Researchers from the Institute of Applied Ecology of the Chinese Academy of Sciences have found that drought and nitrogen deposition are the primary drivers of changes in the elemental composition of plant litter in temperate grasslands, while variation within species plays a dominant role in shaping community-level responses.

The findings were published in Journal of Plant Ecology on May 26.

Plant litter, which consists of dead leaves and other plant materials that accumulate on the ground, serves as a critical link between aboveground vegetation and belowground ecological processes. Its chemical composition directly affects decomposition, nutrient release, and biogeochemical cycling in terrestrial ecosystems. As global environmental change intensifies, grasslands are increasingly exposed to pressures such as extreme drought, rising nitrogen deposition, and shifts in snow dynamics. Although previous studies have focused primarily on carbon, nitrogen, phosphorus and structural compounds such as cellulose and lignin, less is known about how a broader range of essential mineral elements respond to these environmental changes.

To address these issues, the researchers led by Dr. WANG Zhengwen conducted a long-term multifactor global change experiment at the Erguna Forest-Steppe Ecotone Ecosystem Research Station in northern China. They simulated nitrogen deposition through nitrogen addition, altered snow conditions through delayed snowmelt treatments, and imposed drought treatments both individually and in combination.

The researchers measured the concentrations of primary macronutrients including carbon, nitrogen, phosphorus and potassium, secondary macronutrients calcium and magnesium, and micronutrients manganese, iron, copper and zinc in leaf litter. They also quantified the relative contributions of intraspecific trait variation and species turnover to community-level changes in litter elemental composition.

The results showed that drought and nitrogen addition had much stronger effects on litter elemental composition than delayed snowmelt. Overall, the concentrations of carbon, nitrogen and potassium in litter increased in response to drought or nitrogen addition. In contrast, calcium and magnesium concentrations declined under nitrogen addition, although drought partially weakened this effect. Among the micronutrients examined, manganese and zinc showed positive responses to nitrogen addition and drought, respectively, while copper and iron remained largely unchanged.

Further analyses revealed that intraspecific trait variation, which refers to changes in traits within the same species under different environmental conditions, was the dominant mechanism driving community-level changes in litter chemistry. In most cases where significant responses occurred, it accounted for the majority of observed variation. The researchers found that this mechanism was particularly important in explaining increases in nitrogen, potassium, manganese and zinc concentrations, as well as declines in magnesium concentration.

Species turnover, which reflects shifts in the relative abundance or presence of different plant species within a community, played a more limited but sometimes critical role. The researchers found that it was the primary mechanism responsible for declines in litter calcium concentration across treatment conditions. They also observed that species turnover could offset the positive effect of intraspecific trait variation on manganese concentration, helping maintain relatively stable community-level manganese levels despite environmental change.

According to the researchers, this study demonstrates that different litter elements respond in distinct ways to multiple global change drivers and that these responses are governed by the combined influences of trait variation within species and changes in species composition.