Principles of terrestrial ecosystem ecology.pdf

384 Glossary
or from the ecosystem to groundwater or
aquatic ecosystems.
Leaf area index. Leaf area per unit ground
area. Projected LAI is the leaf area projected
onto a horizontal plane.Total LAI is the total
surface area of leaves, including the upper
and lower surface of flat leaves and the
cylindrical surface of conifer needles; it is
approximately twice the value of projected
LAI, except in the case of conifer needles,
where the projected leaf area is multiplied by
p (3.1416) to get total leaf area.
Leaf mass ratio. Ratio of leaf mass to total
plant mass.
Legacy. Effect of past events on the current
functioning of an ecosystem.
Life history traits. Traits (e.g., seed size and
number, potential growth rate, maximum
size, and longevity) of an organism that
determine how quickly a species can get to a
site, how quickly it grows, how tall it gets, and
how long it survives.
Light compensation point. Light intensity at
which net photosynthesis equals zero.
Light-harvesting reactions. Reactions of
photosynthesis that transform light energy
into chemical energy.
Light saturation. Range of light intensities
above which the rate of photosynthesis is
insensitive to light intensity.
Light use efficiency. Ratio of gross primary
production to absorbed photosynthetically
active radiation at the leaf or ecosystem
scale.
Limitation. Reduced rate of a process (e.g., net
primary production, growth or photosynthesis)
due to inadequate supply of a resource
(e.g., light) or low temperature.
Lithosphere. Hard outermost shell of Earth.
Litter. Dead plant material that is sufficiently
intact to be recognizable.
Litterbag. Mesh bag used to measure decomposition
rate of detritus.
Litterfall. Shedding of aboveground plant
parts and death of plants.
Littoral zone. Shore of a lake or ocean.
Loam. Soil with substantial proportions of at
least two size classes of soil particles.
Loess. Soil derived from wind-blown silt
particles.
Longwave radiation. Radiation with wavelengths
3000 to 30,000nm.
Macrofauna. Soil animals larger than 10mm in
length.
Macronutrients. Nutrients that are required in
large quantities by organisms.
Macropores. Large pores between soil aggregates
that allow rapid movement of water,
roots, and soil animals.
Maintenance respiration. Respiration used to
support maintenance of live biomass.
Mantle. Fungal hyphae that surround the
root in ectomycorrhizae; also termed
sheath.
Mass flow. Bulk transport of solutes due to the
movement of soil solution.
Mass wasting. Downslope movement of soil or
rock material under the influence of gravity
without the direct aid of other media such as
water, air, or ice.
Matric potential. Component of water potential
caused by adsorption of water to surfaces;
it is considered a component of
pressure potential in some treatments.
Matrix. Predominant patch type in a landscape.
Mean residence time. Mass divided by the
flux into or out of the pool over a given
time period; synonymous with turnover
time.
Mechanical weathering. Physical fragmentation
of the rock without chemical change.
Mesofauna. Soil animals 0.2 to 10mm in
length.
Mesopause. Boundary between the mesosphere
and thermosphere.
Mesophyll cells. Photosynthetic cells in a leaf.
Mesosphere. Atmospheric layer between the
stratosphere and the thermosphere, which is
characterized by a decrease in temperature
with height.
Metamorphic rocks. Sedimentary or igneous
rocks that are modified by exposure to heat
or pressure.
Metapopulations. Populations of a species
that consist of partially isolated
subpopulations.
Methanogen. Methane-producing bacteria.
Methanotroph. Methane-consuming bacteria.