In 2000, we established a 24-ha plot in Peninsular Thailand to investigate how forest composition, structure and dynamics vary with spatial heterogeneity in resource availability. Detailed soil and topographic surveys were used to describe four edaphic habitats in the plot. Disturbance history was inferred from historical records and floristic analysis. The plot included >119 000 trees ≥1 cm dbh in 578 species, and was recensused in 2010. Species distributions, floristic turnover, stand structure, demographic rates and biomass dynamics were strongly influenced by heterogeneity in soils, topography and disturbance history. Over 75% of species were aggregated on specific edaphic habitats leading to strong compositional turnover across the plot. Soil chemistry more strongly affected species turnover than topography. Forest with high biomass and slow dynamics occurred on well-drained, low fertility ridges. The distribution and size structure of pioneer species reflected habitat-specific differences in disturbance history. Overall, above-ground biomass (AGB) increased by 0.64 Mg ha−1 y−1, from 385 to 392 Mg ha−1, an increase that was entirely attributable to recovery after natural disturbance. Forest composition and stand structure, by reflecting local disturbance history, provide insights into the likely drivers of AGB change in forests. Predicting future changes in tropical forests requires improved understanding of how soils and disturbance regulate forest dynamics.

Rooting differentiation between established trees and grasses has been well documented in savannas, but it remains unclear to what extent tree-grass rooting differences affect competition between newly established seedlings and grasses. To examine this question, a greenhouse experiment was conducted at the University of Missouri, USA. Twenty 3-mo-old seedlings each of two African savanna tree species (Acacia nigrescens and Colophospermum mopane) were grown for 8 mo with two crossed factors: grass competition and irrigation depth. Strong negative effects of grass competition on final seedling biomass and leaf photosynthetic and stomatal conductance occurred in both tree species, but no effects of irrigation depth were detected. There was a clear tree species by grass competition interaction, suggesting interspecific variation in competitive response. The results emphasize the importance of below-ground competition with grasses for physiological and morphological responses of tree seedlings, while minimizing the importance of tree-grass rooting depth differences as a factor in modulating the competitive response of trees to grasses at the seedling stage.

Third-year heights, third-year root-collar diameters, and 3 yr volume growth of loblolly pine seedlings were examined in relation to a) root-collar diameter class at time of planting and b) herbaceous weed control. Treatments were a) no weed control and b) complete control for 2 yr. For both weed control treatments, means for third-year heights, groundline diameters, and volume growth were related positively to initial seedling diameter. The influence of initial seedling diameter on third-year diameters and heights did not differ among weed control treatments. However, the influence of initial diameter on volume growth did differ among weed control treatments. Thus, when using herbaceous weed control, additional gains in early volume growth can be realized by planting seedlings with large root-collar diameters.

Nutrient subsidies from one ecosystem to another serve a critical link among ecosystems. The transfer of materials across the terrestrial-to-marine boundary is considered to be driven by hydrological connectivity, but animal movement can provide another pathway for nutrient transfers. In two separate studies we assessed the role mammals (bats and kangaroos) play in alleviating nutrient limitation in mangrove forests in Australia. At Lizard Island, we measured tree growth and foliar elemental and isotopic composition of trees growing within and outside a large flying fox roost. In Western Australia, we measured foliar elemental and isotopic composition of trees within two forests frequented by kangaroos that feed in spinifex grasslands and shelter in the shade of the mangroves. We compared those with mangroves from adjacent forests that are not frequented by kangaroos. We show that at both locations, the mangrove forest receives terrestrial nutrient subsidies through animal movement. At Lizard Island dominant mangrove species were significantly enriched in nitrogen within the bat roost, as evidenced by higher foliar N concentrations (by up to 150%), N:P and N:C ratios in trees within the roost compared with trees outside the roost. The isotopic signature of foliar N was significantly enriched in 15N by 1–3‰ within the roost, further suggesting that the source of the N enrichment was the bat roost. Growth rates of mangroves within the roost were nearly six times higher than trees outside the roost. In the arid coast of Western Australia, we show elevated foliar 15N abundance of up to 3‰ in mangroves where kangaroos shelter relative to trees where they do not. Thus, this study presents two examples for mammalian herbivore mediated localized transport of nutrients from terrestrial to marine ecosystems, consequently affecting mangrove tree growth, productivity and forest structure.

Mbau forest covers much of the Congo, and shifts in its composition could have a large impact on the African tropics. The Ituri forest in east Congo is near a boundary between the monodominant mbau type and non-mbau mixed forest, and two 20-ha censuses of trees ≥ 1 cm diameter were carried out over 12 y to monitor forest change. Based on published diameter allometry, mbau forest had 535 Mg ha−1 biomass above ground and gained 1.1 Mg ha−1 y−1. Mixed forest had 399 Mg ha−1 and gained 3 Mg ha−1 y−1. The mbau tree (Gilbertiodendron dewevrei) increased its share of biomass from 4.1% to 4.4% in mixed forest; other common species also increased. Sapling density declined at both sites, likely because increased biomass meant shadier understorey, but the mbau tree increased in sapling density, suggesting it will become more important in the future. Tree mortality and growth rates were low relative to other tropical forests, especially in the mbau plots. Shifting toward G. dewevrei would represent a large gain in carbon in the mixed forest, but mbau is presently more important as a high-carbon stock: biomass lost during forest harvest could not recuperate for centuries due to slow community dynamics.

Inability to age tropical trees has imposed major limitations on the basic and applied science of tropical forests. Here advantage was taken of even-aged stands present in successional chronosequences found on Amazonian Whitewater river meanders to simplify the assumptions needed to estimate tree ages from growth measurements. Growth increments of eight common early successional species were measured in 21 0.5-ha plots evenly distributed over chronosequences from the earliest post-pioneer stage to mature Ficus-Cedrela stands representing approximately the mid-point of primary succession. Increment measurements, based on 4 or 5 y of growth, were arrayed in scatter diagrams against the midpoints of the growth intervals. A loess regression of the points, weighted for the higher mortality of slow-growing individuals, was then conducted to generate a ‘best estimate lifetime growth trajectory’ (BELGT) of a ‘typical’ individual surviving to maturity. The BELGT curves were integrated to generate a set of derived curves describing the time required by a ‘typical’ surviving individual to attain any given size up to the maximum for the species. Predictions of the ages of particular stands were derived from these latter curves and found to agree within 3 to 20% of ages independently estimated from the rate of point bar accretion.

We 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.

Published work on the dynamics of forest tree recruitment, growth and mortality in natural tropical forest is reviewed. In most forests studied, annual mortality is between 1% and 2% and is independent of size class in trees >10 cm dbh; mortality is negatively correlated with growth rate and crown illumination; growth rate is highly variable between individual trees, but shows strong autocorrelation between successive measurements on the same tree.

Differences in the rate of dynamic processes can be detected between some species at a site, but data are presently insufficient to determine whether these differences are preserved at other sites where the species occur. None of the studies discussed are of sufficient duration to permit us to draw any conclusions about the equilibrium or non-equilibrium of floristic composition.

Changes in the lowland dipterocarp forest structure and composition are described for a 34-year period between 1947 and 1981 in Sungei Menyala Forest Reserve, Peninsular Malaysia. Although tree density declined by about 10%, basal area changed little, averaging 32.4 m2 ha−1. Size class distributions in 1947 and 1981 were not significantly different. Mortality rates were independent of size class. Mortality exceeded recruitment during the first 16 years to 1963, but was thereafter almost exactly balanced by recruitment. Recruitment rate increased significantly for the latter part of the study.

Mortality was greater than average for understorey species and lower for emergents. Pioneer and late seral species together showed significantly higher mortality rates. Amongst the commoner species, emergent, late-seral and pioneer species showed the highest annual diameter growth rates with species averages over all size classes exceeding 3 mm yr−1; rates for main-canopy species were between 1.5 and 2.5 mm yr−1, and understorey species generally less than 2 mm yr−1.

Species richness was almost identical in 1947 and 1981 (243, 244 species), but a clear decline (to 229 species) between 1953 and 1971 was recovered by 1981. Most species showed little net change in density over the 34-year period, but eight of the 32 commoner species showed significant changes, all unidirectional. These changes in species composition are not negligible, but further analysis is needed to determine if, for example, they are related to disturbance of part of the plot in 1917.

Long-term growth rates of 32 palms (Prestoea montana) were studied using height and diameter measurements taken four times between 1946 and 1982. All leaf scars were counted to estimate leaf production rate, and the distance between scars was measured to establish relationships between leaf production and height growth. Height and diameter growth and leaf production of these palms were not constant during this 36-year period. A greater distance between leaf scars was indicative of rapid height growth but not of high leaf production rate. Dominant palms always grew fast (> 20 cm/yr) in height when they were small, but height growth slowed down when they reached the canopy. Small palms with slow height growth remained suppressed and lost the capacity to grow rapidly in height as adults. Diameter growth decreased with age from 0.07 cm/yr (SE = 0.02) between 1946–51 to 0.01 cm/yr (SE = 0.003) between 1951–82. Annual leaf production averaged 4 leaves/yr over the 36 years of study, was significantly different (P = 0.001) between 1946–51 (5.6 leaves/yr) and 1951–82 (3.8 leaves/yr), and was 4.6 leaves/yr for palms that grew >5 m since 1946 and 3.7 leaves/yr for those that remained suppressed. The best estimate for the mean age of all palms was 61.1 yr (SE = 2.4), obtained from long-term population leaf production rates.

Most trees in the eucalypt savannas of Australia have hollow cores, or pipes, caused by termite activity, yet little is known about their effect on tree growth or survival. Five hundred and forty-one trees with known growth and survival histories were cored to determine pipe diameters in wooded savanna of Kakadu National Park, north Australia. Generalized linear modelling and multi-model inference was used to analyse frequency and degree of piping relative to initial tree diameter at breast height (dbh), eco-taxonomic group or species of eucalypt. Growth (dbh increment) and survival (4 y) were analysed relative to initial tree size, pipe ratio (pipe diameter:dbh) and eco-taxonomic group. The frequency of piping was strongly dependent on dbh, increasing with size of tree, and was highest in eucalypts. Growth and survival of eucalypts increased with tree diameter and decreased with pipe ratio. For example, from modelled data, 10-cm-diameter trees without pipes grew 0.14 cm y−1 with 85% survival vs. 10-cm trees with pipe ratios of 0.60 which had near-zero growth and only 46% survival. Comparing 40-cm-diameter trees without pipes to those having pipe ratios of 0.80, growth was 0.22 vs. 0.05 cm y−1, with little difference in survival, 97–99%, respectively. Contrary to the suggestion that tree hollows are an adaptive trait whereby trees benefit by the release of nutrients, in the north Australian eucalypt savannas the net effect of termite piping on individual tree growth and survival was negative.

Occasional strong droughts are an important feature of the climatic environment of tropical rain forest in much of Borneo. This paper compares the response of a lowland dipterocarp forest at Danum, Sabah, in a period of low (LDI) and a period of high (HDI) drought intensity (1986–96, 9.98 y; 1996–99, 2.62 y). Mean annual drought intensity was two-fold higher in the HDI than LDI period (1997 v. 976 mm), and each period had one moderately strong main drought (viz. 1992, 1998). Mortality of ‘all’ trees ≥10 cm gbh (girth at breast height) and stem growth rates of ‘small’ trees 10–<50 cm gbh were measured in sixteen 0.16-ha subplots (half on ridge, half on lower slope sites) within two 4-ha plots. These 10–50-cm trees were composed largely of true understorey species. A new procedure was developed to correct for the effect of differences in length of census interval when comparing tree mortality rates. Mortality rates of small trees declined slightly but not significantly between the LDI and HDI periods (1.53 to 1.48% y−1): mortality of all trees showed a similar pattern. Relative growth rates declined significantly by 23% from LDI to HDI periods (11.1 to 8.6 mm m−1 y−1): for absolute growth rates the decrease was 28% (2.45 to 1.77 mm y−1). Neither mortality nor growth rates were significantly influenced by topography. For small trees, across subplots, absolute growth rate was positively correlated in the LDI period, but negatively correlated in the HDI period, with mortality rate. There was no consistent pattern in the responses among the 19 most abundant species (n≥50 trees) which included a proposed drought-tolerant guild. In terms of tree survival, the forest at Danum was resistant to increasing drought intensity, but showed decreased stem growth attributable to increasing water stress.

In temperate trees, the extension growth history of stems and branches is easily inferred from the positions of the rings of over-wintering bud-scale scars, allowing one to assess environmental responses from surveys of saplings (Beaudet & Messier 1998, Canham 1988, King 2001). But tropical trees rarely show such distinct demarcations of growth flushes. Furthermore, the frequency of flushing may vary with tree size and environment, and a number of tropical species, often light demanding, show continuous leaf production and extension growth throughout the year (Coley 1983).

Relating patterns of species abundance to the processes that determine them at local and regional spatial scales is one of the central aims of ecological research. To examine the relationship between distribution and growth in tropical rain forest, seasonal and annual changes in tree diameter of two tree species with contrasting distribution patterns, Celtis mildbraedii and Strombosia glaucescens, were monitored across topographic gradients in moist semi-deciduous and moist evergreen forest in Ghana over 2 years, 1997-9. Concurrent measurements were made of soil water availability, and during 1997/8, of rainfall, nutrient availability and photosynthetically active radiation (PAR). The two sites received similar, low, total rainfall during 1997/8, but soil water availability in the dry season at the evergreen site exceeded that at the semi-deciduous forest site. Soil water availability was higher during 1998/9 at both sites. During 1997/8, PAR was similar at the two sites. The evergreen site had soils of lower pH, available P, Mg, Ca and K concentrations than the semi-deciduous forest site. Water availability and the sand content of the soil increased and concentrations of total N and C decreased, from summit to valley positions at both sites. Celtis mildbraedii had significantly faster growth rates than S. glaucescens, and growth of both species was greater at the semi-deciduous than the evergreen forest site during the wet year (1998/9) but not during the dry year (1997/8). Celtis mildbraedii in semi-deciduous forest grew less in valley than summit and slope positions. We conclude that in the absence of a severe dry season, growth is higher in semi-deciduous than evergreen forest, and is related to the higher soil fertility in more seasonal forest. The patterns are consistent with the hypothesis that concentrations of available P and/or cations in the soil limit growth in evergreen forest, while concentrations of N in valley soils limit growth of C. mildbraedii in semi-deciduous forest. There was no evidence that variation in PAR influenced growth rates in these forests. A reduction in growth rate on less fertile soils may be a factor determining the distribution limit of dry forest species, such as C. mildbraedii, in evergreen forest.

Seedlings of Quercus petraea (oak), Fraxinus excelsior (ash) and Pinus sylvestris (Scots pine) were grown at two CO2 concentrations with two O3 and two water supply treatments for 3 yr in a factorial experiment. Oak was the most responsive species to all three treatments; elevated CO2 and irrigation increased biomass by an average of 79% and 41%, respectively, whereas the ozone treatment resulted in a 30% reduction in growth. Significant treatment interactions in this species demonstrated that CO2 ameliorated and irrigation exacerbated the effects of ozone. For Scots pine and ash, irrigation and elevated CO2 increased growth by approx. 60% and 20%, respectively, whereas ozone had no detectable effect on ash and resulted in a 15% reduction in growth of Scots pine. Carbon partitioning to the shoot was enhanced by both the CO2 and H2O treatments in oak, while branching was also increased in this species in response to elevated O3, resulting in changes to the allometric relationships. CO2 enhanced leaf production in oak and Scots pine, and together with the promotion of shoot allocation, this indicates an increased susceptibility to windthrow. Biomass accumulation expressed as relative growth rate, suggested three different time-dependent growth responses to elevated CO2; the CO2 fertilization effect was maintained through the third year of growth in oak, had disappeared in Scots pine and a negative effect was evident in ash. Foliar nitrogen and chlorophyll concentrations indicated a CO2-induced nitrogen deficiency in oak and ash, but not in Scots pine. Chlorophyll degradation in response to ozone was observed in oak, an effect that was enhanced by irrigation and reduced by CO2, presumably through stomatal mediated changes in effective ozone dose. These results therefore suggest that elevated atmospheric CO2 concentrations will enhance growth of some UK forest tree species, although this might only be apparent during the juvenile phase. However, nitrogen deficiencies might limit this enhancement on some sites while changes in allocation and leaf area might promote susceptibility to windthrow. Elevated CO2 also provides some protection against ozone pollution, especially in combination with limited soil moisture availability. These interactions between CO2, ozone and water supply should be taken into account when predicting the effects of environmental change on tree growth and forest productivity.

Current estimates of forest yield losses attributable to ozone pollution amount to c. 10% over Europe as a whole. This figure is derived from a synthesis of all European studies using trees for which AOT40 exposure values are available. However, the choice of 40 nl l−1 as the threshold concentration for demonstrable effects has led to debate, and this value might not be low enough to predict ozone effects in Scandinavia, where concentrations are lower than in southern Europe, and chronic injury resulting from cumulative exposure is observed. This ‘level I’ approach provides a useful means for mapping physiologically effective concentrations but has significant shortcomings in that it is unable to take environmental conditions into account. In order to produce a mechanism capable of predicting yield losses resulting from ozone pollution at specific sites and for individual species, the effective ozone dose, a product of conductance and concentration, must be calculated. Process-based models relating the environment (temperature, humidity/saturation deficit, incident light and soil moisture content) to conductance are available for a number of species (oak, Scots pine, Norway spruce, Sitka spruce, beech and poplar). Effective ozone doses could therefore be calculated, and the relationships between effective dose and yield loss could be determined by revisiting existing data for which only concentrations or AOT40 values are available at present. Yield loss must be the growth parameter with which ozone damage is expressed, since visible injury does not necessarily represent severe injury to the plant, whilst visibly unaffected plants may be significantly compromised in terms of biomass accumulation. For conifers, premature needle drop, although indicative of ozone pollution, might not represent a significant reduction in growth since older needles are, functionally, relatively unimportant.

When revisiting old experiments the question should also be asked ‘what is an appropriate control treatment’. It is unrealistic to expect ambient O3 concentrations on a global scale to return to pre-industrialization levels, and therefore the use of a charcoal-filtered treatment is probably unrealistic. In addition, charcoal filters will remove some of the NOx, and therefore on nutrient deficient soils (typical of many forest soils) the ‘control’ treatment might represent a reduced supply of nitrogen, making it difficult to disentangle the ozone effect per se.

The stage has therefore been reached where ‘level II’ ozone exposure mapping (i.e. based on effective dose at the physiological level) is possible for a number of species. As financial considerations become increasingly important, the scientific community must aim to provide better estimates of O3-induced yield losses so that long-term environmental audits can be performed.

We compared conventional and alternative systems for the establishment of apple trees on a replicated, whole-orchard scale. The alternative system consisted of a K-31 fescue sod rotation followed by planting of trees directly into sod that had been kitted with herbicide. The conventional system consisted of a standard corn rotation, accompanied by application of fertilizer and nematicide. Orchard floor management in the three years following tree planting was based on the use of both pre-and post-emergence herbicides in the conventional system and only contact herbicide in the alternative system. The study documented tree growth, pest incidence, and nitrate mobility in the two systems. The alternative system compared favorably with the conventional system for the growth and establishment of four apple cultivars. Many advantages accompanied the killed sod system, including less subsurface leaching ofnitrate-N and lower costs (largely from decreased herbicide use). The alternative system provided an economical alternative to the problem of soil organic matter depletion in conventional orchard soils without requiring increased use of commercial fertilizers. Grower concerns regarding increased potential for vole damage and poor initial tree growth were unsubstantiated.