Carbon isotope dynamics in Abies amabilis stands in the Cascades

1998 ◽  
Vol 28 (6) ◽  
pp. 808-819 ◽  
Author(s):  
N Buchmann ◽  
T M Hinckley ◽  
J R Ehleringer
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Stand Structure ◽  
Ecosystem Respiration ◽  
Soil Conditions ◽  
Silver Fir ◽  
Old Growth ◽  
Area Index ◽  
Isotope Discrimination ◽  
Abies Amabilis

Carbon isotope ratios ( delta 13C) of canopy air and carbon isotope discrimination at the ecosystem level were studied in three montane Pacific silver fir (Abies amabilis (Dougl. ex Loud.) Dougl. ex J. Forbes) stands, an old-growth and two younger stands. Spatial and temporal variations of canopy CO2 concentrations ([CO2]) and their delta 13C were strongly related to stand structure. Within the old-growth stand, both daytime canopy [CO2] and canopy delta 13C stayed close to those of the troposphere, either indicating low overall photosynthetic rates or high turbulent mixing. Pronounced periods of photosynthetic drawdown below baseline [CO2] accompanied by more enriched canopy delta 13C were observed for the two younger and denser stands. Canopy [CO2] profiles seemed closely related to changes in soil conditions. Soil respiration rates were positively related to soil temperature, but negatively to soil moisture. delta 13C of soil-respired CO2 stayed relatively constant at -24.55 ± 0.20%oduring the growing season. Significant relationships existed between canopy delta 13C and 1/[CO2] in all three stands. Using the intercepts of these regressions, we calculated an average delta 13C for ecosystem respiration of -26.4 ± 0.1%o. Ecosystem carbon isotope discrimination ( DELTA e), an integrating measure for carbon exchange between the troposphere and the entire ecosystem, stayed relatively constant through time. DELTA e showed no significant stand structure effect (leaf area index, density) and averaged 18.9%o for the old-growth and 19.2 ± 0.2%ofor the two younger stands.

Photosynthetic carbon isotope discrimination and its relationship to the carbon isotope signals of stem, soil and ecosystem respiration

2010 ◽  
Vol 188 (2) ◽  
pp. 576-589 ◽  
Author(s):  
Lisa Wingate ◽  
Jérôme Ogée ◽  
Régis Burlett ◽  
Alexandre Bosc ◽  
Marion Devaux ◽  
...  
Keyword(s):  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Ecosystem Respiration ◽  
Isotope Discrimination ◽  
Photosynthetic Carbon

scholarly journals Carbon isotope discrimination by Picea glauca and Populus tremuloides is related to the topographic depth to water index and rainfall

2016 ◽  
Vol 46 (10) ◽  
pp. 1225-1233 ◽  
Author(s):  
Gabriel S. Oltean ◽  
Philip G. Comeau ◽  
Barry White
Keyword(s):  
Carbon Isotope ◽  
Populus Tremuloides ◽  
Picea Glauca ◽  
Carbon Isotope Discrimination ◽  
Tree Height ◽  
Carbon Isotope Ratio ◽  
Threshold Value ◽  
Soil Conditions ◽  
Isotope Discrimination ◽  
Water Index

Carbon isotope ratio (δ13C) has been used as an indicator of water stress because plants discriminate less against 13C when under stress. The depth-to-water (DTW) topographic index provides an estimation of soil moisture based on topographic position and other characteristics of a site. To evaluate whether DTW and carbon isotope discrimination were related and to determine if these relationships are influenced by climate, we sampled three time periods, which differed in the amount of annual precipitation (MAP), from tree cores collected from 42 trembling aspen and 43 white spruce trees growing along DTW gradients at two locations in central Alberta, Canada. Increasing MAP led to lower δ13C, indicating less drought stress as water availability increases, while δ13C increased with DTW up to a threshold value, after which the relationship levelled off, suggesting that higher DTW values represent stress-inducing soil conditions. DTW and MAP were then combined into models (aspen, R2 = 0.72; spruce, R2 = 0.44) that could be used to delineate drought-prone areas during periods of low MAP. Tree height and diameter were also related to DTW, suggesting a functional relationship between an index capturing soil properties and tree size. Our results demonstrate the potential to use the DTW index as a measure of site conditions and to predict stand-level responses.

Carbon Isotope Discrimination and Photosynthetic Gas Exchange in Coffee Hedgerows During Canopy Development

1994 ◽  
Vol 21 (2) ◽  
pp. 207 ◽  
Author(s):  
MV Gutierrez ◽  
FC Meinzer
Keyword(s):  
Stomatal Conductance ◽  
Gas Exchange ◽  
Carbon Isotope ◽  
Carbon Isotope Discrimination ◽  
Area Index ◽  
Canopy Development ◽  
Isotope Discrimination ◽  
Intrinsic Water Use Efficiency ◽  
Use Efficiency ◽  
Sun Leaves

In evergreen species, leaf carbon isotope discrimination (Δ) integrates phenological rhythms in gas exchange as well as seasonal changes in environmental conditions. However, few reports on long term variations in Δ of woody plants are available. We measured Δ, gas exchange, nitrogen content, and photosynthetic nitrogen-use efficiency (PNUE) in coffee hedgerows at different stages of canopy development encompassing a range of leaf area index (LAI) from 0.7 to 7.5. Assimilation was highest in sun leaves, but stomatal conductance was highest in shaded leaves. This resulted in a high correlation between assimilation and stomatal conductance in sun, but not in shaded leaves. Δ was about 20 lower in sun than in shaded leaves, and varied by 2.30 among leaves at different positions along two-year- old branches. These differences in Δ were the result of changes in carbon isotope composition that occurred in mature, fully expanded leaves as they became shaded during subsequent canopy growth. Results from a mass balance model based on leaf gas exchange characteristics and measured foliar Δ values suggested that about 50% of the carbon originally fixed during leaf development in the sun may have subsequently been turned over in the shade. Δ of sun leaves from the upper canopy decreased by about 20 with increasing LAI, indicating that intrinsic water-use efficiency (WUE) of this canopy layer increased during canopy development. In contrast, instantaneous WUE, estimated as assimilation divided by canopy transpiration obtained from sap flow measurements, seemed to decrease with increasing LAI. PNUE of upper canopy sun leaves decreased with increasing LAI, suggesting a physiological compromise between WUE and PNUE mediated by stomatal conductance, which also decreased with increasing LAI. A strong negative correlation obtained between leaf Δ and N content was consistent with a trade-off between intrinsic water- and N-use efficiency.

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