The carbon and nitrogen isotope composition of Australian grasses in relation to climateстатья из журнала
Аннотация: Summary 1. The carbon and nitrogen isotope composition of plants are known to be affected by environmental factors, especially water availability. While δ 13 C of C 4 plants is generally assumed to be much less responsive to environmental variables than that of C 3 plants, it is unclear whether the response of δ 15 N differs between the two photosynthetic pathways. 2. Focussing on differences in the response of members of the C 3 and C 4 photosynthetic pathways to climate variables, we examined the foliar δ 13 C and δ 15 N of grasses collected from natural vegetation in a wide range of climatic zones throughout Australia. 3. An index of water availability was clearly related to foliar δ 13 C and δ 15 N of both C 3 and C 4 grasses. There was a negative relationship between water availability and δ 13 C of C 3 grasses ( r 2 = 0·21), similar to that documented extensively in other C 3 plants. An opposite, positive relationship was found between water availability and δ 13 C in C 4 grasses ( r 2 = 0·17), an effect that has been reported only infrequently. Accounting for differences in δ 13 C between the different C 4 types (NADP‐ME, PCK, NAD‐ME and Aristida ) resulted in a substantial increase in the fit of the model relating δ 13 C to water availability ( R 2 = 0·48). 4. There was a negative relationship between water availability and δ 15 N ( r 2 = 0·40), that was similar in both C 3 and C 4 grasses, but temperature had no effect on δ 15 N. This provides strong support for the theory that water availability is the dominant factor determining soil and plant δ 15 N via its effect on the ‘openness’ of the nitrogen cycle. 5. We also found significant differences in δ 15 N between the different C 4 types, with the highest values for PCK, followed by NADP‐ME and NAD‐ME, and the lowest values for Aristida . The difference in δ 15 N between PCK and Aristida was large, at 5·1‰. 6. The importance of water availability as a predictor of δ 13 C in both C 3 and C 4 grasses suggests that variation in water availability should be considered when estimating C 4 grass abundance based on δ 13 C measurements (e.g. in herbivore diets or as a contributor to biospheric carbon sinks).
Год издания: 2009
Авторы: Brett P. Murphy, David M. J. S. Bowman
Издательство: Wiley
Источник: Functional Ecology
Ключевые слова: Isotope Analysis in Ecology, Plant Water Relations and Carbon Dynamics, Geology and Paleoclimatology Research
Открытый доступ: bronze
Том: 23
Выпуск: 6
Страницы: 1040–1049