National Park Service

Northeast Temperate Network (NETN)

atmospheric deposition and stress


A forest has many layers of plant life. There are the small plants such as shrubs, moss, ferns, and lichens which grow quietly beneath the shadows of tall trees. The trees found in a temperate forests are dominated by hardwoods (deciduous). Deciduous trees drop their leaves in the fall. Their trunks are also made of a bark that is very hard. Most of the trees are maple, birch, beech, oak, hickory, and sweet gum, along with a mix of other species of trees, including pine trees and other conifers. The Taiga is usually found north of the temperate forests, but sometimes they overlap.

Importance & Issues

jefferson salamander Vegetation structure and composition are highly relevant and applicable to ecosystem condition. Knowing the relative abundance, species composition and condition of the plant community provides an integrated measure of vegetation response to stress, in addition to basic information about habitat quality for a variety of other species. Moreover, this information will allow proper interpretation of many other vital signs. Monitoring the vegetation community is also a good early detection strategy for management of invasive species. Monitoring flora is relatively low cost, sampling is efficient, and changes in plant species composition and abundance can be accurately measured. Within forests, monitoring vegetation demography in the form of tree seedling and sapling regeneration provides an anticipatory indicator of future forest cover type as well as an integrative measure of the impacts of multiple stressors acting upon vegetation. Monitoring canopy and understory tree mortality provides another key integrative measure of multiple stressor impacts. Stand structure or age class is indicative of both successional stage and habitat quality, and is a particularly useful measure in forest systems subject to silviculture. Legacy features, such as large trees, snags and coarse woody debris provide important habitat for birds, mammals, and herptiles, as well as decomposers, bryophytes and tree seedlings. These legacy features can be useful indicators of wildlife habitat within early- and mid-successional forests and those subject to silviculture. In addition, canopy vegetation condition is an integrative, anticipatory indicator of stress and change within canopy vegetation, which can in turn lead to changes in ecosystem function, habitat quality and stand composition. At the stand scale, canopy condition can be assessed visually onsite as the crown condition of each canopy tree in a plot.

Our overall goal is to monitor status and trends in the structure, function and condition of NETN forested ecosystems in order to inform management decisions affecting those systems. To do so, NETN will interpret and report the ecological integrity of NETN forested systems from monitoring data. The “ecological integrity” of an ecosystem is a measure of the structure, composition, and function of an ecosystem as compared to pristine or benchmark ecosystems operating within the bounds of natural or historic disturbance regimes (Karr and Dudley 1981, DeLeo and Levin 1997, Czech 2004). Ecological integrity can be assessed by comparing key elements or attributes of an ecosystem to a reference area or to historical measurements or modeling efforts. In this way, NETN hopes to provide reliable data to inform management decisions relevant to NETN forested systems, including NPS land management and forest harvest plans, exotic species control, deer population management, NPS internal development, and national pollution control legislation

Monitoring Objectives

Stand structural class: Determine status and trends in the distribution of structural classes across park, and compare to that expected under natural disturbance regimes.

Snag abundance: Estimate status and trends in snag abundance and size class distribution.

Coarse Woody Debris (CWD): Determine status and trends in coarse woody debris volume.

Canopy closure: Determine status and trends in canopy closure in mature stands. Examine correlation between canopy closure and climatic stress, storms, pest and pathogen outbreaks and other disturbances. To be developed.

Photopoint: Provide visual reference of plots for long-term comparison.

Tree condition: Qualitatively assess condition of trees by species.

Tree growth and mortality rates: Determine growth and mortality rates of canopy tree species. Examine correlation between these rates and air pollution, pest or pathogen outbreaks, climatic stress or other known stressors.

Tree regeneration: Determine status and trends in quantity and composition of tree seedling establishment in forest understory.

Understory diversity: Determine status and trends in exotic plant species cover. Determine change in cover or extent of species indicative of deer browse pressure and other stress.

Forest floor condition: Qualitatively assess forest floor condition and estimate trends in spatial extent of earthworms and trampling impacts.

Landscape context: Determine status and trends in forest patch size, and proportion of surrounding area in natural cover and in anthropogenic landuse.


The Forest Protocol includes the following potential measures: stand structural class, snag abundance, coarse woody debris (CWD), canopy closure, photopoint, tree condition, tree growth and mortality rates, tree regeneration, understory diversity, forest floor condition, landscape context.


Last Updated: December 30, 2016 Contact Webmaster