Risto Jalkanen, Sheila Hicks, Tarmo Aalto, Hannu Salminen. (2008). Past pollen production reconstructed from needle production in Pinus sylvestris at the northern timberline: a tool for evaluating palaeoclimate reconstructions. Silva Fennica vol. 42 no. 4 article id 230. https://doi.org/10.14214/sf.230

Keywords: Scots pine; age-depth chronology; annual resolution; needle trace method; NTM; pollen accumulation rate; temperature reconstruction; tree line

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Annual needle production (PROD) of Scots pine (Pinus sylvestris L.) and pine pollen accumulation rates (PAR) are compared along a 5-site transect from the Arctic Circle to the northern timberline. PROD is calculated using the Needle Trace Method (NTM). PAR is monitored by two series of pollen traps, located in the centres of mires and within forests, respectively. There is a strong year-to-year agreement in PAR and PROD between the sites for the common 19-year period for which both proxies are available. Mean July temperature of the previous year (T_JUL–1) correlates statistically significantly with PROD at all five sites and with PAR in the four northernmost sites. There is also a significant relationship between T_JUN–1 and PROD at all sites, and T_JUN and PAR at the two northernmost sites. PROD and PAR correlate most strongly in the three near tree line sites, where PROD explains up to 51% of the variation in PAR. On the basis of the calibration between PROD, PAR and T_JUL–1, PROD and T_JUL–1 are used to reconstruct past PAR. That such a reconstruction is realistic is supported by its agreement with the pollen record for 1982–2000 and with records of male flowering for the period 1956–1973. The use of PROD in reconstructing past PAR can help in interpreting the fossil pollen signal in terms of climate rather than vegetation change and in evaluating the high-resolution dating of peat profiles and calculations of the rate of peat accumulation.

Jalkanen, Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: risto.jalkanen@metla.fi
Hicks, Institute of Geosciences, P.O. Box 3000, FI-90014 University of Oulu, Finland E-mail: sh@nn.fi
Aalto, Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: ta@nn.fi
Salminen, Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: hs@nn.fi

article id 360, category Research article

Timo Kurkela, Tarmo Aalto, Martti Varama, Risto Jalkanen. (2005). Defoliation by the common pine sawfly (Diprion pini) and subsequent growth reduction in Scots pine: a retrospective approach. Silva Fennica vol. 39 no. 4 article id 360. https://doi.org/10.14214/sf.360

Keywords: height growth; NTM; defoliation; insect attack; needle density; needle production; needle retention; radial growth; herbivory

Abstract | View details | Full text in PDF | Author Info

The foliage status in the main stem of Scots pines (Pinus sylvestris) was studied retrospectively using the needle trace method (NTM) on a stand, seriously defoliated by the pine sawfly (Diprion pini) in the 1980s. Needle density increased abruptly in the seasons following the defoliation. The strongest reduction in annual needle production occurred one year later. As a consequence of lower needle production, the annual number of attached needles decreased three to five years after the defoliation. Needle retention and the average age of attached needles tended to increase after defoliation. In analyses of covariance with the NTM variables, needle density (logarithmic transformed values) and average age of attached needles, had the highest, significant, negative relationship with radial and height increments both in the period prior to the defoliation and in the time when the trees were suffering from defoliation. The relationships between height increment and the number of needles and needle loss were positive and significant. Also radial increment had a positive relationship with the number of needles but not with needle loss. Interestingly, an abrupt increase in the needle density gave a good indication of the effects of a sudden defoliation in pines.

Kurkela, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: timo.kurkela@metla.fi
Aalto, Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: ta@nn.fi
Varama, Finnish Forest Research Institute, Vantaa Research Unit, P.O. Box 18, FI-01301 Vantaa, Finland E-mail: mv@nn.fi
Jalkanen, Finnish Forest Research Institute, Rovaniemi Research Unit, P.O. Box 16, FI-96301 Rovaniemi, Finland E-mail: rj@nn.fi

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