Beyond succession: Abiotic conditions shape upper andean mountain forests seed-bank and seedling assemblages

Soil seed banks, seedlings, and adult plant communities assemble in response to multiple environmental filters; yet we lack clarity on whether successional stage or local heterogeneity plays the dominant role in upper Andean forests. We investigated whether community assembly at different life stages is primarily shaped by forest succession stage or fine-scale local variability. We tested whether local abiotic heterogeneity offsets successional effects, because differences in soil moisture, bulk density, and temperature filter propagule germinability and persistence more strongly than changes linked to stand age. We surveyed four upper Andean Forest localities across early- and late-successional stages. α-diversity and seed/seedling densities did not differ by forest successional stage. Instead, locality explained β-variation in seed banks, seedlings, and adults, respectively, with high turnover. Furthermore, lower seed bank density was associated with higher soil organic carbon content, while higher seedling density was associated with elevated soil temperature. These results shows that fine-scale abiotic heterogeneity governs the assembly of early-life stages in these upper-Andean forests. • Local environmental heterogeneity explained more variation in plant communities than forest successional stage. • Seed bank and seedling richness did not differ between early and late-successional stage forests. • Lower SSB density associated with high SOC, and higher SDL density with warmer soils. Local turnover dominated β-diversity • Fine-scale abiotic variation was associated with differences in early plant life stages in Andean forests.