Nitrogen fertilization and fire act independently on foliar stoichiometry in a temperate steppe

Abstract

Nitrogen (N) fertilization, as a grassland management strategy, has been widely used to improve forage quality and increase the productivity of grasslands degraded by overstocking. It is widely accepted that N addition will alter ecosystem structure and function, and that these effects may be altered by natural disturbances, such as fire. We examined the effects of annual burning and N fertilization (17.5 g N m −2 year −1 , at a surplus rate in order to simulate agriculture treatment) on foliar chemistry and stoichiometric ratios of eight dominant species (Leymus chinensis, Stipa grandis, Cleistogenes squarrosa, Potentilla bifurca, Thalictrum squarrosum, Artemisia frigida, Kochia prostrata and Caragana microphylla) in a temperate steppe in northern China. After 3 years of treatments, annual burning significantly increased soil extractable phosphorus (P) concentration but showed no effects on soil inorganic N concentration, whereas N fertilization caused a significant increase in inorganic N concentration but not of extractable P. Species differed substantially with respect to all nutritional and stoichiometric variables. Both annual burning and N fertilization caused significant increases in foliar N and P concentrations and thus decreases in carbon (C):N and C:P ratios. While annual burning showed no effects on N:P ratios, N fertilization produced higher N: P ratios. However, species responded idiosyncratically to both fire and N fertilization in terms of foliar N concentration, C:N and N:P ratio. In addition, there was no interaction between fire and N fertilization that affected all variables. This study suggests that both annual burning and N fertilization have direct impacts on plant elemental composition and that fire-and N addition-induced changes of community composition may have important consequences for plant-mediated biogeochemical cycling pathways in temperate steppe ecosystem.

Influence of Nitrogen Fertilization on Wheat, and Soil Carbon, Nitrogen and Phosphorus Stoichiometry Characteristics

“…The higher leaf N content and N: P may reflect the high N availability in the N treatments . In this study, the N: P ratios were significantly higher in the N treatments, due to the greater availability of N than P, consistent with previous studies (Craine et al, 2008;Cui et al, 2010). The N treatments had higher C: P ratios than the non-N treatment, but no significant differences were found between N treatments at anthesis.…”

“…The C: P ratio had a similar trend to the N: P. Maximum N: P was in the flag leaf, which caused by the lower P content. The higher C: P ratios in the N treatments were probably caused by the decrease in P as N fertilizer application and consistent with the results reported by Cui et al (2010) for N addition in a temperate steppe ecosystem. N and P content decreased from anthesis to harvest stages, leading C: N and C: P ratios increase in harvest.…”

“…The data were natural log transformed when needed, for meet the assumption of normal distribution of data and homogeneity of variances (Cui et al, 2010). C, N and P stoichiometry were used the mass ration of nutrition content.…”

Carbon, nitrogen and phosphorus stoichiometry in differently aged lucerne stands during flowering

“…No significant difference was found between this study and previous report (Wang et al, 2014) and between lucerne and other species from larger scales (Elser et al, 2000;He et al, 2008;McGroddy et al, 2004;Reich and Oleksyn, 2004;Townsend et al, 2007;Zheng and Shangguan, 2007). This result differs a lot from what we knew from a semi-arid grassland of China (Cui et al, 2010), in which the legume shrub showed the highest foliar N:P. However, in most cases lucerne leaf N:P was higher than the global values, possibly resulting from the very high Volume 39 Issue 4 (2016) 599 N concentration of leguminous lucerne with strong BNF. Dramatically, leaf N:P of other legumes (He et al, 2008) and tropical rainforests (Townsend et al, 2007) were higher than those of lucerne leaf.…”

“…These values were much lower than those of other species from larger scales (Elser et al, 2000;He et al, 2006;McGroddy et al, 2004;Zheng and Shangguan, 2007). Generally leguminous species has the lowest C:N than other species (Cui et al, 2010) due to more N accumulation. There was significant cut effect on leaf C:N of lucerne, in agreement with Wang et al (2013).…”