期刊
SOIL SCIENCE AND PLANT NUTRITION
卷 64, 期 5, 页码 554-557出版社
TAYLOR & FRANCIS LTD
DOI: 10.1080/00380768.2018.1498286
关键词
Extracellular enzyme; lowland dipterocarp forest; nitrogen; phosphorus; phosphomonoesterase; tropics
资金
- MEXT [22255002]
- Sumitomo Foundation [153082]
- JSPS [B17K15289]
- [15K18712]
Previous meta-analyses revealed that the ratio of activities of carbon (C)-acquiring enzyme to nitrogen (N)-acquiring enzymes in tropical forest ecosystems was nearly identical to those in other ecosystems, despite of the N-rich condition in tropical forests. This could be explained by microbes in tropical forest soils, which require a large amount of N to produce N-rich acid phosphatase (AP) for catalyzation of the organic form of phosphorus (P) and compensation for poor P availability in soils. Based on this idea, we hypothesized that experimental P fertilization would reduce the allocation to N-acquiring enzymes compared with that of C-acquiring enzymes, i.e. that it would increase the ratios of activities of -1,4-glucosidase (BG) to -1,4-acetylglucosaminidase (NAG) and leucine aminopeptidase (LAP). We tested this hypothesis using an experimental fertilization site with factorial N (100kg ha(-1)yr(-1)) and P (50kg ha(-1)yr(-1)) addition in a primary tropical lowland forest in Bornean Malaysia, where our earlier work demonstrated that P fertilization reduced AP activity. Contrary to our hypothesis, the BG:NAG and BG:(NAG +LAP) ratios were not altered by either N or P fertilizations. This result indicated that AP production was not a reason for the maintenance of a relatively high investment in N-acquiring enzyme at our study site. Rather, NAG and LAP production was likely driven by C acquisition, rather than N acquisition, as the target substrates contained C as well as N. This idea was supported by the fact that neither the BG:NAG ratio nor the BG:(NAG +LAP) ratio was elevated by N addition. We propose that the ratios of activities of BG to NAG and LAP do not necessarily indicate the ratio of C:N acquisition, at least in our N-rich tropical forest ecosystem.
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