The spatiotemporal change and trend of annual potential evapotranspiration (PET) over the Loess Plateau of Chinafrom 2011 to 2100 areassessed in this work. PET iscalculated using the Hargreaves modelwith monthly mean, maximum, and minimum temperaturesand a 1kmspatial resolution, which are generated using the Delta downscaling methodand general circulation models(GCMs)with four representative concentration pathway(RCP)scenarios.ThePET trend is detected via Mann-Kendall and Sen's slope estimatortests.The following results are drawn: (1) the Delta downscaling method shows a favorable performance in detecting GCM monthly temperaturesbased on the mean absolute error and regression analysis between downscaled data and independent surface observations.Among the 28 GCMs, the NorESM1-M and GISS-E2-R modelsshow the best performancein reproducing the monthly mean/maximum and minimum temperaturesover the Loess Plateau, respectively; (2)the average annual PET over this region will increase by 12.7% to 23.9% from 1961-1990 to the end of this century(2071-2100).However, these incrementsshow strong spatial variations; (3)the annual PET during the 2011-2100 period at each grid of the region demonstrates a significantly increasing trend under each RCP scenario, while RCP2.6, RCP4.5, RCP6.0, and RCP8.5have average magnitudes of trend of10.4 mm/10yr,17.7mm/10yr,21 mm/10yr,and 29.7 mm/10yr, respectively;(4) the annual PET with significanttrendsduring the other three periods (2011-2040, 2041-2070, and 2071-2100)present various spatial distributionsin their magnitudes of trendunder the aforementioned RCP scenarios. RCP2.6 showed a significant decreaseduring 2041-2070 and 2071-2100, although such trends are only observed at 0.3% and 1.2% of the Loess Plateau, respectively; and (5)the spatial results providesomeinformation, such as locations and area ratios, which are valuablein assessingfuture PET changes and trends.These spatiotemporal results represent the PET changesand trends in detail and provide insights for developing flexible adaptation and mitigation strategies to 3 combat the effects of global warmingin this region.

Schematic illustration of the spatial downscaling process. The downscaled precipitation field is constructed from CRU data in August 2014.

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The nutrient ecological stoichiometry of plants and soil is important for the growth and dynamics of species, but the stoichiometric relationships among leaf, litter, and soil remain poorly understood. We analyzed the carbon (C), nitrogen (N), and phosphorus (P) stoichiometry of the leaves, litter, and soil for 31 species at 140 sites in warm temperate forests in northwestern China to document the patterns of nutrient traits and their relationships with climatic factors. The average concentrations of C, N, and P in the combined forests were 462.97, 18.04, and 1.32 g kg−1 for leaves, 365.12, 12.34, and 0.87 g kg−1 for litter, and 15.72, 1.29, and 0.54 g kg−1 for soil, respectively. The concentrations differed significantly among the leaves, litter, and soil. Leaf and soil nutrients were not significantly correlated, whereas leaf and litter nutrients and litter and soil nutrients were significantly correlated, indicating that litter provided a link between leaves and soil and demonstrating the nutrient associations among leaves, litter, and soil. Soil nutrients were strongly correlated with climatic factors, and precipitation had a larger impact than temperature on the plants and soil. This study will help to predict the growth and dynamics of species under environmental changes.

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Understanding the water sources and physiological responses to soil moisture pulses for plantation species, particularly in mixed plantations, are essential to assess the water use strategy and vegetation restoration in semiarid regions. We used hydrogen stable isotopes in plant and soil water to determine the potential water sources for Pinus tabuliformis and Hippophae rhamnoides in both pure and mixed plantations in the semiarid Chinese Loess Plateau during the vigorous growing season (June–August) in 2016. Stomatal conductance (gc), midday leaf water potential (Ψm) and photosynthetic rate (Pr) were measured concurrently to analyse the physiological response. The P. tabuliformis in the pure plantation depended largely on shallow and middle soil layers regardless of precipitation amount, permitting this species to maintain stable Ψm at the expense of Pr through stomatal control. In contrast, H. rhamnoides in the pure plantation shifted its water source from shallow to deep soil layers following decreases in precipitation, allowing this species to maintain stable gc and Pr at the expense of Ψm. Thus, P. tabuliformis and H. rhamnoides displayed isohydric and anisohydric behaviour, respectively. Additionally, both species in mixed plantations largely absorbed water from shallow soil layers and shifted to deep soil layers when precipitation decreased. Mixed afforestation significantly reduced (p < .05) Pr for P. tabuliformis and Ψm for H. rhamnoides. Although contrasting physiological responses were adopted by these species, the major proportion of water resources were competitively obtained from similar soil depths—indicating that their mixed afforestation requires further investigation.