Leaf δ13C variability with elevation, slope aspect, and precipitation in the southwest United States

Abstract

Leaves from several desert and woodland species, including gymnosperms and angiosperms with both C and C physiology, were analyzed to detect trends in δC with elevation and slope aspect along two transects in southeastern Utah and south-central New Mexico, USA. The main difference between the two transects is the steeper elevational gradient for mean annual and summer precipitation in the southern transect. For any given species, we found that isotopic differences between individual plants growing at the same site commonly equal differences measured for plants along the entire altitudinal gradient. In C plants, δC values become slightly enriched at the lowest elevations, the opposite of trends identified in more humid regions. Apparently, increasing water-use efficiency with drought stress offsets the influence of other biotic and abiotic factors that operate to decrease isotopic discrimination with elevation. For some species shared by the two transects (e.g., Pinus edulis and Cercocarpus montanus), δC values are dramatically depleted at sites that receive more than 550 mm mean annual precipitation, roughly the boundary (pedalfer-pedocal) at which soils commonly fill to field capacity in summer and carbonates are leached. We hypothesize that, in summer-wet areas, this may represent the boundary at which drought stress overtakes other factors in determining the sign of δC with elevation. The opposition of isotopic trends with elevation in arid versus humid regions cautions against standard correction for elevation in comparative studies of δC.

Soil n‐alkane δ13C along a mountain slope as an integrator of altitude effect on plant species δ13C

“…This pattern of d 13 C SOM and d 13 C wax responses to altitude has been observed for C 3 plants on species-level d 13 C investigations in many arid areas as well, and is attributed to the physiological effect of restricted water availability at lower elevations [Ehleringer and Cooper, 1988;Lajtha and Getz, 1993;Van de Water et al, 2002]. The low altitudes of the eastern flank of Mt.…”

“…The global pattern of plant species-level d 13 C increase with altitude is established from humid areas avoiding drought stress, and hence above this precipitation threshold, reflecting the response of gas exchange physiology to altitude, i.e., reducing stomatal conductance and decreasing the ratio of internal to external CO 2 concentrations (c i /c a ) due to the decreasing temperature and atmospheric partial pressure of CO 2 and O 2 with altitude [e.g., Körner et al, 1991;Kelly and Woodward, 1995]. However, below the precipitation threshold, a negative correlation occurs between total annual precipitation and plant d 13 C, suggesting that precipitation is an important factor influencing plant physiology [Leffler and Evans, 1999;Leffler and Enquist, 2002;Van de Water et al, 2002;Song et al, 2008], i.e., a reduction in stomatal conductance and leaf c i /c a as soil moisture declined. Both scenarios likely occur along the eastern slope of Mt.…”

“…This phenomenon has been attributed to decreasing temperature and atmospheric partial pressure of CO 2 and O 2 with altitude [e.g., Körner et al, 1991;Kelly and Woodward, 1995]. While in arid areas, drought stress may overtake other factors in determining the sign of plant d 13 C with elevation, and usually leads to a decreasing trend upward due to the increase of precipitation with altitude [e.g., Van de Water et al, 2002]. However, it is unknown to what extent the altitudinal trends in specieslevel d 13 C reflect geographical variations in ecosystem characteristics of structure and function.…”

The effects of short-term rainfall variability on leaf isotopic traits of desert plants in sand-binding ecosystems

“…A large body of literature has reported negative correlations between plants δ 13 C values and the availability of water (e.g., precipitation) (Miller et al, 2001; Van de Water et al, 2002;Swap et al, 2004;Murphy and Bowman, 2009;Wang et al, 2010b). In our study, foliar δ 13 C values of the three shrubs in the extremely arid year of 2005 (61.3 mm precipitation during the growing season) were significantly more positive than those in the arid year of 2004 (107.1 mm precipitation during the growing season).…”

Adaptability to elevated temperature and nitrogen addition is greater in a high-elevation population than in a low-elevation population of Hippophae rhamnoides

“…In addition, many previous observations have showed that d 13 C increases with elevation in conifer leaves (Hultin and Marshall 2000;Li et al 2004). Correlations between d 13 C and various abiotic factors over altitude gradients have been reported, including soil moisture, air temperature, atmospheric CO 2 concentration and evaporative demand (Van de Water et al 2002;Maunoury-Danger et al 2010). Our results indicated that elevated temperature resulted in higher long-term water use efficiency in the high-elevation population than in the low-elevation population.…”