Leaf Litter Decomposition and Nutrient-Release Characteristics of Several Willow Varieties Within Short-Rotation Coppice Plantations in Saskatchewan, Canada

Abstract

Abstract:Quantifying short-rotation coppice (SRC) willow leaf litter dynamics will improve our understanding of carbon (C) sequestration and nutrient cycling potentials within these biomass energy plantations and provide valuable data for model validation. The objective of this study was to quantify the decomposition rate constants (kBiomass) and decomposition limit values (LVBiomass), along with associated release rates (kNutrient) and release limits (LVNutrient) of nitrogen (N), phosphorus (P), potassium (K), sulphur (S), calcium (Ca), and magnesium (Mg) of leaf litter from several native and exotic willow varieties during an initial four-year rotation at four sites within Saskatchewan, Canada. The kBiomass, LVBiomass, kNutrient, and LVNutrient values varied among the willow varieties, sites, and nutrients, with average values of 1.7 year-1, 79 %, 0.9 year-1, and 83 %, respectively. Tissue N had the smallest kNutrient and LVNutrient values, while tissue K and Mg had the largest kNutrient and LVNutrient values, respectively. The leaf litter production varied among willow varieties and sites with an average biomass accumulation of 7.4 Mg ha-1 after the four-year rotation and associated C sequestration rate of 0.2 Mg C ha-1 yr-1. The average contribution of nutrients released from leaf litter decomposition during the four-year rotation to the plant available soil nutrient pool across varieties and sites was 22, 4, 47, 10, 112, and 18 kg ha-1 of N, P, K, S, Ca, and Mg, respectively. Principal component analysis identified numerous key relationships between the measured soil, plant tissue, climate and microclimate variables and observed willow leaf litter decomposition and nutrient release characteristics. Our findings support the contention that SRC willow leaf litter is capable of enhancing both soil organic C levels and supplementing soil nutrient availability over time. Powered by Editorial Manager® and ProduXion Manager® from Aries Systems Corporation

First Rotation Biomass Production and Nutrient Cycling within Short-Rotation Coppice Willow Plantations in Saskatchewan, Canada

“…Based on the litterbag results, the leaf litter cohorts considered in our nutrient budget 23 calculations during the rotation were nutrient release from: three years of establishment year leaf litter 24 (i.e., pre-coppice leaf biomass); two years of first year post-coppice leaf litter; and, one year from the 25 second year post-coppice leaf litter. The remaining nutrient release contributions from the first to third 26 year post-coppice leaf litter were associated with the second rotation [44]. 27…”

“…The subsamples were then thoroughly milled and homogenized prior 27 to analyzing for N, P, K, S, Ca, and Mg contents of the biomass removed from the site. Total N, P, K, 28 Estimates of annual nutrient output from the plant available soil nutrient pool through accumulated leaf 4 litter nutrients at each site were taken from Hangs et al [44]. In a separate companion study, Stadnyk 5 [107] measured the fine and coarse root biomass of all varieties at each site and these values were 6 supplemented with relative biomass proportions among stems, stool, and fine/coarse root fractions 7 reported in the literature [41,95], to estimate the annual below-ground biomass within each plantation 8 throughout the rotation.…”

“…Consequently, litterbags were used to 19 measure the rate of leaf litter decomposition and nutrient release throughout the rotation. Using the 20 estimated nutrient release rate constants and accumulated leaf litter biomass over the four-year 21 rotation, the contribution of leaf litter nutrient release to the plant available soil nutrient pools were 22 calculated [44]. Based on the litterbag results, the leaf litter cohorts considered in our nutrient budget 23 calculations during the rotation were nutrient release from: three years of establishment year leaf litter 24 (i.e., pre-coppice leaf biomass); two years of first year post-coppice leaf litter; and, one year from the 25 second year post-coppice leaf litter.…”

“…The average leaf litter 17 nutrient content among the willow varieties and sites was 80.8, 14.6, 108.1, 24.5, 255.7, and 41.2 kg 18 ha -1 of N, P, K, S, Ca, and Mg, respectively [44]. Additional sinks of plant available soil nutrients 19 included the below-ground willow biomass that consisted of stools and fine and coarse roots, which 20 were 1.2, 10.5, 0.8 Mg ha -1 , respectively, after the initial four-year rotation among willow varieties and 21 sites, with the trend in nutrient immobilization related to the relative biomass of these below-ground 22 tissues (Table 6).…”

“…The following soil analyses were originally reported in Hangs et al [44]. After planting the willow 10 varieties at each site, three 60 cm soil cores (2 cm diameter) were collected within each varietal plot 11 using a JMC backsaver probe (Model PN001; Clements Assoc.…”