The influence of riparian vegetation on leaf litter inputs to Boreal Shield streams: implications for partial-harvest logging in riparian reserves

Abstract

Litter inputs to headwater streams were measured to characterize and describe input patterns to the streams and to quantify the relationships between leaf litter inputs and surrounding riparian characteristics in Boreal Shield forests. Our goal was to provide information on litter inputs to streams in the Boreal Shield to determine if partial-harvest logging of commercial trees within riparian reserves has the potential to cause significant changes to litter inputs. Total leaf litter comprised 87% deciduous leaves and 13% conifer needles during the June to October periods. Commercial deciduous tree species accounted for approximately 50% of total deciduous leaf litter inputs. Distance-weighted deciduous basal area was the best predictor of overstorey deciduous litter (r 2 = 0.597, P = <0.001), indicating that the size, abundance, and proximity of deciduous trees to streams are important to deciduous litter inputs. Leaf litter inputs to Boreal Shield streams are strongly influenced by surrounding riparian vegetation and can be effectively predicted by stem basal area. A linear regression model based on commercial deciduous tree basal area is presented that can be useful to determine the number of trees to retain within a riparian area to maintain leaf litter inputs at or near preharvest levels.Résumé : Les apports de litière dans les cours d'eau de tête ont été mesurés pour caractériser et décrire le profil de ces apports dans les cours d'eau et quantifier les relations entre les apports de litière de feuilles et les caractéristiques riveraines environnantes dans les forêts du bouclier boréal. Notre but était de fournir de l'information au sujet des apports de litière dans les cours d'eau du bouclier boréal pour déterminer si une coupe partielle des tiges marchandes dans les bandes riveraines peut entraîner des changements significatifs dans les apports de litière. La litière de feuilles totale était composée de 87 % de feuilles d'essences feuillues et de 13 % d'aiguilles de conifères durant la période allant de juin à octobre. Les espèces feuillues marchandes représentaient approximativement 50 % de toute la litière de feuilles provenant d'essences feuillues. La surface terrière des essences feuillues pondérée par la distance était le meilleur prédicteur de la litière des essences feuillues de l'étage dominant (r 2 = 0,597, P = <0,001), ce qui signifie que la taille et l'abondance des arbres feuillus et leur proximité des cours d'eau sont des facteurs importants dans les apports de litière d'essences feuillues. Les apports de litière de feuilles dans les cours d'eau du bouclier boréal sont fortement influencés par la végétation riveraine environnante et on peut réussir à les prédire au moyen de la surface terrière des arbres. Un modèle de régression linéaire basé sur la surface terrière des essences feuillues marchandes est présenté. Ce modèle peut être utile pour déterminer combien d'arbres il faut conserver dans une zone riveraine pour maintenir les apports de litière de feuilles au même niveau ou pr...

An Ecological Approach to Riparian-Buffer Definition, and Implications for Timber Harvests in Nova Scotia, Canada

“…The particular importance of riparian trees is witnessed by the fact that sometimes riparian buffers are expressed in terms of tree height (Forest Ecosystem Management Assessment Team [FEMAT], 1993;Ilhardt et al, 2000;Young, 2000). A width of one tree height -ranging from 30 m in eastern North America to 50 m in the west -is estimated to provide most of the coarse woody debris and litter to the watercourse, enough shade to prevent significant warming of its water, and the root system necessary to stabilize its banks (FEMAT, 1993;Reid & Hilton, 1998;Young, 2000;Moore, Spittlehouse, & Story, 2005;Muto, Kreutzweiser, & Sibley, 2009) (Figure 2a). One tree height is consistent with reviews indicating that treed buffers on the order of 30 m are responsible for the majority of these riparian functions (Broadmeadow & Nisbet, 2004;Lee et al, 2004;Groom, Dent, Madsen, & Fleuret, 2011).…”

Costs and benefits of seven alternatives for riparian forest buffer management

“…Indeed, selective logging to promote broadleaved trees in mixed species buffer zones may actually improve ecological values as suggested by Lidman et al (2017b). Leaf litter inputs to headwater streams have been shown to correlate well with the basal area of broadleaved trees in the buffer zone (Muto et al 2009). Selective logging of conifer trees in mixed stands has the potential to increase the broadleaved basal area over time.…”

Woody debris dominates the exports of carbon and nitrogen from headwater streams in an alpine forest

“…Non‐woody debris can decay more rapidly in running water than in forests (Graça et al, 2015), and its decomposition rate increases with increasing temperature (Taylor & Chauvet, 2014), introducing more dissolved carbon and nitrogen into streams. As non‐woody debris enters a stream, it is often retained locally or is transported over a short distance until it is trapped around obstacles (Muto et al, 2009; Osei et al, 2015; Webster et al, 1999), such as root masses, instream wood or other woody debris. Hence, non‐woody debris is drawn into the water by flow and then submerged and accumulated around woody debris (Turowski et al, 2016) or buried within the streambed by sediment movement and flooding (Cornut et al, 2012), thus extending the residence time of the non‐woody debris and promoting the transformation of dissolved organic matter.…”