ASLO 2017 Ocean Sciences Meeting: Mountains to the Sea, 26 February-3 March 2017, Honolulu, Hawaii.
session 070 – Source, speciation, transformation and transport of C, N, and P from terrestrial to freshwater systems
Carbon (C), nitrogen (N), and phosphorus (P) are nutrients often limiting net primary production in aquatic environments. Terrestrial systems are significant sources of these nutrients entering aquatic systems and their nature and availability influence algal biomass production and seasonal dynamics. An understanding of the effects of land management practices on the sources of C, N and P as well as the speciation and transformations of these nutrients in both terrestrial and freshwater systems is critical for controlling the balance of these nutrients in the aquatic environment. The aim of this session is to bring together researchers working on factors affecting speciation and transformation of C, N and P during transport along the terrestrial to freshwater system continuum, including the empirical nutrient signatures and ratios or different source areas and the kinetics of processes transforming nutrient species.
Primary Convener: Ivan P. O’Halloran, University of Guelph, Ridgetown Campus, Ridgetown ON, Canada
Conveners: R. Paul Voroney,Yuki Audette, Katelyn A. Congreves, University of Guelph, Guelph ON, Canada and Chris T. Parsons, University of Waterloo, Waterloo ON, Canada
Helle Astrid Kjær from Centre for Ice and Climate (University of Copenhagen) describes how the atmospheric transport of P has changed over time in the following manuscripts:
(past 100 yrs)
Kjær, Helle Astrid, et al. “Continuous flow analysis method for determination of dissolved reactive phosphorus in ice cores.” Environmental science & technology 47.21 (2013): 12325-12332.
Kjær, Helle Astrid, et al. “Greenland ice cores constrain glacial atmospheric fluxes of phosphorus.” Journal of Geophysical Research: Atmospheres120.20 (2015).
Journal: New Phytologist
Authors: Lin Zhang, Minggang Xu, Yu Liu, Fusuo Zhang, Angela Hodge, Gu Feng
- Arbuscular mycorrhizal fungi (AMF) transfer plant photosynthate underground which can stimulate soil microbial growth. In this study, we examined whether there was a potential link between carbon (C) release from an AMF and phosphorus (P) availability via a phosphate-solubilizing bacterium (PSB).
- We investigated the outcome of the interaction between the AMF and the PSB by conducting a microcosm and two Petri plate experiments. An in vitro culture experiment was also conducted to determine the direct impact of AMF hyphal exudates on growth of the PSB.
- The AMF released substantial C to the environment, triggering PSB growth and activity. In return, the PSB enhanced mineralization of organic P, increasing P availability for the AMF. When soil available P was low, the PSB competed with the AMF for P, and its activity was not stimulated by the fungus. When additional P was added to increase soil available P, the PSB enhanced AMF hyphal growth, and PSB activity was also stimulated by the fungus.
- Our results suggest that an AMF and a free-living PSB interacted to the benefit of each other by providing the C or P that the other microorganism required, but these interactions depended upon background P availability.
Journal: Journal of Experimental Botany
Authors: Fei Wang, Ning Shi, Rongfeng Jiang, Fusuo Zhang and Gu Feng
Abstract: This study used a [13C]DNA stable isotope probing (SIP) technique to elucidate a direct pathway for the translocation of 13C-labeled photoassimilate from maize plants to extraradical mycelium-associated phosphate-solubilizing bacteria (PSB) that mediate the mineralization and turnover of soil organic phosphorus (P) in the hyphosphere. Inoculation with PSB alone did not provide any benefit to maize plants but utilized the added phytate-P to their own advantage, while inoculation withRhizophagus irregularis alone significantly promoted shoot biomass and P content compared with the control. However, compared with both sole inoculation treatments, combined inoculation with PSB and R. irregularis in the hyphosphere enhanced organic P mineralization and increased microbial biomass P in the soil. There was no extra benefit to plant P uptake but the hyphal growth of R. irregularis was reduced, suggesting that PSB benefited from the arbuscular mycorrhizal (AM) fungal mycelium and competed for soil P with the fungus. The combination of T-RFLP (terminal restriction fragment length polymorphism) analysis with a clone library revealed that one of the bacteria that actively assimilated carbon derived from pulse-labeled maize plants was Pseudomonas alcaligenes(Pseudomonadaceae) that was initially inoculated into the hyphosphere soil. These results provide the first in situ demonstration of the pathway underlying the carbon flux from plants to the AM mycelium-associated PSB, and the PSB assimilated the photosynthates exuded by the fungus and promoted mineralization and turnover of organic P in the soil.
Journal : Micorrhiza
Authors: Qun Chu, Xinxin Wang, Yang Yang, Fanjun Chen, Fusuo Zhang, Gu Feng
Abstract: The aim of this study was to compare the mycorrhizal responsiveness among old and recent Chinese maize genotypes (released from 1950s to 2008) in low- and high-Olsen-P soils and to identify parameters that would indicate the relationships between the mycorrhizal responsiveness and the functional traits related to P uptake of maize. A greenhouse factorial experiment was conducted. The factors were maize genotype [Huangmaya (HMY), Zhongdan 2 (ZD2), Nongda 108 (ND108), and NE15], inoculation with or without arbuscular mycorrhizal fungi (AMF) (Rhizophagus irregularis), and Olsen-P levels (4, 9, 18, 36, or 60 mg P kg−1). Old and recently released genotypes differed in their response to AMF under low- and high-P supply. Three kinds of responses (in terms of shoot growth) were observed: the response was positive if the soil P content was low, but negative if the soil Olsen-P content was high (HMY and ND108); the response was neutral regardless of soil P content (ZD2); and the response was positive regardless of soil P content (NE15). Principle component (PC) analysis showed that the first PC comprised morphological and physiological traits of maize roots, and the second PC comprised mycorrhizal traits. The opposite was the case, however, in high-P soil. It is concluded that maize breeding selection from 1950s to 2000s is not always against the AM association and that AMF play positive roles in promoting the growth of some maize genotypes in high-P soil. The root length colonization by efficient AMF might be a useful parameter for breeding varieties with increased mycorrhizal responsiveness.
Journal: Global Biogeochemical Cycles – Wiley Online Library
Authors: Enqing Hou, Chengrong Chen, Yuanwen Kuang, Yuguang Zhang, Marijke Heenan, and Dazhi Wen
Abstract: Understanding the soil phosphorus (P) cycle is a prerequisite for predicting how environmental changes may influence the dynamics and availability of P in soil. We compiled a database of P fractions sequentially extracted by the Hedley procedure and its modification in 626 unfertilized and uncultivated soils worldwide. With this database, we applied structural equation modeling to test hypothetical soil P transformation models and to quantify the importance of different soil P pools and P transformation pathways in shaping soil P availability at a global scale. Our models revealed that soluble inorganic P (Pi, a readily available P pool) was positively and directly influenced by labile Pi, labile organic P (Po), and primary mineral P, and negatively and directly influenced by secondary mineral P; soluble Pi was not directly influenced by moderately labile Po or occluded P. The overall effect on soluble Pi was greatest for labile Pi followed by the organic P pools, occluded P, and then primary mineral P; the overall influence from secondary mineral P was small. Labile Pi was directly linked to all other soil P pools and was more strongly linked than soluble Pi to labile Po and primary mineral P. Our study highlights the important roles of labile Pi in mediating P transformations and in determining overall P availability in soils throughout the world.
Final Programme Now Available
The OP2016 workshop is around the corner and we have 100 delegates registered. We received a substantial number of exceptional abstracts and the OP2016 Steering group has considered all abstracts submitted. The Final OP2016 Programme can now be downloaded.
Session 1: Organic P flows in the environment in context with other nutrient cycles: Integration across ecosystems
Prof. Leo Condron
Keynote Talk: Historical perspective on the nature and dynamics of organic phosphorus in the environment
Session 2: Methods of evaluating organic P stocks, concentration and speciation
Dr. Barbara Cade-Menun
Keynote Talk: Methods to characterize and quantify organic phosphorus in environmental samples: past successes and future directions
Session 3: Biotic interactions in organic P cycling – Plants
Dr. Marie Spohn
Keynote Talk: How are organic carbon and phosphorus mineralization connected in the rhizosphere?
Dr. Mark Smits
Keynote Talk: Plant-fungus interactions with apatite: ideas versus observations of mycorrhizal fungi-induced apatite weathering
Session 4: Biotic interactions in organic P cycling – Microbes
Dr. Federica Tamburini
Keynote Talk: Insights into the biological cycle of P (with a little help from oxygen isotopes).
Dr. Anna Rosling
Keynote Talk: How mycorrhizal associations effects phosphorus cycling in deciduous forest soils.
Session 5: Organic P in soil and waters: Stocks, Flows and impact of scale
Prof. Dr. Erwin Klumpp
Keynote Talk: Specification of nano-particulate phosphorus in terrestrial systems
Session 6: Global challenges for Organic P research
Dr. Ben Turner
Keynote Talk: Organic phosphorus and the ecology of tropical forests