Publications

Isopod mouthpart traits respond to a tropical forest recovery gradient

Functional trait ecology has the potential to provide generalizable and mechanistic predictions of ecosystem function from data of species distributions an

Leaf damage by herbivores and pathogens on New Zealand islands that differ in seabird densities

Seabirds impose a high-nutrient, high-disturbance regime on the islands on which they nest, resulting in higher nutrient cycling rates, plant nutrient uptake and leaf nutrient content. On islands off the coast of New Zealand, seabird-dominated islands support greater densities of soil- and litter-dwelling consumer biota. We predicted that islands with high seabird densities would have higher levels of leaf damage as a result of higher densities of foliar consumers (herbivores and pathogens). Damage levels on leaves of six common tree species were compared between 9 islands with active seabird colonies and 10 islands with low seabird densities resulting from invasion by predatory rats. There were no consistent differences in leaf damage by chewing, mining, or phloem-feeding herbivores across plant species; pathogen damage was lower on islands with high seabird densities than on those with low densities, but this was driven by only two of the plant species. Instead, plant species differed in which of several possible damage types responded to seabird presence, and in which plant leaf traits responded to seabird-related environmental changes. Across plant species, those with more resource-acquisitive leaf traits such as high percent nitrogen and low structural investment experienced higher levels of chewing damage (which accounted for 66-100% of all damage), but not other damage types. We conclude that the fertilisation and disturbance regimes imposed by seabirds do not lead to consistent changes in consumer damage to plants, because of variable responses by both individual plant species and different consumer groups.

Disentangling global soil fungal diversity

A worldwide sampling effort reveals the global drivers of soil fungal biodiversity [Also see Research Article by Tedersoo et al. ]

Thermal characteristics of various biomass fuels in a small-scale biomass combustor

Biomass combustion is a mature and reliable technology, which has been used for heating and cooking. In the UK, biomass currently qualifies for financial incentives such as the Renewable Heat Incentive (RHI). Therefore, it is vital to select the right type of fuel for a small-scale combustor to address different types of heat energy needs. In this paper, the authors attempt to investigate the performance of a small-scale biomass combustor for heating, and the impact of burning different biomass fuels on useful output energy from the combustor. The test results of moisture content, calorific value and combustion products of various biomass samples were presented. Results from this study are in general agreement with published data as far as the calorific values and moisture contents are concerned. Six commonly available biomass fuels were tested in a small-scale combustion system, and the factors that affect the performance of the system were analysed. In addition, the study has extended to examine the magnitude and proportion of useful heat, dissipated by convection and radiation while burning different biomass fuels in the small-scale combustor. It is concluded that some crucial factors have to be carefully considered before selecting biomass fuels for any particular heating application.

Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence

Nitrogen (N) and carbon (C) isotopic signatures (δ15N and δ13C) serve as powerful tools for understanding temporal changes in ecosystem processes

Chapter One - A multitrophic perspective on biodiversity–ecosystem functioning research

The influence of the herbicide glyphosate on interspecific interactions between four soil fungal species

The influence of the herbicide glyphosate on two-way interactions between four fungal species was investigated on agar using direct opposition, volatile inhibitor and non-volatile inhibitor tests, and on barley straw using tests for competitive saprotrophic ability. The results indicated that glyphosate was often capable of shifting the direction of two-species interactions, but there was little agreement between the different tests. Reanalysis of particle colonization data presented earlier demonstrated that glyphosate frequently eliminated negative associations between the same four species, possibly by acting as a resource. It is concluded that interactions between pairs of fungi can be influenced directly by glyphosate (especially at high concentrations) and that this may influence soil fungal community structure.

Analysis of co-occurrence in a fungal community

An approach is presented for quantifying associations between species pairs over a scale of 0·5–1 mm by plating several 0·5–1 mm particles of washed organic matter on agar plates, and observing whether or not fungal species which emerge from the particles are distributed in a random manner with regard to each other. Most of the associations between the seven most abundant species in particles of organic matter from an agricultural soil were significantly negative. Co-occurrence of these species was weakly, but significantly, related to their correlation patterns across samples collected over a spatial scale of several metres.

Aboveground and belowground legacies of native Sami land use on boreal forest in northern Sweden 100 years after abandonment

Human activities that involve land‐use change often cause major transformations to community and ecosystem properties both aboveground and belowground, and when land use is abandoned, these modifications can persist for extended periods. However, the mechanisms responsible for rapid recovery vs. long‐term maintenance of ecosystem changes following abandonment remain poorly understood. Here, we examined the long‐term ecological effects of two remote former settlements, regularly visited for ∼300 years by reindeer‐herding Sami and abandoned ∼100 years ago, within an old‐growth boreal forest that is considered one of the most pristine regions in northern Scandinavia. These human legacies were assessed through measurements of abiotic and biotic soil properties and vegetation characteristics at the settlement sites and at varying distances from them. Low‐intensity land use by Sami is characterized by the transfer of organic matter towards the settlements by humans and reindeer herds, compaction of soil through trampling, disappearance of understory vegetation, and selective cutting of pine trees for fuel and construction. As a consequence, we found a shift towards early successional plant species and a threefold increase in soil microbial activity and nutrient availability close to the settlements relative to away from them. These changes in soil fertility and vegetation contributed to 83% greater total vegetation productivity, 35% greater plant biomass, and 23% and 16% greater concentrations of foliar N and P nearer the settlements, leading to a greater quantity and quality of litter inputs. Because decomposer activity was also 40% greater towards the settlements, soil organic matter cycling and nutrient availability were further increased, leading to likely positive feedbacks between the aboveground and belowground components resulting from historic land use. Although not all of the activities typical of Sami have left visible residual traces on the ecosystem after 100 years, their low‐intensity but long‐term land use at settlement sites has triggered a rejuvenation of the ecosystem that is still present. Our data demonstrates that aboveground–belowground interactions strongly control ecosystem responses to historical human land use and that medium‐ to long‐term consequences of even low‐intensity human activities must be better accounted for if we are to predict and manage ecosystems succession following land‐use abandonment.

Variation in protein complexation capacity among and within six plant species across a boreal forest chronosequence

We investigated among and within species variation in several litter chemical properties, including protein complexation capacity (PCC), for six plant spec

Yield and Berry Composition of Five<i>Vitis</i>Cultivars as Affected by<i>Rupestris</i>Stem Pitting Virus

Rooted cuttings of Kerner (<i>Vitis vinifera</i>), Michurinetz (<i>V. amurensis</i> X), and Okanagan Riesling (<i>V. labrus- cana</i> X), either virus-free or infected with <i>Rupestris</i> stem pitting virus (RSPV), were planted in 1987 in a randomized block experiment at Summerland, British Columbia (arid continental climate). Also, virus-free and RSPV-infected plants Madeleine Sylvaner, and Ortega (both <i>V. vinifera</i>) were planted in a completely randomized experiment at Saanichton Plant Quarantine Station, Sidney, BC (cool maritime climate). Yield components were not affected at the Summerland site, but weight of cane prunings were reduced in RSPV- infected Michurinetz vines in 1995-96. RSPV also lowered yield and clusters per vine of both cultivars in 1994 at Sidney, along with Ortega weight of cane prunings (1993 and 1994) and berry weight (1994). Berry titratable acidity (TA) at harvest was reduced at both sites in RSPV-infected vines, and pH was concomitantly increased. TA was consistently lower and the pH was always higher in the RSPV berries during veraison to harvest at Summerland. No apparent negative impact of RSPV was observed except delayed soluble solids (°Brix) accumulation in RSPV-infected Kerner and Okanagan Riesling vines at Summerland in 1991, and lower °Brix in Ortega RSPV berries at Sidney in 1993. In some seasons, fruit composition differences between virus-free and RSPV vines disappeared close to commercial maturity, but lower TA and higher pH persisted until harvest at the Summerland site in 1993. RSPV-infected vines at Sidney exhibited slightly delayed budburst in 1988-91 and 1994, but not 1993. These results suggest that RSPV has no major impact on grapevine growth and yield, and may advance fruit maturity in terms of TA and pH.

Release of mineral nitrogen from plant root nodules

Root nodules from a variety of nodulated leguminous and non-leguminous plants were added to soil samples and the net release of mineral N was monitored periodically for 56 or 98 days. Over these periods, various nodules demonstrated either net N immobilisation, mineralisation, or immobilisation followed by mineralisation. No nodular tissue mineralised > 30% of its organic N content. Mineral N release from the nodules was not significantly related to their C to N ratios or organic N content (r = 0.410). Nitrogen fractionation data from these nodules indicated that the main forms of N present in combined form were α-amino N and hydrolysable unidentified N(HUN). Attempts to relate mineral N release to the forms of N present in the nodules indicated that nodule N mineralisation was significantly related to nodule concentration of NH4-N and hexosamine-N in combination (r =0.741). It was concluded that these two components are probably highly important in regulating mineral N release from decomposing root nodules.

Long-term drivers of aboveground-belowground linkages and ecosystem functioning

No abstract is provided for this article.

Biodiversity and Ecosystem Function: An Issue in Ecology

No abstract is provided for this article.

Do 'Faculty of 1000' (F1000) ratings of ecological publications serve as reasonable predictors of their future impact?

There is an increasing demand for an effective means of post-publication evaluation of ecological work that avoids pitfalls associated with using the impact factor of the journal in which the work was published. One approach that has been gaining momentum is the 'Faculty of 1000' (hereafter F1000) evaluation procedure, in which panel members identify what they believe to be the most 'important' recent publications they have read. Here I focused on 1530 publications from 7 major ecological journals that appeared in 2005, and compared the F1000 rating of each publication with the frequency with which it was subsequently cited. The mean and median citation frequencies of the 103 publications highlighted by F1000 was higher than for all 1530 publications, but not substantially so. Further, the F1000 procedure did not highlight any of the 11 publications that were each cited over 130 (and up to 497) times, while it did highlight 14 publications that were each cited between 4 and 9 times. Further, 46% and 31% of all manuscripts highlighted by F1000 were cited less often than the mean and median respectively of all 1530 publications. Possible reasons for the F1000 process failing to identify high impact publications may include uneven coverage by F1000 of different ecological topics, cronyism, and geographical bias favoring North American publications. As long as the F1000 process cannot identify those publications that subsequently have the greatest impact, it cannot be reliably used as a means of post-publication evaluation of the ecological literature.

Among‐ and within‐species variation in plant litter decomposition in contrasting long‐term chronosequences

1 Following major disturbances ecosystem development occurs but in the prolonged absence of disturbance a decline (retrogressive) phase follows in which productivity and nutrient availability diminishes. Although it is recognized that litter quality and decomposition rates decrease as retrogression proceeds, little is known about the extent to which this is driven among- vs. within-species variation across these sequences. 2 We selected six long-term chronosequences that each included retrogressive stages, in New Zealand, Hawaii, Sweden, Alaska and Australia. Two involve significant species turnover across the sequence so that different species dominate at different stages, two involve low species turnover so that the same dominant species occur at all stages, and two involve some turnover of species but with certain species persisting throughout most of the sequence. 3 For each chronosequence, we collected litter from each dominant plant species at each stage of that sequence. For each litter collection we measured concentrations of N and P, and performed laboratory decomposition bioassays to measure mass loss, N and P loss, and the response of mass loss to mixture with litters of coexisting species. 4 We found that litter N and P concentrations often declined with increasing ecosystem age, both among- and within-species. However, the relative importance of among- and within-species effects varied across the six chronosequences. Rates of litter mass, N, and P loss during decomposition sometimes decreased with increasing ecosystem age, but most often at the among-species rather than the within-species level. 5 Litter mixing effects often varied across chronosequence stages, but the magnitude and direction of these effects was inconsistent among sequences. Variation in litter mixing effects across chronosequence stages was driven mainly by among- rather than within-species variation. 6 Although several recent studies have emphasized the role of within-species variation on ecosystem properties, our results point to among-species variation as a consistently important ecological driver, with within-species variation being important only for some variables and in some instances. As such they highlight that decomposition processes are most likely to be highly responsive to gradients of soil fertility (such as across chronosequences) when significant species turnover occurs across the gradient.

Context dependent effects of plant species and functional group loss on vegetation invasibility across an island area gradient

1 There has been much debate about how losses of species and functional groups may affect the invasibility of vegetation, but little is understood about how invasibility differs across ecosystems or is driven by environmental context. 2 We studied the invasibility of field plots in two ongoing removal experiments set up across thirty lake islands in northern Sweden. These islands differ in size, and therefore soil fertility and productivity. One experiment involves full factorial removal of three functional groups (dwarf shrubs, mosses and tree roots), and the other involves full factorial removal of three species of dwarf shrub (Vaccinium myrtillus, V. vitis-idaea and Empetrum hermaphroditum). 3 We investigated the effects of removal treatments in both experiments on the invasibility of each of three species (Betula pubescens, Pinus sylvestris and Picea abies). This included a seed sowing study, and a seedling planting study, for each of the three species. 4 For the functional group experiment, removal of shrubs promoted invasibility by all species, and removal of mosses also had positive effects. For the species removal experiment, the two Vaccinium species exerted the strongest effects against invasibility. The floristic components that had the greatest effects represented only a small proportion of total plant biomass. 5 The effects of the removal of shrubs (or of either Vaccinium species) on invasibility often varied across island size classes. In these cases, removals usually had the greatest positive effects on the largest and most productive islands. In contrast, the effects of moss removals on P. sylvestris seedling survival were greatest on small islands. 6 These results show clearly that the effects of loss of components of the resident flora (at either the functional group or species level) on invasibility at the plot scale are context dependent, and can vary greatly across ecosystems. 7 Synthesis. Our results contribute to the ongoing debate about how loss of species and functional groups influences community-level processes, by showing that the effects of loss of resident biota on invasion of new species depends on the attributes of the biota that are lost and the ecosystems that they are lost from.

Biological and biochemical quality of pastoral soils: spatial and temporal variability

This paper reports results of the first year of soil biochemical and microbiological monitoring programme carried out to establish "normal" ranges of values for these soil attributes. Study was conducted on 24 farm sites on yellow-brown loam soils around the Waikato area. Twelve dairy farms and a similar number of sheep-beef farms were selected on the basis of high productivity. Soil samples (0-75 mm depth) were collected at 3- monthly intervals and the following measurements were carried out: soil microbial- C, N, S and P, CO2 evolution, substrate-induced respiration, anaerobic mineralisable N, dehydrogenase activity, fluorescein diacetate (FDA) hydrolysis, amounts of soluble-C and N, extractable NO3 and NH4, soil pH, Olsen P, KH2PO4 extractable SO4-S and organic S, and hydraulic conductivity. Climatic data, records of fertiliser and other additives and productivity were also collected to interpret the variations in these properties. Variables measured from the Horotiu and Tirau silt loam soils showed considerable similarity, however, Otorohanga soils had significantly higher amounts of total and extractable soil C and N. As expected, being a higher input system, soil nutrient status (P, SO4, NO3 and NH4) on dairy farms was generally higher than the sheep-beef farms. The most significant difference was for the Olsen P values, which were about 60-70% higher under dairying. Soil pH on dairy farms was significantly higher than sheep- beef farms. However, total C and N values were significantly higher under sheep-beef than dairy farms. Similarly, the amounts of mineralisable N in all seasons were much higher for the sheep-beef than dairy farms. Apart from total microbial S, none of the other microbial biomass measurements showed any significant effect of season or difference among the soil types. This lack of seasonal effect on microbial biomass can be attributed to the unusual mild seasonal variation during the study. For the various microbial biomass measurements, sheep-beef farms generally had significantly higher values than dairy farms. Microbial C, N, SO4 and total S values were significantly higher for sheep-beef than dairying. The ratios between soil C, N to microbial C, N and microbial C:N showed no consistent pattern between the farm types. Keywords: C and N, enzyme activity, microbial biomass, seasonal variations, soil fertility