1. North-South Variations in West Coast Hydrometeorological Parameters 21
As noted previously, hydrometeorological processes strongly influence
the structure and functioning of natural ecosystems. In most areas ,
biological systems are in a state of dynamic equilibrium with regional and
local climates, although in some cases, unusual hydroclimatic environments have maintained ecosystems that are remnants of earlier times
(e.g., high-altitude arid-region rainforests maintained by cloud water) .
When ecosystems are perturbed by human intervention or a natural
event, the response of the ecosystem will depend on its state (which, in
turn, is determined by abiotic factors such as the hydroclimatology) as
well as the natural biological buffers that exist in the ecosystem. One
approach that may assist in understanding the complex responses of
ecosystems involves the consideration of an ecosystem as a complex yet
geographically bounded system embedded in a larger, simpler abiotic
system with slower variations, such as land-use changes and water contamination. In turn, these variations are embedded in the global climate,
which is subject to interannual variability and change arising from
increasing concentrations of greenhouse gases. The following sections
summarize some of the linkages that exist between the bulk characteristics
of these ecosystems and the larger-scale hydroclimatic factors that affect
the development of these ecosystems.
Hydroclimatology and Biodiversity
An important aspect of an ecosystem is its biodiversity. Terborgh (1992)
suggested that biodiversity is inversely proportional to the latitudinal
temperature gradient and increases near the equator because the latitudinal temperature gradient is less there than it is at more polar latitudes.
He indicated that the width of the zone over which the temperature is
uniform, or nearly uniform , is a good indicator of the potential for
allopatric speciation or biodiversity. According to his analysis, the most
uniform temperature gradients exist near the equator and decrease north
of 20°N and south of 20°S.
Temperature gradients were analyzed for the study area by computing
the value of /1T//1Y (where /1T is the temperature change over a latitude
band of width /1Y) and then inverting this number to get the value of
/1Y//1T (the width of a latitude band over which a 1°C temperature
change takes place). Since the values of temperature along the northsouth transect undergo considerable variability, the temperature differences were averaged by a double pass of a 5-point triangular filter. The
filter smoothed data according to the following relationship:
(1.3)
where To = temperature at the latitude under consideration
T-1 = temperature 1° South
As noted previously, hydrometeorological processes strongly influence
the structure and functioning of natural ecosystems. In most areas ,
biological systems are in a state of dynamic equilibrium with regional and
local climates, although in some cases, unusual hydroclimatic environments have maintained ecosystems that are remnants of earlier times
(e.g., high-altitude arid-region rainforests maintained by cloud water) .
When ecosystems are perturbed by human intervention or a natural
event, the response of the ecosystem will depend on its state (which, in
turn, is determined by abiotic factors such as the hydroclimatology) as
well as the natural biological buffers that exist in the ecosystem. One
approach that may assist in understanding the complex responses of
ecosystems involves the consideration of an ecosystem as a complex yet
geographically bounded system embedded in a larger, simpler abiotic
system with slower variations, such as land-use changes and water contamination. In turn, these variations are embedded in the global climate,
which is subject to interannual variability and change arising from
increasing concentrations of greenhouse gases. The following sections
summarize some of the linkages that exist between the bulk characteristics
of these ecosystems and the larger-scale hydroclimatic factors that affect
the development of these ecosystems.
Hydroclimatology and Biodiversity
An important aspect of an ecosystem is its biodiversity. Terborgh (1992)
suggested that biodiversity is inversely proportional to the latitudinal
temperature gradient and increases near the equator because the latitudinal temperature gradient is less there than it is at more polar latitudes.
He indicated that the width of the zone over which the temperature is
uniform, or nearly uniform , is a good indicator of the potential for
allopatric speciation or biodiversity. According to his analysis, the most
uniform temperature gradients exist near the equator and decrease north
of 20°N and south of 20°S.
Temperature gradients were analyzed for the study area by computing
the value of /1T//1Y (where /1T is the temperature change over a latitude
band of width /1Y) and then inverting this number to get the value of
/1Y//1T (the width of a latitude band over which a 1°C temperature
change takes place). Since the values of temperature along the northsouth transect undergo considerable variability, the temperature differences were averaged by a double pass of a 5-point triangular filter. The
filter smoothed data according to the following relationship:
(1.3)
where To = temperature at the latitude under consideration
T-1 = temperature 1° South