Population Dynamics

What is it? A population is a group of organisms of the same species. Population dynamics refers to the changes in a plant or animal species population size over time due to natural or human causes.

Plant populations can be determined by measuring the area covered by plants of that species. Researchers compare ‘before’ and ‘after’ photographs to study changes in vegetation. Others walk along permanent, marked paths called "transects” year after year to record the plant types that are present.

Satellite imagery can be used for this estimation.To create "satellite images" like this, reflectance data are interpreted into classes such as vegetation or land-use types. Compared over time, these images can show landscape-scale changes in plant populations.

Continued study year after year is required to understand whether population size is increasing, decreasing, or stable.

Population Dynmics Research in LTER

Studying Population Dynamics - Animals

The Palmer Station LTER Site near the tip of the Antarctic Peninsula.

At the Palmer LTER LTER site on the Antarctic Peninsula, scientists are looking closely at the the penguin populations. As the climate and extent of sea ice changes in the area, population size of the different penguin species changes dramatically. During the last twenty years, climate warming at the Antarctic Peninsula has caused species that depend on open water such as Chinstrap (Pygoscelis antarctica) and Gentoo (Pygoscelis papua) penguins to become more abundant, while the population size of ice-dependent Adelie penguins (Pygoscelis adeliae) has declined.

Adelie penguins (Pygoscelis adeliae) make their home on the Antarctic Penninsula.
This graph illustrates the correlation between the number of breeding pairs of penguins over time. Note that the ice coverage in the study area has decreased during the period of time represented in this graph.

Studying Population Dynamics - Plants

The Jornada Basin LTER Site in the Chihuahuan Desert of southern New Mexico.

Over the past one hundred years or so, a combination of drought, grazing, and human disturbance has resulted in desertification in the southwest U.S. and northern Mexico. At the Jornada LTER in southern New Mexico, scientists study the change in regional plant populations. Dominant plant cover has changed from extensive perennial grasses to sparse shrubs with bare ground in between. Long-term studies contribute to unique perspectives into this process, which allow LTER scientists to actively participate in rangeland management.

Local students learn how to study plant population dynamics at the Jornada Basin LTER site.