bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of desiccation on native and non‐native molluscs in rivers
Authors: Collas Frank P. L. , Koopman K. Remon , Hendriks A. Jan , van der Velde Gerard , Verbrugge Laura N. H. , Leuven Rob S. E. W. 
Published: October 2013

Summary

Laboratory data on desiccation tolerance of native and non‐native mollusc species were used to derive species sensitivity distributions (SSDs), to predict effects of desiccation on mollusc assemblages in rivers during low discharge events and to prioritise various environmental stressors (i.e. desiccation, temperature and salinity).

The predicted absence and observed absence of mollusc species by desiccation at a specific site were expressed as potentially not occurring fraction (PNOF) and not occurring fraction (NOF) of their regional species pool in the River Rhine.

Calculations of PNOFs for desiccation explained 57% (LT99) and 65% (LT50) of the NOFs of the mollusc species. Sensitivity to desiccation did not differ between native and non‐native mollusc species pools.

Due to differences in frequency of low river discharge events and water level fluctuations, mollusc species in an impounded reach of the River Meuse were less affected by desiccation than in a free‐flowing distributary of the River Rhine.

Earlier calculations of the PNOFs for combined effects of temperature and salinity in the River Rhine explained 22 and 3% of the NOFs of native and non‐native species, respectively, for the period 1988–2003. Accounting for the effects of desiccation, 62 and 80% of the NOFs of the native and non‐native species pool, respectively, were explained, indicating that desiccation during low discharge events was an important stressor in comparison with water temperature or salinity.

Since a relatively high percentage of the NOFs of native species in the River Rhine still remain unexplained, an effort to assess potential effects of other stressors is recommended (e.g. toxic substances or water turbulence caused by commercial shipping).
Increasing conspecific density weakens the ability of intermediate predators to develop induced morphological defences to top predators
Authors: Davenport Jon M. , Chalcraft David R. 
Published: October 2013

SummaryIntraguild predation is common in nature, but it is unclear how species that both compete and eat each other can persist together. One possibility is that intermediate predators possess inducible morphological defences that protect them from top predators while not compromising their ability to compete with top predators.The ability of intermediate predators to develop morphological defences may be compromised in environments with a high density of conspecifics because of reduced resource availability and predation risk due to the saturating functional response of top predators. Furthermore, since morphological defences take time to develop, the type and extent of morphological defences may vary during development.We conducted an experiment to measure the phenotypic responses of an intermediate predator (larvae of the salamanderAmbystoma opacum) to the presence of a caged top predator (larvae of the dragonflyAnaxspp.) throughout ontological development in environments that differed in the density of conspecifics present. We also assessed how intermediate predators, reared in the different environments, differed in their vulnerability to top predators and ability to deplete their food resources.We found thatAnaxinduced morphological defences inA. opacum, but the extent of morphological change declined with the density of conspecifics. Moreover, some morphological traits disappeared, while others appeared just prior toA. opacummetamorphosis. The change inA. opacumphenotype in response toAnaxmadeA. opacumless vulnerable to predation byAnaxbut had no significant effect on the foraging ability ofA. opacum.Our study demonstrates that top predators can induce phenotypes in intermediate predators that reduce their vulnerability to top predators while not compromising their ability to feed on a common prey. An increase in intermediate predator density, however, could diminish the ability of intermediate predators to develop the full suite of morphological defences. The inability to develop the full suite of morphological defences may reduce the probability of persistence with top predators.
Digging deep for diversity: riparian seed bank abundance and species richness in relation to burial depth
Authors: O'Donnell Jessica , Fryirs Kirstie , Leishman Michelle R. 
Published: October 2013

Summary

Soil and sediment seed banks contribute to the diversity of riparian plant communities. In degraded river systems, seed banks represent an important regeneration niche that may contribute to restoration efforts through the establishment of vegetation. The vertical dimension of seed banks has been neglected in river research, despite its importance for the regeneration of vegetation after disturbances such as erosive floods.

We sampled sediment at various depths within three geomorphological features: bars, benches and the floodplain, across four river reaches in the Wollombi subcatchment of New South Wales, Australia. A seedling emergence study was conducted to characterise the abundance and species richness of the germinable seed bank within these sediments. We hypothesised that the vertical distribution of seeds in bars and benches would show no clear pattern, but that bars would have lower propagule counts overall, due to their non‐cohesive sediment and potential for frequent reworking by low‐level flows. The floodplain seed bank, in contrast, would resemble that of terrestrial systems, with propagule abundance decreasing markedly with depth due to infrequent inundation and sediment reworking.

In total, 9456 seedlings emerged, representing 131 different species (83 native and 47 exotic) from 47 families. Propagule abundance and species richness in bar and bench seed banks were highly variable with depth, with the greatest average propagule numbers found at 25–30 cm and 20–25 cm, respectively. In contrast, and as hypothesised, propagule abundance and species richness in the floodplain decreased significantly with depth. Propagule abundance was surprisingly variable in bars, with some displaying extremely high values and others containing no detectable seeds, although overall species richness was significantly lower than in benches and the floodplain.

The vertical distribution of seeds in bars, benches and floodplains may be determined by the proportional influence of hydrochory (seed transport and deposition by water) during deposition events and seed losses, resulting from sediment reworking and erosion, set within the timescales over which they are formed and reworked. Bar seed banks are continually flushed by frequent inundation and reworking, especially at the surface, reducing seed deposition and burial. Abundant seed fall may be provided by local vegetation, however. Diverse seed banks in benches may form through alternating periods of hydrochoric seed deposition along with sediment, augmented during periods of exposure when propagules from the extant vegetation accumulate. Decreases in germinable propagule abundance and species richness with depth in the floodplain may reflect much slower rates of vertical accretion and seed losses due to mortality over time. Finally, we present some implications for the management of riparian vegetation and applications for river restoration.
Global warming enhances sulphide stress in a key seagrass species (NW Mediterranean)
Authors: García Rosa , Holmer Marianne , Duarte Carlos M. , Marbà Núria 
Published: October 2013

AbstractThe build‐up of sulphide concentrations in sediments, resulting from high inputs of organic matter and the mineralization through sulphate reduction, can be lethal to the benthos. Sulphate reduction is temperature dependent, thus global warming may contribute to even higher sulphide concentrations and benthos mortality. The seagrassPosidonia oceanicais very sensitive to sulphide stress. Hence, if concentrations build up with global warming, this key Mediterranean species could be seriously endangered. An 8‐year monitoring of daily seawater temperature, the sulphur isotopic signatures of water (δ34Swater), sediment(δ34SCRS) andP. oceanicaleaf tissue(δ34Sleaves), along with total sulphur in leaves (TSleaves) and annual net population growth along the coast of the Balearic archipelago (Western Mediterranean) allowed us to determine if warming triggersP. oceanicasulphide stress and constrains seagrass survival. From the isotopicSsignatures, we estimated sulphide intrusion into the leaves (Fsulphide) and sulphur incorporation into the leaves from sedimentary sulphides (SSleaves). We observed lowerδ34Sleaves, higherFsulphideandSSleavescoinciding with a 6‐year period when two heat waves were recorded. Warming triggered sulphide stress as evidenced by the negative temperature dependence ofδ34Sleavesand the positive one ofFsulphide,TSleavesandSSleaves. LowerP. oceanicanet population growth rates were directly related to higher contents ofTSleaves. At equivalent annual maximum sea surface water temperature (SSTmax), deep meadows were less affected by sulphide intrusion than shallow ones. Thus, water depth acts as a protecting mechanism against sulphide intrusion. However, water depth would be insufficient to buffer seagrass sulphide stress triggered by Mediterranean seawater summer temperatures projected for the end of the 21st century even under scenarios of moderate greenhouse gas emissions, A1B. Mediterranean warming, therefore, is expected to enhanceP. oceanicasulphide stress, and thus compromise the survival of this key habitat along its entire depth distribution range.
Separating direct and indirect effects of global change: a population dynamic modeling approach using readily available field data
Authors: Farrer Emily C. , Ashton Isabel W. , Knape Jonas , Suding Katharine N. 
Published: October 2013

AbstractTwo sources of complexity make predicting plant community response to global change particularly challenging. First, realistic global change scenarios involve multiple drivers of environmental change that can interact with one another to produce non‐additive effects. Second, in addition to these direct effects, global change drivers can indirectly affect plants by modifying species interactions. In order to tackle both of these challenges, we propose a novel population modeling approach, requiring only measurements of abundance and climate over time. To demonstrate the applicability of this approach, we model population dynamics of eight abundant plant species in a multifactorial global change experiment in alpine tundra where we manipulated nitrogen, precipitation, and temperature over 7 years. We test whether indirect and interactive effects are important to population dynamics and whether explicitly incorporating species interactions can change predictions when models are forecast under future climate change scenarios. For three of the eight species, population dynamics were best explained by direct effect models, for one species neither direct nor indirect effects were important, and for the other four species indirect effects mattered. Overall, global change had negative effects on species population growth, although species responded to different global change drivers, and single‐factor effects were slightly more common than interactive direct effects. When the fitted population dynamic models were extrapolated under changing climatic conditions to the end of the century, forecasts of community dynamics and diversity loss were largely similar using direct effect models that do not explicitly incorporate species interactions or best‐fit models; however, inclusion of species interactions was important in refining the predictions for two of the species. The modeling approach proposed here is a powerful way of analyzing readily available datasets which should be added to our toolbox to tease apart complex drivers of global change.
The seasonal timing of warming that controls onset of the growing season
Authors: Clark James S. , Melillo Jerry , Mohan Jacqueline , Salk Carl 
Published: October 2013

AbstractForecasting how global warming will affect onset of the growing season is essential for predicting terrestrial productivity, but suffers from conflicting evidence. We show that accurate estimates require ways to connect discrete observations of changing tree status (e.g., pre‐ vs. post budbreak) with continuous responses to fluctuating temperatures. By coherently synthesizing discrete observations with continuous responses to temperature variation, we accurately quantify how increasing temperature variation accelerates onset of growth. Application to warming experiments at two latitudes demonstrates that maximum responses to warming are concentrated in late winter, weeks ahead of the main budbreak period. Given that warming will not occur uniformly over the year, knowledge of when temperature variation has the most impact can guide prediction. Responses are large and heterogeneous, yet predictable. The approach has immediate application to forecasting effects of warming on growing season length, requiring only information that is readily available from weather stations and generated in climate models.
Replicated throughfall exclusion experiment in an Indonesian perhumid rainforest: wood production, litter fall and fine root growth under simulated drought
Authors: Moser Gerald , Schuldt Bernhard , Hertel Dietrich , Horna Viviana , Coners Heinz , Barus Henry , Leuschner Christoph 
Published: October 2013

AbstractClimate change scenarios predict increases in the frequency and duration of ENSO‐related droughts for parts of South‐East Asia until the end of this century exposing the remaining rainforests to increasing drought risk. A pan‐tropical review of recorded drought‐related tree mortalities in more than 100 monitoring plots before, during and after drought events suggested a higher drought‐vulnerability of trees in South‐East Asian than in Amazonian forests. Here, we present the results of a replicated (n = 3 plots) throughfall exclusion experiment in a perhumid tropical rainforest in Sulawesi, Indonesia. In this first large‐scale roof experiment outside semihumid eastern Amazonia, 60% of the throughfall was displaced during the first 8 months and 80% during the subsequent 17 months, exposing the forest to severe soil desiccation for about 17 months. In the experiment's second year, wood production decreased on average by 40% with largely different responses of the tree families (ranging from −100 to +100% change). Most sensitive were trees with high radial growth rates under moist conditions. In contrast, tree height was only a secondary factor and wood specific gravity had no influence on growth sensitivity. Fine root biomass was reduced by 35% after 25 months of soil desiccation while fine root necromass increased by 250% indicating elevated fine root mortality. Cumulative aboveground litter production was not significantly reduced in this period. The trees from this Indonesian perhumid rainforest revealed similar responses of wood and litter production and root dynamics as those in two semihumid Amazonian forests subjected to experimental drought. We conclude that trees from paleo‐ or neotropical forests growing in semihumid or perhumid climates may not differ systematically in their growth sensitivity and vitality under sublethal drought stress. Drought vulnerability may depend more on stem cambial activity in moist periods than on tree height or wood specific gravity.
Elevation‐induced climate change as a dominant factor causing the late Miocene C4 plant expansion in the Himalayan foreland
Authors: Wu Haibin , Guo Zhengtang , Guiot Joël , Hatté Christine , Peng Changhui , Yu Yanyan , Ge Junyi , Li Qin , Sun Aizhi , Zhao Deai 
Published: October 2013

AbstractDuring the late Miocene, a dramatic global expansion of C4 plant distribution occurred with broad spatial and temporal variations. Although the event is well documented, whether subsequent expansions were caused by a decreased atmospheric CO2 concentration or climate change is a contentious issue. In this study, we used an improved inverse vegetation modeling approach that accounts for the physiological responses of C3 and C4 plants to quantitatively reconstruct the paleoclimate in the Siwalik of Nepal based on pollen and carbon isotope data. We also studied the sensitivity of the C3 and C4 plants to changes in the climate and the atmospheric CO2 concentration. We suggest that the expansion of the C4 plant distribution during the late Miocene may have been primarily triggered by regional aridification and temperature increases. The expansion was unlikely caused by reduced CO2 levels alone. Our findings suggest that this abrupt ecological shift mainly resulted from climate changes related to the decreased elevation of the Himalayan foreland.
Biochar amendment to soils with contrasting organic matter level: effects on N mineralization and biological soil properties
Authors: Ameloot Nele , Sleutel Steven , Das K. C. , Kanagaratnam Jegajeevagan , de Neve Stefaan 
Published: October 2013

AbstractFour biochar types, produced by slow pyrolysis of poultry litter (PL) and pine chips (P) at 400 or 500 °C, were added to two adjacent soils with contrasting soil organic matter (SOM) content (8.9 vs. 16.1 g C kg−1). The N mineralization rate was determined during 14‐week incubations and assessments were made of the microbial biomass C, dehydrogenase activity, and the microbial community structure (PLFA‐extraction). The addition of PL biochars increased the net N mineralization (i.e., compared to the control treatment) in both soils, while for treatments with P biochars net N immobilization was observed in both soils. Increasing the pyrolysis temperature of both feedstock types led to a decrease in net N mineralization. The ratio of Bacterial to Fungal PLFA biomarkers also increased with addition of biochars, and particularly in the case of the 500 °C biochars. Next to feedstock type and pyrolysis temperature, SOM content clearly affected the assessed soil biological parameters, viz. net N mineralization or immobilization, MBC and dehydrogenase activity were all greater in the H soil. This might be explained by an increased chance of physical contact between the microbial community activated by SOM mineralization upon incubation and discrete biochar particles. However, when considering the H soil's double C and N content, these responses were disproportionally small, which may be partly due to the L soil's, somewhat more labile SOM. Nonetheless, increasing SOM content and microbial biomass and activity generally appears to result in greater mineralization of biochar. Additionally, higher N mineralization after PL addition to the H soil with lower pH than the L soil can be due to the liming effect of the PL biochars.
Effects of harvest frequency and biosolids application on switchgrass yield, feedstock quality, and theoretical ethanol yield
Authors: Liu Xiao‐Jun Allen , Fike John H. , Galbraith John M. , Fike Wonae B. , Parrish David J. , Evanylo Gregory K. , Strahm Brian D. 
Published: October 2013

AbstractSustainable development of a bioenergy industry will require low‐cost, high‐yielding biomass feedstock of desirable quality. Switchgrass (Panicum virgatum L.) is one of the primary feedstock candidates in North America, but the potential to grow this biomass crop using fertility from biosolids has not been fully explored. The objective of this study was to examine the effects of harvest frequency and biosolids application on switchgrass in Virginia, USA. ‘Cave‐in‐Rock’ switchgrass from well‐established plots was cut once (November) or twice (July and November) per year between 2010 and 2012. Class A biosolids were applied once at rates of 0, 153, 306, and 459 kg N ha−1 in May 2010. Biomass yield, neutral and acid detergent fiber, cellulose, hemicellulose, lignin, and ash were determined. Theoretical ethanol potential (TEP, l ethanol Mg−1 biomass) and yield (TEY, l ethanol ha−1) were calculated based on cellulose and hemicellulose concentrations. Cutting twice per season produced greater biomass yields than one cutting (11.7 vs. 9.8 Mg ha−1) in 2011, but no differences were observed in other years. Cutting once produced feedstock with greater TEP (478 vs. 438 l Mg−1), but no differences in TEY between cutting frequencies. Biosolids applied at 153, 306, and 459 kg N ha−1 increased biomass yields by 25%, 37%, and 46%, and TEY by 25%, 34%, and 42%, respectively. Biosolids had inconsistent effects on feedstock quality and TEP. A single, end‐of‐season harvest likely will be preferred based on apparent advantages in feedstock quality. Biosolids can serve as an effective alternative to N fertilizer in switchgrass‐to‐energy systems.
Influence of intraspecific competition on the distribution of a wide‐ranging, non‐territorial carnivore
Authors: Pilfold Nicholas W. , Derocher Andrew E. , Richardson Evan 
Published: October 2013

AbstractAimIt is generally held that the dominant competitors in a population will occupy high‐quality habitat while forcing subordinates into lower‐quality habitats through interference competition. We examined the distribution of a non‐territorial apex carnivore relative to foraging habitat to assess the effect of two types of interference: competitive asymmetries in predatory ability and conspecific predation risk.LocationBeaufort Sea, Canada.MethodsThe quality of foraging habitat was modelled using resource selection functions to relate the locations of seals killed by polar bears (Ursus maritimus) to attributes of the sea ice. We used estimated seal biomass as a sample weight to reflect the energetic return of different sizes of kills. To test the effect of sample weighting, locations at which polar bears were captured were used to compare habitat quality modelled with kills weighted equally and kills weighted by their biomass. The distributions of different demographic classes of polar bears were then compared with the general predictions of unequal‐competitor models.ResultsPolar bear distribution was correlated with the quality of the foraging habitat as determined by the kill biomass model (rs = 0.90, P = 0.04), but not in the unweighted design (P = 0.75). No difference was detected in use of the highest‐quality foraging habitat by subadults and adults. Females with cubs‐of‐the‐year used lower‐quality foraging habitat relative to the rest of the population.Main conclusionsWeighting the habitat model with biologically relevant information improved its fit to species distribution, and suggested that density of use alone was insufficient to define habitat quality. Intraspecific competition had a varying influence on the distribution: unequal competitors coexisted, while the avoidance of conspecific predation risk resulted in semi‐truncation.
A meta‐analysis comparing standard polyethylene and oxygen barrier film in terms of losses during storage and aerobic stability of silage
Authors: Wilkinson J. M. , Fenlon J. S. 
Published: October 2013

AbstractA meta‐analysis was undertaken of 51 comparisons of standard polyethylene film with oxygen barrier (OB) film in covering systems for bunker silos, unwalled clamp silos and bales. Mean losses of DM or OM during storage from the top 10 to 60 cm of bunker and clamp silos were 195 g kg−1 for standard film and 114 g kg−1 for OB film systems (41 sets of data, P < 0·001), while mean total losses of DM from baled silage were 76·8 g kg−1 for standard film and 45·6 g kg−1 for OB film systems (10 sets of data, P < 0·001). Top surface silage judged subjectively to be inedible was 107 and 29·6 g kg−1 for standard film and OB film systems respectively (5 sets of data, P = 0·02). Aerobic stability was 75 h for silage stored under standard film system and 135 h for silage stored under OB film system (11 sets of data, P = 0·001). It is concluded that the OB film system reduces losses from the outer layers of silos and from bales and increases the aerobic stability of silage in the outer layers of silos.