Historical Forest Management Practices Influence Tree-Ring Based Climate Reconstructions

Georgios Skiadaresis,Willy Tegel,Bernhard Muigg

doi:10.3389/fevo.2021.727651

Georgios Skiadaresis, Willy Tegel + Show 1 more

Open Access

https://doi.org/10.3389/fevo.2021.727651

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Abstract

Tree-ring widths (TRW) of historical and archeological wood provide crucial proxies, frequently used for high-resolution multi-millennial paleoclimate reconstructions. Former growing conditions of the utilized trees, however, are largely unknown. Potential influences of historical forest management practices on climatic information, derived from TRW variability need to be considered but have not been assessed so far. Here, we examined the suitability of TRW series from traditionally managed oak forests (Quercus spp.) for climate reconstructions. We compared the climate signal in TRW chronologies of trees originating from high forests and coppice-with-standards (CWS) forests, a silvicultural management practice widely used in Europe for most of the common era. We expected a less distinct climate control in CWS due to management-induced growth patterns, yet an improved climate-growth relationship with TRW data from conventionally managed high forests. CWS tree rings showed considerably weaker correlations with hydroclimatic variables than non-CWS trees. The greatest potential for hydroclimate reconstructions was found for a large dataset containing both CWS and non-CWS trees, randomly collected from lumber yards, resembling the randomness in sources of historical material. Our results imply that growth patterns induced by management interventions can dampen climate signals in TRW chronologies. However, their impact can be minimized in well replicated, randomly sampled regional chronologies.

Highlights

Medieval societies in Europe developed the “Coppice-with-standards” (CWS) silvicultural system to ensure a sustainable supply with fuelwood and timber for the growing population
Four Tree-ring widths (TRW) chronologies were created based on datasets, which contained differing proportions of trees with periodic management-induced growth releases
In a CWS forest, the reduced competition for light, nutrients and water after periodic understory coppice causes an increased growth in the remaining standards, commonly referred to as release (Müllerová et al, 2016). The absence of such periodic and temporally aligned release events in the HF dataset suggests the absence of substantial alterations in the canopies or understories of target trees, indicative of growing conditions in a high forest (Nowacki and Abrams, 1997; Bergès et al, 2000)

Summary

Introduction

Medieval societies in Europe developed the “Coppice-with-standards” (CWS) silvicultural system to ensure a sustainable supply with fuelwood and timber for the growing population. This twostory forest structure combines an understory of even-aged coppice harvested in short rotation for fuelwood and tanning with an uneven-aged partial upper story of standard trees growing at wide spacing for timber production (Mosandl et al, 2010). The CWS forest management system was used all over medieval and early modern Europe (Short and Hawe, 2012) until it disappeared in most regions by the mid-twentieth century, when fossil fuels had replaced wood as the primary energy source and modern forestry focused primarily on timber production (Groß and Konold, 2010). A small region in southern Germany (Franconia) (Figures 1A,B) provides one of the few places left in central Europe, where traditional CWS forest stands are still maintained (Albrecht and Abt, 2014)

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