Different nitrogen saturation thresholds for above-, below-, and total net primary productivity in a temperate steppe

Yang, Guo-Jiao and Stevens, Carly and Zhang, Zi-Jia and Lü, Xiao-Tao and Han, Xing-Guo (2023) Different nitrogen saturation thresholds for above-, below-, and total net primary productivity in a temperate steppe. Global Change Biology, 29 (16). pp. 4586-4594. ISSN 1354-1013

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Identifying the thresholds for the positive responses of total net primary productivity (NPP) to nitrogen (N) enrichment is an essential prerequisite for predicting the benefits of N deposition on ecosystem carbon sequestration. However, the responses of below-ground NPP (BNPP) to N enrichment are unknown in many ecosystems, which limits our ability to understand the carbon cycling under the scenario of increasing N availability. We examined the changes in above-ground NPP (ANPP), BNPP, and NPP of a temperate meadow steppe across a wide-ranging N addition gradient (0, 2, 5, 10, 20, and 50 g N m -2  year -1 ) during 5 years. Both ANPP and NPP increased nonlinearly with N addition rates. The N saturation threshold for ANPP (T A ) and NPP (T N ) was at the rate of 13.11 and 6.70 g N m -2  year -1 , respectively. BNPP decreased with increasing N addition when N addition rates ˃5 g N m -2  year -1 , resulting in much lower T N than T A . Soil N enrichment played a key role in driving the negative impacts of high N addition rates on BNPP, and consequently on the earlier occurrence of N saturation threshold for NPP. Our results highlight the negative effects of soil N enrichment on NPP in natural grasslands super-saturated with N. Furthermore, by considering ANPP and BNPP simultaneously, our results indicate that previous findings from above-ground might have over-estimated the positive effects of N deposition on primary productivity.

Item Type:
Journal Article
Journal or Publication Title:
Global Change Biology
Uncontrolled Keywords:
?? soil n concentrationn saturation thresholdnitrogen depositionammonium toxicitysemi-arid grasslandproductionecologyglobal and planetary changeenvironmental science(all)environmental chemistry ??
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Deposited On:
20 Jul 2023 14:55
Last Modified:
31 Dec 2023 01:21