Nitrogen immobilization may reduce invasibility of nutrient enriched plant community invaded by Phragmites australis

Abstract

Nutrient enrichment, particularly nitrogen, is an important determinant of plant community productivity, diversity and invasibility in a wetland ecosystem. It may contribute to increasing colonization and dominance of invasive species, such as Phragmites australis, especially during wetland restoration. Providing native species a competitive advantage over invasive species, manipulating soil nutrients (nitrogen) may be an effective strategy to control the invasive species and that management tool is essential to restore the degraded ecosystems. Therefore, we examined competition between Phragmites australis and Melaleuca ericifolia in a greenhouse setting with activated carbon (AC) treatments, followed by cutting of Phragmites shoots in nutrient-rich soils. Additionally, we evaluated the effect of AC on plant-free microcosms in the laboratory, to differentiate direct effects of AC on soil microbial functions from indirect effects. Overall, the objective was to test whether lowering nitrogen might be an effective approach for reducing Phragmites invasion in the wetland. The AC reduced Phragmites total biomass more significantly in repeated cut regime (57%) of Phragmites shoots compared to uncut regime (39%). Conversely, it increased Melaleuca total biomass by 41% and 68% in uncut and repeated cut regimes, respectively. Additionally, AC decreased more total nitrogen in above-ground biomass (41 to 55%) and non-structural carbohydrate in rhizome (21 to 65%) of Phragmites, and less total nitrogen reduction in above-ground biomass (25 to 24%) of Melaleuca in repeated cut compared to uncut regime. The significant negative correlation between Phragmites and Melaleuca total biomass was observed, and noticed that Phragmites acquired less biomass comparatively than Melaleuca in AC-untreated versus AC-treated pots across the cutting frequency. AC also caused significant changes to microbial community functions across Phragmites populations, namely nitrogen mineralization, nitrification, nitrogen microbial biomass and dehydrogenase activity (P ≤ 0.05) that may potentially explain changes in plant growth competition between Phragmites and Melaleuca. The overall effects on plant growth, however, may be partially microbially mediated, which was demonstrated through soil microbial functions. Results support the idea that reducing community vulnerability to invasion through nutrient (nitrogen) manipulations by AC with reducing biomass of invasive species may provide an effective strategy for invasive species management and ecosystem restoration.There are numerous global environmental issues ranging from climate change, global warming, pollution, biological invasion to loss of biodiversity and many more 1 . Amongst these, biological invasion has been considered the most persistent issue to cause biodiversity loss and species extinction placing negative impacts on natural communities and ecological characteristics 2,3 . In parallel, nutrient enrichment is augmenting the invasion process, and is considered a communal obstacle in impl...

Phosphorus Shapes Soil Microbial Community Composition and Network Properties During Grassland Expansion Into Shrubs in Tibetan Dry Valleys

“…In this study, ammonia increased mostly during the later stage of expansion (from T to G) ( Figures 1B,F,G ), indicating that the final grass dominance over shrub was potentially linked to a more active nitrogen cycle. Compared with perennial shrubs, annual grass species tend to have faster growing rate ( Uddin et al, 2020 ); fast-growing species had higher efficient in transporting water, in acquiring and using nutrients and in fixing carbon ( Reich, 2014 ). Ammonia is released from the decomposition of organic nitrogen, a process conducted by microbes ( Galloway et al, 2004 ).…”

“…Ammonia is released from the decomposition of organic nitrogen, a process conducted by microbes ( Galloway et al, 2004 ). Moreover, ammonia is easily to be assimilated by fast-growing grass plants ( Uddin et al, 2020 ), which could meet the higher nitrogen demand of grass species and enhance their dominance over shrubs ( Galloway et al, 2004 ). Thus, our results support that enhanced relative P limitation, accompanied by the decreasing TP and increasing TN, potentially altered the relative competence of grass and shrub in this research.…”

Species identities impact the responses of intensity and importance of competition to the change of soil nutrition condition

“…Similarly, the competition intensity of different target species neighbored by the same neighbor was different from each other (Pérez-Ramos et al 2019;Saccone et al 2017). Secondly, only the factor of plantation condition (grown alone or in mixtures with different neighbors) significantly influenced the root: shoot ratio, which indicated that different neighbors resulted in different nutrition availability for target species or influenced the nutrition absorption of the target species, independently of the soil nutrition conditions (Uddin et al 2020;Zhang et al 2008). Therefore, in the present study, we found several mechanisms potentially contribute to these differential neighbor effects on different target species, as mentioned by other researchers (Bertness and Callaway 1994;Grime, 1977;Grime, 1979;Suding and Goldberg 2001).…”

Gradual Enhancement of the Assemblage Stability of the Reed Rhizosphere Microbiome with Recovery Time

“…Previous studies have documented that the lineage-specific control of rhizosphere bacteria and within-lineage bacterial communities was similar among reed communities [ 35 ]. Most studies involving reeds have focused on invading effects [ 36 , 37 ], decomposition efficiency [ 38 , 39 ], and single kingdom or functional groups [ 32 , 40 ]. To the best of our knowledge, the recovery effects on the assemblage stability of the reed rhizosphere microbiome and the vital roles of core taxa and keystone species in maintaining assemblage stability remain unexplored.…”