The composition and diversity of natural regeneration of tree species in gaps under different intensities of forest disturbance

The positive ecological interaction between gap formation and natural regeneration has been examined but little research has been carried out on the effects of gaps on natural regeneration in forests under different intensities of disturbance.This study evaluates the composition,diversity,regeneration density and abundance of natural regeneration of tree species in gaps in undisturbed,intermittently disturbed,and disturbed forest sites.Bia Tano Forest Reserve in Ghana was the study area and three gaps each were selected in the three forest site categories.Ten circular subsampling areas of 1 m2 were delineated at 2 m spacing along north,south,east,and west transects within individual gaps.Data on natural regeneration 350 cm height were gathered.The results show that the intensity of disturbance was disproportional to gap size.Species diversity differed significantly between undisturbed and disturbed sites and,also between intermittently disturbed and disturbed sites for Simpson's(1-D),Equitability(J),and Berger-Parker(B-P) indices.However,there was no significant difference among forest sites for Shannon diversity(H) and Margalef richness(MI) indices.Tree species composition on the sites differed.Regeneration density on the disturbed site was significantly higher than on the two other sites.Greater abundance and density of shade-dependent species on all sites identified them as opportunistic replacements of gap-dependent pioneers.Pioneer species giving way to shade tolerant species is a natural process,thus make them worst variant in gap regeneration.     

火干扰对天然红松林结构和演替过程的影响

Investigations on charcoal in the soil, fire-scarred trees, stand composition, forest structure as well as regeneration status were carried out in the natural broad-leaved/Korean pine (Pinus koraiensis) forest after fire disturbance at Liangshui Nature Reserve on the mid-north of Xiaoxing‘an Mountains from 1990 to 1992, and the ecological effects of fire disturbance on the formation and succession of this kind of forest were analyzed according to the survey results. The average depth of charcoal in the soil was related to the timing of the fire. According to the characteristic of fire-scarred trees, the dynamic map of the fire behavior was drawn onto the topographic map. It showed that the dimension and extent of the fire disturbance was closely related with site conditions. Fire disturbance only led to a significant difference in stand composition and diameter class structurefor the stands at different locations, rather than completely destroying the forest. After fire disturbance, the horizontal community structure was a mosaic of different patches, which were made up of different deciduous species or different sizes of Korean pines, and the succession trend of each patch was also different. In the sites with the heavy fire disturbance, the intolerant hardwood species were dominant, and there were a large number of regenerative Korean pine saplings under the canopy. In the moderate -disturbed sites, the tolerant hardwood species were dominant, and a small number of large size Korean pines still survived. In the light-disturbed sites, large size Korean pines were dominant.     

Structure changes and succession dynamic of the natural secondary forest after severe fire interference

The structure and dynamic succession law of natural secondary forest after severe fire interference in recent 20 years were studied by adopting the method of deducing time series from the spatial sequence of vegetation in Heihe region, Heilongjiang, China. Two typical and widely distributed forest types in the study area, namely forest type A and forest type B, were selected as study subjects. Forest type A is pure broadleaf forest or broadleaf mixed forest mainly composing of superior Betula platyphylla and Populus davidiana in the area with gradient <25°, while forest type B is pure forest or mixed forest composing of superior Quercus mongolica and Betula davurica in the area with gradient >25°. Species richness, vegetation coverage, important value, and similarity index of community in different layers (Herb, shrub, small tree, and arbor layers) were investigated and analyzed for the two typical forests. The results show that after fire interference, the species richness and coverage in each layer in forest type A were higher than that in forest type B. Both for forest type A and B, with elapse of post-fire years, the species richness and coverage of herbs and shrubs showed a decline tendency, while those of arbor layer present a rising tendency. Through comparison of the important values of species in each layer and analysis of community structure changes, the dynamic process of post-fire vegetation succession for forest type A and B was separately determined. Post-fire 80 years' succession tendency of forest type A is B. platyphylla and Larix gmelinii mixed forest. Its shrub layer is mainly composed of Corylus heterophylla and Vaccinium uliginosum, and herb layer is dominated by Carex tristachya, Athyrium multidentatum, and Pyrola incarnate; whereas, the post-fire 80 years' succession of forest type B is Q. mongolica and B. davurica mixed forest. Its shrub layer is mainly composed of lespedeza bicolar and corylus heterophylla and herb layer is dominated by Carex tristachya, Asparagus densiflorus, and Hemerocallis minor.     

Recovery of species diversity after disturbance of broad-leaved Korean pine mixed forest in Changbai Mountain

IntroductionMorerecently,Thehumanl1asshowedagreatinterestli1studiesonpatternsofchangesinspeciesdiversityduriI1gprocessofsuccession,ThedistuIbal1ceofI1umanactivitiesornaturedisastershasagreatbopactonspeciesdiversity.PlantsPeciescomprisingapost-disturbancecommunityderhefromavarietyofsources-winddispersedseed,buriedpropagulesandresproutingsurvivorsl1'l.TheirulthatecontributiontotheserialflorarenectSacomplexinteractionofinitialabundance,includingdistuthanceintCnsity,proPagatCavailability,andc…     

Temperate forest development during secondary succession: effects of soil,dominant species and management

With the increase in abandoned agricultural lands in Western Europe, knowledge on the successional pathways of newly developing forests becomes urgent. We evaluated the effect of time, soil type and dominant species type (shade tolerant or intolerant) on the development during succession of three stand attributes: above-ground biomass, stand height (HT) and stem density (SD). Additionally, we compared above-ground biomass (AGB) in natural and planted forests, using ten chronosequences (8 from the literature and 2 from this study). Both AGB and HT increased over time, whereas SD decreased. HT, SD and AGB differed among species types. For example, birch had greater HT than alder, willow and ash at a similar age and had higher SD than pine and oak at a similar age. However, birch showed lower AGB than pine. HT and AGB differed among soil types. They were higher in rich soil than in poor soils. Comparative analysis between chronosequences showed an effect of the regeneration method (natural regeneration vs plantation) on above-ground biomass. Planted sites had higher AGB than natural regeneration. Time, soil type, species and regeneration method influenced the mechanism of stand responses during secondary succession. These characteristics could be used to clarify the heterogeneity and potential productivity of such spontaneously growing temperate forest ecosystems.     

Long-term effects of succession,climate change and insect disturbance on oak-pine forest composition in the U.S. Central Hardwood Region

European Journal of Forest Research - Oak-pine forests in the U.S. Central Hardwood Forests are recovering from exploitative harvesting and clearing in the early twentieth century and are...     

Vegetation diversity and vertical structure as indicators of forest disturbance

Plant species composition and vertical structure of oak-mixed Atlantic woodlands differing on disturbance regime were studied in the Basque Country, northern Spain. Four different disturbance groups were considered depending on the time since last thinning and the presence/absence of grazers. Plant species cover varied among disturbance groups for 17 out of the total 47 species present in the study area. In general, disturbance by clear-cutting favoured the cover of Betula alba, Castanea sativa and Quercus robur. The shrub species most affected by disturbance were heathers. Among these, the most drastic effect was found for Calluna vulgaris, Daboecia cantabrica and Erica vagans which disappeared in those woodlands subjected to grazing. Several nemoral species, such as Vaccinium myrtillus, Blechnum spicant and Lamiastrum galeobdolon, were absent in these same grazed forests. By contrast, generalist species, such as Ruscus aculeatus, Geranium robertianum and Veronica officinalis, were mostly present in the grazed woodlands.Diversity was measured as Species Richness as well as with the Shannon’s and Simpson’s indices. Plant species richness did not vary with disturbance treatment, however, it was highest for trees and shrubs at those woodlands in an advanced stage of regeneration, and for herbs in the lowest and highest disturbance groups. Besides, only the third vertical layer (2.5–10 m) was affected by disturbance treatment. Simpson’s was the best index to explain the observed differences in the structure of woodlands subjected to unalike levels of disturbance. Species diversity was highest in woodlands with lowest disturbance or in an advanced state of regeneration. Woodlands with lowest disturbance had the highest diversity of trees and those woodlands in an advanced state of regeneration showed the highest diversity of shrub species. Regarding vertical structure, diversity was mostly affected in the intermediate layer (2.5–10 m), with highest values found in woodlands at the lowest disturbance group, i.e. at least 100 years of no disturbance. Two indices of evenness, i.e. Pielou’s and Simpson’s were also calculated in this study. Results here presented suggest that plant species composition, percent cover of individual plant species, and the Simpson’s diversity index (applied considering the different growth-forms and vertical layers) are suitable and complementary indices to evaluate disturbance at the studied woodlands.     

天然林采伐与生物多样性保护

本文谈了保护生物多样性的意义，生物多样性丧失的原因，森林采伐对生态环境的影响及生物多样性保护的措施。     

Tree species diversity in relation to environmental variables and disturbance gradients in a northeastern forest in Bangladesh

Biodiversity has become an issue of global attention because of growing awareness of its importance and its rapid depletion worldwide. Diversity of tree species in relation to environmental and disturbance gradients was examined in three managed forests. Trees were randomly sampled in a survey of 75 circular plots(radius = 13 m)with 5 subplots(radius = 1 m). Generalized linear model analysis was used with a Poisson distribution log link function to understand the effects of variables(organic matter, organic carbon, nitrogen, potassium, pH, elevation and disturbance) on tree species richness. Canonical correspondence analysis was used to explore ecological relationships among plots. Our result found that the stand characteristics was an important influencing factor in the three forests. Our result showed that the variables had a highly positive influence on tree species richness in the three forests. In ordination, the selected variables governed the richness of tree species. Our study can help identify the most important factors that drive tree species richness in the three managed forests in Bangladesh and in similar ecosystems and inform forest management decisions for conservation according to ecological importance.