Plant nutrient stoichiometry appears out of sync from soil: Increasing influences of changing climate on the grassland in inner Mongolia, China

Abstract

Extremes in weather episodes seem to be the new normal. We need to better understand how changing climatic conditions alter plant growth in grasslands, especially macro nutrient uptake and stoichiometry. However, few studies have examined how warmer/colder or wetter/drier climates influence the nutrient coupling between plants and soils at the ecosystem level. Here, we investigated the changes in carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometric ratios in plants and soils from 65 grassland sites along a geographic gradient in northern China. Results showed that soil C, N and P were negatively correlated with temperature and aridity. Plant N was positively correlated with temperature and aridity, but plant P was negatively correlated with temperature and aridity. Plant C had no significant relationship with either aridity or temperature. Both temperature and aridity were positively correlated with C:N, but negatively correlated with C:P and N:P in soils. The ratio of plant C:N was negatively correlated with aridity, while plant C:P was positively correlated with temperature. Plant N:P was positively correlated with temperature and aridity. Our findings imply that the often-found positive relationships between plant and soil nutrients at one site might not apply to a broad geographic scale with varying climatic conditions, likely because of the “dilution effect” and disparate plant nutrient utilization strategies. It is conceivable that rapid climate shifts and the resulting changes in element availability, turnover rates, absorption, and use efficiency might cause desynchrony of C, N, and P cycles between plants and soils.