Models of litterfall production for Scots pine ( Pinus sylvestris L.) in Finland using stand, site and climate factors

Abstract

The aim of this study was to identify the most significant site, stand and climate factors affecting needle (LF needle) and total (LF total) above-ground litterfall production and to develop multiple linear regression (MLR) models that can be used to reliably predict litterfall production in the boreal zone using readily available variables. Unlike most other litterfall production studies, we use climate data for the actual sites and annual litterfall values. A data set including 34 Scots pine stands located throughout Finland was compiled. The data for some stands covered a period of more than 30 years. The age of the stands ranged from 35 to >200 years and all were growing on upland, mineral soil sites. Stand mean annual LF needle ranged from 22 g m −2 (northern Finland) to 157 g m −2 (southern Finland); corresponding values for LF total were 32 and 230 g m −2. Annual LF needle production accounted between 49 and 75% of stand LF total production and explained 88% of the variation in LF total over all stands. There was considerable annual variation in litterfall production also within the same stand. The coefficient of variation in LF needle in each stand ranged from 4 to 58% (mean = 19%) and from 3 to 39% (mean = 22%) for LF total. Both LF needle and LF total were highly significantly ( p < 0.01) and strongly correlated (Spearman) with latitude, stand basal area, effective temperature sum (ETS) of the current year and even higher with that of the previous year, and the previous years’ July temperature. LF needle had a weak negative, although significant ( p < 0.05) correlation with stand age, but age was not significant for LF total. MLR models using latitude and stand basal area (also dominant tree height in the case of LF needle) as predictive variables accounted for 82% of the variance in both LF needle and LF total. The standard error of the estimate (SE est) was 12.6 g m −2 for LF needle and 23.3 g m −2 for LF total. Latitude effectively described the climate at each stand but ignored the considerable within-stand variation in annual litterfall production. Using the annual values for the climate variables instead of latitude, 70% or more of the variation in both LF needle and LF total in MLR models could be explained. The models are useful tools for predicting annual litterfall in mature Scots pine stands for use in soil organic and carbon models.