Chemistry Reference
In-Depth Information
Due to limitations in the understanding of forest physiology, climate and
mortality, forest die-offs are a big uncertainty in climate projections of
terrestrial ecosystem impacts, climate/ecosystem interactions and carbon-cycle
feedbacks.
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Scientists are always seeking greater understanding of the
complex mechanisms leading to forest dieback, migration and shifts in species
dominance to help predict where and when these changes may occur.
Soils hold important clues about shifts in hydrology and vegetation across
the landscape because, in terrestrial systems, soil characteristics govern the
reception, storage and redistribution of precipitation. This, in turn, determines
the supply of plant-available water and, indirectly, the nutrients necessary for
plant establishment and growth. Because soils with more water are less
sensitive to warming, changes in soil moisture result in changes in soil heat
capacity and conductivity, which, in turn, affect infiltration and water
transport in the soil profile.
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Soil response to changes in precipitation has
implications for vegetation water needs, fire risk, pest outbreaks, infiltration
rates and groundwater recharge;
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therefore, in-depth analyses of these soil
characteristics can give scientists and managers the tools they need to predict
where trees will be most vulnerable to future water stress and where they will
be most likely to establish and thrive under future conditions.
In this chapter, we review existing literature for examples of on-going forest
responses to climate change, many of which are also exacerbated by
anthropogenic stressors. We discuss the implications for the global carbon,
nitrogen and hydrological cycles and how resulting changes in forest lands and
associated ecosystem services may affect food security in the future. We
conclude by providing a method to use soil characteristics to inform land
managers of challenges they may face in preserving valuable services from
forested lands and cropping systems.
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Projected Trends in Climate Change
2.1 General Climate Trends
Rising temperatures have been recorded around the world and are projected to
continue to rise, with regional and local patchiness, causing an overall decrease
in the longevity, extent, and thickness of glaciers, ice sheets, and snowpacks.
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Observations have shown that land has been warming up at a faster rate than
oceans, due to the greater inertia of deep oceans. Sea-level rise projections
presented in the last IPCC report
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were extremely conservative, and new
publications suggest that higher levels are likely to be reached by the end of the
century, if current trends of ice-melting and ocean-warming continue.
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Global warming is likely to drive an increase in global mean precipitation
(rain and snowfall). However, the degree of spatial and seasonal variation
remains large, even when considering multi-model means. All simulations
point to increases in precipitation at high latitudes where more rain than snow
has recently been observed, a trend that probably will continue as winter
