Sphagnum outcompetes feathermosses in their photosynthetic adaptation to postharvest black spruce forests

Mosses dominate the understory of black spruce forest, and changes in moss community composition and functional traits may influence many important ecosystem processes, particularly paludification due to accumulation of peat (mainly Sphagnum). To understand performance and fitness of ground-cover mosses in early forest succession following clearcutting, we investigated photosynthetic traits in Sphagnum and three feathermoss species (i.e., Hylocomium, Ptilium, and Pleurozium) coexisting in mature stands and decade-old black spruce harvest blocks. The results showed that all of these mosses have a significantly higher light saturation point at the harvested plots than the forested plots. Feathermosses at the harvested plots all underwent a reduction in quantum efficiency, chlorophyll b content, and chlorophylls:carotenoids ratio related to photoinhibition, particularly Pleurozium, which experienced a significant decrease in maximum net photosynthesis. In contrast, Sphagnum showed a significant increase in maximum gross photosynthesis, dark respiration, and the ratio of chlorophyll a:b at the harvested plots compared with the forested plots. The distinctive responses of moss photosynthetic traits indicate the potential proliferation of Sphagnum and decrease of feathermosses, and thus consequent peat accumulation. Our results emphasize the importance of the photosynthetic traits of moss as indicators of postharvest conditions for enhancing understory vegetation management to maintain and improve productivity of black spruce.

Ground Cover Management Can Revitalize Black Walnut Trees

Many black walnut plantations have been successfully established in recent years, but not all have continued to grow well after establishment. In one 10-year-old plantation in southern Illinois, elimination of the fescue sod understory by annual cultivation for 5 years produced trees that were 69% larger in diameter at age 15 than those in untreated areas. In a second plantation, 17 years old at the time of treatment, elimination of the fescue by either cultivation or the establishment of hairy vetch resulted in a 250% increase in diameter growth over the next 3 years. For many slow-growing black walnut plantings, some form of understory vegetation management will be required to meet the goals of short-rotation forestry. North. J. Appl. For. 3:49-51, June 1986.