Legacies of forest harvesting on plant diversity and plant community composition in temperate deciduous forest
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Abstract Aims To conserve forest natural heritage, sustainable forest harvesting requires the recovery of plant diversity and ecosystem functions following management. There is a need to clarify the temporal dynamics of plant diversity following harvesting, for both even‐aged and uneven‐aged silvicultural systems. To achieve this goal, the temporal dynamics of plant diversity in the herb layer were measured in unmanaged forests (control) and along a chronosequence (<5 years, 15 years and 30 years after harvesting) for even‐aged and uneven‐aged managed forests. Location Hardwood forest of southern Quebec, Canada. Methods Plant diversity, plant community composition and ecosystem functioning were investigated using metrics exploring richness, evenness and disparity diversity components, and included two scales of diversity partitioning (alpha and beta). Shrub–canopy layer, forest tree species composition and structure, and total forest basal area were also measured. Results In both uneven‐aged and even‐aged managed forest stands, we found: (a) a substantial decrease in mean plant phylogenetic diversity compared with unmanaged forest, even 30 years after harvesting (i.e., decrease of 16% and 22%, respectively); and (b) lowest plant alpha‐diversity in the herb layer 15 years after harvesting. Modification of community composition based upon dissimilarity (beta‐diversity) metrics demonstrated more numerous effects of even‐aged management than uneven‐aged management. For forest composition and structure, plant community and plant traits, dissimilarity relative to the unmanaged control was highest 5 years after even‐aged management. Trait‐based communities were more similar to unmanaged forest at the intermediate levels of forest density (i.e., ~20 m 2 /ha) that were found 5 years after uneven‐aged management. Conclusions Forest management clearly affected diversity, community composition and ecosystem functions along the chronosequence, highlighting the strongest effects of more intensive management (i.e., even‐aged) and the need to improve the sustainability of forest management.Keywords:
Chronosequence
Basal area
Temperate forest
Temperate deciduous forest
Temperate rainforest
Plant Diversity
Old-growth forest
Understory
One of the most influential tenets of forest management today is that old-growth forest stands are generally more structurally complex than comparable younger stands. To test this, a chronosequence of 10 stem-mapped Douglas-fir-dominated mixed-conifer stands in the central western Cascades of Oregon were structurally characterized. Old-growth condition was determined using the index of old-growth (Iog); structural complexity was quantified with the structural complexity index (SCI); and spatial tree distribution patterns were evaluated with Ripley’s K function. Old-growth condition was positively related to structural complexity, but some stands with typical old-growth characteristics exhibited structures no more complex than those of transitional and mature stands. Analysis of SCI-patch types indicates that variability in structural components shifts from tree-to-tree variation to patch-to-patch variation in some old-growth stands. No consistent spatial tree distribution pattern was detected using Ripley’s K. These results suggest that managing forests to promote old-growth structural components without respect to spatial distribution, residual tree densities, tree species composition, or disturbance regime could lead to lower live-tree structural complexity.
Chronosequence
Tree (set theory)
Old-growth forest
Structural complexity
Basal area
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Chronosequence
Old-growth forest
Structural complexity
Tree (set theory)
Basal area
Stand development
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Citations (84)
The plant diversity of Larix principis rupprechtii community and Picea ssp.community and their ecotone are studied using numerical method. The results show: the plant diversity index of communities decrease along with the increasing of elevation gradient; the evenness of tree stratum is lower in the high and low elevation than in the middle, but those of shrub stratum and herb are not obvious. The plant diversity of community's ecotone increase obviously. The change pattern of diversity show different features in various growth type. The β diversity of communities show relative complex feature. It can be divided three parts.There are various features in each part. It show the change characters of plant diversity of communities and their ecotone.
Ecotone
Stratum
Plant Diversity
Diversity index
Elevation (ballistics)
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Chronosequence
Secondary forest
Old-growth forest
Basal area
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One of the key issues facing forest resource planners is the conservation and recruitment of old-growth characteristics in managed forests. The paucity of long-term data sets in many regions has limited our ability to project the temporal patterns of structural development in second-growth forests. Age-based thresholds have been employed in some jurisdictions, but these lack flexibility and are arbitrary in nature. Here we conduct a chronosequence study consisting of second-growth and old-growth stands in the coastal forests of Vancouver Island, British Columbia, to identify structural attributes that are suitable for quantifying and monitoring the progressive development of old-growth characteristics. The following structural attributes were identified and evaluated in the chronosequence analysis: volume and density of large live stems, standard deviation of stem DBH, density of large-diameter snags, volume of woody debris, and understory vegetation cover. The rate at which old-growth structural characteristics developed in second-growth stands varied considerably, with the earliest reaching levels observed in old-growth stands within 112 years, while most requiring 200 to greater than 250 years. The use of quantifiable measures of old-growth structure will help forest managers plan for the continued protection and recruitment of old-growth structure within managed forest landscapes.
Chronosequence
Understory
Coarse Woody Debris
Old-growth forest
Stand development
Silviculture
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Chronosequence
Bryophyte
Understory
Old-growth forest
Black spruce
Secondary forest
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Patterns of structure and diversity are described from a chronosequence established in the Barro Colorado Nature Monument, Panama. The BCNM is a mosaic of sec- ondary forests reflecting two centuries of agriculture and the establishment of forest preserves. Structure and composition were studied in 10 stands: two each had been farmed or pastured 20, 40, 70, and 100 yr previously; two old-growth stands likely never had been farmed intensively. Data from BCNM are compared with those published by Saldarriaga et al. (1988) from an oligotrophic site on the upper Rio Negro, Venezuela. Changes in stand structure across the BCNM chronosequence are consistent with the four phase model of secondary succession (establishment, thinning, transition, steady state). Growth is rapid and stand basal area reaches old- growth values within 70 - 100 yr. In contrast, growth at Rio Negro is slow; only 2/3 of the total basal area characteristic of old-growth stands was established at 80 yr. Sapling densities in both sites decline with forest age, increasing somewhat in older stands of BCNM but remaining low at Rio Negro. In neither site does tree diversity increase asymptotically toward a maximum in old-growth forest or peak at intermediate stand ages. These data suggest that tropical forest successional pat- terns may not be influenced strongly by the dominance of a few pioneer species as often seems to be the case in temperate forest successions, but reflect the availability of a diverse, easily dispersed regeneration pool.
Chronosequence
Dominance (genetics)
Basal area
Old-growth forest
Panama
Secondary forest
Forest structure
Temperate forest
Temperate rainforest
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Changes in physiognomy, species composition and structure, and dispersal mechanisms of canopy and subcanopy plant assemblages were investigated along a chronosequence of three ages: 12, 20, and 50+ years old (=old-growth), three replications in each, in an Atlantic Forest landscape in Northeastern Brazil. Our objective was to investigate whether there is floristic and structural convergence along secondary succession. There were significant differences between secondary and old-growth forests in density and basal area only for the subcanopy. Differences in density between forest ages were noted when the assemblage was analyzed per diameter and height classes. Richness of canopy species of both secondary ages differed from those of old-growth forests. Some dominant species in the canopy of secondary forests showed a significant decrease in density with increasing age, which indicates an ongoing process of floristic changes. The low level of shared species between secondary and old-growth forests supports the idea that species composition is one of the last components to recover during successional process. Zoochory was the most important dispersal guild in species percentage and number, irrespective of stand age. Although regenerating areas can take alternative pathways, our results indicate that secondary Atlantic Forest sites have a high potential for natural regeneration. This recovery is recorded as a physiognomic convergence of the canopy layer in as little as 12 years, and progressive introductions of later successional species into the plant assemblage that lead to convergence in terms of the diversity and richness of the subcanopy and of dispersal guilds just 20 years after abandonment.
Chronosequence
Secondary succession
Secondary forest
Old-growth forest
Guild
Basal area
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Chronosequence
Coarse Woody Debris
Old-growth forest
Secondary forest
Temperate rainforest
Clearcutting
Temperate forest
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Citations (129)
Chronosequence
Secondary succession
Secondary forest
Clearcutting
Old-growth forest
Basal area
Stand development
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Citations (19)