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May 2011
Where have all the wildflowers gone ????
Are prescribed burns effective in weed control at the Santa Rosa Plateau Ecological Reserves?
I have enjoyed the wildflowers and the ecological setting of the Santa Rosa Plateau for over 30 years. However every year I become more and more discourage and frustrated from the decline of wildflowers caused by the choking effect of non-native invasive weeds.
A good majority of my photos on this site were taken on the Los Santos, Trans Preserve, and the vernal pool trails. This last year only a handful of native wildflowers were found on these same trails. I have noticed this rapid decline of wildflowers in the last 10 years.
I suspect that the prescribed control burns have a lot to do with this decline.
Fire ecologist will tell you that burning has little effect on wildlife. I have talked to fire fighters who have participated in these burns and they tell me different. I have personally found burned reptiles in prescribed burns that I have been involved in.
In a natural fire, the fire starts at one location and usually moves in a certain direction, allowing wildlife to run for their lives or take cover. In a control burn they ignite the fire at opposite ends of the area to be burned, in some cases they practically light the whole perimeter, so that the fire will burn inward towards the center. This prevents the fire from getting out of control, but has a more trapping effect on the wildlife.
Prescribed burns can and have been beneficial in controlling weeds. However, in the case for the Santa Rosa Plateau, where the burning is only done on the grasslands, the opposite effect seems to be occurring.
In a recent article in Fremontia, Journal of the California Native Plant Society, April 2010, by Adam Lambert, Carla D’Antonio, and Tom Dudley, commented, “Fire is not considered a key factor in the maintenance of invasive plant dominance, nor an appropriate management tool for eliminating non-native species in most California grasslands.
After 30 years of personal observation, I have seen a tremendous decline in wildflowers followed by an increase in weeds.
Avena or wild non-native oats, and Erodium, two of the major invasion culprits, have probably been growing on the plateau for over two hundred years. They are not recently induced exotic weeds. Up to mankind attempts to control them, they have not been a real problem. I believe they have always been kept in check by the natives and have not been a real deterrent to the native wildflower population.
I remember 15 or 20 years ago, when Poppy Hill was covered with mostly Poppies and Bush Lupines with very few weeds. What a pleasure it was walking thru the Poppies and Lupines. This year and previous recent years you will only find a handful of Poppies and Lupines, if you are lucky.
Many years ago management decided to do a prescribed burn of Poppy Hill. I was told it was a very hot burn. Was the delicate soil mantle damaged? Did the burn cause an opposite effect in controlling weeds? Was there an acceleration of weed growth the following years? I believe so.
I remember you could drive down Tenaja Road and see fields of blooming wildflowers. Something I haven’t seen in many years.
Dickens and Allen of University of California at Riverside have done wonderful work in analyzing the results and benefits of the prescribe burns at the Santa Rosa Plateau.
The study conclusions:
- Fire decreased non-native grass cover for the length of study.
- Native species richness was initially increased with both fire treatments.
- The increase in native diversity is mainly in fire following species.
- Non-native forb cover increased with burning.
- Native forb cover increased in burn + weeding treatments.
- Erodium spp are competing with Nassella pulchra slowing recovery.
Comments on Conclusion # 1 “Fire decreased non-native grass cover for the length of study”
There is no question on fire destroying a large amount of the non-native grass seed, providing the burn is done in a timely matter. Often the burns are done after the majority of the weed seed has dropped to do any good. Once the seed drops to the ground, the fire has less effect on killing the weed seed.
I assume the quantitative weed count from these study burns was determined by counting the seedlings in square meter area plots. However, what is more important is not the actual number of the seedlings counted, but what is the size of the area taken over by the seedlings.
I believe that burning benefits the weed growth by a thinning out effect, allowing the weeds that do survive more room to grow and flourish. Something like thinning out your carrots seedlings in order to produce fewer but larger yields.
Generally, a weed with less competition from the other seedlings will grow larger and have a greater smothering out effect on the natives. The total seed produced from these surviving non-native plants will cause them to disperse their seed a greater distance than the seed from many smaller plants, the surviving weeds will be much larger and be more prolific when it comes to seed production. In other words a few robust plants will produce more seed than a bunch of little crowded out plants.
It stands to reason that a larger weed seed will have a greater survival rate than a smaller seed during a prescribed burn. Any plants-man will tell you a larger seed will initially produce a more robust plant. Are we creating “super-weeds” by selecting out the more robust plants with the larger seeds?
Comment on Conclusion # 2 and #3 “Native species richness was initially increased with both fire treatments.” and #3 “The increase in native diversity is mainly in fire following species.”
This may be true but the weeds usually choke the fire followers out in a few years.
Comment on Conclusion # 4 “Non-native forb cover increased with burning.”
So why do we continue to burn?
Comment on Conclusion # 5 “Native forb cover increased in burn + weeding treatments.”
Why not weed treatment only? Why encourage non-native forbs?
Comment on Conclusion # 6 “Erodium spp are competing with Nassella pulchra slowing recovery.”
Again, why are we burning?
Other factors that may be overlooked
What are the differences of nutrient requirements for natives vs. non-natives?
Most natives have a symbiotic Mycorrhizal relationship going on for them. The benefit of this symbiosis is that certain fungi survive symbiotically on plant roots increasing phosphorus uptake for the plant. Most weeds are non-mycorrhizal and need to uptake their phosphorus directly from the soil in order to survive.
It is known that nutrient rich soil promotes rapid weed growth, just as nutrient rich run off water does in promoting algae in our lakes.
The ash resulting from a prescribed burning could contain as much or more nutrients than steer or horse manure. Ash may be rich in nitrogen, phosphorus, potassium, manganese, and especially calcium. A large percentage of the nitrogen vaporizes into ammonia and nitrogen gases, but in some studies the usable nitrogen content in soils actually increases.
Normally organic material or dying plants take time to decompose. When burned, the decomposition time is hastened, allowing excessive nutrients to be released all at once into the soil during the raining season.
In phosphorus rich soil, native mycorrhizal systems begin to shut down, giving weeds a growth advantage. Normally, non-mycorrhizal weeds grow very poorly in nutrient deficient soils, allowing the natives to live in dominance like they have in the past.
I am no expert, but I have been involved with managing 10 different preserves in Southern California and one thing I have noticed and learned was when and where a healthy native environment exists, weeds do not present a real problem except along the perimeters of the preserves where the soil has been disturbed. Man-made trails also require weed management.
There is a theory that nitrogen air pollution is causing increased weed growth. This may be valid but the srp has relatively clean air.
Maybe there is another factor causing this wildflower decline. I wish the experts would figure it out, because in my mind, there definitely is a serious decline of wildflowers. Ask any “old timers” like myself and they will tell you the same. The burning practices don't seem to be working.
If you support or disagree with me, please email me - Keith@California-Natives.com
I would be most interested in your views and comments. Pro or Con, I will publish them on this web site. www.santarosaplateau.com
Thanks,
Keith Haworth
Keith@California-Natives.com
Comment from Ted St John PhD, Environmental Ecologist
Interesting thoughts, Keith. I have a lot invested in all of these things. These concepts are complex and interrelated. I did my Ph.D. in fire ecology and its effects on mineral nutrition, most of my research on mycorrhizae and mineral nutrition, and have now been doing restoration since the mid 1980s. All of these points are of great interest to me, and I agree that we are not even close to all the answers. It really would be a lot easier to talk than write about.
I have not thought about the point that the crew burns from all sides at once. I thought the problem was that prescribed burns are in late spring and natural burns are in the fall. I think you might be quite right about that point, however.
There is also a big effect of fire frequency. Annual grasslands can stand up to just about any fire frequency. Native grasslands might be able to burn every year at least for a while, but they might suffer at that frequency in competition with annual grasses.
The mycorrhizal question is not a full answer and not as simple as I may have made it sound. Annual grasses can definitely become mycorrhizal but most probably do not have to. Erodium can show a bit of colonization but I have never seen more than a couple of little spots. The biggest mycorrhizal effect in weed control probably has more to do with permeating the soil with a network, not just making individual plants mycorrhizal.
I think Tom might have records that could help evaluate whether flower abundance is really dropping. Some years it seems that way but Linda and I have photo collections from recent years that seem to be as good as anything I can remember from the 80s or early 90s.
Have you ever seen Kathleen and John Hamilton's patch of native grassland? It seems to be about as resistant to annual grasses as anything on the reserve. That apparently has something to do with John's annual January joy ride on his lawnmower. This all fits in with my "unified theory of weed growth," something that I have applied the last couple of years on restoration jobs. I think the weeds are beatable but only with a quite specific regimen of natives, mycorrhizal fungi, certain types of low-impact weed control, and holding your ears just right.
Finally I do not see soil algae in this equation. They need to be. Maybe we can talk through all this soon.
Thanks for the post!
- Ted
Keith's response:
Hey Ted, Yes, I know you have done a lot of work in fire ecology, I appreciate your input and everything you taught me about mycorrhizae.
I am so bummed out finding very few of the native wildflowers on the trails this year that I have seen in abundant quantities in the past.
We burned about 10 acres at Johnson Ranch, it was mostly all Erodium before the burn and afterwards about the same. The purpose of the burn was for the Burrowing owls. I don't know how it is now.
As I remember, Poppy Hill was heavily infested with Erodium after the hill was quite abundant with Poppies and Lupines.
No, I haven't seen Kathleen's native grassland.
Thanks for your expert response, do you mind if I put it on my site?
- Keith
Comment from Zack Principe, Biologist and Ecologist for The Nature Conservancy
Hi Keith, Good to hear from you. This is a very complex subject and you make some good points, but in many of the areas you mention fire having reduced the wildflowers, we have only burned 2-3 times in 27 years. It averages out to each area of the reserve only being disturbed once every 11-12 years since it has been protected. This is in contrast to being grazed by livestock continuously for 100+ years. So, prior to protection disturbance was the norm. There were only a few years between when the cattle were removed and fire was started as a management tool, so I doubt that the good flower years were the result of this very short time with no disturbance in a 100+ year history.
My thought is that we may not be disturbing the grasslands enough be it with fire or grazing or whatever to create openings for native wildflowers. Poppyhill is actually probably a great example of this. Poppies and some lupines follow disturbance. With the lack of disturbance these species have been lost due to thick thatch layers created by non-native grasses. This site was actually part of the first acquisition, so cattle were removed in 1984 and it has only been burned twice since then. To me makes more since that the lack of disturbance following 100+ years of annual disturbance has lead to the change rather than 2 fires in 27 years killing all the native plant seeds. Could be wrong though.
The early years as you call them on your site likely were still influenced by recent cattle grazing (not removed from Sylvan until 1996, Hidden Valley 1995 and much of the low grasslands between the mesas until 1991) and high fire frequency as a result of large wildfires in the early 1980s and aggressive prescribed fires in the late 1980 to mid 1999. We have only burned more than 200 acres or 5% of the grasslands in a single year since 2000 and in 3 years had no fires at all. There was at least one year in the early years that we probably burned more in a single year than we have in the last decade combined. The fact that we are not seeing “recovery” after significantly reducing the frequency of fire again leads me to think too little rather than too much disturbance. Back to poppyhill, last time it was burned was 1997. It is hard for me to believe poppies which thrive naturally on my acre of weeds that was mowed and lightly graded each year for 20+ years before I bought it and that I continue to mow multiple times during the winter and spring, have vanished as we somehow disturbed them too much at SRP.
It is also hard for me to believe that our use of fire differs so dramatically from the fire regime present before European arrival that we have burned up all the native wildflowers. As you allude to on your site it may only take one hot wildfire in the past to eliminate certain species. I am not sure how frequent the fires were before records were kept, but they were part of the landscape with large wildfire in 1945, 1980 and 1981 that burned portions of the grassland at SRP. From what I have read, fire was also commonly used during the Spanish times to clear chaparral to create grasslands and the native Americans used fire to manage game and plant habitat before them.
It seems more likely to me that we have gone the other way and decreased the rate of disturbance below that necessary for the maintenance of wildflower dominated grasslands. Also, in multiple years recently we have had the unfortunate fortune of getting early rains (early and mid October) which greatly favor non-native annual grasses leading to what is referred to as a grass year. From what I have heard and observed 2011 was a grass year in the grasslands throughout California. The concept that all we need to do to preserve a place is buy it and put a fence around it has been shown to work in only very rare cases, say such as chaparral here in California and even that we now need to protect from too much fire somehow. Many systems and even more systems dominated by herbaceous vegetation communities need management as they are not the climax community in most environments. With the massive alteration California grasslands have faced with the invasion of non-native annual grasses and forbs, it is has been shown that no management is generally worse than active management. California grasslands are one of the most altered vegetation communities on earth, they need management. Is fire the only tool, no and we are looking into other tools as well. We have returned cattle to the reserve and will likely start a larger scale mowing program in the future as air quality issues eliminate fire as a management tool in southern California.
I now do a lot of work in the Sierra foothills and visit large ranches. On the ranch I was focused on this past spring, the only pasture that had good wildflower displays was the one that was grazed in the late fall through spring. With the early rains and early grass germination, it appears grazing of the annual grasses early in the growing season knocked them back enough to counteract the positive effects of the early rain for the annual grasses.
I also do some work in Orange and San Diego Counties and unfortunately, there is recent trend across the region in all vegetation communities toward increasing cover of non-native annual grasses. Their cover has increased every year since the start of the monitoring project in 2007, so not a good trend throughout the region. This follows a similar trend we started observing in the grasslands at SRP in 2002, in which we saw an increase until 2006 when we stopped collecting data (again on average only about 100 acres/year burned during the time this data was collected).
I have just unearthed some data from 1986 to 1990 and a quick look reveals that they found the same players Bromus mollis, B. diandrus, Avena and Erodium as the dominate species along with Nassella. They actually do not mention native forbs which makes me think they must have been very uncommon in a majority of the grasslands back then.
The conclusions of Lambert, D’Antonio and Dudley are absolutely correct, but also irrelevant to anyone that has management experience. There is no hope of ever eliminating non-native species from California grasslands, but they must be managed in most situations. Yes, there are certain soils that will support a primarily native grassland without management, but those make up a small component of all our grasslands.
There are grasslands at SRP that have not been burned, visit them and let me know if you think they are that much better than the rest. The areas are: Sylvan Meadows on the outside of the road that arches through it. The area south of Fault Road between the pond and Waterline Rd.
My conclusions are that we don’t know for sure, but that seems very unlikely to me that after native America burning for 1000s of years and then 100+ years of cattle grazing and fire that one fire approximately every 10 years would be the cause of such a negative change.
Glad you asked as always good to keep thinking about these things,
- Zach
Keith's response:
Thanks Zack for your very informative input, everything you say makes sense. However, it seems that I no longer see fields of Buttercups and Chocolate Lilies as I have in the past.
Maybe this year will be different, I hope so. To me Poppy Hill is a mystery. Why do we continue to have spectacular blooms of Poppies along Hwy 15 when we have a good super rainy season regardless of fire disturbances the prior years. Is it because the soil may be a little more soil deficient than at the srp and not as conducive to growing weeds?
Response from Zach Principe, TNC Biologist/Ecologist
Not a problem. The poppies and other wildflowers along I-15 are awesome and when I did some consulting work in those area back in the early 2000s when I was collecting the data at SRP, there was no comparison, those area have way more diversity and cover, period. My thoughts are in addition to the deficient soils (well drained dg) are that there have been a lot of fires in that area (1944, 1957, 1978, 1981, 1987, 1988, 1995, 2004) and that it is type converted chaparral and sage scrub. As a result, we are seeing a lot of non-grassland wildflowers that keep coming up because the native shrub cover needs 20+ years to recover and just can’t with all that fire. This is in contrast to the grassland wildflowers at SRP, they are not fire followers, the same ones show up everywhere, we just generally see more in recently burned areas.
On your chocolate lily comment, a really bad thing has been happening the last few years, people have been reported digging them out along the trails, so could be part of the reason not as many, though I had hoped the problem was not that big. Contact your county supervisor and demand more county rangers to help save not only SRP, but all of riverside county’s parks before they become no more than just overused urban parks. We have tried, but think the politicians need to hear it from the people not us.
- Zach
Comment from Tom Chester
hi, keith, zach, ted and michael!
keith, you're exactly right to raise these issues; they are important ones.
zach has given you a wonderful extensive reply, to which i can only add a few comments.
note that i am not an expert in grassland management; these are just my observations, and i welcome feedback if my conclusions are incorrect. you are welcome to put my thoughts online at your site. (you may wish to restore capitalization, though!)
- non-native species have changed the whole equation for grasslands. the grasslands are now different from what they ever were before. i echo zach's comment that active management is needed to prevent our grasslands from eventually becoming 100% non-native species.
- some areas of the srp are currently 100% non-native grasslands. the only hope for those areas is restoration, active planting of native species, after killing off everything that grows there. carole bell has managed to restore one area near the old entrance by active planting.
- fire works temporarily to decrease the non-native cover, and produce much better bloom displays the following year, for at least two reasons. first, with the removal of the tall non-native grasses, you can actually see the native blooms. second, the increased sunlight, nitrogen, and water in the soil probably promotes increased native blooms, such as for blue dicks and calochortus.
- while something like 99% of our native nassella plants survive a fire, i've observed a number of dead plants that don't. since there is very little nassella recruitment, since baby plants can't compete with the non-native species sucking up the water, my fear is that every fire decreases the number of nassella plants by something like 1%. thus continued fire now, in the presence of non-native weeds, without active planting and nurturing of nassella seedlings, will eventually result in the elimination of the native nassella plants.
- it seems to me that grazing by species like cattle (not like goats, which pull up perennial roots) is one of the best management actions we can take. if cattle eat the non-native grasses and prevent them from seeding, eventually they will be eliminated, or at least much reduced. i am very heartened that the srp has begun experimental grazing programs.
- in addition, active weeding programs are needed to try to eliminate as many non-native species as we can. much more manpower needs to be devoted to this. i see two main programs. first, target a few species, or just one, and totally eliminate them from the srp. once you eliminate a species, it is no longer a headache. second, target the healthiest areas, with the fewest non-natives, and start actively weeding ALL non-natives from a small patch. with time, that patch will have no non-natives in it, and the weeding target area can be enlarged.
such highly intensive management is the only hope of restoring a native grassland. the only way to do this is with a large crew of volunteers, since the money simply isn't there to hire people to do this.
- in response to your main question, "where have the wildflowers gone?", i think fire is largely irrelevant. it is the non-native weeds, uncontrolled by grazing, that are primarily to be blamed for lessened displays.
for example, one of the best goldfields display in southern california, accompanied by tidy tips and poppies, is in the lake henshaw area, and has been produced and maintained by heavy grazing. the cattle there don't let the non-native grasses go to seed, and keep the ground close-cropped.
see wayne armstrong's first pix here:
http://waynesword.palomar.edu/coycrk1.htm
to my knowledge, this display happens every year with decent rainfall.
- zach is exactly right when he talks about "grass years", where early rains germinate the non-natives, which then grow tall enough to significantly suppress the natives and hide them.
but we still have excellent bloom years. in particular, the year after a drought year, if it begins with enough rain to germinate the natives as well as the non-natives, will still produce spectacular displays.
there is so much variability in the showiness of the bloom, depending on rainfall and temperatures, that you have to be careful in concluding that there has been a long-term change from just a handful of years.
to see some of the variability in the srp bloom, see the plots here:
http://tchester.org/srp/plants/blooms/2005/showiness.html#showiness
- tom chester
For continuation of this discussion go to http://santarosaplateau.com/0/