Succession In Tropical Rainforest Research Articles

Light competition drives species replacement during secondary tropical forest succession

Light competition is thought to drive successional shifts in species dominance in closed vegetations, but few studies have assessed this for species-rich and vertically structured tropical forests. We analyzed how light competition drives species replacement during succession, and how cross-species variation in light competition strategies is determined by underlying species traits. To do so, we used chronosequence approach in which we compared 14 Mexican tropical secondary rainforest stands that differ in age (8–32 year-old). For each tree, height and stem diameter were monitored for 2 years to calculate relative biomass growth rate (RGR, the aboveground biomass gain per unit aboveground tree biomass per year). For each stand, 3D light profiles were measured to estimate individuals’ light interception to calculate light interception efficiency (LIE, intercepted light per unit biomass per year) and light use efficiency (LUE, biomass growth per intercepted light). Throughout succession, species with higher RGR attained higher changes in species dominance and thus increased their dominance over time. Both light competition strategies (LIE and LUE) increased RGR. In early succession, a high LIE and its associated traits (large crown leaf mass and low wood density) are more important for RGR. During succession, forest structure builds up, leading to lower understory light levels. In later succession, a high LUE and its associated traits (high wood density and leaf mass per area) become more important for RGR. Therefore, successional changes in relative importance of light competition strategies drive shifts in species dominance during tropical rainforest succession.

Secondary Succession Altered the Diversity and Co-Occurrence Networks of the Soil Bacterial Communities in Tropical Lowland Rainforests.

The characteristics of plant and soil bacterial communities in forest ecosystems have been reported, but our understanding of the relationship between plant communities and soil bacteria in different stages of secondary tropical rainforest succession is still poor. In June 2018, three different natural successional stages of tropical lowland rainforests, early (33 years), early-mid (60 years), and mid successional stage (73 years), in Hainan Island, China, were selected for this study. By conducting field investigation and 16S rRNA gene high-throughput sequencing, the composition and diversity of tree communities, the niche overlap of tree species with legumes among tree species, and the diversity and composition of soil bacterial communities and co-occurrence networks within communities across the successional stages were investigated. The results showed that plant richness and species diversity increased significantly during the secondary succession of tropical lowland rainforests. The order of positive correlations between nitrogen-fixing legumes and other species in plant communities was early-mid > mid > early successional stage. Soil nutrient content and soil bacterial richness were highest in the early-mid stages of succession, followed by mid and early stages of succession. Organic matter (OM), total nitrogen (TN), alkali nitrogen (AN), and available phosphorus (AP) had a stronger positive impact on soil bacterial communities. Co-occurrence network analysis showed that with the advancement of rainforests succession, the negative correlation between soil bacterial species decreased, and the community stability increased. Overall, as a result of tropical lowland rainforest secondary natural succession, the richness and diversity of plant communities increased, which altered the living conditions of nitrogen-fixing legumes and the soil properties, and the network complexity of soil bacterial communities increased with the rising of rainforest soil nutrient content.

Physical structure and biological composition of canopies in tropical secondary and old-growth forests.

The area of tropical secondary forests is increasing rapidly, but data on the physical and biological structure of the canopies of these forests are limited. To obtain such data and to measure the ontogeny of canopy structure during tropical rainforest succession, we studied patch-scale (5 m2) canopy structure in three areas of 18–36 year-old secondary forest in Costa Rica, and compared the results to data from old-growth forest at the same site. All stands were sampled with a stratified random design with complete harvest from ground level to the top of the canopy from a modular portable tower. All canopies were organized into distinct high- and low-leaf-density layers (strata), and multiple strata developed quickly with increasing patch height. The relation of total Leaf Area Index (LAI, leaf area per area of ground) to patch canopy height, the existence of distinct high and low leaf- density layers (strata and free air spaces), the depth and LAI of the canopy strata and free air spaces, and the relation of the number of strata to patch canopy height were remarkably constant across the entire successional gradient. Trees were the most important contributor to LAI at all stages, while contribution of palm LAI increased through succession. We hypothesize that canopy physical structure at the patch scale is driven by light competition and discuss how this hypothesis could be tested. That canopy physical structure was relatively independent of the identity of the species present suggests that canopy physical structure may be conserved even as canopy floristics shift due to changing climate.

Tropical Rainforest Successional Processes can Facilitate Successfully Recovery of Extremely Degraded Tropical Forest Ecosystems Following Intensive Mining Operations

Reforestation is an effective way to alleviate deforestation and its negative impacts on ecosystem services. In tropical rainforest ecosystem, however, frequent typhoons and heavy rainfall can result in landslides and uprooting of many seedlings, making reforestation efforts very difficult, especially within extremely degraded sites where soil conditions cannot support any plant life. Here, we described a reforestation protocol which is based on tropical rainforest successional processes to not only prevent landslides and tree uprooting due to frequent typhoon and heavy rain, but also accelerate tropical forest succession. This protocol first used the slope and soil layer of the undisturbed old-growth tropical rainforest as a reference to reconstruct slope and soil layers. Then multiple tropical tree species with high growth and survival rate were separately monocultured in the reconstructed soil layers. In the year of 2015 and 2016, we tested the effectiveness of this protocol to recover a 0.2 km2 extremely degraded tropical rainforest which consists of bare rock and thus does not support any plant life, in Sanya city, China. Our results showed that, both typhoons and heavy rains did not result in landslide or any tree damages in the area this reforestation protocol was used. Moreover, our separately monocultured eight fast-growing tree species have much higher fast-growing related functional traits than those for tree species in the adjacent undisturbed tropical seasonal forest, which in turn resulted in large soil water and nutrient loss within 3 years. This seemed to simulate a quick transition from primary succession (consist of bare rock and cannot support any plant life) to mid-stage of secondary tropical rainforest succession (many fast-growing pioneer tree species induced high soil water and nutrient loss). Thus, mixing the late-successional tropical tree species with each of the separately monocultured eight fast-growing tree species can accelerate recovery to the undisturbed tropical rainforest as soon as possible. Overall, based on tropical rainforest successional processes, our research provides an effective protocol for quickly and effectively restoring an extremely degraded tropical rainforest ecosystem. We expect that this work will be important for the future recovery of other extremely degraded tropical rainforest ecosystems.

Shade tolerance within the context of the successional process in tropical rain forests

Shade tolerance (the capacity to survive and grow over long periods under shade) is a key component of plant fitness and the foundation of current theories of forest succession in tropical rain forests. It serves as a paradigm to understand the optimal allocation of limited resources under dynamic light regimes. I analyze how tropical rain forest succession influences the expression of ecophysiological mechanisms leading to shade tolerance, and identify future areas that will increase our understanding of the ecological and evolutionary consequences of this phenomenon. Shade tolerance is a multivariate, continuous functional trait reflecting the growth-mortality trade-off of investing resources under limited light vs. exploiting high light conditions. I propose the life cycle successional trajectory model of Gómez-Pompa & Vázquez-Yanes as an integrative tool to understand tropical rain forest succession. This model shows how species distribute along the successional environmental gradient based on their degree of shade tolerance and represents a more integrative paradigm to understand the interface between different aspects of species diversity (ontogenetic variation and functional diversity) throughout succession. It proposes that different trait combinations determining shade tolerance are expressed at different stages of the life cycle, which affects how and when plants enter the successional trajectory. Models explaining the expression of shade tolerance (resource availability, carbon gain, CSR, resource competition) are based on whole-plant economics and are not mutually exclusive. The analysis of shade tolerance is biased towards tree seedlings in the understory of mature forests. Other life stages (juvenile and adult trees), life forms, and microhabitats throughout the forest profile are almost always excluded from these analyses. More integrative explanations based on the distribution of functional traits among species, ontogenetic stages, and the nature of the environmental gradient are being developed based on long-term data and chronosequence comparisons. In summary, shade-tolerance is a complex phenomenon, is determined by multiple characters that change ontogenetically over space and time and entails considerable plasticity. Current methods do not account for this plasticity. Understanding the nature of shade tolerance and its functional basis is critical to comprehending plant performance and improving the management, restoration and conservation of tropical rain forests given the combined threats of global warming and habitat loss

Diversity of fruit-feeding butterflies (Nymphalidae) along a gradient of tropical rainforest succession in Borneo with some remarks on the problem of "pseudoreplicates"

Diversity of fruit-feeding butterflies (Nymphalidae) along a gradient of tropical rainforest succession in Borneo with some remarks on the problem of "pseudoreplicates"

Sucesión ecológica y restauración de las selvas húmedas

Las selvas húmedas han sufrido una intensa deforestación y degradación debido a las actividades antropogénicas. Grandes áreas antes cubiertas por estos bosques de elevada diversidad actualmente se encuentran transformadas en campos agropecuarios, bosques secundarios, campos degradados abandonados y, en menor proporción, remanentes aislados de selva. La teoría clásica de la regeneración natural en claros resulta insuficiente para el estudio de la sucesión y la restauración ecológica de selvas en los extensos campos deforestados. Se requieren nuevos principios ecológicos que permitan el desarrollo de tecnologías eficientes para la recuperación de selvas en campos degradados. El presente artículo desarrolla un esquema conceptual que considera el nivel de disponibilidad de propágulos de especies nativas y el grado de alteración ambiental (calidad de sitio) como dos ejes determinantes de la capacidad de regeneración de la vegetación de selva en campos degradados. La historia de uso del suelo es un promotor importante del estado de los ejes anteriores al modificar con un cierto nivel de intensidad, extensión y duración al ecosistema original. Nuestro marco conceptual identifica factores clave que es importante considerar en la restauración de campos degradados. Según nuestro modelo, la tasa y la magnitud de la regeneración natural (capacidad de regeneración) disminuyen con una reducción en la disponibilidad de propágulos (i.e. banco y lluvia de semillas, regeneración de avanzada, meristemos en raíces y tocones) y la disminución de la calidad sitio (por ejemplo, al aumentar la compactación y la fertilidad del suelo , y la abundancia de plantas exóticas). Dife rentes tipos de uso de suelo reducen diferencialmente la capacidad de regeneración de la vegetación nativa. Por ejemplo, predecimos que la capacidad de regeneración en milpas abandonadas (las cuales reducen en mucho menor grado la disponibilidad de propágulos y la calidad de sitio) debería ser mayor que en pastizales ganaderos abandonados. Las predicciones se evalúan con información proveniente de la literatura y de un proyecto de investigación de largo plazo llevado a cabo en la región de La Selva Lacandona (Chiapas), México. Finalmente, se hace una reflexión sobre los costos asociados a la restauración y se ofrecen recomendaciones que pueden ayudar a promover la sucesión ecológica en campos degradados

Species Dynamics During Early Secondary Forest Succession: Recruitment, Mortality and Species Turnover

ABSTRACTThe “Initial Floristic Composition” hypothesis is applied to secondary tropical rain forest succession in abandoned agricultural fields with light previous land‐use and close to seed sources. This hypothesis predicts that both pioneer and shade‐tolerant species colonize a site directly after abandonment, and as the canopy closes, the recruitment of pioneers sharply declines, while recruitment of shade‐tolerant species continues. It also predicts higher mortality among pioneers. Consequently, recruited and dead trees are expected to differ in species composition, with highest species richness for the recruits. During 18 mo, we monitored recruitment and mortality of trees with height ≥ 1.5 m in eight plots in abandoned cornfields with initial fallow age of 1–5 yr, in SE Mexico. Shade‐tolerant species established in the first years of succession, albeit in low numbers. As predicted, recruited and dead trees differed in species richness and composition, and in shade‐tolerant frequency. In contrast to our expectations, over 50 percent of recruits were from pioneer species, as high stand‐level mortality opened new opportunities for continued pioneer colonization. Species turnover starts very early in succession but is not always a gradual and continuous process, complicating prevailing succession models. The strong spatial and temporal variability of succession emphasizes the need to monitor these dynamics in permanent plots across a range of initial stand ages, with multiple plots in a given age class.

Effects of burning strength in shifting cultivation on the early stage of secondary succession in Sarawak, Malaysia

The effects of burning strength in shifting cultivation on the early stage of secondary succession in tropical rain forest was investigated at four sites (Sabal, Balai Ringin, Niah, and Bakam) in Sarawak, Malaysia. The number and growth (diameter, height, and biomass) of germinated seedlings were measured in experimental shifting cultivation plots in which the burning strength varied between 0, 100, 200, and 300 t/ha at Sabal, Balai Ringin, and Niah and 0, 20, and 100 t/ha at Bakam. Species composition of germinated tree and herbaceous seedlings was surveyed, and a germination test of buried seed was conducted at Niah and Bakam. The number of germinated seedlings decreased with increasing burning strength, whereas seedling growth was promoted by burning. During the first year, growth was best in the intermediate burning strength plots, whereas during the second year, growth was best in the most strongly burned plots. Species composition differed between unburned and burned sites. Site-specific factors such as original stand biomass, soil properties, and invasion of exotic species also affected germination and growth. Buried seeds in the Ao layer were killed by burning, and nearly all seeds in the 0-5 cm layer were killed in the plots with the highest burning strength (> 100 t/ha). On the basis of our findings, we conclude that in shifting cultivation systems burning promotes vegetation recovery when the burning strength is properly managed.

Influence of shade on photosynthetic gas exchange of 7 tropical rain-forest species from Guadeloupe (French West Indies)

species studied and when the measurements were expressed on a leaf-area basis, maximum photosynthesis of sun-grown seedlings was higher than for shade-grown seedlings. The opposite was observed for photosynthesis under limited light and for apparent quantum yield. We also observed a decrease in maximum photosynthesis and an increase in apparent quantum yield when specific leaf area increased, ie when the plants were more shaded. The range of variation in photosynthetic response between full sunlight and full shade made it possible to characterize the photosynthetic plasticity of the species. The results were compared with those obtained for other tropical rain-forest species. They are discussed in terms of photosynthetic and morphological plasticity, shade adaptation, and of the species’ place in tropical rain-forest succession.

Response of Seedlings of Tropical Trees to Cool Temperatures Predicted by ‘Nuclear Winter’ Scenarios

Mathematical models predict that a nuclear war could cause widespread reductions in light intensity and temperature. To assess the possible impact of these reductions on lowland tropical rain-forests, we exposed seedlings of three species of the family Moraceae to various combinations of day and night conditions under reduced light. The species represent three stages in tropical rain-forest succession: Cecropia obtusifolia is an early-successional pioneer, Trichospermum mexicanum is a mid-successional tree, and Brosimum alicastrum is a late-successional tree of mature-phase forests.

Physiological Plant Ecology: Some Contributions to the Understanding of Secondary Succession in Tropical Lowland Rainforest

The current status of the field of physiological plant ecology of tropical secondary tree species is reviewed, focusing on seed germination, net CO2 exchange studies, water relations, and energy balances; its contributions to the understanding of recovery in disturbed areas are discussed. Suggestions of areas in need of future research and methodology are provided. IN RECENT YEARS, the topic of secondary succession in tropical rainforests has received increasing attention due to the accelerated rates of destruction of these areas (G6mez-Pompa et al. 1972, Richards 1973). Secondary succession involves changes of community species composition, structure, and microclimate at a specific site (Pickett 1976). An understanding of the physiological ecology of secondary plants can further our understanding of the nature of the process of secondary succession. Yet except for research on seed germination, relatively little work has been done on the physiological ecology of secondary species in the tropics. This paper presents a brief summary of progress in the field of physiological ecology of tropical secondary tree species, discusses some of the ways in which studies can contribute to our understanding of the process of secondary succession in these forests, and indicates areas in need of future research. It will focus on secondary succession starting from clearcut areas since this is the topic for which most information is available. Secondary succession in naturally occurring canopy gaps, although important in the general dynamics of the forest populations, has scarcely been studied (Whitmore 1966).

Soil nitrogen mineralisation in a secondary rainforest succession.

It has been suggested that soil nitrification is inhibited as a succession develops. This hypothesis was examined in a sub tropical rain forest succession containing five successional stages. Soil mineral nitrogen was measured at the time of collection and after 20 days incubation in the laboratory or field. Sampling was carried out during the wet season and dry season. There was little difference in the ammonium nitrogen concentration at the various sites but increasing amounts of nitrate nitrogen were generally found in each older successional stage.The data show that nitrification inhibition is not an invariable consequence of successional development. Instead the pattern of nitrogen mineralisation is probably related to the overall soil fertility and to the pool of available soil nitrogen.