Sub-regional variation in the structure, composition and ecology of old-growth floodplain forests in the Pacific Coastal Temperate Rainforest

A strong understanding of regional variation in structure and composition of old-growth floodplain forests and ecosystem drivers is critical for improving riparian old-growth management. We reviewed the literature to develop a framework to evaluate these and the relative roles of climate, disturbance, other drivers and their interactions. We then examined forest structure from 17 plots across ~11° of latitude along the northern Pacific Coastal Temperate Rainforest (PCTR). Mean annual temperature and precipitation were the most influential drivers of stand structure. Several flood proxies correlated with structural attributes suggesting that hydrological disturbance is a key driver of structure, likely driving greater variability among floodplain stands than upland stands. Northern plots showed slower stand development compared to southern plots, differences in structure suggest a need to re-evaluate sub-regional boundaries of the PCTR. Delineating sub-regional boundaries are important for monitoring and predicting how climate change will affect these forests and their disturbance regimes.