Water Budgets of Managed Forests in Northeast Germany under Climate Change—Results from a Model Study on Forest Monitoring Sites

Abstract

To develop measures to reduce the vulnerability of forests to drought, it is necessary to estimate specific water balances in sites and to estimate their development with climate change scenarios. We quantified the water balance of seven forest monitoring sites in northeast Germany for the historical time period 1961–2019, and for climate change projections for the time period 2010–2100. We used the LWF-BROOK90 hydrological model forced with historical data, and bias-adjusted data from two models of the fifth phase of the Coupled Model Intercomparison Project (CMIP5) downscaled with regional climate models under the representative concentration pathways (RCPs) 2.6 and 8.5. Site-specific monitoring data were used to give a realistic model input and to calibrate and validate the model. The results revealed significant trends (evapotranspiration, dry days (actual/potential transpiration < 0.7)) toward drier conditions within the historical time period and demonstrate the extreme conditions of 2018 and 2019. Under RCP8.5, both models simulate an increase in evapotranspiration and dry days. The response of precipitation to climate change is ambiguous, with increasing precipitation with one model. Under RCP2.6, both models do not reveal an increase in drought in 2071–2100 compared to 1990–2019. The current temperature increase fits RCP8.5 simulations, suggesting that this scenario is more realistic than RCP2.6.

Accurate Measurements of Forest Soil Water Content Using FDR Sensors Require Empirical In Situ (Re)Calibration

“…Most recalibrations or corrections are performed in the laboratory, since field-based calibration is challenging to perform for many users [10]. The RMSPE quality criteria set by [4] for a mean bias ± 0.02 m 3 m -3 and RMSE < 0.035 m 3 m -3 or a RMSE < 0.30 m 3 m -3 for forest soils by [18] are rarely met, even after (re)calibration or correction.…”

“…For forestry, soil water is of primary concern as an essential medium enabling movement of nutrients towards and within trees, strongly impacting their growth, yield and vitality over decades. Therefore, research sites in forests are often equipped with TDR or FDR soil moisture sensors for continuous water budget monitoring [18], although few calibration studies evaluated the trueness and precision of these sensors. Findings in forest soils were reported by Czarnomski et al [9] using a CS615 sensor, a former version of CS616, and Udawatta et al [15] tested the water dynamics with the CS616 for an agroforestry practice.…”

Changes in Terrestrial Evaporation across Poland over the Past Four Decades Dominated by Increases in Summer Months

“…For example, Great Britain is becoming warmer and wetter, through which increases in precipitation and air temperature are driving increases in runoff and evapotranspiration, as proven for 1961-2015 [16]. In Germany, significant trends were observed in transpiration and evapotranspiration in the period of 1961-2019 [17]. Over European Russia, positive trends in the annual values of potential evapotranspiration were revealed for 1966-2017, the distribution of which has a strong, patchy character [18].…”

Using stable water isotopes to understand ecohydrological partitioning under contrasting land uses in a drought‐sensitive rural, lowland catchment

“…The region of Brandenburg in NE Germany is one of the driest regions in central Europe and particularly vulnerable to droughts (Ziche et al, 2021). Previous studies in the region—and in particular during the 2018 drought—using monitoring and modelling of stable water isotopes to assess land use effects on water partitioning showed large land use impacts on water partitioning.…”