Colonization of experimentally created gaps along an alpine successional gradient

Abstract

The colonization of artificially created gaps was analyzed along an alpine successional gradient from pioneer to early, late, and old successional stages. The presence/absence of species and the abundances of seedlings and adults in the gaps were recorded and compared with those of the surrounding areas. We hypothesized that in the older successional stages, the gaps were likely to be colonized by clonal ingrowth of the surrounding species. In the younger stages, we expected to find a high presence of seedlings and adults recruited by seeds. Micro-succession in the gaps occurred at each successional stage, with all life forms among the colonizers. The abundance of seedlings was significantly higher in the gaps compared with the surrounding area. At the early and late successional stages, the surrounding areas provided safe sites for seedling establishment, with the abundance of adults recruited by seeds higher at the gap edges than in the gap centers. We can confirm the first hypothesis of a higher clonal ingrowth in the old successional stage. Clonal ingrowth also occurred in the younger successional stages. Despite the lower species richness in the gaps, a positive correlation was found between gap and surrounding species frequencies, which were the highest in the pioneer and the lowest in the old successional stage. We conclude that gaps are relevant for seedling recruitment along the entire primary succession gradient. New species invasions from greater distances were not observed in the gaps. The dominant species on each site were identified to be successful gap colonizers.

Establishment and spatial associations of recruits in meadow gaps

“…Vegetative ingrowth was therefore expected to contribute significantly to gap colonization. However, we documented vegetative ingrowth only later in the season, and it was always less common than the generative regeneration, which is consistent with other studies (Bullock et al 1995;Cichini et al 2011). Furthermore, clonal spread was confined mostly to the borders, and thus limited to short distances.…”

Root traits predict decomposition across a landscape‐scale grazing experiment

“…The contribution of plant species identity to goodness of fit for our mixed models was estimated by subtracting the goodness‐of‐fit r 2 for a model without species from the model with species. Statistical significance amongst the different species was obtained through formulating contrast statements within the same model structure, whilst controlling for multiple contrasts (see Hothorn et al ., ; Cichini et al ., ).…”

“…New Phytologist model without species from the model with species. Statistical significance amongst the different species was obtained through formulating contrast statements within the same model structure, whilst controlling for multiple contrasts (see Hothorn et al, 2008;Cichini et al, 2011).…”

Correspondence of seed traits with niche position in glacier foreland succession

“…However, several studies reported of a general low seedling recruitment at early successional stages of glacier forelands (Marcante et al 2009b;Niederfriniger Schlag and Erschbamer 2000;Stöcklin and Bäumler 1996), but more experimental studies are needed that explicitly address the relationship of seed mass, germination and survival of glacier foreland species. Limitation of seedling recruitment also plays a role in later successional stages, but abundant litter Table 1 and high canopy cover are assumed to be the main causes of low recruitment at these sites (Cichini et al 2011;Marcante et al 2009b). Thus, heavier seeds should also be advantageous for seedling recruitment in later successional stages as reported from other communities with prevailing competitive grasses (Jacobsson and Eriksson 2000).…”