Grassland productivity limited by multiple nutrients

Abstract

Terrestrial ecosystem productivity is widely accepted to be nutrient limited(1). Although nitrogen (N) is deemed a key determinant of aboveground net primary production (ANPP)(2,3), the prevalence of co-limitation by N and phosphorus (P) is increasingly recognized(4-8). However, the extent to which terrestrial productivity is co-limited by nutrients other than N and P has remained unclear. Here, we report results from a standardized factorial nutrient addition experiment, in which we added N, P and potassium (K) combined with a selection of micronutrients (K+μ), alone or in concert, to 42 grassland sites spanning five continents, and monitored ANPP. Nutrient availability limited productivity at 31 of the 42 grassland sites. And pairwise combinations of N, P, and K+μ co-limited ANPP at 29 of the sites. Nitrogen limitation peaked in cool, high latitude sites. Our findings highlight the importance of less studied nutrients, such as K and micronutrients, for grassland productivity, and point to significant variations in the type and degree of nutrient limitation. We suggest that multiple-nutrient constraints must be considered when assessing the ecosystem-scale consequences of nutrient enrichment.

Nitrogen and phosphorus co-limitation and grazing moderate nitrogen impacts on plant growth and nutrient cycling in sand dune grassland

“…Other low nutrient grasslands have shown a degree of NP co-limitation, with significantly greater above-ground biomass in NP treatments than in the control or with addition of N or P separately (Willems et al, 1993;Carroll et al, 2003). Across grasslands globally NP colimitation is widespread (Elser et al, 2007;Bracken et al, 2015;Fay et al, 2015). By contrast, in a Dutch study, N addition was reported to increase plant biomass in diverse chalk grassland, overriding any subtle P effects (Bobbink 1991), therefore not all calcareous grasslands are necessarily P limited.…”

Tight coupling of leaf area index to canopy nitrogen and phosphorus across heterogeneous tallgrass prairie communities

“…The Güsewell (2004) range for co-NP limitation 307 is broader than some ranges proposed by others (e.g., Koerselman and Meuleman 1996). 308 more common than previously thought (Fay et al 2015). This suggests that past narrow N: 310 P ratio ranges may have mistakenly predicted single nutrient limitation in some 311 communities that were co-limited.…”

“…LAI represents the 1-sided leaf surface area available 69 for photosynthesis, and variability in this metric strongly influences key ecosystem 70 functions such as productivity and transpiration (Street et al 2012 occurs. This may also apply to LAI-TFP (total foliar phosphorus) relationships in P-limited 95 or co-NP limited systems found in many grasslands (Fay et al 2015). Furthermore, in 96 herbaceous plant communities where the canopy makes up the majority of above ground 97 biomass, such relationships may allow estimates of aboveground stocks of N and P from 98 measurements of LAI, further providing data needed for process-based modelling.…”

“…biomass, but additions of N and P in concert results in greater productivity than N-addition 55 alone (Fay et al 2015). Soil N and P availability vary spatially and temporally according to 56 legacies of grazing and burning, as well as edaphic properties, topography, communitythrough selective grazing preferences and patchy nutrient additions across the landscape 60 (Johnson and Matchett 2001;Raynor et al 2015).…”

“…In many terrestrial ecosystems, primary production is limited by nutrients (Aerts 35 and Chapin 2000; Elser et al 2007), with limitation by nitrogen (N), phosphorus (P), or co-36 limitation by both N and P common in grasslands worldwide (Fay et al 2015). Both N and P 37 play central roles in photosynthesis and cellular function (Reich et decomposition, and hence carbon and nutrient cycling), an improved understanding linking 47 canopy leaf area and N and P distributions will facilitate predictions of ecosystem 48 productivity and other ecological functions.…”