Geography Reference
In-Depth Information
surface temperature of aquatic and terrestrial ecosys-
tems at a high spatio-temporal resolution, a capability
not possible using non-imaging ground-based methods
(e.g., Arscott et al., 2001; Kaushal et al., 2010). However,
a major challenge is to link thermal patch dynamics
with ecological processes. Indermaur et al. (2009a, b),
for example, demonstrated that home range placement
of amphibians in the Tagliamento floodplain depends
on the thermal properties of the individual habitat types
(e.g., large wood deposits that provide thermal refugia),
as well as on the spatial configuration of these habi-
tats. Furthermore, there is clear evidence that the diel
temperature pulses are ecologically more relevant than
the average daily temperature. Microbial activity, for
example, immediately reacts to short-term alterations in
temperature leading to rapid alterations in ecosystem res-
piration when temperature changes. Therefore, ignoring
local-scale and short-term thermal dynamics may lead to
false conclusions about environmental change impacts on
ecosystems. Concurrently, the effects of global warming
can be attenuated by manipulating specific habitat char-
acteristics and processes such as vegetation cover and the
exchange between subsurface and surface water.
The use of airborne vehiclesmountedwithTIR imaging
sensors can be extended to map the riparian areas, for
example, mapping floodplains at different flowconditions
and studying the distribution and density of terrestrial
mammals such as deer or wild boar during flood events
(e.g., Naugle et al., 1996). Furthermore, the TIR technique
can be used in combination with other sensors such as
LIDAR to quantify the three-dimensional heterogeneity
of river floodplains.
5.8 Example 2: Thermal heterogeneity
in river floodplains used to assess
habitat diversity
In this example, we expand our scope from looking at
water innarrow streamand river reaches usingmulti-scale
data, to show an example of thermal heterogeneity in the
river floodplain as an indicator of habitat diversity. River
floodplains are transitional areas that extend from the
edge of permanent water bodies to the edge of uplands.
In their natural state, they are among the most complex,
dynamic, and diverse ecosystems globally, characterised
by interacting flow, thermal, and sediment pulses that
provide a complex 'template' to which organisms are
adapted and by which ecosystem processes are controlled
(Naiman et al., 2005; Stanford et al., 2005; Tockner et al.,
2010). Although the changes in the composition and the
configurationof habitat types have beenwell documented,
little is known about thermal patch dynamics at the land-
scape scale (cf. Cardenas et al., 2008; Smikrud et al., 2008).
Thermal patch dynamics are expected to control the dis-
tribution of aquatic and terrestrial organisms as well as
of animals that exhibit complex life cycles (e.g., aquatic
insects, amphibians). Furthermore, information on ther-
mal heterogeneity is required to 'scale-up' ecosystem
processes from the patch to the entire ecosystem.
In a recent study, Tonolla et al. (2010) applied ground-
basedTIR images toquantify surface temperature patterns
at 12-15 minute intervals over 24 h cycles in near-
natural Alpine river floodplains (Roseg, Tagliamento
River; Figure 5.11). Each habitat type exhibited a distinct
thermal signature creating a complex thermal mosaic. The
diel temperature pulse and maximum daily temperature
were the main thermal components that differentiated
the various aquatic and terrestrial habitat types. In both
river floodplains, exposed gravel sediments exhibited the
highest diel pulse (up to 23 C) while in aquatic habitats
the pulse was as low as 11 C. At the floodplain scale,
thermal heterogeneity was low during night-time but
strongly increased during day time, thereby creating a
complex shifting mosaic of thermal patches (Figure 5.11).
However, TIR images only record T r at the water sur-
face. Within the top 29 cm of the unsaturated gravel
sediments, thermal heterogeneity was as high as across
the entire floodplain at the surface (Tonolla et al., 2010).
This strong vertical gradient should be considered when
calculating temperature-dependent ecosystem processes.
This study emphasised that remotely sensedTIR images
provide a unique opportunity to simultaneously map
5.9 Summary
In this chapter, we showed how TIR measurements
can be used for observing water temperature in river-
ine landscapes for practical applications. We explored
the theoretical basis of TIR observations of water tem-
perature, data sources, the processing steps necessary
to obtain accurate estimates of temperature in riverine
environments from TIR data, and the validation of such
temperature estimates. We also provided some multi-
scale examples of the application of TIR data in riverine
ecology and management. At the end of each section,
and in Table 5.1, we have summarised some of the key
points for managers using TIR data to monitor water
temperature of stream and rivers. We hope that the
Search WWH ::




Custom Search