Table of Contents
Abstract
Fire outbreaks in the CA chaparral have been a natural occurrence for many years at intervals of between 30-150 years. However, recently the fire outbreaks have become frequent at intervals of below 10-15 years. This has increased the use of fire suppression aimed at stopping the fire and protecting human lives and property close to the chaparral. This has however been questioned by fire ecologists who are of the view that fire is significant for the continuity of the chaparral species, and could, therefore, lead to changes in the diversity of plant species. Fire suppression tactics such as the use of fuel breaks have led to the introduction of invasive plant species while other tactics such as the use of fire retardants lead to change in soil composition hence affecting plant species. As this paper finds out, fire suppression in the chaparral and its effects on plant species diversity is a controversial issue which has caused a division in ecological views. The paper looks into the importance of fire to the ecosystem in the CA chaparral to understand how fire suppression affects the plant species diversity.
The California Chaparral is an eco-region that is found in the coast of the state of California in the United States and extends into the Northwestern Baja California in Mexico. The vegetation is characterized by broad-leaved evergreen woody shrubs and heath plants which become highly flammable during late summer and autumn months. The Chaparral is shaped by the Mediterranean climate which is characterized by rainy winters and hot, dry summers. The various characteristics of the Chaparral provide conditions that make it prone to wildfires that are infrequent, large, and of high intensity. Combating such fire requires various wildfire suppression tactics.
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Fire suppression in the California chaparral is usually a combined effort by both firemen on the ground and aerial firefighting aircraft specially designed for this cause. Fire has been occurring in the CA chaparral for so many years which has always been followed by a regeneration of species. This has led to many ecologists arguing that fire in the CA chaparral is indeed a natural occurrence that is necessary for the continuity of species (Lauvaux, Skinner, & Taylor, 2016). However, growing human settlements near this eco-region and occurrence of frequent fires have necessitated fire suppression to protect property and save lives. Despite this justification, the question on many ecologists’ minds is: what are the effects of altering a natural process in an ecosystem? In other words, how has fire suppression in the California chaparral affected the plant species diversity?
Importance of Fire to Plant Species
When it comes to fire-adapted ecosystems such as the CA chaparral, fire plays a major role in diversity maintenance, nutrient cycling, and habitat structure. Fire has also been found to be an important tool in restorative ecology, a field in ecology that deals with the restoration of destroyed, degraded or damaged ecosystems and habitats in the environment (Steel, Safford, & Viers, 2015). Fire ecology also maintains that there are many plant species which rely upon fire for their germination and reproduction. High-severity wildfire creates snag forest habitats which have been observed to contain higher species diversity and richness than unburned old forest. This is because the plant and animal species in vegetation such as the Chaparral have evolved with fire hence they depend on high-severity fires to reproduce and grow. Fire is important for the return of nutrients from plant matter back to the soil. The heat from the fire also favors the germination of certain types of seeds.
Fire Suppression
As mentioned, ecosystems in the Chaparral have evolved with fire. Plant species in this environment require fire to germinate and reproduce. Therefore wildfire suppression eliminates these species (Halsey & Syphard, 2015). Fire retardants work by coating fuels and lessening oxygen availability for the fire. They contain nitrates, phosphates, ammonia, sulfates, and a range of other chemicals and other thickening agents. Although the nitrogen and phosphorus components have been found to have a fertilizing effect (Zedler, Gautier, & McMaster, 1983), the use of these retardants has the potential to alter the soil chemistry. They increase soil acidity which can reduce the availability of plant nutrients in the soil. Recently, more suppression tactics have been included such as fuel treatment or fuel break (Zedler et al., 1983). This involves clearing the chaparral to break the spread of future fire. This can, however, lead to the growth of weed in the cleared areas.
Plant Species in the Chaparral
The Chaparral before a major fire is dominated by manzanita, greasewood (Adenostoma fasciculatum), Ceanothus species, toyon (Heteromeles arbutifolia), scrub oaks (Quercus berberidifolia), and sclerophyllous. These species usually sprout from underground burls after a fire (D’Antonio & Vitousek, 1992). Many of these species require a fire cue for germination. This cue could either be smoke, heat, charred wood, or chemical changes in the soil following a fire. Species such as Phacelia, known as fire followers, require fire to clear vegetation for sunlight to reach them. After a fire, these species grow and release their seeds which remain dormant until the next fire which will create conditions for growth. A cycle is thus created forming a relationship between fire and the CA chaparral. These infrequent fires ensure that the diversity of plant species in the Chaparral is maintained. Fire suppression promotes fire-intolerant invasive species in the chaparral by applying fuel treatment methods (Brooks et al., 2004).
Controversy Surrounding the CA Chaparral fires
Wildfires in the CA chaparral have been surrounded by a lot controversy that has led to divided views within the field of ecology (Minnich, 1989). One of the views is that fire is necessary for the plant species to remain healthy. There is also the view that fire suppression has led to the accumulation of dead chaparral acts as fuel resulting in larger fires. Studies conducted have shown that the chaparral can stay for long periods without fire and continue to maintain productive growth. The optimum period between fires has been estimated to be about 30 years or more (D’Antonio & Vitousek, 1992). Given that fires in the chaparral now occur in intervals of 10-15 years, some ecologists argue this could eliminate many of the plant species in the chaparral. Species such as the Caenothus Oliganthus and Xylococcus bicolor were almost eliminated in successive fires in 1979 and 1980 (Brooks et al., 2004).
Conclusion
Fire suppression has indeed changed plant species diversity in the CA chaparral. Tactics such as fuel breaks have led to the introduction of invasive plant species which are fire-intolerant which has led to frequent fires in the chaparral. Constant fire is a threat to the chaparral plant species. This has led to more fire suppression using chemicals such as fire retardants which alter soil composition hence causing changes to the plant species. More research, however, needs to be done to assess factors such as the full effects of invasive plant species on the chaparral. The true reason for the frequent fires in the chaparral that have been observed of late also needs to be found. Finally, more research needs to be done on the effects of the best methods for fire suppression in the CA chaparral.
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