Chaparral

From Academic Kids

This article is about the biome. For other uses, see Chaparral (disambiguation)

Chaparral is a biome found primarily in California, USA, that is shaped by a Mediterranean climate (mild, wet winters and hot dry summers) and wildfire. Similar plant communities are found in 5 other regions areas including the Mediterranean (where it is known as maquis), coastal central Chile, South African Cape Region (known there as fynbos), and Australia (Western and Southern).

The word chaparral comes from the Spanish word chaparro, or dwarf evergreen oak, which itself comes from the Basque word txapar, with the same meaning.

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Chaparral.jpg
Chaparral, Santa Ynez Mountains, near Santa Barbara, California

A typical chaparral plant community consists of densely-growing evergreen oaks and other drought-resistant shrubs. It often grows so densely that it is all but impenetrable to large animals and humans. This, and its generally arid condition, makes it notoriously prone to wildfires. Although many chaparral plant species require some fire cue (heat, smoke, or charred wood) for germination, chaparral plants are not "adapted" to fire per se. Rather, these species are adapted to particular fire regimes involving season, frequency, intensity and severity of the burn.

There are two misconceptions relating to California chaparral. 1) Chaparral needs to burn to remain healthy, and 2) fire suppression policies have allowed chaparral to accumulate unnatural levels of fuel. California chaparral is extraordinarily resilient to very long periods without fire. Old-growth chaparral in excess of one hundred years old remains a productive, dynamic ecosystem. There is no scientific evidence to support the notion that native shrublands have become unhealthy due to overgrowth. In fact, seeds of many chaparral plants actually require 30 years or more worth of accumulated leaf litter before they will successfully germinate. When intervals between fires drop below 10 to 15 years, many chaparral species are eliminated and the system is typically replaced by non-native, weedy grassland.

The idea that older chaparral is responsible for causing large fires is related to one of the most repeated misconceptions regarding the system: past fire suppression efforts have allowed an “unnatural” accumulation of brush to develop within the chaparral, leading to huge, catastrophic wildfires. This belief appears to be based on the misapplication of studies relating to dry ponderosa pine forests showing that undergrowth has increased over the past century due to successful fire fighting activities. In the past, surface fires burned through these forests at intervals anywhere between 4 to 36 years, clearing out the understory and creating a more ecologically balanced system. However, this conclusion has nothing to do with California shrublands.

Detailed analysis of historical fire data has shown that not only have fire suppression activities failed to exclude fire from southern California chaparral as they have in ponderosa pine forests, but the number of fires is actually increasing in step with population growth. Research showing differences in fire size and frequency between southern California and Baja has been used to imply larger fires north of the border are the result of fire suppression, but this opinion has been seriously challenged by numerous investigators and is no longer supported by the majority of fire ecologists.

Whenever chaparral burns, everything goes, no matter the age. This is characteristic of a crown fire regime as opposed to the surface fire type found in ponderosa forests. A young, 5-year-old stand of chaparral has already produced more than enough material to fuel and carry a catastrophic wildfire across the landscape. Overall, how old a recovered chaparral stand happens to be has very little to do with its chances of burning.

There is no question chaparral is extremely flammable, especially during dry weather conditions. As stands grow older, they continue to build up fuel in the form of both dead and living plant material. This is a natural process and part of the normal chaparral life cycle. However, not all chaparral stands are alike and the amount of fuel accumulation varies with the type. For example, a hillside of ceanothus chaparral has the capacity of accumulating more potential biomass in less than 20 years than an expanse of chamise chaparral does in 60 years. In addition, chaparral on north facing slopes may have more biomass accumulation in 10 years than drier, south-facing slopes do at 80 years.

The ratio of dead to living material in a chaparral stand is equally complex, with amounts accumulated being determined by multiple environmental factors including prior fire history, direction of slope, and severity of drought periods. Extensive studies by numerous investigators have found 30% dead to living ratios across a range of 20 to 60 year old stands without any significant relationship to age. So automatically assuming an older stand of chaparral is filled with dead fuel ready to burn is not supported by actual field research.

In Southern California chaparral forms a dominant habitat. Members of the chaparral biota native to California, all of which tend to regrow quickly after fires, include:

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