Effects of Fine-Scale Disturbances on the Demography and Population Dynamics of the Clonal Moss Hylocomium splendens

• Published in: The Journal of ecology 2001-06, Vol.89 (3), p.395-405
• Main Authors: Rydgren, Knut, de Kroon, Hans, Økland, Rune H., van Groenendael, Jan
• Format: Article
• Language: English
• Subjects: boreal forest; Boreal forests; Botany; Bryophytes; clonal plants; Demography; Ecological disturbance; Ecology; elasticity; fine‐scale disturbance; Forest ecology; Forest regeneration; Forests; Human ecology; Hylocomium splendens; life table response experiment; Mosses; Nature Conservation and Plant Ecology; Natuurbeheer en Plantenecologie; Norway; periodic matrix model; Plant Ecology and Nature Conservation; Plant growth; Plantenecologie en Natuurbeheer; Population ecology; Population growth; Population growth rate; WIMEK
• ISSN: 0022-0477; 1365-2745
• DOI: 10.1046/j.1365-2745.2001.00552.x

1 The boreal forest is subject to disturbance but the effects on population dynamics are poorly understood. We investigated how a prominent species of the forest floor, the clonal moss Hylocomium splendens, responded to different types of fine-scale disturbance. 2 Canopy gap formation was simulated in H. splendens populations by removing 50% of the bryophyte layer (Removal treatment) and herbivory by clipping all of its growing points (Clipped treatment). Demographic parameters and population dynamics were compared with an unmanipulated reference population (Ref). 3 Both types of disturbance caused a significant decrease in mean segment size (particularly following clipping) and an increase in branching rates. Branching rates in the Removal population were enhanced at all architectural opportunities for enhanced branching, but only the Clipped segments themselves were affected during the 2 years following disturbance. 4 The population effects of disturbance were analysed by a periodic matrix model, with 3-year as the period, followed by elasticity analysis. The Ref population was approximately stable (growth rate, λ = 1.012), with the survival of mature segments making an overwhelming contribution to its growth rate. The higher λ (1.740) in the Removal population was associated with higher elasticities of branching. Clipping reduced λ to 0.841 by blocking segment survival, although regeneration of new growing points on the remnant main shoot axis after 1 year, and its subsequent maturation in the next year, then made a major contribution. 5 Life table response experiment analyses revealed that almost all demographic processes including branching and the survival of mature segments contributed to the increased λ in Removal treatment. The relatively small decrease in λ following clipping was mainly due to the absence of mature segment survival, being almost balanced by the pulse of regeneration of growing points the year after disturbance. 6 We conclude that H. splendens populations show a good ability to recover from common types of disturbances in their environment. The general mechanisms behind the responses are discussed.