Acid deposition and soil acidification are highly detrimental to ecosystems. Due to rapid industrialization and fossil fuel combustion, acid deposition has been increasing and the affected area expanding in large parts of Asia. While previous research about soil acidification effects mainly focused on forests, our knowledge of its effects on grasslands is still lacking, particularly for alpine grasslands. In a soil pH manipulation experiment with a gradient of acid addition in the Qinghai-Tibet Plateau, the effects of soil acidification on plant community and belowground properties were investigated, with emphasis on root biomass and traits, as roots account for the major part of plants in alpine ecosystems.
Results/Conclusions
After three years of manipulation, soil pH decreased from 6.0 to 4.7 with the acid-addition gradient, accompanied by significant increases in soil exchangeable Al and available P, and decreases in soil NO3− and exchangeable Ca, Mg, while soil organic carbon (C) did not significantly change. Plant composition was also shifted, with sedges and grasses increasing, while forbs decreasing with the soil acidification. Differing from previous findings of reduced root biomass in acidified soils in forests, soil acidification in the alpine grassland increased root biomass. At the community level, the fraction and diameter of coarse roots, as well as the production of fine roots, increased with soil acidification, which were related to enhanced sedge and grass biomass, respectively. Our results suggest that soil acidification may lead to transient increases in root standing biomass and alteration in root traits at the community level. These changes, combined with slowed decomposition and nutrient cycling, may further constrain ecosystem productivity in nutrient-limiting alpine systems.