DOI: 10.5061/dryad.s7h44j1jx
title: Data from: Nutrient enrichment shifts peak water-use efficiency to wetter conditions in an alpine meadow

description: Ecosystem water-use efficiency, the ratio of gross ecosystem productivity
 to plant transpiration, is found to show a hump-shaped response to extreme
 water variations (with a peak at moderate water level). This peak
 water-use efficiency represents maximum carbon gain per unit of water
 consumed, with its associated water threshold indicating the optimal water
 level to maximize carbon uptake. However, it remains unclear whether
 widespread nutrient enrichment alters this peak water-use efficiency and
 its associated water threshold. Here, we conducted a 6-year field
 experiment involving precipitation reduction and multiple nutrient
 additions in an alpine meadow on the Qinghai-Tibet Plateau. A wide water
 gradient is created by combining experimental precipitation manipulation
 and interannual precipitation fluctuations. Our results showed a
 consistent hump-shaped response of ecosystem water-use efficiency to water
 variations in control, N, NP, and NPK treatments. While nutrient addition
 had little effect on peak water-use efficiency, it significantly increased
 the associated water threshold by 16.9-25.2% (from 540 mm to 631-676 mm).
 This increase was primarily caused by a U-shaped transpiration response,
 but not by the positive responses of gross ecosystem productivity to
 precipitation across all treatments. Specifically, nutrient addition
 elevated the transpiration water threshold (the water level for minimum
 transpiration) by 10.1-16.0% (from 406 mm to 447-471 mm). This U-shaped
 transpiration response to precipitation was mainly regulated by soil
 temperature in control plots, but by vertical root distribution in
 nutrient treatments. Synthesis. These new findings show that nutrient
 enrichment does not alter peak water-use efficiency but elevates its
 associated water threshold. This pattern indicates that nutrient-enriched
 ecosystems require more water than nutrient-poor ones to reach maximum
 carbon uptake, with important implications for predicting the dynamics of
 grassland carbon sink under the combined effects of soil water and
 nutrients.
description: # Nutrient enrichment shifts peak water-use efficiency to wetter
 conditions in an alpine meadow Tingting Li, Furong Wang, Yicheng He,
 Ruiyang Zhang, Jinsong Wang, Shuli Niu, Dashuan Tian* This study found
 that ecosystem water-use efficiency (WUE) consistently shows a hump-shaped
 response to water availability, peaking at moderate levels. While nutrient
 enrichment did not change the peak WUE, it significantly raised the water
 threshold needed to reach this peak, suggesting that nutrient-rich
 ecosystems require more water to maximize carbon uptake. #### Description
 of the data and file structure The dataset consists of a Excel file
 named data2.xlsx **Experiment design**: Nutrient addition × Precipitation
 reduction **Nutrients** N  10 g N m-2 year-1 NP  10 g N m-2 year-1 + 10 g
 P m-2 year-1 NPK  10 g N m-2 year-1 + 10 g P m-2 year-1 + 10 g K m-2
 year-1 **Precipitation** Reduced: Removing half ambient precipitation by
 passive rainout shelter Ambient: Ambient precipitation **Legend**
 Nutrient: Nutrient addition Precipitation: Precipitation reduction Growing
 season precipitation : The precipitation occurs during the growing season
 (May to September) (mm) Water-use efficiency: Ecosystem water-use
 efficiency (μmol·mmol-1) Transpiration: Ecosystem transpiration
 (mmol·m-2·s-1) Evapotranspiration: Ecosystem evapotranspiration
 (mmol·m-2·s-1) Soil evaporation: Soil evaporation (mmol·m-2·s-1) Deep root
 distribution: The ratio of subsoil to topsoil root biomass (%)