TY - JOUR

T1 - Dynamics and multi-annual fate of atmospherically deposited nitrogen in montane tropical forests

AU - Wang, Ang

AU - Chen, Dexiang

AU - Phillips, Oliver L.

AU - Gundersen, Per

AU - Zhou, Xulun

AU - Gurmesa, Geshere A.

AU - Li, Shanlong

AU - Zhu, Weixing

AU - Hobbie, Erik A.

AU - Wang, Xueyan

AU - Fang, Yunting

PY - 2021

Y1 - 2021

N2 - The effects of nitrogen (N) deposition on forests largely depend on its fate after entering the ecosystem. While several studies have addressed the forest fate of N deposition using N-15 tracers, the long-term fate and redistribution of deposited N in tropical forests remains unknown. Here, we applied N-15 tracers to examine the fates of deposited ammonium (NH4+) and nitrate (NO3-) separately over 3 years in a primary and a secondary tropical montane forest in southern China. Three months after N-15 tracer addition, over 60% of N-15 was retained in the forests studied. Total ecosystem retention did not change over the study period, but between 3 months and 3 years following deposition N-15 recovery in plants increased from 10% to 19% and 13% to 22% in the primary and secondary forests, respectively, while N-15 recovery in the organic soil declined from 16% to 2% and 9% to 2%. Mineral soil retained 50% and 35% of N-15 in the primary and secondary forests, with retention being stable over time. The total ecosystem retention of the two N forms did not differ significantly, but plants retained more 15NO3- than 15NH4+ and the organic soil more 15NH4+ than NO3-. Mineral soil did not differ in 15NH4+ and 15NO3- retention. Compared to temperate forests, proportionally more N-15 was distributed to mineral soil and plants in these tropical forests. Overall, our results suggest that atmospherically deposited NH4+ and NO3- is rapidly lost in the short term (months) but thereafter securely retained within the ecosystem, with retained N becoming redistributed to plants and mineral soil from the organic soil. This long-term N retention may benefit tropical montane forest growth and enhance ecosystem carbon sequestration.

AB - The effects of nitrogen (N) deposition on forests largely depend on its fate after entering the ecosystem. While several studies have addressed the forest fate of N deposition using N-15 tracers, the long-term fate and redistribution of deposited N in tropical forests remains unknown. Here, we applied N-15 tracers to examine the fates of deposited ammonium (NH4+) and nitrate (NO3-) separately over 3 years in a primary and a secondary tropical montane forest in southern China. Three months after N-15 tracer addition, over 60% of N-15 was retained in the forests studied. Total ecosystem retention did not change over the study period, but between 3 months and 3 years following deposition N-15 recovery in plants increased from 10% to 19% and 13% to 22% in the primary and secondary forests, respectively, while N-15 recovery in the organic soil declined from 16% to 2% and 9% to 2%. Mineral soil retained 50% and 35% of N-15 in the primary and secondary forests, with retention being stable over time. The total ecosystem retention of the two N forms did not differ significantly, but plants retained more 15NO3- than 15NH4+ and the organic soil more 15NH4+ than NO3-. Mineral soil did not differ in 15NH4+ and 15NO3- retention. Compared to temperate forests, proportionally more N-15 was distributed to mineral soil and plants in these tropical forests. Overall, our results suggest that atmospherically deposited NH4+ and NO3- is rapidly lost in the short term (months) but thereafter securely retained within the ecosystem, with retained N becoming redistributed to plants and mineral soil from the organic soil. This long-term N retention may benefit tropical montane forest growth and enhance ecosystem carbon sequestration.

KW - N-15 tracer

KW - ammonium and nitrate

KW - long&#8208

KW - term fate

KW - N deposition

KW - N retention and redistribution

KW - tropical montane forests

U2 - 10.1111/gcb.15526

DO - 10.1111/gcb.15526

M3 - Journal article

C2 - 33484031

VL - 27

SP - 2076

EP - 2087

JO - Global Change Biology

JF - Global Change Biology

SN - 1354-1013

IS - 10

ER -