Changes in stable nitrogen and carbon isotope ratios of plants and soil across a boreal forest fire chronosequence

Recovery of nitrogen cycling in riparian zones after stream restoration using δ 15N along a 25-year chronosequence in northern Sweden

“…If this is the case, then %N of foliage in F. ulmaria and/or plant biomass should decrease with time. However, we found no significant change in %N in F. ulmaria or soil, nor did other studies of chronosequences in boreal systems (Hyodo et al 2013;Hu et al 2014). Instead, we found a negative quadratic relationship between the biomass of understory vegetation and time since restoration suggesting an initial pulse of N availability soon after restoration followed by decreasing N availability as indicated by a gradual decrease in understory vegetation 15 years after restoration.…”

“…The patterns in δ 15 N of foliage are broadly consistent with the development of decreasing N availability during succession that has been seen in other boreal chronosequences (DeLuca et al 2002;Hyodo et al 2013;Hu et al 2014). If this is the case, then %N of foliage in F. ulmaria and/or plant biomass should decrease with time.…”

“…After restoration, riparian zones were reconnected with the stream creating a new flooding regime and more suitable conditions for denitrification (Nilsson et al 2005), a process which can lead to δ 15 N enrichment of the remaing N pool through gaseous losses. Taken together, increased rates of mineralization and nitrification due to the disturbance of soils, potential for higher nitrate leaching as a result of reduced understory biomass and better conditions for denitrification all likely contributed to the high δ N values soon after wildfires followed by gradually decreasing values over decades to centuries (Hyodo et al 2013;Hu et al 2014). Although the majority of the literature on Ncycling in boreal chronosequences is based on terrestrial forests affected by fire, this is the primary natural disturbance agent in boreal forests and may provide insight into how these systems would react to most disturbances.…”

“…Studies of boreal forest fire chronosequences have reported high δ 15 N values soon after wildfires followed by gradually decreasing values over decades to centuries (Hyodo et al 2013;Hu et al 2014). While research on a riparian restoration chronosequence in California has found that while riparian forests strongly resembled remnant forests with respect to plant community composition (Holl and Crone 2004) and biomass (Matzek et al 2016) after less than 15 years, soil properties and components of nutrient cycling were much slower to change with time (Matzek et al 2016).…”

The interaction between nitrogen and phosphorous is a strong predictor of intra-plant variation in nitrogen isotope composition in a desert species

“…As a result, the variations in the relative abundance of 15 N to 14 N, quantified as δ 15 N, of plants contain rich information about these processes (Högberg, 1997;Robinson, 2001;Evans, 2001;Dawson et al, 2002). For this reason, δ 15 N is often considered an integrator of terrestrial N cycling, and numerous studies have analyzed natural variations in plant δ 15 N across disturbance and successional stages (e.g., Hobbie et al, 2000;Wang et al, 2007;Resco et al, 2011;Hyodo et al, 2013), climate and topoedaphic gradients (e.g., Austin and Sala, 1999;Schulze et al, 1998;Martinelli et al, 1999;Amundson et al, 2003;Craine et al, 2005Craine et al, , 2009Bai et al, 2009), species (e.g., Cernusak et al, 2009;Gubsch et al, 2011), and types of mycorrhizal fungi Hobbie and Hög-berg, 2012). Other studies have used δ 15 N as an indicator of relative N and phosphorus (P) availability and limitation on plant growth (McKee et al, 2002;Wigand et al, 2007;Inglett et al, 2007;Mayor et al, 2014).…”