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ESTRATÉGIAS DE RESTAURAÇÃO FLORESTAL PARA O SUL DO AMAZONAS
Abstract
Este estudo foi realizado com o objetivo de aplicar conceitos e teorias do conhecimento científico documentado, aliados aos conhecimentos práticos, para desenvolver estratégias de restauração florestal. Ao definir estas estratégias buscamos focar naquelas que tem a maior possiblidade de sucesso quando aplicadas ao contexto do sul do Amazonas. É importante que estas estratégias, aqui apresentadas na forma de “técnicas” sejam testadas, monitoradas e aprimoradas com o intuito de gerar conhecimento sólido que possa ser replicado em outras regiões de contexto similar. Portanto, este estudo é apenas o primeiro passo para aprimorar as técnicas e estratégias de restauração florestal para recuperação de áreas degradadas no Amazonas.
O artigo apresenta a importância das tecnologias agropecuárias para o desenvolvimento rural e a sustentabilidade. Analisa e mostra a importância da cultivar de guaraná BRS Maués como contribuição de tecnologia agropecuária para o desenvolvimento rural no aspecto da geração de renda, preservação do ambiente e da sociobiodiversidade. Para a elaboração do estudo foram utilizadas fontes de informação secundárias bem como entrevistas com agricultores que cultivam guaraná e com lideranças comunitárias. As constatações da pesquisa são de que o Estado Brasileiro foi decisivo para o desenvolvimento de tecnologias e sua respectiva implementação dentro de uma visão e perspectiva de modernização da agricultura. Com a cultura do guaraná não foi diferente. O desenvolvimento de tecnologias, especificamente a da produção da variedade BRS Maués, permitiu aumentar a produtividade, a renda dos agricultores, mantendo o ambiente e a floresta. Contribuiu para o surgimento de um setor industrial que passou a utilizar o guaraná para diversos outros fins, além dos já tradicionais
O histórico de uso do solo é fator determinante da sucessão secundária na Amazônia central, levando ao estabelecimento de comunidades de plantas com estrutura, composição florística, biomassa e dinâmica distintas. A utilização do fogo para renovação de pastagens compromete o potencial regenerativo dessas áreas, que, quando abandonadas, são dominadas pelo gênero Vismia e colonizadas por poucas espécies, resultando em florestas secundárias pouco diversificadas nas quais a sucessão permanece estagnada. Uma vegetação mais rica e dominada pelo gênero Cecropia coloniza áreas com histórico de uso menos intensivo, permitindo o rápido desenvolvimento da sucessão. Embasado nos conhecimentos adquiridos ao longo de duas décadas de estudo, discutimos aspectos práticos relacionados ao potencial e aos custos do manejo da sucessão secundária para a restauração dos serviços ambientais e como forma de aliar a geração de renda à redução do desmatamento na região. O manejo do dossel e os plantios de enriquecimento mostraram-se técnica e economicamente viáveis em capoeiras de Cecropia, mas capoeiras dominadas por Vismia requerem o desenvolvimento de propostas de manejo alternativas para sua restauração. Trabalhos em desenvolvimento pelo Projeto Pioneiras, objetivando investigar as trajetórias sucessionais em regiões distintas da Amazônia e analisar os efeitos das mudanças climáticas sobre as florestas secundárias, são apresentados e discutidos no final.
O presente trabalho teve como objetivo efetuar um levantamento sobre as classificações ecológicas de espécie arbóreas. Uma breve abordagem foi sintetizada sobre o processo de dinâmica sucessional em floresta tropical e dos principais elementos que caracterizam esse processo. Também foi mostrado a existência da grande diversidade de classificações das espécies em grupos ecológicos.
Este guia apresenta informações e fotos de 100 espécies nativas que ocorrem na parte alta da bacia hidrográfica do rio Teles Pires, em Mato Grosso, região que inclui os municípios de Nova Mutum, Nova Ubiratã, Tapurah, Sapezal e Campos de Júlio. Elas são consideradas espécies-chave para a restauração ecológica dos diferentes tipos de vegetação que lá ocorrem, como Cerrado, Floresta Amazônica e as Florestas de Transição entre esses dois Biomas. O guia tem como objetivo ser uma ferramenta de apoio para a identificação e para a produção de sementes e mudas dessas espécies e, dessa forma, contribuir com o processo de adequação ambiental das propriedades rurais da região. Ao final, apresentamos uma explanação sobre o processo de regularização da produção e comercialização de mudas e sementes florestais no Estado de Mato Grosso e as legislações pertinentes, visando estimular a cadeia da restauração ecológica na região.
Past studies have shown that tropical forest regeneration on degraded farmlands is initially limited by lack of seed dispersal, but few studies have tracked changes in abundance and composition of seed rain past the first few years after land abandonment. We measured seed rain for 12 months in 10 6–9-year-old restoration sites and five mature, reference forests in southern Costa Rica in order to learn (1) if seed rain limitation persists past the first few years of regeneration; (2) how restoration treatments influence seed community structure and composition; and (3) whether seed rain limitation is contingent on landscape context. Each restoration site contained three 0.25-ha treatment plots: (1) a naturally regenerating control, (2) tree islands, and (3) a mixed-species tree plantation. Sites spanned a deforestation gradient with 9–89% forest area within 500 m around the treatment plots. Contrary to previous studies, we found that tree seeds were abundant and ubiquitous across all treatment plots (585.1 6 142.0 seeds�m�2�yr�1 [mean 6 SE]), indicating that lack of seed rain ceased to limit forest regeneration within the first decade of recovery. Pioneer trees and shrubs comprised the vast majority of seeds, but compositional differences between restoration sites and reference forests were driven by rarer, large-seeded species. Large, animal-dispersed tree seeds were more abundant in tree islands (4.6 6 2.9 seeds�m�2�yr�1) and plantations (5.8 6 3.0 seeds�m�2�yr�1) than control plots (0.2 6 0.1 seeds�m�2�yr�1), contributing to greater tree species richness in actively restored plots. Planted tree species accounted for ,1% of seeds. We found little evidence for landscape forest cover effects on seed rain, consistent with previous studies. We conclude that seed rain limitation shifted from an initial, complete lack of tree seeds to a specific limitation on large-seeded, mature forest species over the first decade. Although total seed abundance was equal among restoration treatments, tree plantations and tree islands continued to diversify seed rain communities compared to naturally regenerating controls. Compositional differences between regenerating plots and mature forests suggest that large-seeded tree species are appropriate candidates for enrichment planting.
Teoriza-se sobre a importância da restauração como uma ferramenta para a conservação ambiental
através do uso de técnicas nucleadoras capazes de facilitar o processo sucessional em áreas degradadas,
envolvendo organismos produtores, consumidores e decompositores. Esta proposta mostra que o processo
sucessional envolve todos os componentes do ecossistema, onde se destaca a importância dos fragmentos vegetacionais mais próximos das áreas a serem restauradas, de forma a criar uma maior conectividade dentro da paisagem envolvida. São indicadas como técnicas nucleadoras a transposição de solo, poleiros artificiais, coleta de sementes de espécies nucleadoras com manutenção da variabilidade genética, plantio de mudas em ilhas de alta diversidade e transposição de chuva de sementes. As técnicas nucleadoras devem garantir uma maior
conectividade com os fragmentos da região, ropiciando um aumento contínuo da biodiversidade e resiliência
na área degradada, mantendo uma estabilidade dinâmica.
Secondary forests accounted for over one-third (266.000 km 2) of the total deforested area in the Legal Amazon by 2008. This study analyzed the spatial and temporal dynamics of secondary forests in Apuí (AM), Brazil, a municipality in which the expansion of cattle ranching has caused substantial increases in deforestation. A multi temporal series of 10 Landsat TM 5 satellite was classified by the maximum likelihood method in Envi 4.7 software. Mappings were analyzed by logical expressions using Dinamica EGO software, which allowed the extraction of information related to the land cover dynamics in the landscape. It also allowed the evaluation of the methodology employed in the images classification. The results pointed to the intensive land use system established in the region, where deforestation rates were above the average found in the whole Amazon in the last decade. The dynamics of secondary forest was associated temporally to the date of images acquisition and spatially to the local dynamics of pastures expansion and maintenance. The dynamic land use in the region resulted in a large decrease of secondary forests; on average, only 10% of the secondary forests mapped in a year remain in the landscape after six years. The methodology employed in our study was useful for mapping land cover. The use of tools that allowed the overlay of classified images and the extraction of their quantitative information were essential to the refinement and analysis of data, minimizing errors associated with the process of classifying satellite imagery.supervisionada, landscape ecology.
http://dx.doi.org/10.5902/198050988436Este estudo foi realizado no fragmento “Reserva da Biologia”, situado na Universidade Federal de Viçosa, Minas Gerais, (20º35’-28º50’S e 42º45’-43º00’W) onde foram instaladas 10 parcelas de 5 x 5 m interdistantes em 1 m. Foi realizada uma queima controlada nas parcelas instaladas, utilizando a técnica do fogo a favor do vento, obedecendo ao sentido do aclive. O objetivo foi caracterizar o banco de sementes do solo antes e depois do fogo, para verificar os efeitos desse distúrbio na densidade das populações e na composição florística da comunidade vegetal. No centro de cada parcela foi coletada uma amostra de solo de 40 x 25 cm, a partir da superfície da serapilheira até 5 cm de profundidade. Um dia após a coleta das amostras de solos as parcelas foram submetidas à queima controlada. Imediatamente após a queima foram realizadas novas coletas de solo seguindo a mesma metodologia adotada anteriormente. Foram obtidas 528 e 429 sementes germinadas das amostras do banco de sementes do solo antes e após o fogo, respectivamente, pertencentes a 23 espécies de 14 famílias botânicas, sendo as mais representativas Melastomataceae, Asteraceae e Urticaceae. Entre as duas amostragens (antes e após o fogo) não houve redução significativa da riqueza de espécies e a similaridade florística foi de 34 %. Miconia cinnamomifolia e Leandra purpurascens foram as espécies mais abundantes nas duas amostragens. As espécies pioneiras se destacaram com 44 e 40 % das espécies presentes no banco de sementes antes e após o fogo, respectivamente.
http://dx.doi.org/10.5007/2175-7925.2012v25n1p23
A capacidade de perpetuação das espécies de uma floresta depende da viabilidade do banco de sementes e fertilidade do solo. Este trabalho teve como objetivo analisar a estrutura do banco de sementes e as condições do solo como ferramentas para recuperação de uma área perturbada do Parque Municipal do Mocambo de Patos de Minas, MG. O local foi dividido em três áreas sendo que, em cada área, foram selecionadas aleatoriamente nove parcelas de 10x30m (300m2) e em cada uma dessas parcelas foram coletadas amostras de solo em três pontos e três profundidades diferentes. A metade destas amostras foi mantida sobre a irradiação de luz e o restante no escuro. Uma amostra do solo de cada área foi coletada para se verificar a fertilidade do solo. Observou-se dominância de espécies herbáceas pioneiras nas emergências. O maior índice de emergência foi encontrado na profundidade de 0 a 10cm. O solo mostrou-se com deficiência em potássio e fósforo, sendo que nos demais nutrientes analisados os valores encontravam-se muito bons. Conclui-se que, em longo prazo, essa área consiga se regenerar naturalmente, e é possível também acelerar esse processo com a introdução de espécies nativas e de dispersores naturais.
Resumo -Em função de questões legais e ambientais, a restauração de áreas degradadas tem se concentrado principalmente no ambiente ciliar. Apesar das matas ciliares estarem protegidas pela legislação há quase meio século, grande parte dessas florestas foram degradadas de forma semelhante ao que ocorreu com as outras formações naturais. Nas últimas décadas, o aumento da fiscalização e das punições levaram a um aumento na conservação e restauração das formações ciliares. A percepção de que era necessário ampliar e aprofundar o conhecimento científico disponível sobre a recuperação dessas áreas estimulou o incremento de pesquisas nas matas ciliares, nas mais diferentes áreas do conhecimento. Hoje, dispõe-se de muito conhecimento científico sobre vários aspectos das características do meio físico das matas ciliares, como geomorfologia, solos e hidrologia, e também sobre as comunidades biológicas aí existentes. Estes conhecimentos incluem aspectos como a composição florística, a estrutura fitossociológica, a fenologia e a dinâmica dessas vegetações. Também a fauna tem sido estudada. Este artigo apresenta sucintamente a metodologia atualmente empregada pelo Laboratório de Ecologia e Restauração Florestal (LERF) da Universidade de São Paulo para a recuperação de áreas degradadas. Termos para indexação: Adequação ambiental, restauração florestal, matas ciliares, Laboratório de Ecologia e Restauração Florestal, legislação ambiental.
Wetlands are valuable ecosystems because they harbor a huge biodiversity and provide key services to societies. When natural or human factors degrade wetlands, ecological restoration is often carried out to recover biodiversity and ecosystem services (ES). Although such restorations are routinely performed, we lack systematic, evidence-based assessments of their effectiveness on the recovery of biodiversity and ES. Here we performed a meta-analysis of 70 experimental studies in order to assess the effectiveness of ecological restoration and identify what factors affect it. We compared selected ecosystem performance variables between degraded and restored wetlands and between restored and natural wetlands using response ratios and random-effects categorical modeling. We assessed how context factors such as ecosystem type, main agent of degradation, restoration action, experimental design, and restoration age influenced post-restoration biodiversity and ES. Biodiversity showed excellent recovery, though the precise recovery depended strongly on the type of organisms involved. Restored wetlands showed 36% higher levels of provisioning, regulating and supporting ES than did degraded wetlands. In fact, wetlands showed levels of provisioning and cultural ES similar to those of natural wetlands; however, their levels of supporting and regulating ES were, respectively, 16% and 22% lower than in natural wetlands. Recovery of biodiversity and of ES were positively correlated, indicating a win-win restoration outcome. The extent to which restoration increased biodiversity and ES in degraded wetlands depended primarily on the main agent of degradation, restoration actions, experimental design, and ecosystem type. In contrast, the choice of specific restoration actions alone explained most differences between restored and natural wetlands. These results highlight the importance of comprehensive, multi-factorial assessment to determine the ecological status of degraded, restored and natural wetlands and thereby evaluate the effectiveness of ecological restorations. Future research on wetland restoration should also seek to identify which restoration actions work best for specific habitats.
Considering its potential use in degraded environments, this study characterized the composition of a seed bank obtained from an area of typical secondary succession on the Federal University of Viçosa campus. Inferences were made whether this indicator reflects future sustainability, given the seed bank's potential for revegetating degraded sites. Its floristic composition was compared with indices obtained in other similar seed bank studies. The specific site is located at the Mata da Garagem woods, a 40-year old forest fragment covering a low ridge parallel to a campus roadway. Twenty seed bank samples were collected from randomly selected points, each sample consisting of four subsamples. The experiment was installed on the campus nursery using 20 wooden boxes (50x50x15cm). After 90 days, 508 individual plants were counted, and 38 species were identified, as belonging to 34 genera distributed among 22 families. The diversity index (H') is 2.11; whereas the equability (J) value of 0.67 is considered high compared to other seed bank studies. Cecropia hololeuca (28.9%) and Solanum erianthum (18,7%) are indicated as the most important species within the forest regeneration process. Results suggest that the seed bank studied indeed has the potential for promoting and guaranteeing an ecological succession process dynamics on degraded lands of similar ecosystems.
The Y Ikatu Xingu Campaign brought together indigenous people, farmers, researchers, governmental, and non-governmental organizations seeking riparian forest restoration in the Xingu watershed, in west-central Brazil. Forest restoration is challenging in the region because of scarce nurseries, long distances, and high costs associated with the usual technique of planting nursery-raised seedlings. This article describes mechanized direct seeding and compares it with the planting of seedlings, in terms of cost and tree densities at ages of 0.5 until 5.5 yr after planting. Direct-seeding was mechanized using common agricultural machines designed for sowing cereals or grasses, which were loaded with 200,000 seeds of native trees and 150,000 seeds of annual and sub-perennial legumes, plus 50–150 kg sand ha−1. The Campaign restored more than 900 ha by direct-seeding and 300 ha by planting seedlings. The great demand for native seeds was met by the Xingu Seed Network, formed by Indians, small landholders, and peasants, which commercialized 98 tons of native seeds and earned US1,845 ha−1 against US$5,106 ha−1), results in higher tree densities (2,500–32,250 trees ha−1 against 1,500–1,650 trees ha−1), is more practical, and creates layers of dense vegetation that better resembles natural forest succession.
Birds both promote and prosper from forest restoration. The ecosystem functions birds perform can increase the pace of forest regeneration and, correspondingly, increase the available habitat for birds and other forest-dependent species. The aim of this study was to learn how tropical forest restoration treatments interact with landscape tree cover to affect the structure and composition of a diverse bird assemblage. We sampled bird communities over two years in 13 restoration sites and two old-growth forests in southern Costa Rica. Restoration sites were established on degraded farmlands in a variety of landscape contexts, and each included a 0.25-ha plantation, island treatment (trees planted in patches), and unplanted control. We analyzed four attributes of bird communities including frugivore abundance, nectarivore abundance, migrant insectivore richness, and compositional similarity of bird communities in restoration plots to bird communities in old-growth forests. All four bird community variables were greater in plantations and/or islands than in control treatments. Frugivore and nectarivore abundance decreased with increasing tree cover in the landscape surrounding restoration plots, whereas compositional similarity to old-growth forests was greatest in plantations embedded in landscapes with high tree cover. Migrant insectivore richness was unaffected by landscape tree cover. Our results agree with previous studies showing that increasing levels of investment in active restoration are positively related to bird richness and abundance, but differences in the effects of landscape tree cover on foraging guilds and community composition suggest that trade-offs between biodiversity conservation and bird-mediated ecosystem functioning may be important for prioritizing restoration sites.
Active forest restoration typically involves planting trees over large areas; this practice is costly, however, and establishing homogeneous plantations may favour the recruitment of a particular suite of species and strongly influence the successional trajectory. An alternative approach is to plant nuclei (islands) of trees to simulate the nucleation model of succession and accelerate natural recovery.
We evaluated natural tree recruitment over 4 years in a restoration study replicated at eight former pasture sites in the tropical premontane forest zone of southern C osta R ica. At each site, two active restoration strategies were established in 50 × 50 m plots: planting trees throughout, and planting different‐sized tree islands (4 × 4, 8 × 8, 12 × 12 m) within the plot. Restoration plots were compared to similar‐sized controls undergoing passive restoration. Sites were spread across c . 100 km ² and distributed along a gradient of surrounding forest, allowing us to compare the relative importance of adjacent forest to that of within‐site treatment on tree recruitment.
Recruitment of animal‐dispersed tree species was more than twofold higher in active (μ = 0·45 recruits m ⁻² ) as compared to passive restoration; recruitment was equivalent in plantation and island treatments, even though only 20% of the area in island plots was planted originally. The majority of recruits (>90%) represented early successional species ( n = 54 species total).
Density of animal‐dispersed recruits was greater in large (0·80 ± 0·66 m ⁻² ) than small (0·28 ± 0·36 m ⁻² ) islands and intermediate in medium‐sized islands. Seedling recruitment (<1 m tall) was greater in the interior of islands as compared to plantations, whereas sapling recruitment was similar, suggesting that island interiors may develop greater density of woody recruits as succession proceeds.
Surrounding forest cover did not influence density or species richness of recruits among sites, although this factor may become more important over time.
Synthesis and applications . Applied nucleation is a promising restoration strategy that can accelerate forest recovery to a similar degree as plantation‐style restoration but is more economical. Appropriate island size is on the order of c . 100 m ² . Practitioners should consider the methodology as an alternative to large‐scale plantings.
THE "ROÇAS DE CABOCLOS" are the slash-and-burn agricultural units of traditional populations dwelling in the lowlands of the Brazilian Tropics, generally in association with forests. They are derived from the indigenous system with some modifications introduced by the Africans and Portuguese. In this paper we analyse the community structure of the "roças" and the role of biological and cultural factors in maintaining and augmenting the genetic variability in the most important species planted in roças, the cassava (Manihot esculenta). There is a high degree of diversity in the "roças" and the several species that are normally present, like cassava, sweet-potato, yams, arrowroot, ariá, cupá and peanuts present what has been called ecological combining ability, meaning that they optimize their use of environmental factors and resources by minimizing the overlap of their architectures. The variability of cassava is amplified by the seed bank in previously occupied sites, interspecific crossings and intervarietal crossings facilitated by the planting arrangements chosen by the "caboclos". After being created, the variability is fixed through vegetative cloning, the usual reproduction method not only of cassava, but also of the other species of the "roça", mostly perennial and showing "agronomical disjuntion", that is, reproduction and production effected by different organs of the plant.
Este trabalho teve por objetivos identificar e avaliar a agressividade potencial das plantas daninhas em um agrossistema com leguminosas herbáceas anuais como cobertura de solo. Foram plantadas, nas ruas de um sistema de aléias de sombreiro (Clitoria fairchildiana) e no final do período agrícola, as leguminosas mucuna-preta, feijão-guandu, feijão-de-porco e calopogônio, em sistema de blocos ao acaso com cinco repetições. Para estudo da dinâmica da composição florística, avaliaram-se a freqüência, densidade, dominância, similaridade, diversidade de espécies e biomassa das plantas daninhas. Foram identificadas 42 espécies de plantas espontâneas, das quais as mais freqüentes e de maior densidade e dominância foram Leptochoa virgata, Panicum laxum e Sida sp. Não foram detectadas diferenças significativas para densidade, número de espécies, diversidade e biomassa entre as plantas daninhas emergidas nos quatro tratamentos com leguminosas; nem destas em relação ao controle.This study evaluated the efficiency of cover legumes in suppressing weed. A field experiment was arranged in a randomized block design with five replications in an alley cropping system, using Clitoria fairchildiana and four cover species, Mucuna aterrima, Cajanus cajan, Canavalia ensiformes and Calopogonium mucunoides. Weed frequency, density, diversity and biomass were evaluated with 42 weed species being identified. The most frequent and presenting the highest density and dominance were Leptochoa virgata, Panicum laxum and Sida sp. No significant differences were detected in density, number of species, diversity and biomass among the four legumes, nor between them and the control.
The aim of this study was to gather information on timber trees occurring in a non-flooded forest near Manaus and to make an attempt to rank these species according to their succession in the forest. The ranking would be helpful in modeling the forest's dynamics, for forest conservation, management and rehabilitation of degraded areas. The group studied was formed by 60 botanical species belonging to 42 genera and 18 families. In a general view, seed size was >0.5cm3 (69% of the species), seed dispersal by animals predominated (60%), germination occurred within a period of up to 3 months (69%) and wood density was high (>0.8 g/cm3 in 52%). However the set of characteristics did not permit a clear ranking of all species, as characteristics thought to be typical for pioneer or climax occurred together on the same species in 24 of the selected trees (40%). Wood density and fruiting regularity showed to be of little use for classification, as well as the presence of seed dormancy, as dormancy was detected in all successional groups. On the other hand, a distinction between the various types of seed dormancy was helpful to separate the groups. The following seed related characteristics may be recommended for classification: dispersal type, reserve quantity, desiccation tolerance and dormancy types. The attempt of ranking the timber species according to their role in natural succession showed that most had a set of characteristics typical of mature forest. Only a few species had earlier successional characteristics, and probably have higher resistance to forest disturbance.
We tested alternative hypotheses concerning factors affecting early forest succession and community composition in deforested and abandoned areas invaded by an exotic grass, Saccharum spontaneum , in Panama. We hypothesized three barriers to natural regeneration: (1) Saccharum competition, (2) seed dispersal limitations, and (3) fire. We measured natural tree and shrub regeneration in a factorial experiment combining distances from adjacent forest, mowing treatments of the Saccharum, and a prescribed burn. To determine the applicability of the general model of neotropical succession and the nucleation model of succession to species composition of forest regeneration in these anthropogenic grasslands in Panama the effect of time since fire and distance to remnant vegetation (isolated trees, shrubs, and large monocots) was measured. Fire significantly affected species composition and decreased species richness because most species had either their resprouting ability or seed germination inhibited by fire; the few species that had regeneration enhanced by fire dominated early successional commu- nities. Sites differed in time since fire, ranging from 1 to 4 yr; the interaction of site and distance from the forest significantly affected community composition and the prevalence of species with different dispersal mechanisms and shade tolerance. At recently burned sites, light-dependent wind-dispersed species predominated; most were found near the forest edge. As time since fire increased, significantly more shade-tolerant, larger-animal-dispersed species were recorded, and the proximity to and species identity of remnant vegetation became more important in affecting species composition of the natural regeneration; no significant effect of distance from the forest was found at sites that were unburned for three or more years. Our results support both successional models; the temporal sequence of species composition corresponded to later stages of the general model, while the spatial distribution of species followed the nucleation model. Our results highlight the importance of effective seed dispersal in structuring successional species composition and distribution and in regaining lost diversity resulting from frequent fires in the Saccharum.
The failure of most efforts undertaken to restore natural high-diversity tropical forests, like the Atlantic Forest, has resulted in a very intense round of discussions on the science and best-practice of ecological restoration in the state of São Paulo, southeastern Brazil. This culminated in the participatory elaboration of a state resolution concerning technical and orientation aspects for restoration activities, which has been reviewed and updated periodically in workshops that bring together more than 200 professionals. The aim of this resolution was to maximize the establishment of biologically viable forests, with plant richness consistent with the reference ecosystem, to ensure the persistence of restored forests and protect native biodiversity. The contributions of this resolution for the improvement and stimulation of restoration actions are evident today. Between 2003 and 2008, when the resolution was heavily discussed, seedling production of native shrubs and trees in the state increased from 13,000,000 (55 nurseries) to 33,000,000 (114 nurseries) per year, and average number of plant species produced in nurseries also increased from 30 to over 80, reflecting the increase of restoration actions. In our view, the existing legal instrument has served well as a mechanism to accompany environmental public policy aimed at protection of the collective interests of society. In particular, it guides and orients the bulk of investments in ecological restoration and enhances the prospects for maximizing the societal benefits that can and should be obtained from restoration activities, including the persistence of biodiversity in human-modified tropical landscapes.
El término "áreas degradadas" es utilizado normalmente para definir las áreas de bosques secundarios en la Amazonía brasileña. El gobierno y las iniciativas privadas han propuesto las plantaciones mecanizadas de granos, especialmente la soya, el maíz y el arroz, como alternativa de aprovechamiento de estas áreas, consideradas degradadas e improductivas. En este trabajo fue realizado un análisis sobre la importancia de las áreas de bosques secundarios en la Amazonía, mostrando su valor del punto vista ecológico, social y económico, además de los impactos de su sustitución por plantaciones mecanizadas.
Restoring small-scale habitat heterogeneity in highly diverse systems, like tropical forests, is a conservation challenge and offers an excellent opportunity to test factors affecting community assembly. We investigated whether (1) the applied nucleation restoration strategy (planting tree islands) resulted in higher habitat heterogeneity than more homogeneous forest restoration approaches, (2) increased heterogeneity resulted in more diverse tree recruitment, and (3) the mean or coefficient of variation of habitat variables best explained tree recruitment. We measured soil nutrients, overstory and understory vegetation structure, and tree recruitment at six sites with three 5- to 7-year-old restoration treatments: control (no planting), planted tree islands, and conventional, mixed-species tree plantations. Canopy openness and soil base saturation were more variable in island treatments than in controls and plantations, whereas most soil nutrients had similar coefficients of variation across treatments, and bare ground was more variable in control plots. Seedling and sapling species density were equivalent in plantations and islands, and were substantially higher than in controls. Species spatial turnover, diversity, and richness were similar in island and plantation treatments. Mean canopy openness, rather than heterogeneity, explained the largest proportion of variance in species density. Our results show that, whereas canopy openness and soil base saturation are more heterogeneous with the applied nucleation restoration strategy, this pattern does not translate into greater tree diversity. The lack of a heterogeneity-diversity relationship is likely due to the fact that recruits respond more strongly to mean resource gradients than variability at this early stage in succession, and that seed dispersal limitation likely reduces the available species pool. Results show that planting tree islands facilitates tree recruitment to a similar degree as intensive plantation-style restoration strategies.
Tropical land cover change has negatively affected numerous migratory bird populations. Forest restoration can augment migrant wintering habitat. However, almost no information exists about factors that influence migrant use of tropical restoration sites. We sampled migrant birds in young restoration sites in Costa Rica from February 2006 to April 2008 to determine how vegetation height, planting design, season, and landscape forest cover influenced capture rates of four declining species. We also documented total numbers of migratory species and individuals captured in each planting design treatment; each site had a control treatment where seedlings were not planted, an island treatment where seedlings were planted in patches, and a plantation treatment where seedlings were planted to cover the entire area. Sites varied in landscape forest cover within 500 m buffers. Three out of four focal species were captured significantly more often in plantation treatments than island or control treatments. Two of the four species showed seasonal patterns and one species was captured more often in high-vegetation sites. Greater numbers of species and individuals were captured in plantation treatments compared to island and control treatments. The plantation planting design increased migrant use more quickly than the island planting design. When resources are available, we recommend planting plantation-style to rapidly increase the value of restoration sites to a range of species, particularly those that use woody vegetation. When resources are more limited, planting islands may be a cost-effective, although not as ecologically effective, alternative that supports a diversity of migrant species compared to unplanted controls.
After tropical lands have been abandoned from anthropogenic pressures, often forest structure and some species recover naturally. Studies suggest, however, that mature-forest species are frequently slow to establish and an active management strategy may be necessary. We tested direct seeding of mature-forest species as a restoration strategy in sites previously used for slash-and-burn agriculture in semi-evergreen, seasonal forest in the Yucatan peninsula, Mexico, and evaluated when in the successional process this strategy had the highest success rate. We planted three mature-forest species (Brosimum alicastrum, Enterolobium cyclocarpum, and Manilkara zapota) in three forest ages: recently abandoned (<5 years), young successional forest (8–15 years), and reference forest (>50 years). Overall, an average of 5–41% of planted seeds germinated, and 3–35% were present through the seedling stage. Only M. zapota had higher germination in the reference forest than in the other forest ages, whereas the other two species had similar percentage germination in all successional stages. Of the seeds that germinated in the 8–15 years sites and the reference forest, 58–95% of the seedlings survived through the end of the study, whereas survival in recently abandoned sites was less than 50% in most cases. Seedling height was generally similar across forest age categories. Our results suggest that direct seeding these mature-forest species after the first few years of natural succession could be a successful strategy to accelerate and guarantee their establishment.
a b s t r a c t Given the extent of land use and land cover change by humans on a global scale, conservation efforts have increasingly focused on restoring degraded ecosystems to provide ecosystem services and biodiversity. Many examples in the tropics and elsewhere, however, show that some ecosystems recover rapidly without human intervention which begs the question of in which cases and to what extent humans should actively work to facilitate ecosystem recovery. We recommend that all land managers consider a suite of ecological and human factors before selecting a restoration approach. Land managers should first consider what the likely outcome of a passive restoration (natural regeneration) approach would be based on the natural ecosystem resilience, past land-use history, and the surrounding landscape matrix. They should also identify the specific goals of the project and assess the resources available. Conducting these analyses prior to selecting restoration approaches should result in a more efficient use of restoration resources both within and among projects and should maximize the success of restoration efforts.
INTRODUÇÃO As formações vegetais ciliares têm sido submetidas a diversos impactos antrópicos. Para o Conselho Nacional do Meio Ambiente, estas áreas são alvo de preservação permanente, fazendo-se então necessário, intervenções restaurativas onde ocorra a restituição o mais próximo possível da condição original, fazendo com que a sucessão natural se expresse e recrie comunidades naturais, cujos processos ecológicos se baseiam na estabilidade e resiliência (Três et al., 2006). Neste contexto, conceitos de nucleação, defendidos pioneiramente por Yarranton & Morrison (1974) podem ser efetivos. Entre as práticas nucleadoras estruturadas a partir do conceito original, cogitam-se os poleiros secos como uma ferramenta importante e barata na atração dos dispersores à área a ser restaurada, contribuindo para a chegada de propágulos (Zucca & Castro, 2006). O poleiro seco pode ser feito de taquaras com suas ramificações laterais, enterradas perpendicularmente ao solo, imitando galhos secos de árvores para a utilização por aves como locais de descanso e forrageamento, onde possam defecar ou regurgitar sementes, incrementando o banco de sementes e plântulas local (Reis et al.; 2003). Considerando-se que nos trópicos cerca de 95% das espécies arbóreo-arbustivas apresentam recursos adaptados ao consumo por animais (Howe & Westley, 1988) e que as aves são consideradas importantes agentes de transporte de sementes (Krieck, et al., 2006), o uso de ferramentas atrativas para este tipo de dispersor a ambientes ciliares degradados pode ser um aliado no processo restaurativo.
Vegetation, seed rain, seed germination, microclimate, and soil physical and chemical parameters were measured in a recently abandoned pasture and adjacent primary rain forest in southern Costa Rica. The goal of this study was to assess the importance of these factors in limiting forest regeneration in abandoned pastures. Seed rain of animal dispersed species decreased dramatically in the pasture >5 m from the forest/pasture edge; fewer wind dispersed seeds fell in the pasture than in the forest, but the difference was much less than for animal dispersed seeds. Percent seed germination of most species studied was similar in the forest and in pasture with grasses; seed germination was lower during the dry season in areas of pasture cleared of grasses. Air temperature, vapor pressure deficit (VPD), and photon flux density (PFD) were much higher in the pasture than in the forest at 1 m above the ground. VPD and PFD at ground level and soil temperature were similar in the pasture and the forest, indicating that pasture grasses strongly modify microclimatic conditions near the soil surface. The lowest gravimetric water content recorded in the pasture during the dry season was 0.5 and leaf relative water contents of the two species measured in the forest and pasture were identical, suggesting that plants in the pasture were not water stressed. Levels of most soil nutrients were lower in the pasture as compared to the forest; however, aboveground and root biomass for seedlings grown in pasture and forest soils did not differ significantly. Although a number of factors impede forest recovery in abandoned pastures, these results suggest that the most important limitation is lack of seed dispersal.
Planting tree seedlings in small patches (islands) has been proposed as a method to facilitate forest recovery that is less expensive than planting large areas and better simulates the nucleation process of recovery. We planted seedlings of four tree species at 12 formerly agricultural sites in southern Costa Rica in two designs: plantation (entire 50 × 50 m area planted) and island (six patches of three sizes). We monitored seedling survival, height, and canopy area over 3 years. To elucidate mechanisms influencing survival and growth, we measured soil and foliar nutrients, soil compaction, and photosynthesis. Survival of all species was similar in the two planting designs. Seedling height and canopy area were greater in plantations than islands at most sites, and more seedlings in islands decreased in height due to damage incurred during plot maintenance. Survival, height, and canopy area were both site- and species-specific with the two N-fixing species (Inga edulis and Erythrina poeppigiana) greater than the other species (Terminalia amazonia and Vochysia guatemalensis). Foliar N was higher in Terminalia and Vochysia in sites where Inga growth was greater. Soil nutrients, however, explained a small amount of the large differences in growth across sites. Leaf mass per area was higher in islands, and P use efficiency was higher in plantations. Our results show advantages (good seedling survival, cheaper) and disadvantages (more seedling damage, slightly lower growth) to the island planting design. Our study highlights the importance of replicating restoration strategies at several sites to make widespread management recommendations.
In degraded tropical pastures, active restoration strategies have the potential to facilitate forest regrowth at rates that are faster than natural recovery, enhancing litterfall, and nutrient inputs to the forest floor. We evaluated litterfall and nutrient dynamics under four treatments: plantation (entire area planted), tree islands (planting in six patches of three sizes), control (same age natural regeneration), and young secondary forest (7–9-yr-old natural regeneration). Treatments were established in plots of 50 × 50 m at six replicate sites in southern Costa Rica and the annual litterfall production was measured 5 yr after treatment establishment. Planted species included two native timber-producing hardwoods (Terminalia amazonia and Vochysia guatemalensis) interplanted with two N-fixing species (Inga edulis and Erythrina poeppigiana). Litter production was highest in secondary forests (7.3 Mg/ha/yr) and plantations (6.3), intermediate in islands (3.5), and lowest in controls (1.4). Secondary forests had higher input of all nutrients except N when compared with the plantation plots. Inga contributed 70 percent of leaffall in the plantations, demonstrating the influence that one species can have on litter quantity and quality. Although tree islands had lower litterfall rates, they were similar to plantations in inputs of Mg, K, P, Zn, and Mn. Tree islands increased litter production and nutrient inputs more quickly than natural regeneration. In addition to being less resource intensive than conventional plantations, this planting design promotes a more rapid increase in litter diversity and more spatial heterogeneity, which can accelerate the rate of nutrient cycling and facilitate forest recovery.
Extensive areas of the tropics have been converted into pasture for cattle ranching. Frequently, abandoned pasture does not revert to forest. The goal of this project was to identify barriers to lowland moist forest regeneration in highly degraded grasslands in the Sierra Nevada de Santa Marta, Colombia. The barriers we considered were seed source, seed predation, competition with grasses, microclimate and soil limitations on plant growth, and fire. Seed dispersal into the grasslands is limited to within 10 meters of forest fragments, but this barrier can be overcome by sowing seeds and planting seedlings and by establishing perches to attract dispersers. In these degraded grasslands, seed predation was lower than in the adjacent forest patches, and there was no evidence that grasses inhibited the establishment of woody species. The most important barrier was the severe degradation of the soils. In much of the area, the A and B horizons have been eroded away, leaving saprolite at the soil surface. Seedlings of two fast-growing pioneer species, Ochroma pyramidale and Cochlospermum vitifolium, grew to a maximum height of only 2.5 and 12 cm, respectively, during the first eight months. The slow plant growth in the degraded grassland soils compared to forest soils was associated with lower levels of cation-exchange capacity, calcium, magnesium, and potassium. Even if these barriers could be overcome, the frequent and extensive use of fire in the region must be controlled to avoid killing established woody plants.
Tropical forests are being cleared at an alarming rate although our understanding of their ecology is limited. It is therefore essential to design restoration experiments that both further our basic knowledge of tropical ecology and inform management strategies to facilitate recovery of these ecosystems. Here we synthesize the results of research on tropical montane forest recovery in abandoned pasture in Costa Rica to address the following questions: (1) What factors limit tropical forest recovery in abandoned pasture? and (2) How can we use this information to design strategies to facilitate ecosystem recovery? Our results indicate that a number of factors impede tropical forest recovery in abandoned pasture land. The most important barriers are lack of dispersal of forest seeds and seedling competition with pasture grasses. High seed predation, low seed germination, lack of nutrients, high light intensity, and rabbit herbivory also affect recovery. Successful strategies to facilitate recovery in abandoned pastures must simultaneously overcome numerous obstacles. Our research shows that establishment of woody species, either native tree seedlings or early-successional shrubs, can be successful in facilitating recovery, by enhancing seed dispersal and shading out pasture grasses. On the contrary, bird perching structures alone are not an effective strategy, because they only serve to enhance seed dispersal but do not reduce grass cover. Remnant pasture trees can serve as foci of natural recovery and may enhance growth of planted seedlings. Our results highlight the importance of: (1) understanding the basic biology of an ecosystem to design effective restoration strategies; (2) comparing results across a range of sites to determine which restoration strategies are most generally useful; and (3) considering where best to allocate efforts in large-scale restoration projects.
Question
What is the relative contribution of geographic distance, soil and topographic variables in determining the community floristic patterns and individual tree species abundances in the nutrient‐poor soils of central Amazonia?
Location
Central Amazonia near Manaus, Brazil.
Methods
Our analysis was based on data for 1105 tree species (≥ 10 cm dbh) within 40 1‐ha plots over a ca. 1000‐km ² area. Slope and 26 soil‐surface parameters were measured for each plot. A main soil‐fertility gradient (encompassing soil texture, cation content, nitrogen and carbon) and five other uncorrelated soil and topographic variables were used as potential predictors of plant‐community composition. Mantel tests and multiple regressions on distance matrices were used to detect relationships at the community level, and ordinary least square (OLS) and conditional autoregressive (CAR) models were used to detect relationships for individual species abundances.
Results
Floristic similarity declined rapidly with distance over small spatial scales (0–5 km), but remained constant (ca. 44%) over distances of 5 to 30 km, which indicates lower beta diversity than in western Amazonian forests. Distance explained 1/3 to 1/2 more variance in floristics measures than environmental variables. Community composition was most strongly related to the main soil‐fertility gradient and C:N ratio. The main fertility gradient and pH had the greatest impact of species abundances. About 30% of individual tree species were significantly related to one or more soil/topographic parameters.
Conclusions
Geographic distance and the main fertility gradient are the best predictors of community floristic composition, but other soil variables, particularly C:N ratio, pH, and slope, have strong relationships with a significant portion of the tree community.
With the increasing need to restore former agricultural lands worldwide and in the tropics, in particular, it is critical to explore different models for how to restore these lands in a cost-effective manner which best simulates natural forest recovery and provides for human livelihoods. We propose that agro-successional restoration, which we define as incorporating a range of agroecology and agroforestry techniques as a transition phase early in forest restoration, could be used more widely to overcome socioeconomic and ecological obstacles to restoring these lands. Over centuries, farmers and scientists have developed various agroforestry techniques that aim to cultivate crops and trees, in a range of crop types, time periods of cultivation (a few years to several decades), and complexity of species planted. The management practices used in these systems, such as weeding and increasing soil fertility, parallel those used in many forest restoration efforts. The synergism between these approaches is evidenced by many existing agro-successional examples currently used by smallholders in the tropics. Benefits of the agro-successional model include extending the management period of restoration, offsetting some management costs, providing food security for small landholders, and involving small landholders in the restoration process.
Planting native tree seedlings is the predominant restoration strategy for accelerating forest succession on degraded lands. Planting tree "islands" is less costly and labor intensive than establishing larger plantations and simulates the nucleation process of succession. Assessing the role of island size in attracting seed dispersers, the potential of islands to expand through enhanced seed deposition, and the effect of planting arrangements on seed dispersal by birds and bats informs restoration design. Determining the relative importance of local restoration approach vs. landscape-level factors (amount of surrounding forest cover) helps prioritize methods and locations for restoration. We tested how three restoration approaches affect the arrival of forest seeds at 11 experimental sites spread across a gradient of surrounding forest cover in a 100-km2 area of southern Costa Rica. Each site had three 50 x 50 m treatments: (1) control (natural regeneration), (2) island (planting tree seedlings in patches of three sizes: 16 m2, 64 m2, and 144 m2), and (3) plantation (planting entire area). Four tree species were used in planting (Terminalia amazonia, Vochysia guatemalensis, Erythrina poeppigiana, and Inga edulis). Seed rain was measured for 18 months beginning approximately 2 years after planting. Plantations received the most zoochorous tree seeds (266.1 +/- 64.5 seeds x m(-2) x yr(-1) [mean +/- SE]), islands were intermediate (210.4 +/- 52.7 seeds x m(-2) x yr(-1)), and controls were lowest (87.1 +/- 13.9 seeds x m(-2) x yr(-1)). Greater tree seed deposition in the plantations was due to birds (0.51 +/- 0.18 seeds x m(-2) x d(-1)), not bats (0.07 +/- 0.03 seeds x m(-2) x d(-1)). Seed rain was primarily small-seeded, early-successional species. Large and medium islands received twice as many zoochorous tree seeds as small islands and areas away from island edges, suggesting there is a minimum island size necessary to increase seed deposition and that seed rain outside of planted areas is strongly reduced. Planting design was more important for seed deposition than amount of forest cover within the surrounding 100- and 500-m radius areas. Establishing plantations and large islands facilitates the arrival of early-successional tree seeds and represents a broadly applicable strategy for increasing seed rain on abandoned agricultural lands. However, more intensive restoration approaches may be necessary for establishment of dispersal-limited species.
Este trabalho trata da recuperação de áreas degradadas pela mineração da fração argila em Doutor Pedrinho-SC. O estudo utilizou técnicas para integrar o solo, as plantas e os animais. Testaram-se dois níveis de topografia, regular e irregular, dois níveis de adubação, orgânica e química, e dois níveis de serapilheira, com e sem. A espécie arbórea selecionada foi a leguminosa Mimosa scabrella (bracatinga). Poleiros artificiais foram instalados na área a fim de incrementar o número de sementes provenientes de áreas vizinhas pelos devidos dispersores. Aos nove meses de avaliação, a partir das análises químicas de solo, não foram verificados incrementos nutricionais. A bracatinga apresentou índice de sobrevivência superior a 92%, enquanto que a cobertura do solo pela copa das árvores foi significativamente superior para os tratamentos que receberam serapilheira, com valores maiores de 67%. Apesar de a cobertura do solo pela revegetação natural não apresentar diferença, em geral, houve tendência da mesma ser maior nos tratamentos com topografia regular. Os poleiros artificiais foram responsáveis pela vinda de vinte e uma sementes pertencentes a seis morfoespécies distintas. Entre as doze famílias botânicas de plantas espontâneas identificadas, a maior parte apresentou síndrome de polinização zoofilica, dispersão de sementes anemocórica e hábito herbáceo. Conclui-se que a bracatinga, a abubação orgânica e/ou química, a serapilheira e os poleiros artificiais são indicados para utilização em programas de recuperação de áreas degradadas semelhantes ao deste estudo. Estudos complementares são necessários para avaliar a pertinência ou não do uso da topografia irregular em programas de recuperação de áreas degradadas
Land-use practices can dramatically shift the trajectories of rain forest recovery. In a 25-year study, Amazon rain forest
regenerated following deforestation as long as seed availability and seedling recruitment were not interrupted. In contrast,
rain forest converted to cattle pastures via cutting and burning prior to abandonment diverted succession, leading to highly
simplified stands dominated by a single genus. Annual fires eliminated seedlings, saplings, coppice, and seeds in the soil,
except for several Vismia species. Once established, Vismia regenerated by continual resprouting and resisted the establishment
of other rain forest species, especially the normal suite of pioneers. Through time, succession both in abandoned clearcuts
and pastures increased in stem density and biomass; however, species accumulation and ecosystem services were limited in pastures
when compared with those in abandoned clearcuts. Therefore, prescribed burning to maintain pastureland leaves a legacy that
is not readily extinguished, whereas abandoning clearcuts engenders an accelerated rain forest regeneration.
The article discusses the economic dimension of ecological restoration drawing on experiences in the Brazilian Atlantic forest, which is one of the most biodiverse ecosystems on the planet and also one of the richest in endemism. The looming land crisis has been receiving increasing attention worldwide. In this context, forest restoration could be seen as just another factor in the demand for land, with the potential to reduce food production, increase food prices and have other unwanted consequences. Centuries of deforestation and forest degradation have compromised the delivery of ecosystem services and the production of forest goods in the Atlantic forest. Nevertheless, the region presents a huge opportunity for new approaches to ecological restoration and for establishing forest restoration as an economically viable practice. The Atlantic forest has been exploited to the point where it no longer supplies significant quantities of timber.
If tropical farmers cannot be provided with sustainable land-use systems, which address their subsistence needs and keep them gainfully employed, tropical forests will continue to disappear. We looked at the abil- ity of economic land-use diversification – with reforestation of tropical “wastelands” as a key activity – to halt deforestation at the farm level. Our ecological–economic concept, based on land-use data from the buffer area of the Podocarpus National Park in southern Ecuador, shows that stopping deforestation after 10 years is possible without violating subsistence demands. Tropical, farm-level diversification may not only reduce total deforestation by 45%, but also increase farmers’ profits by 65%, because the formerly unpro- ductive wastelands have been returned to productive land use. We therefore conclude that a “win–win” sce- nario is possible: the subsistence needs of people can be reconciled with conservation objectives. However, inexpensive microcredits (at interest rates below 6%) and experience on alternative land-use opportunities must be offered to farmers.
Background: In central Amazonia, previous low intensity land use engenders succession dominated by Cecropia spp. which proceeds at high rates; however, at higher intensity of use succession is arrested and dominated by Vismia spp. over the long-term. Factors driving these two successional pathways are unknown.Aims: We aim to elucidate seedling growth under the two alternative successional pathways.Methods: We experimentally determined the effects of successional age and photosynthetically active radiation (%PAR) on relative height growth (RHG) of nine species of shade-tolerant tree seedlings in secondary forests dominated by Cecropia and Vismia, varying in age from 1 to 20 years.Results: In Cecropia-dominated successions, seedling RHG decreased with increasing successional age and with associated decreasing %PAR. In Vismia-dominated successions, RHG was independent of successional age and %PAR, and %PAR did not change with successional age, being always higher than in Cecropia stands. The RHG of seedlings was lower in Vismia- than in Cecropia-dominated stands for similar %PAR levels.Conclusions: Successional age and light availability affect seedlings growth differently in the two successional pathways. Unlike in Cecropia-dominated successions, in Vismia-dominated secondary forests seedling growth is limited by factors other than light. In a scenario of increasing land use intensity constraints to seedling development in secondary forests can reduce species diversity in human altered landscapes.
The objective of this study was to evaluate whether early successional shrubs facilitate, tolerate or inhibit different stages of tree establishment in abandoned tropical pasture.
Seed rain, seed predation, seed germination and seedling survival of tropical forest trees in pasture grass, below small (< 25 m ² ) shrub patches and below large (> 40 m ² ) shrub patches, were compared in one abandoned pasture in Costa Rica over 2 years.
Seed rain of animal‐dispersed trees was higher below both large and small shrub patches than below grass. Seed rain of wind‐dispersed trees did not differ in the three patch types.
Predation of all animal‐dispersed seeds combined and of three individual species was significantly higher below large and small shrub patches compared with below grass; predation of five species did not differ significantly in the three patch types.
Germination did not differ significantly in the three patch types for any of the species.
Seedling survival was highest below large shrub patches for three of four species.
Computer simulations of probabilities of seeds arriving in the pasture and surviving to the seedling stage suggest that early successional shrubs have a net facilitative effect on the early stages of forest tree seedling establishment compared with areas without shrubs in the pasture studied, although variance was high. Shrubs may facilitate, inhibit and tolerate different stages of tree seedling establishment.
Successional pathways were evaluated in two Amazonian secondary forest communities with different land‐use histories. Sites which had been clearcut without subsequent use were dominated after 6–10 years by the pioneer genus Cecropia (Moraceae), whereas those used for pasture before abandonment were dominated by the pioneer genus Vismia (Clusiaceae).
There were 58 plant families and 300 species identified in Cecropia stands but only 43 families and 147 species were identified in Vismia stands. There were 77 species in common (Sorensen similarity = 0.34).
Differences in species number and composition of recruiting individuals between stand types were significant and were a function of the dominant pioneer genus, stem density, distance from primary forest, and land‐use history. Regeneration under Vismia canopy was dominated by small Vismia individuals (25% of plants < 2 cm basal diameter), whereas regeneration under Cecropia canopy was more diverse and did not include a single young Cecropia .
The number of regenerating plants in both secondary stand types dropped off sharply with distance (5, 25, 50, and 100 m) from primary forest, suggesting that seed dispersal was limiting plant recruitment. Species richness also declined with distance and could be explained by the decline in plant density. Species richness in Cecropia stands increased linearly with plant density, but in Vismia stands the richness increase with density was a decelerating function.
For the central Amazon, secondary succession involves a more rapid return of primary forest species if deforestation is not followed by use as pasture before abandonment.
Secondary forests are a vital part of the tropical landscape, and their worldwide extent and importance continues to increase. Here, we present the largest chronosequence data set on forest succession in the wet tropics that includes both secondary and old-growth sites. We performed 0.1 ha vegetation inventories in 30 sites in northeastern Costa Rica, including seven old-growth forests and 23 secondary forests on former pastures, ranging from 10 to 42 yr. The secondary forest sites were formerly pasture for intervals of <1–25 yr. Aboveground biomass in secondary forests recovered rapidly, with sites already exhibiting values comparable to old growth after 21–30 yr, and biomass accumulation was not impacted by the length of time that a site was in pasture. Species richness reached old-growth levels in as little as 30 yr, although sites that were in pasture for > 10 yr had significantly lower species richness. Forest cover near the sites at the time of forest establishment did not significantly impact biomass or species richness, and the species composition of older secondary forest sites (>30 yr) converged with that of old growth. These results emphasize the resilience of tropical ecosystems in this region and the high conservation value of secondary forests.
Avaliação e monitoramento de áreas em processo de restauração. Martins, SV Restauração ecológica de ecossistemas degradados
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