Long-term nitrogen and phosphorus enrichment alters vegetation species composition and reduces carbon storage in upland soil

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Type Article
Original languageEnglish
Pages (from-to)688-694
Number of pages7
JournalScience of the Total Environment
Volume593-594
Issue numberN/A
Early online date30 Mar 2017
DOI
Publication statusPublished - 01 Sep 2017
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Abstract

Reactive nitrogen (N) deposition can affect ecosystem processes, particularly in oligotrophic upland habitats. Phosphorus (P) addition has been proposed to reduce the effects of N enrichment on N leaching and acidification, since P limitation can reduce biomass production and consequent sequestration of reactive N. However, biodiversity is often reduced in more productive ecosystems and P limitation may protect against this effect. Responses to P availability in instances of high N deposition are poorly understood. This study investigated the ecosystem response to alleviation of P limitation, using a long-term nutrient addition experiment (1996–2012) three years after ceasing N inputs and 15 years after a single P application. Substantial differences were observed in the structure and composition of vegetation species and above-ground vegetation biomass. Vegetation height was greater in the N + P addition treatments (+ 38% cf. control), with increased cryptogam cover (+ 47%), whereas N addition increased graminoid species cover (+ 68%). Vegetation diversity was significantly reduced by the addition of P (− 21%), indicating that P limitation is likely to be an important mechanism that limits biodiversity loss in upland habitats exposed to chronic N deposition. Significant differences in soil C and N contents were also observed between treatments. Relative to control, the addition of N increased soil C (+ 11%) and N (+ 11%) pool sizes, whereas the addition of N and P reduced soil C (− 12%) and N (− 13%) pool sizes. This demonstrated the importance of P availability for upland ecosystem processes, and highlights the long-term effects of P addition on vegetation species composition and C storage. Thus, the addition of P cannot be endorsed as a method for reducing impacts of N deposition.

Capsule: Phosphorus limitation is a major mechanism governing ecosystem processes in situations of high atmospheric nitrogen deposition.

Keywords

  • nitrogen deposition, phosphorus limitation, mosses, vascular plants, soil carbon