Ecological Systems, Introduction - Ecological Systems - page 4

patterns, in order to use effectively the energy available. This entry demonstrates
the need for flow analysis, provides a brief example using a well-studied ecosystem,
and discusses some of the ecosystem development tendencies which can be

addressed using ecosystem flow analysis.

Ecotones and Ecological Gradients - Ecotones are areas of steep transition between
ecological communities, ecosystems, or ecological regions (such as Mediterranean
and desert). Ecotones often occur along ecological gradients. Such gradients are
created as a result of spatial shifts in elevation, climate, soil, and many other
environmental factors. Ecotones commonly coincide with areas of sharp climatic
transition along environmental gradients. They occur at multiple spatial scales,
from continental-scale transitions between major biomes to small-scale ecotones
where local vegetation communities and microhabitats coincide. They show
a diversity of boundary types that range from natural boundaries (e.g., altitudinal,
latitudinal transitions) to human-generated ecotones (e.g., forest clear-cut edges or
urban ecotones). Ecotones have been studied in the past four decades in an
ecological context and in recent years are receiving increasing attention in the
context of biodiversity conservation. Various studies have shown that species
richness and abundances tend to peak in ecotonal areas, though exceptions to
these patterns occur. Ecotones are “natural laboratories” for studying a range of
evolutionary processes, such as the process by which new species form, also termed
speciation. Recent evidence suggests that ecotones may serve as speciation centers.
Some researchers argue that ecotones deserve high conservation investment, poten-
tially serving as speciation and biodiversity centers. Because ecotones are often
small in size and relatively rich in biodiversity, conservation efforts in these areas
may prove to be an efficient and cost-effective conservation strategy.

Invasive Species - This entry describes the causes and consequences of biological
invasions, by synthesizing concepts from population biology, community ecology,
evolution, biogeography, and conservation biology. First, the patterns and process
of invasion are explored; then, some of its potential ecological and socioeconomic
impacts are examined. Some major hypotheses and theoretical concepts explaining
patterns of colonization and impact are presented. Next, management approaches to
assessing, preventing, and mitigating this problem are considered. The entry ends
with a brief glimpse at some of the emerging issues that will likely be the foci of
future research.

Landscape Ecology - Landscapes are spatially heterogeneous areas characterized
by diverse patches that differ in size, shape, contents, and history. When spatial
heterogeneity is considered, scale matters and hierarchy emerges. Landscape ecol-
ogy is the science and art of studying and improving the relationship between
spatial pattern and ecological processes on a multitude of scales and organizational
levels. In a broad sense, landscape ecology represents both a field of study and
a scientific paradigm. As a highly interdisciplinary and transdisciplinary enterprise,
landscape ecology integrates biophysical and analytical approaches with humanis-
tic and holistic perspectives across natural and social sciences. Landscape ecology