In:
Functional Ecology, Wiley, Vol. 30, No. 2 ( 2016-02), p. 305-313
Abstract:
Nitrogen ( N ) saturation hypothesis suggests that when an ecosystem reaches N ‐saturation, continued N input will cause increased N leaching, nitrous oxide ( N 2 O ) emission, and N mineralization and nitrification rates. It also suggests that a different element will become the main limiting factor when N saturation has been reached. Although this hypothesis has been tested in temperate forests, whether they can be directly applied to N ‐saturated tropical forests remain poorly addressed. To test this hypothesis, soil inorganic N , soil N mineralization and nitrification rate, soil N 2 O emission rate and nitrate ( ) leaching rate were measured in an N ‐saturated old‐growth tropical forest in southern C hina, after 6 years of N and P addition. We hypothesized that N addition would stimulate further N saturation, but P addition might alleviate N saturation. As expected, our results showed that six continuous years of experimental N addition did cause further N saturation, which was indicated by significant increases in soil inorganic N concentration, N 2 O emission and nitrate ( ) leaching. However, in contrast to our expectations, N addition significantly decreased in situ rates of net N mineralization and nitrification, which could be related to associated changes in enzyme activity and microbial community composition. On the other hand, P addition mitigated N saturation, as expected. Soil inorganic N concentration, N 2 O emission and leaching decreased significantly after P addition, but the net rates of N mineralization and nitrification were significantly increased. Our results provide a new understanding of the N saturation hypothesis, suggesting that the effects of long‐term N deposition on net N mineralization and nitrification rates in N‐saturated tropical forests can be negative and that P addition can alleviate N saturation in such tropical systems.
Type of Medium:
Online Resource
ISSN:
0269-8463
,
1365-2435
DOI:
10.1111/fec.2016.30.issue-2
DOI:
10.1111/1365-2435.12475
Language:
English
Publisher:
Wiley
Publication Date:
2016
detail.hit.zdb_id:
2020307-X
detail.hit.zdb_id:
619313-4
SSG:
12
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