Climatic drivers of Picea growth differ during recruitment and interact with disturbance severity to influence rates of canopy replacement

• Published in: Agricultural and forest meteorology 2020-06, Vol.287, p.107981, Article 107981
• Main Authors: Saulnier, M., Schurman, J., Vostarek, O., Rydval, M., Pettit, J., Trotsiuk, V., Janda, P., Bače, R., Björklund, J., Svoboda, M.
• Format: Article
• Language: English
• Subjects: Canopy recruitment; Climate change; Dendrochronology; Disturbance severity; Environmental Sciences; Global Changes; Resilience of primary spruce forests; Tree demographics
• ISSN: 0168-1923; 1873-2240
• DOI: 10.1016/j.agrformet.2020.107981

•Disturbances provide opportunities for tree recruitment and canopy replacement.•We used tree rings to study tree growth during recruitment/recruitment duration.•Disturbance severity and growth history shape individual recruitment responses.•Tree growth during recruitment is uniquely sensitive to winter climatic conditions.•Accelerating recruitment dynamics in the Carpathians imply links to global change. While shifting disturbance rates and climate change have major implications for the structure of contemporary forests through their effects on adult tree mortality, the responses of regenerating trees to disturbances and environmental variation will ultimately determine the structure and functioning of forests in the future. Assessing the resilience of forests to changing conditions requires information on what constrains tree performance during recruitment and whether recruitment dynamics have changed throughout history. We analyzed growth patterns in a large sample of tree cores (n = 14 793) collected from primary Picea forests throughout the Carpathian Mountains. Growth rate anomalies recorded in tree-rings permitted the reconstruction of several key recruitment and disturbance parameters: (1) whether individuals were recruited after a period of competitive suppression (Released Trees; RT; 66% of trees) or immediately following gap formation (Gap Recruited Trees; GRT; 33%), (2) growth rates during recruitment, (3) the duration of recruitment and (4) historical disturbance severity variation. High neighborhood density led to lower growth rates in RTs, but favored a higher growth rate in GRTs. Winter temperatures were positively correlated with Picea growth during recruitment, GRTs were also more sensitive to winter precipitation. Recent increases in growth during recruitment and reductions in recruitment intervals suggest that rates of canopy replacement have increased over recent decades. Assessments of forest resilience must recognize that constraints on tree growth differ during recruitment and interact with disturbance severity. An individual's experience prior to competitive release and factors altering the immediate abiotic conditions of a recruiting individual (competition and disturbance severity) are important determinants of canopy replacement rates; these recruitment parameters will certainly interact with shifting disturbance regimes. Ultimately, increasing growth rates and decreasing recruitment intervals suggest that forest dynamics are ac