Causes and feedbacks to widespread grass invasion into chaparral shrub dominated landscapes
This study provides a unified, holistic framework for predicting the dynamics of shrub-grass conversion throughout Mediterranean-climate shrublands. This work focuses specifically on the California chaparral, which until recently has been considered resistant to invasion by exotic grasses, but in recent years appears to have undergone substantial type conversion.
To synthesize current understanding of the feedbacks and anthropogenic impacts that both enhance and reduce the susceptibility of southern California chaparral to invasion and its corresponding ability to recolonize invaded areas.
We review the existing literature pertaining to the factors that enhance or reduce the susceptibility of chaparral to invasion, and organize these factors and their interactions into a single unified framework of environmental drivers, ecological interactions, and historical legacies associated with the distribution and rate of such invasion.
A myriad of processes interact to mediate the invasion of exotic grasses into intact chaparral. In addition, we demonstrate that feedbacks exist within both chaparral shrublands and exotic grasslands that modify the landscape in ways that can enhance their own survival, act as barriers to conversion into alternate cover types, and in some cases weaken the resistance of adjacent vegetation to invasion. We posit a methodological framework from which the many climatic, anthropogenic, edaphic, and biotic feedbacks that determine the mosaic of invasion can be modeled.
This study demonstrates that substantial conversion of chaparral into deciduous grasslands has recently occurred in southern California and presents a unified framework for forecasting the dynamics of shrub-grass conversion throughout Mediterranean-climate shrublands.
KeywordsChaparral Invasion Ecological forecasting Alternate stable states Landscape restoration
This research was funded through a cooperative agreement between UC-Riverside and the US Forest service (Grant No. 11-CS-11050100-031) and the National Science Foundation (DEB—1656062).
- Allen EB (1999) Restoring habitats to prevent exotics. In: Proceedings of the California exotic pest plant council symposium, pp 41–44Google Scholar
- Allen EB, Padgett PE, Bytnerowicz A, Minnich R (1998) Nitrogen deposition effects on coastal sage vegetation of southern California. In: Proceedings of the international symposium on air pollution and climate change effects on forest ecosystems, Pacific Southwest Research Station, Riverside, California, USA. US Department of Agriculture Forest Service, pp 131–140Google Scholar
- Allen EB, Williams K, Beyers JL, Phillips M, Ma S, D’Antonio CM (2018) Chaparral Restoration. In: Underwood EC, Safford HD, Molinari NA, Keeley JE (eds) Valuing chaparral: ecological, socio-economic, and management perspectives. Springer, BerlinGoogle Scholar
- Bentley JR (1967) Conversion of Chaparral areas to grassland: techniques used in California vol Agriculture Handbook No. 328. Forest Service, USDA, Berkeley, CAGoogle Scholar
- Borchert MI, Odion DC (1995) Fire intensity and vegetation recovery in chaparral: a review. In: Keeley JE, Scott T (eds) Brushfires in California wildlands: ecology and resource management. International Association of Wildland Fire, FairfieldGoogle Scholar
- Bradshaw LS, Deeming JE, Burgan RE, Cohen JD (1983) The 1978 national fire-danger rating systemL technical documentation. United Stated Department of Agriculture, Forest Service, Intermountain Forest and Range Experiment Station, OgdenGoogle Scholar
- Christensen NL (1985) Shrubland fire regime and their evolutionary consequences. In: Pickett STA (ed) The ecology of natural disturbance and patch dynamics. Academic Press Inc, Orlando, pp 85–99Google Scholar
- Conard SG, Weise DR (1998) Management of fire regime, fuels and fire effects in southern California chaparral: lessons from the past and thoughts for the future vol 20. Fire in ecosystem management: shiftng the paradigm from suppression to prescription. Tall Timbers Fire Ecology Conference Proceedings. Tall Timber Research Station, Tallahassee, Florida, USAGoogle Scholar
- Corbett ES, Crouse RP (1968) Rainfall interception by annual grass and chaparral… losses compared (U.S. Forest Serv. Res. Paper PSW-48). USDA Forest Service, Pacific Southwest Forest and Range Experiment Station, Berkeley, CaliforniaGoogle Scholar
- Cornwell WK, Cornelissen JHC, Amatangelo K, Dorrepaal E, Eviner VT, Godoy O, Hobbie SE, Hoorens B, Kurokawa H, Pérez-Harguindeguy N, Quested HM, Santiago LS, Wardle DA, Wright IJ, Aerts R, Allison SD, Van Bodegom P, Brovkin V, Chatain A, Callaghan TV, Díaz S, Garnier E, Gurvich DE, Kazakou E, Klein JA, Read J, Reich PB, Soudzilovskaia NA, Vaieretti MV, Westoby M (2008) Plant species traits are the predominant control on litter decomposition rates within biomes worldwide. Ecol Lett 11:1065–1071CrossRefGoogle Scholar
- Figueroa JA, Castro SA, Marquet PA, Jaksic FM (2004) Exotic plant invasions to the mediterranean region of Chile: causes, history and impacts. Rev Chil Hist Nat 77:465–483Google Scholar
- Green LR (1977) Fuelbreaks and other fuel modification for wildland fire control. In: Agriculture handbook vol 499. USDA Forest Service, Washington DCGoogle Scholar
- Haidinger TL, Keeley JE (1993) Role of high fire frequency in destruction of mixed chaparral. Madroño 40:141–147Google Scholar
- Hedrick DW (1951) Studies on the succession and manipulation of chamise brushlands in California. Texas A&M University, TexasGoogle Scholar
- Homyak PM (2012) Nitrogen and phosphorus biogeochemistry of watersheds along the western slope of the Sierra Nevada. UC RiversideGoogle Scholar
- Johnson WH, Fitzhugh EL (1990) Grazing helps maintain brush growth on cleared land California. Agriculture 44:31–35Google Scholar
- Keeley JE (2000) Chaparral. In: Barbour M, Billings W (eds) North American terrestrial vegetation. Cambridge University Press, New YorkGoogle Scholar
- Keeley JE (2001) Fire and invasive species in Mediterranean-climate ecosystems of California. In: Galley KEM, Wilson TP (eds) Proceedings of the invasive species workshop: the role of fire in the control and spread of invasive species. Timbers Research Station, Tallahassee, pp 81–94Google Scholar
- Keeley JE (2004) Invasive plants and fire management in California Mediterranean-climate ecosystems. In: Proceedings 10th MEDECOS ConferenceGoogle Scholar
- Keeley JE, Keeley SC (1987) Role of fire in the germnation of chaparral herbs and suffrutescents. Madroño 34:240–249Google Scholar
- Keeley JE, Syphard AD (2018) South Coast Bioregion. In: Wagtendonk JW, Sugihara NG, Stephens SL, Thode AE, Shaffer KE, Fites-Kaufman JA (eds) Fire in California’s ecosystems, 2nd edn. University of California Press, Berkeley, CaliforniaGoogle Scholar
- Murphy AH, Leonard OA (1974) Chaparral shrub control as influenced by grazing, herbicides and fire California. Agriculture 28:10–13Google Scholar
- Oechel WC (1988) Seedling establishment and water relations after fire in a Mediterranean ecosystem. In: Allen EB (ed) The reconstruction of disturbed arid lands. Westview Press, Boulder, pp 34–45Google Scholar
- Orme AR, Bailey RG (1970) The effect of vegetation conversion and flood discharge on stream channel geometry: a case of southern California watersheds. Proc Am Assoc Geogr 2:101–106Google Scholar
- Parker VT (1987) Effects of wet-season management burns on chaparral vegetation: implications for rare species. In: Elias TE (ed) Proceedings of a conference on the conservation and management of rare and endangered plants, Sacramento. California Native Plant Society, California, pp 233–237Google Scholar
- Rowe PB (1963) Streamflow increases after removing woodland-riparian vegetation from a southern california watershed. J For 61:365–370Google Scholar
- Rundel PW (1983) Impact of fire on nutrient cycle. In: Kruger FJ, Mitchell DT, Jarvis JUM (eds) Mediterranean type ecosystems, vol 192–207. Springer, BerlinGoogle Scholar
- Van de Water K, Safford HD (2011) A summary of fire frequency estimates for California vegetation before Euro-American settlement fire. Ecology 7:26–58Google Scholar
- Zammit CA, Zedler PH (1988) The influence of dominant shrubs, fire, and time since fire on soil seed banks in mixed chaparral. Vegetatio 75:175–187Google Scholar