Complex sentence: Emphasis in the 1950s centered on systems for roading and for harvesting old-growth forests, while esearch in the 1960s focused on effects of logging on water, sediment, and nutrient losses from small watersheds.
Split into simpler sentences: Emphasis in the 1950s centered on systems for roading and for harvesting old-growth forests. Research in the 1960s focused on effects of logging on water, sediment, and nutrient losses from small watersheds.