Plant-plant interactions

We measured the effect of elevated atmospheric CO2 on atmospheric nitrogen (N2) fixation for the tree species Alnus glutinosa growing in monoculture or in mixture with the non-N2-fixing tree species Betula pendula and Fagus sylvatica. We addressed the hypotheses that 1: N2 fixation in A. glutinosa will increase in response to increased atmospheric CO2 concentrations, when growing in monoculture, 2: the impact of elevated CO2 on N2 fixation in A. glutinosa is the same in mixture and in monoculture and 3: the impacts of elevated CO2 on N cycling will be evident in a decrease in leaf δ15N and in the soil-leaf enrichment factor (EF), and that these impacts will not differ between mixed and single species stands. Trees were grown in a forest plantation on former agricultural fields for 4 growing seasons, after which the trees were on average 3.8 m tall and canopy closure had occurred. Atmospheric CO2 concentrations were maintained at either ambient or elevated (by 200 ppm) concentrations using a free-air CO2 enrichment (FACE) system. Leaf δ15N was measured and used to estimate the amount (Ndfa) and proportion (%Ndfa) of N derived from atmospheric fixation. On average 62% of the N in A. glutinosa leaves was from fixation. %Ndfa and Ndfa for A. glutinosa trees in monoculture did not increase under elevated CO2, despite higher growth rates. However, N2 fixation did increase for trees growing in mixture, despite the absence of significant growth stimulation. There was evidence that fixed N2 was transferred from A. glutinosa to F. sylvatica and B. pendula, but no evidence that this affected their CO2 response. This study shows that N2 fixation in A. glutinosa may be higher in a future elevated CO2 world, but that this effect will only occur where the trees are growing in mixed species stands.

Network Biology
ISSN 2220-8879
CODEN NBEICS

http://www.iaees.org/publications/journals/nb/articles/2019-9(2)/2019-9(2).asp

Volume 9, Number 2, 1 June 2019

Articles

Evaluating the network structure of different Neotropical plant-plant interactions
Network Biology, 2019, 9(2): 18-27
Walter Santos de Araujo
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[Email Article] [Comment/Review Article]


Design of a common pathway drug for all types of cardiovascular diseases: A network biology approach
Network Biology, 2019, 9(2): 28-41
Al-Mustanjid Arif, Chandan Mandal, Md. Habibur Rahman
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[ Full PDF (1362K)]
[Email Article] [Comment/Review Article]

Improving fertility of marginal soils for the sustainable production of biomass is a strategy for reducing land use conflicts between food and energy crops. Digestates can be used as fertilizer and for soil amelioration. In order to promote plant growth and reduce potential adverse effects on roots because of broadcast digestate fertilization, we propose to apply local digestate depots placed into the rhizosphere. We grew Sida hermaphrodita in large mesocosms outdoors for three growing seasons and in rhizotrons in the greenhouse for 3 months both filled with marginal substrate, including multiple sampling dates. We compared digestate broadcast application with digestate depot fertilization and a mineral fertilizer control. We show that depot fertilization promotes a deep reaching root system of S. hermaphrodita seedlings followed by the formation of a dense root cluster around the depot-fertilized zone, resulting in a fivefold increased biomass yield. Temporal adverse effects on root growth were linked to high initial concentrations of ammonium and nitrite in the rhizosphere in either fertilizer application, followed by a high biomass increase after its microbial conversion to nitrate. We conclude that digestate depot fertilization can contribute to an improved cultivation of perennial energy-crops on marginal soils.