Estímulos ao banco de sementes do solo reduzem a predominância de gramíneas exóticas em pastagens amazônicas

Riparian vegetation has great functional importance in agroscapes because it establishes physical connections between natural ecosystems embedded in an agricultural matrix. Throughout the tropics, the historical demand for cropland and pastures in the lands adjacent to streams has led to the replacement of forests by exotic grasses. In order to find new methods for initiating the restoration of riparian forests, we evaluated the use of the pioneer shrubs Tithonia diversifolia and Piper auritum as nurse species for their effects on (1) competition with dominant grasses; (2) natural regeneration and the ecological facilitation of six native tree species of different successional stages; and (3) influence on microclimate. Over a period of 15 months, 4.4% coverage of P. auritum was insufficient to inhibit grasses. In contrast, 81% coverage of T. diversifolia limited the growth of dominant grasses such as Cenchrus purpureus, Paspalum paniculatum, and Cynodon plectostachyus likely by intercepting more than 90% of photosynthetically active radiation (PAR), even though other factors cannot be ruled out. T. diversifolia showed simultaneous effects of facilitation and competition by promoting higher survival of the planted native trees while slowing the growth of pioneer species and inhibiting the regeneration of native woody plants probably as a result of high light interception. This study suggests that planting T. diversifolia as a nurse shrub may facilitate early stages of restoration by inhibiting the growth of pastures, but requires pruning, both to increase light availability and promote the growth of planted trees and the recruitment of woody plants.

A capacidade de regeneração natural de espécies nativas em situações de competição com árvores de plantios florestais pode ser considerado um fator de grande valor para a manutenção da diversidade. Diante disso, o presente estudo avaliou a regeneração natural de espécies nativas no sub-bosque de um povoamento de Eucalyptus saligna Smith., localizado na Reserva Biológica de Saltinho, PE. Para a análise da estimativa da regeneração natural das espécies arbóreas foram selecionados três talhões de Eucalyptus saligna Smith. Em cada um deles, foram implantadas parcelas de 1,0 x 50 m, sendo uma na extremidade do talhão e as outras distanciando 10 m de uma da outra, totalizando dez subunidades. As análises foram estabelecidas, com base no nível de inclusão das espécies arbóreas em regeneração natural com Circunferência do Caule a Altura de 30 cm do solo - (CAB0,30m) ≤ 15 cm, e as classes de alturas foram assim distribuídas: Classe 1 com indivíduos arbóreos com altura (H) 1,0 ≤ H ≤ 2,0, a Classe 2 com altura (H), 2 < H ≤ 3 e a Classe 3 com altura (H) >3,0 m. Para avaliar a diversidade florística a nível de espécie utilizou-se o índice de Shannon (H´). No total, foram amostrados 302 indíviduos vivos, pertencentes a 23 famílias botânicas, 31 gêneros e 39 espécies. Analisando-se os resultados obtidos pode-se concluir que o eucalipto possibilita a regeneração de espécies nativas no sub-bosque, contudo, a composição florística depende também de características edáficas e da proximidade de fontes de propágulos.

Forest degradation often permits the proliferation of dense understories that inhibit the development of natural regeneration over long periods. In South American temperate rainforests, native Chusquea bamboo species become unusually competitive after logging and invade forest understories, creating dense and continuous thickets under remnant canopy tree species. In this study, we aim to evaluate how natural regeneration of native species develops after removal of the Chusquea bamboo understory and to define which microsite conditions can facilitate species' early development. To achieve this, we removed the Chusquea understory in 45 experimental units, systematically established in a 4 ha experiment located in degraded temperate forests on Chiloé Island, North‐Patagonia, Chile. We evaluated microsite conditions and monitored the natural regeneration response during 5 years. After 5 years, greater than 81% of the remnant canopy tree species were regenerating, mostly from seed, and there was a 55.5% increase in total natural regeneration (p < 0.05; increase >1 individuals/m2 yr−1), with species like Amomyrtus spp. increasing abundance by greater than 121%. Total natural regeneration presented positive significant correlations (p < 0.01) with the depth of the water table (rs: 0.40), soil carbon (rs: 0.44), nitrogen (rs. 0.41), and organic matter (rs: 0.44). We conclude that removing the Chusquea understory assists the natural recovery of degraded temperate rainforests by facilitating additional recruitment of early, mid, and late successional tree species. In this process, early and mid‐successional tree species are more specific in their microsite preferences than successionally late ones.

International forest landscape restoration commitments have promoted the restoration of millions of hectares of degraded and deforested lands globally, but few forest restoration approaches provide both ecologically‐sound and financially‐viable solutions for achieving the spatial scale proposed. One potential revenue source for restoration is selective harvesting of timber, a product for which there is a clear global market and increasing demand. The use of commercially valuable exotic trees may attract farmers to restoration, but can be a major concern for ecologists. Here, we present results collected over 7 years from experimental studies at three sites across the Brazilian Atlantic Forest to assess the impacts of incorporating exotic eucalypts as a transitional stage in tropical forest restoration on above‐ground biomass accumulation, native woody species regeneration and financial viability. Biomass accumulation was nine times greater in mixed eucalypt‐native species plantations than native only plantings due to fast eucalypt growth. Nonetheless, the growth of native non‐pioneer trees was not affected or only slightly reduced by eucalypts prior to logging. Eucalypts did not negatively affect the natural regeneration of native woody species before or after eucalypt logging. Canopy cover regrew quickly but was slightly lower a year following logging in mixed eucalypt‐native species plantations. Natural regeneration richness and planted non‐pioneer growth were similar across treatments in the post‐logging period. We found higher variation of biomass accumulation and native species regeneration among sites than between plantation types within sites. The income from eucalypt wood production offset 44%–75% of restoration implementation costs. Synthesis and applications. Many of the negative effects attributed to eucalypts on the growth and natural regeneration of native trees depend on features of the production system, landscape structure, soil, and climate in which they are grown, rather than the effects of eucalypts per se. In Brazil's Atlantic Forest region, exotic eucalypts can become important allies of tropical forest restoration, and their use and investment opportunities should be considered within the portfolio of options supported by public and private funding and policies.

En los andes del Ecuador existen plantaciones de Pinus radiata y Pinus patula, sembradas entre matorrales, páramos y áreas abiertas; y, se desconoce la sucesión vegetal, sus cambios y desarrollo. Se investigó una plantación de Pinus radiata en la hoya de Loja con el objetivo de caracterizar la composición florística y monitorear la regeneración natural considerando categorías de regeneración: plántulas, brinzales y latizales. Se establecieron 5 parcelas de 20 m x 20 m, se anidaron 5 subparcelas de 5 m x 5 m y 5 subparcelas de 1 m x 1 m. Se midió altura y diámetro basal. Se determinó la sobrevivencia y crecimiento en un periodo de 12 meses; se analizó la influencia de variables ambientales: luminosidad, pendiente, profundidad del suelo horizonte O, sobre la diversidad y abundancia de la regeneración natural. Se identificaron 24 especies, 21 géneros y 22 familias. La mayor diversidad presentan los latizales; las especies con mayor IVI en las tres categorías son: Piper barbatum, Viburnum triphyllum y Frangula granulosa. Los latizales presentan mayor sobrevivencia (99,37 %), seguida por brinzales (87,59 %) y plántulas (82,76 %). El incremento en altura y diámetro es mayor en Frangula granulosa, Clusia latipes, Critoniopsis pycnantha y Alnus acuminata. No existe influencia significativa de los factores ambientales sobre la diversidad y abundancia de la regeneración natural. La regeneración natural encontrada en las condiciones de hábitat de la plantación; demuestra que es factible la recuperación de la vegetación natural y la presencia de un bosque natural cuando desaparezca la plantación forestal.

The brushwood is a technique of environmental complexation, which consists in the use of plant residues. This technique, when well established technically, can exert influence on seedbed quality, fostering native plant establishment and ecosystem restoration. In this way, we aimed to evaluate the efficiency of brushwood for the induction of natural regeneration of native species in an area covered by exotic inhibitory grasses of the genus Urochloa, as well as check the minimum size required to prevent the re-invasion of the forage. As a hypothesis, we adopted the minimum width of 4 m as sufficient for the establishment of natural regeneration prior to the reoccupation of grasses. The experiment was conducted between May 2014 and May 2016 in Morretes-PR in a lowland evergreen rain forest area. Seven different sizes of brushwood were compared: 6 x 1, 6 x 2, 6 x 3, 6 x 4, 6 x 5, 6 x 6 m and control treatment. Woody species were identified and counted and herbaceous cover percentage estimated after 4, 8, 12, 18 and 24 months. There was no resumption of natural succession of native species. At any size, brushwood alone was ineffective to prevent the growth by grasses from the edges of the plots, and, since it constitutes a residue pile, it further complicates the establishment of woody species. For the creation of safe sites and consequent restoration by natural regeneration, there is a need for local elimination of Urochloa forages, without which native species are unlikely to survive.

The expansion and intensification of açaí management in floodplain forests of the Amazonian estuary have resulted in changes in floristic composition and in biodiversity losses, causing problems to ecosystems and endangering livelihoods of riverine communities. These transformations have prompted the need for forest restoration. The objective of this study was to identify and analyze forest recovery initiatives carried out in floodplain forests previously subjected to intensive açaí management in the Amazonian estuary. Methods included structured interviews and questionnaires. Results reveled the following restoration types: 1) area enrichment: subtype 1 - high floodplain forest (7.89%) and subtype 2 - low floodplain forest (44.75%); 2) directing natural regeneration of native species (34.21%); 3) cultivation of native species (13.15%). Results suggest that forest restoration efforts can promote sustainable production of açaí, productive diversity, ecosystem conservation and generate income for riverine families.

Встановлено основні технологічні елементи створення модриново-ялицевих культур, здійснено порівняння середніх таксаційних показників Larix L., Abies alba Mill., Picea abies (L.) Karst. у штучних насадженнях – висоти, діаметра та об’єму середнього дерева в умовах вологих букових та грабово-букових яличин і суяличин, а також ялицевих дібров. Встановлено, що створення лісових культур за участю модрини та ялиці є перспективним напрямком формування високопродуктивних багатоярусних і стійких лісових фітоценозів.
 Насадження за участю ялиці та модрини відзначаються високими таксаційними показниками та значними запасами стовбурової деревини, де темнохвойна порода відіграє роль підгону, а модрина формує повнодеревні стовбури, зростаючи у пристигаючих насадженнях за Іа-Іb класами бонітету. Модрина, при цьому, завжди має перевагу над ялицею за висотою, що дає їй змогу успішно рости в модриново-ялицевих деревостанах.
 У молодих насадженнях 30-35-річного віку модрина, при сумісному зростанні з ялицею, а також з ялиною має перевагу за висотою в межах 20-25%, за діаметром – 25-30%, за об’ємом середнього дерева – в два рази. У насадженнях 41-50-річного віку модрина має перевагу над ялицею за висотою на 10-20%, хоча в окремих випадках може відставати в рості за діаметром.
 Аналіз ходу росту показує, що до 30-річного віку найвищою інтенсивністю росту за висотою та діаметром характеризуються модрина та ялина, тоді як ялиця починає формувати значні прирости, як за висотою так і за діаметром, після 30-40-річного віку.
 Під час формування високопродуктивних та стійких ялиново-модриново-ялицевих насаджень лісокультурними і лісівничими заходами необхідно забезпечити участь модрини в їх складі в межах 30-40%.
 Встановлено доцільність створення часткових культур модрини методом висаджування породи окремими рядами чи біогрупами серед природного поновлення корінних порід – бука та ялиці.

QuestionWhat is the effect of invading individuals of the widely invasive species Pinus radiata D. Don on regeneration of native woody species in a semi‐arid ecosystem?LocationA semi‐arid ecosystem in central Chile.MethodsWe sampled natural regeneration of native woody species in 40 plots in each of three canopy types: (1) under young adult invading trees of P. radiata located in formerly open (disturbed) sites; (2) in patches of native trees; and (3) in open (disturbed) sites, in two localities where this exotic tree is invading. Additionally, we carried out a field experiment in one of these localities; in eight of each of these canopy types we sowed seeds of ten widely distributed woody native species and monitored their recruitment. We also assessed different biotic and abiotic variables in these canopy types.ResultsWe found that soil water content, depth and cover of leaf litter were higher and photosythetically active radiation was lower under P. radiata trees and native patches than in open sites. In the natural regeneration study, species richness of seedlings was higher in native patches and under P. radiata trees than in open sites, and total abundance of seedlings (including all species) was higher only in native patches than in open sites. In the field experiment, both species richness and total abundance of seedlings were higher in native patches and under P. radiata trees than in open sites. Moreover, in the field experiment species richness recruiting in native patches was higher than under P. radiata trees.ConclusionsWe suggest that native patches as well as P. radiata trees invading open sites facilitate or have the potential to facilitate regeneration of native species, although facilitation produced by native trees was stronger than that produced by P. radiata. Thus, in sites where nurse plants are not available, invasion by this exotic tree may be exploited in restoration processes through sowing or planting native species under the canopy of invading young trees of P. radiata, eliminating P. radiata individuals after native regeneration has established.

Abstract: The objective of this work was to evaluate the effect of brushwood, black plastic mulch, herbicide, and artificial perch on the natural regeneration of native species in Urochloa grassland. The experiment was conducted between February 2014 and February 2016 in the Dense Ombrophilous Forest, in the municipality of Morretes, in the state of Paraná, Brazil. The treatments were: herbicide, herbicide + perch, black plastic mulch, black plastic mulch + perch, brushwood + herbicide, brushwood + herbicide + perch, and a control treatment. The evaluations were carried out at 4, 8, 12, 18, and 24 months after the installation of the experiment, by counting and identifying regenerating woody species and estimating visually the percentage of herbaceous coverage. Initially, brushwood and black plastic mulch reduced the Urochloa grasses; however, this effect was lost over time due to the rapid growth of the grasses from the edges to the center of the plots. The use of perches in the treatments does not allow a significant increase of other species because of the continued inhibiting conditions for the establishment of seedlings. The herbicide is effective in removing the grasses; however, the recruitment of woody species is only satisfactory when perches are used to attract the dispersing fauna. For a successful ecological restoration of pastures, there is a need for the local elimination of Urochloa grasses.

BackgroundInvasions by non-native plants contribute to loss of ecosystem biodiversity and productivity, modification of biogeochemical cycles, and inhibition of natural regeneration of native species. Japanese stiltgrass (Microstegium vimineum (Trin.) A. Campus) is one of the most prevalent invasive grasses in the forestlands of Tennessee, United States. We measured the extent of invasion, identified potential factors affecting invasion, and quantified the relative importance of each factor. We analyzed field data collected by the Forest Inventory and Analysis Program of the U.S. Forest Service to measure the extent of invasion from 2005 to 2011 and identified potential factors affecting invasion during this period using boosted regression trees.ResultsOur results indicated that presence of Japanese stiltgrass on sampled plots increased 50% (from 269 to 404 plots) during the time period. The probability of invasion was correlated with one landscape condition (elevation) (20.5%) and five forest features (including tree species diversity, basal area, stand age, site productivity, and natural regeneration) (79.5%). Boosted regression trees identified the most influential (highly correlated) variables as tree species diversity (30.7%), basal area (22.9%), elevation (20.5%), and stand age (16.7%). Our results suggest that Japanese stiltgrass is likely to continue its invasion in Tennessee forests.ConclusionsThe present model, in addition to correlating the probability of Japanese stiltgrass invasions with current climatic conditions and landscape attributes, could aid in the on-going development of control strategies for confronting Japanese stiltgrass invasions by identifying vulnerable areas that might emerge as a result of likely changes in climatic conditions and land use patterns.

A major global effort to enable cost‐effective natural regeneration is needed to achieve ambitious forest and landscape restoration goals. Natural forest regeneration can potentially play a major role in large‐scale landscape restoration in tropical regions. Here, we focus on the conditions that favor natural regeneration within tropical forest landscapes. We illustrate cases where large‐scale natural regeneration followed forest clearing and non‐forest land use, and describe the social and ecological factors that drove these local forest transitions. The self‐organizing processes that create naturally regenerating forests and natural regeneration in planted forests promote local genetic adaptation, foster native species with known traditional uses, create spatial and temporal heterogeneity, and sustain local biodiversity and biotic interactions. These features confer greater ecosystem resilience in the face of future shocks and disturbances. We discuss economic, social, and legal issues that challenge natural regeneration in tropical landscapes. We conclude by suggesting ways to enable natural regeneration to become an effective tool for implementing large‐scale forest and landscape restoration. Major research and policy priorities include: identifying and modeling the ecological and economic conditions where natural regeneration is a viable and favorable land‐use option, developing monitoring protocols for natural regeneration that can be carried out by local communities, and developing enabling incentives, governance structures, and regulatory conditions that promote the stewardship of naturally regenerating forests. Aligning restoration goals and practices with natural regeneration can achieve the best possible outcome for achieving multiple social and environmental benefits at minimal cost.

Gap cutting consists of the removal of all trees growing on a small surface, varying in size from 200 to 600 m2. In Italy, gap cutting has been successfully tested for introducing the natural regeneration of native species into softwood plantations, thus accelerating the transition towards climax hardwood stands. Depending on plantation types and conditions, gap cutting should be started at an age between 70 and 80 years and the system should include at least 12 to 15 gaps, in order to produce enough wood to cover costs. Generally, natural regeneration is firmly established within 5–7 years from treatment. Gap cutting also offers superior results to selection thinning, the latter producing about 35% less value and incurring 25% to 30% more costs. As for all regeneration cuts, the success of gap cutting depends on wildlife control in order to prevent extensive damage to the regeneration.

Tree monocultures constitute an increasing fraction of the global tree cover and are the dominant tree-growing strategy of forest landscape restoration commitments. Their advantages to produce timber are well known, but their value for biodiversity is highly controversial and context dependent. Therefore, understanding whether, and in which conditions, they can harbor native species regeneration is crucial. Here, we conducted meta-analyses based on a global survey of the literature and on a database created with local, unpublished studies throughout Brazil to evaluate the regeneration potential of native species under tree monocultures and the way management influences this regeneration. Native woody species regeneration under tree monocultures harbors a substantial fraction of the diversity (on average 40% and 68% in the global and Brazilian surveys, respectively) and abundance (on average 25% and 60% in the global and Brazilian surveys, respectively) of regeneration observed in natural forests. Plantations with longer rotation lengths, composed of native tree species, and located adjacent to forest remnants harbor more species. Pine plantations harbor more native individuals than eucalypt plantations, and the abundance of regenerating trees is higher in sites with higher mean temperatures. Species-area curves revealed that the number of woody species under pine and eucalypt plantations in Brazil is 606 and 598 species, respectively, over an aggregated sampled area of ca. 12 ha. We highlight that the understory of tree monocultures can harbor a considerable diversity of regenerating native species at the landscape and regional scales, but this diversity strongly depends on management. Long-rotation length and favorable location are key factors for woody regeneration success under tropical tree monocultures. Therefore, tree monocultures can play a role in forest landscape restoration and conservation, but only if they are planned and managed for achieving this purpose.

Identifying factors involved in the choice of species for forest restoration is a great challenge, given the wide range of biotic and abiotic factors that may influence ecosystem trajectories. This review aims to highlight the information from reference areas and edaphoclimatic factors as aids in the choice of forest species to be used in the restoration of riparian forests, especially for the southern of Brazil. Native forest species of natural occurrence in riparian areas offer the potential for recovering these environments, depending on the ecological group and stage of ecological succession where they are naturally present. However, floristic and phytosociological surveys in well-preserved remnant riparian forests with no anthropogenic interference and in areas at different stages of natural succession are needed. This will enable the identification of the most representative species which are adapted to the conditions of local sites. Additionally, information must be correlated with chemical, physical and biological aspects of the soil as well as ecological processes and climatic characteristics, enabling the proper choice of species. Thus, the components of soil-plant-atmosphere system must be incorporated into the degraded environments in order to achieve an integrated recovery of ecological processes.