Does pH matter for ecosystem multifunctionality? An empirical test in a semi-arid grassland on the Loess Plateau

Date of data collection: 2016-2018 Geographic location of data collection: Guyuan, Ningxia, China (106°23′E, 36°15′N) These data were generated to (i) investigate the responses of soil properties, biological communities and multifunctionality to decreased soil pH; (ii) determine the potential biotic and abiotic pathways that soil pH may drive multifunctionality. In 2016, a 17 m × 40 m semi-arid grassland plot with an initial pH value of 8.05 and uniform vegetation was selected. The experiment was granted by the administration of Yunwu Mountain National Nature Reserve. A randomized block design was used with five treatments and six replicates per treatment. A total of 30 plots were established. All plots were 2 m × 2 m and separated by 1 m buffer zones. The treatments included five levels of acid addition rate (0, 0.23, 0.56, 3.60, and 9.01 mol H+ m-2) in the form of sulphuric acid solution. In late August 2017, the plant communities achieved their peak biomass, and were surveyed and har..., 1. Plant community and primary productivity Total numbers of species and individuals observed in each quadrat were measured as species richness and abundance, respectively. The species diversity of each plot was also characterized by Shannon Wiener's diversity index and Simpson’s diversity index. The species evenness was characterized by Pielou's evenness index. We measured soil respiration, root respiration, ecosystem respiration (ER) and net ecosystem C exchange (NEE) one time in mid-August 2017. Gross primary productivity (GPP) is the sum of NEE and ER. 2. Soil properties Soil pH was measured in a 1/2.5 ratio (soil/water) suspension. A rapid method of soil carbonate analysis using gas chromatography (GC-7890B, Agilent, Santa Clara, CA, USA) was used to measure soil carbonate. A 20 g subsample of the fresh soil was oven-dried at 105 °C for 24 h to determine soil moisture. Ammonium and nitrate concentrations in soil extracts were measured using a segmented flow analyzer (Skalar SAN Plu...,