Analysis of mangrove forest succession, using sediment cores: a case study in the Cananéia -Iguape coastal system, São Paulo Brazil

Sediment cores are an essential tool for the analysis of the dynamics of mangrove succession. Coring was used to correlate changes in depositional environments and lateral sedimentary facies with discrete stages of forest succession at the Cananéia-Iguape Coastal System in southeastern Brazil. A local level successional pattern was examined based on four core series T1) a sediment bank; T2) a smooth cordgrass Spartina alterniflora bank; T3) an active mangrove progradation fringe dominated by Laguncularia racemosa, and; T4) a mature mangrove forest dominated by Avicennia schaueriana. Cores were macroscopically described in terms of color, texture, sedimentary structure and organic components. The base of all cores exhibited a similar pattern suggesting common vertical progressive changes in depositional conditions and subsequent successional colonization pattern throughout the forest. The progradation zone is an exposed bank, colonized by S. alterniflora. L. racemosa, replaces S. alterniflora as progradation takes place. As the substrate consolidates A. schaueriana replaces L. racemosa and attains the greatest structural development in the mature forest. Cores collected within the A. schaueriana dominated stand contained S. alterniflora fragments near the base, confirming that a smooth cordgrass habitat characterized the establishment and early seral stages. Cores provide a reliable approach to describe local-level successional sequences in dynamic settings subject to drivers operating on multiple temporal and spatial scales where spatial heterogeneity can lead to multiple equilibria and where similar successional end-points may be reached through convergent paths.

The relationship between stem vessel parameters and the development of strata in the early stages of secondary forest succession in Amazonia

In order to compare the development of strata in the early stages of secondary forest succession with vessel parameters of the tree species, a forest inventory was carried out in 4-year (Q1: 48 m2), 11-year (Q2: 400 m2) and 20-year (Q3: 400 m2) forests and vessel parameters were investigated from stem cross sections of 18 species obtained in Q2. Thirty three species (21 families), 77 species (35 families), 39 species (20 families) were found in Ql, Q2, Q3, respectively. The percentage of dead individuals, dead stems and the percentage of individuals with multiple stems increased with time after clear cutting. Also, the total D2H of Q3 was 26.1 times that of Q1, and the development of strata started in Q2 and Q3. The image analysis of vessel size, area and number of vessels revealed that species which reach the forest canopy had a large D2H value, vessel diameter and area, while species which remain near the forest floor had smaller ones. Poecilanthe effusa (Huber) Ducke is an example of the latter case, with a large number of individuals and abundant sprouting of new stems from stumps, but with high mortality.

Atlantic Forest succession over calcareous soil, Parque Estadual Turístico do Alto Ribeira - PETAR, SP

The forest succession after abandonment of slash-and-burn agriculture over calcareous soil in Brazilian Atlantic Forest was assessed. This is one of the world's most threatened Biome, with only 8% remaining. The study area is located over calcareous soil inside the Alto Ribeira Touristic State Park (PETAR), southeast Brazil. The phytossociological survey showed a successional pattern dominated by species of Leguminosae, especially Piptadenia gonoacantha (Mart.) J.F. Macbr. This species occurs in calcareous soils as a substitute of Tibouchina pulchra (Cham.) Cogn. (Melastomataceae) that is the most usual dominant tree species in early succession over acidic soil, which is the most common situation in this Biome. These results are important for a better understanding of Neotropical forest biodiversity and characterize a unique genetic bank in this highly endangered Biome. They are also decisive to support actions regarding rehabilitation of degraded lands and a potential tool for Neotropical forest sustainable management, both inside and around the conservation unit.

The impact of fragmentation and density regulation on forest succession in the Atlantic rain forest

The Atlantic Rain Forest, an important biodiversity hot spot, has faced severe habitat loss since the last century which has resulted in a highly fragmented landscape with a large number of small forest patches (<100 ha). For conservation planning it is essential to understand how current and future forest regeneration depends on ecological processes, fragment size and the connection to the regional seed pool. We have investigated the following questions by applying the forest growth simulation model FORMIND to the situation of the Atlantic Forest in the state of Sao Paulo, SE Brazil: (1) which set of parameters describing the local regeneration and level of density regulation can reproduce the biomass distribution and stem density of an old growth forest in a reserve? (2) Which additional processes apart from those describing the dynamics of an old growth forest, drive forest succession of small isolated fragments? (3) Which role does external seed input play during succession? Therefore, more than 300 tree species have been classified into nine plant functional types (PFTs), which are characterized by maximum potential height and shade tolerance. We differentiate between two seed dispersal modes: (i) local dispersal, i.e. all seedlings originated from fertile trees within the simulated area and (ii) external seed rain. Local seed dispersal has been parameterized following the pattern oriented approach, using biomass estimates of old growth forest. We have found that moderate density regulation is essential to achieve coexistence for a broad range of regeneration parameters. Considering the expected uncertainty and variability in the regeneration processes it is important that the forest dynamics are robust to variations in the regeneration parameters. Furthermore, edge effects such as increased mortality at the border and external seed rain have been necessary to reproduce the patterns for small isolated fragments. Overall, simulated biomass is much lower in the fragments compared to the continuous forest, whereas shade tolerant species are affected most strongly by fragmentation. Our simulations can supplement empirical studies by extrapolating local knowledge on edge effects of fragments to larger temporal and spatial scales. In particular our results show the importance of external seed rain and therefore highlight the importance of structural connectivity between regenerating fragments and mature forest stands. (C) 2009 Elsevier B.V. All rights reserved.

ANALYSIS OF MANGROVE FOREST SUCCESSION, USING SEDIMENT CORES: A CASE STUDY IN THE CANANEIA-IGUAPE COASTAL SYSTEM, SAO PAULO-BRAZIL

Sediment cores are an essential tool for the analysis of the dynamics of mangrove succession. Coring was used to correlate changes in depositional environments and lateral sedimentary facies with discrete stages of forest succession at the Cananeia-Iguape Coastal System in southeastern Brazil. A local level successional pattern was examined based on four core series T1) a sediment bank; T2) a smooth cordgrass Spartina alterniflora bank; T3) an active mangrove progradation fringe dominated by Laguncularia racemosa, and; T4) a mature mangrove forest dominated by Avicennia schaueriana. Cores were macroscopically described in terms of color, texture, sedimentary structure and organic components. The base of all cores exhibited a similar pattern suggesting common vertical progressive changes in depositional conditions and subsequent successional colonization pattern throughout the forest. The progradation zone is an exposed bank, colonized by S. alterniflora. L. racemosa, replaces S. alterniflora as progradation takes place. As the substrate consolidates A. schaueriana replaces L. racemosa and attains the greatest structural development in the mature forest. Cores collected within the A. schaueriana dominated stand contained S. alterniflora fragments near the base, confirming that a smooth cordgrass habitat characterized the establishment and early seral stages. Cores provide a reliable approach to describe local-level successional sequences in dynamic settings subject to drivers operating on multiple temporal and spatial scales where spatial heterogeneity can lead to multiple equilibria and where similar successional end-points may be reached through convergent paths.

Nitrogen use strategies of neotropical rainforest trees in threatened Atlantic Forest

The characteristics of nitrogen acquisition, transport and assimilation were investigated in species of an Atlantic Forest succession over calcareous soil in south-eastern Brazil. Differences in behaviour were observed within the regeneration guilds. Pioneer species showed high leaf nitrogen contents, a high capacity to respond to increased soil nitrogen availability, a high capacity for leaf nitrate assimilation and were characterized by the transport of nitrate + asparagine. At the other end of the succession, late secondary species had low leaf nitrogen contents, little capacity to respond to increased soil nitrogen availability, low leaf nitrate assimilation and were active in the transport of asparagine + arginine. The characteristics of nitrogen nutrition in some early secondary species showed similarities to those of pioneer species whereas others more closely resembled late secondary species. Average leaf delta(15)N values increased along the successional gradient. The results indicate that the nitrogen metabolism characteristics of species may be an additional ecophysiological tool in classifying tropical forest tree species into ecological guilds, and may have implications for regeneration programmes in degraded areas.

Photosynthetic responses of four tropical tree species grown under gap and understorey conditions in a semi-deciduous forest

Leaf CO2 assimilation (A) as a function of photosynthetic photon flux density (Q) or intercellular CO2 concentration (Ci) and chlorophyll fluorescence measurements were carried out on four tropical woody species growing in forest gap and understorey (Bauhinia forficata Link. and Guazuma ulmifolia Lam. as pioneers, and Hymenaea courbaril L. and Esenbeckia leiocarpa Engl. as non-pioneers). Chlorophyll fluorescence indicated similar acclimation capacities of photochemical apparatus to contrasting light environments irrespective to plant species. Maximum CO2 assimilation and quantum yield derived from A/Q curves indicated higher photosynthetic capacity in pioneer than in non-pioneer species in forest gap. However, the differences among species did not show a straightforward relation with their successional status regarding data derived from A/Q curves under understorey conditions. Both successional groups are able to sustain positive carbon balance under contrasting natural light availabilities, modifying photochemical and biochemical photosynthetic traits with similar phenotypic plasticity capacity.

Use of Large Clear-Cuts by Wilson’s Warbler in an Eastern Canadian Boreal Forest

Wilson’s Warbler (Cardellina pusilla; WIWA) has been declining for several decades, possibly because of habitat loss. We compared occupancy of territorial males in two habitat types of Québec’s boreal forest, alder (Alnus spp.) scrubland and recent clear-cuts. Singing males occurred in clusters, their occupancy was similar in both habitats, but increased with the amount of alder or clear-cut within 400 m of point-count stations. A despotic distribution of males between habitats appeared unlikely, because there were no differences in morphology between males captured in clear-cuts vs. alder. Those results contrast with the prevailing view, mostly based on western populations, that WIWA are wetland or riparian specialists, and provide the first evidence for a preference for large tracts of habitat in this species. Clear-cuts in the boreal forest may benefit WIWA by supplying alternative nesting habitat. However, the role of clear-cuts as source or sink habitats needs to be addressed with data on reproduction.

Succession and management of tropical dry forests in the Americas: Review and new perspectives

Understanding tropical forest succession is critical for the development of tropical forest conservation strategies worldwide, given that tropical secondary forests can be considered the forests of the future. Tropical dry forests (TDF) are among the most threatened tropical ecosystems, there are more secondary forests and forest restoration efforts that require a better understanding of successional processes. The main goal of this synthesis for this special issue on the ecology and management of tropical dry forests in the Americas is to present a summarized review of the current knowledge of the ecology and management implications associated to TDF succession. We explore specific issues associated to tropical dry forest succession with emphasis on the use of chronosequences, plant diversity and composition, plant phenology and remote sensing, pollination, and animal-plant interactions; all under the integrating umbrella of ecosystem succession. We also emphasize the need to conduct socio-ecological research to understand changes in land-use history and its effects on succession and forest regeneration of TDF. We close this paper with some thoughts and ideas associated with the strong need for an integrating dimension not considered until today: the role of cyberinfrastructure and eco-informatics as a tool to support sound conservation, management and understanding of TDF in the Americas. (C) 2009 Elsevier B.V. All rights reserved.

Can overharvesting of a non-timber-forest-product change the regeneration dynamics of a tropical rainforest? The case study of Euterpe edulis

The exploitation of non-timber forest products is often considered a low-impact activity in tropical forests. However, assessments of the impacts of such activity are mostly focused on the harvested species and not on the plant community, thus limiting our understanding for establishing forest management recommendations. We investigated the consequences of Euterpe edulis palm heart harvesting on the seed rain in the Brazilian Atlantic rainforest. We compared the density of E. edulis individuals, as well as the density of E. edulis seeds, and the density, richness and functional composition of seed rain of the whole plant community, before and after palm heart harvesting in a 10 ha permanent plot. This assessment was carried out in preserved (typical old-growth Atlantic rainforest) and in disturbed (more open habitat dominated by the native bamboo Guadua tagoara) forest patches. Palm harvesting reduced the E. edulis population from 202.16 to 25.67 ind/ha and its seed rain density from 0.362 to 0.3 seeds/m2 and from 2.395 to 0.15 seeds/m2 in preserved and disturbed forest patches, respectively. Seed density of light-dependent climbers, pioneer trees, bamboo and animal-dispersed seeds increased after palm harvesting, especially in the disturbed forest patches, where palm harvesting was more intense and may have changed the light regime of the understory. On the other hand, species richness of the plant community declined by half. We observed a remarkable decline in the number of animal-dispersed species, especially for those with large seeds, suggesting that the activity of seed dispersers, including many species attracted by E. edulis fruits, was reduced. Therefore, harvesting of E. edulis palm heart may change the regeneration dynamics of the Atlantic rainforest, both due to shifts in forest structure, mediated by the removal of individuals from the forest canopy, and in community functioning, mediated by the interference on the activity of seed dispersers. © 2013 Elsevier B.V. All rights reserved.

THE CONVERSION OF THE ATLANTIC FOREST IN ANTHROPOGENIC LANDSCAPES: LESSONS FOR THE CONSERVATION OF BIOLOGICAL DIVERSITY OF TROPICAL FORESTS

The Brazilian Atlantic forest has been an excellent laboratory for investigations regarding tropical forest ecology and the fragility of tropical ecosystems in face of human disturbances. In this article, we present a synthesis about the spatial distribution of Atlantic forest biodiversity and forest response to human disturbances, as well as the ongoing conservation efforts based on a review of several investigations in this biota. In general, studies have documented an uneven distribution of biodiversity throughout the Atlantic forest region, revealing alarming rates of habitat loss at low altitudes, while protected areas concentrate at higher altitudes. It has been suggested that the remaining forest habitat is moving towards an early-successional systems across human-modified landscapes. Such regressive forest succession increases the threats for several animals and plant groups. Based on these findings, we propose seven guidelines in order to enhance the provision of ecosystem services and the conservation value of human-modified landscapes, reducing the species extinction risk in the Atlantic forest and in other irreplaceable tropical biotas.

Habitat structure and food resources for wildlife across successional stages in a tropical forest

Tropical forests are experiencing an increase in the proportion of secondary forests as a result of the balance between the widespread harvesting of old-growth forests and the regeneration in abandoned areas. The impacts of such a process on biodiversity are poorly known and intensely debated. Recent reviews and multi-taxa studies indicate that species replacement in wildlife assemblages is a consistent pattern, sometimes stronger than changes in diversity, with a replacement from habitat generalists to old-growth specialists being commonly observed during tropical forest regeneration. However, the ecological drivers of such compositional changes are rarely investigated, despite its importance in assessing the conservation value of secondary forests, and to support and guide management techniques for restoration. By sampling 28 sites in a continuous Atlantic forest area in Southeastern Brazil, we assessed how important aspects of habitat structure and food resources for wildlife change across successional stages, and point out hypotheses on the implications of these changes for wildlife recovery. Old-growth areas presented a more complex structure at ground level (deeper leaf litter, and higher woody debris volume) and higher fruit availability from an understorey palm, whereas vegetation connectivity, ground-dwelling arthropod biomass, and total fruit availability were higher in earlier successional stages. From these results we hypothetize that generalist species adapted to fast population growth in resource-rich environments should proliferate and dominate earlier successional stages, while species with higher competitive ability in resource-limited environments, or those that depend on resources such as palm fruits, on higher complexity at the ground level, or on open space for flying, should dominate older-growth forests. Since the identification of the drivers of wildlife recovery is crucial for restoration strategies, it is important that future work test and further develop the proposed hypotheses. We also found structural and functional differences between old-growth forests and secondary forests with more than 80 years of regeneration, suggesting that restoration strategies may be crucial to recover structural and functional aspects expected to be important for wildlife in much altered ecosystems, such as the Brazilian Atlantic forest. (C) 2012 Elsevier B.V. All rights reserved.

Native tree seedling growth when fertilized with different amounts of dry sewage sludge and mineral fertilizer

The increasing volume of urban sewage nowadays generates considerable amount of sludge to be disposed of. One environmentally adequate destination could be the application of treated and stabilized sludge (biosolids) to forest plantations as fertilizer and soil conditioner. The purpose of this study was to analyze the feasibility of applying sewage sludge, evaluating its effects on native tree seedlings. The species evaluated were aroeira-pimenteira (Schinus terebinthifolia Raddi), cabreuva-vermelha (Myroxy-Ion peruiferum L. f.), pau-de-viola (Cytarexyllum myrianthum Cham), unha-de-vaca (Bauhinia forficata Link), which are usually planted in forest restoration. Seedlings were cultivated in pots, containing a volume of 4 dm(3) of soil, within a greenhouse. The study was developed in the proximity of Campinas, SP, Brazil, and installed in November, 2003. The design was entirely randomized including seven treatments: control; mineral fertilization; and different doses of sewage sludge (biosolids) complemented with potassium, due to the low concentration of this element in the sludge produced by the wastewater treatment plant of Barueri (Metropolitan region of Sao Paulo city). The results showed that the application of different dosages of biosolids promoted different responses in stem height and biomass production. The treatment with 20 g/dm(3) of dry sewage sludge promoted both the highest growth and the highest seedling biomass production, compared to the control treatment. All native tree species treated with the highest dosage of sewage sludge showed a growth similar to that of mineral fertilization. The seedlings of aroeira-pimenteira, pau-de-viola, and unha-de-vaca, all typical species of the initial succession in natural forest ecosystems, grew and produced more biomass than cabreuva-vermelha, a typical species of the final forest succession.

Influência da luminosidade na fisiologia e morfoanatomia de jequitibá branco (Cariniana estrellensis (Raddi.) Kuntze) e jequitibá rosa (Cariniana legalis (Mart.) Kuntze)

Cariniana estrellensis (Raddi.) Kuntze e C. legalis (Mart.) Kuntze são arbóreas nativas do Brasil que, além de possuírem alto poder econômico, são objeto de interesse em programas de recuperação de áreas degradadas e em plantios comerciais. A escassez de informações relacionadas ao desempenho ecofisiológico dessas espécies em condições ambientais estressantes dificultam o manejo e conservação das mesmas. Dessa forma, o presente estudo objetivou avaliar a ecofisiologia das espécies em um gradiente de irradiância, por meio de dois experimentos. No experimento 1, plantas de C. estrellensis com 12 meses de idade foram submetidas a quatro tratamentos: 40%, 50%, 70% e 100% de irradiância, durante 104 dias. Ao final desse período foram feitas análises de crescimento, do conteúdo de pigmentos fotossintéticos, de trocas gasosas, da fluorescência da clorofila a, do conteúdo foliar de carboidratos solúveis, das características anatômicas foliares e caulinares e da plasticidade fenotípica da espécie. No experimento 2, plantas de C. estrellensis e C. legalis com 14 meses de idade foram submetidas a dois tratamentos: 30% e 100% de irradiância (sombra e sol, respectivamente), durante 30 dias. Ao final desse período foram feitas análises do estresse oxidativo das espécies, por meio da quantificação da atividade das enzimas catalase e peroxidase do ascorbato e por meio da quantificação do conteúdo foliar de pigmentos fotossintéticos. No experimento 1, em 70% de irradiância, as plantas apresentaram melhor crescimento em altura e diâmetro, maior massa seca de folhas (MSF), de caule (MSC) e de raiz (MSR). Em 70% e 100% de irradiância, as plantas apresentaram folhas menores (AFU) e mais espessas (AFE e MFE) resultando em menor área foliar total (AFT). Nesses tratamentos as plantas também apresentaram menor conteúdo foliar de clorofila a (Chl a) e b (Chl b), porém, maior razão Chl a/b e maior conteúdo de carotenóides, o que implicou em menor razão Chl a/Carot. Taxas fotossintéticas maiores foram encontradas nas plantas em 70% e inibidas em 40% e 50%, em função da baixa irradiância solar, e em 100%, possivelmente pela ocorrência de fotoinibição, como mostraram os parâmetros do fluxo de energia do fotossistema II. De acordo com a análise da fluorescência da clorofila a, em pleno sol, as plantas apresentaram menor densidade de centros de reação ativos (RC/ABS) e maior dissipação de energia (DI0/ABS), culminando com menor desempenho do fotossistema II (PIabs) e desempenho total (PITotal). O conteúdo foliar de carboidratos solúveis foi maior nas plantas em 70%, seguido das plantas em 100% de irradiância, com exceção da glicose, que não variou entre os tratamentos. A maior espessura encontrada nas folhas sob 100% de irradiância foi em função da maior espessura das epidermes adaxial e abaxial e dos parênquimas paliçádico e esponjoso. E o maior diâmetro do caule em 70% de irradiância se deu pela maior espessura do xilema e floema secundários. No experimento 2, as plantas em pleno sol de ambas as espécies também apresentaram menor conteúdo foliar de clorofila a (Chl a) e b (Chl b) e maior razão Chl a/b. No entanto, o conteúdo de carotenóides foi maior, o que implicou em menores razões Chl a/Carot. A atividade da catalase (CAT) variou em função do tempo e da espécie, apresentando uma queda em C. estrellensis aos 16 dias, possivelmente em função de fotoinativação, e um aumento em C. legalis aos 30 dias. Já a atividade da peroxidase do ascorbato (APX) não variou em função do tempo, da espécie ou dos tratamentos. O estudo da plasticidade fenotípica mostrou que C. estrellensis é uma espécie plástica, principalmente em função das variáveis de fotossíntese e trocas gasosas, sendo capaz de sobreviver no gradiente de irradiância testado, o que viabiliza o seu uso em projetos de recuperação de áreas degradadas. E, uma vez que as análises ecofisiológicas mostraram que C. estrellensis e C. legalis apresentaram melhor desempenho em luminosidade moderada, sugere-se que ambas comportaram-se como espécies intermediárias no processo de sucessão florestal. No entanto, uma vez que a concentração de pigmentos foliares e a produção de enzimas antioxidantes inferiram maior susceptibilidade de C. estrellensis à fotoinibição em alta irradiância, sugere-se maior viabilidade do uso de C. legalis em projetos de recuperação de áreas degradas.