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| Titel |
Longer vegetative seasons and colder winters may be responsible for increased net ecosystem productivity in a deciduous forest in southern-central Indiana |
| VerfasserIn |
Danilo Dragoni, H. P. Schmid, C. Wayson, C. S. B. Grimmond, J. C. Randolph, H. Potter |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250042288
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| Zusammenfassung |
| Changes in current climatic conditions are well documented at both local and global scales.
While there is a general consensus on the causes and the expected trends for these changes,
large uncertainties affect the predictions on the future roles of temperate forests
in offsetting anthropogenic carbon emissions. This uncertainty mainly originates
from the incomplete understanding of the mechanisms and controls that regulate
the carbon cycle in forest, but also by a general lack of long-term measurements
that could otherwise reveal trends in carbon, water and energy exchange between
the ecosystem and the atmosphere. The AmeriFlux site in the Morgan Monroe
State Forest in Indiana (MMSF) has been collecting observations on net ecosystem
exchange (NEE) of carbon and its environmental drivers since 1998, and for this
reason is one of the few sites in North America with the possibility of performing a
decadal analysis on net ecosystem productivity (NEP) trends. Despite the large
inter-annual variability in NEP, the observations show a significant increase in net
forest productivity over the past 10 years (about 100 gC m-2). This increase in
productivity is hypothesized to be caused by changes in phenology and carbon cycle
occurring as a result of climate changes. Different independent techniques were used to
determine the start, the end, and the length of the vegetative season, including ground-,
eddy-covariance-, and remote sensing-based approaches. Remarkably, the majority shows
the same trends and they provide evidence for longer vegetative seasons that are
caused by extension of the vegetative activity in the fall. Both phenological and flux
observations indicate that the vegetative season extended later in the fall with an
increase in length of about 3 days year-1. However, these changes are responsible
for only 50% of the total annual gain in forest productivity in the past decade. A
negative trend in air and soil temperature during the winter months may explain
an equivalent increase in net uptake through a decrease in ecosystem respiration. |
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