Search

Your search keyword '"Dijkstra, Feike A."' showing total 627 results
Start Over Author "Dijkstra, Feike A."
627 results on '"Dijkstra, Feike A."'

20. Aridity thresholds of soil microbial metabolic indices along a 3,200 km transect across arid and semi-arid regions in Northern China

Author

Hou, Jianfeng, Dijkstra, Feike A, Zhang, Xiuwei, Wang, Chao, Lü, Xiaotao, Wang, Peng, Han, Xingguo, and Cheng, Weixin

Subjects
Respiration, Microbial metabolism, Metabolic quotient, Carbon limitation, Microbial biomass, Microbial biomass., Biological Sciences, Medical and Health Sciences
Abstract

Soil microbial processes are crucial for understanding the ecological functions of arid and semi-arid lands which occupy approximately 40% of the global terrestrial ecosystems. However, how soil microbial metabolic activities may change across a wide aridity gradient in drylands remains unclear. Here, we investigated three soil microbial metabolic indices (soil organic carbon (SOC)-based microbial respiration, metabolic quotient, and microbial biomass as a proportion of total SOC) and the degree of carbon limitation for microbial respiration along a 3,200 km transect with a wide aridity gradient. The aridity gradient was customarily expressed using the aridity index (AI) which was calculated as the ratio of mean annual precipitation to mean annual evaporation, therefore, a lower AI value indicated a higher degree of aridity. Our results showed non-linear relationships between AI values and the metabolic indices with a clear aridity threshold for each of the three metabolic indices along the aridity gradient, respectively (AI = 0.13 for basal respiration, AI = 0.17 for metabolic quotient, and AI = 0.17 for MBC:SOC ratio). These metabolic indices linearly declined when AI was above the thresholds, but did not show any clear patterns when AI was below the thresholds. We also found that soil microbial respiration was highly limited by available carbon substrates at locations with higher primary production and relatively lower level of water limitation when AI was above the threshold, a counter-intuitive pattern that microbes were more starved in ecosystems with more substrate input. However, the increasing level of carbon limitation did correspond to the declining trend of the three metabolic indices along the AI gradient, which indicates that the carbon limitation influences microbial metabolism. We also found that the ratio of microbial biomass carbon to SOC in arid regions (AI < 0.2) with extremely low precipitation and primary production were not quantitatively related to SOC content. Overall, our results imply that microbial metabolism is distinctively different in arid lands than in non-arid lands.

Published
2019

36. Standards of Practice for Review and Publication of Models

Author

Aber, John D., primary, Bernhardt, Emily S., additional, Dijkstra, Feike A., additional, Gardner, Robert H., additional, Macneale, Kate H., additional, Parton, William J., additional, Pickett, Steward T.A., additional, Urban, Dean L., additional, and Weathers, Kathleen C., additional

Published
2021
Full Text
View/download PDF

42. Nitrogen and phosphorus availability affect wheat carbon allocation pathways: rhizodeposition and mycorrhizal symbiosis

Author

Bicharanloo, Bahareh, Shirvan, Milad Bagheri, Keitel, Claudia, and Dijkstra, Feike A.

Subjects
Photosynthesis -- Research, Wheat -- Research, Beef cattle, Fungi, Genotypes, Agricultural industry, Earth sciences
Abstract

Plants allocate their photosynthetic carbon (C) belowground through rhizodeposition, which can be incorporated into microbial biomass and organic matter, but can also be directly shared with arbuscular mycorrhizal fungi (AMF). In this study, we investigated how both rhizodeposition and AMF colonisation are affected by nitrogen (N) and phosphorus (P) availability in soil systems, and in mm, how these C allocation pathways influenced plant P uptake in four different wheat genotypes with variable root traits. Wheat genotypes (249, Suntop, Scout and IAW2013) were grown in pots and labelled continuously during their growth period with [sup.13]C[O.sub.2] to determine rhizodeposition. We applied two levels of N (25 and 100 kg [ha.sup.-1]) and P (10 and 40 kg [ha.sup.-1]) fertiliser. Plant root traits, plant P content, soil available P and N, microbial biomass C and P, and AMF colonisation were examined. We constructed a structural equation model to show how C allocation to rhizodeposition and AMF colonisation depended on P and N availability, and how these pathways affected plant P uptake and grain yield. Wheat genotypes with fine roots (Suntop, Scout and IAW2013) were associated with AMF colonisation for plant P uptake, and the genotype with the largest root biomass (249) provided more C to rhizodeposition. Both rhizodeposition and AMF colonisation increased plant P and grain yield under low P and high N availability respectively, while root biomass and root traits, such as specific root length and proportion of fine roots, determined which C allocation pathway was employed by the plant. Additional keywords: C allocation, [sup.13]C labelling, mycorrhizal colonisation, microbial biomass phosphorus, root traits, phosphorus uptake. Received 9 July 2019, accepted 18 November 2019, published online 4 December 2019, Introduction Many Australian soils are phosphorus (P)-deficient and P is one of the most critical and limiting nutrients in many soils of Australia (Viscarra Rossel and Bui 2016). Phosphorus is [...]

Published
2020
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results