Carbon and nitrogen accumulation within four black walnut alley cropping sites across Missouri and Arkansas, USA

Abstract

Agroforestry systems that integrate useful long-lived trees have been recognized for their potential in mitigating the accumulation of atmospheric fossil fuel-derived carbon (C). Black walnut (Juglans nigra) is frequently planted and cultivated in North America for its valuable lumber and edible nuts, and is highly amenable to the integration of understory crops or livestock in agroforestry systems. However, little is known about C content in black walnut trees, including the amounts of C assimilated into lignocellulosic tissues within different tree compartments. Therefore, allometric equations for above-and below-ground compartments of 10-year-old black walnut trees across diverse locations were developed. Ten grafted black walnut trees from each of four sites across the midwestern USA were destructively harvested for above-and below-ground biomass, and dry biomass weight (DW w), C (C w) and nitrogen (N; N w) stocks were quantified. Soils surrounding the harvested trees were sampled and analyzed for soil organic C (SOC) and total N (TN). Total DW w ranged from 27 to 54 kg tree-1 , with woody tissues containing an average of 467 g kg-1 C and 3.5 g kg-1 N. Woody tissues differed in C w and N w across location, and aboveground sections contained more C and less N compared with most root tissues. The slopes of the allometric equations did not differ significantly among locations, while intercepts did, indicating that trees only differed in initial size across locations. SOC and TN did not vary in distance from the trees, likely because the trees were not yet old enough to have impacted the surrounding soils. Our results establish a

Nitrogen dynamics in agroforestry systems. A review

“…In agroforestry systems, N sequestration, i.e., the long-term storage of N in soils, vegetation, and geological formations (Vogel et al 2014;Tian et al 2021;Zhang et al 2021), is active in biomass and soils. Sequestration of N in above- and belowground biomass varies depending on agroforestry type, tree species, location, and environment conditions, including soil properties and climatic condition (Gamble et al 2016(Gamble et al , 2020Dold et al 2019;Thomas et al 2020). In 4-yearold alley cropping systems consisting of four herbaceous perennial crops and two short-rotation woody crops in USA, aboveground biomass N pools ranged from 86 to 233 kg N ha −1 and fine root biomass N pools ranged from 2000 to 7200 kg N ha −1 (Gamble et al 2016(Gamble et al , 2020.…”

Evaluating tree growth factors into species-specific functional soil maps for improved agroforestry system efficiency

“…The diameter at breast height (i.e., 1.37 m above soil level) (DBH) of the trees in the study area were measured annually to represent the tree growth. The DBH was measured using steel dendrometer bands (Thomas et al 2020). The DBH of pecan trees was measured annually from 2004 to 2019, oak from 2005 to 2019, and of cottonwood and sycamore trees from 2016 to 2019.…”

Peer Review #2 of "Soil microbial diversity in organic and non-organic pasture systems (v0.2)"

“…Before plots were established, sheep grazed at approximately ~10 sheep ha-1 according to forage availability, which was seasonal and dependent on forage species present (Eremopyrum triticeum, Lolium perenne and other voluntary forbs and grasses). Details regarding the soil types of the study area are available in earlier publication from the research site (Thomas et al, 2008). The site received 101 cm rainfall in 2017 and 129 cm in 2018, with the 30-year (1987-2017) mean annual precipitation of 126 cm (Fig.…”