Recruitment dynamics in conifer-dominated uneven-aged forests in the carpathians

Abstract

In permanently uneven-aged forests, continuous ingrowth of recruitment into higher stand layers is a critical process for the formation and maintenance of differentiated stand structures. This study analyses the abundance and diversity of recruitment (diameter at breast high (DBH) 0.1–4 ​cm) across 241 research plots in 11 structurally differentiated Norway spruce (silver fir)-dominated forest stands distributed at altitudes between 500 and 1,440 ​m a.s.l. The influence of light conditions and lateral competition characteristics on the height increment and crown architecture of recruitment was investigated in detail for 352 Norway spruce and 361 silver fir trees. Light-related variables were confirmed to directly affect the recruitment distribution only to a limited extent. Under relatively low light conditions in montane stands, silver fir reached higher height increments than Norway spruce. The better adaptation of silver fir to shaded conditions was reflected also in its higher apical dominance ratio compared to Norway spruce. The height increment and apical dominance ratio of Norway spruce and silver fir recruitment were positively correlated with indirect radiation, DBH, and relative crown length (RCL), but not with lateral competition. These results confirm that the regulation of light conditions in permanently uneven-aged stands is crucial for the growth dynamics of recruitment, as well as for the future proportions of Norway spruce and silver fir in mixed, structurally diverse stands.