Ecohydrological dynamics in the Alps: Insights from a modelling analysis of the spatial variability

Abstract

Mountain ecosystems are experiencing rapid warming resulting in ecological changes worldwide. Projecting the response of these ecosystems to climate change is thus crucial, but also uncertain due to complex interactions between topography, climate, and vegetation. Here, we performed numerical simulations in a real and a synthetic spatial domain covering a range of contrasting climatic conditions and vegetation characteristics representative of the European Alps. Simulations were run with the mechanistic ecohydrological model Tethys–Chloris to quantify the drivers of ecosystem functioning and to explore the vulnerability of Alpine ecosystems to climate change. We correlated the spatial distribution of ecohydrological responses with that of meteorological and topographic attributes and computed spatially explicit sensitivities of net primary productivity, transpiration, and snow cover to air temperature, radiation, and water availability. We also quantified how the variance in several ecohydrological processes, such as transpiration, quickly diminishes with increasing spatial aggregation, which highlights the importance of fine spatial resolution for resolving patterns in complex topographies. We conducted controlled numerical experiments in the synthetic domain to disentangle the effect of catchment orientation on ecohydrological variables, such as streamflow. Our results support previous studies reporting an altitude threshold below which Alpine ecosystems are water‐limited in the drier inner‐Alpine valleys and confirm that the wetter areas are temperature‐limited. High‐resolution simulations of mountainous areas can improve our understanding of ecosystem functioning across spatial scales. They can also locate the areas that are the most vulnerable to climate change and guide future measurement campaigns.

On the Spatio-Temporal Under-Representation of Isotopic Data in Ecohydrological Studies

“…Few isotope-based water uptake studies aiming at larger scales are existing at present. The methods used therein can be summarized as follows: (i) Upscaling through modeling approaches based on individual plants and/or small scale tracer-based analysis (e.g., Stumpp et al, 2012;Fatichi et al, 2016;Mastrotheodoros et al, 2019); (ii) Well-planned spatial and temporal sampling design (e.g., defining sampling transects or sampling grids, coverage of key species and different age groups, etc. ), complementing isotope analysis with ancillary monitoring such as soil moisture and sap flow dynamics (as auspicated by Jackisch et al, 2020) and upscaling via the isoscapes-approach (e.g., West et al, 2008;Bowen, 2010;West J.…”

More green and less blue water in the Alps during warmer summers

“…hydrometeorological products to generate high-resolution forcing (precipitation (P), air temperature, solar radiation, wind speed, and relative humidity; see Methods) to drive and validate the ecohydrological model Tethys-Chloris (T&C) 21 . The model resolves the water, carbon and energy budgets at the hourly time scale in a physically based and spatially explicit manner, accounting for lateral water transfer and topographic effects on radiation.…”

“…The model resolves the water, carbon and energy budgets at the hourly time scale in a physically based and spatially explicit manner, accounting for lateral water transfer and topographic effects on radiation. The model has been extensively validated in many regions worldwide 21,22,31 , including Alpine ecosystems 32 . To account for the high spatial heterogeneity of the region, we performed massively parallel simulations (6.1*10 5 CPU hours) at an unprecedented high resolution (250 m grid) for the entire Alpine arch (257,045 km 2 , 4.12 million pixels, Supplementary Fig.…”

Groundwater Buffers Drought Effects and Climate Variability in Urban Reserves

“…Model simulations were carried out using T&C (Fatichi et al, , ; Manoli et al, ; Mastrotheodoros et al, , ), which simulates essential components of the hydrological and carbon cycles, resolving energy, water, and carbon fluxes at the land surface. Meteorological inputs used for forcing T&C include rainfall, air temperature, relative humidity, wind speed, solar radiation, atmospheric pressure, cloud cover or longwave radiation, and atmospheric CO 2 concentration.…”