Plant–bacteria–soil response to frequency of simulated nitrogen deposition has implications for global ecosystem change

Abstract

Atmospheric nitrogen (N) deposition, generally, has been simulated through a single or relatively few N applications per year for its ecological effect study. Despite the importance of timing in ecosystem processes, ecological experiments with more realistic N addition frequencies are rare. We employed a novel design with typical twice (2X) versus atypical monthly (12X) N applications per year to explore effects of N addition frequency on above‐ and below‐ground biodiversity and function. Each year, several response variables from either below‐ground or above‐ground growth, N status and cycling, or plant and bacterial diversity differed as a result of N addition frequency. BNPP showed a large frequency effect in the relatively moist year but not in the dry year. Nitrogen addition decreased root growth in the monthly relative to the biannual applications, which could be highly consequential for predicting changes in global carbon and nitrogen cycling. Simulated N deposition tended to perturb biodiversity, but it is noteworthy that 12X applications that spread N deposition more evenly through a year have much less negative impacts on plant and bacterial diversities than 2X amendments per year. Soil N mineralization rate in year 6 was much lower when N additions were monthly compared with a biannual amendment, especially when simulated N deposition was high. We have established that amendment frequency matters for understanding ecosystem response to N deposition. Experiments that more closely mimic the anthropogenic process of N deposition are needed to best assess ecosystem and potential global biogeochemical changes. A free Plain Language Summary can be found within the Supporting Information of this article.

Nitrogen addition stimulates soil aggregation and enhances carbon storage in terrestrial ecosystems of China: A meta‐analysis

“…Finally, we acknowledge that atmospheric N deposition is a chronic, low-dose input of N into ecosystems, whereas many N fertilization experiments use single, annual pulses. In particular, studies that explicitly manipulate the frequency of N addition find that responses to N enrichment are much weaker when N is applied as many doses over the course of the year, rather than as a single addition (Cao et al, 2019). This finding suggests that ecosystems respond very differently to chronic, low-dose versus high-pulse dose input of N. It is preferable that future studies could document similar patterns over N deposition gradients.…”

Responses of soil N2O emissions and their abiotic and biotic drivers to altered rainfall regimes and co‐occurring wet N deposition in a semi‐arid grassland

“…However, wet N deposition is tightly coupled with precipitation events (Boring et al, 1988) so that altering the precipitation pattern also modifies the temporal distribution of wet N deposition. Despite this, the response of N cycling to simulated N deposition is often studied based on a single or a series of N addition events over the course of a year (Cao, Pang, et al, 2020; Yue et al, 2019; Zhang, Lu, et al, 2014). The nature of the interaction between modified rainfall regimes and the co‐occurring wet N deposition and its effect on soil N 2 O emissions remains a gap in our knowledge.…”

Litter Management as a Key Factor Relieves Soil Respiration Decay in an Urban-Adjacent Camphor Forest under a Short-Term Nitrogen Increment

“…The anthropogenic input of reactive nitrogen (N) has increased 3-to 5-fold on a global scale [1], mainly through fossil-fuel burning and artificial nitrogen fertilizer applications [2]. The increased N input has led to many ecological effects in terrestrial ecosystems [3], such as soil acidification [4], nutrient imbalance [5], biodiversity loss [6,7], greenhouse gas emission [8], and global climate change [9]. In the subtropical forests of Southern China, N-saturated caused by elevated N deposition was usually quantified by nitrate leaching measurements [10].…”