The more I think about it the more I wonder about the advisability of pulling Broom and Acacia, both of which are nitrogen fixers. Could it be Nature is saying she wants more pioneer nitrogen fixers to build up soil nutrient levels, and when they have done their job, they may be naturally overtaken by newly strengthened natives? Could it be a lot of these nonnatives are not really competing at all but are actually helping the natives in the long run? Acacia grows fast & dies fast, thus laying down lots of woody debris. Could it be Nature willed those Acacias to grow and is saying her priority is that she needs more rotting biomass to feed the soil ecology (and stop erosion and store water), then when it is restored to health the conditions will be right for a more native slower growing but longer lived self-sustaining community to regrow? I wonder if we should focus less on taking away natives and more on building up the soil and adding biomass to the system.
I am reminded of a quote from Food and Healing by Annemarie Colbin: "In the world outside our bodies, whenever there is a pileup of garbage, insects and scavengers come to break it down and convert it into something useful, such as humus or compost. So it is inside our bodies: If there is a pileup of waste matter accumulating, the immune system decides it's time to clean up. It then provokes, say, a cold, or some other mucous discharge to flush out the obstruction, calling in an army of bacteria to help dispose of the stuff. It is unfortunate that we have come to misread these minor cleanup reactions as illnesses and thus undesirable. Interrupting this process with aspirin or antibiotics is akin to killing the cleaning lady in the midst of her spring cleaning, when everything is a mess. Major infections such as meningitis or pneumonia occur most frequently in the wake of minor infections, precisely because the minor infection's task has been incompletely fulfilled."
While landscapes going through infections of non-natives have suffered damage in places, I wonder if it may not always be as chaotic or bad as it seems, and Nature may not always be as hapless and powerless as we presume. At a Yellow Star Thistle pulling work party I was struck by a California Native Plant Society member's take on it: it's Nature's answer to overgrazing; when the land has been abused, Nature puts Thistles there to keep the abusers away and protect it while it heals itself.
The more I find out the more I grow to appreciate the wisdom of what organic farmers say: their primary focus is not growing crops but growing soil, since if the soil is healthy and wealthy, the plants can take care of themselves.
Just as people and plants are susceptible to certain diseases when under stress or when certain nutrient levels are deficient, excessive, or imbalanced, the same must be true of landscapes. Is it possible to read the deeper problems in the ecosystem from what invasions or other disturbances it is susceptible to? Would it make any sense to catalog what weeds are causing problems, and what their ecological roles and nutrient effects are (nitrogen fixing etc etc), to see if patterns develop?
If we do decide to kill some trees, why not save time & energy by girdling them rather than cutting them? Does anyone know if girdled trees resprout like stumps do, so we can also save the ongoing time & energy drain of continually returning to deal with resprouts?
Some other ideas for conserving biomass: Facilitate composting of kitchen and yard wastes by people in the watershed. Could we get a chipper onsite, or place a chipper on Park Blvd and have it dump its output on the fill area that is bare of trees to build some soil?
Has there been any monitoring of soils and soil ecology in the Sausal watershed? Anybody know local or California people with experience in soil microbiology? Have any Sausal people more experienced at working with soil than the rest of us noticed any differences in the soils where natives are doing well and the soils where exotics are rampant, or between soils that have good cover and soils that are bare or eroding? As we work in the watershed, it would be good to pay attention to indications of soil ecosystem health, and see if any patterns develop.
We may want to consider organizing propagation of soil microorganisms as well as plants, especially for anywhere natives are not faring well and for fill areas such as Bridgeview meadow & its eroding slope, the El Centro pool banks, and the spot by Park Boulevard.
I'm interested in learning more about how natural succession works, and would welcome any tips on where to go to learn more.
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>As an example of oak/acacia interaction, look at the area just upstream of >El Centro on the side opposite from the creek. Those oaks had essentially no >sunlight for decades until we cleared the acacia last year.
How do we know the Oaks weren't weak not as much due to shading as due to soil deficiencies, which the Acacias are in the process of correcting?
> With their fast growth rates and dense stands, acacias grew up right through > the middle of even mature oak groves and wipe them out by blocking sunlight.
I doubt very much the Acacias were threatening Oaks everywhere. If we can establish where they were and were not growing, and figure out the differences between those places, it may provide some enlightenment to help read what's going on in the ecosystem.
How do we know whether they are really competing? Oaks normally live centuries, Acacias decades. How do we know the Acacia isn't just a blip in the lifespan of the Oak it is popping up next to, and the Oak won't benefit more over its lifespan from woody debris feeding the soil & stopping erosion & holding water etc than it loses from the temporary loss of sunshine? Even if it kills an Oak, how do we know the Oak's neighbors & descendents won't get a net benefit? How do we know that, if what is most needed in that place is biomass to feed the soil ecology, and stop erosion, and cover the soil with a buffer against humidity and temperature fluctuations that are hostile to soil microorganisms, then killing some oaks, thus accelerating deposition of biomass, may be the optimal thing to restore the ecosystem in the long run?
How do we know that if we take out an Acacia something else won't pop up in its place, and Nature won't keep putting something there till she gets what she needs?
-- Walter Epp for7gen àt idiom døt com