Non-pioneer Species Research Articles

Climbers and logging in the Forêt Classée du Haut-Sassandra, Côte-d’Ivoire

In this study we compare climber abundance and size in centres of post-logging skid tracks and log loading areas to their adjacent relatively undisturbed border zones, in a selectively logged forest in the west-centre of Côte d’Ivoire. We also evaluate the effect of time after logging (age) on these climber parameters. In 19 plots, 3 months to 17 years after logging we counted and measured climber individuals and shoots by species. Skid tracks and loading areas had similar abundance and size of climbers, only the densities of herbaceous species and of pioneer species were both higher in loading areas. Skid tracks had the same abundance and size of climbers as their adjacent border areas. Densities of long climbers (>3 m length), woody species and non-pioneer species were higher in the border areas, and densities of herbaceous species and pioneer species were lower, compared to centre areas. With the exception of density of long climbers (higher in the border areas), climber abundance and size in loading areas were similar to those in their adjacent border areas. Climber species richness in skid tracks decreased with time after logging. All other climber parameters studied were not correlated with time after logging. We conclude that despite the mechanical damage in logging related areas most climbers were not much affected, and that time since logging only affects climber species richness in skid tracks.

Light environment and tree strategies in a Bolivian tropical moist forest: an evaluation of the light partitioning hypothesis

Light partitioning is thought to contribute to the coexistence of rain forest tree species. This study evaluates the three premises underlying the light partitioning hypothesis; 1) there is a gradient in light availability at the forest floor, 2) tree species show a differential distribution with respect to light, and 3) there is a trade-off in species performance that explains their different positions along the light gradient. To address these premises, we studied the light environment, growth, and survival of saplings of ten non-pioneer tree species in a Bolivian moist forest. Light availability in the understorey was relatively high, with a mean canopy openness of 3.5% and a mean direct site factor of 6.8%. Saplings of two light demanding species occurred at significantly higher light levels than the shade tolerant species. The proportion of saplings in low-light conditions was negatively correlated with the successional position of the species. Light-demanding species were characterised by a low share of their saplings in low-light conditions, a high sapling mortality, a fast height growth and a strong growth response to light. These data show that all three premises for light partitioning are met. There is a clear gradient in shade-tolerance within the group of non-pioneer species leading to a tight packing of species along the small range of light environments found in the understorey.

GETTING TO THE CANOPY: TREE HEIGHT GROWTH IN A NEOTROPICAL RAIN FOREST

There is still limited understanding of the processes underlying forest dy- namics in the world's tropical rain forests, ecosystems of disproportionate importance in terms of global biogeochemistry and biodiversity. Particularly poorly documented are the nature and time scale of upward height growth during regeneration by the tree species in these communities. In this study, we assessed long-term height growth through ontogeny for a diverse group of canopy and emergent tree species in a lowland neotropical rain forest (the La Selva Biological Station, northeastern Costa Rica). Species were evaluated based on annual height measurements of large samples of individuals in all postseedling size classes, over a 16-yr period ( .11 000 increments). The study species were seven nonpi- oneers (Minquartia guianensis, Lecythis ampla, Hymenolobium mesoamericanum, Sima- rouba amara, Dipteryx panamensis, Balizia elegans,and Hyeronima alchorneoides ) and two pioneers (Cecropia obtusifoliaand Cecropia insignis). For each species, inherent height growth capacity was estimated as the mean of the five largest annual height increments (from different individuals) in each juvenile size class (from 50 cm tall to 20 cm in diameter). All species showed marked ontogenetic increases in this measure of height growth potential. At all sizes, there were highly significant differences among species in height growth potential. The two Cecropia species consistently showed the highest observed maximum height increments as smaller juveniles (#4 cm in diameter). Among the nonpioneers, Sim- arouba had the highest growth potential across all juvenile sizes. For all species, mean annual height increments in all juvenile size classes were very much lower than the species' potential growth rates and reflected the impacts of frequent periods of zero growth and major height losses from physical damage. Because of the same factors, maximum net height increments declined over increasing measurement intervals (1-15-yr periods). With only one exception (Simarouba amara saplings #1 cm in diameter that survived 10 yr), the annual height growth increments of these species showed no significant temporal au- tocorrelation. For the seven nonpioneer species, we estimated the minimum time required to grow from 50 cm tall saplings to 10 cm diameter trees, based on their greatest net height increments over increasing intervals. Estimated passage times increased from 7-33 yr, when based on maximum 5-yr height increments, to 37-83 yr, when based on maximum net height growth over 15 yr for the six longest studied (nonpioneer) species. Given the erratic height growth trajectories found for these juvenile trees in this 16-yr study, it is clear that much longer term observation is required. Still unknown are the actual growth trajectories that characterize successful regeneration in each of our focal species, how much time successful trees spend as suppressed juveniles, and the number of times they experience and recover from major physical damage.

Leaf herbivory on three tree species in a monodominant and two other Terra firme forests on Maracá Island, Brazil

The aim of this study was to test the hypothesis that the monodominant non-pioneer Peltogyne gracilipes, typically does not suffer density-dependent herbivory (Janzen-Connell model). Two components of intraspecific variation in leaf herbivory were measured: 1) the variation between individuals in the population at the same time and 2) the temporal variation in rates of damage to each individual. The study was carried out on Maracá Island, Roraima, Brazil in three plots (50 m χ 50 m) in each of three forest types: Peltogyne-rich forest (PRF), Peltogyne-poor forest (PPF), and forest without Peltogyne (FWP). Two other non-pioneer species (Ecclinusa guianensis and Pradosia surinamensis) were chosen for comparison because they were fairly abundant and their seedlings could be readily identified. The values of leaf area removed by herbivores of trees and seedlings of the three study species were in the range reported for other tropical tree species (2-16%, standing damage). There were no differences within species between forests. However, there was a significant difference among species but this was not correlated with seedling density. Peltogyne seedlings showed no evidence of density-dependent herbivory as predicted by the Janzen-Connell model despite the fact that adult trees were observed to suffer a mass defoliation in April 1992. This result suggests that Peltogyne may be dominant partly due to escape from herbivory in the early stages of its life although it may suffer occasional mass defoliation as an adult.

ASSESSING THE GROWTH OF TROPICAL RAIN FOREST TREES: ISSUES FOR FOREST MODELING AND MANAGEMENT

Growth performance was assessed for a diverse suite of canopy and emergent tree species in a lowland neotropical rain forest (the La Selva Biological Station, northeastern Costa Rica). Species were evaluated based on annual diameter measurements of large samples of individuals in all post-seedling size classes, over a 12-yr period. The study species were seven non-pioneers (Minquartia guianensis, Lecythis ampla, Hymenolobium mesoamericanum, Simarouba amara, Dipteryx panamensis, Pithecellobium elegans, and Hyeronima alchorneoides) and two pioneers (Cecropia obtusifolia and C. insignis). For each species, inherent growth capacity through ontogeny was estimated as the mean of the five largest annual increments (from different individuals) in each juvenile and adult size class. At all tree sizes, species differed highly significantly in this measure. In the small sapling sizes (≤4-cm diameter), the two pioneers showed markedly higher maximum growth than all the non-pioneers, in line with current understanding. This growth advantage, however, was quickly lost with increasing tree size. For eight of the nine species, the ontogenetic patterns of maximal growth closely corresponded to species groupings previously based on juvenile microsites (forest stage, light levels). Average growth rates, however, which are the combined result of environmental and biotic factors, did not show this correspondence. The groups based on microsite occupancy and growth potential provide a starting point for treating the great numbers of species of tropical rain forest trees as many fewer functional types, a sine qua non for modeling these complex forests. The exceptional growth capacity of one of our focal non-pioneer species (Simarouba) suggests that it represents a hitherto unrecognized functional type among tropical rain forest trees. The data from this long-term study indicate that several assumptions of current forest-dynamics models are not applicable to trees of this biome. For most species (1) diameter growth during regeneration was not correlated with tree size; (2) adult sizes were not characterized by a constant maximal basal-area increment; and (3) growth capacity did not decline toward zero as trees approached maximum size. Evaluation of overall increment distributions revealed a broad adult size range of exclusively high growth in the emergent Hymenolobium; for two additional species, sectors of the adult size range showed an absence of very low or negative growth. At most sizes, however, all nine species displayed the full range of growth increments, from slightly negative to observed maxima. Describing the performance of tropical rain forest canopy trees will require similar analysis of growth data obtained from many individuals and intervals, and stratified across juvenile and adult life stages. More realistic forest-dynamics models will depend on such evaluations of many tree species, in diverse tropical rain forests. Such models are greatly needed, both for designing management for this biome and for predicting its responses to changing climate and atmospheric conditions.

Seed rain from forest fragments into tropical pastures in Los Tuxtlas, Mexico

Deforestation has resulted in the fragmentation of forests. Remnant fragments are widely assumed to be sources of seeds for forest regeneration in abandoned pastures. The seed rain in 12 pastures at Los Tuxtlas, Mexico, their relationship with riparian vegetation adjacent to them, and their closeness to the reserve is described. For all the species found in the seed rain, we classified them by typical habitat (pasture or rain forest), life form, dispersal syndrome, and plant strategy (pioneer or non-pioneer species). In addition, germinability was evaluated for all seeds. We also assessed the correlation in composition of the seed rain and the riparian vegetation. Only 11% of the total species that occur in the Los Tuxtlas region reach pastures via dispersal from forest fragments. However, nearly 80% of the species in the seed rain did not come from the fruiting individuals in the adjacent riparian vegetation. The proportion of dispersal syndromes, life forms and plant strategies of the species in the seed rain was similar to those observed in the rain forest. On average, the germinability of forest species was less than 30%.

Changes of community characteristics of a broad-leaved-conifer mixed forest after selection cutting

The modification in structure, composition, and diversity, shrub, as well as herb strata ofPinus koraiensis-Tilia amurensis-Abies nephrolepis forest after 16a of selection cutting in northeastern China was studied. In the selection cutting forest, individuals with small DBH classes characterized size distribution. The virgin forest, on the other hand, was mainly composed of individuals having larger DBH classes. The density of dominant species and the species diversity at tree stratum in the selection-cutting stand was significantly larger than that of in the primeval forest. The shrub layer also showed a similar result. However, the herb layer had comparatively low species diversity. Large growing space and strong light in the artificial gaps must have provided opportunities for the species of shade tolerance or shade intolerance to establish on the stand. The juveniles of non-pioneer species, which were hardly found in highly shaded virgin forest, were also released by the disturbance. Regeneration in the selection-cutting stand was prompted by the disturbance, where the density of saplings occurred nearly 3 times as much as that in the virgin stand. The growth of shrub layer was improved due to the alteration in light condition. The projection volume of the herb layer was less affected. Restoration of a semi-virgin forest to the original status after selection cutting could be possible in several decades. However, for those subjected to clear cutting, it might take several centuries. In order to promote biodiversity, it is reasonable to practice selection cutting in communities for consisting of species with various levels of shade tolerance.

Regeneration strategies of tree species in the laurel forest of Tenerife (The Canary Islands)

The laurel-forest of the Canary Islands is a montane cloud-forest. In order to gain some knowledge on the processes that maintain tree species diversity, we conducted an analysis of three different laurel-forest plots of the Anaga massif (Tenerife), varying in canopy composition but growing under similar environmental conditions. For each plot we recorded basal area of the canopy trees (h 1.30 m), as well as seed-bank composition. The plots have similar regeneration composition, which appears to be independent of differences in canopy composition. Laurus azorica is the most common seedling species, whereas Prunus lusitanica is the most abundant species among suckers and basal shoots. Neither Erica arborea nor Myrica faya, the two main canopy trees in one of the plots, were found in any of the stands as seedlings or suckers, despite their existence as viable seeds in the seed-bank. The regeneration composition and the canopy composition in one of the plots is remarkable different, revealing differents dynamics processes in the three plots. The results suggest the existence of three well-defined ecological groups: pioneer (regeneration primarily by seedlings), non-pioneer (regeneration by seedlings and suckers) and remnant species (regeneration primarily by suckers).These three groups and the effect of small scale disturbances (natural and human-induced), could help to understand the maintenance of tree species richness.

Landscape-scale evaluation of understory light and canopy structures: methods and application in a neotropical lowland rain forest

Light is a key resource controlling tree regeneration in the understory of closed-canopy old-growth forests. To evaluate the distribution of understory light environments at a landscape scale, we used stratified random sampling in a 500-ha stand of Costa Rican tropical rain forest. Fifteen 100 m long transects were placed using random coordinates within two soil–geomorphology units (flat alluvial terraces and dissected ridge-slope-swale terrain). At 2.5-m intervals we measured canopy height and slope angle, classified topographic position, and took canopy photographs with a fish-eye lens at 1 and 3 m above the ground (and at 0.6 and 5 m height at five stations per transect). Photographs were analyzed for global site factor (GSF), which is analogous to the percentage of full sun radiation reaching a point. Canopy height and GSF at 1 and 3 m above the ground were significantly autocorrelated (Moran's I) at 2.5-m intervals. The autocorrelation rapidly declined at greater intervals, reaching nonsignificance at ca. 20 m. Both canopy height and GSF at 3 m height had a weak tendency for negative autocorrelations at intervals of 25–50 m. Median canopy height (615 stations) was 23 m (range 0–37). Gaps (canopy height ≤2 m, Brokaw 1982) were only 1.5% of sample points. Gaps were more frequent on steep slopes than on terraces, ridgetops, swales, and gentle slopes. Canopy height varied significantly across this topographic gradient. At all four heights (0.6, 1, 3, and 5 m) median GSF was ≤2.4%. GSF values >8% accounted for only 3% of the total sample (N = 1380). GSF was only weakly negatively correlated with canopy height and the relation was not monotonie. Under canopies 13-19 m tall, nearly all GSF values were ≤5%. Higher GSFs were more frequent under both shorter and taller canopies. Given the observed variance in GSF and canopy height, 100–200 points separated by intervals of ≥20 m are necessary to measure the forest-wide means of these variables to ±10%. We discuss implications of these results for current approaches to modeling understory light based on canopy characteristics. We compared the random background of light environments from 1–3 m above the ground at La Selva with those occupied by saplings of pioneer and nonpioneer tree species. The two pioneers (Cecropia spp.) occurred in microsites significantly brighter than random sites, while sapling microsites of all five nonpioneer species were significantly darker than random. Comparing the landscape-scale distribution of key resources with species' actual distributions at similar scales offers a quantitative method for assessing plant life histories within and among forests.

Classifying the life-history strategies of trees on the basis of the Grimian model

In forest succession studies, two major groups of tree species are usually recognized: pioneer and non-pioneer (climax) species. It is assumed that each group has its own set of adaptive traits that impart advantages or disadvantages to trees in early-and late-successional stages. In the present paper, the pioneer/climax concept is tested for 36 major European tree species, whose ontogenetic and ecological attributes (in total 21 variables) were compiled from the literature and analyzed by multivariate statistical methods. On this basis, a new ecological classification of tree species is proposed and interpreted in terms of the theoretical, triangular model of life-history strategies developed by Grime. For each type of life-history strategy (ruderal, stress-tolerant, competitive and intermediate), specific adaptations determining the functional roles of tree species in the dynamics of forest communities are identified and described.

Spatial Distribution Pattern of Representative Tree Species in a Foothill Rain Forest in West Sumatra.

Spatial distribution was analysed for all plot trees and representative tree species in two duplicate I-ha plots established in a foothill rain forest 16 km west from Padang, West Sumatra, Indonesia. All tree trunks ≥ 8 cm dbh were distributed randomly in both plots. Spatial correlation between dead trees and recruited trees during the 8-year period was locally negative while broadly positive, suggesting that the random spatial pattern is dynamically maintained by mechanisms of density-dependent regulation. All of five abundant canopy/subcanopy non-pioneer species, i.e. Hopea dryobalanoides, Gonystylus forbesii, Cleistanthus glandulosus, Mastixia trichotoma, and Grewia florida, and typical pioneer Macaranga spp., including M. gigantea, M. hypoleuca, M. pruinosa and M. triloba, showed a clumped distribution, particularly for smaller size classes. Two subcanopy non-pioneer species, Mastixia and Grewia showed a shift from a regularly decreasing density with height in one plot with larger gap area to bimodal height distribution in the other plot with smaller gap area. They also showed a similar tendency in spatial pattern such that the negative spatial correlation was observed between seedlings (

Comparative recruitment patterns of two non-pioneer canopy tree species in French Guiana.

A comparative study was conducted on the recruitment patterns of two non-pioneer tree species, one dispersed by arboreal mammals and birds (Virola michelii, Myristicaceae) and the other by rodents (Moronobea coccinea, Clusiaceae). These species differ in fruiting phenology, seed size, dispersal distance, germination time and seed nutrient exhaustion. In both species, establishment patterns were consistent with the escape hypothesis and the Janzen-Connell model. Virola seeds need not be buried to survive and germinate, and may produce a seedling carpet beneath the parent. Moronobea seedlings only establish from seeds buried by scatterhoarding rodents in the surrounding understory. One-year survival of Virola seedlings was 47.8% and was greater >10 m than < 10 m from the largest parent tree. In contrast, survival of Moronobea seedlings was 56% 3 years after seed dispersal. Survival of juveniles was greater in gaps than in the understory for Virola but not for Moronobea. Moronobea survival was greater than Virola survival in both microhabitats. Both species establish in the understory, yet both grew faster in gaps. Virola appeared to be more gap-dependent than Moronobea which may persist several years in the understory until a gap occurs. Virola and Moronobea illustrate two intermediate recruitment patterns along an hypothetical continuum of nonpioneer species replacement (Bazzaz and Pickett 1980; Swaine and Whitmore 1988).

Acclimation to a Change in Light Regime in Seedlings of Six Australian Rainforest Tree Species

Acclimation potential of seedlings of six non-pioneer, North Queensland rainforest tree species (Diploglottis diphyllostegia, Flindersia brayleyana, Dysoxylum schgneri, Prunus turnerana, Neisosperma poweri and Castanospora alphandii) were evaluated in three different light regimes. The seedlings were grown from seeds and raised in 37, 10 and 2.5% photosynthetically active radiation (PAR) of full sunlight in a shade house. Plants were harvested at 1, 4, and 15 months after germination. At 4 months, for each species, one-third of the seedlings in each light environment were transferred to each of the two other light environments. The remaining one-third stayed in the same light environment and formed the control. The control seedlings of all species showed a marked response to increasing PAR: relative growth rate (RGR) and total biomass were low in the 2.5% PAR level, increased in the 10% PAR level and were maximal in the 37% PAR level, except for Neisosperma. The seedlings in the 25% PAR level showed a typical shade plant morphology with a high leaf area ratio, low root-shoot ratio and low specific leaf weight. For seedlings of Dysoxylum and Prunus, a change in light regime from 37% PAR to 2.5% PAR resulted in negative relative growth rates. Eleven months after transfer, many growth characteristics still showed significant initial × final light environment interactions, an indication of incomplete adjustment. Acclimation to increasing light availability was faster than acclimation to decreasing light availability. On the basis of biomass allocation patterns (root-shoot ratio, leaf area ratio and specific leaf weight), the six species could not be differentiated under the three light regimes and their dynamics. However, using RGR as a relative measure of carbon economy, it was possible to differentiate the species in their acclimation ability to decreased but not to increased irradiance. It was concluded that, for non-pioneer species, acclimation potential may be more related to physiological than to morphological plasticity.

Distribution and effects on tree growth of lianas and woody hemiepiphytes in a Costa Rican tropical wet forest

ABSTRACTWe evaluated occurrence and abundance of lianas and woody hemiepiphytes on canopy and emergent tree species in primary tropical wet forest at the La Selva Biological Station, Costa Rica. Two pioneers, Cecropia obtusifolia and C. insignis, lacked both lianas and hemiepiphytes. The seven non-pioneer species differed significantly in their loads of lianas and hemiepiphytes. For all non-pioneer species, two measures of liana and hemiepiphyte loads (the percentage of the crown occupied and the combined basal area of descending hemiepiphyte and liana roots and stems) increased significantly with tree diameter. In all non-pioneer species, most trees ∵ 70 cm diameter (50–97%) were colonized. Lianas occupied more trees and had a smaller mean host diameter than did hemiepiphytes; however, basal area of descending roots or stems was equivalent for the two life forms in occupied trees. We used partial correlations controlling for tree diameter to evaluate the relationship between annual tree diameter growth and loads of hemiepiphytes and lianas for six non-pioneer species. Five of the six species showed a significant negative correlation between loads and diameter growth. Existing published data show that the high incidence of lianas and hemiepiphytes at La Selva is paralleled in most other Neotropical wet forests.