2017 ESA Annual Meeting (August 6 -- 11)

COS 28-8 - Responses of soil microbial community to a decade of high nitrogen inputs in tropical forests

Tuesday, August 8, 2017: 10:30 AM
E141, Oregon Convention Center
Xiankai Lu1,2, Cong Wang1, Jing Tian3, Kaijun Zhou1, Qinggong Mao1 and Jiangming Mo1, (1)South China Botanical Garden, Chinese Academy of Sciences, Guangzhou, China, (2)Department of Biology, Stanford University, Stanford, CA, (3)Institute of Geograpghic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing, China
Background/Question/Methods

Soil microorganisms play fundamental roles in nutrient cycling within forests ecosystems. With elevated anthropogenic nitrogen (N) deposition at a global scale, however, little is known on how long-term N deposition affects soil microbial community in tropical forest ecosystems as well as in ecosystems with different land-use history. To address this question, we expanded on a long-term N deposition experiment in three tropical forests that vary in land-use history (primary, secondary, and planted forests) in Southern China, with variable N additions as NH4NO3 of 0, 50, 100 and 150 kg N ha-1 yr-1 (above the background), respectively. Soil bacterial and fungal communities were studied using 16s rRNA genes pyrosequencing and the internal transcribed spacer (ITS) sequencing, respectively.

Results/Conclusions

(1) Fungi: Basidiomycota and Ascomycota were the dominant communities as the phylum level in all three forests (60-80% as relative abundance). The primary forest was the most diverse in terms of operational taxonomic units (OTUs). Non-metric multidimensional scaling analysis showed that the primary forest had significantly different community structures from that of the secondary and planted forests. However, a decade of N additions had no significant effects on fungal α-diversity (such as Shannon, chao1, observed species, and PD-whole-tree) for all three forests, although the dominant communities had different responses to long-term N additions, with an increasing abundance for Ascomycota in the primary forest and for Basidiomycotain the pine forest, but no changes in the secondary forest.

(2)Bacteria: Proteobacteria, Acidobacteria, and Actinobacteria were the dominant communities as the phylum level in the studied forests (70-80% as relative abundance).The total α-diversity were comparable among these forests, but non-metric multidimensional scaling analysis showed that the bacterial community structures were different between the primary and the secondary/planted forests. Similar to soil fungi, a decade of N additions had no significant effects on total α-diversity. However, the bacterial community structures were more sensitive to high N inputs in the primary forest than the other two, which generally showed no response to N inputs. Elevated N additions increased the abundances of Proteobacteria (mainly as Alphaproteobacteria and Gammaproteobacteria) and Actinobacteria, but decreased the abundance in Acidobacteria in the primary forest.

These findings suggested that long-term N deposition could alter soil microbial community structures rather than total biodiversity, and the primary forest was more sensitive to high N inputs than the secondary and planted forests. Soil acidification played an important role on changing microbial community structures in the primary forest.