Relationships between foliar carbon isotope composition and elements of C3 species in grasslands of Inner Mongolia, China

Abstract

Foliar elements and their ratios can be related to foliar carbon isotope composition (d 13 C) through their involvement in plant transpiration, photosynthesis, and osmotic adjustment. In order to investigate these relationships in grasslands of Inner Mongolia, China, d13 C and element contents of dominant C 3 species at 47 grassland sites were determined. For C 3 species, d13 C showed no correlation with carbon (C), positive correlations with nitrogen (N), nitrogen:phosphorus ratio (N/P) and carbon:phosphorus ratio (C/P), and negative correlations with phosphorus (P), potassium (K), and carbon:nitrogen ratio (C/N), while correlation with P was subsidiary to positive correlation between P and K. These correlations indicate that plants in Inner Mongolia that survive in dry conditions may profit from their higher water use efficiency via stomatal regulation and N-related photosynthetic capacity rather than K-related osmotic adjustment and P-related photosynthetic capacity. Further, plants adapt to severe environments by having higher water and phosphorus use efficiency at the expense of nitrogen use efficiency. However, these correlations differed among plant functional groups (PFGs), e.g., d13 C was negatively correlated with N in shrubs in contrast to other life forms. A possible explanation is that shrubs adapt to low N availability by having lower photosynthetic nitrogen use efficiency (PNUE), so that N is not positively related to photosynthetic rate in shrubs. Obviously, data on stomatal conductance, PNUE, and cell osmotic pressure are needed to fully understand these correlations and the strategies of plants adapted to arid environments.

Leaf Age Compared to Tree Age Plays a Dominant Role in Leaf δ13C and δ15N of Qinghai Spruce (Picea crassifolia Kom.)

“…Multiple studies have reported various correlations between the δ 13 C and leaf nutrients [20,21,38]. In the present work, the positive relationship between δ 13 C and N over all aged leaves together (Table 2) is in accordance with most previous studies [20,39].…”

“…Our study observed that leaf δ 13 C was positively related to all aged leaves' P concentrations in simple regression (Table 2), but the effect of leaf P concentration on δ 13 C was not significant in multiple regression ( Figure 4A). This indicates that the variations in the leaf δ 13 C values were likely caused by stomatal limitation rather than P-related changes in photosynthetic efficiency [18,20]. In addition, our findings of the negative correlation between leaf δ 13 C and the C:N ratios is consistent with the results from multiple previous studies and suggests that P. crassifolia may achieve higher water use efficiency (WUE) at the expense of decreased nitrogen use efficiency (NUE) [20,38].…”

“…Moreover, our conclusions suggest that the relative contribution of leaf N concentrations on δ 13 C was significant (p < 0.01). The main cause of the positive relationships was that photosynthetic capacity increased with leaf N concentrations [20], and there was a positive correlation between leaf δ 13 C and photosynthetic capacity [4]. However, other studies have found a negative correlation between leaf δ 13 C and leaf N concentrations, and this was likely attributed to the presence of nitrogen-fixing species in samples such as Caragana microphylla [5] or an autocorrelation with water availability in a semiarid environment.…”

“…Current work has demonstrated that plant δ 13 C is also influenced by various environmental factors such as precipitation, humidity, soil moisture, and air temperature [18,19]. Furthermore, leaf functional elements such as nitrogen (N) and phosphorus (P) also play a key role in δ 13 C values through their indirect effects on photosynthetic capacity and the synthesis of proteins, DNA and RNA [20,21]. However, our knowledge on the relative role of these parameters in leaf δ 13 C values remains incomplete.…”

Spatial Variation in Leaf Stable Carbon Isotope Composition of Three Caragana Species in Northern China

“…Nevertheless, our results indicated that leaf δ 13 C showed a negative relationship with N and P concentrations for all species, which has also been observed in several previous studies [28,40,41,[63][64][65]. Moreover, the negative correlation between leaf δ 13 C and leaf N concentration is reported to be independent of functional group, vegetation type, and altitude, suggesting that this is a general trend for plants [66,67]. Other studies have interpreted the negative correlation between leaf δ 13 C and leaf N concentration as an autocorrelation due to low water availability in semi-arid environments [63,67].…”