The species-specific relationship of leaf mass per area components to light and moisture

Abstract

The aim of this study was to investigate at the interspecific level to what extent the number of mesophyll cell layers and the leaf dry mass content (LDMC) – key determinants of leaf mass per area (LMA) – adapt to the ambient light and habitat moisture preferred by the species. The number of mesophyll cell layers was indirectly characterised by the quotient of thickness of chlorophyll-bearing mesophyll (Mth) and the anticlinal length of the mesophyll cells (aMCL). The leaves of 131 species from forests and acidic dry grasslands were sampled in the Federal State of Brandenburg in north-eastern Germany. Their light and moisture preferences were characterised using the light and moisture indicator values of Tichý et al. (2023), their geobotanical distribution within terrestrial plant communities arranged along a gradient of community-weighted mean light values and their classification according to preferences for forests and open land (Schmidt et al., 2002). The Mth/aMCL ratios correlated significantly and positively with increasing light levels and negatively with increasing habitat moisture. However, the variability of these relationships was high.

The water relations of the entire plant may differ from those of the leaves, for example due to deep roots. Therefore, LDMC was used to characterise water relations, especially of the leaves. The Mth/aMCL ratio did not correlate with LDMC. The study of light-loving species with known root system data showed that variation in rooting depth and the avoidance of dry periods influenced LDMC but not the Mth/aMCL ratio. This difference in the relationships of the Mth/aMCL ratio to light and moisture, in addition to the high variability in its correlation with light, suggests that the effects of light or moisture on LMA – commonly measured in ecological studies – should be viewed with caution.