but several, which serve different pollinators. And there isn’t just one genus of wetland plant filtering the water, but three or four.
- It improves the soil structure with a diversity of roots. Plants taking water from the soil and releasing it through their leaves (evapotranspiration) is important to soil stabilization. And a variety of root structures will make the soil more lively, which will feedback and make the soil better for the root structures.
- The Pacific Northwest forests need plants at every canopy level — from ground covering forbs and ferns up to the tallest Douglas fir trees. Because (see first item) there are things that eat plants at every level.
- Many of the forest types we target in our restoration have similar plant communities and associations, with the main difference being proportions between the plants. Planting with as wide a palette as possible provides the opportunity for the plants to sort themselves out a bit.
- Plant diversity also builds in resilience to disturbances, whether fire, flood, famine, or climate change. And given that we work in a ravine, we could well be creating a refuge for many plants to escape the worst effects of climate change.
I’m sure there are more reasons, but this is what I can think of off the top of my head.
Oh, the statistics. We — the people engaged in restoration in North Beach Park, whether EarthCorps, a crew contracted by the Parks Department, or people working with Friends of North Beach Park — have planted 63 different species of plant in the park. Of these, 39, or 62%, were unrepresented in the park. Note that these aren’t necessarily rare plants, they’re just unrepresented in North Beach Park. And I’m not saying we’ve increased the diversity by that much. That would need a complete survey of all the plants in the park, native and invasive. But it’s still a fairly good number.
Mirrored from Nature Intrudes. Please comment over there.