Elaeagnus angustifolia Elevates Soil Inorganic Nitrogen Pools in Riparian Ecosystems

Elaeagnus angustifolia L., a nonnative N₂-fixer, has established within riparian corridors of the interior western United States and is now the fourth most frequently occurring woody riparian plant in this region. We examined whether E. angustifolia alters pools and fluxes of soil inorganic N at eight sites dominated by Populus deltoides ssp. wislizeni along the Rio Grande in New Mexico over 2 years. E. angustifolia contributed a small fraction of total leaf fall (<5% across sites) but accounted for a disproportionately high amount of N (19%) that entered the system from P. deltoides and E. angustifolia leaf fall, due to the high N content (>2%) of E. angustifolia senesced leaves. Soil inorganic N concentrations and potential rates of nitrification and net N mineralization varied across sites. E. angustifolia leaf fall explained 59% of the variation in soil inorganic N concentrations across years. This relationship suggests that inputs of N-rich leaf litter from E. angustifolia may increase N availability in riparian soils. We detected no relationship between E. angustifolia leaf fall and fluxes of soil inorganic N, whereas others have measured both stimulation and inhibition of soil N cycling by E. angustifolia. Greater abundance of N₂-fixing species in riparian forests may augment growth of neighboring plants or increase N export to rivers. Given these possibilities, ecosystem studies and restoration projects should further examine the potential for E. angustifolia to affect N pools and fluxes along western North American rivers.     

Long-term competitive displacement of Typha latifolia by Typha angustifolia in a eutrophic lake

This study follows the outcome of long-term competition between a broad-leaved and a narrowleaved Typha species, T. latifolia and T. angustifolia respectively, in a eutrophic lake. The lake was bordered by a zone of T. latifolia, at one location interrupted by a T. angustifolia stand. Distributional changes of the T. angustifolia stand and the adjacent zone of T. latifolia were measured on aerial photographs (13 years) and along ground-level transects (6 years). A second stand of T. angustifolia was established with transplanted ramets within a formerly homogeneous zone of T. latifolia, and displacement between the two species was measured along ground-level transects after 6 years. Differences between the species in shoot performance were investigated to help explain the relative competitive abilities of the two Typha species. T. angustifolia expanded at the expense of T. latifolia at all water depths where both species occurred, except in very shallow water. Expansion rates suggest that T. angustifolia was not affected by the presence of T. latifolia in water depths exceeding 0.25 m. The Typha species were significantly negatively associated according to rank correlations of shoot densities, and changes of shoot densities, along the transects. These results suggest that T. angustifolia is competitively superior to T. latifolia, contradicting earlier studies. The higher competitive ability of T. angustifolia is consistent with its having taller shoots and a higher standing crop in early summer. Further, shoot height distributions indicated a closer integration of shoot emergence during spring in T. angustifolia than in T. latifolia. A high leaf area/shoot weight ratio suggest that T. latifolia may instead be relatively fast-growing, achieving competitive superiority over narrower-leaved Typha species during a transient period after simultaneous seedling establishment.     

Allelopathy as a mechanism for the invasion of <Emphasis Type="Italic">Typha angustifolia</Emphasis>

The direct competitive effects of exotic plants on natives are among the leading causes of plant extinctions worldwide. Allelopathy, one type of direct plant competition, has received relatively little research, particularly in aquatic and wetland systems, even though allelopathy can be a potent mechanism through which plant communities are structured. Typha angustifolia (narrow-leaved cattail) is an invasive exotic plant in North America that often forms monocultures in disturbed wetlands and is more invasive than native members of its genus. We tested whether T. angustifolia was allelopathic and whether it produced different biochemicals than a native congener by growing it with the native bulrush Bolboschoenus fluviatilis (river bulrush) in soil with and without activated carbon and by qualitatively and quantitatively comparing soluble phenolics produced in the roots of T. angustifolia and the native Typha latifolia (broad-leaved cattail). T. angustifolia had a strong allelopathic effect on B. fluviatilis, reducing the longest leaf length and root, shoot, and total biomass of B. fluviatilis. When the allelopathy of T. angustifolia was ameliorated by activated carbon, however, longest leaf length, ramet number, root biomass, shoot biomass, and total biomass of T. angustifolia were greatly reduced due to resource competition with B. fluviatilis. Furthermore, T. angustifolia produced different, but not more, soluble phenolics than T. latifolia suggesting that the identity of the phenolics is different between the two species rather than the concentrations. The allelopathic effects of T. angustifolia on a North American native wetland plant and its production of root biochemicals that appear to differ from those produced by a native congener are consistent with the possibility that T. angustifolia may use a novel allelochemical in its invasion of North American wetlands.     

Microsatellite loci isolated from narrow‐leaved cattail Typha angustifolia

We present 11 dinucleotide microsatellite DNA loci isolated from the narrow‐leaved cattail (Typha angustifolia) and describe conditions for their amplification. The PCR primers were tested on at least 20 individuals of Typha angustifolia and T. latifolia from two Ukrainian populations per species. The primers amplify loci with relatively high numbers of alleles (averaging 7.22 and 4.95 alleles per locus in T. angustifolia and T. latifolia, respectively), and polymorphic information content (averaging 0.61 and 0.46 in T. angustifolia and T. latifolia, respectively).     

The confusion of Agave vivipara L. and A. angustifolia Haw., two distinct taxa

Agave vivipara L. andA. angustifolia Haw., considered conspecific by Wijnands, are shown to be two distinct species. A previous neotypification (as a lectotypification) ofA. angustifolia by Gentry is superseded because it is in conflict with the protologue; a new neotype is designated herein. The economic importance ofA. angustifolia is summarized.     

Influence of Zinnia angustifolia HBK genotype on embryonic and vegetative development of Z. angustifolia x Z. elegans Jacq. interspecific hybrids

Summary Interspecific crosses between Zinnia angustifolia clones (maternal parents) and Z. elegans lines (paternal parents) were performed to investigate postzygotic barriers among Z. angustifolia X Z. elegans hybrids and to determine influence of parental genotype on embryonic and vegetative development of interspecific hybrids. Variation in percentage of emerged seedlings (PES) and percentage of morphologically normal hybrids (PNH) was attributable to Z. angustifolia clones with minor or no effect attributable to Z. elegans lines. Heterogeneity in PES values among Z. angustifolia clones was due to differences in amount of hybrid embryo breakdown and ungerminable seed. Cytological observations of normal and abnormal interspecific hybrids revealed similar chromosome numbers (2n=23) but indicated a low mitotic index for abnormal hybrids. Genetic analysis of PES and PNH suggested control by multiple genes inherited from the Z. angustifolia genome. Adequate sampling of the Z. angustifolia gene pool would permit exploitation of genetic variability present within the species and allow improvements in PES and PNH for interspecific hybrids.Scientific Article No. A-4479, Contribution No. 7472 of the Maryland Agricultural Experiment Station, Department of Horticulture     

Leaf litter of <Emphasis Type="Italic">Kageneckia angustifolia</Emphasis> D. Don (Rosaceae) inhibits seed germination in sclerophyllous montane woodlands of central Chile

Leaf litter accumulation can have either positive, negative or neutral effects on seed germination and seedling recruitment. In montane woodlands of the Mediterranean zone of central Chile, large amounts of leaf litter accumulate beneath the crowns of the summer semi-deciduous tree Kageneckia angustifolia and no regeneration of this or other plant species has been observed beneath this tree throughout the year. In a sample plot of 5000 m² we selected ten K. angustifolia trees and measured (1) leaf litter accumulation beneath and outside canopy; (2) the effects of time elapsed since burial on viability of K. angustifolia seeds with and without a leaf litter cover; (3) field seed germination with presence or absence of leaf litter and (4) the possible chemical effects of K. angustifolia leaf litter leachates on seed germination of its own seeds and of other two co-occurring native shrubs species (Guindilia trinervis and Solanum ligustrinum). Our results show that a considerable accumulation of leaf litter occurred beneath K. angustifolia, and litter negatively affected seed viability and germination of this species in the field. Under laboratory conditions, K. angustifolia leaf litter leachates inhibited seed germination of its own seeds and of the two native shrub species. Chemical effects are likely involved in the negative effects of leaf litter on the recruitment of K. angustifolia in the montane sclerophyllous woodland of central Chile.     

盐分和干旱对沙枣幼苗生理特性的影响

以沙枣(Elaeagnus angustifolia L.)幼苗为实验材料,分别对其进行轻度干旱(土壤含水量7%—9%)、重度干旱(土壤含水量3%—5%)、100 mmol/L NaCl以及100 mmol/L NaCl处理下不同程度的盐旱共胁迫处理,处理2周后测其生理指标,包括生长指标、光合指标、渗透调节指标以及复水后生长指标,研究盐旱共胁迫对沙枣幼苗生理特性的影响。结果表明:和对照相比,轻度干旱对沙枣幼苗的生物量没有显著影响,重度干旱处理明显降低了沙枣的生物量,无论是轻度干旱还是重度干旱,都显著降低了沙枣幼苗的净光合速率、K~+含量,显著增加了Na~+含量、脯氨酸含量、可溶性糖含量、有机酸含量、总酚和类黄酮含量;和对照相比,100 mmol/L NaCl处理显著降低了沙枣幼苗的生物量、净光合速率和K~+含量,显著增加了Na~+含量、脯氨酸含量、可溶性糖含量、有机酸含量、总酚和类黄酮含量;和盐处理相比,轻度干旱和盐分共胁迫对沙枣幼苗的各项指标没有显著差异,而重度干旱和盐分共胁迫明显降低了沙枣幼苗的生物量、净光合速率;复水一周后,只有轻度干旱可以回复到对照水平。以上结果表明,盐分和干旱处理明显抑制了沙枣幼苗的生长,轻度干旱和盐分共胁迫条件下,沙枣幼苗表现出一定的交叉适应现象,而重度干旱却加重了盐害。     

Root aerobic respiration and growth characteristics of three Typha species in response to hypoxia

The responses of root aerobic respiration to hypoxia in three common Typha species were examined. Typha latifolia L., T. orientalis Presl, and T. angustifolia L. were hydroponically cultivated under both aerobic and hypoxic growth conditions to measure root oxygen consumption rates. Hypoxia significantly enhanced the root aerobic respiration capacity of the two deep-water species, T. orientalis and T. angustifolia, while it did not affect that of the shallow-water species, T. latifolia. T. angustifolia increased its root porosity and root mass ratio, while T. latifolia increased its root diameter under the hypoxic growth conditions. The relative growth rates in biomass of T. orientalis and T. angustifolia were 59 and 39% higher, respectively, under the hypoxic growth conditions than under the aerobic growth conditions. In contrast, that of T. latifolia did not differ between the two conditions. In T. orientalis and T. angustifolia, enhanced root aerobic respiration rates under the hypoxic growth conditions would have increased the nutrient uptake, and thus higher relative growth rates were obtained. For the deep-water species, T. orientalis and T. angustifolia, the root aerobic respiration capacity was enhanced, probably in order to maintain the generation of respiratory energy under hypoxia.     

Soil properties and actinorhizal vegetation influence nodulation of Alnus glutinosa and Elaeagnus angustifolia by Frankia

Nodulation (mean number of nodules per seedling) was 5 times greater for Elaeagnus angustifolia than for Alnus glutinosa overall when seedlings were grown in pots containing either an upland or an alluvial soil from central Illinois, USA. However, the upland Alfisol had 1.3 times greater nodulation capacity for A. glutinosa than for E. angustifolia. The presence of A. glutinosa trees on either soil was associated with a two-fold increase in nodulation capacity for E. angustifolia. Nodulation increases for soils under A. glutinosa were obtained for A. glutinosa seedlings in the Alfisol, but decreased nodulation for A. glutinosa seedlings occurred in the Mollisol. Greatest nodulation of E. angustifolia seedlings occurred near pH 6.6 for soil pH values ranging from 4.9 to 7.1, while greatest nodulation of A. glutinosa occurred at pH 4.9 over the same pH range. Nodulation was not affected by total soil nitrogen concentrations ranging from 0.09 to 0.20%. Mollisol pH was significantly lower under A. glutinosa trees than under E. angustifolia trees. For 4- to 8-year-old field-grown trees, A. glutinosa nodule weights were negatively correlated with soil pH, while for similar aged E. angustifolia trees nodulation in the acidic Alfisol was not detected.     

Differential patterns of morphological and molecular hybridization between Fraxinus excelsior L. and Fraxinus angustifolia Vahl (Oleaceae) in eastern and western France

We examined large‐scale patterns of morphology, genetic structure and ecological correlates of Fraxinus excelsior and the closely related species Fraxinus angustifolia in France, in order to determine the degree of hybridization between them. We sampled 24 populations in two putative hybrid zones (Loire and Saône), and five control populations of each species. We measured foliar characteristics of adult trees and used five nuclear microsatellites as molecular markers. Canonical discriminant analysis indicated that the two species differ in morphology, but that intermediate types are common in the Loire region but less frequent in the Saône region. Bayesian population assignment identified one F. angustifolia and two F. excelsior gene pools. Most Loire individuals clustered genetically with the F. angustifolia gene pool. In contrast, the Saône region presented individuals belonging mostly to F. excelsior pools, although the F. angustifolia type was frequent in certain populations. The lowest F_ST values were found between the Loire and F. angustifolia controls that also exhibited no significant isolation by distance. The proportion of the F. angustifolia gene pool in each locality was negatively correlated with winter temperatures, suggesting that a cold climate may be limiting. Hybridization is probably favoured by the intermediate climatic conditions in the Loire region that allow both species to occur, but is somewhat hampered by the harsher winters in the Saône area where morphological introgression has apparently not yet occurred.     

Seasonal cambium activity in the subtropical rain forest tree Araucaria angustifolia

Information on the timing and dynamics of tree ring formation is essential to assess the seasonal behavior of secondary wood growth and its associated environmental influences. Araucaria angustifolia is a dominant species in highland pluvial ecosystems of southeastern South America. Previous investigations indicated that their growth rings are formed annually, but no information exists about the timing of growth ring formation and the environmental triggers influencing cambium activity. In this paper we examine inter- and intra-annual cambial activity in A. angustifolia, through anatomical and dendrochronological evidence at two study sites, and model the relationships between regional climate variation and intra-annual tree ring formation. The results confirm the annual growth ring formation in A. angustifolia and indicate that its growth season extends from October to April. Day length and temperature were the main environmental factors influencing the seasonal cambium activity. Our results evidence the dendrochronological potential of A. angustifolia for ecological and climatological studies in southeastern South America.     

Interspecific differences in radial oxygen loss from the roots of three <Emphasis Type="Italic">Typha</Emphasis> species

A comparison was made of the radial oxygen loss (ROL) from the roots of three Typha species, Typha latifolia L., Typha orientalis Presl and Typha angustifolia L., which resemble each other in morphology. ROLs were evaluated in the laboratory for seedlings of T. orientalis and T. angustifolia in order to compare them with the ROL value for T. latifolia obtained in our previous study. Measurements were conducted using the highly oxygen-sensitive anthraquinone radical anion as an oxygen indicator, which enabled us to simulate the natural conditions in which the oxygen released from the root is immediately consumed by the soil. Among the three Typha species, the ROL was the highest in T. angustifolia, followed by T. latifolia and T. orientalis. Illumination significantly enhances the ROL of T. orientalis, and this effect was also observed for T. latifolia in our previous study, whereas it did not affect the ROL of T. angustifolia. These results indicate that ROL differs significantly between species, even among members of the same genus that are similar in morphology.     

Soils as agents of selection: feedbacks between plants and soils alter seedling survival and performance

Soils are one of the first selective environments a seed experiences and yet little is known about the evolutionary consequences of plant-soil feedbacks. We have previously found that plant phytochemical traits in a model system, Populus spp., influence rates of leaf litter decay, soil microbial communities and rates of soil net nitrogen mineralization. Utilizing this natural variation in plant-soil linkages we examined two related hypotheses: (1) Populus angustifolia seedlings are locally adapted to their native soils; and (2) Soils act as agents of selection, differentially affecting seedling survival and the heritability of plant traits. We conducted a greenhouse experiment by planting seedlings from 20 randomly collected P. angustifolia genetic families in soils conditioned by various Populus species and measured subsequent survival and performance. Even though P. angustifolia soils are less fertile overall, P. angustifolia seedlings grown in these soils were twice as likely to survive, grew 24% taller, had 27% more leaves, and 29% greater above-ground biomass than P. angustifolia seedlings grown in non-native P. fremontii or hybrid soils. Increased survival resulted in higher trait variation among seedlings in native soils compared to seedlings grown in non-native soils. Soil microbial biomass varied significantly across soil environments which could explain more of the variation in seedling performance than soil texture, pH, or nutrient availability, suggesting strong microbial interactions and feedbacks between plants, soils, and associated microorganisms. Overall, these data suggest that a “home-field advantage” or a positive plant soil feedback helps maintain genetic variance in P. angustifolia seedlings.     

Ecological interpretation of multiple population size structures in trees: The case of Araucaria angustifolia in South America

Abstract In this paper I examined the usefulness of tree population size distributions in evaluating the conservation status of populations of an endangered tree species. I set expectations derived from two complimentary views of the ecology of rainforest trees and examined whether they were met by size distributions of populations of the South American dominant conifer Araucaria angustifolia and its relationship with forest structural characteristics. Specifically, I evaluated the expectations that (i) A. angustifolia trees have larger diameter than average angiosperm trees and form a higher monospecific canopy layer above the shorter angiosperm canopies; (ii) A. angustifolia populations are characterized by size distributions with many large individuals and a long tail of relatively rare, small individuals (have symmetry coefficient <0); (iii) the symmetry of the size distribution of A. angustifolia populations is negatively related to the abundance of large (d.b.h. ≥ 10.0 cm) individuals in the population; and (iv) the abundance of A. angustifolia trees is negatively related to the abundance of angiosperm trees, as the successional accumulation of angiosperm stems would not be accompanied by the recruitment of new A. angustifolia. These expectations were evaluated using data on 25 populations of A. angustifolia sampled in the Rio Grande do Sul State in southern Brazil. The first, third and fourth expectations were met, while the second one was only partially met. This was because populations showed a bimodal distribution regarding symmetry in size distribution, with most populations showing normal or negative symmetry, and those logged, adult‐depleted populations showing positive skewness.     

Dominance of non-native riparian trees in western USA

Concern about spread of non-native riparian trees in the western USA has led to Congressional proposals to accelerate control efforts. Debate over these proposals is frustrated by limited knowledge of non-native species distribution and abundance. We measured abundance of 44 riparian woody plants at 475 randomly selected stream gaging stations in 17 western states. Our sample indicates that Tamarix ramosissima and Elaeagnus angustifolia are already the third and fourth most frequently occurring woody riparian plants in the region. Although many species of Tamarix have been reported in the region, T. ramosissima (here including T. chinensis and hybrids) is by far the most abundant. The frequency of occurrence of T. ramosissima has a strong positive relation with the mean annual minimum temperature, which is consistent with hypothesized frost sensitivity. In contrast the frequency of occurrence of E. angustifolia decreases with increasing minimum temperatures. Based on mean normalized cover, T. ramosissima and E. angustifolia are the second and fifth most dominant woody riparian species in the western USA. The dominance of T. ramosissima has been suspected for decades; the regional ascendance of E. angustifolia, however, has not previously been reported.     

Morphological adaptations of emergent plants to water flow: a case study with Typha angustifolia, Zizania latifolia and Phragmites australis

1. Water velocity plays an important role in shaping plant community structure in flowing waters although few authors have yet attempted to explain the adaptation of plants to flow. 2. We aimed to test two hypotheses, that: (i) some emergent macrophytes reconfigure their shoot distribution in fast currents and form clumps, and (ii) the shape and morphology of such clumps minimises drag caused by the current. The study focuses on three emergent macrophytes that co‐occur along a gradient of water velocity. 3. The species showed a clear zonation in response to water depth and current velocity. Phragmites australis occupied shallower and more slowly flowing water than Typha angustifolia and Zizania latifolia, which had similar preferences. 4. Both T. angustifolia and Z. latifolia shoots were more clumped at high velocity, whereas they were more randomly distributed at low flow or in stagnant water. Because of the low shoot density, water flowed more easily through T. angustifolia clumps, whereas Z. latifolia clumps had a high shoot density and large amounts of trapped litter, causing stagnant water in the centre of the clump. The clumps of Z. latifolia with a high density of shoots were longer and narrower than T. angustifolia clumps. Phragmites australis was less tolerant of flow than the other two species and large amounts of litter trapped in the clumps impaired flow. 5. The shoot distribution of both T. angustifolia and Z. latifolia is reconfigured at high flow and this minimises drag on the clumps.     

Control of resin production in Araucaria angustifolia,an ancient South American conifer

Araucaria angustifolia is an ancient slow‐growing conifer that characterises parts of the Southern Atlantic Forest biome, currently listed as a critically endangered species. The species also produces bark resin, although the factors controlling its resinosis are largely unknown. To better understand this defence‐related process, we examined the resin exudation response of A. angustifolia upon treatment with well‐known chemical stimulators used in fast‐growing conifers producing both bark and wood resin, such as Pinus elliottii. The initial hypothesis was that A. angustifolia would display significant differences in the regulation of resinosis. The effect of Ethrel^® (ET – ethylene precursor), salicylic acid (SA), jasmonic acid (JA), sulphuric acid (SuA) and sodium nitroprusside (SNP – nitric oxide donor) on resin yield and composition in young plants of A. angustifolia was examined. In at least one of the concentrations tested, and frequently in more than one, an aqueous glycerol solution applied on fresh wound sites of the stem with one or more of the adjuvants examined promoted an increase in resin yield, as well as monoterpene concentration (α‐pinene, β‐pinene, camphene and limonene). Higher yields and longer exudation periods were observed with JA and ET, another feature shared with Pinus resinosis. The results suggest that resinosis control is similar in Araucaria and Pinus. In addition, A. angustifolia resin may be a relevant source of valuable terpene chemicals, whose production may be increased by using stimulating pastes containing the identified adjuvants.     

Is <Emphasis Type="Italic">Campanula glomerata</Emphasis> Threatened by Competition of Expanding Grasses?

In East Germany, a high percentage of species-rich, semi-natural dry grasslands has been converted into species-poor communities dominated either by Poa angustifolia or Festuca rupicola. The disappearance of low-intensity types of agricultural land-use such as mowing and grazing has been the cause for the decline of many grassland species, as lack of biomass extraction leads to a new situation in competition. Here we evaluate the performance of the rare forb Campanula glomerata in competition with P. angustifolia and F. rupicola using a replacement design experiment. C. glomerata responded to the presence of these grass species in contrasting ways: whereas the presence of P. angustifolia had a negative effect on C. glomerata biomass and fitness, the presence of F. rupicola affected the forb in a positive way. The results of an additional sowing experiment revealed that the germination and establishment rates of C. glomerata decrease in accordance with increasing density of P. angustifolia. Thus the response of this rare forb varies among neighbour species.     

Self-incompatibility and interspecific incompatibility: relationships in intra- and interspecific crosses of Zinnia elegans Jacq. and Z. angustifolia HBK (Compositae)

Summary Intraspecific and reciprocal interspecific crosses involving Zinnia angustifolia clones and Z. elegans lines showed that in both species, sporophytic self-incompatibility (SI) systems were present. Intensity of SI varied among clones and lines, and high self seed set was associated with a concomitant decrease in callose fluorescence in papillae and pollen tubes. Incomplete stigmatic inhibition of pollen germination and tube growth was observed in reciprocal interspecific crosses and associated with callose synthesis, suggesting S-gene activity. Seed set and progeny obtained following Z. angustifolia×Z. elegans matings was comparable to intraspecific compatible matings of Z. angustifolia although the rate of pollen tube growth through the style was slower. In Z. elegans × Z. angustifolia matings, additional prezygotic barriers were present and acted between pollen tube penetration of the stigma and syngamy. SI X SI interspecific incompatibility was essentially unilateral, with no embryos or progeny obtained when Z. elegans was the pistillate parent. It was hypothesized that nonfunctioning of Z. elegans × Z. angustifolia crosses was due to S-gene expression at the stigmatic surface and to other isolating mechanisms in the stylar or ovarian transmitting tissue.Scientific Article No. A-4448, Contribution No. 7439 of the Maryland Agricultural Experiment Station, Department of HorticultureA portion of this paper was presented in the report: Boyle TH, Stimart DP (1986) Incompatibility relationships in intra- and interspecific crosses of Z. elegans Jacq. and Z. angustifolia HBK (Compositae). In: Mulcahy D (ed) Biotechnology and ecology of pollen. Springer, New York