Small-Scale Forest Structure Influences Spatial Variability of Belowground Carbon Fluxes in a Mature Mediterranean Beech Forest

Ettore D’Andrea,Andrea Scartazza,Paolo De Angelis,Giorgio Matteucci,Gabriele Guidolotti

doi:10.3390/f11030255

Abstract

The tree belowground compartment, especially fine roots, plays a relevant role in the forest ecosystem carbon (C) cycle, contributing largely to soil CO2 efflux (SR) and to net primary production (NPP). Beyond the well-known role of environmental drivers on fine root production (FRP) and SR, other determinants such as forest structure are still poorly understood. We investigated spatial variability of FRP, SR, forest structural traits, and their reciprocal interactions in a mature beech forest in the Mediterranean mountains. In the year of study, FRP resulted in the main component of NPP and explained about 70% of spatial variability of SR. Moreover, FRP was strictly driven by leaf area index (LAI) and soil water content (SWC). These results suggest a framework of close interactions between structural and functional forest features at the local scale to optimize C source–sink relationships under climate variability in a Mediterranean mature beech forest.

Highlights

Terrestrial ecosystems, especially forests, have an active role in the global carbon (C) cycle: forests cover about 4.2 × 103 Mha of the earth’s land surface, accounting for about 45% of terrestrial carbon and contributing to about 50% of terrestrial net primary production (NPP) [1]
The commonality analysis suggested that 44% of the whole variability was affected by the pure effect of leaf area index (LAI), 20% related to soil water content (SWC), and 36% was affected by the joint effect of the two predictors
Our results indicate that FRPY is mainly dependent on LAI, which represents a proxy of ecosystem productivity and ground coverage [41,42]

Summary

Introduction

Terrestrial ecosystems, especially forests, have an active role in the global carbon (C) cycle: forests cover about 4.2 × 103 Mha of the earth’s land surface, accounting for about 45% of terrestrial carbon and contributing to about 50% of terrestrial net primary production (NPP) [1]. As we are following the climatic scenario characterized by the highest variations [2], forests play a crucial role to mitigate global climatic change by removing 2.4 ± 0.4 Pg C y−1 from the atmosphere through growth [3]. This amount corresponds up to 30% of anthropogenic CO2 emissions from fossil fuel burning and deforestation [4]; it is evident how changes in the productivity of the forest ecosystem affects the C-cycle. Fine root production (FRP) plays a relevant role on NPP at both ecosystem and global levels accounting for up to 67% and 22% of NPP, respectively [7,8]

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