Relationship between the stable carbon isotopic composition of modern plants and surface soils and climate: A global review

Carbon and nitrogen isotope variability in the seeds of two African millet species: Pennisetum glaucum and Eleusine coracana

“…Both temperature and precipitation have varying degrees of influence on P. glaucum δ 13 C and δ 15 N values, together accounting for 48% and 34% of the total variation in pearl millet seed δ 13 C and δ 15 N values, respectively. The significant positive relationship that we observe between cumulative annual precipitation and P. glaucum seed δ 13 C values is opposite that observed in C 3 plants, but in line with some previous studies on C 4 plants and supported by physiological theory . Water availability, through a positive correlation with the ambient partial pressure of CO 2 (c i /c a ), is expected to have a positive correlation with δ 13 C values when leakiness ( ϕ ) is below a threshold value of 0.35 .…”

“…Water availability, through a positive correlation with the ambient partial pressure of CO 2 (c i /c a ), is expected to have a positive correlation with δ 13 C values when leakiness ( ϕ ) is below a threshold value of 0.35 . Temperature and P. glaucum seed δ 13 C values are significantly negatively correlated in our study, but over a very narrow temperature range (2.8°C), suggesting that these results, if expanded over a broader range, may not actually conflict with previous observations of no significant trend in foliar δ 13 C values with temperature . The positive correlation that we observe between cumulative annual precipitation and δ 15 N values in P. glaucum seeds is opposite to that observed in a global compilation of leaf δ 15 N values, but the weak significant positive relationship that we see between P. glaucum seed δ 15 N values and temperature is in agreement with previous research .…”

“…A growth chamber experiment that included five C 4 plant species found a slight decrease in δ 13 C value with increasing temperature . Others have observed no trends in δ 13 C values with temperature or a non‐significant negative correlation . It is interesting, therefore, that temperature and P. glaucum seed δ 13 C values are so strongly and significantly negatively correlated in our study.…”

“…Looking at precipitation alone, our findings suggest that precipitation has a small but significant effect on P. glaucum δ 13 C values (Figure ). Previous research examining the relationship between δ 13 C values in C 4 vegetation and rainfall has identified either a weak negative correlation, no relationship, or a positive correlation . A positive relationship between rainfall and δ 13 C values is opposite to that for C 3 plants (e.g.,) but nonetheless supported by physiological theory.…”

Holocene Moisture Variations in Western Arid Central Asia Inferred From Loess Records From NE Iran

“…Under natural conditions, C 3 plants will partially close their stomata to prevent water loess in dry conditions, which results in decreased stomatal conductance and an increased difference in CO 2 concentration between the inside and outside of the mesophyll cells, causing a decrease in C i / C a , which finally results in increased δ 13 C org , and vice versa (Balesdent & Mariotti, ; Melillo et al, ). It has been widely demonstrated that under C 3 plant‐dominated ecosystems, there is a negative correlation between the δ 13 C org values of modern C 3 plants and surface soils and precipitation (e.g., Diefendorf et al, ; Kohn, ; Rao et al, ; Wang, Wang, et al, 2019). A recent study also demonstrated that the modern natural ecosystem in NE Iran is dominated by C 3 plants and that the surface soil δ 13 C org values are strongly negatively correlated with MAP ( R 2 = 0.4419, p < 0.001; Wang, Wang, et al, 2019).…”