Urban ecosystems are an increasingly dominant feature of terrestrial landscapes. While evidence that species can adapt to urban environments is accumulating, the mechanisms through which urbanization ...imposes natural selection on populations are poorly understood. The identification of adaptive phenotypic changes (i.e. clines) along urbanization gradients would facilitate our understanding of the selective factors driving adaptation in cities. Here, we test for phenotypic clines in urban ecosystems by sampling the frequency of a Mendelian-inherited trait—cyanogenesis—in white clover (Trifolium repens L.) populations along urbanization gradients in four cities. Cyanogenesis protects plants from herbivores, but reduces tolerance to freezing temperatures. We found that the frequency of cyanogenic plants within populations decreased towards the urban centre in three of four cities. A field experiment indicated that spatial variation in herbivory is unlikely to explain these clines. Rather, colder minimum winter ground temperatures in urban areas compared with non-urban areas, caused by reduced snow cover in cities, may select against cyanogenesis. In the city with no cline, high snow cover might protect plants from freezing damage in the city centre. Our study suggests that populations are adapting to urbanization gradients, but regional climatic patterns may ultimately determine whether adaptation occurs.
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Biochar has been used to remediate contaminated-soil with heavy metals, however, less is known on how biochar interacts with planting density and nutrient fluctuation to affect the remediation. A pot ...experiment was conducted in the greenhouse to investigate the effects of biochar application (without vs. with 1% biochar, g/g substrate), nutrient fluctuation (constant vs. pulsed) and planting density (1-, 3- and 6-individuals per pot) on the growth, and cadmium (Cd) and nutrient uptake of
Trifolium repens
population. Our results found that the growth of
T. repens
population increased significantly with increasing planting density, and the increment decreased with increasing planting density. Both the Cd and nutrient uptake were higher at higher planting density (e.g., 3- and 6-individuals) than at lower planting density (e.g., 1-individual). Biochar application increased the biomass and shoot Cd uptake, but decreased the ratio of root to shoot and root Cd uptake of
T. repens
population, the effects of which were significantly influenced by planting density. Although nutrient fluctuation had no effect on the growth of
T. repens
population, but its interaction with planting density had significant effects on Cd uptake in tissues. Overall, the effects of biochar application and nutrient fluctuation on the growth and Cd uptake were both influenced by planting density in the present study. Our findings highlight that biochar application and constant nutrient supply at an appropriate planting density, such as planting density of 3-individuals per pot in the present study, could promote the growth, and Cd and nutrient uptake of
T. repens
population.
Nitrous oxide (N2O) is a potent greenhouse gas (GHG) emitted from agricultural soils and is influenced by nitrogen (N) fertiliser management and weather and soil conditions. Source partitioning N2O ...emissions related to management practices and soil conditions could suggest effective mitigation strategies. Multispecies swards can maintain herbage yields at reduced N fertiliser rates compared to grass monocultures and may reduce N losses to the wider environment. A restricted-simplex centroid experiment was used to measure daily N2O fluxes and associated isotopomers from eight experimental plots (7.8 m2) post a urea-N fertiliser application (40 kg N ha−1). Experimental pastures consisted of differing proportions of grass, legume and forage herb represented by perennial ryegrass (Lolium perenne), white clover (Trifolium repens) and ribwort plantain (Plantago lanceolata), respectively. N2O isotopomers were measured using a cavity ring down spectroscopy (CRDS) instrument adapted with a small sample isotope module (SSIM) for the analysis of gas samples ≤20 mL. Site preference (SP = δ15Nα – δ15Nβ) and δ15Nbulk ((δ15Nα + δ15Nβ) / 2) values were used to attribute N2O production to nitrification, denitrification or a mixture of both nitrification and denitrification over a range of soil WFPS (%). Daily N2O fluxes ranged from 8.26 to 86.86 g N2O-N ha−1 d−1. Overall, 34.2% of daily N2O fluxes were attributed to nitrification, 29.0% to denitrification and 36.8% to a mixture of both. A significant diversity effect of white clover and ribwort plantain on predicted SP and δ15Nbulk indicated that the inclusion of ribwort plantain may decrease N2O emission through biological nitrification inhibition under drier soil conditions (31%–75% WFPS). Likewise, a sharp decline in predicted SP indicates that increased white clover content could increase N2O emissions associated with denitrification under elevated soil moisture conditions (43%–77% WFPS). Biological nitrification inhibition from ribwort plantain inclusion in grassland swards and management of N fertiliser source and application timing to match soil moisture conditions could be useful N2O mitigation strategies.
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•N2O samples from static chambers (<20 ml) analysed using novel CRDS technique.•Site preference (‰) and soil WFPS (%) used to determine N2O production pathways.•Daily N2O fluxes attributed to 34.2% nitrification and 29.0% denitrification.•δ15Nbulk and SP (drier soil) indicate ribwort plantain may inhibit nitrification.•SP drop with increasing WC (wet soil) implies stimulation of denitrification.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Estrategias para mejorar los pastizales altoandinos Lima Molina, Nila; Aguirre Terrazas, Lucrecia; Flores Mariazza, Enrique
Revista de investigaciones veterinarias del Perú,
06/2020, Volume:
31, Issue:
2
Journal Article
Un estudio de campo fue conducido para evaluar el impacto de la fertilización fosforada y la introducción del trébol blanco (Trifolium repens) en praderas naturales dominadas por Festuca ...dolichophylla (festuca). El área de estudio estuvo ubicado a 4500 msnm, en el sector Ayaracra, región Pasco, la cual corresponde a la eco región Puna del Perú. El diseño experimental fue factorial 2x2x5 en bloques con dos niveles de fósforo (0 y 80 kg/ha), dos distanciamientos entre puntos de siembra (0.5 y 1.0 m) y cinco épocas climáticas de crecimiento. Se evaluó la altura de planta, expansión foliar, vigor (volumen, altura), peso de la planta (g/m2), numero de cabezas florales (inflorescencias), grado de nodulación, contenido de nitrógeno en la hojas y tallos de festuca y contenido de nitrógeno en el suelo con presencia de trébol. La fertilización con fósforo (80 kg/ha) y el distanciamiento de siembra (0.5 cm) mostraron un efecto significativo en la altura, expansión foliar y grado de nodulación del trébol. En la festuca, la fertilización fosforada mostró una mejora significativa en el volumen y altura de planta, el distanciamiento de siembra de 0.5 cm mejoró el número de inflorescencias, y el distanciamiento a 1 m mejoró la altura. La precipitación (durante el pico de lluvia) favoreció la respuesta de expansión foliar y altura de planta del trébol y festuca.
•First study of functional properties in novel hybrids for drought-exposed pastures.•The stress-resistant BC1 hybrids were able to maintain photosynthesis under drought.•Drought resistance in BC1 ...hybrids was related to high constitutive kaempferol levels.•BC1 hybrids also showed the highest increases of hydroxycinnamic acids under drought.•BC1 families with high levels of specific phenolics can be used for plant improvement.
This study investigated drought responses in first (BC1) and second (BC2) backcross generation hybrids of Trifolium repens L.×T. uniflorum L., and compared these to high-yielding T. repens L. (white clover) cultivars. Plant attributes included accumulation of leaf phenolics as well as other biochemical and physiological water stress responses. Measurements were made across broad clover types as well as on a subset of related material. Under drought, net photosynthesis decreased by 44–48% and transpiration rates decreased by 60% in the BC2 family and in the white clover parent, but were unaltered in the BC1 family. Drought-induced decreases in leaf water potential were more pronounced in the BC1 family (−47%) than the BC2 (−31%) and parental (−28%) material. Quercetin glycoside accumulation generally increased 2–3 fold under drought. Compared with the BC2 family and with parent plants, the BC1 family had 2.5–4x higher constitutive kaempferol glycoside levels, and 1.5–2.5x higher kaempferol glycoside accumulation under drought. Constitutive kaempferol glycoside accumulation was related to reduced senescence and to less pronounced decreases in shoot DW under drought stress. Hydroxycinnamic acid accumulation increased by 56–73% under water stress, particularly for the BC1 generation. These results identify physiological and biochemical traits that help explain drought resistance of T. repens×T. uniflorum hybrids. The findings suggest merit for the selection of BC1 families with increased accumulation of protective phenolic compounds in breeding programmes for improved drought resistance.
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The legumes white melilot (Melilotus albus ʻMebaʼ) and white clover (Trifolium repens ʻJuraʼ) were tested for their suitability as intercrops for fast growing poplar hybrids grown as short rotation ...coppice (Populus nigra × P. maximowiczii ʻMax-4ʼ, P. maximowiczii × P. trichocarpa ʻNE-42ʼ and P. trichocarpa × P. koreanaʻP-468ʼ). Legumes were sown in the established poplar plantation after its first harvest (5 years after the establishment of the plantation) and their effect on soil nitrogen, vegetation undergrowth and poplar growth was monitored for two years. All three parameters were influenced by the legume intercrops but the effect depended on the poplar clone, legume species and their interaction. In P-468 white clover lowered inter-year decline of soil nitrogen content, increased the Ellenberg indicator value for nutrients and promoted height increment. Such an effect was not detected in the other two poplar hybrids probably due to insufficient establishment of clover. Plots sown with legumes and subjected to weeding exhibited profound differences of the understorey vegetation compared to controls. The difference persisted even during the second year after legume growth had largely receded. Our results indicate a short-term potential of white clover to contribute to poplar growth, and N supply in poplar plantations. Further studies should explore the benefits of clover intercropping from a long-term perspective, with additional poplar clones and under different climate-soil conditions.
•Co-cultivation of white clover (Trifolium repens ʻJura’) with hybrid poplar P. trichocarpa × P. koreana ʻP-468′ improved soil nitrogen and poplar growth.•Though transient the presence of white clover had high impact on poplar plantation understorey composition.•N-fixing white clover significantly promoted nitrophilous species as indicated by the Ellenberg indicator value for nutrients.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
There is growing evidence for the convergent evolution of physically linked gene clusters encoding chemical defense pathways. Metabolic clusters are proposed to evolve because they ensure ...co-inheritance of all required genes where the defense is favored, and prevent inheritance of toxic partial pathways where it is not. This hypothesis rests on the assumption that clusters evolve in species where selection favors intraspecific polymorphism for the defense; however, they have not been examined in polymorphic species.
We examined metabolic cluster evolution in relation to an adaptive polymorphism for cyanogenic glucoside (CNglc) production in clover. Using 163 accessions, we performed CNglc assays, BAC sequencing, Southern hybridizations and molecular evolutionary analyses.
We find that the CNglc pathway forms a 138-kb cluster in white clover, and that the adaptive polymorphism occurs through presence/absence of the complete cluster. Component genes are orthologous to those in the distantly related legume Lotus japonicus.
These findings provide empirical support for the co-inheritance hypothesis, and they indicate that adaptive CNglc variation in white clover evolves through recurrent deletions of the entire pathway. They further indicate that the shared ancestor of many important legume crops was likely cyanogenic and that this defense was lost repeatedly over the last 50 Myr.
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In order to understand the degradation of different residual pesticides of white clover silage and their influence on silage quality, three commonly used orchard pesticides with different ...concentrations were added to the white clover and fermented for 90 days. The results showed that the degradation rate of cypermethrin and its toxic degradation product 3-phenoxybenzoic acid (3-PBA) was the highest after silage, at different concentrations, both were 100%. The degradation rate of Tebuconazole and chloropyridine was 72.47–80.27% and 47.76–64.82%, of which 3,5,6-trichloro-2-pyridinol (TCP) content, poisonous toxic degradation product, increased 0.0525–0.253 mg·kg−1. The residues of beta-cypermethrin and tebuconazole had reached safety standards after silage. As compared with the control, the contents of lactic acid, acetic acid, and propionic acid increased in the treated samples. The higher concentrations of three pesticides all significantly reduced the lactic acid content of silage (p<0.05). Pesticides had different effects on the nutritional components of white clover silage. Conclusively, silage is a potential way to expand the utilization of covering plants in orchards.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Mining environmental liabilities generate environmental pollution. The objective of the present study was to determine the yield of white clover (Trifolium repens) and orchard grass (Dactylis ...glomerata) cultivated in mining environmental passives adding black earth and compost as a substrate in the Buenaventura Julcani Huancavelica Company. The treatments were the combinations: 4: 3.1: 3.1: 3:1.1 kg of RP: RP, TN: RP, C: RP, TN, C respectively. They were distributed in four treatments with twelve experimental units for each species of leguminous and gramineous grass, we worked according to the completely randomized design (DCA) with a 2 x 4 factorial arrangement, the experimental unit being a treatment with twelve repetitions. The variables evaluated were: germination percentage (TG) and stem survival percentage (TST). For the statistical analysis, the SPSS software was used.
Several studies have reported positive effect of cover crop on topsoil physical properties as well as weed suppression, but few have quantified its effect on Fusarium head blight prevention. This ...study explored the effect of white mustard (Sinapis alba L.) and white clover (Trifolium repens L.) as cover crops on weed pressure and Fusarium infestation in spring wheat and spring barley grain under different tillage systems.
Five tillage practices were investigated in a loam soil in long term tillage experiment in Central Lithuania in Dotnuva: deep ploughing (22–24 cm), shallow ploughing (16–18 cm), shallow harrowing (8–10 cm), deep harrowing (14–16 cm) and direct drilling, with and without cover crop. Cover crops were sown using fertilizer spreader: white mustard seed were spread before harvest of the spring wheat and spring barley in 2013 and 2014, respectively and white clover – at the beginning of vegetation of winter oilseed rape in early spring, in 2017. Cover crops effect on Fusarium fungi was evaluated in spring cereals grown after the cover crop: in spring barley in 2014 and in spring wheat in 2018.
Both cover crops resulted in lower weed pressure for a post - harvest period under different tillage practises. White mustard suppressed weed air-dry mass up to 90 and white clover up to 99 percent. White mustard has influenced the decrease of Fusarium graminearum contamination in spring barley grain as well as white clover reduced F. culmorum infestation level in spring wheat grain. Our results suggest that white mustard and white clover as cover crops might be an option for integrated pest management in order to supplement weed control strategy and Fusarium head blight prevention under sustainable tillage practises.
•Cover crops decreased weed infestation for a post-harvest period.•White mustard reduced grain contamination by Fusarium graminearum in spring barley.•White clover negatively affected Fusarium culmorum infestation in spring wheat grain.•Cover crops may supplement integrated pest management for weed and FHB control.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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