Effects of Climate and Atmospheric Nitrogen Deposition on Early to Mid-Term Stage Litter Decomposition Across Biomes

Abstract

Litter decomposition is a key process for carbon and nutrient cycling in terrestrial ecosystems and is mainly controlled by environmental conditions, substrate quantity and quality as well as microbial community abundance and composition. In particular, the effects of climate and atmospheric nitrogen (N) deposition on litter decomposition and its temporal dynamics are of significant importance, since their effects might change over the course of the decomposition process. Within the TeaComposition initiative, we incubated Green and Rooibos teas at 524 sites across nine biomes. We assessed how macroclimate and atmospheric inorganic N deposition under current and predicted scenarios (RCP 2.6, RCP 8.5) might affect litter mass loss measured after 3 and 12 months. Our study shows that the early to mid-term mass loss at the global scale was affected predominantly by litter quality (explaining 73% and 62% of the total variance after 3 and 12 months, respectively) followed by climate and N deposition. The effects of climate were not litter-specific and became increasingly significant as decomposition progressed, with MAP explaining 2% and MAT 4% of the variation after 12 months of incubation. The effect of N deposition was litter-specific, and significant only for 12-month decomposition of Rooibos tea at the global scale. However, in the temperate biome where atmospheric N deposition rates are relatively high, the 12-month mass loss of Green and Rooibos teas decreased significantly with increasing N deposition, explaining 9.5% and 1.1% of the variance, respectively. The expected changes in macroclimate and N deposition at the global scale by the end of this century are estimated to increase the 12-month mass loss of easily decomposable litter by 1.1–3.5% and of the more stable substrates by 3.8–10.6%, relative to current mass loss. In contrast, expected changes in atmospheric N deposition will decrease the mid-term mass loss of high-quality litter by 1.4–2.2% and that of low-quality litter by 0.9–1.5% in the temperate biome. Our results suggest that projected increases in N deposition may have the capacity to dampen the climate-driven increases in litter decomposition depending on the biome and decomposition stage of substrate.

Nitrogen increases early‐stage and slows late‐stage decomposition across diverse grasslands

“…Mean annual temperature, precipitation variability and atmospheric N deposition all contributed to variation in decomposition rates across sites, mostly later in decomposition. Faster decomposition in warmer sites, observed previously in global decomposition syntheses (Gholz et al, 2000;Kwon et al, 2021;Zhang et al, 2008), is expected because of greater biological activity, longer growing seasons and higher nutrient availability. Greater photodegration in warmer sites could also have contributed to faster decomposition in those sites, given that MAT was highly correlated with annual insolation (Austin & Vivanco, 2006).…”

“…Positive relationships between k s and N deposition provide further evidence that N limits decomposition across grasslands, and contrast results from a cross‐site study of tea leaf decomposition world‐wide, which showed negative relationships between atmospheric N deposition and mass loss over 3 and 12 months in temperate sites (Kwon et al, 2021). The effects of N from deposition and fertilizer differed in key ways.…”

“…Initial decomposition rates varied widely among sites, but in ways not explained by measured site climate or edaphic factors. Decomposition of common above-ground substrates was similarly unrelated to climate factors across six grassland sites in the US Central Great Plains (Bontti et al, 2009), and a cross-sites study of decomposing tea leaves similarly found a high percentage of unexplained variation across grassland sites (Kwon et al, 2021). What other factors might have contributed to variation in initial decomposition across sites?…”

Climate change, human health, and the exposome: Utilizing OMIC technologies to navigate an era of uncertainty

“…It is believed that rising temperatures lead to the geographical expansion of many species of weeds ( 27 ). Higher CO 2 concentration is also believed to increase weed severity and herbicide resistance due to the CO 2 -enhanced fertilizing effect and water use of weeds compared to other crops ( 28 , 29 ).…”

Elevated Nitrogen Deposition to Fire‐Prone Forests Adjacent to Urban and Agricultural Areas, Colorado Front Range, USA

“…Nr deposition and wildfires can interact in a number of ways. First, chronically elevated Nr deposition can increase the susceptibility of an ecosystem to wildfire by increasing biomass and the thickness of the litter layer, and by increasing vulnerability to drought stress (Green et al., 2013; Grulke et al., 2008; Kwon et al., 2021). Second, wildfires themselves are large sources of Nr emissions and subsequent deposition, with the magnitude and form of Nr emissions dependent on both fuel and combustion conditions (Benedict et al., 2017; Johnson et al., 1998; Lindaas, Pollack, Calahorrano, et al., 2021; Lindaas, Pollack, Garofalo, et al., 2021).…”