Recovery from disturbance requires resynchronization of ecosystem nutrient cycles

Abstract

Abstract. Nitrogen (N) and phosphorus (P) are tightly cycled in most terrestrial ecosystems, with plant uptake more than 10 times higher than the rate of supply from deposition and weathering. This near-total dependence on recycled nutrients and the stoichiometric constraints on resource use by plants and microbes mean that the two cycles have to be synchronized such that the ratio of N:P in plant uptake, litterfall, and net mineralization are nearly the same. Disturbance can disrupt this synchronization if there is a disproportionate loss of one nutrient relative to the other. We model the resynchronization of N and P cycles following harvest of a northern hardwood forest. In our simulations, nutrient loss in the harvest is small relative to postharvest losses. The low N:P ratio of harvest residue results in a preferential release of P and retention of N. The P release is in excess of plant requirements and P is lost from the active ecosystem cycle through secondary mineral formation and leaching early in succession. Because external P inputs are small, the resynchronization of the N and P cycles later in succession is achieved by a commensurate loss of N. Through succession, the ecosystem undergoes alternating periods of N limitation, then P limitation, and eventually co-limitation as the two cycles resynchronize. However, our simulations indicate that the overall rate and extent of recovery is limited by P unless a mechanism exists either to prevent the P loss early in succession (e.g., P sequestration not stoichiometrically constrained by N) or to increase the P supply to the ecosystem later in succession (e.g., biologically enhanced weathering). Our model provides a heuristic perspective from which to assess the resynchronization among tightly cycled nutrients and the effect of that resynchronization on recovery of ecosystems from disturbance.

Responses of a tundra system to warming using SCAMPS: a stoichiometrically coupled, acclimating microbe–plant–soil model

“…1) draws from the soil microbial C and N limitation model of Schimel and Weintraub (2003), the microbial physiology in response to warming model of Allison et al (2010), the tundra soil organic C (SOC) model of Moorhead and Reynolds (1993), and the resource optimization model of Rastetter et al (1997Rastetter et al ( , 2001Rastetter et al ( , 2013. The model is driven by soil temperature (8C) and allows inputs of DON and DOC from outside the system, which were set to 0 in our simulations.…”

“…We assume 98% of each nutrient is available for microbial or plant uptake at a given time step (parameter C). Uptake is driven by a resource optimization scheme for plants developed by Rastetter et al (Rastetter 2011, Rastetter et al 2013. We assume that the microbes continuously adjust the allocation of uptake assets (uptake enzymes, energy expenditure, and other assets) to optimize the relative rates of resource acquisition to meet their stoichiometric needs.…”

“…We assume that the microbes continuously adjust the allocation of uptake assets (uptake enzymes, energy expenditure, and other assets) to optimize the relative rates of resource acquisition to meet their stoichiometric needs. These uptake assets are represented in the model by an abstract variable we call ''effort'' (Ef i [Rastetter et al 2013]). The subscript ''i'' represents the resources DOC, DON, or NH 4 þ .…”

Modeling long‐term changes in tundra carbon balance following wildfire, climate change, and potential nutrient addition

“…Although effects of N and P additions have been examined in field studies, most studies either conducted a single treatment (Shaver and Chapin 1980, Wookey et al 1995, Robinson et al 1998 or put extremely high factorial N and P additions (e.g., Henry et al 1986, Shaver andChapin 1995). To constrain these uncertainties and investigate the underlying mechanisms that control long-term recovery of tundra ecosystems from disturbance, this study employed the multiple element limitation (MEL) model (Rastetter et al 2013, Jiang et al 2015a, Pearce et al 2015 to simulate long-term C and nutrient cycles along a burn severity gradient of the Anaktuvuk River fire scar with varied future climate scenarios. To constrain these uncertainties and investigate the underlying mechanisms that control long-term recovery of tundra ecosystems from disturbance, this study employed the multiple element limitation (MEL) model (Rastetter et al 2013, Jiang et al 2015a, Pearce et al 2015 to simulate long-term C and nutrient cycles along a burn severity gradient of the Anaktuvuk River fire scar with varied future climate scenarios.…”

System dynamics modeling of the influence of the TN/TP concentrations in socioeconomic water on NDVI in shallow lakes

“…Unprecedented water usage, sewage, and other human activities affect the water quality . For example, the nutrients mainly originating from socioeconomic water, such as the total nitrogen (TN) and the total phosphorus (TP) in the water body, affect the ecosystem status (Rastetter et al, 2013;Garnier et al 2005;Zhao et al, 2013). Meanwhile, water pollution, coupled with water shortage, has made the intensive conflicts over water resources between human and ecosystems Yang et al, 2013).…”