Does Mixing Tree Species Affect Water Storage Capacity of the Forest Floor? Laboratory Test of Pine-Oak and Fir-Beech Litter Layers

Anna Ilek,Marta Rajtar,Małgorzata Szostek,Anna Mikołajczyk

doi:10.3390/f12121674

Anna Ilek, Marta Rajtar + Show 2 more

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https://doi.org/10.3390/f12121674

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Abstract

During the last decade, tree species mixing has been widely supported as a silvicultural approach to reduce drought stress. However, little is known on the influence of tree species mixing on physical properties and the water storage capacity of forest soils (including the forest floor). Thus, the study aimed to analyze the effect of mixing pine needles and oak leaves and mixing fir needles and beech leaves on hydro-physical properties of the litter layer during laboratory tests. We used fir-beech and pine-oak litter containing various shares of conifer needles (i.e., 0, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90 and 100%) to determine the influence of the needle admixture on bulk density, total porosity, macroporosity, water storage capacity, the amount of water stored in pores between organic debris and the degree of saturation of mixed litter compared to broadleaf litter (oak or beech). We found that the admixture of fir needles increased the bulk density of litter from 7.9% with a 5% share of needles to 55.5% with a 50% share (compared to pure beech litter), while the share of pine needles < 40% caused a decrease in bulk density by an average of 3.0–11.0% (compared to pure oak litter). Pine needles decreased the water storage capacity of litter by about 13–14% with the share of needles up to 10% and on average by 28% with the 40 and 50% shares of pine needles in the litter layer. Both conifer admixtures reduced the amount of water stored in the pores between organic debris (pine needles more than fir needles).

Highlights

Recent research examining global climate changes indicates that drought conditions have increased globally in the last 40–50 years [1]
We calculated bulk density BD, total porosity TP, water storage capacity PK, macroporosity MP, the amount of water stored in pores between organic debris PW and the degree of saturation SW for each artificial litter sample
The admixture of fir needles increased the bulk density of litter from 7.9% with a 5% share of needles to 55.5% with a 50% share, while the share of pine needles < 40% caused a decrease in bulk density by an average of 3.0–11.0%

Summary

Introduction

Recent research examining global climate changes indicates that drought conditions have increased globally in the last 40–50 years [1]. In order to deal with drought effects, trees adopt numerous belowground strategies (e.g., root architecture and depth, root access to deep water) that likely interact with soil properties and soil biota [13,14,15]. For this reason, taking into account only the aboveground traits of trees without consideration for belowground traits and site conditions may lead to erroneous projections of drought consequences. Any generalization or theory needs to be based on a broad overview of the mixing reactions of functionally different tree species investigated in different mixing proportions, patterns and under different site conditions [16]

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