Regeneration Of Dominant Species Research Articles

Community stability evaluation of riparian forest of the upper reaches of Wenyuhe in Shanxi, China

Aims Stability can comprehensively reflect the structural and functional characteristics of communities. Our objective was to evaluate the stability of 13 riparian forest communities in the upper reaches of Wenyuhe. Methods The evaluation was based on fuzzy comprehensive appraisement theory. In considering integrity stability and structural stability, five indexes were selected which could reflect the current situations of the 13 communities: regeneration of dominant species of the tree layer, total species diversity, Godron index, site quality and protection intensity. The five indexes were measured by 12 factors. Community stability was determined by the means of five subordinate function values. Important findings Most subordinate function values were 0.40–0.60. The stability of two communities, Populus cathayana + Quercus wutaishanica and Pinus tabulaeformis + Betula platyphylla, classified them in the middle of a low-mountain forest succession series. Among middle (high)-mountain forest succession series, stability increased with succession progressing from Populus cathayana forest as the lowest to Picea wilsonii as the highest. In addition, the stability of Picea meyeri + Populus cathayana + Betula platyphylla mixed forest, Larix principis-rupprechtii + Picea meyeri mixed forest and Larix principis-rupprechtii + Picea wilsonii mixed forest were also high, probably in response to disturbance caused by tree canopy or environmental heterogeneity.

Differential species responses to compounded perturbations and implications for landscape heterogeneity and resilience

Disturbance interactions are of great interest in ecology due to their potential to cause non-linear, unexpected results. Increases in disturbance frequency and intensity as a result of climate change increase the need for better conceptual and mechanistic understanding of ecosystem response to compounded perturbations. Impacts on structural elements of ecosystems, such as tree species, are particularly important, as changes in these species’ populations, frequencies, and distributions may influence landscape functioning for extended periods of time. This study investigated the impact of three overlapping disturbances common to western US forests (wind, logging, and fire) on three dominant tree species: Lodgepole pine, Engelmann spruce, and quaking aspen. Ninety-nine study plots were examined across a gradient of interaction severities from a 1997 blowdown, subsequent salvage logging, and a 2002 fire in a Rocky Mountain subalpine forest. Regeneration of dominant species was analyzed in the context of disturbance history and species-specific disturbance response strategies. Results indicated that species are differentially affected by disturbance interactions. Lodgepole pine is highly sensitive to both previous disturbances and their severities, whereas spruce and aspen are insensitive to disturbance history, although both showed higher recruitment levels in three-disturbance environments. Disturbance types, combinations, and specific resilience mechanisms appear to be more important than number of disturbances. Disturbance interactions were not necessarily additive, and in some cases, three disturbances were less severe than two. As a result of long-distance dispersal, aspen seems likely to greatly increase in dominance across the landscape. Species-specific responses are generalized through their individual response strategies, with specialized responses being less resilient to multiple disturbances than generic seed dispersal strategies. Differential responses by structural tree species will likely drive an increase in future landscape heterogeneity and potential decreases in future landscape resilience to fire.

Gap phase regeneration recruitment of mixed conifer-broadleaf forests in Wolong Nature Reserve

Wolong Nature Reserve is the largest reserve for protecting the endangered wild giant panda. Due to historical factors, even in many sections of the core protection area, the forests have been seriously destroyed and natural forests are poorly restored. However, the relative importance of the determinants for recruitment of communities under disturbance is rarely explored. In our study the endogenous and exterior factors in a forest gap that affect the conifer-broad-leaved mixed forest regeneration were investigated near Wuyipeng, one of the observation stations at Wolong, to explore which determinant had the greatest effect on gap regeneration and to discover the recruitment of seedling establishment in forest gaps. With a linear sampling method, environmental factors, gap characteristics and recruitment of new individuals were measured and examined in every forest gap along three sampling lines. Data of environmental factors in the gaps were collected for a Pearson correlation analysis in order to explore the disturbance and preprocessed characteristics of the gaps, using principal component analysis in SPSS. Correlation analysis was applied to further explore the relationship between changes in the gaps and the response of the regenerating seedlings. The results show that a range of natural and human disturbances affected the pattern and characteristics of the forest gaps in this area. The richness in the composition of the seedlings was higher than that of gap makers, but the order of dominance of the composition was different between seedlings and gap makers. The success of dominant species in establishing themselves was affected by different environmental factors. For instance, the establishment of Betula spp. was correlated significantly with topographic factors, while that of Abies faxoniana was affected by soil characteristics and that of Rhododendron spp. correlated significantly with topographic factors and characteristics of gap makers. Moreover, all the biodiversity indices of regenerating seedlings were significantly correlated with environmental principle components mostly reflecting soil properties. From this we can infer that soil characteristics are the most important factors affecting the regeneration of dominant species and seedling diversity under gap disturbances.

Stand Structure and Dynamics in the Temperate Rain Forests of Chiloe Archipelago, Chile

We compared the structure and dynamics of selected stands (c. 0.8 ha) of rain forest in four islands (Alao, Chaulinec, Talcain, and Isla Grande) of the Chiloe Archipelago (c. 42? 30' S). In each forest stand, we tallied and measured the diameter at breast height (d.b.h.) of all canopy trees (>10 cm d.b.h.) within two 20x20 m plots. We also esti- mated the abundance of seedlings and saplings in each plot. The stands were dominated by broad-leaved evergreen trees and had in common the presence of several species of Myrtaceous trees in their canopies. Nothofagus spp. were absent from all but one stand. Structurally, the forests were dominated by different species, although overall species composition was similar. Drimys winteri was dominant in Talc'an and Chaulinec, Aextoxicon punctatum was dominant in Alao, and Amomyrtus luma was dominant in Isla Grande. Laurelia philippiana, A. luma, and Myrceugenia planipes were common to all forests. Nothofagus dombeyi was only present in Talc'an, represented by a few, large emergent trees. The distribution of individuals by d.b.h. classes (every 5 cm, from 10 to >40) showed that the forests of Alao and Chaulinec are dominated by individuals in the smallest d.b.h. class (about 50% of all stems). In the other forests, those individuals made up only 20% of the canopy, and larger trees were more common. Because of the smaller size and relative isolation of the forest patches in Alao and Chaulinec, this pattern might be attributed to invasion of these stands by species from surrounding second- growth forest. Comparison of tree species densities between plots 1 and 2 in each forest revealed that the distribution of young (<15 cm d.b.h.) individuals is highly patchy within a stand for all dominant species. This result is consistent with the hypothesis that the regeneration of dominant species is favoured within tree fall gaps. A broader scale of patchiness, related to the episodic occurrence of stand-devastating disturbances, could explain the persistence of Nothofagus dombeyi populations in Talc'an. Recruitment of seedlings and saplings in the forests studied was positively correlated with the abundance of each species in the canopy. Accordingly, dominance will be maintained in these forests in the absence of stand- disrupting disturbances.

Reciprocal Replacement and the Maintenance of Codominance in a Beech-Maple Forest

Regeneration of dominant species in an undisturbed beech-maple forest in Michigan, USA, was studied. Spatial distributions of saplings of beech and maple were related to influence by canopy trees of these species. Some factor effecting a differential mortality of young individuals of the two species was indicated and it is suggested that this factor is related to species of nearby canopy trees. This cause of mortality appeared to act on individuals between one and four meters in height. Assuming that replacement of fallen trees in such a forest is primarily by advance reproduction in the form of such seedlings and saplings as studied here, it appears that individuals of either dominant species will tend to be replaced by individuals of the other species in a pattern of reciprocal replacement. This, then, is a possible mechanism for indefinite maintenance of codominance in a climax forest.