Establishment and spatial associations of recruits in meadow gaps

Questions What is the spatio-temporal dynamics of recruit (seedlings and vegetative sprouts) establishment in meadow gaps? What processes prevail during recruit establishment? At what spatio-temporal scales do they operate? Location A wet meadow in South Bohemia, a region of the Czech Republic. Methods We studied spatio-temporal dynamics in pattern of recruits (seedlings and vegetative sprouts) to characterize development and underlying ecological processes during gap colonization. We established four types of artificial gaps laid out in ten replicated blocks. To distinguish the effects of generative vs vegetative reproduction we used gaps with sterilized and non-sterilized soil (manipulating the seed bank), and manipulated the possibility of clonal spread by inserting mesh or felting along the borders of the gaps. Results The majority of recruits appeared during July and August. Recruits were surrounded by empty spaces of 59mm, and formed clumps of 20mm or more. Clumping of even-aged seedlings and a lower number of vegetative recruits were observed in the gaps with non-sterilized soil. Overall, clonal spread was limited to the gap borders, being far less common than recruit establishment from seeds. The recruits emerged preferentially close to the gap centre where the temperature was highest as was the red to farred ratio (R:FR). However, during the season, the majority of late recruits were observed in the southern, coolest parts of the gaps, reflecting the increasing importance of the facilitative effect of the surrounding vegetation. Conclusions Gaps were colonized predominantly from seeds; vegetative propagation was very slow and appeared at the end of the season. The presence of a seed bank enabled earlier gap colonization; the effect of seed rain became increasingly important during the season. The recruits were clumped, which further supports environmentally driven establishment, although other factors (e.g. facilitation) cannot be excluded. For the shortest distances, recruits were absent close neighbours due to the strongest competition. We therefore suggest that there was a spatial continuum between competition and facilitative effects among individual recruits.