influence du climat et de la prédation sur l'utilisation de l'habitat et la ...

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3.5. Discussion
Relationship between abundance of porcupines and solar irradiance
We observed a strong decline in abundance of porcupines from 2000 ongoing. Density of
porcupines concomitantly dropped (from ca. 40 to ca. three animaIs per km 2 between 2000
and 2006, Y. Lemay UQAR, unpublished data) in other areas of the Parc National du Bic
where no captures were performed so that we are confident that our study design is not
responsible for the observed dec\ine. As it was hypothesized from Klvana et al. (2004),
changes in abundance of porcupines were correlated to solar irradiance at our study site. Our
first prediction was therefore supported. We now discuss how solar activity could influence
abundance of porcupines in eastern Québec through cascading effects on winter precipitation,
win ter survival rates, and predation rates on porcupines.
Relationship between solar irradiance and winter precipitation
We found that high solar activity was associated with low levels of winter precipitation.
Klvana et al. (2004) also found a link between solar activity and winter precipitation when
analysing weather records for the same area for the 1877-2000 time period. In their study,
both time series showed regular periodicities, with a lag of four to five years between the two
cycles. A significant number of studies have found correlations between solar activity and
different meteorological parameters (reviews in Tsiropoula 2003, Versteegh 2005). Positive,
negative or non-existent correlations have been reported between local weather and solar
activity. Sorne were direct (e.g. Currie 1993, Lean et al. 1995) white others were delayed
correlations (e.g. Perry 1994, 2006). Such conflicting evidence gives a confusing and
contradictory picture of solar influences on the earth 's climate. One reason for this confusion
may be that solar effects on meteorological parameters differ in various geographical regions
and at different time periods. Indeed, sorne reversaIs between solar activity and weather
variables have been reported in the literature. We found no significant correlation between
solar irradiance, snowfall and spring tempe rature between 1998 and 2004 white Klvana et al.
(2004) found those series to remain in phase between 1877 and 2000. One explanation may
be that we were faced with a breakdown of the link between solar irradiance and sorne local
parameters. Alternatively, the statistical tool we used (i .e. direct correlations) may have been