Summary Carbon isotope discrimination (Δ) has been used widely to infer intrinsic water‐use efficiency (iWUE) of C 3 plants, a key parameter linking carbon and water fluxes. Despite the essential role mesophyll conductance ( g m ) in photosynthesis Δ, its effect on Δ‐based predictions iWUE generally neglected. Here, we derive mathematical expression as function Δ that includes (iWUE mes exploits ‐stomatal sc relationship across drought‐stress levels plant functional groups (deciduous or...

ABSTRACT The CO 2 respired by leaves is 13 C‐enriched relative to leaf biomass and putative respiratory substrates (Ghashghaie et al ., Phytochemistry Reviews 2, 145–161, 2003), but how this relates the C content of root, or whole plant unknown. isotope composition ( δ R ) from shoots roots sunflower Helianthus annuus L.), alfalfa Medicago sativa perennial ryegrass Lolium perenne L.) growing in a range conditions was analysed. In all instances plants were grown controlled environments with...

Abstract Global warming, increasing CO 2 concentration, and environmental disturbances affect grassland communities throughout the world. Here, we report on variations in C3/C4 pattern of Inner Mongolian derived from soil vegetation. Soil samples 149 sites covering an area approximately 250 000 km within Mongolia, People's Republic China were analyzed for isotopic composition ( δ 13 C) organic carbon (SOC). The contrast C between C3 C4 plants allowed calculation ratio SOC with a two‐member...

Abstract Background The anthropogenic increase of atmospheric CO 2 concentration ( c a ) is impacting carbon (C), water, and nitrogen (N) cycles in grassland other terrestrial biomes. Plant canopy stomatal conductance key player these coupled cycles: it physiological control vegetation water use efficiency (the ratio C gain by photosynthesis to loss transpiration), responds photosynthetic activity, which influenced N status. It unknown if the -increase climate change over last century have...

The emergence of a regular phyllochron from the dynamic processes leaf initiation, elongation and whorl construction suggests causal relationships between emergence. This paper presents hypothesis as to how ontogeny growth zone leaves is triggered by events, implements it in model elongation. Two different experiments, presenting two contrasted cases kinetics elongation, were analysed interpreted with terms functioning zone. Analysis revealed that allows for several patterns observed,...

Summary 1. Recently, Caut, Angulo & Courchamp (2009, Journal of Applied Ecology ) published a review on diet‐tissue isotopic shifts in animals. They concluded that are influenced by the composition diet for both 13 C and 15 N wide range animal taxa. 2. We suggest conclusion is error, provide discussion sources error assessment discrimination. 3. Errors derivation include imprecise definitions, mathematical artefacts invalid statistical analysis. It likely work also suffers from...

ABSTRACT A 13 C/ 12 C mass spectrometer was interfaced with a open gas exchange system including four growth chambers to investigate CO 2 components of perennial ryegrass ( Lolium perenne L.) stands. Chambers were fed air containing known δ CΟ2 −2.6 or −46.8‰). The did not fractionate isotopes and no extraneous leaked into chambers. on‐line discrimination (Δ) stands in light independent when constant. exchanged by the Nd ) darkness Rn differed 0.7‰, suggesting some Δ dark respiration at...

Abstract The carbon isotope composition ( δ 13 C) of C3 ecosystems is sensitive to water availability, and provides important information for the assessment terrestrial (C) sink/source activity. Here, we report effects plant available soil (PAW) on community C signatures temperate humid grassland. 5‐year study was conducted pastures exhibiting a large range PAW capacity that were located two site types: peat mineral soils. data set included centennial drought year 2003, from wet years (2000...

Abstract. This work explored the spatial variation of C3/C4 distribution in Inner Mongolia, P. R. China, steppe by geostatistical analysis carbon isotope data vegetation and sheep wool. Standing community biomass (n=118) wool (n=146) were sampled a ~0.2 Mio km2 area. Samples from ten consecutive years (1998–2007) obtained. Community samples represented isotopic composition standing on about 1000 m2 ("community-scale"), whereas spatio-temporal scale reflected entire area grazed herd during...

The substrate supply system for respiration of the shoot and root perennial ryegrass (Lolium perenne) was characterized in terms component pools pools' functional properties: size, half-life, contribution to shoot. These investigations were performed with growing constant conditions continuous light. Plants labeled 13CO2/12CO2 periods ranging from 1 600 h, followed by measurements rates 13C/12C ratios CO2 respired shoots roots dark. Label appearance delayed approximately h relative shoots;...

ABSTRACT While there is currently intense effort to examine the 13 C signal of CO 2 evolved in dark, less known on isotope composition day‐respired . This lack knowledge stems from technical difficulties measure pure respiratory isotopic signal: day respiration mixed up with photorespiration, and no obvious way separate photosynthetic fractionation (pure c i / a effect) effect (production different δ value that net‐fixed ) at ecosystem level. Here, we took advantage new simple equations,...

Effects of the arbuscular mycorrhizal fungus (AMF) Glomus hoi on carbon economy perennial ryegrass (Lolium perenne) were investigated by comparing nonmycorrhizal and plants same size, morphology phosphorus status. Plants grown in presence CO2 sources with different C isotope composition (delta13C -1 or -44). Relative respiration gross photosynthesis rates, belowground allocation assimilated during one light period ('new C'), as well its contribution to respiration, quantified concerted use...

Abstract. The relationship between carbon isotope discrimination (13Δ) of C3 vegetation and long-term (30 years) short-term (growing period) precipitation was investigated. Different species Stipa, a dominant grass genus in the (semi-)arid Asian steppes, other were collected along aridity gradients Inner Mongolia 2005 (11 sites, 71 samples) Republic 2006 (40 45 samples). data set expanded with published unpublished Stipa studies covering 8 years, including 64 observations 103 species)...

This work assessed the central carbohydrate metabolism of actively photosynthesizing leaf blades a C3 grass (Lolium perenne L.). The study used dynamic 13C labelling plants growing in continuous light with contrasting supplies nitrogen ('low N' and 'high N') mathematical analysis tracer data four-pool compartmental model to estimate rates of: (i) sucrose synthesis from current assimilation; (ii) export/use; (iii) hydrolysis (to glucose fructose) resynthesis; (iv) fructan resynthesis...

Abstract Leaks and isotopic disequilibria represent potential errors artefacts during combined measurements of gas exchange carbon isotope discrimination (Δ). This paper presents new protocols to quantify, minimize, correct such phenomena. We performed experiments with gradients CO 2 concentration (up ±250 μ mol −1 ) δ 13 C CO2 (34‰), between a clamp‐on leaf cuvette ( LI ‐6400) surrounding air, assess (1) leak coefficients for , 12 the empty intact leaves H olcus lanatus 3 or S orghum...

Summary Quantification of leaf respiration is important for understanding plant physiology and ecosystem biogeochemical processes. Leaf continues in the light ( R L ) but supposedly at a lower rate than dark D k ). However, there no method direct measurement available methods require nonphysiological conditions. A based on isotopic disequilibrium quantified 13C mesophyll conductance young old fully expanded leaves six species. was compared to determined by Laisk very same with minimum time...

We explore here our mechanistic understanding of the environmental and physiological processes that determine oxygen isotope composition leaf cellulose (δ18 Ocellulose ) in a drought-prone, temperate grassland ecosystem. A new allocation-and-growth model was designed added to an 18 O-enabled soil-vegetation-atmosphere transfer (MuSICA) predict seasonal (April-October) multi-annual (2007-2012) variation δ18 O-enrichment (Δ18 based on Barbour-Farquhar model. Modelled agreed best with...

The oxygen and hydrogen isotope composition of water in the leaf growth-and-differentiation zone, LGDZ, (δ18 OLGDZ , δ2 HLGDZ ) grasses influences isotopic cellulose (oxygen) wax (hydrogen) - important for understanding (paleo)environmental physiological information contained these biological archives but is presently unknown. This work determined δ18 18 O- 2 H-enrichment LGDZ (∆18 ∆2 ), blade OLW, HLW two C3 three C4 grown at high low vapor pressure deficit (VPD). proportion unenriched (px...

Abstract. The oxygen isotope composition (δ18O) of leaf water (δ18Oleaf) is an important determinant environmental and physiological information found in biological archives, but the system-scale understanding propagation δ18O rain through soil xylem to δ18Oleaf has not been verified for grassland. Here we report a unique comprehensive dataset fortnightly observations soil, stem waters made over seven growing seasons temperate, drought-prone, mixed-species Using ecohydrology part physically...

* The kinetic characteristics of the main sources ecosystem respiration are quite unknown, partly because methodological constraints. Here, we present a new open-top chamber (OTC) apparatus for continuous 13C/12C labelling and measurement CO2 fluxes, report tracer kinetics nighttime temperate grassland. includes four dynamic flow-through OTCs, unit mixing CO2-free air with 13C-depleted CO2, analyser an online isotope ratio mass spectrometer. concentration (367 +/- 6.5 micromol mol(-1))...

Stable isotope analysis of hair has found applications in many fields science because it provides a temporally resolved, fairly stable isotopic archive mammalian individuals. We investigated whether this is modified by natural weathering while attached to living animal. analyzed the tail switch hairs one suckler cow, sampled seven times over period four annual summer pasture-winter stall feeding cycles. compared relative ratios (δ²H, δ¹³C, δ¹⁵N, δ¹⁸O and δ³⁴S) sections that grew...