Retention of surface nitrate additions in a temperate old field: implications for atmospheric nitrogen deposition over winter and plant nitrogen availability

Abstract

In many temperate ecosystems, rates of atmospheric nitrogen deposition remain high over winter despite decreased agricultural activity over this season. The extent to which this nitrogen is accessible for plant growth over the following growing season may depend strongly on uptake by plants and soil microorganisms from late fall through early spring, when the majority of aboveground plant tissue has senesced. We added Ca( 15 NO 3 ) 2 (5 atom % 15 N) at a rate of 2 g m −2 of N (corresponding to 100 mg 15 N m −2 ) to the surface of plots in a temperate old field during either late fall, winter, spring melt or early spring. We quantified the recovery of excess 15 N in the soil microbial biomass and soil extracts following spring melt and in aboveground plant tissue at the peak of the plant growing season. Nitrate additions had no significant effect on total aboveground plant biomass, relative species abundance or percent tissue nitrogen. However, mean excess 15 N in aboveground plant tissue varied significantly among treatments, with values of 8.1, 2.6, 0.3 and 7.3 mg m −2 for late fall, winter, spring melt and early spring addition plots, respectively. Corresponding values of excess 15 N were 3.1, 1.4 and 0.2 mg m −2 in microbial biomass, and 0.17, 0.07 and 0.03 mg m −2 in soil extracts, for late fall, winter and spring melt addition plots, respectively. Overall, these results indicate that nitrogen retention from late fall through early spring may depend highly on plant uptake in this system, and that only a small fraction of the nitrogen that accumulates in the winter snow pack may be available to plants.

Nitrogen uptake by Carex aquatilis during the winter–spring transition in a low Arctic wet meadow

“…However, in some cases spring runoff may result in significant N losses, particularly when large volumes of water are flowing rapidly, where nitrate‐N is abundant, and where N is deposited on soil surfaces, i.e. by atmospheric deposition (Joseph & Henry 2008, 2009). With soil microbes in decline during the transition from winter to spring, the competitive ability of soil microbes for nutrient acquisition may be lower than it would be during the rest of the growing season, when turnover of N by microbes is relatively high despite low MB (Buckeridge & Jefferies 2007).…”

Fewer new species colonize at low frequency N addition in a temperate grassland

“…Bai et al 2010;Dickson et al 2014) or winter (e.g. Joseph & Henry 2009;Vourlitis 2012) with only a few additions per year. Thus, results from previous controlled experimental studies might lead to biased estimates of the effects of Nr deposition on the changes of community composition, due to excessively large and infrequent pulses of N added to ecosystems (Smith, Knapp & Collins 2009).…”

Vanishing winters in Germany: soil frost dynamics and snow cover trends, and ecological implications

“…Clein & Schimel 1995), but now these concepts have been extended to temperate regions (Campbell et al 2005). In particular, intense soil freezing can disrupt soil microbial activity (Yanai et al 2004, Bolter et al 2005, and damage plant roots , Weih & Karlsson 2002, leading to increased soil nitrogen leaching (Joseph & Henry 2009), increased soil trace gas losses , decreased plant productivity, and plant mortality (Schaberg et al 2008). Freezing can also affect soil physical processes directly by breaking up aggregates (Oztas & Fayetorbay 2003), and reducing water infiltration (Iwata et al 2010).…”