Effects of changes in precipitation on energy and water balance in a Eurasian meadow steppe

Abstract

Introduction: Water such as precipitation is the most critical environment driver of ecosystem processes and functions in semi-arid regions. Frequency and intensity of drought and transient waterlogging are expected to increase in the meadow steppe in northeastern China. Using a 4-year dataset of eddy covariance flux measurements, ground measurements of biomass, phenology, and meteorological conditions, we investigated the changes in energy fluxes at multiple temporal scales and under different precipitation regimes. Results: The meadow steppe was latent heat (LE) dominated when soil water content was > 0.3 m 3 m −3 , but switched to sensible heat (H) dominated status when soil water content fell below 0.3 m 3 m −3. LE dominated the energy exchange of the meadow grasslands on a yearly basis. Intensive precipitation had a profound impact on water-energy balance that could reduce the damages of drought by elevating deep soil moisture. The influence of LE on waterlogging depended on timing, with increased LE at the beginning of growing season and decreased LE after waterlogging. Spring and summer droughts resulted in different energy partitioning between latent and sensible heat energies, with spring drought dramatically decreased the LE fraction due to the change in water. In contrast, summer drought had little impact on LE due to the sufficient water input from large precipitation events at the beginning of the growing season. Conclusions: There existed great seasonal and interannual variabilities in energy balance and partitioning in the meadow steppe over the 4-year study period, which were strongly influenced by changes in precipitation. The water loss through latent heat was more sensitive to spring drought than to summer drought, while summer drought had negligible impact on LE. Waterlogging contributed to LE by enhancing its values during and after the waterlogged periods at the beginning of the growing season in a dry year, but lowering its value after the waterlogged periods in growing season.

Evapotranspiration of an Abandoned Grassland in the Italian Alps: Influence of Local Topography, Intra- and Inter-Annual Variability and Environmental Drivers

“…The bimodality (considering hourly data, Figure 7), was caused by the low values in the early morning and at sunset (when a low radiation forcing occurred) and by higher values when the photosynthesis was no more inhibited because of higher radiation input. The statistically significant inter-annual difference of LE confirmed, with another approach, the strong inter-annual differences found by [44,87,92]. The site LE bimodality differs from other studies, where it was interpreted as either a consequence of agricultural management [93] or changing soil water content conditions [94].…”

“…The precipitation pattern and soil water availability could also be important, as noted by [92]. At Cogne, however, this importance was not found.…”

Responses of soil N2O emissions and their abiotic and biotic drivers to altered rainfall regimes and co‐occurring wet N deposition in a semi‐arid grassland

“…Besides changes in precipitation amounts, climate models also predict that reduced or increased precipitation frequency—with or without modifications in the total precipitation amount—will occur over many terrestrial areas (Trenberth, 2011). Changes in precipitation frequency can lead to significant changes in ecological processes (e.g., Chen et al, 2019). In particular, they are expected to have large impacts on N cycling in arid and semi‐arid ecosystems (Borken & Matzner, 2009).…”

Decadal Changes in Soil Water Storage Characteristics Linked to Forest Management in a Steep Watershed

“…In fact, the most accurate direct measurements of hydrological characteristics are available only for rainfall and streamflows and rarely for evapotranspiration and water storage [1]. In any terrestrial ecosystem, rainfall is the largest flux term and main input of the water budget [2,3], thereby considered the major driving force of hydrological processes [4,5], particularly impacting the amounts of soil moisture [6] and surface water and groundwater resources [7]. Streamflow, on the other hand, is one of the output components of the water balance [8,9] and generally reflects water availability.…”