 |
| Titel |
Probing the past 30-year phenology trend of US deciduous forests |
| VerfasserIn |
X. Yue, N. Unger, T. F. Keenan, X. Zhang, C. S. Vogel |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1726-4170
|
| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 12, no. 15 ; Nr. 12, no. 15 (2015-08-06), S.4693-4709 |
| Datensatznummer |
250118053
|
| Publikation (Nr.) |
 copernicus.org/bg-12-4693-2015.pdf |
|
|
|
|
|
| Zusammenfassung |
| Phenology is experiencing dramatic changes over deciduous forests in the
USA. Estimates of trends in phenology on the continental scale are
uncertain, however, with studies failing to agree on both the magnitude and
spatial distribution of trends in spring and autumn. This is due to the
sparsity of in situ records, uncertainties associated with remote sensing data, and
the regional focus of many studies. It has been suggested that reported
trends are a result of recent temperature changes, though multiple processes
are thought to be involved and the nature of the temperature forcing remains
unknown. To date, no study has directly attributed long-term phenological
trends to individual forcings across the USA through integrating
observations with models. Here, we construct an extensive database of ground
measurements of phenological events across the USA, and use it to calibrate
and evaluate a suite of phenology models. The models use variations of the
accumulative temperature summation, with additional chilling requirements
for spring phenology and photoperiod limitation for autumn. Including a
chilling requirement or photoperiod limitation does not improve model
performance, suggesting that temperature change, especially in spring and
autumn, is likely the dominant driver of the observed trend during the past
3 decades. Our results show that phenological trends are not uniform over
the contiguous USA, with a significant advance of 0.34 day yr−1 for
the spring budburst in the east, a delay of 0.15 day yr−1 for the
autumn dormancy onset in the northeast and west, but no evidence of change
elsewhere. Relative to the 1980s, the growing season in the 2000s is
extended by about 1 week (3–4 %) in the east, New England, and the upper
Rocky Mountains forests. Additional sensitivity tests show that
intraspecific variations may not influence the predicted phenological
trends. These results help reconcile conflicting reports of phenological
trends in the literature, and directly attribute observed trends to
long-term changes in temperature. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|