Fertilization and Tree Species Influence on Stable Aggregates in Forest Soil

Abstract

Background and objectives: aggregation and structure play key roles in the water-holding capacity and stability of soils and are important for the physical protection and storage of soil carbon (C). Forest soils are an important sink of ecosystem C, though the capacity to store C may be disrupted by the elevated atmospheric deposition of nitrogen (N) and sulfur (S) compounds by dispersion of soil aggregates via acidification or altered microbial activity. Furthermore, dominant tree species and the lability of litter they produce can influence aggregation processes. Materials and methods: we measured water-stable aggregate size distribution and aggregate-associated organic matter (OM) content in soils from two watersheds and beneath four hardwood species at the USDA Forest Service Fernow Experimental Forest in West Virginia, USA, where one watershed has received (NH4)2SO4 fertilizer since 1989 and one is a reference/control of similar stand age. Bulk soil OM, pH, and permanganate oxidizable carbon (POXC) were also measured. Research highlights: fertilized soil exhibited decreased macro-aggregate formation and a greater proportion of smaller micro-aggregates or unassociated clay minerals, particularly in the B-horizon. This shift in aggregation to soil more dominated by the smallest (<53 µm) fraction is associated with both acidification (soil pH) and increased microbially processed C (POXC) in fertilized soil. Intra-aggregate OM was also depleted in the fertilized soil (52% less OM in the 53–2000 µm fractions), most strongly in subsurface B-horizon soil. We also document that tree species can influence soil aggregation, as soil beneath species with more labile litter contained more OM in the micro-aggregate size class (<250 µm), especially in the fertilized watershed, while species with more recalcitrant litter promoted more OM in the macro-aggregate size classes (500–2000 µm) in the reference watershed. Conclusions: long-term fertilization, and likely historic atmospheric deposition, of forest soils has weakened macro-aggregation formation, with implications for soil stability, hydrology, and storage of belowground C.

Pulp and Paper Mill Sludge; a Soil Amendment and Compost option for Landfill Diversion for South-Africa

“…Estimation of soils resistance to erosion is referred to as 'erodability' of soil, based on its physical characteristics (Kemner and Adams, 2021). Primary factors affecting erodability are soil texture, organic matter content, structure and permeability.…”

“…Primary factors affecting erodability are soil texture, organic matter content, structure and permeability. Greater infiltration, organic matter and structure improve soils resistance to erosion (Kemner and Adams, 2021, Lawaal, 2009, Lal, 2015.…”

“…Vegetative cover directly relates to soil erosion. Vegetative cover that's minimal or absent have increased potential to erosion (Lawaal, 2009, Kemner andAdams, 2021). Vegetative cover allow for a degree of protection from rain drops and splashes, reduces speed of consequent runoff generated simultaneously allowing for greater infiltration (Lawaal, 2009).…”

“…Micro-aggregates are particles of silt and clay bound together, collections of micro-aggregates together with organic matter and other particles are known as macro-aggregates (Turgut and Kose, 2015). Secretions from microbial activity, plant roots and mycorrhizae are major factors in the formation of macro-aggregates (Kemner and Adams, 2021).…”

Fertilization and seasonality influence on the photochemical performance of tree legumes in forest plantation for area recovery in the Amazon

“…Studies have demonstrated the effects of fertilization on biomass growth during forest restoration with leguminous trees [21,22]. Fertilization effects may enhance the drought tolerance of species due to increased quantum yield [23,24]. A few studies have evaluated the combined effects of seasonality and fertilization on chlorophyll fluorescence.…”