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Forest ecology
Introduction
Forest ecology is a part of ecology that is concerned with forests as opposed to grasslands, savannas, or tundra. Ecology is the study of the processes
of interaction among organisms and between organisms and their environment. Ecology is often subdivided into physiological ecology, population ecology,
community ecology, and ecosystem ecology. Forest
ecology has generally focused on forest trees so it
could provide the ecological basis for silviculture,
forest management, and forest economics. Forestry
has always had an interest in the ecology of trees but
in the first half of the last century, forest ecology
was mostly included within silviculture [1]. Silviculture originally used an agricultural model, viewing forest trees as a perennial crop. Starting in the
1960s, forestry began to consider forests not just
as stands of trees but as ecosystems (see Ecosystem) and to be interested in the many other services
that ecosystems supply [2]. In the past decades, forest ecology increasingly became forest ecosystem
ecology.
Forest ecology has profited from interaction
with several other disciplines, particularly hydrology, meteorology, soil science, geomorphology, economics, and wildlife management. These disciplines
not only brought an enlarged understanding of the
physical environment and its coupling to forest ecology but also brought new conceptual tools, for example, sediment budgets, dissolved chemicals, water
budgets, and heat budgets. In turn, forest ecology has
interested the geosciences and economics in ecosystems. This synergy could lead to a better understanding of ecosystem processes and economic processes
through ecosystem services [3].
Forest ecology’s approach to study was influenced
by agriculture’s clinical approach of using field trials
and correlational studies. Only in the last few decades
has a more process approach (“how things work”)
begun (see Process models). A process approach
has allowed forest ecology to more easily extend
its methodologies beyond case studies and statistical models based on specific data sets (e.g., Ref. 4).
Trees live a long time and, as a result, the establishment of permanent plots with periodic remeasurement
has been a significant part of forestry data collection as far back as the 1700s. The alternatives to
these longitudinal studies are comparative studies
and chronosequences. Comparative studies use measurements of morphology and environmental conditions to establish their statistical relationships and
to infer the functional importance of morphology,
physiology, and interspecific variation. This approach
has important limitations in determining and understanding functional mechanisms (see e.g., Ref. 5).
Chronosequence studies use plots of different ages
to represent the same plot being traced through time.
The assumption is that each plot, although different
in age, has traced exactly the same history up to their
present age. Although this approach is widely practiced, the assumptions underlying this method are
rarely tested, and when they have been, they have
often proved to be invalid (see e.g., Ref. 6).
Introductions to forest ecology can be found in
Refs 7–10. The different contents of these texts
indicate the varying interests of forest ecology.
The rest of this article briefly considers some parts
of forest ecology that have developed approaches
which have been particularly fruitful in recent
decades.
Watersheds and Water Budgets
Forest Services in North America, starting mainly in
the 1950s, set up experimental watersheds in most
different forest types. The water, biogeochemical,
and sediment budgets approach used in watershed
research resulted in a more process-oriented view of
forest ecosystems; this approach allowed a practical
means of organizing and integrating the various
flows of water, chemicals, sediment, heat energy, and
biomass productivity.
Hubbard Brook in New Hampshire, United States
was one of the earliest to profit from this expanded
viewpoint. Early in the 1960s, studies at Hubbard Brook [11] noted the increase in ions of
H, SO4 , and NO2 in wet and dry precipitation.
This “acid precipitation” had been recognized earlier in northern Europe as being due to industrial sources but its effects and biophysical processes were not yet well understood. Because of the
interest in small watershed hydrology (i.e., connections between hillslopes and first-order streams –
(see Catchment hydrology)), biogeochemistry (i.e.,
Encyclopedia of Environmetrics, Online © 2006 John Wiley & Sons, Ltd.
This article is © 2013 John Wiley & Sons, Ltd.
This article was published in Encyclopedia of Environmetrics Second Edition in 2012 by John Wiley & Sons, Ltd.
DOI: 10.1002/9780470057339.vnn137
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Forest ecology
not just nutrient ions), and vegetation ecology (particularly productivity and plant composition), the
Hubbard Brook studies [12] were interested in following the acid precipitation through the canopy
into the forest floor and into the streams. These
studies and others [13, 14] discovered that the
tree canopies acted as exchange surfaces to modify the wet and dry precipitation as it passed
through to the forest floor. The Hubbard Brook studies also explained how increases in mobile anions
of strong acids of sulfur and nitrogen increased
transport (leaching) through the soil profile and
into first-order streams and how these effects were
neutralized by the third- and fourth-order streams
[15, 16]. Leaching is the chemical process of
exchange of cations between a stationary anion
(organic matter and clay) and mobile anions in the
weak electrolyte soil solution.
Hubbard Brook also pioneered watershed manipulations to study the effects of both experimental and
forestry practices on forest populations and biogeochemistry. One of these experiments, the killing of all
plants for two years to exaggerate the biogeochemical response to this unnatural disturbance, proved
useful in understanding the role of the nitrogen cycle
in the recovery from natural and anthropogenic disturbances [17, 18].
Andrews Forest in Oregon is perhaps the bestknown research watershed to the general public
because of its contribution to the spotted owl and oldgrowth issues [19]. Its scientific contribution to forest
ecology included studies on old-growth forests, large
woody debris, and eco-hydrology [20]. Study of oldgrowth in the Andrews Forest also led to recognition
of the importance of large woody debris on carbon
dynamics in both uplands and streams [21, 22]. In
streams, the supply of large tree trunks was crucial
in structuring stream habitat for aquatic organisms,
particularly salmon [23].
Forest Geomorphology
Landscapes are made up of ridgelines, peaks, saddles, and stream courses or hollows (convergent
areas without streams); between these are hung hillslopes. Hillslopes are conveyor belts for downslope movement of sediments and chemicals in
solution. Thus, any section of the hillslope consists of two inputs and one output. The soil (if
not transported by glaciation) is created by weathering from the bedrock, that is, soil production.
Soil above the bedrock is moved into and out of
a hillslope section as a function of slope angle,
soil type, moisture content, and burrowing organisms [24]. These forces create hillslopes of certain
shapes which in turn affect the downslope hydrology and thus create the moisture gradient from
dry at the top of hillslopes to wet at the bottom.
These hydrological processes also carry dissolved
chemical ions, particularly nutrients such as nitrogen, calcium, magnesium, and phosphorus [25, 26].
Many studies have shown the importance of hillslope
geomorphological and hydrological processes and an
increasing number of studies have shown the importance of organisms in creating hillslope processes,
for example, tree uprooting, burrowing, and soil
organisms.
The transfer of water, biogeochemicals, and sediments from uplands (hillslopes) to streams creates
soil moisture–nutrient gradients that are significant
in the plant distributions within watersheds [27, 28].
These moisture–nutrient gradients are the result of
hydrologic and geomorphic processes on the hillslope. Hillslope shape and elevation are the result
of the transfer of sediments and dissolved chemicals downslope and to first-order streams. This in
turn defines how and where streams will form and
how dissected the watershed will be. Since hillslopes are the terrain in which forest ecology is
most interested, this dissection (the amount and steepness) of the uplands is essential to understanding
the physical template on which forest ecosystems
reside.
Ecosystem Management
Ecosystem management calls attention to the fact that
forests must be managed for more than the trees [29].
One significant idea that ecosystem management
introduced was the role of natural disturbance. By
viewing natural disturbances as a recurrent part
of ecosystems, a new model for managing forests
developed, namely, that forestry could try to mimic
natural disturbances. This was a major departure from
the agricultural/silvicultural model and incorporated
the idea that cutting trees in a forest was a kind of
disturbance. Mimicking disturbance has to this point
been largely a regime approach in which descriptors
Encyclopedia of Environmetrics, Online © 2006 John Wiley & Sons, Ltd.
This article is © 2013 John Wiley & Sons, Ltd.
This article was published in Encyclopedia of Environmetrics Second Edition in 2012 by John Wiley & Sons, Ltd.
DOI: 10.1002/9780470057339.vnn137
Forest ecology
such as disturbance type, occurrence, distribution,
size, seasonality, severity, and intensity are thought of
as a multivariate space in which forest management
should attempt to occupy a similar hyperspace as
natural disturbances for a specific ecosystem. A good
description of this approach for the boreal forest of
eastern Canada can be found in Ref. 30. The regime
approach is still a classification/topological approach
and does not necessarily lead to an understanding of
how the disturbance produces a specific ecological
effect. However, despite ecosystem management’s
present limitations in understanding of ecosystem
processes, it is a major step forward in forest ecology
and management.
References
[1]
Puettmann, K.J., Coates, D., & Messier, C. (2009).
A Critique of Silviculture: Managing for Complexity,
Island Press, Washington.
[2] Christensen, N.L., Bartuska, A., Brown, J.H., Carpenter, S., D’Antonio, C., Francis, R., Franklin, J.F.,
MacMahon, J.A., Noss, R.F., Parsons, D.J., Peterson, C.H., Turner, M.G., & Woodmansee, R.G. (1996).
The scientific basis for ecosystem management, Ecological Applications 6, 665–691.
[3] Costanza, R., d’Arge, R., de Groot, R., Farber, S.,
Grasso, S., Hannon, B., Limburg, K., Naeem, S.,
O’Neill, R.V., Paruelo, V., Raskin, R.G., Sutton, P.,
& van den Belt, M. (1997). The value of the world’s
ecosystem services and natural capital, Nature 387,
253–260.
[4]
Maurer, B.A. (1999). Untangling Ecological Complexity, University of Chicago Press, Chicago.
[5] Ackerly, D.D. (1999). Comparative plant ecology and
the role of phylogenetic information, in Physiological
Plant Ecology, M.C. Press, J.D. Scholes, & M.G. Barker,
eds, Blackwell Science, Oxford, pp. 391–413.
[6]
Johnson, E.A. & Miyanishi, K. (2008). Testing the
assumptions of chronosequences in succession, Ecology
Letters 11, 419–431.
[7] Barnes, B.V., Zak, D.R., Denton, S.R., & Spurr, S.H.
(1998). Forest Ecology, 4th Edition, John Wiley & Sons,
Inc., New York.
[8]
Kimmins, J.P. (2004). Forest Ecology: A Foundation
for Sustainable Forest Management and Environmental
Ethics in Forestry, 3rd Edition, Prentice-Hall, Upper
Saddle River.
[9]
Oliver, C.D. & Larson, B.C. (1990). Forest Stand
Dynamics, McGraw-Hill Inc., New York.
[10] Waring, R.H. & Running, S.W. (2007). Forest Ecosystems: Analysis at Multiple Scales, 3rd Edition, Elsevier,
Amsterdam.
3
[11] Likens, G.E., Bormann, F.H., Pierce, R.S., Eaton, J.S.,
& Johnson, N.M. (1977). Biogeochemistry of a Forested
Ecosystem, Springer-Verlag, New York.
[12] Likens, G.E., Driscoll, C.T., & Buso, D.C. (1996). Longterm effects of acid rain: response and recovery of a
forested ecosystem, Science 272, 244–246.
[13] Lindberg, S.E., Lovett, G.M., Richter, D.D., & Johnson,
D.W. (1986). Atmospheric deposition and canopy interactions of major ions in a forest, Science 231, 141–145.
[14] Lovett, G.M. & Lindberg, S.E. (1993). Atmospheric
deposition and canopy interactions of nitrogen in forests,
Canadian Journal of Forest Research 23, 1603–1616.
[15] Johnson, N. (1979). Acid rain: neutralization within
Hubbard Brook ecosystem, Science 204, 497–499.
[16] Hedin, L.O., Likens, G.E., Postek, K.M., & Driscoll,
C.T. (1990). A field experiment to test whether organic
acids buffer acid deposition, Nature 345, 798–800.
[17] Likens, G.E., Bormann, F.H., Johnson, N.M., Fisher,
D.W., & Pierce, R.S. (1970). Effects of forest cutting and
herbicide treatment on nutrient budgets in the Hubbard
Brook watershed ecosystem, Ecological Monographs
40, 23–47.
[18] Vitousek, P.M., Gosz, J.R., Grier, C.C., Melillo, J.M.,
Reiners, W.A., & Todd, R.L. (1979). Science 204,
469–474.
[19] T.A., Spies & S.L. Duncan, eds (2009). Old Growth
in a New World: A Pacific Northwest Icon Reexamined ,
Island Press, Washington.
[20] Swanson, F.J. & Jones, J.A. (2001). Geomorphology and
Hydrology of the H. J. Andrews Experimental Forest,
Blue River, Oregon. Modular Field Guide to the H. J.
Andrews.
[21] Spies, T.A., Franklin, J.F., & Thomas, T.B. (1988).
Coarse woody debris in Douglas-fir forests of Western
Oregon and Washington, Ecology 69, 1689–1702.
[22] Laudenslayer, W.F., Shea, P.J., Valentine, B.E., Weatherspoon, C.P., Lisle, T.E., & Technical Coordinators.
(2002). Proceedings of the Symposium on the Ecology
and Management of Dead Wood in Western Forests. 2–4
November 1999; Reno, NV. (Gen. Tech. Rep. PSWGTR-181. Albany, CA: Pacific Southwest Research Station, Forest Service, U.S. Department of Agriculture),
pp. 949.
[23] Montgomery, D.R. (2003). King of Fish: The ThousandYear Run of Salmon, Westview Press, Boulder.
[24] Anderson, R.S. & Anderson, S.P. (2010). Geomorphology: The Mechanics and Chemistry of Landscapes, Cambridge University Press, Cambridge.
[25] Yoo, K., Amundsen, R., Heimsath, A.M., & Dietrich,
W.E. (2006). Spatial patterns of soil organic carbon
on hillslopes: Integrating geomorphic processes and the
biological C cycle, Geoderma 130, 47–65.
[26] Yoo, K., Amundsen, R., Heimsath, A.M., Dietrich, W.E.,
& Brimhall, G.H. (2007). Integration of geochemical
mass balance with sediment transport to calculate rates
of soil chemical weathering and transport on hillslopes,
Journal of Geophysical Research 112, F02013.
Encyclopedia of Environmetrics, Online © 2006 John Wiley & Sons, Ltd.
This article is © 2013 John Wiley & Sons, Ltd.
This article was published in Encyclopedia of Environmetrics Second Edition in 2012 by John Wiley & Sons, Ltd.
DOI: 10.1002/9780470057339.vnn137
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Forest ecology
[27] Bridge, S.R.J. & Johnson, E.A. (2000). Geomorphic
principles of terrain organization and vegetation gradients, Journal of Vegetation Science 11, 57–70.
[28] Chipman, S.J. & Johnson, E.A. (2002). Understory
vascular plant species diversity in the mixed wood boreal
forest of Western Canada, Ecological Applications 12,
588–601.
[29] F.B. Samson & F.L. Knopf, eds (1996). Ecosystem
Management: Selected Readings, Springer, New York.
[30] S., Gauthier, M.A. Vaillancourt, A. Leduc, L. De.
Grandpré, D. Kneeshaw, H. Morin, P. Drapeau, &
Y. Bergeron, eds (2009). Ecosystem Management in
the Boreal Forest, Presses de l‘Université du Québec,
Québec.
(See also Agroforestry; Ecosystem monitoring;
Forest growth and yield modeling; Forest health
monitoring; Forest inventory; Forestry; Tree morphology)
Encyclopedia of Environmetrics, Online © 2006 John Wiley & Sons, Ltd.
This article is © 2013 John Wiley & Sons, Ltd.
This article was published in Encyclopedia of Environmetrics Second Edition in 2012 by John Wiley & Sons, Ltd.
DOI: 10.1002/9780470057339.vnn137
E. A. JOHNSON