Are riparian buffers surrounding forestry-impacted streams sufficient to meet key ecological objectives? A Swedish case study

Darshanaa Chellaiah,Lenka Kuglerová

doi:10.1016/j.foreco.2021.119591

Darshanaa Chellaiah, Lenka Kuglerová

Open Access

https://doi.org/10.1016/j.foreco.2021.119591

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Abstract

In many national guidelines and policies regarding protection of freshwater systems from stressors associated with forestry, riparian buffer width is a commonly prescribed strategy, typically with no other refinements of protection measures. In Sweden, the Strategic Management Objectives (SMOs) were developed to ensure that riparian buffers that are left after harvesting sustain important ecosystem attributes in aquatic systems, referred to as objectives, namely shading, biodiversity, reduction of sedimentation, and provision of deadwood and food. However, little specification is given on threshold targets or how to manage riparian zones to effectively provide these objectives. In this paper, we evaluated whether existing riparian buffers of different widths along small, recently harvested (<8 years) streams were able to provide proxies of these targeted objectives, and further compared harvested streams to counterparts situated in mature unharvested production forests (reference) in northern and southern Sweden. The influence of buffer width varied with objective and geographic location. In both regions, canopy cover (proxy for shading) increased with riparian width, and riparian deadwood was highest in no buffer sites. Organic matter (OM; proxy for food) was highest in the northern no buffer streams, while in the south OM increased with buffer width. All other parameters tested had no relationship to buffer width. These differing responses even in streams subjected to similar land-use and management within a close vicinity and region, suggest that the contemporary strategy of prescribing fixed buffer widths and/or stating objectives without defined guidelines for what constitutes an effective riparian buffer is insufficient given the large variability of stream ecosystems across small spatial scales. More comprehensive consideration synergistically accounting for site-specificity and land mosaic planning are needed to develop functionally effective buffers that can mitigate forestry impacts on stream ecosystems.

Highlights

Riparian zones are vital to regulate ecological functions and con nections between terrestrial and aquatic environments (Naiman and and Decamps, 1997; Richardson and Sato, 2015)
In this paper we investigate the ability of riparian buffer width to mitigate forestry impacts on headwater ecosystems compared to un harvested, mature and managed production forests
We note that variation in stream, riparian and catchment-scale conditions can influ ence measured parameters tested in this study, we focused on buffer width as an explanatory variable in our analyses, rather than on a suite of physicochemical effects reported elsewhere (Burrows et al, 2017; Jonsson et al, 2017; Lidman et al, 2017) given that buffer width is a common one-size-fit-all strategy to mitigate land-use change impacts

Summary

Introduction

Riparian zones are vital to regulate ecological functions and con nections between terrestrial and aquatic environments (Naiman and and Decamps, 1997; Richardson and Sato, 2015). They are important habi tats for maintaining biodiversity, regulating sediment and nutrient transport and providing shading and resource subsidies for organisms (Chellaiah and Yule, 2018; Moore et al, 2018). As small streams represent 70–80% of total river network length in forested regions (Ågren et al, 2015) and provide water, energy, biogeochemical constituents and biodiversity to downstream ecosystems (Moore et al, 2018; Coats and Jackson, 2020), improper riparian management surrounding small streams can signifi cantly alter ecology at local and whole-catchment scales

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