The February edition of ESA's Ecological Monographs features major research papers regarding a wide range of ecological topics. A sampling of these topics is listed below.
Desert Shrubs and the Formation of Resource Islands
Desert ecosystems are some of the most uninhabitable places in the world. The
plants and animals of deserts display extraordinary evolutionary adaptations
designed to withstand or even circumvent the driest of seasons. James Reynolds,
a plant ecologist from Duke University, and Ross Virginia, a soil ecologist from
Dartmouth College, headed a team of researches located in the Jornada Basin of
southern New Mexico to explore and understand the survival strategies of two
successful shrub species in the semiarid grasslands of the southwestern United
States and how changes in the amount and seasonality of rainfall may affect
these plants in the future.
A three-year field study has shown that when desert shrubs establish themselves in suitable places on the desert floor, a microclimate below the shrub canopy is created. These tiny reserves are the homes for many soil microorganisms that are essential in maintaining soil health. Scientists have observed that the areas outside of these shrubs are more exposed to wind and rain which make these places unsuitable for plant life. Consequently, each individual shrub site contains the necessary elements for survival which scientists call "resource islands." These islands are preferred sites for the regeneration of shrubs and other herbaceous plants that would otherwise die without them. The coexistence between plants and soil organisms within this unique system has made it possible for life to flourish even within the harshest of environments.
The Effects of Flooding on Black Ash Trees
Experts are just beginning to understand the ecological implications of global
warming. Scientists conclude that natural disturbances in forests (fires,
insect outbreaks, windstorms, etc.) are affected by Earth's global climate
change. Consequently, researchers are interested in recognizing the effects of
this phenomenon on forest ecology and specifically how certain species are
adapted to this change. A study conducted by ecologists Jacques Tardif and Yves
Bergeron in Quebec's southwestern boreal forests focused on the ecological
implications of flood disturbances on populations of black ash (Fraxinus
nigra).
Study plots were designated around Lake Duparquet in Quebec to witness the effects of flooding on black ash populations surrounding the lake. Both natural and gradual fluctuations in spring flood levels have enabled black ash populations to adapt to their changing environment. Researchers observed that population stability was due to the strategically different reproduction methods between trees located within the floodplain and trees located in higher elevations. Near the lake, trees relied mainly on vegetative sprouting while less exposed trees away from the lake relied mainly on seed dispersion and germination. Researchers conclude that it is this unique adaptation of black ash to rely on two types of reproduction that characterizes its resilience to flooding disturbance. This reliance may be the trees' natural insurance against the increasing levels of stress influenced by global climate change. But researchers warn that this insurance may only be effective in large stands; smaller groups of trees may not contain the same characteristics and may be more vulnerable to floods.
Exotic Plant Species Invade Hot Spots of Native Plant Diversity
Researchers in Colorado have conducted long term studies on the patterns of
exotic plant invasions that have recently challenged some of ecology's existing
paradigms. It has been widely hypothesized that diversity begets stability.
Areas of low diversity were thought to be less complex systems, while highly
diverse areas were considered more complex and thus more efficient in using
available resources. However, field scientists observed that areas of high plant
diversity may be invaded just as easily as areas of low diversity. Study sites
were based in the Colorado Rockies, the Central Grasslands in Colorado, Wyoming,
South Dakota, and Minnesota and included nine different vegetation types in both
areas. This pattern was said to have been based on a complexity of issues,
including plant cover, soil nitrogen availability, and total number of exotic
species. Patterns of invasion, more importantly, depend on scale, ecosystem,
vegetation type, availability of resources and responses to disturbance. Ecologists are always faced with new theories due to the
complexity of natural ecosystems. When new theories arise, old ones are
challenged. "It is humbling to note that community ecologists do not yet
understand the causes and patterns of native species richness," says the head
ecologist of the study, Thomas J. Stohlgren.
Ecological Monographs is a journal published four times a year by the Ecological Society of America (ESA). Copies of the above articles are available free of charge to the press through the Society's Public Affairs Office. Members of the press may also obtain copies of ESA's entire family of publications, which includes Ecology, Ecological Applications, Ecological Monographs, and Conservation Ecology. Others interested in copies of articles should contact the Reprint Department at the Ecological Society of America, 2010 Massachusetts Avenue, NW, Suite 400, Washington, DC 20036.
Founded in 1915, the Ecological Society of America (ESA) is a scientific, non-profit, organization with over 7000 members. Through ESA reports, journals, membership research, and expert testimony to Congress, ESA seeks to promote the responsible application of ecological data and principles to the solution of environmental problems. For more information about the Society and its activities, access ESA's web site at: http://esa.sdsc.edu.
Journal
Ecological Monographs