Editing Chaparral (section)

==Fire==
[[File:Chamise resprout Mag Road III.jpg|thumb|Chamise (''Adenostoma fasciculatum'') resprouting after a high-intensity chaparral fire]]
[[File:Post Fire Wildflowers.jpg|thumb|Wildflower display after the 2007 Witch Creek Fire, San Diego County, California]]
[[File:Hwy 60 Riverside County.jpg|thumb|Impact of high fire frequency: chaparral/sage scrub type converted to non-native grassland]]

Chaparral is a coastal biome with hot, dry summers and mild, rainy winters. The chaparral area receives about {{convert|38–100|cm|abbr=on}} of precipitation a year. This makes the chaparral most vulnerable to fire in the late summer and fall.

The chaparral ecosystem as a whole is adapted to be able to recover from naturally infrequent, high-intensity fire (fires occurring between 30 and 150 years or more apart); indeed, chaparral regions are known culturally and historically for their impressive fires. (This does create a conflict with human development adjacent to and expanding into chaparral systems.) Additionally, Native Americans burned chaparral near villages on the coastal plain to promote plant species for textiles and food.<ref>{{cite book |title=Fire, native peoples, and the natural landscape |last1=Allen |first1=Craig D. |last2=Baker |first2=William L. |last3=Bendix |first3=Jacob |last4=Griffin |first4=Duane |last5=Knox |first5=Margaret A. |last6=Parker |first6=Albert J. |last7=Parker |first7=Kathleen C. |last8=Vale |first8=Thomas R. |last9=Whitlock |first9=Cathy |date=2002 |publisher=Island Press |publication-place=Washington, DC |isbn=9781559638890 |oclc=614708491}}</ref> Before a major fire, typical chaparral plant communities are dominated by [[manzanita]], chamise ''[[Adenostoma fasciculatum]]'' and ''[[Ceanothus]]'' species, [[toyon]] (which can sometimes be interspersed with [[California scrub oak|scrub oak]]s), and other drought-resistant shrubs with hard ([[sclerophyllous]]) leaves; these plants resprout (see [[resprouter]]) from underground [[burl]]s after a fire.<ref name="Parker CA Ecosystems">{{cite journal |last=Parker |first=V. T. |year=2016 |editor-last=Mooney |editor-first=H. |editor2-last=Zavaleta |editor2-first=E. |title=Chaparral |journal=Ecosystems of California |location=[[Oakland, CA]] |publisher=[[University of California Press]] |pages=479–507}}</ref>

Plants that are long-lived in the seed bank or serotinous with induced germination after fire include chamise'', Ceanothus,'' and fiddleneck''.'' Some chaparral plant communities may grow so dense and tall that it becomes difficult for large animals and humans to penetrate, but may be teeming with smaller fauna in the understory. The seeds of many chaparral plant species are stimulated to germinate by some fire cue (heat or the chemicals from smoke or charred wood).<ref name="Parker CA Ecosystems"/> During the time shortly after a fire, chaparral communities may contain soft-leaved herbaceous, fire following annual wildflowers and short-lived perennials that dominate the community for the first few years – until the burl resprouts and seedlings of chaparral shrub species create a mature, dense overstory. Seeds of annuals and shrubs lie dormant until the next fire creates the conditions needed for germination.

Several shrub species such as ''Ceanothus'' fix nitrogen, increasing the availability of nitrogen compounds in the soil.<ref>{{Cite journal|last1=Kummerow|first1=J.|last2=Alexander|first2=J.V.|last3=Neel|first3=J.W.|last4=Fishbeck|date=1978|title=Symbiotic Nitrogen fixation in ceanothus roots|journal= American Journal of Botany|language=en|volume=65|issue=1|pages=63–69|doi=10.1002/j.1537-2197.1978.tb10836.x|jstor=2442555|url=https://www.jstor.org/stable/2442555}}</ref>

Because of the hot, dry conditions that exist in the California summer and fall, chaparral is one of the most fire-prone plant communities in North America. Some fires are caused by lightning, but these are usually during periods of high humidity and low winds and are easily controlled. Nearly all of the very large wildfires are caused by human activity during periods of hot, dry easterly [[Santa Ana winds]]. These human-caused fires are commonly ignited by power line failures, vehicle fires and collisions, sparks from machinery, arson, or campfires.

===Threatened by high fire frequency===
Though adapted to infrequent fires, chaparral plant communities can be eliminated by frequent fires. A high frequency of fire (less than 10-15 years apart) will result in the loss of obligate seeding shrub species such as ''Manzanita'' spp. This high frequency disallows seeder plants to reach their reproductive size before the next fire and the community shifts to a sprouter-dominance. If high frequency fires continue over time, obligate resprouting shrub species can also be eliminated by exhausting their energy reserves below-ground. Today, frequent accidental ignitions can convert chaparral from a native shrubland to non-native annual grassland and drastically reduce species diversity, especially under drought brought about by climate change.<ref>{{Cite journal|last1=Syphard|first1=Alexandra D.|last2=Radeloff|first2=Volker C.|last3=Keeley|first3=Jon E.|last4=Hawbaker|first4=Todd J.|last5=Clayton|first5=Murray K.|last6=Stewart|first6=Susan I.|last7=Hammer|first7=Roger B.|date=2007-07-01|title=Human Influence on California Fire Regimes|journal=Ecological Applications|language=en|volume=17|issue=5|pages=1388–1402|doi=10.1890/06-1128.1|pmid=17708216|bibcode=2007EcoAp..17.1388S |issn=1939-5582}}</ref><ref>{{Cite journal|last1=Pratt|first1=R. Brandon|last2=Jacobsen|first2=Anna L.|last3=Ramirez|first3=Aaron R.|last4=Helms|first4=Anjel M.|last5=Traugh|first5=Courtney A.|last6=Tobin|first6=Michael F.|last7=Heffner|first7=Marcus S.|last8=Davis|first8=Stephen D.|date=2014-03-01|title=Mortality of resprouting chaparral shrubs after a fire and during a record drought: physiological mechanisms and demographic consequences|journal=Global Change Biology|language=en|volume=20|issue=3|pages=893–907|doi=10.1111/gcb.12477|pmid=24375846|bibcode=2014GCBio..20..893P|s2cid=19688559 |issn=1365-2486}}</ref>

=== Invasive species effects on soil composition post and pre fire ===
Invasive species impact the chaparral ecosystem in many ways; they inhibit the re-establishment of native species, promote shorter term fire frequency, and change chemical composition of soils which ultimately impedes native species success. Annual Invasion on chaparral environments leads to lower levels of readily available Nitrogen (N) for native plants, affects the [[Carbon-to-nitrogen ratio|Carbon-to-Nitrogen]] ratio (C/N), develops shallow fine root systems, creates more litter and aboveground biomass and can increase soil respiration. Native plants rely on nitrogen to grow so when non natives invade they take this away hindering plant growth. High frequency fire due to invasive grasses increase the amount of Nitrogen lost due to volatilization, as nitrogen is lost more consistently native shrubs struggle due to lower then normal nitrogen levels.<ref>{{Cite journal |last=Debano |first=L. F. |last2=Conrad |first2=C. E. |date=May 1978 |title=The Effect of Fire on Nutrients in a Chaparral Ecosystem |url=http://doi.wiley.com/10.2307/1936579 |journal=Ecology |language=en |volume=59 |issue=3 |pages=489–497 |doi=10.2307/1936579}}</ref> Non-Native invasive such as grasses tend to have shallower root systems that outcompete natives such as [[Manzanita|M''anzanita'']]'', [[Adenostoma fasciculatum|Chamise]]'' and ''[[Ceanothus]]''. Since invasive grasses root systems are much shallower they reduce soil moisture at the top level of the soil, this greatly reduces the prosperity of re establishing native seedlings.<ref>{{Cite journal |last=Phillips |first=Michala L. |last2=Allen |first2=Edith B. |date=March 2024 |title=Invasive grass density negatively impacts chaparral seedling establishment |url=https://onlinelibrary.wiley.com/doi/10.1111/rec.14053 |journal=Restoration Ecology |language=en |volume=32 |issue=3 |doi=10.1111/rec.14053 |issn=1061-2971}}</ref> Increased plant litter and biomass aboveground crowd out natives and change desirable soil compositions.<ref>{{Cite journal |last=Zedler |first=Paul H. |last2=Gautier |first2=Clayton R. |last3=McMaster |first3=Gregory S. |date=August 1983 |title=Vegetation Change in Response to Extreme Events: The Effect of a Short Interval between Fires in California Chaparral and Coastal Scrub |url=https://esajournals.onlinelibrary.wiley.com/doi/10.2307/1937204 |journal=Ecology |language=en |volume=64 |issue=4 |pages=809–818 |doi=10.2307/1937204 |issn=0012-9658}}</ref>

[[Plant litter]] when decomposed brings vital nutrients such as Carbon into the below soil. Invasive grasses produce litter with less recalcitrant Carbon in turn resulting in less Carbon intrusion. Recalcitrant carbon is found in higher quantities and quality in native shrubs litter, recalcitrant carbon takes longer to break down and is resistant to decomposing so it can stay in the soil for centuries. Chaparral provides vital [[Carbon sink|carbon sinks]] for our environment, when invasive grasses move in after short frequency fires we see less carbon storage and more carbon set free into the atmosphere.<ref name=":1">{{Cite journal |last=Dickens |first=S. J. M. |last2=Allen |first2=E. B. |date=May 2014 |title=Exotic plant invasion alters chaparral ecosystem resistance and resilience pre- and post-wildfire |url=http://link.springer.com/10.1007/s10530-013-0566-0 |journal=Biological Invasions |language=en |volume=16 |issue=5 |pages=1119–1130 |doi=10.1007/s10530-013-0566-0 |issn=1387-3547}}</ref>

To combat these non-native invasions and potentially balance degraded soils, techniques such as weeding and seeding along with [[Hydroseeding|hydro seeding]] can prove effective. Weeding and re seeding native species takes away competition after disturbances and allows native species to increase density.<ref name=":1" /> Post fire Carbon and Nitrogen levels greatly decrease and hydro seeding can help bring these levels back to what they were pre fire.<ref>{{Cite journal |last=Vourlitis |first=George |last2=Steinecke |first2=Dylan |last3=Martinez |first3=Tanairi |last4=Konda |first4=Karen |last5=Rendon |first5=Roxana |last6=Hall |first6=Victoria |last7=Khor |first7=Sherryca |last8=Sethuraman |first8=Arun |date=March 2022 |title=Fire and post-fire management alters soil microbial abundance and activity: A case study in semi-arid shrubland soils |url=https://linkinghub.elsevier.com/retrieve/pii/S092913932100442X |journal=Applied Soil Ecology |language=en |volume=171 |pages=104319 |doi=10.1016/j.apsoil.2021.104319|doi-access=free }}</ref> Although hydro seeding can help balance these levels it is important to note that hydro seeding does open up the possibility of introducing invasive species and has potential long lasting effects on Carbon and Nitrogen cycles in chaparral ecosystems.

===Wildfire debate===
There are two older hypotheses relating to California chaparral fire regimes that caused considerable debate in the past within the fields of wildfire ecology and land management. Research over the past two decades have rejected these hypotheses:
# That older stands of chaparral become "[[senescent]]" or "[[decadent]]", thus implying that fire is necessary for the plants to remain healthy,<ref>{{Cite journal|last=Hanes|first=Ted L.|date=1971-02-01|title=Succession after Fire in the Chaparral of Southern California|journal=Ecological Monographs|language=en|volume=41|issue=1|pages=27–52|doi=10.2307/1942434|jstor=1942434|bibcode=1971EcoM...41...27H |issn=1557-7015}}</ref>
# That [[wildfire suppression]] policies have allowed dead chaparral to accumulate unnaturally, creating ample fuel for large fires.<ref name="Minnich 1983">{{Cite journal|last=Minnich|first=Richard A.|date=1983-03-18|title=Fire Mosaics in Southern California and Northern Baja California|url=https://www.science.org/doi/10.1126/science.219.4590.1287|journal=Science|language=en|volume=219|issue=4590|pages=1287–1294|doi=10.1126/science.219.4590.1287|issn=0036-8075|pmid=17735593|bibcode=1983Sci...219.1287M|s2cid=46485059}}</ref>

The perspective that older chaparral is unhealthy or unproductive may have originated during the 1940s when studies were conducted measuring the amount of forage available to deer populations in chaparral stands.<ref>{{Cite journal|last=Halsey|first=R.W.|title=Chaparral as a natural resource: changing the conversation about chaparral and fire|date=2009|journal=Proceedings of the CNPS Conservation Conference|pages=82–86|url=https://californiachaparral.org/__static/2cd475078290bea5c83ba143f73a1cba/cnps_proceedings_halsey_-82-_86.pdf?dl=1}}</ref> However, according to recent studies, California chaparral is extraordinarily resilient to very long periods without fire<ref name="Keeley 255–265">{{Cite journal|last1=Keeley|first1=Jon E.|last2=Pfaff|first2=Anne H.|last3=Safford|first3=Hugh D.|date=2005-10-03|title=Fire suppression impacts on postfire recovery of Sierra Nevada chaparral shrublands*|url=http://www.publish.csiro.au/wf/WF05049|journal=International Journal of Wildland Fire|language=en|volume=14|issue=3|pages=255–265|doi=10.1071/wf05049|issn=1448-5516}}</ref> and continues to maintain productive growth throughout pre-fire conditions.<ref>{{Cite book|title=Stand Age and Growth Dynamics in Chamise Chaparral|last=Hubbard|first=R.F.|publisher=Master’s thesis, San Diego State University|year=1986|location=San Diego}}</ref><ref>{{Cite journal |last1=Larigauderie |first1=A. |last2=Hubbard |first2=T.W. |last3=Kummerow |first3=J. |date=1990 |title=Growth dynamics of two chaparral shrub species with time after fire |journal=Madroño |volume=37 |issue=4 |pages=225–236 |jstor=41424817}}</ref> Seeds of many chaparral plants actually require 30 years or more worth of accumulated [[leaf litter]] before they will successfully germinate (e.g., scrub oak, ''[[Quercus berberidifolia]]''; toyon, ''[[Heteromeles arbutifolia]]''; and holly-leafed cherry, ''[[Prunus ilicifolia]]''). When intervals between fires drop below 10 to 15 years, many chaparral species are eliminated and the system is typically replaced by non-native, invasive, weedy grassland.<ref>{{Cite journal|last=Keeley|first=Jon E.|title=Future of California Floristics and Systematics: Wildfire Threats to the California Flora|date=1995|journal=Madroño|volume=42|issue=2|pages=175–179|jstor=41425064}}</ref><ref>{{Cite journal|last1=Haidinger|first1=Tori L.|last2=Keeley|first2=Jon E.|date=1993|title=Role of high fire frequency in destruction of mixed chaparral|url=http://www.californiachaparral.org/images/Haidinger_Role_of_High_fire_frequency.pdf |archive-url=https://web.archive.org/web/20160414152510/http://californiachaparral.org/images/Haidinger_Role_of_High_fire_frequency.pdf |archive-date=2016-04-14 |url-status=live|journal=Madroño|volume=40|pages=141–147}}</ref><ref>{{Cite journal|last=Zedler|first=P.H.|year=1995|editor-last=Keeley|editor-first=J.E.|editor2-last=Scott|editor2-first=T|title=Fire frequency in southern California shrublands: biological effects and management options|journal=Brushfires in California Wildlands: Ecology and Resource Management|publisher=International Association of Wildland Fire|location=Fairfield, WA|pages=101–112}}</ref>

The idea that older chaparral is responsible for causing large fires was originally proposed in the 1980s by comparing wildfires in [[Baja California]] and southern California. It was suggested that fire suppression activities in southern California allowed more fuel to accumulate, which in turn led to larger fires.<ref name="Minnich 1983"/> This is similar to the observation that fire suppression and other human-caused disturbances in dry, [[ponderosa pine]] forests in the Southwest of the United States has unnaturally increased forest density.<ref name="Swetnam 1999">{{Cite journal|last1=Swetnam|first1=T.W.|last2=Allen|first2=C.D.|last3=Betancourt|first3=J.L.|date=1999|title=Applied historical ecology: using the past to manage for the future|journal=Ecological Applications|language=en|volume=9|issue=4|pages=1189–1206|doi=10.1890/1051-0761(1999)009[1189:AHEUTP]2.0.CO;2|url=https://esajournals.onlinelibrary.wiley.com/doi/abs/10.1890/1051-0761%281999%29009%5B1189%3AAHEUTP%5D2.0.CO%3B2}}</ref> Historically, mixed-severity fires likely burned through these forests every decade or so,<ref name="Swetnam 1999"/> burning understory plants, small trees, and downed logs at low-severity, and patches of trees at high-severity.<ref>{{Cite book|last1=Hanson|first1=C.T|last2=Sherriff|first2=R.L|last3=Hutto|first3=R.L.|last4=DellaSala|first4=D.A.|last5=Veblen|first5=T.T.|last6=Baker|first6=W.L.|year=2015|editor-last=DellaSala|editor-first=D.A.|editor2-last=Hanson|editor2-first=C.T.|title=The Ecological Importance of Mixed-Severity Fires: Nature's Phoenix|publisher=Elsevier|location=Amsterdam, Netherlands|pages=3–22|isbn=978-0-12-802749-3 |url=https://www.elsevier.com/books/the-ecological-importance-of-mixed-severity-fires/dellasala/978-0-12-802749-3}}</ref> However, chaparral has a high-intensity crown-fire regime, meaning that fires consume nearly all the above ground growth whenever they burn, with a historical frequency of 30 to 150 years or more.<ref name="Halsey Conservation Issues"/> A detailed analysis of historical fire data concluded that fire suppression activities have been ineffective at excluding fire from southern California chaparral, unlike in ponderosa pine forests.<ref name="Keeley 255–265"/> In addition, the number of fires is increasing in step with population growth and exacerbated by climate change. Chaparral stand age does not have a significant correlation to its tendency to burn.<ref>{{Cite journal|last1=Moritz|first1=Max A.|last2=Keeley|first2=Jon E.|last3=Johnson|first3=Edward A.|last4=Schaffner|first4=Andrew A.|date=2004-03-01|title=Testing a basic assumption of shrubland fire management: how important is fuel age?|journal=Frontiers in Ecology and the Environment|language=en|volume=2|issue=2|pages=67–72|doi=10.1890/1540-9295(2004)002[0067:tabaos]2.0.co;2|issn=1540-9309}}</ref>

Large, infrequent, high-intensity wildfires are part of the natural fire regime for California chaparral.<ref>{{Cite journal|last1=Mensing|first1=S.A.|last2=Michaelsen|first2=J.|last3=Byrne|first3=R.|date=1999|title=A 560 year record of Santa Ana fires reconstructed from charcoal deposited in the Santa Barbara Basin, California|journal=Quaternary Research|volume=51|issue=3|pages=295–301|doi=10.1006/qres.1999.2035|bibcode=1999QuRes..51..295M|s2cid=55801393 |url=https://californiachaparral.org/__static/9512ac1d82af2bf86ac6e888cc7ed366/santa_ana_fires_-500-_years.pdf?dl=1}}</ref> Extreme weather conditions (low humidity, high temperature, high winds), drought, and low fuel moisture are the primary factors in determining how large a chaparral fire becomes.