Ecophysiological Variability of Alnus viridis (Chaix) DC. Green Alder Leaves in the Bieszczady Mountains (Poland)

Abstract

Alnus viridis (Chaix) DC., green alder, is a fast-growing shrub that grows expansively in the European mountainside. In Poland, A. viridis naturally occurs only in the Bieszczady Mountains (south-eastern part of the country), above the upper forest border. In this study, we assessed the potential of green alder to expand in post-farming areas in the Bieszczady Mountains. We investigated the effects of topographical, climatic, and edaphic characteristics of four various study sites on the physiological and morphological properties of A. viridis leaves in order to answer the question whether the growth of plants in lower positions improves their physiological condition to such an extent that it increases the species invasiveness. This is the first comprehensive ecophysiological study of this species to be carried out in this part of Europe. The photochemical efficiency of PSII, the chlorophyll content, and leaf ¹³C and ¹⁵N discrimination were analyzed. On the basis of leaf radiation reflection, coefficients such as reflectance indices of anthocyanins, carotenoids, flavonoids (ARI2, CRI1, FRI), photochemical index of reflection (PRI), and the water band index (WBI) were calculated. We observed favorable physiological effects in A. viridis plants growing in locations below the upper forest border compared to plants growing in higher locations. As a result, A. viridis may become an invasive species and disturb the phytocoenotic balance of plant communities of the altitudinal zones in the Polish Western Carpathians.

Keywords: 13C discrimination; 15N discrimination; JIP-test; chlorophyll a fluorescence; green alder; reflectance.

Figure 1

Normalized fluorescence induction curves (Vt) of Chl a fluorescence of green alder (Alnus viridis) leaves recorded in July (filled points) and September (empty points) in localities at different elevations, 586, 980, 1215, and 1320 m a.s.l. (a) The differential fluorescence curves (ΔVt) obtained by subtracting the Chl a fluorescence values on the O‒P phase from all field sites (b), as described in Methods.

Figure 2

Differential fluorescence curves (ΔVt) of green alder (Alnus viridis) leaves for phases: (a) O‒K, (b) O‒J, (c) J‒I, and (d) I‒P, normalized to values corresponding to characteristic points in transitions of the chlorophyll fluorescence induction curve. The curves for individual sections were obtained by subtracting the Chl a fluorescence values recorded in July from the curves obtained in September. As a control for each field test stand, the curve obtained in July was adopted, as described in Methods.

Figure 3

Values of selected Chl a fluorescence parameters of green alder (Alnus viridis) leaves (in % of control), recorded in (a) July and (b) September all field sites—in localities at elevations 980, 1215, and 1320 m a.s.l. The control was based on values from the lowest locality (586 m a.s.l.).

Figure 4

Reflectance curves for leaves of green alder (A. viridis) plants growing in the Bieszczady Mts. at different elevations: 568, 980, 1215, and 1320 m a.s.l. (a) reflectance—inset is an enlarged graph of PAR reflection; (b) reflectance difference—calculated by subtracting reflectance intensity values (%) for plants growing 568 m a.s.l. from reflectance intensity values for plants growing 980, 1215, or 1320 m a.s.l., respectively (see Material and methods); (c) sensitivity—calculated by dividing the RD values by mean reflectance values (%) for plants growing at 568 m a.s.l., N = 40.