Nitrogen deposition influences nitrogen isotope composition in soil and needles of Pinus massoniana forests along an urban-rural gradient in the Pearl River Delta of south China
- 393 Downloads
Atmospheric nitrogen (N) deposition remains globally and regionally a significant N source in forest ecosystems, with intensive industrial activities. Stable N isotope ratio (δ15N) is a useful indicator widely adopted to assess environmental and ecological impacts of anthropogenic N inputs. On the basis of temporal changes in tree ring δ15N established recently, the present study investigated the influence of N deposition on δ15N in needles of Masson pine (Pinus massoniana L.) and forest soil along an urban–rural gradient in the Pearl River Delta of south China.
Materials and methods
Soil and needle samples were selected from South China Botanical Garden (SBG) in Guangzhou, Ding Hu Shan Natural Reserve (DHS) in Zhaoqing, and Nan Kun Shan Natural Reserve (NKS) in Huizhou. Five soil profiles at each site were sampled at three horizons: organic horizon (Oa), 0–10 and 10–20 cm depths, underneath the selected Masson pine trees. Soil samples were air-dried and sieved through 2 mm for analysis. Current-year and previous-year needles of Masson pine were collected from outer branches of the middle canopy at south, west, east, and north directions, and pooled according to needle age for each tree. Needles were rinsed, dried, ground, and stored in desiccator before analysis. Nitrogen isotope ratios were determined by Finnigan isotope mass spectrometer.
Results and discussion
Significant differences in soils (Oa and 0–10 cm depth layers) and needles along the urban–rural gradient were revealed with positively high δ15N values (+2.19 ± 1.43‰ in Oa, +6.67 ± 1.52‰ in 0–10 cm depth layer and about +1.0‰ in needles) at the rural site (NKS) and negatively low δ15N values (−5.51 ± 1.38‰ in Oa, −1.11 ± 1.36‰ in 0–10 cm depth layer and about −5.0‰ in needles) at the highest N deposition site (SBG). Needles exposed to high N deposition had significantly different δ15N values between age classes. The results suggested that atmospheric N deposition density contributed to the patterns of δ15N in soil and needles of Pinus massoniana along the urban–rural gradient.
The detectably decreasing trends of δ15N observed in the soils and pine needles from NKS to SBG implied that N deposition has influenced the forests N isotope composition. The patterns of soil- and needle-δ15N of Masson pine might be closely related to N deposition intensity. Values of δ15N in soils and needles were indicative of the gradient of urban–rural N deposition in the Pearl River Delta of south China.
KeywordsForest soil Nitrogen deposition δ15N Pine needle Pinus massoniana
This project has been jointly supported by National Natural Science Foundation of China (No. 30972365), National Basic Research Program of China (No. 2009CB421101), Guangdong Natural Science Foundation (No. 10151065005000001), and the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KSCX2-EW-J-28). Dr David Doley from University of Queensland helped to improve the manuscript.
- Brady NC, Weil R (2001) The nature and properties of soils. Pearson Education, NJGoogle Scholar
- Chen XY, Mulder J (2008) Atmospheric deposition of nitrogen at five subtropical forested sites in South China. Sci Total Environ 378:317–330Google Scholar
- Choi WJ, Lee SM, Yoo SH (2001) Increase in δ15N of nitrate through kinetic isotope fractionation associated with denitrification in soil. Agr Chem Biotechnol 44:135–139Google Scholar
- Editorial Committee of Foresets of Guangdong (2005) Guangdong Yearbook. Guangdong Yearbook Publishing House, Guangzhou (in Chinese)Google Scholar
- Guangdong Soil Survey Office (1993) Guangdong soil. Science Press, Beijing, in ChineseGoogle Scholar
- Huang ZL, Ding MM, Zhang ZP, Yi WM (1994) The hydrological processes and nitrogen dynamics in a monsoon evergreen broad-leafed forest of Dinghushan. Acta Phytoecologica Sin 8:194–199 (in Chinese with English abstract)Google Scholar
- Likens GE, Driscoll CT, Buso DC (1996) Long-term effects of acid rain: response and recovery of a forest ecosystem. Nature 272:244–246Google Scholar
- Liu DW, Xia H (2007) Chemical characteristics of precipitation in Foshan: comparing with Guangzhou. Environ Sci Technol 30:71–74 (in Chinese with English abstract)Google Scholar
- Ren R, Mi FJ, Bai NB (2000) A chemometries analysis on the data of precipitation chemistry of China. J Bejing Polytech Univ 26:90–95 (in Chinese with English abstract)Google Scholar
- Sun FF, Kuang YW, Wen DZ, Xu ZH, Li JL, Zuo WD, Hou EN (2010) Long-term tree growth rate, water use efficiency, and tree ring nitrogen isotope composition of Pinus massoniana L. in response to global climate change and local nitrogen deposition in Southern China. J Soils Sediments 10:1453–1465CrossRefGoogle Scholar
- Zhang XF (2006) Ecological significance of acid rain transformation in Huizhou City. J Agr Environ Sci 25:733–736 (in Chinese with English abstract)Google Scholar
- Zhou GY, Yan JH (2001) The influence of regional atmospheric precipitation characteristics and its element inputs on the existence and development of Dinghushan forest ecosystems. Acta Ecol Sin 21:2002–2012Google Scholar