bluuebunny/crossref_metadata_2025_split huggingface dataset:
NaOH‐extractable organic matter of andic soils from Galicia (NW Spain) under different land use regimes: a pyrolysis GC/MS study
Authors: Verde J. R. , Buurman P. , Martínez‐Cortizas A. , Macías F. , Camps Arbestain M. 
Published: November 2008

SummaryThe objective of this study was to determine to what extent the attenuation or loss of andic soil properties caused by land use change – from forest (FOR, average C content 118.2 ± 23.7 g kg−1) to agricultural land (AGR, average C content 55.7 ± 16.7 g kg−1) use – is reflected in soil organic matter (SOM) at the molecular level. For this, NaOH‐extractable SOM of A horizons from 17 soils developed on amphibolitic parent material in NW Spain was studied by pyrolysis gas chromatography spectrometry (Py‐GC/MS). We also included two buried andic A horizons (PAL, 2200 cal yr BP in age) on the same parent material, as a reference for the molecular composition of SOM from soils without recent litter additions. Organic matter of PAL soils had a composition largely different from that of superficial soils (FOR and AGR), with an important relative contribution of microbial polysaccharides and N‐compounds, and an absence of compounds that characterize fresh plant litter (e.g. lignins). In the superficial soils, the relative contribution of lignin‐derived compounds was greater in AGR than in FOR soils. Differences were also observed in the relative contribution of aliphatic compounds, FOR soils being enriched in this type of components compared with AGR soils. The results indicated that land use change from FOR to AGR, which was accompanied by a decrease in total SOM, resulted in an enrichment in primary SOM. The smaller relative abundance of primary SOM derivatives in andic FOR soils indicates that these compounds were quickly degraded in Andisols.
A 10‐year study of phosphorus balances and the impact of grazed grassland on total P redistribution within the soil profile
Authors: Watson C. J. , Matthews D. I. 
Published: November 2008

SummaryPhosphorus (P) inputs (wet deposition and fertilizer P) and outputs (animal product and drainflow) were studied on reseeded grazed grassland swards receiving different nitrogen (N) inputs (100–500 kg N ha−1 year−1) for 10 years (March 1989–February 1999), at an experimental site in Northern Ireland. All plots received the same maintenance application of P fertilizer (8.5 kg P ha−1 year−1) to meet grass requirements, to minimize the P surplus and to quantify the impact on P losses to land drainage water. The annual flow weighted mean total P concentrations in drainflow ranged from 187 to 273 μg P litre−1and were well above the concentrations believed to trigger eutrophication. Annual total P lost to drainage water ranged from 0.28 to 1.73 kg P ha−1, but was unaffected by N input. As the average annual P balance was zero, there was no significant change in total P in the top 15 cm of soil. However, there was a highly significant redistribution of P to the soil surface from the 10–15 cm depth, possibly as a result of root acquisition and earthworm activity. Total P in the top 5 cm of soil increased from 0.85 g kg−1to 1.04 g kg−1, over the 10 years of the study, despite there being no net P input. This P accumulation in the top few cm of soil is likely to exacerbate P losses in overland flow and make improvements in water quality difficult to achieve.
Micromorphological evidence of black carbon in colluvial soils from NW Spain
Authors: Kaal J. , Van Mourik J. M. 
Published: November 2008

SummaryBiomass burning produces a residue called black carbon (BC). Black C is generally considered to be highly resistant against biodegradation and has a potential role in the global C cycle, but is difficult to identify and quantify when subjected to prolonged degradation in terrestrial sediments. The colluvial soils from Campo Lameiro (NW Spain), also known as ‘Atlantic rankers’, are rich in organic matter (up to 140 g C kg−1 soil). A micromorphological study was undertaken to test the hypothesis that a large proportion of the organic matter was derived from BC formed during Holocene wildfires (up to > 6000 years ago).As roughly estimated from image analysis of 12 thin sections, the volumetric BC contribution ranged between 10 and 60% (26% on average) of the organic matter. This is a conservative estimate as additional morphologically unrecognizable BC was present in the microgranular matrix of coalesced excrement. We conclude that (i) currently unknown quantities of BC are stored in Atlantic rankers and (ii) analysis of thin sections is an effective tool to identify BC.
The behaviour of soil process models of ammonia volatilization at contrasting spatial scales
Authors: Corstanje R. , Kirk G. J. D , Lark R. M. 
Published: November 2008

SummaryProcess models are commonly used in soil science to obtain predictions at a spatial scale that is different from the scale at which the model was developed, or the scale at which information on model inputs is available. When this happens, the model and its inputs require aggregation or disaggregation to the application scale, and this is a complex problem. Furthermore, the validity of the aggregated model predictions depends on whether the model describes the key processes that determine the process outcome at the target scale. Different models may therefore be required at different spatial scales. In this paper we develop a diagnostic framework which allows us to judge whether a model is appropriate for use at one or more spatial scales both with respect to the prediction of variations at those scale and in the requirement for disaggregation of the inputs. We show that spatially nested analysis of the covariance of predictions with measured process outcomes is an efficient way to do this. This is applied to models of the processes that lead to ammonia volatilization from soil after the application of urea.We identify the component correlations at different scales of a nested scheme as the diagnostic with which to evaluate model behaviour. These correlations show how well the model emulates components of spatial variation of the target process at the scales of the sampling scheme. Aggregate correlations were identified as the most pertinent to evaluate models for prediction at particular scales since they measure how well aggregated predictions at some scale correlate with aggregated values of the measured outcome. There are two circumstances under which models are used to make predictions. In the first case only the model is used to predict, and the most useful diagnostic is the concordance aggregate correlation. In the second case model predictions are assimilated with observations which should correct bias in the prediction, and errors in the variance; the aggregate correlations would be the most suitable diagnostic.
Spatial variation of ammonia volatilization from soil and its scale‐dependent correlation with soil properties
Authors: Corstanje R. , Kirk G. J. D. , Pawlett M. , Read R. , Lark R. M. 
Published: November 2008

SummaryQuantitative predictions of ammonia volatilization from soil are useful to environmental managers and policy makers and empirical models have been used with some success. Spatial analysis of the soil properties and their relationship to the ammonia volatilization process is important as predictions will be required at disparate scales from the field to the catchment and beyond. These relationships are known to change across scales and this may affect the performance of an empirical model. This study is concerned with the variation of ammonia volatilization and some controlling soil properties: bulk density, volumetric water content, pH, CEC, soil pH buffer power, and urease activity, over distances of 2, 50, 500, and >2000 m. We sampled a 16 km × 16 km region in eastern England and analyzed the results by a nested analysis of (co)variance, from which variance components and correlations for each scale were obtained. The overall correlations between ammonia volatilization and the soil properties were generally weak: –0.09 for bulk density, 0.04 for volumetric water content, –0.22 for CEC, –0.08 for urease activity, –0.22 for pH and 0.18 for the soil pH buffer power. Variation in ammonia volatilization was scale‐dependent, with substantial variance components at the 2‐ and 500‐m scales. The results from the analysis of covariance show that the relationships between ammonia volatilization and soil properties are complex. At the >2000 m scale, ammonia volatilization was strongly correlated with pH (–0.82) and CEC (–0.55), which is probably the result of differences in parent material. We also observed weaker correlations at the 500‐m scale with bulk density (–0.61), volumetric water content (0.48), urease activity (–0.42), pH (–0.55) and soil pH buffer power (0.38). Nested analysis showed that overall correlations may mask relationships at scales of interest and the effect of soil variables on these soil processes is scale‐dependent.
Exploring the relationship between sampling efficiency and short‐range endemism for groundwater fauna in the Pilbara region, Western Australia
Authors: EBERHARD STEFAN M. , HALSE STUART A. , WILLIAMS MATTHEW R. , SCANLON MICHAEL D. , COCKING JAMES , BARRON HARLEY J. 
Published: November 2008

Summary1. Identifying the existence of short or narrow range endemic species is an important issue when planning for conservation of groundwater fauna in the face of threats to groundwater quantity and quality.2. Fourteen bores were sampled six times over 3 or 4 years to assess the reliability of net‐hauling sampling in broad‐scale survey to collect the groundwater fauna present at a site and to identify short‐range endemic (SRE) species.3. Species accumulation curves suggested that one sample from a bore collected 23% and 46% of species occurring in low and high abundance, respectively, and two samples collected 38% and 65% of such species. False‐negative rates provided a slightly higher estimate of the collection probability of species with low abundances.4. The frequent failure to collect species present at a site means that some apparent short‐range endemism was probably an artefact of low sampling effort. Nevertheless, as is typical for subterranean fauna, a high proportion of the known species in the Pilbara region appeared to be SREs. About 55% had probable ranges <10 000 km2, the criterion proposed byHarvey (2002)for short‐range endemism.5. Consideration of species occurrence patterns, natural barriers and the scale of most disturbances suggest that 1000 km2is a more satisfactory threshold for short‐range endemism than 10 000 km2but, as the threshold is reduced, more intensive sampling is required to determine whether a species qualifies as an SRE.6. Extrapolation of the results of regional sampling suggested the Pilbara contains about 500–550 species of groundwater fauna, with the density of species being relatively uniform across the region. Attempts to use a T‐S curve approach (sensuUgland & Gray, 2004) highlighted the lack of information about within‐population dispersal of these species and the area of an aquifer that is effectively sampled by a bore.
Crassulacean acid metabolism contributes significantly to the in situ carbon budget in a population of the invasive aquatic macrophyte Crassula helmsii
Authors: KLAVSEN SIGNE KOCH , MABERLY STEPHEN C. 
Published: November 2008

Summary1. The ecophysiological significance of Crassulacean acid metabolism (CAM) in the invasive aquatic macrophyte Crassula helmsii was studied in an English soft‐water lake. The extent and the contribution of CAM to the carbon budget was examined in spring (April) and summer (July) along a depth gradient (0.5–2.2 m), covering the growth range of C. helmsii in the lake.2. Significant in situ CAM activity (30–80 meq kg−1 FW) was present in all specimens, although it decreased with depth and hence correlated with the decline in photon irradiance. Potential CAM activity (60–161 meq kg−1 FW), measured after exposure to low concentrations of CO2 in the day and high concentrations at night, were on average 2.7‐times greater than in situ CAM activity. Overall CAM activity increased from April to July, which is consistent with higher potential carbon limitation caused by increased temperature and light availability.3. CAM activity in C. helmsii appeared to be carbon‐limited at night because night‐time carbon‐fixation increased at raised, compared to ambient, concentrations of CO2.4. The high in situ CAM activity in C. helmsii was reflected in the contribution of CAM to the total carbon budget which, independent of depth and season, ranged from 18% to 42%. The amount of CO2 taken up in the night via CAM was 0.74 to 2.94 times the amount of CO2 lost in respiration, thus emphasizing the importance of CAM in refixation of potentially lost respiratory CO2.5. The onset of decarboxylation in the morning appeared to be under circadian control as there was a delay of up to 5.5 h between the start of the light period and a decline in cell acidity level.6. There was little variation in δ13C content (−21.69 to 23.49‰) with season or depth suggesting, along with the estimated contribution to the carbon‐budget, that CAM is important for the whole population of C. helmsii. CAM may confer a competitive advantage in relation to growth, which may be one of the reasons for the invasiveness of this species.
Waterborne metals impair inducible defences in Daphnia pulex: morphology, life‐history traits and encounters with predators
Authors: MIRZA R. S. , PYLE G. G. 
Published: November 2008

Summary1. Inducible defences may be temporary and favoured where predation is intermittent and have been demonstrated in several invertebrates and vertebrates when prey detect chemical cues (kairomones) released by predators. Daphnia pulex (a water flea) exposed to Chaoborus (midge larvae) kairomones produce small neckteeth on the dorsal surface of the head as a defence against this gape‐limited predator and survive better in the presence of Chaoborus. Recent studies have shown that waterborne copper (Cu) impairs the induction of neckteeth which could lead to lower survival.2. Here, we examined the effects of Cu on morphological changes and shifts in life‐history traits in D. pulex exposed to kairomone from Chaoborus americanus. We exposed D. pulex mothers to chemical cues of C. americanus fed on either D. pulex neonates or on brine shrimp Artemia salina, the same Chaoborus cues combined with an environmentally relevant concentration of copper (10 μg L−1), or dechlorinated tap water. We examined several morphological characteristics of neonates and life‐historical characteristics of adults as well as assessing survival of neonates by staging encounters with predators.3. Neonates from mothers exposed to kairomone plus copper had fewer and shorter neckteeth than neonates from mothers exposed to kairomone alone. Moreover, neonates exposed to Cu had lower survival during encounters with predators than neonates exposed to kairomone without Cu.4. Adult female Daphnia exposed to kairomones released more neonates within the first 24 h of brood release and emptied their brood pouches quicker than mothers not exposed to kairomones, irrespective of the presence of Cu.5. Impairment by metals of morphological defences in zooplankton could lead to a decline in population density and alter community structure.
Contribution of N2O to the greenhouse gas balance of first‐generation biofuels
Authors: SMEETS EDWARD M. W. , BOUWMAN LEX F. , STEHFEST ELKE , Van VUUREN DETLEF P. , POSTHUMA ADAM 
Published: November 2008

AbstractIn this study, we analyze the impact of fertilizer‐ and manure‐induced N2O emissions due to energy crop production on the reduction of greenhouse gas (GHG) emissions when conventional transportation fuels are replaced by first‐generation biofuels (also taking account of other GHG emissions during the entire life cycle). We calculate the nitrous oxide (N2O) emissions by applying a statistical model that uses spatial data on climate and soil. For the land use that is assumed to be replaced by energy crop production (the ‘reference land‐use system’), we explore a variety of options, the most important of which are cropland for food production, grassland, and natural vegetation. Calculations are also done in the case that emissions due to energy crop production are fully additional and thus no reference is considered. The results are combined with data on other emissions due to biofuels production that are derived from existing studies, resulting in total GHG emission reduction potentials for major biofuels compared with conventional fuels. The results show that N2O emissions can have an important impact on the overall GHG balance of biofuels, though there are large uncertainties. The most important ones are those in the statistical model and the GHG emissions not related to land use. Ethanol produced from sugar cane and sugar beet are relatively robust GHG savers: these biofuels change the GHG emissions by −103% to −60% (sugar cane) and −58% to −17% (sugar beet), compared with conventional transportation fuels and depending on the reference land‐use system that is considered. The use of diesel from palm fruit also results in a relatively constant and substantial change of the GHG emissions by −75% to −39%. For corn and wheat ethanol, the figures are −38% to 11% and −107% to 53%, respectively. Rapeseed diesel changes the GHG emissions by −81% to 72% and soybean diesel by −111% to 44%. Optimized crop management, which involves the use of state‐of‐the‐art agricultural technologies combined with an optimized fertilization regime and the use of nitrification inhibitors, can reduce N2O emissions substantially and change the GHG emissions by up to −135 percent points (pp) compared with conventional management. However, the uncertainties in the statistical N2O emission model and in the data on non‐land‐use GHG emissions due to biofuels production are large; they can change the GHG emission reduction by between −152 and 87 pp.
Forest–flood relation still tenuous – comment on ‘Global evidence that deforestation amplifies flood risk and severity in the developing world’ by C. J. A. Bradshaw, N.S. Sodi, K. S.‐H. Peh and B.W. Brook
Authors: Van DIJK ALBERT I. J. M. , Van NOORDWIJK MEINE , CALDER IAN R. , BRUIJNZEEL SAMPURNO L. A. , SCHELLEKENS JAAP , CHAPPELL NICK A. 
Published: November 2008

AbstractIn a recent paper in this journal, Bradshaw and colleagues analyse country statistics on flood characteristics, land cover and land cover change, and conclude that deforestation amplifies flood risk and severity in the developing world. The study addresses an important and long‐standing question, but we identify important flaws. Principal among these are difficulties in interpreting country statistics and the correlation between population and floods. We review current knowledge, which suggests that the removal of trees does not affect large flood events, although associated landscape changes can under some circumstances. Reanalysis of the data analysed by Bradshaw and colleagues shows that population density alone already explains up to 83% of the variation in reported flood occurrences, considerably more than forest cover or deforestation (<10%). Feasible explanations for this statistical finding – whether spurious or causative – are not difficult to conceive. We, therefore, consider the conclusion of Bradshaw and colleagues to be unsupported. However, their study is a valuable first step to show how these or similar flood data might be used to further explore the relationship between land cover and flooding.
Regional analysis of the impacts of climate change on cheatgrass invasion shows potential risk and opportunity
Authors: BRADLEY BETHANY A. 
Published: November 2008

AbstractInteractions between climate change and non‐native invasive species may combine to increase invasion risk to native ecosystems. Changing climate creates risk as new terrain becomes climatically suitable for invasion. However, climate change may also create opportunities for ecosystem restoration on invaded lands that become climatically unsuitable for invasive species. Here, I develop a bioclimatic envelope model for cheatgrass (Bromus tectorum), a non‐native invasive grass in the western US, based on its invaded distribution. The bioclimatic envelope model is based on the Mahalanobis distance using the climate variables that best constrain the species' distribution. Of the precipitation and temperature variables measured, the best predictors of cheatgrass are summer, annual, and spring precipitation, followed by winter temperature. I perform a sensitivity analysis on potential cheatgrass distributions using the projections of 10 commonly used atmosphere–ocean general circulation models (AOGCMs) for 2100. The AOGCM projections for precipitation vary considerably, increasing uncertainty in the assessment of invasion risk. Decreased precipitation, particularly in the summer, causes an expansion of suitable land area by up to 45%, elevating invasion risk in parts of Montana, Wyoming, Utah, and Colorado. Conversely, increased precipitation reduces habitat by as much as 70%, decreasing invasion risk. The strong influence of precipitation conditions on this species' distribution suggests that relying on temperature change alone to project future change in plant distributions may be inadequate. A sensitivity analysis provides a framework for identifying key climate variables that may limit invasion, and for assessing invasion risk and restoration opportunities with climate change.
Forest fine‐root production and nitrogen use under elevated CO2: contrasting responses in evergreen and deciduous trees explained by a common principle
Authors: FRANKLIN OSKAR , McMURTRIE ROSS E. , IVERSEN COLLEEN M. , CROUS KRISTINE Y. , FINZI ADRIEN C. , TISSUE DAVID T. , ELLSWORTH DAVID S. , OREN RAM , NORBY RICHARD J. 
Published: November 2008

AbstractDespite the importance of nitrogen (N) limitation of forest carbon (C) sequestration at rising atmospheric CO2concentration, the mechanisms responsible are not well understood. To elucidate the interactive effects of elevated CO2(eCO2) and soil N availability on forest productivity and C allocation, we hypothesized that (1) trees maximize fitness by allocating N and C to maximize their net growth and (2) that N uptake is controlled by soil N availability and root exploration for soil N. We tested this model using data collected in Free‐Air CO2Enrichment sites dominated by evergreen (Pinus taeda; Duke Forest) and deciduous [Liquidambar styraciflua; Oak Ridge National Laboratory (ORNL)] trees. The model explained 80–95% of variation in productivity and N‐uptake data among eCO2, N fertilization and control treatments over 6 years. The model explains why fine‐root production increased, and why N uptake increased despite reduced soil N availability under eCO2at ORNL and Duke. In agreement with observations at other sites, the model predicts that soil N availability reduced below a critical level diminishes all eCO2responses. At Duke, a negative feedback between reduced soil N availability and N uptake prevented progressive reduction in soil N availability at eCO2. At ORNL, soil N availability progressively decreased because it did not trigger reductions in N uptake; N uptake was maintained at ORNL through a large increase in the production of fast turnover fine roots. This implies that species with fast root turnover could be more prone to progressive N limitation of carbon sequestration in woody biomass than species with slow root turnover, such as evergreens. However, longer term data are necessary for a thorough evaluation of this hypothesis. The success of the model suggests that the principle of maximization of net growth to control growth and allocation could serve as a basis for simplification and generalization of larger scale forest and ecosystem models, for example by removing the need to specify parameters for relative foliage/stem/root allocation.