Spring Annuals Research Articles

New segetal communities of sunflower crops in the Orenburg Region

The diversity of weed-field communities of sunflower crops within the forest-steppe zone of the Orenburg Region (Abdulinskiy, Matveevskiy, Oktyabrskiy, Aleksandrovskiy, Sharlykskiy districts) was studied. The communities in the system of ecological-floristic classification units are assigned to the new variant Orobanche cumana of the Amarantho blitoides Lactucetum tataricae Khasanova et al. 2019. In the core of the cenoflora of communities juvenile weed species prevail. The most active of them are late spring annuals (Amaranthus blitoides, Panicum miliaceum, Amaranthus retroflexus, Setaria viridis) and early spring annuals (Chenopodium album, Fallopia convolvulus, Camelina microcarpa). Root perennials such as Lactuca tatarica, Convolvulus arvensis, Euphorbia virgata, Cirsium arvense have also a high proportion. A distinctive feature of the communities is the participation in their floristic composition of a dangerous quarantine species Sunflower broomrape (Orobanche cumana). Modeling the area of the association under a moderate scenario of climate change shows that the distribution of communities by 2050 can cover almost the entire territory of the Cis-Urals (within the Republic of Bashkortostan). It is necessary to organize a monitoring system for the range of these communities in the Southern Urals.

Foliar nutrient resorption responses of three life-form plants to water and nitrogen additions in a temperate desert

How nitrogen deposition and increasing precipitation would affect leaf nutrient concentration and internal nutrient cycling of desert plants is still unclear. The aim of our study was to test the responses of leaf nutrient resorption to increasing precipitation and N enrichment in a temperate desert. Green and senesced leaf nitrogen and phosphorus concentrations, and nitrogen (NRE) and phosphorus (PRE) resorption efficiency of three life-form plants (5 spring annuals, 2 summer annuals and 2 shrubs) were investigated. Both NRE and PRE showed remarkable variations among plant life-forms, being lowest in shrubs and highest in spring annuals, suggesting that plants may have different nutrient requiring strategies. Nitrogen addition promoted green and senesced leaf nitrogen concentrations in summer annuals and shrubs, while having no impacts on leaf phosphorus concentration, NRE and PRE. Water addition had no impacts on leaf nutrient concentration and resorption efficiency; combined nitrogen and water addition had no interactive effects. Our results suggest that spring annuals and shrubs exhibit conservative nutrient adaptation through increasing nutrient uptake but not changing nutrient internal cycle to increasing nitrogen and water.

Phenological transition dictates the seasonal dynamics of ecosystem carbon exchange in a desert steppe

AbstractQuestionThere are large variations in ecosystem carbon (C) exchange in desert ecosystems; however, few studies have examined the effects of community phenological staging on seasonal variations of ecosystem C exchange. We asked whether factors that control temporal changes in net ecosystem C exchange (NEE) vary with an obvious community transition from spring annuals to summer annuals and perennials in a temperate desert steppe.LocationSouth margin of the Gurbantunggute Desert, northwestern China.MethodsEcosystem C and water exchange were measured regularly using closed static chambers and analysed at daily and seasonal intervals. Soil moisture and temperature, photosynthetically active radiation (PAR) and plant biomass were also investigated.ResultsSoil temperature had a dominant influence on C release into the atmosphere from the ecosystem during the snowmelting phase (mid‐March to early April). In the spring annual dominant phase (mid‐April to early June), the diurnal pattern of NEE was consistent with the pattern of PAR. The ecosystem became a weak C resource (0.16 ± 0.03 μmol CO2 m−2·s−1) and NEE was positively correlated with community biomass during this phase. In the summer annual and perennial dominant phase (late June to late September), NEE showed relatively large C release (0.74 ± 0.03 μmol CO2 m−2·s−1) and was negatively correlated with soil temperature.ConclusionOur results indicate that the primary abiotic factor controlling NEE varies throughout the year, and NEE is determined by the interaction of a plant functional group with precipitation and temperature.

Plant functional trait responses to interannual rainfall variability, summer drought and seasonal grazing in Mediterranean herbaceous communities

Summary 1. Some plant functional traits evolved with high temporal resource variability and disturbance in ecosystems where these factors are prevalent. Persistence of characteristics of these functional traits in ecosystems may depend on continued resource variability and disturbance, which in turn may promote functional diversity. In Mediterranean ecosystems, experiments that eliminate temporal resource variability and disturbance are needed to detect functional trait dependence on these factors. 2. The purpose of this study was to experimentally assess how interannual rainfall variability, summer drought and seasonal grazing modify the characteristics of functional traits (life span, flowering time, seed size and plant size) in old-field (6–15 years) Mediterranean herbaceous communities. 3. We designed a 9-year factorial field experiment that manipulated Mediterranean rainfall variability in three ways: (i) constant water availability with no summer drought; (ii) autumn and spring water availability but with summer drought; and (iii) no water supplied to rainfall; and grazing regimes: (i) autumn grazing; (ii) spring grazing; and (iii) non-grazing, in each of the three scenarios of water availability. At a community scale, we measured abundance of different categories within four plant functional traits: plant life span (annual and perennial), flowering time of annuals (spring and summer) and seed and plant sizes of spring annuals (small and large). 4. Interannual rainfall variability in autumn and spring (IRVAS), summer drought and grazing reduced perennial cover. IRVAS was necessary for the persistence of small-seeded and small-size spring annuals. IRVAS and summer drought increased spring annuals in grazed treatments. 5. Results suggest that IRVAS, summer drought and grazing favour the coexistence of species, through improved functional diversity in seed and plant sizes and increased abundance of spring annuals, the most species-rich functional group. Both effects may be the reason for the high species richness in grazed Mediterranean herbaceous communities.

Natural Variation of Flowering Time and Vernalization Responsiveness in Brachypodium distachyon

Dedicated bioenergy crops require certain characteristics to be economically viable and environmentally sustainable. Perennial grasses, which can provide large amounts of biomass over multiple years, are one option being investigated to grow on marginal agricultural land. Recently, a grass species (Brachypodium distachyon) has been developed as a model to better understand grass physiology and ecology. Here, we report on the flowering time variability of natural Brachypodium accessions in response to temperature and light cues. Changes in both environmental parameters greatly influence when a given accession will flower, and natural Brachypodium accessions broadly group into winter and spring annuals. Similar to what has been discovered in wheat and barley, we find that a portion of the phenotypic variation is associated with changes in expression of orthologs of VRN genes, and thus, VRN genes are a possible target for modifying flowering time in grass family bioenergy crops.

Fire in Chihuahuan Desert grassland: Short-term effects on vegetation, small mammal populations, and faunal pedoturbation

A prescribed burn resulted in significant decreases in canopy cover of the grasses: Bouteloua eriopoda, Sporobolus flexuosus, and Aristida purpurea. One year post-burn, basal cover of B. eriopoda remained significantly lower in burned patches than in unburned areas but there were no differences in basal cover of the other perennial grasses. Only one species of the 14 summer annual species occurred in both burned and unburned plots. There were six species of spring annuals in burned patches but no spring annuals in the unburned grassland ten months post-burn. Fire killed 100% of the snakeweed shrubs ( Gutierrezia sarothrae), 77% of the Ephedra torreyana shrubs, and 36% of the Yucca elata. All mesquite shrubs that were top-killed by fire, resprouted one month post-burn. Fire had no effect on abundance and species richness of rodents. There were fewer wolf spider, Geolycosa spp. burrows in burned areas than in unburned grassland. The area and volume of soil in termite galleries and sheeting were significantly larger in the unburned grassland than in the burned areas.

Weed suppression by soil steaming in combination with activating compounds

SummaryThe aim of this study was to determine the weed suppression potential of soil steaming plus activating compounds (KOH or CaO) to boost soil temperature. Different combinations between the compounds and rates were tested in experiments carried out in the field and in a controlled environment. Treatment effects were assessed on field weed vegetation and on seedbank and seedling emergence of three winter (Alopecurus myosuroides, Matricaria chamomilla and Raphanus raphanistrum) and four spring annuals (Amaranthus retroflexus, Echinochloa crus‐galli, Fallopia convolvulus and Setaria viridis), were assessed on field weed vegetation. Neither maximum soil temperature (from 72 to 85°C) nor duration of high temperature in the 3 h following application consistently affected weed suppression. In the field, no significant effects on total weed density were recorded, but there were some significant effects on individual species. The weed seedbank was clearly suppressed by activated steaming: total seedling emergence was inversely related to increasing KOH rates both in the 0–10 and 10–20 cm soil layers, while for CaO the relationship was significant only in the 0–10 cm layer. Winter annuals were more sensitive to KOH than CaO and spring annuals had a more pronounced species‐specific response to treatments. There was a strong negative relationship between compound rate and seedling emergence for all species. Alopecurus myosuroides was the most sensitive to the steam‐alone treatment (77% reduction), whereas M. chamomilla and E. crus‐galli were the least sensitive. Results from this study indicate that the type and rates of activating compounds for soil steaming must be adjusted to the weed community composition.

Macrofossil evidence for pre‐settlement vegetation of Central Otago's basin floors and gorges

Composition of pre‐settlement vegetation communities in the semi‐arid Central Otago lowlands has been one of New Zealand's longstanding ecological puzzles. Uncertainty is due largely to a paucity of fossil data. Here, we provide new evidence for pre‐settlement vegetation in the region based on analyses of plant macrofossils from 15 late Pleistocene and Holocene lowland sites. The assemblages represent two habitat types: wooded or partially wooded intermontane basin‐floor wetlands, and low forest and/or shrubland habitats in the Kawarau and Clutha River gorges. In both habitat types, plant communities appear to have been predominantly woody, with significant components of herbaceous dicotyledons but few grasses. Both habitats seem to have undergone major post‐settlement vegetation transformation. Several presently common taxa were rare or absent before human settlement, but others (including threatened spring annuals), now rare or extinct in the region, were formerly more common.

Maternal Effects and Germination Timing Mediate the Expression of Winter and Spring Annual Life Histories inArabidopsis thaliana

In natural populations of the annual plant Arabidopsis thaliana, season of germination determines life history. Spring annuals overwinter as seeds and germinate and flower in spring. Winter annuals germinate in fall, overwinter as rosettes, and flower in spring. In many plant species, germination is affected by the maternal phenotype during seed production. In those that produce seeds on branches from the main stem and branches from basal nodes, like A. thaliana, there may be positional effects on germination. This study examines the effects of maternal branch type on germination in artificial seasonal spring and fall environments. Seeds from apical and basal branches of 41 accessions of A. thaliana were weighed and divided between spring (low temperature for 21 d) and fall (ambient temperature) germination environments. Maternal branch type had significant effects on germination fraction and seed mass, but the direction of the effect differed among accessions. The genetic correlation between seed mass an...

Acrosymphyton brainardii sp. nov. (Gigartinales, Rhodophyta) from French Frigate Shoals, northwestern Hawaiian Islands

Acrosymphyton brainardii sp. nov. is described from the remote and unpopulated French Frigate Shoals, northwestern Hawaiian Islands. The new species is distinguished from other known species of Acrosymphyton by its extremely long carpogonial and auxiliary-cell branches, uncoiled trichogynes, auxiliary-cell branches organized into dense fascicles, ovoid to ellipsoidal gonimoblasts, and thick outer cortex. Gametophytes are assumed to be spring or summer annuals, because populations disappear during autumn months. Male gametophytes and tetrasporophytes remain unknown.

DETERMINATION OF PHOTOPERIODIC RESPONSE GROUP AND EFFECT OF SUPPLEMENTAL IRRADIANCE ON FLOWERING OF SEVERAL BEDDING PLANT SPECIES

Flower induction of many plant species is synchronized temporally during the year by utilizing changes in day or night length. Commercial potted plant growers have used photoperiod manipulation to induce flowering of short-day plants on a year round basis. A lack of application of photoperiod to manipulate growth of current spring annuals has, in part, been due to the lack of information identifying the photoperiodic classifications of each species. This paper outlines a series of experiments that identified the photoperiodic group classifications and responses to supplemental irradiance of 28 spring annual species. No species studied were identified as obligate short-day plants. Most species were either obligate or facultative long-day plants. Species in which growers have traditionally had difficulty in producing marketable flowering plants in spring tended to be obligate long-day plants. In contrast, a number of species that tend to flower later in the season than desirable were identified as facultative short-day plants. In addition, species varied in their flowering response to supplemental lighting treatments. Leaf number below the first flower was affected by the addition of supplemental lighting under inductive conditions with approximately one half of the species studied.

Variability in soils and vegetation associated with harvester ant (Pogonomyrmex rugosus) nests on a Chihuahuan Desert watershed

The effects of harvester ant (Pogonomyrmex rugosus) nests on the density and cover of spring annual plants and on soil characteristics were measured at three locations characterized by different soils and dominant vegetation on a desert watershed. There were few differences in vegetation and soils associated with harvester ant nests at locations at the base of the watershed where brief periods of flooding and sediment deposition occur at periodic intervals. At mid-slope locations, there were significant increases in total nitrogen, inorganic phosphorus, and cover (biomass) of four species of spring annuals at the edges of nest disks when compared with reference sites. The spring annuals that exhibited increased cover were species that increase biomass as a function of available nitrogen. At a clay-loam, Scleropogon-Hilaria, grassland site, there were significant reductions in the concentrations of Ca2+ and Mg2+, significant increases in nitrate and total nitrogen, but a significant increase in cover in only one species of annual plant. The data demonstrate that the effects of ants on soil properties and vegetation vary with site location and soil type.

Chihuahuan Desert Annuals: Importance of Water and Nitrogen.

We examined the effects of water supplementation and nitrogen amendment on biomass, cover, and density of annual plants on a termite-free and a termite-present area in the Chihuahuan Desert. Soil moisture was higher in the termite than in the termite-free plots, and in the watered than in the unwatered plots during the spring and summer. There were no differences in soil moisture among plots during the winter. Soil nitrogen was higher in the termite-free than in the termite plots. There were no differences in total plant biomass produced in termite and termite-free areas. There were significant differences in relative abundances of species among treatments. natural rainfall was sufficient for maximum spring-annual biomass development on all plots except for the termite-free unfertilized, unwatered plots. These were the driest plots but had high soil nitrogen. Most of the herbaceous species responded to the water amendments by lengthening growing seasons, increasing density, or increasing biomass. When there was sufficient water for most of the spring annuals, high soil nitrogen levels favored increased densities and biomasses of Descurainia pinnata and Lepidium lasiocarpum. The absence of C4 summer annuals in the high-nitrogen plots suggests that relatively high soil nitrogen adversely affected the summer annuals. Termite-free watered plots had higher soil moisture than the termite-unwatered plots, but summer annuals were relatively abundant on the latter. Water amendments had a greater effect on the species abundances in the termite-free area than in the one with termites. In the area with termites, nitrogen amendments had a greater effect on species abundances. Species diversity and richness were affected by fertility as was species composition. This study demonstrates that we must understand patterns of soil nitrogen availability and processes affecting nitrogen availability in addition to water availability, in order to understand productivity and species composition of Chihuahuan Desert annual plants.

Responses of Chihuahuan Desert herbaceous annuals to rainfall augmentation

Densities and biomass of annual herbaceous plants were compared on plots receiving supplemental water of 25 mm at 4-week intervals or 6·3 mm per week, and plots receiving only natural rainfall. During the first summer, there were no significant differences in total biomass between treatments, but the density and biomass of two species, Astragalus tephrodes and Euphorbia micromera, were greater on the watered plots. Several spring annuals responded to supplemental water and by late spring (April) there were decreases in biomass on the watered plots, with the greatest decreases on the 6·3 mm per week plots. Few species of summer annuals responded to supplemental water during the second year, possibly as a result of smaller rain events and/or limitation of available nitrogen. Root shoot biomass ratios were between 0·15 and 0·25 for winter–spring annuals and 0·04 and 0·03 for summer annuals.

SCHMITZIA EVANESCENS SP. NOV. (RHODOPHYTA, GIGARTINALES) A NEW SPECIES OF CALOSIPHONIACEAE FROM THE NORTHEASTERN NEW ZEALAND COAST1

ABSTRACTA new red alga, Schmitzia evanescens sp. nov. (Gigartinales), is described from the northeastern coast of North I., New Zealand. Gametophytes are diminutive, delicate, mucilaginous spring annuals which grow subtidally on cobble substrata. The uniaxial construction and carposporophyte development place this new taxon in the Calosiphoniaceae, a family of only two genera, Calosiphonia H. M. Crouan et P. L. Crouan and Schmitzia P. C. Silva. This is the first report of this family in New Zealand. The new species has vegetative features of both these genera, but is assigned to Schmitzia on the basis of its unusual carposporophyte development in which the gonimoblast initial arises directly from the connecting filament at some distance from the undifferentiated intercalary auxiliary cell. Because recent investigators of other red algal genera with a similar carposporophyte development have questioned the validity of site of gonimoblast initiation as a generic criterion it is suggested that the separation of Schmitzia and Calosiphonia should be re‐evaluated. These and several other genera in the Gymnophlaeaceae, Pseudoanemoniaceae, Dumontiaceae and Gloiosiphoniaceae, can be considered, on morphological and reproductive grounds, to be relatively simple and therefore perhaps primitive members of the Rhodophyta.

Early Spring Herb Communities in Mesophytic Forests of the Great Lakes Region

Herb composition in early spring (before leafout of hardwood overstories) was sampled quantitatively in 60 little—disturbed mesophytic hardwood stands in the Great Lakes region, USA. Disturbed hardwood stands and stands containing evergreens (hemlock) in the overstory were described by releve. Importance of strictly vernal growth forms, early spring annuals and ephemeroid perennials, was correlated with total cover of herbs. In places with nutrient—poor mineral soil, slow rates of litter decomposition, compressed growing season, or evergreen shade, populations of vernal herbs were generally sprase, with summergreen and semi—evergreen taxa relatively important. In mesophytic woods occupying physiographically similar sites, the most significant regional differences in species importance are associated with differences in soil fertility rather than climate. Superimposed on the soil—related, specific compositional differences were gradual, more general, southeast to northwest decreases in species richness, total cover of herbs, and importance of strictly vernal growth forms (annuals and ephemeroids) relative to herbs with summergreen shoots. Within stand, the most significant influences on vernal herb composition were soil drainage and microtopography. Plants with a large proportion of shoots of recent seed origin (annuals and "weedy" perennials) were often strongly dominant in areas with recently exposed mineral soil, as at the edges of receding vernal pools. Plants with large subterranean organs were rare in such sites. Cover of vernal herbs tended to be high on soil mounds and very low in pits, but differences in species composition were not as well defined as they are in large—area uplands vs. broad poorly drained areas. Species abundant on large patches of bare soil (as at the edges of receding vernal pools) also tended to be common in disturbed stands. Long—lived perennials with large storage organs tended to be uncommon in disturbed stands.

Warm Climate Production Guidelines for Angelonia

Angelonia is a popular warm-season annual that has a renewed interest for growers and consumers due to the development of several new cultivars. It is excellent for use in the landscape and in large containers, and is becoming more popular for cut flower use. Known as the summer snapdragon, this plant does best in warm climates, is drought tolerant, and really shines when snapdragons and other spring annuals begin to wither. Older varieties vary in performance. Most are treated as annuals, but in all Florida zones they can be perennial if the winter is mild. This document is ENH 877, one of a series of the Environmental Horticulture Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date October 15, 2002.
 https://edis.ifas.ufl.edu/ep134

Field Experiments for Control of the Beet Leafhopper in Idaho, 1936–37*

The beet leafhopper, Etdettix tenellus (Bak.), is the vector of curly top, a disease of sugar beets, beans, tomatoes, cucurbits and other crops. This insect breeds in desert areas, where it completes the early-summer generation on the spring annuals. These annuals mature about the time the spring generation is developed, and the insect migrates to suitable summer host plants, which are found in certain cultivated and abandoned-farm areas.