223Chapter 11
Combined Stresses in Forests
Patrick Mitchell, Tim Wardlaw and Libby Pinkard
© Springer International Publishing Switzerland 2015
R. Mahalingam (ed.), Combined Stresses in Plants, DOI 10.1007/978-3-319-07899-1_11
P. Mitchell () · L. Pinkard
CSIRO Land and Water Flagship, Private Bag 12, Hobart,
Tasmania 7001, Australia
e-mail: [email protected]
T. Wardlaw
Forestry Tasmania, 79 Melville Street, Hobart, Tasmania 7000, Australia
11.1 What Is Stress to a Tree or Forest Ecosystem?
Environmental stress can be viewed as the physical, chemical, and biological con-
straints on the productivity and development of ecosystems. For plants, Grime
( 1977 ) hypothesized that stress is one of the three fundamental drivers shaping plant
strategies and he defined stress as a set of external constraints limiting the rate
of resource acquisition, growth, or reproduction (Grime 1977 ). Stress, in a broad
sense, is the major force limiting species distribution and ecosystem structure and
function. Forest ecosystems are maintained in a dynamic equilibrium by continu-
ous stress-inducing factors, as well as stochastic disturbance events. For example,
primary climatic stress factors can be broadly categorized as light, temperature,
and water and largely explain the distribution of biomes and forest types globally
(Boisvenue and Running 2006 ). Competitive and other biotic interactions are also
important in limiting species and population distribution and function. Thus, the
role of stress in triggering and shaping plant functioning is complex and can be bet-
ter understood by considering responses that arise when a particular individual or
population is exposed to conditions outside its normal operating range.
The impacts of stress on growth and development are evident at different tem-
poral scales for both individuals and populations (Fig. 11.1a). At the whole-plant
level, the initial stress response or period of decline in a process such as growth or
photosynthesis, happens within seconds to days. Acclimation can follow the ini-
tial response and involves compensation or enhanced resistance to the initial stress