Tree age,site and climate controls on tree ring cellulose δ18O: A case study on oak trees from south-western France

A main concern of dendroclimatic reconstruction is to distinguish in the tree ring proxy the influence of the climate variables of interest from other controlling factors. In order to investigate age, site and climate controls on tree ring width and cellulose δ¹⁸O, measurements have been performed in nearby groups of young (145 years old) and older (310–405 years old) oak trees in south-western France, covering the period 1860–2010.Within a given site, inter-tree deviations are small, pointing to a common climatic signal. Despite a similar inter-annual variability, the average level of cellulose δ¹⁸O in the young tree group is ∼0.8‰ higher than in the old trees. Such offsets might be caused by different soil properties and differences in the fraction of the source water used by trees from different depths. The δ¹⁸O of water in the top soil layer is directly related to the current growing season precipitation, while deeper water can have a lower and more constant δ¹⁸O. Local cave drip waters at 10 m depth indeed show a constant isotopic composition, which corresponds to pluri-annual mean precipitation.A 2‰ increasing trend is observed in cellulose δ¹⁸O of young trees in the first 30 years of growth, during a period when no trend is visible in older trees. This increase can be quantitatively explained by humidity gradients under the forest canopy, and a changing microclimate around the crown as trees grow higher.While relationships between tree ring width and climate appear complex, the isotopic composition of cellulose is strongly correlated with summer maximum temperature, relative humidity and evapotranspiration (r ≈ 0.70). Weaker correlations (r ≈ 0.40) are identified with precipitation δ¹⁸O from a 15-year long local record and from the REMOiso model output. These results imply that leaf water enrichment has a stronger control on the inter-annual variability of cellulose δ¹⁸O than the δ¹⁸O of precipitation.This study demonstrates the suitability of oak tree ring cellulose δ¹⁸O for reconstructing past summer climate variability in south-western France, provided that the sampling and pooling strategy accounts for the fact that trees from different sites and of different age can introduce non-climatic signals.     

Effects of anticoagulants on stable-isotope values (δ13C and δ15N) of shark blood components

The effects of anticoagulant EDTA and sodium heparin (SH) on stable carbon δ¹³C and nitrogen δ¹⁵N isotopic values of red blood cells (RBC) and blood plasma in juvenile blacktip reef sharks Carcharhinus melanopterus were analysed. Plasma preserved with anticoagulants was not isotopically distinct from plasma stored in no-additive control tubes but RBC δ¹⁵N values exhibited small enrichments when preserved with EDTA and SH. Results suggest EDTA and SH are viable anticoagulants for stable isotopic analyses of blood fractions but further studies are advised to validate results.     

Predicting tree biomass growth in the temperate–boreal ecotone: Is tree size,age, competition,or climate response most important?

As global temperatures rise, variation in annual climate is also changing, with unknown consequences for forest biomes. Growing forests have the ability to capture atmospheric CO₂ and thereby slow rising CO₂ concentrations. Forests’ ongoing ability to sequester C depends on how tree communities respond to changes in climate variation. Much of what we know about tree and forest response to climate variation comes from tree‐ring records. Yet typical tree‐ring datasets and models do not capture the diversity of climate responses that exist within and among trees and species. We address this issue using a model that estimates individual tree response to climate variables while accounting for variation in individuals’ size, age, competitive status, and spatially structured latent covariates. Our model allows for inference about variance within and among species. We quantify how variables influence aboveground biomass growth of individual trees from a representative sample of 15 northern or southern tree species growing in a transition zone between boreal and temperate biomes. Individual trees varied in their growth response to fluctuating mean annual temperature and summer moisture stress. The variation among individuals within a species was wider than mean differences among species. The effects of mean temperature and summer moisture stress interacted, such that warm years produced positive responses to summer moisture availability and cool years produced negative responses. As climate models project significant increases in annual temperatures, growth of species like Acer saccharum, Quercus rubra, and Picea glauca will vary more in response to summer moisture stress than in the past. The magnitude of biomass growth variation in response to annual climate was 92–95% smaller than responses to tree size and age. This means that measuring or predicting the physical structure of current and future forests could tell us more about future C dynamics than growth responses related to climate change alone.     

Effects of tumor necrosis factor and interferon-β on proliferation and epidermal growth factor binding in young and senescent WI-38 cells

Summary Tumor necrosis factor-α (TNF) and various interferons (IFN) have potent cytostatic or cytotoxic effects on a variety of human tumor-derived cell lines. Their effects on normal cells are more controversial. We have examined the effects of TNF and IFN-β on the proliferation of WI-38 cells in a serum-free, growth factor-supplemented medium and in serum-containing medium. These cells respond to the combination of epidermal growth factor (EGF), insulin-like growth factor-I (IGF-I), and dexamethasone by DNA synthesis at a rate and extent equivalent to serum-stimulated cells. TNF has no effect on this growth factor-stimulated proliferation. However, it is stimulatory in serum-containing medium. IFN-β inhibits DNA synthesis 60 to 70% in both young and senescent cells. TNF and IFN-β together have a synergistic effect and completely inhibit growth factor-stimulated DNA synthesis in young cells. No synergism was observed with senescent cells. TNF stimulated an increase in the number of EGF specific binding sites two- to threefold in 24 h in both young and senescent cells. This seems to result from a proportional increase in a very high affinity binding site. IFN-β has little or no effect on EGF binding either alone or in combination with TNF.     

Foliar chemistry and tree ring δ13C of Pinus densiflora in relation to tree growth along a soil pH gradient

Background and aims

Soil acidification is known to be one of the constraints of tree growth; however, it is unclear how it affects tree growth at photosynthesis level (i.e., through affecting stomatal conductance vs. carboxylation rate) during the growth of trees. This paper studied the effects of soil acidification on Pinus densiflora foliar chemistry and tree ring C isotope ratio (¹³C/¹²C, expressed as δ¹³C) and their relationship with tree growth.

Methods

Tree growth (diameter, annual growth ring area, and root biomass), soil chemistry (pH, mineral N, and exchangeable Ca and Al), foliage chemistry (N, Ca/Al, and δ¹³C), and tree ring δ¹³C in P. densiflora stands along a soil pH gradient (from 4.38 to 4.83, n?=?9) in southern Korea were investigated.

Results

Overall, trees with relatively poor growth under more acidic soil conditions (low pH and Ca/Al) had lower values of foliar N concentration and δ¹³C and tree ring δ¹³C, suggesting that restricted N uptake under more acidic soil conditions caused N limitation for photosynthesis, leading to poor tree growth. In addition, relationships between mean annual area increment and carbon isotope discrimination of tree rings at five-yr intervals from 1968 to 2007 revealed that the impact of soil acidification on tree growth became severer during the last 15 yrs as negative correlations between them became significant after 1993.

Conclusions

Reduced N uptake under acidic soil conditions resulted in lower radial growth of P. densiflora via non-stomatal limitation of photosynthesis.     

Reliability of δ13C and δ15N in faeces for reconstructing savanna herbivore diet

We tested the reliability of herbivore faecal δ¹³C and δ¹⁵N values for reconstructing diet through review of an extensive database derived from a 3-year study of ungulates in South Africa's Kruger National Park. Faeces are a useful material for stable isotope studies of diet because they record dietary turnover at very short time scales, and because sampling is non-invasive. However, the validity of faecal isotope proxies may be questioned because they represent only undigested food remains. Results from Kruger Park confirm that free-ranging browsers have faecal δ¹³C consistent with C₃ feeding, grazer faeces are C₄, and mixed-feeder faeces intermediate. Although the respective ranges do not overlap, there is significant variation in faecal δ¹³C of browsers and grazers (～2.0–4.0‰) across space and through time. We demonstrate that most (～70%) of this variation can be ascribed to corresponding patterns of variation in the δ¹³C of C₃ and C₄ plants, respectively, re-enforcing the fidelity of faecal isotope proxies for diet but highlighting a need for mixing models that control for variations in plant δ¹³C in order to achieve accurate diet reconstructions. Predictions for the effects of climate (rainfall) and ecophysiology on ¹⁵N-abundance variations in mammals do not persist in faeces. Rather, faecal δ¹⁵N tracks changes in plant δ¹⁵N, with further fractionation occurring primarily due to variations in dietary protein (reflected by %N). Controlling for these effects, we show that a dual-isotope multiple source mixing model (Isosource) can extend diet reconstructions for African savanna herbivores beyond simplified C₃/C₄ distinctions, although further understanding of variations in mammal δ¹⁵N are needed for greater confidence in this approach.     

Differences in the C age, δC and δO of Holocene tufa and speleothem in the Dinaric Karst

We studied Holocene speleothems and tufa samples collected in numerous caves and rivers in the Dinaric Karst of Croatia, Slovenia, Bosnia and Herzegovina, as well as Serbia and Montenegro. Differences in the formation process of tufa and speleothems are discussed in the context of their isotopic composition (¹⁴C, ¹³C and ¹⁸O), as well as the chemistry of surface water (rivers, lakes) and drip water (in caves). The physical and chemical parameters monitored in the surface water (tufa precipitation) and drip water (speleothem precipitation) show that more stable conditions accompany speleothem rather than tufa formation. This is particularly obvious in the water temperature variations (2-22°C in surface water and 7-12°C in drip water) and in saturation index variation (3-11 in surface water and 1-6 in drip water). The range of ¹⁴C ages recorded by Holocene speleothems (∼12?000 yr) is wider by several thousands years than that of Holocene tufa samples (∼6000 yr). δ¹³C values for tufa samples range from −12‰ to −6‰ and for speleothem samples from −12‰ to +3‰ reflecting higher soil carbon and/or vegetation impact on the process of tufa than on speleothem formation. The differences in δ¹⁸O values of tufa and speleothem samples from different areas reflect different temperature conditions and differing isotopic composition in the water. The study shows that speleothems from the Dinaric Karst can be used as global palaeoclimatic records, whereas tufa records changes in the local palaeoenvironment.     

Influence of gabaculine on growth,chlorophyll synthesis,and δ-aminolevulinic acid synthase activity in Euglena gracilis

Euglena gracilis is capable of forming the heme and chlorophyll precursor δ-aminolevulinic acid (ALA) by two routes: from glutamate via the five-carbon path in the chloroplasts, and by ALA synthase-mediated condensation of succinyl-CoA and glycine, probably in the mitochondrion. 5-Amino-1,3-cyclohexadienyl carboxylic acid (gabaculine), a powerful inhibitor of ALA formation via the five-carbon path, was administered to E. gracilis Klebs strain Z Pringsheim cells growing in the light or dark, and its effects on growth, chlorophyll accumulation and extractable ALA synthase activity were measured. Gabaculine had no effect in vitro on ALA synthase or ALA dehydratase, even at 100 μM. Administration of 100 μM gabaculine to wild-type cells growing in the light slowed growth, inhibited chlorophyll accumulation, and induced an increase in extractable ALA synthase activity. Chlorophyll accumulation in the light was abolished by prior administration of the compound to growing cells for 6 h in the dark, whereas chlorophyll accumulation in cells without gabaculine began immediately after transfer to light. Extractable ALA synthase activity from gabaculine-pretreated dark-grown cells was initially lower than the activity from untreated cells, but it did not undergo a further decline after transfer of the cells to the light, whereas the activity from untreated cells dropped to less than one eighth the dark level after 2 h in the light, and by 4 h had fallen to a level five times lower than that extractable from gabaculine-treated cells. These results suggest that suppression of ALA synthase activity by light in untreated cells is related to light-induced activation of the five-carbon ALA biosynthetic pathway in the plastids, and may result from a contribution by a product of the five-carbon pathway to non-plastid tetrapyrrole pools in the light.     

Soil nitrification and foliar δ15N declined with stand age in trembling aspen and jack pine forests in northern Alberta,Canada

Aims

Seed germination and seedling emergence are vulnerable to water stress in arid environments. When precipitation is low and unpredictable during the early growing season, seeds near the sand surface often suffer from hydration/dehydration during germination. We investigated the responses of seedling emergence and survival of a sand dune grass with high sand stabilization value to amount and frequency of precipitation and depth of burial in sand.

Methods

Effects of amount and frequency of precipitation, burial and hydration/dehydration on seedling emergence of Leymus secalinus, were examined using standard procedures.

Results

Seedling emergence was affected by amount and frequency of monthly precipitation and depth of burial, and it decreased as precipitation frequency decreased with same amount of precipitation. Highest emergence percentage was obtained with 100 or 150 mm precipitation at 1–4 cm depth. Hydration/dehydration treatments decreased germination and increased dormancy percentage. Young seedlings with root lengths of 0–1 mm desiccated up to 30 days revived after rehydration.

Conclusions

Seedling emergence of L. secalinus is adapted to 150 mm monthly precipitation with frequency of 10–30 times per month, 1–4 cm burial depth and dehydration interval of 1–2 days. Alteration of amount and/or frequency of precipitation caused by climate change could markedly affect seedling emergence and population regeneration of this species.     

Patterns of foliar δ15N and their control in Eastern Asian forests

Foliar δ¹⁵N has been used increasingly in research on ecosystem nitrogen (N) cycling, because it can serve as an integrator of ecosystem N cycling and thus has a potential to reveal temporal and spatial patterns of N cycling as well as how the N cycle is altered by disturbances. However, the current understanding on controls of foliar δ¹⁵N is based principally on studies from America, Europe, Australia and Africa. Here we compiled data from 65 forests at 33 sites across East Asia to explore regional patterns and what controls foliar δ¹⁵N by linking it to climate, species composition, soil depth, slope position, N deposition, and soil N availability. In East Asia, foliar δ¹⁵N ranged from ?7.1 to +2.7‰. Mean foliar δ¹⁵N values for tropical, subtropical and temperate forests were all ?3.1‰, which was unexpected. The patterns of foliar δ¹⁵N with precipitation, temperature and altitude were not clear. The variation in foliar δ¹⁵N among species and between different slope positions appeared to be small within a given forest. The δ¹⁵N for both bulk soil N and extractable inorganic N generally increased with soil depth as expected, strengthening the idea that deep-rooted trees may have access to ¹⁵N-enriched N. Different from the positive correlations reported across America and Europe, in East Asia we found that foliar δ¹⁵N decreased with increasing N deposition and did not relate to soil N availability. These discrepancies deserve more research to elucidate the mechanisms by which foliar δ¹⁵N is affected by ecosystem N availability at a regional scale.     

Quaternary record of aridity and mean annual precipitation based on δ15N in ratite and dromornithid eggshells from Lake Eyre, Australia

The cause(s) of the late Pleistocene megafauna extinction on the Australian continent remains largely unresolved. Unraveling climatic forcing mechanisms from direct or indirect human agents of ecosystem alteration has proven to be extremely difficult in Australia due to the lack of (1) well-dated vertebrate fossils and (2) paleo-environmental and -ecological records spanning the past approximately 100 ka when regional climatic conditions are known to have significantly varied. We have examined the nitrogen isotope composition (δ(15)N) of modern emu (Dromaius novaehollandiae) eggshells collected along a precipitation gradient in Australia, along with modern climatological data and dietary δ(15)N values. We then used modern patterns to interpret an approximately 130-ka record of δ(15)N values in extant Dromaius and extinct Genyornis newtoni eggshells from Lake Eyre to obtain a novel mean annual precipitation (MAP) record for central Australia spanning the extinction interval. Our data also provide the first detailed information on the trophic ecology and environmental preferences of two closely related taxa, one extant and one extinct. Dromaius eggshell δ(15)N values show a significant shift to higher values during the Last Glacial Maximum and Holocene, which we interpret to indicate more frequent arid conditions (<200 mm MAP), relative to δ(15)N from samples just prior to the megafauna extinction. Genyornis eggshells had δ(15)N values reflecting wetter nesting conditions overall relative to those of coeval Dromaius, perhaps indicating that Genyornis was more reliant on mesic conditions. Lastly, the Dromaius eggshell record shows a significant decrease in δ(13)C values prior to the extinction, whereas the Genyornis record does not. Neither species showed a concomitant change in δ(15)N prior to the extinction, which suggests that a significant change in vegetation surrounding Lake Eyre occurred prior to an increase in local aridity.     

Rivermouth Alteration of Agricultural Impacts on Consumer Tissue δ15N

Terrestrial agricultural activities strongly influence riverine nitrogen (N) dynamics, which is reflected in the δ¹⁵N of riverine consumer tissues. However, processes within aquatic ecosystems also influence consumer tissue δ¹⁵N. As aquatic processes become more important terrestrial inputs may become a weaker predictor of consumer tissue δ¹⁵N. In a previous study, this terrestrial-consumer tissue δ¹⁵N connection was very strong at river sites, but was disrupted by processes occurring in rivermouths (the ‘rivermouth effect’). This suggested that watershed indicators of N loading might be accurate in riverine settings, but could be inaccurate when considering N loading to the nearshore of large lakes and oceans. In this study, the rivermouth effect was examined on twenty-five sites spread across the Laurentian Great Lakes. Relationships between agriculture and consumer tissue δ¹⁵N occurred in both upstream rivers and at the outlets where rivermouths connect to the nearshore zone, but agriculture explained less variation and had a weaker effect at the outlet. These results suggest that rivermouths may sometimes be significant sources or sinks of N, which would cause N loading estimates to the nearshore zone that are typically made at discharge gages further upstream to be inaccurate. Identifying definitively the controls over the rivermouth effect on N loading (and other nutrients) will require integration of biogeochemical and hydrologic models.     

Origin of carbon in agricultural soil profiles deduced from depth gradients of C:N ratios,carbon fractions, δ13C and δ15N values

Plant and Soil - Agricultural soils in Germany store 2.54 Pg of organic carbon (C). However, information about how and when this C entered the soils is limited. This study illustrates how depth...     

��13C signature of tree rings and radial increment of Fagus sylvatica trees as dependent on tree neighborhood and climate

We conducted dendroecological analyses in 80-year-long tree ring chronologies to detect neighborhood effects (competition intensity, species identity) on the δ¹³C signature of tree rings and radial stem increment of Fagus sylvatica trees growing either in monospecific or mixed patches of a temperate forest. We hypothesized that tree ring δ¹³C is a more sensitive indicator of neighborhood effects and the impact of climate variability on growth than is ring width. We found a closer correlation of summer precipitation to δ¹³C than to ring width. While the ring width showed a decline over the test period (1926–2005), the mean curve of δ¹³C increased until the mid of the 1970s, remained high until about 1990, and markedly decreased thereafter. Possible explanations related to ontogeny and environmental change (‘age effect’ due to canopy closure; elevated atmospheric SO₂ concentrations in the 1960s–1980s) are discussed. Beech target trees surrounded by many allospecific trees had a significantly lower mean δ¹³C in the period 1926–1975 than beech with predominantly or exclusively conspecific neighborhood, possibly indicating a more favorable water supply of beech in diverse stands. Contrary to expectation, trees subject to more intense competition by neighboring trees (measured by Hegyi’s competition index) had lower δ¹³C values in their tree rings, which is thought to reflect denser canopies being linked to increased shading. We conclude that tree ring δ¹³C time series represent combined archives of climate variability, stand history and neighborhood effects on tree physiology and growth that may add valuable information to that obtained from conventional tree ring analysis.     

Quantifying the risk of mis-estimating correlation significance of climate–tree growth relationships

In dendroecology, sampling effort has a strong influence of both regional chronology properties and climate–tree growth relationships assessment. Recent studies evidenced that decreasing sample size leads to a weakening of the bootstrapped correlation coefficients ( ${\text{BCC}}$ BCC ). The present analysis focused on the risk of mis-estimating the significance of population ${\text{BCC}}\,\left( {{\text{BCC}}_{\text{POP}} } \right)$ BCC ( BCC POP ) from a sample of N trees, and then proposed an approach to detect and correct mis-estimations using the properties of the sample. The sample size effect and the limits of the correction were illustrated from 840 individual growth chronologies of Corsican pine (Pinus nigra Arnold ssp. laricio Poiret var. Corsicana) sampled in Western France. The 840 trees were used to assess the population characteristics, and the effect of sampling effort was investigated through a simulation approach based on a resampling procedure of N trees amongst 840 (N ? [5; 50]). Our results evidenced that the risk strongly varied amongst the climatic regressors. The highest risks were evidenced for significant ${\text{BCC}}_{\text{POP}}$ BCC POP , with a percentage of mis-estimation ranging from 25 to 80. On the contrary, small samples allowed providing an reliable estimation of the significance of non-significant ${\text{BCC}}_{\text{POP}}$ BCC POP . To a lesser extent, the risk slightly decreased with increasing N, according to a negative exponential trend. The detection and correction method was found relevant to detect mis-estimation only for significant ${\text{BCC}}_{\text{POP}}$ BCC POP ; otherwise, the ${\text{BCC}}_{\text{POP}}$ BCC POP significance was generally overestimated.     

Effects of high irradiances on photosynthesis,growth and crassulacean acid metabolism in the epiphyteKalanchoö uniflora

Summary Kalancho? uniflora was grown in the glasshouse with and without shading. Chlorophyll content, area/FW ratio and specific leaf area were higher in leaves of shaded as compared to unshaded plants. Light saturation curves and continuous gas exchange measurements showed that the apparent quantum yield and the light-saturated photosynthetic rate were higher in shaded plants. Shaded plants had lower “mesophyll resistances” than unshaded plants, indicating that the different photosynthetic capacities reflected different contents of ribulose biphosphate carboxylase-oxygenase. Highlight treatment of plants grown in the shade resulted in a decreased photosynthetic efficiency, showing that these plants were sensitive to photoinhibition. However, dry matter production was higher in unshaded than in shaded plants. Obviously the difference in irradiance between the two growth regimes did more than offset the differences in photosynthetic efficiency. Applying additional nutrients did not alter the effects of high PFDs. The results are discussed in respect to photosynthetic performence and plant distribution in the epiphytic habitat.     

Effects of transforming growth factor β on growth of human mammary epithelial cells in culture

Summary Normal human mammary epithelial cells (HMEC) from different individual reduction mammoplasty specimens were all growth inhibited, and showed a flattened, elongated morphology in response to human recombinant transforming growth factor β1 (TGFβ). The degree of growth inhibition varied among specimens, but none of the normal HMEC maintained growth in the continued presence of TGFβ. The degree of growth inhibition also varied with cell age in vitro, cells closer to senescence being more sensitive. TGFβ sensitivity was additionally assayed in two established cell lines derived from one of the reduction mammoplasty specimens after exposure to benzo(a)pyrene. Although varying degrees of growth inhibition and morphologic changes were observed in the cell lines, both lines contained populations that maintained active growth in the presence of TGFβ. Subclones of these lines demonstrated a great plasticity in their growth response to TGFβ, with individual clones ranging from strongly growth inhibited to nearly unaffected. These results suggest that multiple factors influence the extent of TGFβ-induced growth effects on both normal and transformed mammary epithelial cells, and that some of these factors may act through epigenetic mechanisms. This work was supported by CA24844 from the National Institutes of Health, Bethesda, MD, and the Office of Energy Research, Office of Health and Environmental Research of the U.S. Department of Energy under contract DE-AC03-76SF00098.     

The influence of weed control on foliar δ<Superscript>15</Superscript>N, δ<Superscript>13</Superscript>C and tree growth in an 8 year-old exotic pine plantation of subtropical Australia

Background and aims

The aim of weed control and fertilization in forest plantations was to increase tree growth by reducing competition for available nutrients and water. However, treatments that influence weed biomass can also have significant impacts on soil carbon (C) and nitrogen (N) cycling which can in turn lead to changes in the dynamics of stable C (δ¹³C) and N (δ¹⁵N) isotope compositions in soils and tree foliage.

Methods

We examined the key C and N cycling processes influenced by routine and luxury weed control and fertilization treatments as reflected by soil and foliar δ¹³C and δ¹⁵N and long-term tree growth in an 8-year old F₁ hybrid pine (Pinus elliottii x P. caribaea) plantation in southeast Queensland, Australia. Weed control treatments varied by treatment frequency and intensity while fertilization treatments varied by the application of N, phosphorus (P), potassium (K) and micronutrients. Different soil and canopy sampling positions were assessed to determine if sampling position enhanced the relationships among soil N transformations and tree N use, water use efficiency and carbon gain under the early establishment silviculture.

Results

Routine weed control was associated with increased weed biomass returned to the soil, compared with luxury weed control. Soil δ¹³C increased at the 0–5 cm soil sampling depth in both the inter-planting (IPR) and planting row (PR) as a result of the routine weed control treatments. In addition, soil δ¹³C was significantly higher as a result of fertilisation treatment in the 0–5 cm soil sampling depth in the PR. Soil δ¹³C was negatively correlated to soil δ¹⁵N at the 0–5 cm soil sampling depth in the IPR. Soil δ¹⁵N increased in the 0–5 and 5–10 cm soil sampling depths in the IPR, as a result of more frequent (luxury) weed control. Foliar δ¹⁵N and tree water use efficiency (WUE) (as indicated by foliar δ¹³C) were positively correlated with tree growth at age 8 years. While relationships between δ¹³C and δ¹⁵N in the soil and foliage varied depending on soil sampling depth and position, and with canopy sampling position where there were consistent relationships between soil δ¹³C (or δ¹⁵N) and foliar δ¹⁵N.

Conclusions

This study demonstrates how early establishment silviculture has important implications for soil C and N cycling and how soil δ¹³C and δ¹⁵N were consistent with changes in soil C cycling and N transformations as a result of weed control treatments, while foliar δ¹⁵N was linked to more rapid N cycling as reflected in the soil δ¹⁵N, which increased tree growth and tree WUE (as reflected by foliar δ¹³C).

     

Are extra-pair young better than within-pair young? A comparison of survival and dominance in alpine marmot

1. In socially monogamous species, females may seek extra-pair copulation to gain genetic benefits. In order to test this 'genetic quality' hypothesis, one must compare the performance of extra-pair young (EPY) and within-pair young (WPY). Such tests, however, are scarce and results published so far are inconclusive. 2. Here, we test the 'genetic quality' hypothesis using multistate capture-recapture models to compare age-specific survival and access to dominance between EPY and WPY in the alpine marmot Marmota marmota, a socially monogamous mammal showing extra-pair paternities. 3. When compared with WPY, survival of EPY was higher by 15%, 10% and 30%, for juveniles, yearlings and 2-year-old individuals, respectively. Survival at older ages did not differ. 4. Survival corresponded to true survival for yearlings and juveniles as dispersal does not occur before 2 years of age in marmots. For older individuals, survival estimates included a mixture of survival and dispersal. The 30% increase of the 2-year-old EPY survival might reflect delayed dispersal rather than high survival of EPY as compared with WPY. 5. WPY and EPY had the same probability (0.28) to access dominance at 2 years of age, but EPY were more successful at older ages than WPY (0.46 vs. 0.10). 6. Both survival and reproductive performance were higher in EPY than in WPY. The fitness advantages of adopting such a mixed mating tactic are thus likely to be high for marmot females. We suggest that obtaining genetic benefits is the main evolutionary force driving extra-pair paternity in alpine marmots.     

Spatial interpolation of N concentrations and δ15N values in the moss Hypnum cupressiforme collected in the forests of Slovenia

Mosses were collected from 103 locations and analyzed for N concentration and δ¹⁵N values. At each location, the samples were collected from two types of site: under the tree canopies and in the adjacent forest openings. A spatial correlation was detected, and ordinary kriging could be applied only to the N in the mosses that were collected in the openings. In contrast, a spatial correlation was not detected for N in the mosses that were collected under the canopies or for the δ¹⁵N of the mosses at either type of site. For those, the spatial interpolation was calculated as the sum of the regression predictions and the inverse distance weighted interpolation of residuals. The maps for the N at both site types (canopy/open) identified similar areas with increased N concentrations. The sole exception was the mosses collected under the canopy, for which some local emitters of NO_x were also identified.