Olusegun O. Osunkoya

Comparative height–crown allometry and mechanical design in 22 tree species of Kuala Belalong rainforest, Brunei, Borneo

In rainforests, trunk size, strength, crown position, and geometry of a tree affect light interception and the likelihood of mechanical failure. Allometric relationships of tree diameter, wood density, and crown architecture vs. height are described for a diverse range of rainforest trees in Brunei, northern Borneo. The understory species follow a geometric model in their diameter-height relationship (slope, β = 1.08), while the stress-elasticity models prevail (β = 1.27-1.61) for the midcanopy and canopy/emergent species. These relationships changed with ontogeny, especially for the understory species. Within species, the tree stability safety factor (SSF) and relative crown width decreased exponentially with increasing tree height. These trends failed to emerge in across-species comparisons and were reversed at a common (low) height. Across species, the relative crown depth decreased with maximum potential height and was indistinguishable at a common (low) height. Crown architectural traits influence SSF more than structural property of wood density. These findings emphasize the importance of applying a common reference size in comparative studies and suggest that forest trees (especially the understory group) may adapt to low light by having deeper rather than wider crowns due to an efficient distribution and geometry of their foliage.

BAAD: a biomass and allometry database for woody plants

Understanding how plants are constructed—i.e., how key size dimensions and the amount of mass invested in different tissues varies among individuals—is essential for modeling plant growth, carbon stocks, and energy fluxes in the terrestrial biosphere. Allocation patterns can differ through ontogeny, but also among coexisting species and among species adapted to different environments. While a variety of models dealing with biomass allocation exist, we lack a synthetic understanding of the underlying processes. This is partly due to the lack of suitable data sets for validating and parameterizing models. To that end, we present the Biomass And Allometry Database (BAAD) for woody plants. The BAAD contains 259u2009634 measurements collected in 176 different studies, from 21u2009084 individuals across 678 species. Most of these data come from existing publications. However, raw data were rarely made public at the time of publication. Thus, the BAAD contains data from different studies, transformed into standard units and variable names. The transformations were achieved using a common workflow for all raw data files. Other features that distinguish the BAAD are: (i) measurements were for individual plants rather than stand averages; (ii) individuals spanning a range of sizes were measured; (iii) plants from 0.01–100 m in height were included; and (iv) biomass was estimated directly, i.e., not indirectly via allometric equations (except in very large trees where biomass was estimated from detailed sub-sampling). We included both wild and artificially grown plants. The data set contains the following size metrics: total leaf area; area of stem cross-section including sapwood, heartwood, and bark; height of plant and crown base, crown area, and surface area; and the dry mass of leaf, stem, branches, sapwood, heartwood, bark, coarse roots, and fine root tissues. We also report other properties of individuals (age, leaf size, leaf mass per area, wood density, nitrogen content of leaves and wood), as well as information about the growing environment (location, light, experimental treatment, vegetation type) where available. It is our hope that making these data available will improve our ability to understand plant growth, ecosystem dynamics, and carbon cycling in the worlds vegetation.

Lantana camara L. (Verbenaceae) invasion effects on soil physicochemical properties

Lantana camara is a recognized weed of worldwide significance due to its extensive distribution and its impacts on primary industries and nature conservation. However, quantitative data on the impact of the weed on soil ecosystem properties are scanty, especially in SE Australia, despite the pervasive presence of the weed along its coastal and inland regions. Consequently, mineral soils for physicochemical analyses were collected beneath and away from L. camara infestations in four sites west of Brisbane, SE Australia. These sites (hoop pine plantation, cattle farm, and two eucalyptus forests with occasional grazing and a fire regime, respectively) vary in landscape and land-use types. Significant site effect was more frequently observed than effect due to invasion status. Nonetheless, after controlling for site differences, ~50% of the 23 soil traits examined differed significantly between infested and non-infested soils. Moisture, pH, Ca, total and organic C, and total N (but not exchangeable N in form of NO3-) were significantly elevated, while sodium, chloride, copper, iron, sulfur, and manganese, many of which can be toxic to plant growth if present in excess levels, were present at lower levels in soils supporting L. camara compared to soils lacking the weed. These results indicate that L. camara can improve soil fertility and influence nutrient cycling, making the substratum ideal for its own growth and might explain the ability of the weed to outcompete other species, especially native ones.

Longevity, Lignin Content and Construction Cost of the Assimilatory Organs of Nepenthes Species

BACKGROUND AND AIMSnThis study examined level of causal relationships amongst functional traits in leaves and conjoint pitcher cups of the carnivorous Nepenthes species.nnnMETHODSnPhysico-chemical properties, especially lignin content, construction costs, and longevity of the assimilatory organs (leaf and pitcher) of a guild of lowland Nepenthes species inhabiting heath and/or peat swamp forests of Brunei, northern Borneo were determined.nnnKEY RESULTSnLongevity of these assimilatory organs was linked significantly to construction cost, lignin content and structural trait of tissue density, but these effects are non-additive. Nitrogen and phosphorus contents (indicators of Rubisco and other photosynthetic proteins), were poor predictors of organ longevity and construction cost, suggesting that a substantial allocation of biomass of the assimilatory organs in Nepenthes is to structural material optimized for prey capture, rigidity and escape from biotic and abiotic stresses rather than to light interception. Leaf payback time - a measure of net carbon revenue - was estimated to be 48-60 d. This is in line with the onset of substantial mortality by 2-3 months of tagged leaves in many of the Nepenthes species examined. However, this is a high ratio (i.e. a longer minimum payback time) compared with what is known for terrestrial, non-carnivorous plants in general (5-30 d).nnnCONCLUSIONSnIt is concluded that the leaf trait bivariate relationships within the Nepenthes genus, as in other carnivorous species (e.g. Sarraceniaceae), is substantially different from the global relationship documented in the Global Plant Trait Network.

Reproductive and ecophysiological attributes of the rare Gardenia actinocarpa (Rubiaceae) compared with its common co-occurring congener, G. ovularis

Gardenia actinocarpa Puttock (rare) and G. ovularis F.M.Bailey (widespread) are closely related co-occurring shrub–small trees of rainforests of far north Queensland, Australia.Gardenia actinocarpa is endemic to alluvial lowlands along Noah–Oliver Creeks of Cape Tribulation, whereasG. ovularis spans a wider habitat and occurs on a range of substrates and altitudes. The rare G. actinocarpa is cryptically and strictly dioecious, with a longer reproductive period (9 months) and a low fecundity (1.77 fruits per female tree). In contrast, G. ovularis, although also dioecious, has a shorter reproductive phase (4 months) and produces more fruits (35.76 fruits per female tree), some of which may occur in the absence of fertilisation (apomixis). Under different regimes of photosynthetically active radiation (PAR), seed germination percentages and patterns were similar (70–90%) in the two species, although at 37% PAR G. actinocarpa has lower germination (55–68%). The rare G. actinocarpa loses seed viability very rapidly (G. ovularis (37%). Gardenia actinocarpa grows and survives in both closed forest understorey and in small gaps, while G. ovularis prefers light gaps (both small and large). Net photosynthetic measurements of seedlings grown at 2.5 and 37% PAR suggest that the physiological performance of G. actinocarpa is not inferior to that of G. ovularis, although the latter exhibits greater plasticity. In a density-dependent seedling growth experiment, G. actinocarpa, surprisingly, has a superior competitive ability. Thus, the rarity ofG. actinocarpa may be a result of limited fecundity, reduced seed dispersal ability and lack of soil seed-banks rather than inferior vegetative and ecophysiological traits.

What lies beneath? The pattern and abundance of the subterranean tuber bank of the invasive liana cat's claw creeper, Macfadyena unguis-cati (Bignoniaceae)

Cat’s claw creeper, Macfadyena unguis-cati (L.) Gentry (Bignoniaceae) is a major environmental weed of riparian areas, rainforest communities and remnant natural vegetation in coastal Queensland and New South Wales, Australia. In densely infested areas, it smothers standing vegetation, including large trees, and causes canopy collapse. Quantitative data on the ecology of this invasive vine are generally lacking. The present study examines the underground tuber traits of M. unguis-cati and explores their links with aboveground parameters at five infested sites spanning both riparian and inland vegetation. Tubers were abundant in terms of density (~1000 per m2), although small in size and low in level of interconnectivity. M. unguis-cati also exhibits multiple stems per plant. Of all traits screened, the link between stand (stem density) and tuber density was the most significant and yielded a promising bivariate relationship for the purposes of estimation, prediction and management of what lies beneath the soil surface of a given M. unguis-cati infestation site. The study also suggests that new recruitment is primarily from seeds, not from vegetative propagation as previously thought. The results highlight the need for future biological-control efforts to focus on introducing specialist seed- and pod-feeding insects to reduce seed-output.

Stand dynamics and spatial patterns across varying sites in the invasive Lantana camara L. (Verbenaceae)

As with many invasive plant species, little is known of the population spatial patterns and stand dynamics of Lantana camara L. (Verbenaceae)—a thicket-forming weed of worldwide significance in managed and conservation lands, including coastal and inland habitats of Eastern Australia. Consequently, we mapped and followed annually for 3xa0years the demographic fate of more than 2000 Lantana individuals at sites with four land-uses (hoop pine plantation, cattle farm, and two eucalyptus forests with occasional grazing and periodic burning regime, respectively) in Queensland, SE Australia. Populations exhibited plant size distributions that were continuous (i.e., of L or symmetric type) and unimodal, except the farm population where bimodality was observed. Newly established plants could be reproductive within one growing season at ~50xa0cm in height, especially where environmental resources were not limiting. Density had an appreciable effect on the weed’s reproductive capacity and growth, but not on survival. Established and newly recruited individuals were aggregated but the degree of aggregation decreased with plant size. However, in the sites that had experienced burning or mechanical clearing, Lantana seedling/juvenile recruitment assumed negative association (spatial displacement) in relation to established individuals. The findings of this study agree with the notion that ecological processes often leave characteristic spatial signatures, which if interpreted using appropriate hypotheses can help to ascertain factors responsible for the observed spatial patterns and stand dynamics.

Modeling population growth and site specific control of the invasive Lantana camara L. (Verbenaceae) under differing fire regimes.

It is at the population level that an invasion either fails or succeeds. Lantana camara L. (Verbenaceae) is a weed of great significance in Queensland Australia and globally but its whole life-history ecology is poorly known. Here we used 3xa0years of field data across four land use types (farm, hoop pine plantation and two open eucalyptus forests, including one with a triennial fire regime) to parameterise the weed’s vital rates and develop size-structured matrix models. Lantanacamara in its re-colonization phase, as observed in the recently cleared hoop pine plantation, was projected to increase more rapidly (annual growth rate, λxa0=xa03.80) than at the other three sites (λ 1.88–2.71). Elasticity analyses indicated that growth contributed more (64.6xa0%) to λ than fecundity (18.5xa0%) or survival (15.5xa0%), while across size groups, the contribution was of the order: juvenile (19–27xa0%)xa0≥xa0seed (17–28xa0%)xa0≥xa0seedling (16–25xa0%)xa0>xa0small adult (4–26xa0%)xa0≥xa0medium adult (7–20xa0%)xa0>xa0large adult (0–20xa0%). From a control perspective it is difficult to determine a single weak point in the life cycle of lantana that might be exploited to reduce growth below a sustaining rate. The triennial fire regime applied did not alter the population elasticity structure nor resulted in local control of the weed. However, simulations showed that, except for the farm population, periodic burning could work within 4–10xa0years for control of the weed, but fire frequency should increase to at least once every 2xa0years. For the farm, site-specific control may be achieved by 15xa0years if the biennial fire frequency is tempered with increased burning intensity.

Leaf properties and construction costs of common, co-occurring plant species of disturbed heath forest in Borneo

The leaf properties and construction costs (CC) are reported for eight indigenous heath (kerangas) forest species and three invasive (exotic) species of Acacia. Both groups of species co-occur and colonise disturbed lowland tropical heath rainforest habitats in Brunei, Borneo Island. Across species, CC mass-based increased with nitrogen (N) and heat of combustion (H C ), and decreased with ash content. CC area-based showed similar trends (although weaker in strength) in addition to significant positive correlation with leaf mass per unit area (LMA). Within the native species, the CCs of the shrub and small tree species were lower and significantly different from those of medium-sized tree species. Given the invasive success of the three acacias, it is hypothesised that these species may require less energy for biomass construction than do the native species. Within similar life growth form, no difference in CC mass-based was detected between the native trees and the invasive acacias. For CC area-based, the invasive Acacia species had a higher value. These findings failed to uphold our hypothesis. LMA and leaf N and phosphorus (P), but not potassium (K), were higher in the invasive acacias. The higher N and LMA could have been the cause of higher CC area-based in the invasive acacias. From the ordination of 11 species on the basis of leaf properties, the invasive and native species are more likely to be found in different groupings—although some native species seem more affiliated with the invasive than with their own guild, especially Alphitonia and Macaranga. BT04 Lea io iv ic e O. O. Os et al

Cat's claw creeper vine, Macfadyena unguis-cati (Bignoniaceae), invasion impacts: comparative leaf nutrient content and effects on soil physicochemical properties

Macfadyena unguis-cati (L.) Gentry (Bignoniaceae) is a major environmental weed in coastal Queensland, Australia. There is a lack of quantitative data on its leaf chemistry and its impact on soil properties. Soils from infested vs uninfested areas, and leaves of M. unguis-cati and three co-occurring vine species (one exotic, two native) were collected at six sites (riparian and non-riparian) in south-eastern Queensland. Effects of invasion status, species, site and habitat type were examined using univariate and multivariate analyses. Habitat type had a greater effect on soil nutrients than on leaf chemistry. Invasion effect of M. unguis-cati on soil chemistry was more pronounced in non-riparian than in riparian habitat. Significantly higher values were obtained in M. unguis-cati infested (vs. uninfested) soils for ~50% of traits. Leaf ion concentrations differed significantly between exotic and native vines. Observed higher leaf-nutrient load (especially nitrogen, phosphorus and potassium) in exotic plants aligns with the preference of invasive plant species for disturbed habitats with higher nutrient input. Higher load of trace elements (aluminium, boron, cadmium and iron) in its leaves suggests that cycling of heavy-metal ions, many of which are potentially toxic at excess level, could be accelerated in soils of M. unguis-cati-invaded landscape. Although inferences from the present study are based on correlative data, the consistency of the patterns across many sites suggests that M. unguis-cati may improve soil fertility and influence nutrient cycling, perhaps through legacy effects of its own litter input.