Relationships between C3 Plant Foliar Carbon Isotope Composition and Element Contents of Grassland Species at High Altitudes on the Qinghai-Tibet Plateau, China

Abstract

Relationships of foliar carbon isotope composition (d 13 C) with foliar C, N, P, K, Ca, Mg contents and their ratios of 219 C 3 species leaf samples, obtained in August in 2004 to 2007 from 82 high altitude grassland sites on the Qinghai-Tibet Plateau China, were examined. This was done with reference to the proposition that foliar d 13 C increases with altitude and separately for the life-form groups of graminoids, forbs and shrubs and for the genera Stipa and Kobresia. For all samples, foliar d13 C was negatively related to foliar K, P and g K+ Ca+ Mg , and positively correlated to foliar C, C/N and C/P. The significance of these correlations differed for the taxonomic and life-form groups. Lack of a relationship of foliar d 13 C with foliar N was inconsistent with the majority of studies that have shown foliar d 13 C to be positively related to foliar N due to a decrease of C i /C a (the ratio between intercellular and atmospheric concentration of CO 2 ) and explained as a result of greater photosynthetic capacity at higher foliar N concentration. However this inconsistency relates to other high altitude studies that have found that photosynthetic capacity remains constant as foliar N increases. After accounting for the altitudinal relationship with foliar d 13 C, of the elements only the K effect was significant and was most strongly expressed for Kobresia. It is concluded that factors critical to plant survival and growth at very high altitudes, such as low atmospheric pressure and low temperatures, may preclude expression of relationships between foliar d 13 C and foliar elements that have been observed at lower altitudes.

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

“…Generally, C was negatively correlated with ash or mineral content (Zhou et al 2013). Thus, positive correlation between d 13 C and C was expected.…”

“…Pinus tabulaeformis is negatively related to N. Negative relationships between d 13 C and K were reported for Quercus aquifolioides (Li et al 2009), Pinus tabulaeformis (Li et al 2011), sugar beet (Tsialtas and Maslaris 2006), and grassland species on QinghaiTibet Plateau (Zhou et al 2013). However, while Cao et al (2009) and Zhao et al (2007) found negative relationships between d 13 C and K for Tamarix ramosissima, Artemisia ordosica, and Hedysarum scoparium, as well, they also found positive relationships for Populus euphratica and Caragana korshinskii.…”

“…However, compared with environmental factors, fewer studies have been conducted for leaf elements (Zhou et al 2013), even though these may have important roles in controlling foliar d…”

“…13 C values positively correlate with N (Hamerlynck et al 2004;Ma et al 2012;Prasolova et al 2005;Sparks and Ehleringer 1997), Zhou et al (2013) found that the low atmospheric pressure and temperatures of QinghaiTibet Plateau may preclude expression of positive relationship between d 13 C and N. Li et al (2015) also found no correlation between d…”

“…Further, foliar element ratios, e.g., C/N (foliar carbon:nitrogen ratio), C/P (foliar carbon:phosphorus ratio), and N/P (foliar nitrogen:phosphorus ratio), are also key traits of ecological relevance and link with d 13 C through their correlation with water use efficiency (WUE). For example, Cernusak et al (2010) observed a positive correlation between leaf N/P ratio with WUE and that with d 13 C. However, previous studies have suggested that relationships between foliar d 13 C and elements differ for study areas and plant species (Cao et al 2009;Zhao et al 2006Zhao et al , 2007Zhou et al 2013). For example, although most studies have reported that d…”