19 research outputs found
Legacy of pre-disturbance spatial pattern determines early structural diversity following severe disturbance in mountain spruce forests in Czech Republic
Background
Severe canopy-removing disturbances are native to many temperate forests and radically
alter stand structure, but biotic legacies (surviving elements or patterns) can lend continuity
to ecosystem function after such events. Poorly understood is the degree to which the structural
complexity of an old-growth forest carries over to the next stand. We asked how predisturbance
spatial pattern acts as a legacy to influence post-disturbance stand structure,
and how this legacy influences the structural diversity within the early-seral stand.
Methods
Two stem-mapped one-hectare forest plots in the Czech Republic experienced a severe
bark beetle outbreak, thus providing before-and-after data on spatial patterns in live and
dead trees, crown projections, down logs, and herb cover.
Results
Post-disturbance stands were dominated by an advanced regeneration layer present before
the disturbance. Both major species, Norway spruce (Picea abies) and rowan (Sorbus
aucuparia), were strongly self-aggregated and also clustered to former canopy trees, predisturbance
snags, stumps and logs, suggesting positive overstory to understory neighbourhood
effects. Thus, although the disturbance dramatically reduced the stand’s height
profile with ~100% mortality of the canopy layer, the spatial structure of post-disturbance
stands still closely reflected the pre-disturbance structure. The former upper tree layer influenced
advanced regeneration through microsite and light limitation. Under formerly dense
canopies, regeneration density was high but relatively homogeneous in height; while in former small gaps with greater herb cover, regeneration density was lower but with greater
heterogeneity in heights
Storm disturbance in forest ecosystems in Estonia
Several storms have damaged Estonian forests in recent years. Individual tree properties such as diameter at breast height (dbh) and tree height affect the type of damage (stem breakage or uprooting) and influence the formation of postdisturbance forest structure. The aim of this study was to analyse how the risk of uprooting and stem breakage varied with respect to tree diameter, height, species and soil conditions. The data were collected from plots located in storm-damaged forests in eastern Estonia. The probability of uprooting increased with increasing diameter for Norway spruce, European aspen and birch. Black alders with large stem diameter usually suffered stem breakage. A high proportion of stem breakage also occurred among small Norway spruce in the understorey, probably damaged by falling canopy trees. Soil conditions influenced the ratio between uprooting and stem breakage of Norway spruce, the ratio being much higher on gley soils than on podzolic soils. The root plate size of Norway spruce was only slightly correlated with dbh, tree height and volum