The spatiotemporal dynamics of a primary succession

Abstract

Summary1. Conceptual models of ecosystem development commonly predict a phase of initial colonization characterized by the nucleation, growth and coalescence of discrete patches of pioneer plants. Spatiotemporal dynamics during subsequent development may follow one of three different models: the classical model, in which initially discrete patches of competitive dominant (secondary) colonists coalesce to form a homogeneous cover; the patch dynamics model, in which renewal mechanisms such as disturbance create a shifting mosaic of patches at different stages; and the geoecological model, in which the vegetation gradually differentiates along edaphic gradients related to the underlying physical template. 2. These models of spatiotemporal dynamics were tested using vegetation and soil data from an 850-year chronosequence, comprised of seven lava flows on Mt Hekla, Iceland. The scale and intensity of spatial pattern were quantified on each flow using spatial analyses (mean-variance ratios, quadrat variance techniques and indices of autocorrelation). Changes in spatial pattern with increasing terrain age were compared with predicted trajectories, in order to identify which of the models of spatiotemporal dynamics was most consistent with the observations. 3. The early stages of ecosystem development were characterized by colonization of the pioneer species, especially Racomitrium mosses, in discrete patches ('Pioneer colonization stage', < 20 years), which then grew laterally and coalesced to form a continuous, homogeneous carpet ('Pioneer expansion stage', 20-100 years). Later in the sequence, higher plants established in discrete patches within this pioneer matrix ('Higher plant colonization stage', 100 -600 years). Over time, heterogeneity re-emerged at a larger spatial scale as the vegetation differentiated according to topographic variations in the underlying substrate ('Differentiation stage', > 600 years). 4. Synthesis . The spatiotemporal dynamics observed in the early stages of this succession were consistent with a model of pioneer nucleation in micro-scale safe sites, followed by growth, coalescence and eventual fragmentation of pioneer patches. The spatial patterns which emerged later in development support the geoecological model, with spatial differentiation of vegetation related to meso-scale substrate topography. The findings provide insight on how vegetation patterns emerge at different stages of ecosystem development in response to differing scales of heterogeneity in the underlying physical environment.

Regional Variation in Successional Trajectories and Rates of Vegetation Change on Glacier Forelands in South-Central Norway

“…Subsequent divergence of vegetation occurs with increasing distance from the glacier due to topographic variation (Cutler et al, 2008), decreasing intensity and frequency of disturbance, and generally more favorable conditions for establishment despite greater competition. The fact that later colonizing species are more sensitive to environmental factors may mean that their narrower niche width results in increasing heterogeneity (Leps and Rejmanek, 1991).…”

Accumulation of nitrogen and organic matter during primary succession of &lt;i&gt;Leymus arenarius&lt;/i&gt; dunes on the volcanic island Surtsey, Iceland

“…Cutler et al, 2008;del Moral et al, 2009;Cutler 2011;Garibotti et al, 2011). In patchy environments, positive feedback mechanisms can contribute to resource aggradation (cf.…”

Infiltration and water retention of biological soil crusts on reclaimed soils of former open-cast lignite mining sites in Brandenburg, north-east Germany

“…Hence, in the initial stage of the ecosystem development, the post-mining sites are open areas without or with a low cover of higher vegetation (Wiegleb and Felinks, 2001). In this context, first cryptogamic pioneers, which are able to colonize the soil surface under such extreme conditions without human support, played a key role in the soil development and niche formation for higher plants (Bowker et al, 2014;Cutler et al, 2008). Therefore, green algae, cyanobacteria and bacteria (Veste, 2005) promoted cross-linking of mineral particles, form biological soil crusts and accumulate organic biomass (Büdel, 2003;Dümig et al, 2014).…”