Showing papers in "Plant Ecology & Diversity in 2014"

Vertical distance from drainage drives floristic composition changes in an Amazonian rainforest

Abstract: Background: Plant composition changes with topography and edaphic gradients that correlate with soil-water and nutrient availability. Data on soil water for the Amazon Basin are scarce, limiting the possibility of distinguishing between soil and soil-water influences on plant composition. Aim: We tested a new proxy for water table depth, the terrain height above nearest drainage (HAND), as a predictor of composition in trees, lianas, palms, shrubs, and herbs and compared HAND to conventional measures of height above sea level (HASL) and horizontal distances from nearest drainage (HDND). Methods: Plant-species composition in 72 plots distributed across 64 km2 of lowland evergreen terra firme forest was summarised using non-metric multidimensional scaling (NMDS). NMDS scores were regressed against estimates of HAND, HASL and HDND. Results: Plant composition was highly correlated with the vertical distance from water table, capturing up to 82% of variation. All life forms showed highest turnover rates in the...

The productivity, metabolism and carbon cycle of two lowland tropical forest plots in south-western Amazonia, Peru

Abstract: Background: The forests of western Amazonia are known to be more dynamic that the better-studied forests of eastern Amazonia, but there has been no comprehensive description of the carbon cycle of a western Amazonian forest. Aims: We present the carbon budget of two forest plots in Tambopata in south-eastern Peru, western Amazonia. In particular, we present, for the first time, the seasonal variation in the detailed carbon budget of a tropical forest. Methods: We measured the major components of net primary production (NPP) and total autotrophic respiration over 3–6 years. Results: The NPP for the two plots was 15.1 ± 0.8 and 14.2 ± 1.0 Mg C ha−1 year−1, the gross primary productivity (GPP) was 35.5 ± 3.6 and 34.5 ± 3.5 Mg C ha−1 year−1, and the carbon use efficiency (CUE) was 0.42 ± 0.05 and 0.41 ± 0.05. NPP and CUE showed a large degree of seasonality. Conclusions: The two plots were similar in carbon cycling characteristics despite the different soils, the most notable difference being high allocation ...

Fire disturbance in Amazonian blackwater floodplain forests

Abstract: Background: Large fire scars were detected in floodplain forests of the middle Rio Negro in dry years of the 1990s, using satellite data. Aim: To relate fire years and river level anomalies to the Tropical Pacific Southern Oscillation Index (SOI); to measure fire damage and post-fire succession rate. Methods: We analysed the relationship between the SOI and water levels for 1968–2010. In Landsat images of the 1990s we determined fire scar ages. Using QuickBird images, we measured forest cover loss in 36 of these scars, covering 873 ha. This was validated by field measurements of tree mortality in 15 scars. As a metric of post-fire succession, we compared change in the Enhanced Vegetation Index (EVI) in 10 large floodplain fire scars and 12 terra firme slash-and-burn fallows. Results: SOI explained 32% of the variation in annual low water level. Forest cover loss in the 36 burn scars was 88% ± 8% (mean ± SD), range 67–98%. Post-fire tree mortality was 91%, ±8%, range 75–100%. Correlation between cover loss...

Disequilibrium and hyperdynamic tree turnover at the forest-cerrado transition zone in southern Amazonia

Abstract: Background: The zone of transition (ZOT) between the Cerrado and the Amazon forest in southern Amazonia represents a unique and rapidly shrinking area due to land-use change. Aims: To compare the dynamics and above-ground biomass of vegetation located in the ZOT with core Amazon forest and to determine how ZOT dynamics differ within vegetation types for different tree diameter classes. Methods: Censuses of trees were conducted in seven plots in monodominant forest, semi-deciduous seasonal forest, gallery forest, cerrado sensu stricto and cerradao, in north-eastern Mato Grosso, Brazil from 1996 to 2010, including data for the 2005 drought year. Separate analyses of stem dynamics and biomass were carried out for two different diameter (d) classes: 5 ≤ d < 10 cm and d ≥ 10 cm. Results: For trees with d ≥ 10 cm the average mortality rate was 2.8% year−1, with an estimated above-ground dry biomass of 210 Mg ha−1. Trees with 5 ≤ d < 10 cm constituted only a small fraction of the total biomass store (ca. 10 Mg h...

Spatial patterns of above-ground structure, biomass and composition in a network of six Andean elevation transects

Abstract: Background: The Amazon to Andes transition zone provides large expanses of relatively pristine forest wilderness across environmental gradients. Such elevational gradients are an excellent natural laboratory for establishing long-term interactions between forest ecosystems and environmental parameters, which is valuable for understanding ecosystem responses to environmental change. Aims: This study presents data on elevational trends of forest structure (biomass, basal area, height, stem density), species richness, and composition from six elevational transects in the Andes. Methods: We analysed the spatial patterns of forest structure, above-ground biomass and composition from 76 permanent plots, ranging from lowland Amazonian rain forest to high-elevation cloud forests in Ecuador, Peru, and Bolivia. Results: Forest above-ground woody biomass stocks ranged from 247 Mg ha−1 (Peru, 210 m) to 86 Mg ha−1 (Peru, 3450 m), with significantly decreasing trends of tree height and biomass and an increasing trend o...

Productivity and carbon allocation in a tropical montane cloud forest in the Peruvian Andes

Abstract: Background: The slopes of the eastern Andes harbour some of the highest biodiversity on Earth and a high proportion of endemic species However, there have been only a few and limited descriptions of carbon budgets in tropical montane forest regions Aims: We present the first comprehensive data on the production, allocation and cycling of carbon for two high elevation (ca 3000 m) tropical montane cloud forest plots in the Kosnipata Valley, Peruvian Andes Methods: We measured the main components and seasonal variation of net primary productivity (NPP), autotrophic (R a) and heterotrophic (R h) respiration to estimate gross primary productivity (GPP) and carbon use efficiency (CUE) in two 1-ha plots Results: NPP for the two plots was estimated to be 705 ± 039 and 804 ± 047 Mg C ha−1 year−1, GPP to be 2233 ± 223 and 2682 ± 297 Mg C ha−1 year−1 and CUE was 032 ± 004 and 030 ± 004 Conclusions: We found strong seasonality in NPP and moderate seasonality of R a, suggesting that forest NPP is dri

Ecosystem respiration and net primary productivity after 8–10 years of experimental through-fall reduction in an eastern Amazon forest

Abstract: Background: There is much interest in how the Amazon rainforest may respond to future rainfall reduction However, there are relatively few ecosystem-scale studies to inform this debate Aims: We described the carbon cycle in a 1 ha rainforest plot subjected to 8–10 consecutive years of ca 50% through-fall reduction (TFR) and compare these results with those from a nearby, unmodified control plot in eastern Amazonia Methods: We quantified the components of net primary productivity (NPP), autotrophic (R a) and heterotrophic respiration, and estimate gross primary productivity (GPP, the sum of NPP and R a) and carbon-use efficiency (CUE, the ratio of NPP/GPP) Results: The TFR forest exhibited slightly lower NPP but slightly higher R a, such that forest CUE was 029 ± 004 on the control plot but 025 ± 003 on the TFR plot Compared with four years earlier, TFR plot leaf area index and small tree growth recovered and soil heterotrophic respiration had risen Conclusions: This analysis tested and extended

Seasonal production, allocation and cycling of carbon in two mid-elevation tropical montane forest plots in the Peruvian Andes

Abstract: Background: Tropical montane cloud forests (TMCF) are unique ecosystems with high biodiversity and large carbon reservoirs. To date there have been limited descriptions of the carbon cycle of TMCF. Aims: We present results on the production, allocation and cycling of carbon for two mid-elevation (1500–1750 m) tropical montane cloud forest plots in San Pedro, Kosnipata Valley, Peru. Methods: We repeatedly recorded the components of net primary productivity (NPP) using biometric measurements, and autotrophic (R a) and heterotrophic (R h) respiration, using gas exchange measurements. From these we estimated gross primary productivity (GPP) and carbon use efficiency (CUE) at the plot level. Results: The plot at 1500 m was found very productive, with our results comparable with the most productive lowland Amazonian forests. The plot at 1750 m had significantly lower productivity, possibly because of greater cloud immersion. Both plots had similar patterns of NPP allocation, a substantial seasonality in NPP com...

Soil physical conditions limit palm and tree basal area in Amazonian forests

Abstract: Background: Trees and arborescent palms adopt different rooting strategies and responses to physical limitations imposed by soil structure, depth and anoxia. However, the implications of these differences for understanding variation in the relative abundance of these groups have not been explored. Aims: We analysed the relationship between soil physical constraints and tree and palm basal area to understand how the physical properties of soil are directly or indirectly related to the structure and physiognomy of lowland Amazonian forests. Methods: We analysed inventory data from 74 forest plots across Amazonia, from the RAINFOR and PPBio networks for which basal area, stand turnover rates and soil data were available. We related patterns of basal area to environmental variables in ordinary least squares and quantile regression models. Results: Soil physical properties predicted the upper limit for basal area of both trees and palms. This relationship was direct for palms but mediated by forest turnover ra...

The production, allocation and cycling of carbon in a forest on fertile terra preta soil in eastern Amazonia compared with a forest on adjacent infertile soil

Abstract: Background: Terra preta do indio or ‘dark earth’ soils formed as a result of a long-term addition of organic matter by indigenous peoples in Amazonia. Aims: Here we report on the first study of productivity, allocation and carbon cycling from a terra preta plot in eastern Amazonia (Caxiuana, Para, Brazil), and contrast its dynamics with a nearby plot on infertile soil (ferralsols). Methods: We determined total net primary production (NPP) for fine roots, wood, and canopy and total autotrophic respiration (rhizosphere, wood, and canopy respiration) from two 1-ha plots on contrasting soils. Results: Both gross primary productivity (GPP) (35.68 ± 3.65 vs. 32.08 ± 3.46 Mg C ha−1 year−1) and carbon use efficiency (CUE) (0.44 ± 0.06 vs. 0.42 ± 0.05) were slightly higher at the terra preta plot. Total NPP (15.77 ± 1.13 Mg C ha−1 year−1 vs. 13.57 ± 0.60 Mg C ha−1 year−1) and rates of fine root production (6.41 ± 1.08 vs. 3.68 ± 0.52 Mg C ha−1 year−1) were also greater at the terra preta plot vs. the tower plot. C...

Convergence and divergence in alternative successional pathways in Central Amazonia

Abstract: Background: Plant succession and community assembly following different land-use histories in the Amazon Basin are poorly understood. Aims: Changes in woody vegetation were monitored across chronosequences of abandoned pastures and abandoned clearcuts in order to compare their successional patterns. Methods: In chronosequences, initially 5–19 years old in abandoned clearcuts and 2–11 years old in abandoned pastures, trees (≥ 3 cm dbh) were tagged and recruitment and mortality recorded annually for 12 years. Results: Stem densities exhibited no significant trend during the first 25 years of succession regardless of land-use history. Basal area in abandoned clearcuts increased rapidly in the first decade, outpacing accumulation in abandoned pastures, although basal area on the two pathways converged at 25 years post-abandonment. Transects in abandoned pastures were much more variable in stem density and basal area than those in abandoned clearcuts, reflecting cohort growth and thinning by the dominant genus...

Invasion of Acacia mangium in Amazonian savannas following planting for forestry

Abstract: Background : No studies have examined the invasion of exotic species used for forestry purposes in the savannas of the Brazilian Amazonia. Aims : We investigated the invasion process of Acacia mangium in savanna areas adjacent to large-scale forestry plantations in north-eastern Roraima State, Brazilian Amazonia. Methods : A tree inventory to record the presence of all A. mangium and native tree individuals was carried out in of 14 plots (each 50 m in width and 1500 m in length) established at five plantation sites. Biometric measurements were taken for all individuals to identify their structure and maturity. Distance categories were created for determining frequency of occurrence in 100 m sections along the plots for all individuals. Correlations and goodness-of-fit tests for discrete data ordered in categories were applied to verify the occurrence of A. mangium plants in relation to distance from the plantation. Results : Individuals of A. mangium were dispersed up to 900 m from the plantation edge 8–9...

Ecosystem productivity and carbon cycling in intact and annually burnt forest at the dry southern limit of the Amazon rainforest (Mato Grosso, Brazil)

Abstract: Background: The impact of fire on carbon cycling in tropical forests is potentially large, but remains poorly quantified, particularly in the locality of the transition forests that mark the boundaries between humid forests and savannas. Aims: To present the first comprehensive description of the impact of repeated low intensity, understorey fire on carbon cycling in a semi-deciduous, seasonally dry tropical forest on infertile soil in south-eastern Amazonia. Methods: We compared an annually burnt forest plot with a control plot over a three-year period (2009–2011). For each plot we quantified the components of net primary productivity (NPP), autotrophic (R a) and heterotrophic respiration (R h), and estimated total plant carbon expenditure (PCE, the sum of NPP and R a) and carbon-use efficiency (CUE, the quotient of NPP/PCE). Results: Total NPP and R a were 15 and 4% lower on the burnt plot than on the control, respectively. Both plots were characterised by a slightly higher CUE of 0.36–0.39, compared to...

The productivity, allocation and cycling of carbon in forests at the dry margin of the Amazon forest in Bolivia

Abstract: Background: The dry transitional forests of the southern Amazonia have received little attention from a carbon cycling and ecosystem function perspective, yet they represent ecosystems that may be impacted by global climate change in the future. Aims: To compare the full carbon cycle for two 1-ha forest plots that straddle the ecotone between humid forest and dry forest in Amazonia, ca. 100 km from Santa Cruz, Bolivia. Methods: 2.5 years of measurements of the components of net primary production (NPP) and autotrophic respiration were collected. Results: Total NPP was 15.5 ± 0.89 Mg C ha−1 year−1 at the humid site and 11.27 ± 0.68 Mg C ha−1 year−1 at the dry site; a total Gross Primary Production (GPP) of 34.14 ± 2.92 Mg C ha−1 year−1 and 26.88 ± 2.70 Mg C ha−1 year−1 at the two sites. Carbon use efficiency for both sites was higher than reported for other Amazonian forests (0.45 ± 0.05 and 0.42 ± 0.05). Conclusions: Drier soil conditions selected for the dry deciduous tree species which had higher leaf p...

Basin-wide variations in Amazon forest nitrogen-cycling characteristics as inferred from plant and soil 15N:14N measurements

Abstract: Background: Patterns in tropical forest nitrogen cycling are poorly understood. In particular, the extent to which leguminous trees in these forests fix nitrogen is unclear. Aims: We aimed to determine factors that explain variation in foliar δ15N (δ15NF) for Amazon forest trees, and to evaluate the extent to which putatively N2-fixing Fabaceae acquire nitrogen from the atmosphere. Methods: Upper-canopy δ15NF values were determined for 1255 trees sampled across 65 Amazon forest plots. Along with plot inventory data, differences in δ15NF between nodule-forming Fabaceae and other trees were used to estimate the extent of N2 fixation. Results: δ15NF ranged from −12.1‰ to +9.3‰. Most of this variation was attributable to site-specific conditions, with extractable soil phosphorus and dry-season precipitation having strong influences, suggesting a restricted availability of nitrogen on both young and old soils and/or at low precipitation. Fabaceae constituted fewer than 10% of the sampled trees, and only 36% we...

Seasonal patterns of leaf-level photosynthetic gas exchange in an eastern Amazonian rain forest

Abstract: Background: Global changes are challenging the equilibrium in the Amazon. Understanding how that biome responds to seasonality in water availability is essential to build scenarios of ecosystem functioning in the near future. Aims: Our aim was to test for seasonal variations in leaf traits related to primary productivity. Methods: Chemical composition, mass to area ratio and photosynthetic response curves to light and CO2 and of stomatal conductance (gs) to leaf-to-air water pressure deficit (ν) were determined from leaves of Amazonian trees and lianas. Results: Weak responses of gs to ν suggested limited stomatal control over transpiration. Dry season stomatal limitation of photosynthesis was not a common feature as only one individual studied (out of 14) exhibited concomitant decreases in light saturated photosynthetic rate (ASat )a ndgs (measured during ASat) associated with the dry season. Furthermore, 75% of the individuals evaluated did not show decreased photosynthetic capacity (Vcmax) during the dry season, suggesting limited seasonal leaf acclimation. Grouped analyses indicated that most parameters evaluated remained constant across seasons. The exceptions were leaf nitrogen and its isotopic signature, and the integrated stomatal sensitivity to light, CO2 and ν. Conclusions: These findings reinforce the notion that the dry season in eastern Amazonia is not associated with significant limitations in leaf-level photosynthesis.

Age and light effects on seedling growth in two alternative secondary successions in central Amazonia

Abstract: Background : In central Amazonia, previous low intensity land use engenders succession dominated by Cecropia spp. which proceeds at high rates; however, at higher intensity of use succession is arrested and dominated by Vismia spp. over the long-term. Factors driving these two successional pathways are unknown. Aims : We aimed to elucidate seedling growth under the two alternative successional pathways. Methods : We experimentally determined the effects of successional age and photosynthetically active radiation (PAR) on relative height growth (RHG) of nine species of shade-tolerant tree seedlings in secondary forests dominated by Cecropia and Vismia, varying in age from 1–20 years. Results : In Cecropia-dominated successions, seedling RHG decreased with increasing successional age and with associated decreasing PAR. In Vismia-dominated successions, RHG was independent of successional age and PAR, and PAR did not change with successional age, being always higher than in Cecropia stands. The RHG of seedlin...

Changes in forest structure and composition after fire in tropical montane cloud forests near the Andean treeline

Abstract: Background: In tropical montane cloud forests (TMCFs) fires can be a frequent source of disturbance near the treeline. Aims: To identify how forest structure and tree species composition change in response to fire and to identify fire-tolerant species, and determine which traits or characteristics are associated with fire tolerance. Methods: Shifts in forest structure and diversity were assessed on 15 paired plots in burnt and unburnt (control) forests, along a fire chronosequence. Species were classified as fire-sensitive, fire survivors or fire thrivers, using a fire tolerance index. Regression and tree analyses were used to determine which traits contributed to the fire tolerance of species. Results: There were more small- and medium-sized trees in the burnt plots independent of time since the last fire. There were shifts in family importance value and in species diversity among the plots. Of the 73 species analysed there were 39 fire-sensitive species, 19 fire survivors and 14 fire thrivers. Sprouting...

Patterns of seed dispersal syndromes on serpentine soils: examining the roles of habitat patchiness, soil infertility and correlated functional traits

Abstract: Background: It is critical to understand the ecological factors shaping seed dispersal in plant communities in order to predict their fate in the face of global change. Communities restricted to patchy habitats may contain more species with ‘directed’ dispersal syndromes that facilitate successful seed dispersal to other patches; however, habitat quality may constrain the presence of and efficiency of dispersal syndromes found within those habitats.Aims: The aim of this study was to hypothesise that if habitat patchiness is an important filter on dispersal syndromes, ‘directed’ vertebrate dispersal should be more prevalent in serpentine habitats because of their patchiness. Alternatively, if habitat quality is more important, wind dispersal should be more prevalent in serpentine habitats because of their low fertility.Methods: Using three datasets representing grassland, chaparral and forest vegetation types, we analysed differences in the composition of dispersal syndromes (vertebrate, wind, pass...

The ecosystem dynamics of Amazonian and Andean forests

Abstract: The importance of Amazonian and Andean rain forests in the Earth System cannot be overstated. They store ca. 100 billion tonnes of carbon in their biomass (Malhi et al. 2006; Saatchi et al. 2007), ...

The seasonal cycle of productivity, metabolism and carbon dynamics in a wet aseasonal forest in north-west Amazonia (Iquitos, Peru)

Abstract: Background: The forests of north-west Amazonia are characterised by the highest levels of tree diversity in the world, high rainfall and relatively fertile soils. Aims: Here we present a comprehensive description of the carbon cycle of two 1 ha forests plots in Allpahuayo, near Iquitos, Peru, one on an occasionally inundated alisol/gleysol landscape, the other on an arenosol (sandy soil). Methods: Data on the components of net primary productivity (NPP) and autotrophic respiration were collected over the period 2009–2011, and summed to estimate gross primary productivity (GPP) and carbon use efficiency (CUE). Results: Overall, these forests showed high values of GPP (39.05 ± 4.59 and 41.88 ± 4.60 Mg C ha−1 year−1). Despite the lack of a dry season, the forests showed distinct seasonality in tree growth, litterfall, flowering and fine root productivity. This showed that tropical forests with little seasonality in water supply can still exhibit distinct seasonality in NPP and carbon use, apparently synchron...

Assessing above-ground woody debris dynamics along a gradient of elevation in Amazonian cloud forests in Peru: balancing above-ground inputs and respiration outputs

Abstract: Background: Dead biomass, including woody debris (WD), is an important component of the carbon cycle in tropical forests. Aims: This study analyses WD (>2 cm) and other above-ground fluxes in mature tropical forest plots along an elevational gradient (210–3025 m above sea level) in southern Peru. Methods: This work was based on inventories of fine and coarse WD (FWD and CWD, respectively), above-ground biomass, and field-based and experimental respiration measurements. Results: Total WD stocks ranged from 6.26 Mg C ha−1 at 3025 m to 11.48 Mg C ha−1 at 2720 m. WD respiration was significantly correlated with moisture content (P < 0.001; R 2 = 0.25), temperature (P < 0.001; R 2 = 0.12) and wood density (P < 0.001; R 2 = 0.16). Controlled experiments showed that both water content and temperature increased respiration rates of individual WD samples. The full breadth of the temperature sensitivity coefficient, or Q 10, estimates, ranging from 1.14–2.13, was low compared to other studies. In addition, temperat...

Gap formation and carbon cycling in the Brazilian Amazon: measurement using high-resolution optical remote sensing and studies in large forest plots

Abstract: Background: The dynamics of gaps plays a role in the regimes of tree mortality, production of coarse woody debris (CWD) and the variability of light in the forest understory. Aims: To quantify the area affected by, and the carbon fluxes associated with, natural gap-phase disturbances in a tropical lowland evergreen rain forest by use of ground measurements and high-resolution satellite images. Methods: We surveyed two large forest inventory plots of 114 and 53 ha of the Tapajos National Forest (TNF) in the Brazilian Amazon during 2008 and 2009, respectively. We mapped all gaps and collected data on light availability, CWD stocks and tree mortality in the field. Gap location, canopy openness (CO) and leaf area index (LAI) estimated in the field were compared with two IKONOS–2 high-resolution satellite images acquired at approximately the time of the field measurements. Results: In the two large plots (167 ha total area) we found 96 gaps. The gaps represented 1.42% of the total area and gaps <1-year-old acc...

Fifty years of vegetation change in oceanic-montane liverwort-rich heath in Scotland

Abstract: Background: Liverwort heath is considered in Scotland to be one of the vegetation types most vulnerable to environmental change, yet detailed insights into its dynamics are lacking.Aims: To assess the nature and extent of plant compositional changes in liverwort heath over 50 years and relate this to environmental change drivers.Methods: Vegetation plots previously recorded 20 and 50 years ago were re-surveyed to assess changes in species composition, plot-level species richness and between-plot variability, using several β-diversity indices and partitioning. The environmental indicator values of the species that showed most change were used to identify the environmental drivers of change.Results: Liverwort heath in north-west Scotland has undergone compositional changes over 50 years, becoming more heterogeneous, and losing some of its distinct character. Dwarf shrubs and specialist liverworts have decreased, while graminoids have increased. Partitioning of change in β diversity indicated that mainly cha...

Shifting dynamics of climate-functional groups in old-growth Amazonian forests

Abstract: Background: Climate change is driving ecosystem shifts, which has implications for tropical forest system function and productivity. Aim: To investigate Amazon forest dynamics and test for compositional changes between 1985 and 2005 across different plant groups. Methods: Tree census data from 46 long-term RAINFOR forest plots in Amazonia for three climate-functional groups were used: dry-affiliate, climate-generalist and wet affiliate. Membership of each group was ascribed at genus level from the distribution of individuals across a wet–dry gradient in Amazonia, and then used to determine whether the proportions of these functional groups have changed over time, and the direction of any change. Results: In total, 91 genera, representing 59% of the stems and 18% of genera in the plots, were analysed. Wet-affiliates tended to move from a state of net basal area gain towards dynamic equilibrium, defined as where gain ≈ loss, governed by an increase in loss rather than a decrease in growth and mainly driven ...

Dissolved organic carbon concentration and its relationship to electrical conductivity in the waters of a stream in a forested Amazonian blackwater catchment

Abstract: Background: Dissolved organic carbon (DOC) is a major component of the total carbon in headstreams in Amazonia. Long-term measurements of DOC concentration are difficult to obtain in remote areas of Amazonia. Aims: To take measurements of electrical conductivity (EC) and DOC concentration in a blackwater stream and to determine whether it is possible to make predictions of the DOC concentration in such streams using continuous measurements of EC alone. Methods: In a forested area, DOC concentration and EC were measured in groundwater along a topographic gradient at weekly intervals over a period of 8 months, and in stream water at half-hourly intervals over 2 years. Results: Strong and positive relationships between EC and DOC concentration were found in stream water in wet (r 2 = 0.99) and dry periods (r 2 = 0.97). It was thus possible to produce two equations that could be used to derive DOC concentration values from continuous measurements of EC. Both DOC concentration and EC varied according to the di...

The effect of harsh abiotic conditions on the diversity of serpentine plant communities on Lesbos, an eastern Mediterranean island

Abstract: Background: Diversity patterns of plant communities are related to the environment, including productivity and patchiness of habitat.Aims: To determine differences in diversity patterns between serpentine and non-serpentine communities.Methods: A two-year study was conducted in native eastern Mediterranean grasslands. For each year 40 0.25 m2 plots were sampled across four pairs of sites, each of which contained a serpentine and an adjacent non-serpentine plant community. Alpha and beta diversity (variation in species composition among plots within localities), species composition and biomass production were determined. Total soil elemental concentrations and pH were also measured.Results: Serpentine habitats were shown to support a lower alpha diversity relative to non-serpentine habitatas on a per plot basis. Differences in alpha diversity between the two substrates were associated with variation in soil chemistry rather than above-ground biomass production. Serpentine habitats also exhibited lower beta...

Expanding the coverage of plant trait databases – A comparison of specific leaf area derived from fresh and dried leaves

Abstract: Background: Specific leaf area (SLA) is a key plant functional trait, related to leaf life span, nutrient concentrations and photosynthetic rates, among other factors. However, a limiting factor in measuring these traits is that they are taken from fresh leaves. If accurate SLA measurements could be extracted from dried herbarium specimens, values for many more species could be rapidly included in large trait databases. Aims: To determine whether artificial drying of leaves could influence subsequent calculations of SLA compared to calculations using fresh leaf area. Methods: Using data from 449 leaves from 123 tropical species, we compared leaf area and SLA of fresh leaves with leaf area and SLA of the same leaves following standard pressing and drying procedures. Drying was carried out in the field using an electric heater. Results: We found a significant decrease in leaf area following pressing and artificial drying (mean decrease = 8%), but that this effect was less in larger leaves. This decrease in ...

Mycorrhizal ecology on serpentine soils

Abstract: Background: Serpentine ecosystems support different, often unique, plant communities; however, we know little about the soil organisms that associate with these ecosystems. Mycorrhizas, mutualistic symbioses between fungi and roots, are critical to nutrient cycling and energy exchange below ground.Aims: We address three hypotheses: H1, diversity of mycorrhizal fungi in serpentine soils mirrors above-ground plant diversity; H2, the morphology of mycorrhizas and fungi on serpentine soils differs from that on non-serpentine; and H3, mycorrhizal fungal communities of the same or closely related hosts differ between serpentine and non-serpentine soils.Methods: This review focuses on whether plant diversity on serpentine soils correlates with the below ground diversity of mycorrhizal fungi.Results: Studies show that plants and fungi formed abundant ectomycorrhizal and arbuscular mycorrhizal symbioses on and off serpentine soils. No serpentine-endemic fungi were identified. Molecular analyses indicate distinct s...

Diversity, abundance and distribution of lianas of the Cerrado-Amazonian forest transition, Brazil

Abstract: Background: Lianas strongly influence tropical forest dynamics and diversity. Aims: To determine the relationship among richness, diversity, abundance and distribution of liana species in different vegetation formation types along a gradient within a savanna–forest transition zone in central Brazil. Methods: All liana species were identified and their girth measurements (≥5 cm) taken in one 1 ha plot at each of 15 sites that encompassed a range of vegetation types: dystrophic cerradao (tall closed woodland cerrado), gallery forest, flooded forest, semi-deciduous seasonal forest (one monodominant) and evergreen forest. We evaluated and compared the communities in terms of richness, community diversity (Shannon's H’), equitability (Hurlbert's, PIE), and the distribution of liana abundance. Results: In total, 1467 individual lianas belonging to 65 species, 41 genera and 17 families were recorded in the 15 ha sampled. The value of H’ varied from 0–2.47, and that of PIE ranged from 0–0.90. While flooded forest...