Intermediate Successional Stages Research Articles

Soil food web assembly and vegetation development in a glacial chronosequence in Iceland

Worldwide human activities threaten soil quality in terms of the soil’s ability to deliver ecosystem services. This ongoing process of land degradation asks for effective strategies of soil protection. In this context, it is important to understand processes that build up and regenerate soil.The present study investigated how the soil ecosystem, including soil organisms, vegetation and soil ecological processes, develops during the process of soil formation in a chronosequence in a glacier forefield in Iceland. We hypothesised that along successional age we see increases in nutrient content, vegetation cover, and plant species richness linked to increases in soil food webs biomass and complexity.In line with our expectations all measured pools of carbon and nitrogen, and vegetation cover increased with age in the glacial forefield, but plant species richness levelled off after 30 years. Soil organisms generally increased in biomass with successional age, although some of the groups of soil organisms peaked at an intermediate successional stage. In contrast to our expectations, some of the calculated food web complexity metrics such as the number of trophic groups and trophic chain length did not increase linearly, but showed an intermediate peak or even decreased with successional age. However, plant cover and pools of carbon and nitrogen still increased after 120 years. From these results we conclude that soil ecosystem development takes more than a century under Icelandic climatic conditions to fully develop in terms of vegetation succession, food web structure and biogeochemical cycling.

Vegetation patterns along agricultural land abandonment in the Balkans

AbstractQuestionWhat are the woody vegetation encroachment patterns after agricultural land abandonment? Focusing on two parameters, woody plant species richness and vertical vegetation heterogeneity (number of different vegetation strata and their relative cover) we investigated: (a) the effect of forest encroachment following land abandonment; (b) the comparative importance of forest encroachment vis‐a‐vis topographic and climatic parameters, and finally; (c) the ecological importance of eight land‐cover types encountered in abandoned agricultural landscapes.LocationThe Balkan Peninsula (Albania, Bulgaria, Croatia, Greece).MethodsWe set up a standard methodology for 1 × 1 km site selection (70 sites) and data collection within 497 plots, along a well‐defined forest encroachment gradient that reflects land abandonment in terms of woody vegetation cover.ResultsThe pattern that emerged was neither clear nor common for the Balkan region, regarding the effect of forest encroachment on the woody plant species richness in young forests, formed from 20 to 50 years after land abandonment. However, at national level, species diversity was significantly affected by elevation (Bulgaria and Croatia) and temperature (Croatia), with lower and cooler areas being richer. Elevation was of great importance in determining vertical vegetation heterogeneity. Woodlots, broad‐leaved forests, hedges and shrublands held the highest woody species richness in comparison to the more open land‐cover types, and vertical vegetation heterogeneity was higher in open forests and woodlots.ConclusionsWe expect the expansion of broad‐leaved forests following land abandonment to enhance woody species richness. However, other land‐cover types that were found to be important for woody plants should be maintained. As woody plants play a key role in supporting overall biodiversity, by providing suitable habitat for many species, we consider the preservation of a mosaic of patches of different land‐cover types essential for the conservation of both plant and animal species diversity. Young forests should be preserved at intermediate stages of succession, through intermediate disturbance activities, including medium intensity grazing and the enhancement of wild ungulates.

Using LiDAR waveform metrics to describe and identify successional stages of tropical dry forests

During the past several decades, full-waveform LiDAR has been widely employed to estimate biophysical and biochemical attributes of forests. Many LiDAR metrics have been proposed for distinguishing tree species. However, little work has been dedicated to identifying tools for accurately classifying forests in different levels of ecological succession. This paper explores the potential of full-waveform LiDAR metrics in the identification and classification of tropical dry forests (TDFs) at three levels of ecological succession: early, intermediate, and late. Based on the effective LiDAR waveform and the cumulative return energy curve from the Laser Vegetation Imaging Sensor (LVIS), we derived a total of 21 LiDAR metrics which can be classified into point-, line-, area-, or shape-based groups. We further evaluated their ability in differentiating TDF succession using multiple comparison analysis (Duncan method and Tamhane’s T2 method) and ISODATA clustering. Our results showed that the response of LiDAR energy could well reflect the variation in TDF vertical structure. The effective LiDAR waveform of the early successional stage was characterized by one narrow peak; the late successional stage was characterized by multiple major and minor peaks; and the intermediate stage showed transitional characteristics. The normalized cumulative curves tended to be linear with the development of succession. Our multiple comparison analysis suggested that shape- and area-based metrics were generally better than point- and line-based ones in the differentiation of successional stages. Meanwhile the late successional stage can be identified by metrics from any of the four metric groups, the early and intermediate successional stages can be better identified using shape- or area-based metrics. Our ISODATA classification results further confirmed the advantages of area-based metrics since they presented the highest accuracies in nearly all accuracy measurements and for all successional stages. Our study suggests the encouraging potential of LiDAR waveform metrics in the quantification of tropical forests structure as a function of different levels of ecological succession.

Disentangling the environmental heterogeneity, floristic distinctiveness and current threats of tropical dry forests in Colombia

Tropical dry forests (TDFs) have been defined as a single biome occurring mostly in the lowlands where there is a marked period of drought during the year. In the Neotropics, dry forests occur across contrasting biogeographical regions that contain high beta diversity and endemism, but also strong anthropogenic pressures that threaten their biodiversity and ecological integrity. In Colombia, TDFs occur across six regions with contrasting soils, climate, and anthropogenic pressures, therefore being ideal for studying how these variables relate to dry forest species composition, successional stage and conservation status. Here, we explore the variation in climate and soil conditions, floristic composition, forest fragment size and shape, successional stage and anthropogenic pressures in 571 dry forest fragments across Colombia. We found that TDFs should not be classified solely on rainfall seasonality, as high variation in precipitation and temperature were correlated with soil characteristics. In fact, based on environmental factors and floristic composition, the dry forests of Colombia are clustered in three distinctive groups, with high species turnover across and within regions, as reported for other TDF regions of the Neotropics. Widely distributed TDF species were found to be generalists favored by forest disturbance and the early successional stages of dry forests. On the other hand, TDF fragments were not only small in size, but highly irregular in shape in all regions, and comprising mostly early and intermediate successional stages, with very little mature forest left at the national level. At all sites, we detected at least seven anthropogenic disturbances with agriculture, cattle ranching and human infrastructure being the most pressing disturbances throughout the country. Thus, although environmental factors and floristic composition of dry forests vary across regions at the national level, dry forests are equally threatened by deforestation, degradation and anthropogenic pressures all over the country, making TDFs a top priority for conservation in Colombia.

ESTRUTURA DA COMUNIDADE ARBÓREA E CARACTERÍSTICAS EDÁFICAS DE UM FRAGMENTO URBANO

No Brasil há diversos municípios com fragmentos florestais inseridos no perímetro urbano sob ameaça de degradação. A Mata do Desamparo (Araguari - MG) é uma importante formação florestal que protege nascentes existentes em um parque urbano. O objetivo desse estudo foi realizar o levantamento fitossociológico da vegetação arbórea do gradiente florestal e realizar análises de solo. Foram plotadas 25 parcelas de 20 x 20 m, dispostas em quatro blocos e amostrados todos os indivíduos arbóreos com circunferência a 1,30 m ≥ 15 cm e também coletadas amostras de solo a 0-20 cm de profundidade para análises químicas, umidade do solo e o desnível do terreno. Para averiguar se as propriedades químicas, umidade do solo e o desnível influenciaram na distribuição das espécies vegetais do fragmento florestal foi realizada a análise de correspondência canônica (CCA). A comunidade apresentou elevada riqueza (94 espécies) e número de indivíduos (1760) muito elevado em relação a outras florestas da região e adensamentos de espécies de borda e comuns de áreas abertas mesmo na região mais interiorana da floresta, o que indica que existem impactos antrópicos sobre a comunidade arbórea. A CCA demonstrou a heterogeneidade ambiental com a formação de três grupos, um formado pelas parcelas próximas ao leito do rio com maior umidade do solo e menor desnível, outro formado por parcelas com grande desnível, com predominância de espécies generalistas consideradas uma floresta estacional semidecidual e outro fortemente correlacionado com alumínio. Assim, este fragmento florestal pode ser considerado um importante relicto urbano com grande riqueza de espécies, no entanto, impactos passados influenciaram a estrutura da comunidade arbórea, que está em um estágio intermediário de sucessão.

Ecological succession of aquatic macrophytes on floating meadows in the Pantanal wetland

With the aim of documenting aquatic macrophyte succession on floating meadows and its relationship with histosol thickness, we sampled six-hundred 0.5 × 0.5 m2 plots of ten randomly chosen floating meadows in Baia Grande lake (Aquidauana, MS, Brazil). The floating meadows were marked in order to follow, since August 2014–August 2015, floristic and phytosociological changes and to assess their relationship with histosol thickness. We recorded 58 species belonging to 23 families and 47 genera. The richest families were Poaceae (8 species), Asteraceae (7) and Cyperaceae (6). Four species stood out for their high importance value: Oxycaryum cubense (Poepp. & Kunth) Lye, Ludwigia helminthorrhiza (Mart.) H. Hara, Eichhornia azurea (Sw.) Kunth and Vigna longifolia (Benth.) Verdc. Histosol thickness of the floating meadows varied from 1 to 51 cm, making it possible to classify them into three classes. We observed that most species (63.3%) were in the initial and intermediate stages of succession (1–34 cm histosol) and that species were replaced as a function of histosol thickness. We conclude that floating meadows have succession stages with various species of aquatic macrophytes related with histosol thickness, but species composition regarding succession stages differs from other water bodies in the Pantanal wetland.

Changes in forest structure and composition in a successional tropical dry forest

We describe changes in forest structure and floristic composition of three successional stages for Mata Seca State Park, in Minas Gerais, Brazil, through the measurement of all trees greater than 5 cm of diameter at breast height (DBH) of 18 permanent plots (6 per stage) for early, intermediate, and late successional stages of a tropical dry forest during a 5-year period. Using this information, we calculated the Importance Value Index (IVI), Holdridge Complexity Index, Jaccard Similarity Coefficient, and Shannon Diversity Index for each stage of succession. The floristic composition and structure of the successional stages expressed by the Holdridge Complexity Index, showed that complexity increases gradually as we advance through the successional stages, while the Shannon Diversity Index indicated that species diversity was higher in the intermediate stage of succession. The Jaccard Similarity Coefficients showed that the intermediate and late successional stages had high similarity, whereas the early successional stage had low similarity with these two successional stages. Mortality rates were higher in the early stage, especially in stems with smaller diameters (5-10cm). This information contributes to the dissemination of important knowledge for the conservation of the tropical dry forests of Brazil, which are the most threatened ecosystems in this country and, at the same time, the least studied.

Modeling seasonal surface temperature variations in secondary tropical dry forests

Secondary tropical dry forests (TDFs) provide important ecosystem services such as carbon sequestration, biodiversity conservation, and nutrient cycle regulation. However, their biogeophysical processes at the canopy-atmosphere interface remain unknown, limiting our understanding of how this endangered ecosystem influences, and responds to the ongoing global warming. To facilitate future development of conservation policies, this study characterized the seasonal land surface temperature (LST) behavior of three successional stages (early, intermediate, and late) of a TDF, at the Santa Rosa National Park (SRNP), Costa Rica. A total of 38 Landsat-8 Thermal Infrared Sensor (TIRS) data and the Surface Reflectance (SR) product were utilized to model LST time series from July 2013 to July 2016 using a radiative transfer equation (RTE) algorithm. We further related the LST time series to seven vegetation indices which reflect different properties of TDFs, and soil moisture data obtained from a Wireless Sensor Network (WSN). Results showed that the LST in the dry season was 15–20K higher than in the wet season at SRNP. We found that the early successional stages were about 6–8K warmer than the intermediate successional stages and were 9–10K warmer than the late successional stages in the middle of the dry season; meanwhile, a minimum LST difference (0–1K) was observed at the end of the wet season. Leaf phenology and canopy architecture explained most LST variations in both dry and wet seasons. However, our analysis revealed that it is precipitation that ultimately determines the LST variations through both biogeochemical (leaf phenology) and biogeophysical processes (evapotranspiration) of the plants. Results of this study could help physiological modeling studies in secondary TDFs.

Spatial and temporal changes in epibenthic communities at deep, hard bottom aquaculture sites in Newfoundland

This study explores spatio-temporal changes in epibenthic communities due to salmon aquaculture at deep (>30m), hard-bottom dominated sites in Newfoundland (Canada). Using a drop-camera approach, we followed changes with production at two aquaculture sites, as well as potential recovery processes at two fallow sites, comparing their epibenthic composition with nearby non-production sites. Multivariate analysis revealed that aquaculture production led to rapid changes in epibenthic communities, as evidenced primarily by the presence of two visual indicators: bacterial mats and opportunistic polychaetes. Due to low taxon richness and abundances, as well as variability among sites, no clear intermediate successional stages were apparent. Beggiatoa-like mats and opportunistic polychaetes appeared rapidly once aquaculture production began; these indicators did not increase in spatial extent during the survey and were typically observed up to 100m, and occasionally up to 160m from cages. After 15 months of fallowing, Beggiatoa-like mats and opportunistic polychaetes remained present at sites and were occasionally accompanied by few other taxa, suggesting incomplete recovery.

Changes in biotic and abiotic drivers of seedling species composition during forest recovery following shifting cultivation on Hainan Island, China

AbstractSeedlings play an important role in the processes of plant community succession. We compared seedling (dbh < 1 cm) species composition and diversity over a chronosequence (18‐, 30‐, 60‐year‐old second growth and old growth forest) after shifting cultivation in a tropical lowland rain forest area on Hainan Island, China. Seedling diversity reached a maximum in the 60‐year‐old second growth forest, which is consistent with the intermediate disturbance hypothesis. With the progression of secondary succession, canopy openness (CO), soil organic matter, soil phosphorus content, and tree abundance showed a general decreasing trend; soil water content and tree basal area showed a general trend of increase, while soil pH and other nutrients reached maximum values and tree richness reached a minimum value at intermediate stages of succession. Seedling composition and diversity were significantly affected by soil water, pH, soil nutrient content, and biotic factors in the 18‐year‐old second growth forests; by soil pH, soil nutrient content, and biotic factors in the 30‐year‐old second growth forests; by CO, soil nutrient content and tree abundance in the 60‐year‐old second growth forests; and by CO, soil pH, and soil nutrient content in the old growth forests. At earlier stages of succession, the effect of the proportion of old growth forest in the surrounding landscape on seedling diversity was greater than that of land‐use history, but the importance of these drivers was reversed at later stages of succession.

Quantifying economic losses from wildfires in black pine afforestations of northern Spain

We implemented a fire risk assessment framework that combines spatially-explicit burn probabilities, post-fire mortality models and public auction timber prices, to estimate expected economic losses from wildfires in 155 black pine stands covering about 450ha in the Juslapeña Valley of central Navarra, northern Spain. A logit fire occurrence model was generated from observed historic fires to provide required fire ignition input data. Wildfire likelihood and intensity were estimated by modeling 50,000 fires with the minimum travel time algorithm (MTT) at 30m resolution under 97th percentile fire weather conditions. Post-fire tree mortality due to burning fire intensity at different successional stages ranged from 0.67% in the latest stages to 9.22% in the earliest. Stands showed a wide range of potential economic losses, and intermediate successional stage stands presented the highest values, with about 124€ha−1 on average. A fire risk map of the target areas was provided for forest management and risk mitigation purposes at the individual stand level. The approach proposed in this work has a wide potential for decision support, policy making and risk mitigation in southern European commercial conifer forests where large wildfires are the main natural hazard.

Tree succession across a seasonally dry tropical forest and forest-savanna ecotone in northern Minas Gerais, Brazil

Aims: Understanding succession in tropical forest is an important aspect of vegetation science, but to date, successional processes in seasonally dry tropical forests (SDTFs) have received much less attention than evergreen humid tropical forests. We aim to fill this knowledge gap. Methods: We investigated vegetation succession in SDTF areas consisting of three different successional stages (early, intermediate, late), and a SDTF-savanna ecotone in the municipal district of Juramento, north of Minas Gerais State, Brazil. Using twelve 400 m(2) plots in each area, we compared vegetation parameters and structural variables (absolute density and basal area) and examined the floristic composition of the tree component to find gradients of change. Important Findings: We found evidence of species turnover along a successional gradient, with the intermediate stage showing the highest species richness and diversity. This was accompanied with a significant increase in the number of tree individuals and basal area from the early to intermediate successional stage. However, the intermediate and late SDTF successional stages were more similar in structure and floristics. The ecotone was the most species rich and was similar to the intermediate SDTF and early successional stage in species richness and floristic composition respectively. These results will have implications for guiding SDTF management and recovery programs.

Effects of density dependence in a temperate forest in northeastern China.

Negative density dependence may cause reduced clustering among individuals of the same species, and evidence is accumulating that conspecific density-dependent self-thinning is an important mechanism regulating the spatial structure of plant populations. This study evaluates that specific density dependence in three very large observational studies representing three successional stages in a temperate forest in northeastern China. The methods include standard spatial point pattern analysis and a heterogeneous Poisson process as the null model to eliminate the effects of habitat heterogeneity. The results show that most of the species exhibit conspecific density-dependent self-thinning. In the early successional stage 11 of the 16 species, in the intermediate successional stage 18 of the 21 species and in the old growth stage all 21 species exhibited density dependence after removing the effects of habitat heterogeneity. The prevalence of density dependence thus varies among the three successional stages and exhibits an increase with increasing successional stage. The proportion of species showing density dependence varied depending on whether habitat heterogeneity was removed or not. Furthermore, the strength of density dependence is closely related with species abundance. Abundant species with high conspecific aggregation tend to exhibit greater density dependence than rare species.

COMPOSIÇÃO FLORÍSTICA E CARACTERIZAÇÃO SUCESSIONAL COMO SUBSÍDIO PARA CONSERVAÇÃO E MANEJO DO PNMCBio, SOROCABA - SP

http://dx.doi.org/10.5902/1980509821125O trabalho foi realizado no Parque Natural Municipal Corredores da Biodiversidade (PNMCBio), em Sorocaba -SP, com o objetivo de avaliar a composição florística do componente arbóreo e o estágio sucessional de uma área de floresta nativa de aproximadamente 31 hectares. Para tanto, foram alocadas 64 parcelas de tamanho 10 x 10 m, distribuídas aleatoriamente na área, sendo coletados todos os indivíduos com CAP igual ou maior que 15 cm. Estimou-se a diversidade por meio do índice de diversidade de Shannon (H’) e a equabilidade por meio do índice de Pielou (J’). As espécies foram caracterizadas nos grupos sucessionais, síndrome de dispersão, categorias de ameaça, amplitude de distribuição e indicadoras do estágio de regeneração. Foram amostrados 1088 indivíduos, distribuídos em 79 espécies, 54 gêneros e 29 famílias, sendo o H’ estimado em 3,421 e o J’ em 0,78, valores próximos aos encontrados em outras áreas de formações vegetacionais similares. Foram identificadas quatro espécies ameaçadas de extinção, 11 espécies endêmicas da Mata Atlântica e duas espécies restritas à Floresta Estacional Semidecidual no domínio da Mata Atlântica. O fragmento encontra-se em estágio médio de regeneração, sendo de suma importância sua conservação e manejo para a manutenção da biodiversidade local e regional.

Importance of succession, harvest, and climate change in determining future composition in U.S. Central Hardwood Forests

Most temperate forests in U.S. are recovering from heavy exploitation and are in intermediate successional stages where partial tree harvest is the primary disturbance. Changes in regional forest composition in response to climate change are often predicted for plant functional types using biophysical process models. These models usually simplify the simulation of succession and harvest and may not consider important species‐specific demographic processes driving forests changes. We determined the relative importance of succession, harvest, and climate change to forest composition changes in a 125‐million ha area of the Central Hardwood Forest Region of U.S. We used a forest landscape modeling approach to project changes in density and basal area of 23 tree species due to succession, harvest, and four climate scenarios from 2000 to 2300. On average, succession, harvest, and climate change explained 78, 17, and 1% of the variation in species importance values (IV) at 2050, respectively, but their contribution changed to 46, 26, and 20% by 2300. Climate change led to substantial increases in the importance of red maple and southern species (e.g., yellow‐poplar) and decreases in northern species (e.g., sugar maple) and most of widely distributed species (e.g., white oak). Harvest interacted with climate change and accelerated changes in some species (e.g., increasing southern red oak and decreasing American beech) while ameliorated the changes for others (e.g., increasing red maple and decreasing white ash). Succession was the primary driver of forest composition change over the next 300 years. The effects of harvest on composition were more important than climate change in the short term but climate change became more important than harvest in the long term. Our results show that it is important to model species‐specific responses when predicting changes in forest composition and structure in response to succession, harvest, and climate change.

Plant functional traits suggest a change in novel ecological strategies for dominant species in the stages of forest succession

In forest succession, the ecological strategies of the dominant species that are based on functional traits are important in the determination of both the mechanisms and the potential directions of succession. Thirty-one plots were established in the Loess Plateau region of northern Shaanxi in China. Fifteen leaf traits were measured for the 31 dominant species that represented the six stages of succession, and the traits included four that were related to morphology, seven to stoichiometry and four to physiological ecology. The species from the different successional stages had different patterns of distribution of the traits, and different key traits predicted the turnover of the species during succession. The ash and the cellulose contents were key regulatory factors of species turnover in the early successional communities, and the trait niche forces in sugar and leaf dry mass content might become more important with the progression of succession. When only the three herb stages were considered, a progressive replacement of the ruderal by the competitive-ruderal species occurred in the intermediate stages of succession, which was followed by the stress-tolerant-competitive or the competitive-stress tolerant-ruderal strategists late in the succession. Thus, the different species that occurred in the different stages of succession shared different trait-based ecological strategies. Additionally, these differences occurred concomitantly with a shift toward competitive-stress tolerant-ruderal strategies.

Re‐growing a tropical dry forest: functional plant trait composition and community assembly during succession

SummaryA longstanding goal of ecology and conservation biology is to understand the environmental and biological controls of forest succession. However, the patterns and mechanisms that guide successional trajectories, especially within tropical forests, remain unclear.We collected leaf functional trait and abiotic data across a 110‐year chronosequence within a tropical dry forest in Costa Rica. Focusing on six key leaf functional traits related to resource acquisition and competition, along with measures of forest stand structure, we propose a mechanistic framework to link species composition, community trait distributions and forest structure. We quantified the community‐weighted trait distributions for specific leaf area, leaf dry matter concentration, leaf phosphorus concentration, leaf carbon to nitrogen ratio and leaf stable isotopic carbon and nitrogen. We assessed several prominent hypotheses for how these functional measures shift in response to changing environmental variables (soil water content, bulk density andpH) across the chronosequence.Increasingly, older forests differed significantly from younger forests in species composition, above‐ground biomass and shifted trait distributions. Early stages of succession were uniformly characterized by lower values of community‐weighted mean specific leaf area, leaf stable nitrogen isotope and leaf phosphorus concentration. Leaf dry matter concentration and leaf carbon to nitrogen ratio were lower during earlier stages of succession, and each trait reached an optimum during intermediate stages of succession. The leaf carbon isotope ratio was the only trait to decrease linearly with increasing stand age indicating reduced water use efficiency in older forests. However, in contrast with expectations, community‐weighted trait variances did not generally change through succession, and when compared to null expectations were lower than expected.The observed directional shift in community‐weighted mean trait values is consistent with the ‘productivity filtering’ hypothesis where a directional shift in water and light availability shifts physiological strategies from ‘slow’ to ‘fast’. In contrast with expectations arising from niche based ecology, none of the community trait distributions were over‐dispersed. Instead, patterns of trait dispersion are consistent with the abiotic filtering and/or competitive hierarchy hypotheses.

Fractal Feature of Particle-Size Distribution in the Rhizospheres and Bulk Soils during Natural Recovery on the Loess Plateau, China.

The application of fractal geometry to describe soil structure is an increasingly useful tool for better understanding the performance of soil systems. Only a few studies, however, have focused on the structure of rhizospheric zones, where energy flow and nutrient recycling most frequently occur. We used fractal dimensions to investigate the characteristics of particle-size distribution (PSD) in the rhizospheres and bulk soils of six croplands abandoned for 1, 5, 10, 15, 20, and 30 years on the Loess Plateau of China and evaluated the changes over successional time. The PSDs of the rhizospheres and the fractal dimensions between rhizosphere soil and bulk soils during the natural succession differed significantly due to the influence of plant roots. The rhizospheres had higher sand (0.05–1.00 mm) contents, lower silt (<0.002 mm) contents, and lower fractal dimensions than the bulk soils during the early and intermediate successional stages (1–15 years). The fractal dimensions of the rhizosphere soil and bulk soil ranged from 2.102 to 2.441 and from 2.214 to 2.459, respectively, during the 30-year restoration. Rhizospheric clay and silt contents and fractal dimension tended to be higher and sand content tended to be lower as abandonment age increased, but the bulk soils had the opposite trend. Linear regression analysis indicated that the fractal dimensions of both the rhizospheres and bulk soils were significantly linearly correlated with clay, sand, organic-carbon, and total-nitrogen contents, with R 2 ranging from 0.526 to 0.752 (P<0.001). In conclusion, PSD differed significantly between the rhizosphere soil and bulk soil. The fractal dimension was a sensitive and useful index for quantifying changes in the properties of the different soil zones. This study will greatly aid the application of the fractal method for describing soil structure and nutrient status and the understanding of the performance of rhizospheric zones during ecological restoration.

DIVERSIDAD DE MARIPOSAS DIURNAS (INSECTA: LEPIDÓPTERA) DE UN BOSQUE SUBANDINO, CAJIBÍO, CAUCA

In the department of Cauca, still remains small fragments sub-Andean forest persist. The nature reserve Raices de Vida (Roots of Life) of the school Carmen Quintana, at Cajibio (Cauca), has one of these fragments but influenced by areas of agricultural uses. This prompted a need for investigate the actual state in order to define and, if needed, implement educational and management strategies. With this objective in mind, a sampling of diurnal Lepidoptera community (as a biological indicator) was carried out. Analyses of data of richness and abundance of Lepidoptera allowed to defined how this insect community is associated with the state of the forest. A total of 785 butterflies, grouped in 80 species, was recorded. Specimens belong to the superfamily Papilionioidea and represent four families: Pieridae, Hesperiidae, Nymphalidae and Lycaenidae. A total of 14 species, indicators of disturbed ecosystems, include Leptophobia aripa, Anartia amathea, Euptychia hermes and Phoebis sennae. On the other hand, a good forest species like Manataria maculata, Pseudohaetera hypaesia, Taygetis chrysogone, Memphis lyceus and Heliconius erato chestertoni were found. Results suggest that this small forest fragment is under an intermediate successional stage, hence representing an important area for conservation and environmental education strategies.

Resilience of savanna forest after clear-cutting in the cerrado-amazon transition zone

The dynamics of the natural process of recuperation of the structure and diversity of native vegetation following anthropogenic disturbance has been the subject of a great deal of controversy in restoration ecology research. The present study evaluates the natural regeneration of savanna forest ( cerradao ) 32 and 36 years after the clear-cutting of the vegetation. We compared species diversity, and the structure and dynamics of the vegetation in two communities, one representing preserved cerradao (PC), and the other, the regenerating cerradao (RC), which was clear-cut in 1976. Surveys were conducted in 2008 and 2012, 32 and 36 years after clear-cutting, respectively. In 2008, we demarcated 81 permanent 10 m x 10 m plots, 50 in the RC and 31 in the PC, and measured all live plants with a diameter at soil level > 5 cm. In 2012, the plots were resampled, including the original plants and all the recruits. The species were classified as specialists in savanna (SA) or forest habitat (FO), or as generalists (SA/FO). The RC presented the highest species richness and diversity, density, annual increment, and mortality rates. However, no significant differences were found between communities in the distribution of specialist or generalist species, or between years (2008 and 2012) in basal area or recruitment rates. While the species composition of the two communities is highly similar, the RC was characterized by a higher frequency of SA species, and was more similar to nearby savanna communities (cerrado sensu stricto ). Trees in the RC were smaller and suffered higher rates of mortality than those in the PC, but also higher annual increments. While the RC demonstrated a high degree of resilience following clear-cutting, it was still found to be at an intermediate stage of succession, even after almost four decades, indicating that regeneration is a slow process.