Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N Status
Elevated nitrogen (N) deposition may further acidify soils in tropical forests. Yet, we have limited evidence on this prediction and it remained unclear how this would affect fine root growth therein. Here, we report responses of fine root biomass, vitality, and chemistry, as well as related soil pa...
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MDPI AG
2022-08-01
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| Series: | Forests |
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| author | Feifei Zhu Frank S. Gilliam Jan Mulder Muneoki Yoh Jiangming Mo Xiankai Lu |
| author_facet | Feifei Zhu Frank S. Gilliam Jan Mulder Muneoki Yoh Jiangming Mo Xiankai Lu |
| author_sort | Feifei Zhu |
| collection | DOAJ |
| description | Elevated nitrogen (N) deposition may further acidify soils in tropical forests. Yet, we have limited evidence on this prediction and it remained unclear how this would affect fine root growth therein. Here, we report responses of fine root biomass, vitality, and chemistry, as well as related soil parameters to eight years of N additions in three tropical forests different in initial soil N status, with one primary forest being N-saturated, and another two younger forests (one secondary forest and one planted forest) less N-rich. Results showed that in the primary forest, fine root biomass decreased and fine root necromass increased following N addition, resulting in lower live fine root proportion (fine root vitality). Declining fine root vitality was associated with fine root Fe accumulation and soil acidification indicated by regression analysis. These alterations of fine root growth and chemistry co-occurred with soil pH decline, soil exchangeable Fe<sup>3+</sup> mobilization, exchangeable Ca<sup>2+</sup>, and Mg<sup>2+</sup> depletion after N treatments in the primary forest. In contrast, N addition only elevated fine root K, Al, and Fe content in the secondary forest. In the planted forest, moderate but significant decreases in soil pH, soil exchangeable K<sup>+</sup>, and Mg<sup>2+</sup> were found after N treatment, with fine root biomass negatively correlated with soil exchangeable Al<sup>3+</sup> and Al<sup>3+</sup>/(Ca<sup>2+</sup> + Mg<sup>2+</sup>) ratio. Our results suggested that long-term N fertilization may negatively affect fine root growth, via severed soil acidification, Fe mobilization, and base cation depletion in highly acidified, N-saturated primary tropical forests. Initial forest N status, influenced by different land-use history, mediates N deposition effects on fine root growth. |
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| language | English |
| last_indexed | 2024-03-09T04:26:11Z |
| publishDate | 2022-08-01 |
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| spelling | doaj.art-cd3dd4418d6046178f46c808624ceb6f2023-12-03T13:41:14ZengMDPI AGForests1999-49072022-08-01138132810.3390/f13081328Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N StatusFeifei Zhu0Frank S. Gilliam1Jan Mulder2Muneoki Yoh3Jiangming Mo4Xiankai Lu5CAS Key Laboratory of Forest Ecology and Management, Institute of Applied Ecology, Chinese Academy of Sciences, Shenyang 110016, ChinaDepartment of Biology, University of West Florida, Pensacola, FL 32514, USAFaculty of Environmental Sciences and Natural Resource Management, Norwegian University of Life Sciences, N-1432 Aas, NorwayInstitute of Agriculture, Tokyo University of Agriculture and Technology, Tokyo 183 0059, JapanKey Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, ChinaKey Laboratory of Vegetation Restoration and Management of Degraded Ecosystems, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, ChinaElevated nitrogen (N) deposition may further acidify soils in tropical forests. Yet, we have limited evidence on this prediction and it remained unclear how this would affect fine root growth therein. Here, we report responses of fine root biomass, vitality, and chemistry, as well as related soil parameters to eight years of N additions in three tropical forests different in initial soil N status, with one primary forest being N-saturated, and another two younger forests (one secondary forest and one planted forest) less N-rich. Results showed that in the primary forest, fine root biomass decreased and fine root necromass increased following N addition, resulting in lower live fine root proportion (fine root vitality). Declining fine root vitality was associated with fine root Fe accumulation and soil acidification indicated by regression analysis. These alterations of fine root growth and chemistry co-occurred with soil pH decline, soil exchangeable Fe<sup>3+</sup> mobilization, exchangeable Ca<sup>2+</sup>, and Mg<sup>2+</sup> depletion after N treatments in the primary forest. In contrast, N addition only elevated fine root K, Al, and Fe content in the secondary forest. In the planted forest, moderate but significant decreases in soil pH, soil exchangeable K<sup>+</sup>, and Mg<sup>2+</sup> were found after N treatment, with fine root biomass negatively correlated with soil exchangeable Al<sup>3+</sup> and Al<sup>3+</sup>/(Ca<sup>2+</sup> + Mg<sup>2+</sup>) ratio. Our results suggested that long-term N fertilization may negatively affect fine root growth, via severed soil acidification, Fe mobilization, and base cation depletion in highly acidified, N-saturated primary tropical forests. Initial forest N status, influenced by different land-use history, mediates N deposition effects on fine root growth.https://www.mdpi.com/1999-4907/13/8/1328nitrogen depositionfine root vitalityfine root chemistrysoil acidificationtropical forest |
| spellingShingle | Feifei Zhu Frank S. Gilliam Jan Mulder Muneoki Yoh Jiangming Mo Xiankai Lu Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N Status Forests nitrogen deposition fine root vitality fine root chemistry soil acidification tropical forest |
| title | Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N Status |
| title_full | Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N Status |
| title_fullStr | Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N Status |
| title_full_unstemmed | Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N Status |
| title_short | Effects of Excess Nitrogen (N) on Fine Root Growth in Tropical Forests of Contrasting N Status |
| title_sort | effects of excess nitrogen n on fine root growth in tropical forests of contrasting n status |
| topic | nitrogen deposition fine root vitality fine root chemistry soil acidification tropical forest |
| url | https://www.mdpi.com/1999-4907/13/8/1328 |
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