Dendroecological studies of trees outside forests (TOF) – A systematic review

Dendroecology offers insights into plant species responses to abrupt and long-term shifts in environmental conditions, but studies are predominantly focused on trees in forest ecosystems. This systematic literature review examines the prevalence and patterns of dendroecological studies conducted outside forest habitats. Utilizing the PRISMA framework, we systematically searched the Web of Science and identified 59 relevant publications encompassing 217 sampling sites across 26 countries. The studies showed a strong geographic bias towards temperate and cold regions, primarily in the Northern Hemisphere, and a scarce research cover from arid regions, where TOFs are highly present. We found a focus on urban and agricultural settings, and a predominant emphasis on Pinaceae, revealing a lack of knowledge on a broader set of TOF species. Tree-ring width was identified as the primary method for assessing climate-growth relationships in the studies, while wood anatomy, wood density, and stable isotopes were used less frequently. Our findings indicate a strong positive correlation between precipitation and tree growth across various climates, while temperature exhibited mixed effects. The underrepresentation of studies in the Tropics and the Southern Hemisphere, the taxonomic composition of TOF dendroecology, and the predominance from ring width as a parameter to study growth highlight a critical bias in current knowledge. To advance TOF dendroecology, future research must prioritize sampling sites where TOFs are highly present, obtaining metadata related to management and stand origin, and adopting a multi-parameter approach to understand climate-growth relationships to create a more comprehensive framework for understanding global tree-growth dynamics .