Vegetation patterns 25 years after the eruption of Mount St. Helens, Washington, USA

Abstract

In 2004, we surveyed the vegetation on Mount St. Helens to document changes since 1992. We asked how communities differentiate and if they develop predictable relationships with local environments. We sought evidence from links between species and environment and changes in community structure in 271 250-m(2) plots. The habitats of the seven community types (CTs) overlapped broadly. Ordination methods demonstrated weak correlations among species distributions and location, elevation, and surface variables. Comparisons to 1992 by habitat demonstrated a large increase in plant cover and substantial development of vegetation structure. Pioneer species declined while mosses increased proportionately leading to more pronounced dominance hierarchies in most habitats. In Lupinus colonies, dominance declined, and diversity increased due to the increased abundance of formerly rare species. On once barren sites, dominance increased, but diversity changed slightly, which suggested the incipient development of competitive hierarchies. Weak correlations between vegetation and the environment suggested that initially stochastic establishment patterns had not yet been erased by deterministic factors. A vegetation mosaic that is loosely controlled by environmental factors may produce different successional trajectories that lead to alternative stable communities in similar habitats. This result has implications for restoration planning.

Primary Succession along an Elevation Gradient 15 Years after the Eruption of Mount Pinatubo, Luzon, Philippines

“…Landscape effects such as elevation and geographic position were highly associated with vegetation change, as they were on Mount St. Helens (del Moral and Lacher 2005). Despite these similarities, the speed of vegetation recovery on Mount Pinatubo is noteworthy, with dense cover of species occurring in less than 15 yr.…”

“…del Moral and Lacher 2005). If these river systems on Mount Pinatubo follow patterns observed on other volcanoes, species diversity eventually will increase dramatically (e.g., Whittaker and Fernández Palacios 2007).…”

“…Our intent was to create an inventory of the taxa and determine how they have assembled to provide a baseline for meaningful studies of succession. Therefore, we sampled 63 plots among the eight sites (Figure 1), using 12 quadrats per plot following del Moral and Lacher (2005). Whenever possible, we used circular 250 m 2 plots as follows: from the center of the plot, three 1 m 2 quadrats were arrayed at 2 m intervals along radii arrayed along the cardinal directions.…”

Spatial factors affecting primary succession on the Muddy River Lahar, Mount St. Helens, Washington

“…), del Moral and Lacher (2005) used canonical correspondence analysis (CCA) and found only weak explanatory variables. We reanalyzed their data with RDA and obtained much improved results (RDA = 28.7% of the species variation, CCA = 13.0%).…”

Progressive Succession at Vegetation of Gölardı (Terme/Samsun) Natural Protected Area

“…As river deltaic plains [4], riparian floodplains [5], salt marshes [6] freshwater marshes [7], coastal or inland sand dunes [8,9], volcanic erupted areas [10] and deglaciation areas (edge of retreating glacier; glacier forelands) [11] are offer an excellent opportunity to study processes of primary succession. However deltaic plains of big rivers belong to the most variable and least predictable environments on earth.…”