Elevational parallels of latitudinal variation in the proportion of lianas in woody floras

Aim  To determine if elevational variation in the proportion of lianas in woody floras parallels the variation observed on latitudinal gradients. This is to be expected if the poleward decrease in the importance of lianas is related to the vulnerability of their wide vessels to freeze embolism.
Location  Coastal ranges of south-central Chile (latitude 37°–40° S) and western South Island of New Zealand (41°–43° S).
Methods  The presence of all woody species was recorded in plots of 2500 m² (Chile) or 100–400 m² (New Zealand) on four elevational gradients in temperate rain forest. Each species was classified as a tree, shrub or liana. Original data were obtained from 22 plots at two sites in Chile. In New Zealand, two surveys comprising a total of 296 plots were extracted from the National Vegetation Survey data base.
Results  Liana species richness declined more or less monotonically on all four gradients, whereas richness of trees and shrubs showed more varied elevational patterns. The proportion of woody species contributed by the liana life-form was negatively correlated with elevation on all four gradients, falling from 15 to 35% of the woody flora at c . 200 m a.s.l. to nil well below the tree line. The elevational and latitudinal limits of liana species were marginally significantly correlated in Chile, but not in New Zealand.
Main conclusions  The elevational parallel of the well-documented decline in liana representation with increasing latitude is consistent with the hypothesis that cold intolerance is a strong control on the global distribution of the liana life-form.     

Canopy openness in gaps determines the influence of herbaceous climbers and insect folivory on the survival of a tropical pioneer tree,Neoboutonia macrocalyx Pax

Gaps created 10 years ago by clearing of conifer plantations in Kibale National Park, Uganda, still experience very little tree regeneration. We studied the arrested succession by examining the survival of Neoboutonia macrocalyx Pax in different sized canopy gaps. We examined whether Neoboutonia seedlings can survive in gaps, which the tree rarely colonizes naturally and whether survival is limited by the size of the canopy opening, herbaceous climbers or insect folivory. A total of 384 seedlings were planted in 24 gaps, and survival was monitored for 19 months. Survival was dependent on canopy openness, being lowest in small gaps and highest in large gaps. We found a significant negative relationship between survival and folivory and a positive relationship between survival and climber infestation. Because 53% of the seedlings survived, regeneration could be limited by seed dispersal, rather than high seedling mortality. However, considering its high survival rate in arrested succession gaps, Neoboutonia seems to have good potential for forest restoration.     

Spatially limited clonality and pollen and seed dispersal in a characteristic climber of Central African rain forests: Haumania danckelmaniana (Marantaceae)

Gene dispersal and clonality are important aspects of plant evolution affecting the spatial genetic structure (SGS) and the long‐term survival of species. In the tropics these parameters have mostly been investigated in trees and some herbs, but rarely in climbers which frequently: (1) show clonal growth leading to a patchy distribution pattern similar to that of understory herbs; and (2) flower in the canopy where they may have access to long‐distance dispersal like canopy trees. We thus hypothesize for climbers an intermediate genetic structure between herbs and trees. The study aims at assessing breeding system and spatial extent of clonality and gene dispersal in Haumania danckelmaniana (Marantaceae), a common climber in the tropical rain forests from western Central Africa. In eastern Cameroon, 330 ramets were sampled at three spatial scales and genotyped at seven microsatellite loci. Clonality was moderate (clonal extend: 15–25 m, clonal diversity 0.4–0.65) indicating the importance of recruitment from seeds at this locality. The low inbreeding (F_IS) suggested predominant outcrossing. The rate of decay of the relatedness between individuals with distance indicated limited gene dispersal distance (σ_g = 9–50 m, neighborhood sizes Nb = 23–67) in accordance with narrowly gravity dispersed seeds and restricted pollen transfer distance in densely flowering populations. The marked SGS (Sp = 0.011–0.026) was similar to that reported in tropical trees, but might increase with augmented clonality as in many herbs, especially under more severe disturbance regimes.     

Comparison Between Two Methods for Measuring Fruit Production in a Tropical Forest1

We compared fruiting data derived simultaneously from fruit traps placed on the ground and from canopy‐surveyed plots in a terra firme rain forest, Colombian Amazonia. Values derived from the canopy‐surveyed plots were higher than fruit‐trap estimates. Fruiting patterns obtained throughout both methods were not correlated. Our results showed that the fruit‐trap method does not accurately reflect fruiting patterns occurring at the highest levels of the forest, while the canopy‐surveyed plots provided both quantitative and qualitative information on canopy fruit production, and each species contribution.     

Seedling growth of climbing species from a southeast Brazilian tropical forest

Climbers are considered heliophytes. They are copious at the margins of forests and natural and man-made clearings. The objective of this paper was to study the initial growth of seedlings maintained under full sunlight and shaded conditions (under a vegetation canopy). The species studied were: Aristolochia galeata, Arrabidea triplinervia, Bidens brasiliensis, Canavalia parviflora, Chamissoa altissima, Cissus sicyoides, Dalechampia pentaphylla, Dicella bracteosa, Dioscorea sp., Gouania virgata, Mascagnia anisopetala, Mutisia coccinea, Oxypetalum molle, Pithecoctenium crucigerum, Rynchosia phaseoloides, Serjania multiflora and Solanum flaccidum. The initial growth of the seedlings was followed under two conditions: at the margin and under the canopy of a mesophyllous tropical forest (22° 4955S–47° 0633W). The climbers showed high rates of growth in sunlight when compared to those under canopy. Most of the species presented higher growth of the shoot than roots but in general no significative differences between root/shoot were found in both treatments. Bidens, Cissus, Mutisia and Pithecoctenium showed a very high mortality rate under canopy but, most of the studied species survived under deep shaded forest for approximately 100 days.     

Abundance and utilization of Pyrenacantha sylvestris in Budongo Forest Reserve,western Uganda

Pyrenacantha sylvestris S. Moore (Icacinaceae), locally known as Kateganende, has been extensively harvested by local people yet poorly managed. This has created a gap between its utilization and conservation. A study was therefore conducted to document its abundance and utilization in Budongo Forest Reserve. Abundance was assessed in ten systematically sampled plots of 20 × 50 m. Five of the plots were established in logged forest (compartment N2) and the other five in the nature reserve (compartment N15). Individual P. sylvestris and trellises were recorded and their respective diameter at breast height measured. Questionnaires designed to capture information on the utilization of P. sylvestris were administered to 40 systematically selected respondents adjacent to the forest reserve. Abundance was highest in logged areas of the forest (χ² = 14.8, d.f. = 4, P < 0.01). Individuals in the diameter class 0.1–0.5 cm were the most abundant. Pyrenacantha sylvestris in the forest were mostly hosted in the trellises of the diameter class 1.0–10 cm. Over‐reliance and use of P. sylvestris threaten the survival of the species. There is a need to create awareness and regulate its harvesting. In addition, research needs to be conducted on the possibility of propagating and domesticating this plant.