Groundwater extraction reduces tree vitality, growth and xylem hydraulic capacity in Quercus robur during and after drought events

Georgios Skiadaresis,Jürgen Bauhus,Kerstin Stahl,Julia Schwarz

doi:10.1038/s41598-021-84322-6

Georgios Skiadaresis, Jürgen Bauhus + Show 2 more

Open Access

https://doi.org/10.1038/s41598-021-84322-6

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Journal: Scientific Reports	Publication Date: Mar 4, 2021
Citations: 12	License type: open-access

Affiliation: University of Freiburg

Abstract

Climate change is expected to pose major direct and indirect threats to groundwater-dependent forest ecosystems. Forests that concurrently experience increased rates of water extraction may face unprecedented exposure to droughts. Here, we examined differences in stem growth and xylem hydraulic architecture of 216 oak trees from sites with contrasting groundwater availability, including sites where groundwater extraction has led to reduced water availability for trees over several decades. We expected reduced growth and xylem hydraulic capacity for trees at groundwater extraction sites both under normal and unfavourable growing conditions. Compared to sites without extraction, trees at sites with groundwater extraction showed reduced growth and hydraulic conductivity both during periods of moderate and extremely low soil water availability. Trees of low vigour, which were more frequent at sites with groundwater extraction, were not able to recover growth and hydraulic capacity following drought, pointing to prolonged drought effects. Long-term water deficit resulting in reduced CO2 assimilation and hydraulic capacity after drought are very likely responsible for observed reductions in tree vitality at extraction sites. Our results demonstrate that groundwater access maintains tree function and resilience to drought and is therefore important for tree health in the context of climate change.

Highlights

Climate change is expected to pose major direct and indirect threats to groundwater-dependent forest ecosystems
We selected an equal number of declining and healthy trees per stand for wood anatomical measurements, the distribution of trees among vigour classes differed across sites with varying groundwater availability (Table 1)
The strong positive correlations observed between Ring width (RW) and average soil moisture anomaly index (SMI) for the period from March to August or individual months of the vegetation period indicate that radial growth of oaks was strongly controlled by soil water availability during the whole vegetation period

Summary

Introduction

Climate change is expected to pose major direct and indirect threats to groundwater-dependent forest ecosystems. Groundwater extraction rates for agricultural, industrial and domestic uses will most certainly increase during more frequent and intense drought events in future[17,18,19] This combination of direct and indirect effects of climate change will expose these forest ecosystems to potentially dramatic decreases in water a vailability[15]. We lack an understanding of the mechanisms that underlie this impaired growth performance at the species level This is essential to explain observed declines in tree vitality and identify populations most vulnerable to climate c hange[21,22,23,24]

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Conclusion