Functional shifts in weed community composition following adoption of conservation agriculture

Weed Research ◽  
2021 ◽  
Author(s):  
Damien Derrouch ◽  
Bruno Chauvel ◽  
Stéphane Cordeau ◽  
Fabrice Dessaint
2019 ◽  
Author(s):  
Coline Deveautour ◽  
Sally Power ◽  
Kirk Barnett ◽  
Raul Ochoa-Hueso ◽  
Suzanne Donn ◽  
...  

Climate models project overall a reduction in rainfall amounts and shifts in the timing of rainfall events in mid-latitudes and sub-tropical dry regions, which threatens the productivity and diversity of grasslands. Arbuscular mycorrhizal fungi may help plants to cope with expected changes but may also be impacted by changing rainfall, either via the direct effects of low soil moisture on survival and function or indirectly via changes in the plant community. In an Australian mesic grassland (former pasture) system, we characterised plant and arbuscular mycorrhizal (AM) fungal communities every six months for nearly four years to two altered rainfall regimes: i) ambient, ii) rainfall reduced by 50% relative to ambient over the entire year and iii) total summer rainfall exclusion. Using Illumina sequencing, we assessed the response of AM fungal communities sampled from contrasting rainfall treatments and evaluated whether variation in AM fungal communities was associated with variation in plant community richness and composition. We found that rainfall reduction influenced the fungal communities, with the nature of the response depending on the type of manipulation, but that consistent results were only observed after more than two years of rainfall manipulation. We observed significant co-associations between plant and AM fungal communities on multiple dates. Predictive co-correspondence analyses indicated more support for the hypothesis that fungal community composition influenced plant community composition than vice versa. However, we found no evidence that altered rainfall regimes were leading to distinct co-associations between plants and AM fungi. Overall, our results provide evidence that grassland plant communities are intricately tied to variation in AM fungal communities. However, in this system, plant responses to climate change may not be directly related to impacts of altered rainfall regimes on AM fungal communities. Our study shows that AM fungal communities respond to changes in rainfall but that this effect was not immediate. The AM fungal community may influence the composition of the plant community. However, our results suggest that plant responses to altered rainfall regimes at our site may not be resulting via changes in the AM fungal communities.


2020 ◽  
pp. 67-79
Author(s):  
Yu. Kravchenko

In Ukraine 57.5 % of agricultural land is subjected to erosion with 10–24 million tons of humus, 0.3–0.96 million tons of nitrogen, 0.7–0.9 million tons of phosphorus and 6–12 million tons of potassium lost annually. Degradation processes are also common on chernozems, which cover about 60 % of the Ukrainian territory. The aim of the research is to defi ne the most eff ective soil conservation practices and legislative decisions aimed to conservation/recovering the Ukrainian chernozem fertility. The experimental data of the agrochemical certifi cation of Ukrainian lands, data from scientifi c papers, stock and instructional materials as well as our own fi eld and laboratory studies were used. It has been established that the long-term use of deep subsurface tillage on typical chernozem increases, compared with plowing, the content of 10–0.25 mm of air-dry and water-resistant aggregates, the bulk density, soil water storages, water infi ltration rates, the content of mobile phosphorus and exchangeable potassium, pHH2O, CaCO3 stocks, the contents of humic and fulvic acids, molecular weights of humic acids – by 5.5 and 3.06 %; 0.05 g/cm3; 25.5 mm; 22.6 mm/h; 0.1 and 3 mg/100 g of soil; 0.03 pHH2O; 18 t/ha, 0.02 and 0.04 %, 91195 kDa, respectively. Fertilizers may contribute to the crop yields increase from by 60% in the Polissya, by 40 % – in the Forest Steppe, by 15 % – in the Wet Steppe, by 10 % – in the Dry Steppe and by 40 % – in the Irrigated Steppe areas. In soil-conservation rotations, the crop placement and alternation are advisable to combine with strips or hills sowing, taking into account the local relief features; soil alkalinization, applying anti-erosion structures. Ukrainian agriculture will receive additional 10–12 million tons of forage units or 20–22 % from all fodder in a fi eld agriculture under increasing 8–10 % of arable lands for intercrops. It is advisable to mulch the eroded chernozems of Ukraine depending on their texture composition: 1.3 t/ha of mulch for sandy and loamy soils, 1.9 t/ha – for sandy and 1.1 t/ha – for loamy soils. The implementation of soil conservation agriculture can minimize some soil degradation processes and improve eff ective soil properties required to realize the biological potential of cultivated plants. Key words: chernozem, degradation, fertility, soil conservation technologies, agriculture policy.


2019 ◽  
Vol 83 (3) ◽  
pp. 295-308
Author(s):  
MG Weinbauer ◽  
S Suominen ◽  
J Jezbera ◽  
ME Kerros ◽  
S Marro ◽  
...  

2020 ◽  
Vol 637 ◽  
pp. 159-180
Author(s):  
ND Gallo ◽  
M Beckwith ◽  
CL Wei ◽  
LA Levin ◽  
L Kuhnz ◽  
...  

Natural gradient systems can be used to examine the vulnerability of deep-sea communities to climate change. The Gulf of California presents an ideal system for examining relationships between faunal patterns and environmental conditions of deep-sea communities because deep-sea conditions change from warm and oxygen-rich in the north to cold and severely hypoxic in the south. The Monterey Bay Aquarium Research Institute (MBARI) remotely operated vehicle (ROV) ‘Doc Ricketts’ was used to conduct seafloor video transects at depths of ~200-1400 m in the northern, central, and southern Gulf. The community composition, density, and diversity of demersal fish assemblages were compared to environmental conditions. We tested the hypothesis that climate-relevant variables (temperature, oxygen, and primary production) have more explanatory power than static variables (latitude, depth, and benthic substrate) in explaining variation in fish community structure. Temperature best explained variance in density, while oxygen best explained variance in diversity and community composition. Both density and diversity declined with decreasing oxygen, but diversity declined at a higher oxygen threshold (~7 µmol kg-1). Remarkably, high-density fish communities were observed living under suboxic conditions (<5 µmol kg-1). Using an Earth systems global climate model forced under an RCP8.5 scenario, we found that by 2081-2100, the entire Gulf of California seafloor is expected to experience a mean temperature increase of 1.08 ± 1.07°C and modest deoxygenation. The projected changes in temperature and oxygen are expected to be accompanied by reduced diversity and related changes in deep-sea demersal fish communities.


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