Soil carbon stocks under grazed pasture and pasture-tree systems.

There is increasing interest in the potential of trees to sequester carbon (C) in above- and below-ground stocks to mitigate against increasing concentrations of greenhouse gases (GHG). This study determined whether pasture-tree (PT) systems influence soil C stocks compared with open pasture (OP) by sampling four sites with trees aged 14 to16 years. Poplars (Populus spp.) at Tikokino and Woodville and alders (Alnus spp.) at Poukawa and Ruakura were planted on contrasting soils (Haplustands, Endoaquepts, Durustalfs and Humaquepts, respectively). Trees at all four sites were arranged in partial-Nelder radial planting designs, with five stem densities ranging from 67 to 1276 stems ha-1. Soils were sampled at five stem density classes, along with adjacent OP areas in the same paddock, to a depth of 1 m (0-75, 75-150, 150-300, 300-600, 600-1000 mm). At three of the four sites, root mass density was greater (P < 0.05) in PT than in OP systems. At Woodville, estimates of total soil C mass to 1 m tended to be greater (P = 0.08) in the OP than in the PT system (200 vs. 163 Mg C ha-1, respectively), whereas no significant differences in total soil C masses between OP and PT were shown at the remaining sites (P > 0.10). Despite the limited statistical significance, estimates of total soil C mass at Tikokino and Woodville (sites with poplars) were 11 and 18% greater in OP than in PT systems, whereas estimates at Poukawa and Ruakura (sites with alders) were 2 and 6% greater in PT than in OP systems. Under the current conditions, our study suggests that tree species may be an additional factor influencing the C cycle and C accumulation in soils and need to be considered in the building of our soil C inventories.

Verbal Descriptions of Cue Direction Affect Object Desirability.

Approach-avoidance behaviors are observed across a broad range of species. For humans, we tend move toward things we like, and away from things we dislike. Previous research tested whether repeatedly shifting visuo-spatial attention toward an object in response to eye gaze cues can increase liking for that object. Here, we tested whether a gaze-liking effect can occur for verbal descriptions of looking behavior without shifts of attention. Also, we tested the gaze specificity hypothesis - that the liking effect is specific to gaze cues - by comparing the effect of different types of cue (pointing gestures and arrow cues). In Experiment 1, participants (N = 205) were split into 5 groups according to the type of cue that was described as directed either toward or away from an object. The results show that (1) attention is not necessary; the liking effect was recorded for verbal descriptions of looking, (2) the effect also occurs for descriptions of pointing and arrows, and (3) the liking effect is enhanced for gaze cues compared to arrows, consistent with the gaze specificity hypothesis. Results from a further experiment suggest that the effect is not due to demand compliance. We conclude that the gaze-liking effect occurs for verbal descriptions of eye gaze. Indeed, because our method bypasses altogether the use of visual cues, objects, and shifts in visual selective attention, our paradigm appears to be more sensitive at tapping into the fundamental approach-avoidance response that mediate the implicit liking effect. As such, it offers new opportunities for research investigations in the future.

Prediction of extinction in plants: interaction of extrinsic threats and life history traits.

The global extinction of species proceeds through the erosion of local populations. Using a 60-year time series of annual sighting records of plant species, we studied the correlates of local extinction risk associated with a risk of species extinction in the Park Grass Experiment where plants received long-term exposure to nutrient enrichment, soil acidification, and reductions in habitat size. We used multivariate linear models to assess how extrinsic threats and life history traits influence extinction risk. We investigated effects of four extrinsic threats (nitrogen enrichment, productivity, acidification, and plot size) as well as 11 life history traits (month of earliest flowering, flowering duration, stress tolerance, ruderalness [plant species' ability to cope with habitat disturbance], plant height, diaspore mass, seed bank, life form, dispersal mode, apomixis [the ability for a species to reproduce asexuall through seeds], and mating system). Extinction risk was not influenced by plant family. All of the 11 life history traits except life form and all threat variables influenced extinction risk but always via interactions which typically involved one threat variable and one life history trait. We detected comparatively few significant interactions between life history traits, and the interacting traits compensated for each other. These results suggest that simple predictions about extinction risk based on species' traits alone will often fail. In contrast, understanding the interactions between extrinsic threats and life history traits will allow us to make more accurate predictions of extinctions.

Nitrogen Cycling from Increased Soil Organic Carbon Contributes Both Positively and Negatively to Ecosystem Services in Wheat Agro-Ecosystems.

Soil organic carbon (SOC) is an important and manageable property of soils that impacts on multiple ecosystem services through its effect on soil processes such as nitrogen (N) cycling and soil physical properties. There is considerable interest in increasing SOC concentration in agro-ecosystems worldwide. In some agro-ecosystems, increased SOC has been found to enhance the provision of ecosystem services such as the provision of food. However, increased SOC may increase the environmental footprint of some agro-ecosystems, for example by increasing nitrous oxide emissions. Given this uncertainty, progress is needed in quantifying the impact of increased SOC concentration on agro-ecosystems. Increased SOC concentration affects both N cycling and soil physical properties (i.e., water holding capacity). Thus, the aim of this study was to quantify the contribution, both positive and negative, of increased SOC concentration on ecosystem services provided by wheat agro-ecosystems. We used the Agricultural Production Systems sIMulator (APSIM) to represent the effect of increased SOC concentration on N cycling and soil physical properties, and used model outputs as proxies for multiple ecosystem services from wheat production agro-ecosystems at seven locations around the world. Under increased SOC, we found that N cycling had a larger effect on a range of ecosystem services (food provision, filtering of N, and nitrous oxide regulation) than soil physical properties. We predicted that food provision in these agro-ecosystems could be significantly increased by increased SOC concentration when N supply is limiting. Conversely, we predicted no significant benefit to food production from increasing SOC when soil N supply (from fertiliser and soil N stocks) is not limiting. The effect of increasing SOC on N cycling also led to significantly higher nitrous oxide emissions, although the relative increase was small. We also found that N losses via deep drainage were minimally affected by increased SOC in the dryland agro-ecosystems studied, but increased in the irrigated agro-ecosystem. Therefore, we show that under increased SOC concentration, N cycling contributes both positively and negatively to ecosystem services depending on supply, while the effects on soil physical properties are negligible.

Absence of phylogenetic signal in the niche structure of meadow plant communities.

A significant proportion of the global diversity of flowering plants has evolved in recent geological time, probably through adaptive radiation into new niches. However, rapid evolution is at odds with recent research which has suggested that plant ecological traits, including the beta- (or habitat) niche, evolve only slowly. We have quantified traits that determine within-habitat alpha diversity (alpha niches) in two communities in which species segregate on hydrological gradients. Molecular phylogenetic analysis of these data shows practically no evidence of a correlation between the ecological and evolutionary distances separating species, indicating that hydrological alpha niches are evolutionarily labile. We propose that contrasting patterns of evolutionary conservatism for alpha- and beta-niches is a general phenomenon necessitated by the hierarchical filtering of species during community assembly. This determines that species must have similar beta niches in order to occupy the same habitat, but different alpha niches in order to coexist.

Phylogeny and the hierarchical organization of plant diversity.

R. H. Whittaker's idea that plant diversity can be divided into a hierarchy of spatial components from alpha at the within-habitat scale through beta for the turnover of species between habitats to gamma along regional gradients implies the underlying existence of alpha, beta, and gamma niches. We explore the hypothesis that the evolution of alpha, beta, and gamma niches is also hierarchical, with traits that define the alpha niche being labile, while those defining beta and gamma niches are conservative. At the alpha level we find support for the hypothesis in the lack of close significant phylogenetic relationship between meadow species that have similar alpha niches. In a second test, alpha niche overlap based on a variety of traits is compared between congeners and noncongeners in several communities; here, too, there is no evidence of a correlation between alpha niche and phylogeny. To test whether beta and gamma niches evolve conservatively, we reconstructed the evolution of relevant traits on evolutionary trees for 14 different clades. Tests against null models revealed a number of instances, including some in island radiations, in which habitat (beta niche) and elevational maximum (an aspect of the gamma niche) showed evolutionary conservatism.

Crowdsourcing the identification of organisms: A case-study of iSpot.

Accurate species identification is fundamental to biodiversity science, but the natural history skills required for this are neglected in formal education at all levels. In this paper we describe how the web application ispotnature.org and its sister site ispot.org.za (collectively, "iSpot") are helping to solve this problem by combining learning technology with crowdsourcing to connect beginners with experts. Over 94% of observations submitted to iSpot receive a determination. External checking of a sample of 3,287 iSpot records verified > 92% of them. To mid 2014, iSpot crowdsourced the identification of 30,000 taxa (>80% at species level) in > 390,000 observations with a global community numbering > 42,000 registered participants. More than half the observations on ispotnature.org were named within an hour of submission. iSpot uses a unique, 9-dimensional reputation system to motivate and reward participants and to verify determinations. Taxon-specific reputation points are earned when a participant proposes an identification that achieves agreement from other participants, weighted by the agreers' own reputation scores for the taxon. This system is able to discriminate effectively between competing determinations when two or more are proposed for the same observation. In 57% of such cases the reputation system improved the accuracy of the determination, while in the remainder it either improved precision (e.g. by adding a species name to a genus) or revealed false precision, for example where a determination to species level was not supported by the available evidence. We propose that the success of iSpot arises from the structure of its social network that efficiently connects beginners and experts, overcoming the social as well as geographic barriers that normally separate the two.

The Demographic Cost of Reproduction and Its Consequences in Balsam Fir (Abies balsamea).

It is an axiom of life-history theory that reproduction involves age-specific costs in terms of survival or future reproduction. The measurement of costs of reproduction in plants is difficult, and few field studies have measured these costs in terms of fitness or demographic components, thus creating a hiatus between theory and data. In this article, we describe methods for overcoming the problem, illustrated by a field study of balsam fir. We used serial correlation and a permutation test to detect growth costs of reproduction and show how these translate into demographic costs when relative tree size (and therefore growth) is critical to survival. Using chronosequences, we reconstructed the age- and size-specific dynamics of a subalpine population of Abies balsamea. A matrix model describing these dynamics was then used to estimate age- and size-specific probabilities of future survival to maturity ([Formula: see text]). By using a regression model of the relationship between tree size, age, and [Formula: see text], we were able to estimate the maximum age-specific demographic cost of reproduction for trees of all ages. The shape of the age-specific cost curve for A. balsamea may explain why, contrary to a previously published hypothesis, age at first reproduction in A. balsamea does not vary between wave-regenerating and normal populations.

Citizen science reveals unexpected continental-scale evolutionary change in a model organism.

Organisms provide some of the most sensitive indicators of climate change and evolutionary responses are becoming apparent in species with short generation times. Large datasets on genetic polymorphism that can provide an historical benchmark against which to test for recent evolutionary responses are very rare, but an exception is found in the brown-lipped banded snail (Cepaea nemoralis). This species is sensitive to its thermal environment and exhibits several polymorphisms of shell colour and banding pattern affecting shell albedo in the majority of populations within its native range in Europe. We tested for evolutionary changes in shell albedo that might have been driven by the warming of the climate in Europe over the last half century by compiling an historical dataset for 6,515 native populations of C. nemoralis and comparing this with new data on nearly 3,000 populations. The new data were sampled mainly in 2009 through the Evolution MegaLab, a citizen science project that engaged thousands of volunteers in 15 countries throughout Europe in the biggest such exercise ever undertaken. A known geographic cline in the frequency of the colour phenotype with the highest albedo (yellow) was shown to have persisted and a difference in colour frequency between woodland and more open habitats was confirmed, but there was no general increase in the frequency of yellow shells. This may have been because snails adapted to a warming climate through behavioural thermoregulation. By contrast, we detected an unexpected decrease in the frequency of Unbanded shells and an increase in the Mid-banded morph. Neither of these evolutionary changes appears to be a direct response to climate change, indicating that the influence of other selective agents, possibly related to changing predation pressure and habitat change with effects on micro-climate.