The interaction between nitrogen and phosphorous is a strong predictor of intra-plant variation in nitrogen isotope composition in a desert species

Journal Article · Wed Jan 11 00:00:00 EST 2017 · Biogeosciences (Online)

DOI:https://doi.org/10.5194/bg-14-131-2017· OSTI ID:1394470

Zhang, Jinxin ^[1]; Gu, Lianhong ^[2]; Zhang, Jingbo ^[3]; Wu, Rina ^[4]; Wang, Feng ^[4]; Lin, Guanghui ^[5]; Wu, Bo ^[4]; Lu, Qi ^[4]; Meng, Ping ^[6]

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1. Chinese Academy of Forestry, Beijing (China). Inst. of Desertification Studies. Research Inst. of Forestry
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Environmental Sciences Division. Climate Change Science Inst.
3. Chinese Academy of Forestry, Beijing (China). Inst. of Desertification Studies; The Experimental Center of Desert Forestry of the Chinese Academy of Forestry, Dengkou, Inner Mongolia Autonomous Region (China)
4. Chinese Academy of Forestry, Beijing (China). Inst. of Desertification Studies
5. Tsinghua Univ., Beijing (China). Center for Earth System Science
6. Chinese Academy of Forestry, Beijing (China)

Understanding intra-plant variations in δ¹⁵N is essential for fully utilizing the potential of δ¹⁵N as an integrator of the terrestrial nitrogen (N) cycle and as an indicator of the relative limitation of N and phosphorous (P) on plant growth. Studying such variations can also yield insights into N metabolism by plant as a whole or by specific organs. However, few researchers have systematically evaluated intra-plant variations in δ¹⁵N and their relationships with organ nutrient contents. We excavated whole plant architectures of Nitraria tangutorum Bobrov, a C₃ species of vital regional ecological importance, in two deserts in northwestern China. We systematically and simultaneously measured N isotope ratios and N and P contents of different parts of the excavated plants. We found that intra-plant variations in δ¹⁵N of N. tangutorum were positively correlated with corresponding organ N and P contents. However, it was the N × P interaction, not N and P individually or their linear combination, that was the strongest predictor of intra-plant δ¹⁵N. Additionally, we showed that root δ¹⁵N increased with depth into soil, a pattern similar to profiles of soil δ¹⁵N reported by previous studies in different ecosystems. We hypothesized that the strong positive intra-plant δ¹⁵N–N and P relationships are caused by three processes acting in conjunction: (1) N and P content-driven fractionating exchanges of ammonia between leaves and the atmosphere (volatilization) during photorespiration, (2) resorption and remobilization of N and P from senescing leaves, and (3) mixture of the re-translocated foliar N and P with existing pools in stems and roots. To test our hypothesis, future studies should investigate plant N volatilization and associated isotope fractionation and intra-plant variations in δ¹⁵N in different species across ecosystems and climates.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Biological and Environmental Research (BER); Ministry of Science and Technology (MOST) (China); National Natural Science Foundation of China (NSFC); State Forestry Administration of China; Chinese Academy of Forestry (CAF)
• Grant/Contract Number: AC05-00OR22725; 2012BAD16B01; 31400620; 201404304; CAF201202; CAFYBB2011007
• OSTI ID: 1394470
• Journal Information: Biogeosciences (Online), Vol. 14, Issue 1; ISSN 1726-4189
• Publisher: European Geosciences Union
• Country of Publication: United States
• Language: English

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59 BASIC BIOLOGICAL SCIENCES