J Plant Ecol ›› 2016, Vol. 9 ›› Issue (5): 564-575 .DOI: 10.1093/jpe/rtv076

• Research Articles • Previous Articles     Next Articles

The effect of temporal variation in soil carbon inputs on interspecific plant competition

Stav Livne-Luzon1,*, Hagai Shemesh2, Osnat Gilor3 and Ofer Ovadia1   

  1. 1 Department of Life Sciences, Ben-Gurion University of the Negev, POB 653, Beer Sheva 8410501, Israel; 2 Department of Environmental Sciences, Tel-Hai Academic College, Upper Galilee 12208, Israel; 3 Department of Environmental Hydrology and Microbiology, Jacob Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Sede Boqer 84990, Israel
  • Received:2015-07-26 Accepted:2015-11-17 Published:2016-09-20
  • Contact: Livne-Luzon, Stav

The effect of temporal variation in soil carbon inputs on interspecific plant competition

Abstract: Aims Release of carbon from plant roots initiates a chain of reactions involving the soil microbial community and microbial predators, eventually leading to nutrient enrichment, a process known as the 'microbial loop'. However, root exudation has also been shown to stimulate nutrient immobilization, thereby reducing plant growth. Both mechanisms depend on carbon exudation, but generate two opposite soil nutrient dynamics. We suggest here that this difference might arise from temporal variation in soil carbon inputs.
Methods We examined how continuous and pulsed carbon inputs affect the performance of wheat (Triticum aestivum), a fast-growing annual, while competing with sage (Salvia officinalis), a slow-growing perennial. We manipulated the temporal mode of soil carbon inputs under different soil organic matter (SOM) and nitrogen availabilities. Carbon treatment included the following two carbon input modes: (i) Continuous: a daily release of minute amounts of glucose, and (ii) Pulsed: once every 3 days, a short release of high amounts of glucose. The two carbon input modes differed only in the temporal dynamic of glucose, but not in total amount of glucose added. We predicted that pulsed carbon inputs should result in nutrient enrichment, creating favorable conditions for the wheat plants.
Important findings Carbon addition caused a reduction in the sage total biomass, while increasing the total wheat biomass. In SOM-poor soil without nitrogen and in SOM-rich soil with nitrogen, wheat root allocation was higher under continuous than under pulsed carbon input. Such an allocation shift is a common response of plants to reduced nutrient availability. We thus suggest that the continuous carbon supply stimulated the proliferation of soil microorganisms, which in turn competed with the plants over available soil nutrients. The fact that bacterial abundance was at its peak under this carbon input mode support this assertion. Multivariate analyses indicated that besides the above described changes in plant biomasses and bacterial abundances, carbon supply led to an accumulation of organic matter, reduction in NO 3 levels and increased levels of NH 4 in the soil. The overall difference between the two carbon input modes resulted primarily from the lower total wheat biomass, and lower levels of NO 3 and soil PH characterizing pots submitted to carbon pulses, compared to those subjected to continuous carbon supply. Carbon supply, in general, and carbon input mode, in particular, can lead to belowground chain reactions cascading up to affect plant performance.

Key words: competition, exudation, microbial loop, nutrient immobilization

摘要:
Aims Release of carbon from plant roots initiates a chain of reactions involving the soil microbial community and microbial predators, eventually leading to nutrient enrichment, a process known as the 'microbial loop'. However, root exudation has also been shown to stimulate nutrient immobilization, thereby reducing plant growth. Both mechanisms depend on carbon exudation, but generate two opposite soil nutrient dynamics. We suggest here that this difference might arise from temporal variation in soil carbon inputs.
Methods We examined how continuous and pulsed carbon inputs affect the performance of wheat (Triticum aestivum), a fast-growing annual, while competing with sage (Salvia officinalis), a slow-growing perennial. We manipulated the temporal mode of soil carbon inputs under different soil organic matter (SOM) and nitrogen availabilities. Carbon treatment included the following two carbon input modes: (i) Continuous: a daily release of minute amounts of glucose, and (ii) Pulsed: once every 3 days, a short release of high amounts of glucose. The two carbon input modes differed only in the temporal dynamic of glucose, but not in total amount of glucose added. We predicted that pulsed carbon inputs should result in nutrient enrichment, creating favorable conditions for the wheat plants.
Important findings Carbon addition caused a reduction in the sage total biomass, while increasing the total wheat biomass. In SOM-poor soil without nitrogen and in SOM-rich soil with nitrogen, wheat root allocation was higher under continuous than under pulsed carbon input. Such an allocation shift is a common response of plants to reduced nutrient availability. We thus suggest that the continuous carbon supply stimulated the proliferation of soil microorganisms, which in turn competed with the plants over available soil nutrients. The fact that bacterial abundance was at its peak under this carbon input mode support this assertion. Multivariate analyses indicated that besides the above described changes in plant biomasses and bacterial abundances, carbon supply led to an accumulation of organic matter, reduction in NO 3 levels and increased levels of NH 4 in the soil. The overall difference between the two carbon input modes resulted primarily from the lower total wheat biomass, and lower levels of NO 3 and soil PH characterizing pots submitted to carbon pulses, compared to those subjected to continuous carbon supply. Carbon supply, in general, and carbon input mode, in particular, can lead to belowground chain reactions cascading up to affect plant performance.