Neotropical rainforest climax trees-

Neotropical forests NFs play a main role in delivering environmental services such as biodiversity conservation and C sink. Conserving the remaining NF and recovering degraded areas is then urgent, although it is not an easy task. Ecological traits are widely varied across NF, as well as their responses to anthropic intervention. In this chapter, we both highlight the main differences between RF and DF, from their origin to present-day distribution, species composition, taxonomic and functional diversities, and discuss the predictions for shifts in all these traits during the next decades. Although few certainties, NF potential for mitigation of atmospheric C increases is a consensus among researchers.

Neotropical rainforest climax trees

Neotropical rainforest climax trees

Neotropical rainforest climax trees

Neotropical rainforest climax trees

In Old fields: dynamics and restoration of abandoned farmland ed. K, Pascarella J. Tropical tree communities: a test of the nonequilibrium hypothesis. The invasibility of tropical forests by exotic plants. These are surprisingly high Neotropical rainforest climax trees, higher than the average basal area in neighbouring old-growth forest plots on comparable sites M. E, Knight D. D, Murawski D. The biomass loss due to mortality has a secondary role, and, as described above, it is important since early successional phases of RF, as well as Neotropical rainforest climax trees late regeneration phases of SDF.

Fitness women nude free gallery. 1. Complexities of vegetation change following stand-removing disturbances

Guayaquil flooded grasslands. ArgentinaBrazil. Juan Fernandez Islands temperate forests. Neotropic Temperate grasslands, savannas, and Neotroipcal v t e. Central American dry forests. GuatemalaMexico. BoliviaBrazilParaguay. Hispaniolan dry forests. Moist Pacific Coast mangroves. Chiapas montane forests. They grow in African, Asian and Neotropical rainforest climax trees rainforests. Oaxacan montane forests. Unique trees that feed on decomposing forest floor material, kauri trees produce toxins that Neotropical rainforest climax trees smaller species of insects and microorganisms that die and fall to the base of the tree, where the tree can then draw up the decomposing matter through a shallow tubular root structure.

Rates of change in tree communities following major disturbances are determined by a complex set of interactions between local site factors, landscape history and structure, regional species pools and species life histories.

  • The Neotropical realm is one of the eight biogeographic realms constituting the Earth's land surface.
  • In the previous article we covered plants in the tropical rainforest.
  • The Neotropical Rainforest.

Neotropical forests NFs play a main role in delivering environmental services such as biodiversity conservation and C sink. Conserving the remaining NF and recovering degraded areas is then urgent, although it is not an easy task. Ecological traits are widely varied across NF, as well as their responses to anthropic intervention. In this chapter, we both highlight the main differences between RF and DF, from their origin to present-day distribution, species composition, taxonomic and functional diversities, and discuss the predictions for shifts in all these traits during the next decades.

Although few certainties, NF potential for mitigation of atmospheric C increases is a consensus among researchers. We also speculate about possible interventions, with the aim of avoiding a drastic future scenario. Forests play a main role in global ecosystem services as water supply, climate regulation, conservation of biodiversity richness, and carbon dynamic and storage. For instance, Extent of forest loss red , gain green , and both magenta for the — period, as stated by Hansen et al. Due to the huge area comprised by the Neotropics, one can imagine that forest conservation should not be an easy issue, requiring unmistakable strategies according to the distinctiveness on species composition and ecological traits of the vegetation.

Indeed, heterogeneity of NF has been recognized for a long time, and many systems have been proposed for their classification. In a useful synthesis of such systems, five main forest physiognomies were proposed—broadleaved forest, mixed needle-broadleaved forest, stiff-leaved forest, broadleaved dwarf-forest, and stiff-leaved dwarf-forest—based on canopy structure and species assemblage [ 6 ].

The author, however, stresses that these criteria on their own are not enough to embrace all disparities of the vegetation and thus incorporates additional descriptors based on ecological and physiognomic attributes to be used in different combinations, as far as required.

It is important to highlight that water availability is determined not only by rainfall regime but also by variations of ground water regimes related to soils and geomorphology. Therefore, forests under different precipitation conditions may have similar growth periods, species compositions, and ecological traits [ 9 ]. It must be also stressed that the RF and SDF concepts are expanded here to include the southern temperate NF in spite of their strikingly distinct flora and environment [ 10 ].

In general, the larger continuous extents of NF are found as RF, although both patches and incursions are not uncommon. On the other hand, SDFs show a predominantly patchy distribution, with a wide variation in patch size [ 11 ]. Contrasting with SDFs, RFs display a lower species turnover, despite the intense plant migration favored by the instable conditions of those very dynamic communities. While the high turnover of species in continental, regional, and local scales is an inherent challenge for biodiversity conservation of the SDF, the growing fragmentation is a current threat to the maintenance of diversity and recovery of degraded areas in both NF and RF [ 15 ].

Additionally, current environmental changes—such as global warming associated to increased drought severity—may boost disturbance events and tree mortality and lead to the development of novel ecosystems, where hitherto NFs were dominant. Predicting how species and communities will behave in this scenario is thus a priority for successful actions of conservation of both Neotropical RF and SDF in the next decades.

While the first represents the pristine source of diversity for the present South American tropical forests, the latter is considered the ancestral of the present forests of the humid and cool-temperate south. Indeed, many ancient lineages of the mixed paleoflora, as Araucariaceae, Cunoniaceae, Lauraceae, Myrtaceae, Monimiaceae, Nothofagaceae, and Podocarpaceae, can still be found in southern South America despite the drastic changes that took place during the Paleocene [ 8 ].

During the Cenozoic Paleocene-Eocene Thermal Maximum, the Austral-derived flora started a migration toward lower latitudes, reaching the southern borders of the tropics.

This process continued during the subsequent warming events until the Early Eocene Climatic Optimum, when both temperate and tropical forests expanded and experienced intense in situ speciation events. Despite the high speciation rates in the tropics, such processes also took place independently along the latitudinal gradient beyond its limits, leading to a specially diversified set of clades.

The already recognizable Neotropical rainforests were also expanding, with a few lineages reaching the extratropical South America, and, at the same time, elements of the Northern Hemisphere were also reaching the tropics after the uplift of the Mesoamerican isthmus [ 8 , 17 ].

With the rise of the Andean Chain in the Neogene, new marked changes took place in the South America flora. In the South, many lineages became restrict to the pacific side of the mountains, as well as extinction processes occurred e. Further climate changes along Neogene and Pleistocene drove the consolidation of the RF and SDF nuclei, despite their areas waxed and waned following the fluctuations of both rainfall and temperature.

They were probably not continuous at that or any other time, which is reflected on the current scarcity of widespread species throughout SDF islands [ 7 ]. Yet, the presence of many populations at the same SDF nuclei for many million years indicates that core areas have been preserved over time. Nonetheless, it is very likely that SDF had expanded into RF domains along both the Pleistocene and the late Holocene Last Glacial Maximum, favored by the cooler and dryness of such periods.

Rain forest areas, unlike those of SDF, used to diminish during the Quaternary glaciations, when they became, at higher or lower levels, fragmentated and confined into refugia islands [ 20 , 21 ]. The matrix surrounding these patches suffered varied alterations, with part remaining forest SDF and part being covered by other vegetation types, particularly grasslands and savannas.

Migrations across South America indeed occurred during such periods, including the establishment of the Andean Alnus and Podocarpus into the central Amazonian lowlands.

Because of the reduced temperatures, precipitation, and atmospheric CO 2 of the Last Glacial Maxima, the Amazonian forests were less productive, had lower canopy structure, and were floristically and distinct than those of today. The basin area was predominantly covered by forests and was affected in different ways by the climatic changes. Such processes probably influenced the present gradient of RF biodiversity within the basin.

On the Late Holocene, RF reached their widest distribution, as a response to the increased precipitation caused by greater austral summer insolation. In the following dry periods of the early-mid Holocene, such forests contracted again until reaching the current configuration—or that of the European arrival [ 19 , 24 ]. Rain forests of the Atlantic domain were also impacted by the Pleistocene and Holocene climatic fluctuations, provoking the emergence of many C4 lineages during the drier periods, especially at the Last Glacial Maxima.

After that, Atlantic RF experienced a big expansion and had the representativeness of gymnosperms diminished, being likely, then, that Atlantic Forests reached its modern floristic composition on the early Holocene [ 25 , 26 ]. For example, the dispersal processes of the zoochorous species were probably affected, particularly for those bearing large fleshy fruits, perhaps leading to the extinction of part of them.

Quaternary fires might have partially and temporarily suppressed or disturbed specific regions of RF, which are nowadays less diverse. Contrary to what one may think, this process probably has not favored SDF establishment, which is indicated by the absence of fire adaptations in their present-day flora [ 7 ].

Nonetheless, the anthropogenic impacts that took place afterward certainly surpassed by far those promoted by fire, with significant suppression of both SDF and RF registered since the development of the first American cultures. Besides this, such processes were greatly intensified after Spanish and Portuguese occupation, when RF exploration was also initiated [ 13 , 14 ]. Changes in such vegetations are still occurring in an accelerated rate, and increasing our knowledge on the response of NF to these threats is urgent whether we are legitimately interested on their conservation.

Notwithstanding the fact that the plant cover has gone through striking variation along the geological eras, forests were always well represented in the Neotropics.

In fact, Europeans found massive extents of forests in both Meso and South Americas, when they arrived in those continents Figure 2. The distribution pattern of both RF and SDF of that period can still be noted, although much of the plant mass has been depleted or modified in structure and connectivity. In general terms, RFs are found in areas with humid climates, independently of pedologic traits or flooding regimes [ 9 ].

Contrastingly, drier areas with low ground water and fertility are usually covered by either savannas or grasslands. The scattered distribution SDF concentrates across the so-called Pleistocene Arc that surrounds the Amazon basin before stretching into Mesoamerica and the Caribbean [ 11 , 15 , 30 ]. Extent and geographical distribution of Neotropical forest domains solid patches; discontinuity within domains are not considered and incursions in other domains spotted areas.

Species composition and richness, however, vary widely in the region, with a notable increase in species richness toward the Andes [ 31 ]. Some of these families are distributed in abundance gradients along the whole Amazonian region.

In small scales, some families can show distinct distribution patterns, as that found for Lecythidaceae in French Guyana [ 32 ].

The second largest extent of RF is found along the South American Atlantic coast, namely the Atlantic domain, which extends from north-eastern Argentina and eastern Paraguay to north-eastern Brazil Figure 2. Therefore, the Atlantic domain harbors not only RF but also other vegetation types, particularly where it finds its environmental limits.

The following main types of RF may be distinguished accordingly: rain, cloud, rocky cloud, and Araucaria mixed forests, which are considered the core area of Atlantic forests. Many species from the Atlantic SDF and, less frequently, from the RF are found on the tropical and subtropical riverine forests that extend into the neighboring drier domains.

Additionally, several species from the Amazonian RF are found in those riverine forests, which can be considered a floristic link among all disjunct South American RF [ 9 , 35 ]. Several clades have their species concentrated in or confined to Neotropical SDF. Even when polyphyly is noted, the sister species are often found in the same region, indicating a high geographic phylogenetic structuration.

Besides that, the endemics tend to be abundant, resulting in a metacommunity pattern of high mid abundance levels [ 7 ]. There is a notable discontinuity among SDF islands, apart from both extremes of the Dry Diagonal, namely the Caatinga and Chaco domains, in north-eastern and central-southern South America, respectively Figure 2 [ 36 ].

Within SDF domains, soil traits can be very important to determinate the deciduousness degree, with evergreeness as an efficient strategy to save input nutrients under oligotrophic conditions [ 37 ]. Significant floristic differences are currently found among the three domains in the region, namely the Caatinga, Chaco, and Cerrado, which is the Brazilian savannas domain, where many incursions of SDF are found [ 36 ]. In some cases, the number of endemics can be high, as in Caatinga, within which a rocky portion can be discriminated due to the abundance of some species, belonging to four families: Cactaceae Brasilicereus phaeacanthus , C.

In the case of the Cerrado, the number of generalists is increased because of the numerous tree species shared with the co-occurring savannas and riverine forests, which contribute to the higher species richness in the domain. A number of species are common throughout the Dry Diagonal, such as Anadenanthera colubrina , Myracroduon urundeuva , Handroanthus impetiginosus , Aspidosperma pyrifolium , Senegalia polyphylla , Amburana cearensis , Schinus brasiliensis , Annona leptopetala , and Platymiscium floribundum.

The remaining South American SDFs, occurring from northern Argentina to the Caribbean coast of Colombia and Venezuela, show similar patterns, despite the occurrence of a few distinct species groups.

However, there is also a great floristic variation as only a third of the botanical families are found throughout.

This includes, for instance, increasing abundances toward the east of Acacia tamarindifolia , Amaioua guianensis , Bourreria cumanensis , Bunchosia mollis , Bursera simaruba , Capparis verrucosa , C. The north also includes Bourreria succulenta , Helietta pleeana , Krugiodendrum ferreum , Linociera caribaea , Pseudobombax septenatum , Zizyphus cinnamomum , and the association of Bursera and Lonchocarpus , which are also very common in the Caribbean but rare across Venezuela.

At the same time, many of the major tropical clades as Anacardiaceae, Annonaceae, Meliaceae, Moraceae, and Sapotaceae are absent in temperate lands. In this way, many lineages, such as Aextoxicon , Citronella , Cryptocarya , Drimys , Gomortega , Laurelia, Persea , Laureliopsis , Legrandia , Nothofagus , Pitavia , and Podocarpus , have diversified outside the tropics, keeping their ancestral preference for temperate conditions.

There is a high floristic uniqueness in both the tropical and temperate NF, with species richness by far higher in the former due to higher speciation and lower extinction rates overtime.

On the other hand, the temperate flora has a higher lineage diversity, that is, richness of ancient clades [ 10 ]. For example, warmer temperatures and higher rainfall increase species richness for both Leguminosae and Bignoniaceae, cooler temperatures for Asteraceae and Melastomataceae, and dryness for Polygonaceae, while abundance is favored by lower temperatures for Melastomataceae and Rubiaceae and higher precipitation for Arecaceae [ 39 ].

However, to our knowledge, there are no studies on the main modulators of the present-day clade distribution for the temperate Neotropics. The main driver of forest type distribution across the Neotropics is the rainfall regime, although the temperature plays a major role in the subtropical and temperate sectors [ 18 ].

Indeed, rainfall itself controls forest structure, species richness, and successional dynamics. Together with soil fertility and landscape heterogeneity, temperature has also a positive correlation to taxonomic structural complexity, expressed as an increasing gradient of species, genera, and families richness from SDF to RF [ 35 , 38 , 40 ].

Species richness among SDF islands is poorly affected by changes in the amount of precipitation; otherwise, water restriction seems to be very important for the maintenance of SDF patches, preventing the establishment of RF [ 7 , 35 ].

Several climatic features also modulate species distribution at and within regional levels. For example, temperature seasonality is the main controller of tree species composition in the subtropical sector of the Atlantic domain, particularly segregating Araucaria-dominated forests [ 18 ].

In the tropical sector, water deficit severity and mean annual precipitation are the best predictors of changes in species composition, segregating two main floristic groups, containing a rain, cloud, and cloud dwarf-forests and b riverine and semideciduous forests and campos rupestres [ 29 ]. Additional roles are played by fire and frost frequency in segregating the woody flora of rock outcrops, as does strong winds and salt-spray for coastal white-sand woodlands.

Likewise, rainfall patterns are the main controllers of species richness across the Amazon domain, with higher figures in the much rainier west and center than in the seasonal and drier east and south [ 19 , 31 ]. The existence of forests across the Dry Diagonal depends basically on two factors: higher soil moisture on valley bottoms harboring riverine seasonal forests and patches higher fertility soils covered on either deciduous or semideciduous forests [ 9 ].

On top of this, climate features play an additional role, affecting the species composition of SDF across the whole Diagonal, and extremes of cold temperatures and dry season severity are key factors. Nonclimatic environmental traits, such as space, altitude, substrate, topography, soil composition, as well as anthropic impacts, are very important in determining NF types across other geographic regions.

In this way, in north-western Argentina, the chief explanatory variables for species distribution on the Andean piedmont slopes are related to increasing moisture and decreasing temperature toward higher altitudes [ 41 ]. For example, the moister the area, the higher the abundance of Diatenopteryx sorbifolia , Ocotea puberula , Cordia americana , and Eugenia uniflora , while the opposite pattern is shown by Calycophyllum multiflorum , Phyllostylon rhamnoides , Astronium urundeuva , and Anadenanthera colubrina.

Lecythidaceae and Caesalpinioideae are predominant in the coastal plains and hilly hinterlands, while Burseraceae, Vochysiaceae, Simaroubaceae, and Mimosoideae are predominant in valley bottoms.

The tropical rainforest is a mysterious, lush landscape of dense jungle and tall canopy trees that harbors millions of species of wildlife, plants and microorganisms. Belizean Coast mangroves. Rhinoceros Beetle. Belizean Reef mangroves. Argentina , Brazil , Uruguay.

Neotropical rainforest climax trees

Neotropical rainforest climax trees. General Tropical Tree Facts

A flowering tree, the kapok is harvested for its tough fibers that can be spun into rough fabric or stuffing. Strangler figs are tropical trees found all over the equatorial zone of the world as far north as the state of Florida.

These trees cling to life under the dense rainforest canopy by attaching their root structure to a host tree and growing around and inside of the host to gain water and other nutrients. Receiving its name from the "strangling" way it clings to and eventually kills a host tree, the strangler fig starts its life cycle on the top of the forest canopy, rather than on the floor. Growing roots downward toward to soil, the high perch of the strangler fig means it doesn't have to compete for light.

Cecropia trees are relatively small, exceedingly common rainforest trees that grow quickly and are used by animals and people. These trees produce long, plump fruits that transmit seeds through animal digestive tracts that arrive at their newly fertilized growing area at a greater distance from the parent tree than wind or water could carry them. Used by humans for wood, sandpaper and even rope products, the strong fibers of the cecropia tree make them useful to natives. The trees' rapid life cycle also make them the first trees to colonize areas that have suffered deforestation or land clearance.

Kauri trees, found in New Zealand's rainforest canopies, are extremely large, ancient trees that can live for over a thousand years. Costa Rica , Nicaragua. Eastern Cordillera Real montane forests. Colombia , Ecuador , Peru. Eastern Panamanian montane forests.

Colombia , Panama. Fernando de Noronha-Atol das Rocas moist forests. Guayanan Highlands moist forests. Brazil , Colombia , Guyana , Suriname , Venezuela. Guianan piedmont and lowland moist forests. Brazil , Venezuela. Hispaniolan moist forests. Dominican Republic , Haiti. Bolivia , Brazil , Peru.

Isthmian-Atlantic moist forests. Isthmian-Pacific moist forests. Costa Rica , Panama. Jamaican moist forests. Brazil , Colombia , Venezuela. Leeward Islands moist forests.

Bolivia , Brazil. Magdalena Valley montane forests. Mato Grosso tropical dry forests. Negro-Branco moist forests. Northeastern Brazil restingas. Northwestern Andean montane forests. Colombia , Ecuador. Oaxacan montane forests. Orinoco Delta swamp forests. Guyana , Venezuela. Paramaribo swamp forests. Guyana , Suriname. Argentina , Brazil , Paraguay. Pernambuco coastal forests. Pernambuco interior forests.

Puerto Rican moist forests. Purus-Madeira moist forests. Rio Negro campinarana. Santa Marta montane forests. Serra do Mar coastal forests. Sierra Madre de Chiapas moist forest. El Salvador , Guatemala , Mexico. Brazil , Colombia , Peru. South Florida rocklands. Southern Andean Yungas. Argentina , Bolivia. Southwest Amazon moist forests. Talamancan montane forests. Brazil , Guyana , Suriname , Venezuela. Trinidad and Tobago moist forests.

Trindade-Martin Vaz Islands tropical forests. Uatuma-Trombetas moist forests. Brazil , Guyana , Suriname. Venezuelan Andes montane forests. Veracruz moist forests. Veracruz montane forests. Western Ecuador moist forests. Windward Islands moist forests. Xingu-Tocantins-Araguaia moist forests. Belize , Guatemala , Mexico. Apure-Villavicencio dry forests. Bolivian montane dry forests. Cauca Valley dry forests. Cayman Islands dry forests. Central American dry forests. Argentina , Bolivia , Paraguay.

Chiapas Depression dry forests. Guatemala , Mexico. Chiquitano dry forests. Ecuadorian dry forests. Hispaniolan dry forests. Jalisco dry forests. Leeward Islands dry forests. Anguilla , Antigua and Barbuda , Montserrat. Magdalena Valley dry forests.

Panamanian dry forests. Puerto Rican dry forests. Revillagigedo Islands dry forests. Sierra de la Laguna dry forests. Sinu Valley dry forests. Southern Pacific dry forests. Trinidad and Tobago dry forests. Tumbes-Piura dry forests. Windward Islands dry forests. Belizian pine forests. Central American pine-oak forests.

Hispaniolan pine forests. Haiti , Dominican Republic. Miskito pine forests. Honduras , Nicaragua. Sierra de la Laguna pine-oak forests.

Sierra Madre de Oaxaca pine-oak forests. Sierra Madre del Sur pine-oak forests. Trans-Mexican Volcanic Belt pine-oak forests. Juan Fernandez Islands temperate forests. Magellanic subpolar forests. Argentina , Chile.

Valdivian temperate rain forests. Bolivia , Brazil , Paraguay. Clipperton Island shrub and grasslands. Brazil , Guyana , Venezuela. Los Llanos. Venezuela , Colombia. Argentina , Brazil , Uruguay. Argentina , Uruguay.

Central Mexican wetlands. Cuban wetlands. Enriquillo wetlands. Guayaquil flooded grasslands. Southern Cone Mesopotamian savanna. Central Andean dry puna. Argentina , Bolivia , Chile. Argentina , Bolivia , Peru. Central Andean wet puna. Talamanca Paramo. Southern Andean steppe. Mexico , Guatemala. Araya and Paria xeric scrub.

Cayman Islands xeric scrub. Guajira-Barranquilla xeric scrub. La Costa xeric shrublands. Leeward Islands xeric scrub. Malpelo Island xeric scrub. Windward Islands xeric scrub. Saint Peter and Saint Paul Archipelago. Alvarado mangroves.

Rates of change in tree communities following major disturbances are determined by a complex set of interactions between local site factors, landscape history and structure, regional species pools and species life histories. We consider five tree community attributes: stem density, basal area, species density, species richness and species composition.

We describe two case studies, in northeastern Costa Rica and Chiapas, Mexico, where both chronosequence and annual tree dynamics studies are being applied. These case studies show that the rates of change in tree communities often deviate from chronosequence trends.

Dynamic changes in basal area within stands, on the other hand, generally followed chronosequence trends. Stem turnover rates were poor predictors of species turnover rates, particularly at longer time-intervals. Effects of the surrounding landscape on tree community dynamics within individual plots are poorly understood, but are likely to be important determinants of species accumulation rates and relative abundance patterns.

Vegetation does not really consist of climaxes and successions leading towards them. In a long-range perspective, the vegetation of the Earth's surface is in incessant flux; what we observe in the field are not simply successions and climaxes, but only different kinds and degrees of vegetational stability and instability, different kinds and rates of population change.

Whittaker , p. Structure and dynamics of forest vegetation reflect a complex interplay of disturbance events and regeneration processes taking place through time and space Chazdon Rates of change, however, vary considerably, depending upon what forest attributes are being measured and upon the intensity, duration and frequency of the disturbance.

Ultimately, rates of forest change following major disturbances are determined by a complex set of interactions between local site factors, landscape history and structure, regional species pools including non-native species and species life histories Pickett et al. In this review, we define major disturbances as those that result in the complete or nearly complete removal of vegetation, leading to the establishment of even-aged regrowth. These disturbances may occur at a range of spatial scales, from large gaps in a forest matrix, to small swidden agriculture fields, to large-scale deforestation.

Resprouting is the predominant form of regeneration following damaging windstorms, such as hurricanes or cyclones Yih et al. When residual vegetation and propagule sources are lacking, destroyed by fires, or when soils are highly disturbed or compacted by heavy grazing, bulldozing or high-impact logging, rates of forest regrowth and biomass accumulation decline; under extreme conditions, successional processes may be arrested or diverted by exotic species Hjerpe et al.

To add further complexity, site factors such as soil fertility and texture interact with landscape factors, such as forest cover spatial organization and extent, distance to forested areas and regional species pool, to determine rates of species colonization, accumulation of species and accumulation of biomass above- and belowground Johnson et al.

A complete understanding of the factors that influence forest vegetation change following major disturbances in tropical forests must incorporate analyses of site attributes as well as landscape configuration and regional species composition. These effects are not exclusively unidirectional, as secondary forest development can influence species composition and genetic structure of populations in nearby mature forests as well as in surrounding areas undergoing succession U.

Sezen , unpublished work. As stated by Pickett , p. Successional processes are not always directional or predictable, and multiple pathways can lead to a range of mature forest types rather than a single stable endpoint Gleason Here, we describe the succession process in terms of rates of change in tree community attributes rather than as a recovery process, thereby avoiding the assumption that succession is orderly or deterministic and will eventually reach the original forest structure and species composition present before the disturbance.

Two general approaches have been used to assess rates of vegetation change during succession. Rates of change are therefore estimated indirectly, based on assumptions that the same successional process takes place within each stand.

The second approach directly documents the rates of change through monitoring vegetation dynamics over time in particular forest stands. We then examine whether chronosequence trends can predict tree community changes as observed within individual secondary forest stands over time.

We consider two case studies, from northeastern Costa Rica and Chiapas, Mexico, where both approaches are being applied in long-term studies of successional permanent plots. Since chronosequence studies are based on single-time information from a range of sites, these data emphasize cumulative or net effects of ecological processes. We examine rates of change for five tree community attributes: stem density; basal area; species density; species richness; and species composition.

In two case studies, we examine turnover rates of stems and species for different size classes and time-scales. Stem density and basal area are influenced by rates of tree growth, recruitment and mortality, whereas species density, richness and composition reflect processes of species turnover and community assembly.

Collectively, these processes determine changes in species relative abundance, size distributions and dominance over time. When assessing vegetation change in successional tropical forests, the standard for comparison is usually neighbouring areas of mature or old-growth forests.

Many secondary forests are found in small patches isolated from continuous forest cover. As a result, it remains a major challenge to obtain robust data on vegetation change in secondary forests that matches the spatial extent of data collected for mature forest tracts, which are generally larger areas at least for those that are investigated in ecological studies and may therefore encompass greater edaphic heterogeneity.

Originally framed as a tool for investigating primary succession, chronosequence studies have become a key component of research on secondary forest succession. However, chronosequence data only permit inferences of successional change and do not facilitate direct analysis of the underlying processes mediating the change growth, mortality and recruitment. In addition, the basic assumption of chronosequence studies—that the sites represent points along a continuum, rather than snapshots of independent trajectories—often remains untested.

Chronosequence sites must be carefully chosen to avoid bias in site selection. The best chronosequence studies are those that base their site selection on precise, independently verifiable estimates of site age. For example, Ruiz et al. Ideally, site selection should remain unbiased by prior notions of successional rates, topography or ease of access, although these factors often restrict available study areas. Chronosequence studies have contributed valuable data used to infer rates of vegetation change in regenerating tropical forests.

Both are generally calculated from stem diameters, but the equations used for ABM are often site specific e. Brown ; Nelson et al. For both ABM and basal area, secondary tropical wet forests exhibit rapid growth in the first years of establishment.

Pascarella et al. Saldarriaga et al. The pantropical average rate of biomass accumulation in the first 20 years of forest succession has been estimated to be 6. In contrast to the linear increases in ABM found in other chronosequence studies, Jepsen reported sigmoidal increase in biomass accumulation in swidden fallows from 2 to 15 years old in Sarawak Malaysia, with initially rapid biomass growth up to 10 years followed by no net biomass accumulation.

Based on fitted functions, biomass accumulation reached a maximum rate of The growth of secondary forests can be strongly affected by soil fertility Moran et al. Swidden fallows and abandoned pastures may follow very different successional trajectories Uhl et al. Successional changes in stem density may be driven by intrinsic species life-history differences e.

Species life-history attributes can lead to episodic recruitment and the development of strong cohort structure in young secondary forests.

For example, in the Neotropics, initial colonization is often dominated by relatively short-lived, fast-growing, pioneer genera such as Cecropia , Vismia and Ochroma Finegan ; Vester ; Mesquita et al. When these species die off after 25—30 years, or sometimes much earlier, stem density may decline rapidly see Breugel et al.

Mortality and recruitment processes in mature tropical forests are often density- or frequency dependent Wills et al. The importance of density-dependent effects on stem density and species composition in tropical secondary forests remains unclear, however, due to the paucity of published information from permanent sample plot studies.

Breugel et al. A concentration of growth in the larger trees and relatively high mortality among the smaller trees indicated asymmetric competition, and the resulting pattern of tree thinning strongly influences vegetation dynamics in early succession. Successional changes in density of both trees and regenerating seedlings and saplings may indicate the potential for density-dependent effects on mortality, growth and recruitment Uriarte et al.

The relative importance of conspecific versus heterospecific effects of density on tree regeneration also remains to be determined in tropical secondary forests Uriarte et al. Since shade-tolerant tree species are not yet reproductively mature in young stands, seeds must be dispersed from nearby or distant mature forests or forest fragments.

The lack of locally produced seed shadows decreases the potential for conspecific density-dependent effects on seedling recruitment and growth Janzen ; Connell ; Uriarte et al. Unlike basal area and ABM, stem density does not appear to follow a predictable pattern with forest age. Density is potentially influenced by a wide variety of factors, operating at a range of spatial and temporal scales that vary in their effects on different size classes. Stem density in secondary forests is generally higher than in old-growth forests, even when comparing relatively large size classes e.

Stem density may peak at an intermediate age range, although these patterns will vary with diameter size limits. Feldpausch et al. In Puerto Rico, stem density greater than 2.

As the forest develops, new species begin to colonize and recruit, leading to a gradual accumulation of species over time. Species density is highly sensitive to stem density Denslow ; Chazdon et al. An alternate approach is to use an index such as Shannon's H or Fisher's alpha to assess species diversity; these measures can also be influenced by sample size, however.

Numerous studies have documented increasing diversity with forest age, although direct comparisons are difficult due to lack of standardization of diversity measures see reviews by Chazdon in press , Holl in press. Aide et al. Sheil applied rarefaction methods to these data to correct for differences in stem density and confirmed the mid-successional peak. Andel found higher diversity Fisher's alpha in old secondary forests in northwest Guyana than in neighbouring old-growth forests. Rates of species accumulation are often slower on abandoned pasture compared with abandoned crop cultivation in regenerating forests of Puerto Rico Aide et al.

Whereas species density may quickly reach the level of old growth, species composition remains distinct for much longer or may never fully recover Corlett ; Clark ; Finegan The legacy of early species colonization may persist for decades or even centuries, as some pioneer species can be very long lived Budowski ; Gemerden et al. One of the central questions regarding forest succession is whether floristic change follows a predictable pathway. The species composition of each wave is predictable, as is the sequence of replacement.

Neither of these models adequately describes actual trends in species composition in successional tropical forests, however.

Few chronosequence studies support the relay floristics model, although many species of early successional pioneers fail to recruit after canopy closure Finegan ; Chazdon in press ; Holl in press ; Breugel et al. Studies in eastern Amazonia, Bolivia, and Mexico found that species from all functional groups including shade-tolerant species established very early in succession and continued to establish after canopy closure Uhl et al.

In Mesoamerica, studies of tree life histories have revealed a number of distinct functional groups of tree species, which become abundant during different phases of succession Budowski , ; Finegan , ; Dalling et al. The resulting waves of recruitment and mortality may lead to wide fluctuations in stem density and may also account for the observed mid-successional peak in species richness Sheil The initial floristic composition of successional forests may influence species composition for long periods of time, though the effects of early species composition are often confounded with those of prior land use.

In the Brazilian Amazon, researchers have identified two different floristic pathways on abandoned lands. Vismia species, in contrast, are longer lived and resprout frequently and may arrest the floristic turnover Vester ; Steininger ; Mesquita et al. Detailed long-term studies are needed to evaluate the influence of land-use history and initial floristic composition on successional pathways and species turnover.

An important question in forest regeneration is whether secondary forests converge with the vegetation of nearby old-growth forests or whether the community composition remains distinct.

Terborgh et al. A key factor in convergence here, however, would seem to be that the regional context of this study was that of forest cover with little or no human disturbance. Sheil re-evaluated Eggeling's plots in Budongo Forest, Uganda, and also detected directional changes in floristic composition conforming to Eggeling's predicted successional trajectory. In other situations, the outcome of succession is less clear with measurable differences in floristic composition persisting for up to centuries after abandonment Corlett ; Clark ; Finegan ; Gemerden et al.

Neotropical rainforest climax trees

Neotropical rainforest climax trees

Neotropical rainforest climax trees