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California, Fire and Plants

Cooperation versus Competition

California native ecosystems and the way they work (cooperation) are very different from the way the plants in a common garden grow (competition). Most of the horticultural perennials and annuals people raise in the garden are at best weakly dependent on underground ecosystems and each other. Why should they be? We water and fertilize them; we see immediate results, in faster growth, more flowers, longer flowering time, etc. Also, many garden plants have been hybridized and improved, etc. so that they hardly resemble their relatives in the wild. Many of these garden flowers are what are called ruderals (many, out of their native habitat, are the weeds of the world ). Ruderal plants need a mineral and moisture-rich environment to flourish. Ruderal plants rely on a strategy of getting theirs first through competition, flowering quickly, and quickly producing many, many seeds to out- reproduce their competition. They do not cooperate with other plants in the vicinity by sharing water and nutrition. They quickly capture the available water and nutrition in an area, and are on their way! Ruderal plant life cycles are based upon year- to -year strategies, with little or no long-term strategies (that is, ruderal plants are mostly annuals, or short-lived perennials or biennials). In contrast to most gardens, the native ecosystem is a well-ordered, long-term system. (In California we also have annuals, and if they are taken to other areas, they can become weeds, such as the California poppy, in areas of the eastern U.S., but in their natural habitat they are more dependent upon the plant community, and do not exhibit ruderal plant tendencies.

Drought? Not comparatively.

In tree ring studies of the last four hundred years, the 1900's have had a surplus of rainfall. California has not seen a period of extended drought for the last one hundred years. The worst drought in California was between 60-80 years long. There were also many of 20-22 year duration. The wettest ten-year period was 1975-1984. The driest period for California as a whole was around 1625. The driest year in the last 400 years, for Santa Barbara, was ½ inches of rainfall in 1841. As no rain was actually reported this was probably all fog. The studies have been implemented in cycles as they relate to humans, not in plant community cycles. The periods of time under which the studies were undertaken are simply too short to be valid. Under our seasonal drought stresses the California native plant communities have shifted from competition to cooperation. (A variation of this exists in any stable pristine ecosystem in the world.) In other words, the plants grow much more slowly, and react to stresses much more slowly, and everything that happens, happens more slowly. For example, if you inherit a very large, old oak tree, and you plant a lawn under it (this would be considered a stress to an oak tree because most oak trees in California usually do not receive summer rainfall), the oak tree will die, but it may take decades.
With the state's 12-70 year drought periods the seeds of the native annuals and short-lived perennials have to remain viable for years (they do; after a fire, we've seen the best show of California poppies on a chaparral site that had not burned for 70 years). Our longer- lived native plants need to build a seed bank over a period of years in order to have sufficient numbers to regenerate during the 2-7 years that have normal or above normal rainfall.

Mulch and weeds don't mix

Most of the chaparral plant species need a mulch or litter layer (except for the grasslands and desert) that will gradually form as the plants reach their maturity. This mulch and litter layer needs to make soil contact; standing annual, introduced grasses or other weeds will block the formation of the litter layer. These weeds need to be removed and kept out, because they will prevent succession of the plant community and help to cause the death of the long-lived shrubs and trees.
Most California native plants grow and reproduce under a short-term and long-term community-oriented cycle. In California's environment the whole has to support the individual and the individual the whole for all to survive (a.k.a. mutualism).
Native plants of the valley grassland, coastal prairie and most other California plant communities survive because the ecosystem is a protective, closed biomass system (all the biomass in the system is conserved and recycled) based on plant community, mycorrhizal community, climate and soil types. The primary mechanism for the moisture and nutrient transfer in these systems is based on mycorrhizal associations. In our grassland, desert, and oak woodland communities, the natural cycles occur in one season, without a classic climax species. The traditional idea of a climax species doesn't pertain to these communities because these communities are not based on competition, but instead, on cooperation. What does this mean? You just talked about succession, now you say no???
1700)(three to six drought cycles before a fire.) In wetter areas the long-term cycle may extend to 250-400 years. We're also concerned that a number of 'good' bacteria and fungi that cycle through in the natural succession have disappeared under this non-supportive cover. (If a fire only occurs every 130 years naturally, how many of these interrupted cycles can our rare flora tolerate?) (Box et.al.; Hanes; Horton & Kraebel; Humphrey and Mehrhoff; Keeley et. al.; Morrison & Swanson; Zedler, et. al.)
the mycorrhizal associations at the same level as plant associations and blurring the distinctions of what we see above ground and below ground. In most cases people have been treating and reacting to the above ground effect of these biological interactions and not recognizing the ecological significance of the underground microorganism community.

Alien Invasion

It is very important to note that before and after the 1979 fire there were no alien plant species in the chaparral; the grassland and foothill woodland plant communities only had wild oats (Avena fatua).
The other important note is that when the annual, fire-following wildflowers died down for the summer, they left little litter. Clean bare ground is normal and healthy. (The same situation occurs in other relatively undisturbed plant communities; wildflowers waist deep in early spring with no weeds, in summer, no litter or dead matter taller than 1”, with bare patches in between, on the same site.) This leaves no fuel! Compare this with the introduced species like yellow star thistle (Centauria sp) or rip gut (Bromus diandrus). The fibrous stems stay erect and flammable long after the plant is dead.

Notes on California's ecology

We have spent the last 17 years trying to develop strategies to overcome the introduced weeds on this site (and others). We have had to reevaluate our 40 years of experience in California native plants and the theories we learned in college. Below is the information we have learned to date about 'restoring' a 'grass'-seeded site and why it is necessary to at least try to partially restore the site.
After 17 years the star thistle is in decline(waiting for the next fire, that its debris favors) but the Bromus (grass) and Erodium that CDF (CAL fire) seeded has spread to the non-seeded areas carrying another fire into a formerly clean area and killing more oaks and pines.
1. Much of the data on the ecology of California has been fatally (for the ecology) flawed by misinterpretation or misunderstanding the parameters of our ecosystems.
a. Any fire data based on midwinter or spring burns is invalid. Wet soil kills the underground biomass. (Dunn, et. al.) Many of the herbivores are in hibernation in the winter and are left alive in large numbers to eat the new growth as it emerges.
b. Any herbivore study based on small-scale data is invalid. Our wildfires normally cover thousands of acres, pushing the herbivores long distances away from the seedlings or crown sprouts.
c. Any excess nitrogen will force a decline of the mycorrhizal community. (Arnolds). So why do the researchers insist of fertilizing native plant communities? California does not have highly fertile soils in any plant community (other than Riparian) unless the community is destroyed or burned because the community structure limits the nutrition of the site. That is, if you test a site with fertilizer you kill or greatly suppress the mycorrhizal associations on the site, completely changing the ecology of the site.
2. Any study that looks at only one variable without including the variations caused by other variables is not valid. (D. J. Read; Read, et.al.; Coleman, et. al.)
3. Broad-based studies are much more valid and give better data. For example, Medina and Silva have an excellent graph of the effects of the underground biomass (mycorrhizas are the main component) and above ground biomass (plants) after a fire in the Venezuela savanna. It shows the mycorrhiza supporting the plants after a fire and then the plants recharging the mycorrhiza as the plants recover and grow through their seasons. The more variables included the more valid the study. Mycorrhizas are left out of most studies. They change dramatically the results if they are included. (D. J. Read, Pankow, et.al.)
4. Any study that looks at short-frequency fires as a normal occurrence is fatally flawed. (Zedler, et.al.)
5. Any study that looks at our California ecosystem as a ruderal-based system is fatally flawed. (Grime; Grime et. al.; Perry, et. al., Pankow, et.al.)
6. Any study that looks at a California ecosystem in months instead of decades has major limitations and may be fatally flawed.
7. If the information does not seem valid, question the source. Ask for references and experiences. (Bad researchers quoting other bad researchers! If you do not recognize any of the references or magazines there may be a reason. If all the quotes are from range management, fire, and trade type journals maybe it is not sound ecology you are hearing. Journals called the likes of Billy Bob's Wildland Revival or University Agriculture and published by a chemical company may be suspect.)
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Edited on Aug 19, 2013. Authors:
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