Growth Of Herbaceous Plants Research Articles

Growth and reproduction of vascular plants in polluted environments: a synthesis of existing knowledge

Identification of factors explaining diversity in plant responses to industrial pollution is crucial for predicting fates of polluted ecosystems. Meta-analysis based on 203 publications demonstrated that plants growing near point polluters showed similar decreases in characters reflecting growth (–13.1%) and reproduction processes (–8.5%). In herbaceous plants, root growth was reduced, while aboveground biomass did not change, because the decrease in leaf size was compensated by an increase in leaf number. In contrast, woody plants demonstrated no changes in allometry and their growth was reduced to a greater extent than growth of herbaceous plants. Raunkiaer’s classification of life forms appeared the best predictor of species’ responses to pollution. Within woody plants, trees and shrubs, but not dwarf shrubs, showed strong decreases in growth and reproduction. Within herbaceous plants, significant growth reduction was observed only in annuals. Longevity of foliage or plant phylogeny did not explain variation in species’ responses. Adverse effects of pollution were stronger in regions with higher temperature and precipitation, hinting that existing pollution loads may become more harmful for plants as climate changes. Relatively minor explanatory value of the characteristics of individual polluters removes one of the principal obstacles to accounting for the effects of pollution in vegetation models and allows extrapolation of the effects observed near point polluters to both regional and global scales. We conclude that losses in productivity of plant communities due to aerial pollution can be approximately estimated on the basis of the life form spectra and climate.

Effects of Paclobutrazol on Royal Palm (Roystonea regia) Trunk and Height Growth

Paclobturazol is a plant growth regulator which reduces cell elongation and growth. It is commonly used in reducing the growth of herbaceous plants and woody dicots. It has also shown activity against young palms, such as oil and date palms. The effects of basal drench treatments applied annually or as a single application on mature Royal palms (Roystonea regia) were studied over a three-year period. No significant effects were noted on lateral trunk growth. Paclobutrazol treatments resulted in slower vertical growth than in palms not receiving a treatment. However, even at 36 MAT, the average reduction in vertical growth (approx. 50 cm) was still not horticulturally significant relative to the overall palm height of approximately 7 m. Royal palms may attain heights up to 24 m when mature. It is recommended that they not be planted within 7 m of utility lines especially considering regulating their vertical growth is not a practical option.

Competitive responses of seedlings and understory plants in longleaf pine woodlands: separating canopy influences above and below ground

A trenching study was used to investigate above- and below-ground competition in a longleaf pine ( Pinus palustris P. Mill.) woodland. Trenched and nontrenched plots were replicated in the woodland matrix, at gap edges, and in gap centers representing a range of overstory stocking. One-half of each plot received a herbicide treatment to remove the understory. We monitored pine survival and growth, understory productivity, light level (gap fraction), and soil resources. The overstory facilitated pine seedling survival. Pine seedling growth was reduced as overstory stocking increased. Reduced growth of seedlings was also observed in gaps when the understory was left intact. Understory plants competed with seedlings by filling the root gaps that developed as a result of overstory disturbance. Hardwood growth increased in gaps, owing to decreased belowground competition with adult pines, while growth of herbaceous plants and pine seedlings increased with light availability. Large overstory gaps are not required to initiate regeneration in longleaf pine woodlands. Retaining overstory dispersed throughout the stand but variable in density, through single-tree selection approaches, may be an alternative to gap-based approaches. This approach would allow for the fuel continuity needed to sustain the frequent fire required to maintain the diversity characteristic of this type of woodland.

Effects of prescribed fire and fire surrogates on floral visiting insects of the blue ridge province in North Carolina

Pollination by insects in forests is an extremely important process that should be conserved. Not only do pollinating insects help to maintain a diversity of plants within forests, but they also aid in pollinating crops found near forested land. Currently, the effects of various forest management practices on floral visiting insect abundance or diversity is unknown, so we investigated how prescribed burning, mechanical shrub control, and combination of the two affected abundance of floral visiting insects. We caught 7921 floral visitors from four orders and 21 families. Hymenoptera was the most abundant and diverse order, with Halictidae being the most abundant family. A total of 45 species of Hymenoptera representing six families were captured. We caught seven families and 35 species of Lepidoptera, six families and 33 species of Coleoptera, and two families and 13 species of Diptera. Most floral visitors were captured in the mechanical shrub control plus prescribed burn treatments, while lower numbers were caught on the mechanical shrub control only, prescribed burn only and control treatments. Overall species richness was also higher on mechanical plus burn treatments. Total pollinator abundance and the abundance of most orders and families was correlated with decreased tree basal area and increased percent herbaceous plant cover. Our study shows that floral visitors increased in abundance and species richness most from forest disturbance that reduced the density of overstory trees and increased the amount of herbaceous plant growth.

Growth of tropical savanna grass plants in competition: A shoot population model

The Venezuelan savannas, and in general Neotropical savannas, are composed of herbaceous co-dominant species and less abundant trees and shrubs, conditioned in great measure by the occurrence of annual fire events. We studied the growth dynamics of three grass species representative of the major phenological and architectural types: a precocious, bunch grass, Elyonurus adustus, an early, medium tall grass Leptocoryphium lanatum and a late, tall species Andropogon semiberbis. The experimental design included individuals of all these species growing alone, interacting in species pairs and all three species in competitive interaction. Close inspection of the data showed that the species differ widely in the spatial and temporal patterns of occupation of aboveground space, showing important levels of neighborhood interference among them. Shoot emergence during the time period between fire events (usually 1 year) is not a continuous process but occurs as a set of discrete cohorts. We model plant growth as a population of shoots governed by ordinary differential equations that accounts for the existence of different number of cohorts as a consequence of shoot competition. A comparison of simulated patterns to those observed in the field was assessed by the root mean square (RMS) error between the transient behaviors of both patterns. L. lanatum resulted both the most impaired and the least impairing of the three species and the opposite is valid for A. semiberbis. For the former species, the competition effect when growing together with the other two is stronger that when growing in pairs and close to an additive process. For E. adustus and A. semiberbis the addition of the third species does not substantially modified the effect obtained when competing in pairs. This model can be applied to the analysis of the herbaceous plant growth process on savannas subject to fire. With modifications, the model can be applied to other grass plants and other grassland ecosystems. We suggest that a possible mechanism involved in this process is the growth inhibition of the basal shoots by the older shoots of the same plant.

CLIMATIC FLUCTUATION CAUSES LARGE-SCALE SYNCHRONOUS VARIATION IN RADIAL ROOT INCREMENTS OF PERENNIAL FORBS

Although there is clear evidence that climate change influences ecological patterns and processes, scientists do not agree on the importance of climate in causing ecological change. Part of the problem is finding large-scale ecological response patterns that are unbiased and unconfounded estimators of the effects of climate change. Here we present evidence that the 1997/1998 El Niño event, associated in 1998 with the highest global surface temperature since 1860, caused synchronous variation in radial increment growth of the main roots of perennial forb species in the United States and in Switzerland. Our a posteriori analysis of annual ring width fluctuations indicates that growth of herbaceous plants responds rapidly and sensitively to climatic fluctuation, while the direction and strength of the response depends on interactions with local conditions. We suggest that analysis of growth rings in the roots of forbs provides a widely applicable approach to detecting effects of both strong global climate variation and regionally limited extreme climatic events on herbaceous vegetation. This new technique of “herb-chronology” thus helps ecologists to evaluate how competitive balance between plant species in herbaceous vegetation might respond to climate change, with consequences for ecosystem function and diversity.

Inter-hemispheric comparison of fire history: The Colorado Front Range, U.S.A., and the Northern Patagonian Andes, Argentina

Fire history was compared between the Colorado Front Range (U.S.A.) and northern Patagonia (Argentina) by dating fire-scars on 525 Pinus ponderosa and 418 Austrocedrus chilensis, respectively, and determining fire weather on the basis of instrumental and tree-ring proxy records of climatic variation. Years of above average moisture availability preceding fire years, rather than drought alone, is conducive to years of widespread fire in the Colorado Front Range and the northern Patagonian study areas. Above-average precipitation promotes fire by enhancing the growth of herbaceous plants which increases the quantity of fine fuels during the fire season a few years later. The short-term variability in moisture availability that is conducive to widespread burning is strongly related to El Nino Southern Oscillation (ENSO) activity. The warm (El Nino) phase of ENSO is associated with greater moisture availability during the spring in both regions which leads to peaks in fire occurrence several years after El Nino events. The warmer and drier springs associated with la Nina events exacerbate the drying of fuels so that fire years commonly coincide with La Nina events. In both regions, there was a dramatic decline in fire occurrence after the early 1900s due to a decline in intentionally set fires by Native Americans and European settlers, fuel reduction by livestock grazing, and increasingly effective organized fire suppression activities after the 1920s. In both regions there was a marked increase in fire frequency during the mid-and late-19th centuries which coincides with increased ignitions by Native Americans and/or European settlers. However, year-to-year variability in ring widths of Pinus ponderosa and Austrocedrus chilensis also increased from relatively low values in the late 1700s and early 1800s to peaks in the 1850s and 1860s. This implies frequent alternation of years of above and below average moisture availability during the mid-19th century when the frequencies of major fire years rise. The high correlation of tree-growth variability betweem the two regions implies a strong inter-hemispheric variation in climatic variability at a centennial time scale which closely parallels a variety of proxy records of ENSO activity. Based on the relationship of fire and ENSO events documented in the current study, this long-term trend in ENSO activity probably contributed to the mid- and late-19th century increase in fire spread in both regions. These similar trends in fire occurrence have contributed to similar patterns of forest structures, forest health, and current hazard of catastrophic wildfire in the Colorado Front Range and northern Patagonia.

How Experimental Defoliation and Leaf Height Affect Growth and Reproduction in Trillium grandiflorum

ROONEY, THOMAS P. AND DONALD M. WALLER (Department of Botany, University of Wisconsin-Madison, 430 Lincoln Drive, Madison WI 53706). How experimental defoliation and leaf height affect growth and reproduction in Trillium grandiflorum. J. Torrey Bot. Soc. 128: 393-399. 2001.-Both defoliation and higher leaf placement can reduce growth in herbaceous plants. We examined variation in relative growth rate (RGR) and reproduction in response to defoliation and leaf height in Trillium grandiflorum at 4 sites in northern Wisconsin, USA. Plant biomass and the probability of flowering increased with increased leaf height. Analyses of covariance revealed that experimental defoliation and leaf height separately and independently reduced individual RGR, and accounted for about 42% of the total variance in RGR. Defoliation in 1998 had no effect on flowering in 1999, but leaf height in 1998 was positively associated with the likelihood of flowering in 1999. RGR and plant responses to defoliation varied among sites. We conclude that defoliation and leaf height reduce RGR over short time scales.

Linear relationships between aboveground biomass and plant cover in low open herbaceous vegetation

Abstract. Four herbaceous plant species of a sand dune area and several herb species of an open early‐successional patch were investigated for the occurrence of a simple relationship between aboveground biomass and plant cover. Without exception linear regressions of aboveground biomass on plant cover were found with slope factors depending on the growth form of the species. These results suggest that (early) growth of herbaceous plants in low and (temporarily) open vegetation is not affected by possible constraints caused by a decreasing ratio of plant cover to aboveground biomass. The obtained linear relationships could be used for rapid non‐destructive determination of aboveground biomass by image‐analysis of cover data.

‘Effective growing days’: a simple predictive model of the response of herbaceous plant growth in a Mediterranean ecosystem to variation in rainfall and phosphorus availability

1 Herbaceous plant production on many Mediterranean soils is severely restricted by nutrient deficiency. On such a shallow, phosphorus‐deficient soil in the western Galilee of Israel with an average annual rainfall >800 mm, a single addition of phosphorus fertilizer consistently increased herbaceous plant production in a community dominated by the dwarf shrub Sarcopoterium spinosum by a factor of 2.8–3.8 over 7 years. Regardless of phosphorus addition, interannual variation of the herbaceous vegetation remained high (C.V. = 0.33). A simple model based on climate data was developed to explain the continuing interannual variation in biomass production. 2 This interannual variation is accounted for by an ‘effective growing day’ index, G, based on an estimate of the number of days throughout the growing season during which the available water in the rooting zone can balance the current potential evaporation demand. The validity of this approach was tested on data from 7 consecutive years. 3 At given phosphate (P) availability levels, the index G was found to be highly correlated with both seasonal biomass production and P uptake of the herbaceous plant, but the regression lines intersected the G axis far to the right of the origin. 4 When the adverse effect of the winter climate on growing conditions was taken into account, the regression lines passed close to the origin. Annual biomass production and P uptake could then be well described as linear functions of G with the slope related to availability of P. 5 Average intraseasonal trends gave G‐values which were better predictors of both biomass production and P‐uptake than annual weather (temperature or potential evaporation) fluctuations. 6 Both shoot biomass and P uptake were strongly influenced by growing conditions in autumn (beginning of growing season) and in spring (main growing season), but plant production was more sensitive than P uptake to growing conditions in autumn and vice versa in spring. 7 The close relationship between G and P uptake at different P availability levels indicates that availability of P did not diminish for at least 7 years after a single application of 4.5–9.0 g m−2 P as superphosphate. Nutrient cycling, secondary effects of the dominant legume species, and small losses of P from the ecosystem are proposed as possible reasons for this phenomenon.

Relationships between soil moisture and growth of herbaceous plants in a natural vegetation mosaic in Niger

The ‘tiger bush’ is a particular vegetation pattern in which densely vegetated bands alternate with bare areas. In general, bare areas are working as impluvium for the downslope vegetated stripes. The intraseasonal regimes of soil moisture are quantified during a rainy season, and their influence on the growth of the annual vegetation is analysed.Data were collected along the line of maximum slope crossing two vegetated bands. Density and phenology of herbaceous layer are related to the changes of soil moisture and to the associated soil surface features.The herbaceous layer comprises only annual species, mainly composed of the tiny grassMicrochloa indicaandCyanotis lanata(Commelinaceae). Both are indicators of long-term overgrazing. The distribution ofMicrochloa indicais well correlated with the sedimentary crusts located immediately upslope of the thicket.Cyanotis lanatais the only species recorded in the downslope part of the transect. Its distribution is well correlated with the biological crusts located in the core of the thicket, where infiltration first occurs and high infiltration rates are seen, as long as shade and litter are not limiting for seedling development. As the rainy season progresses, infiltration also increases upslope of the thicket which, until then, remains bare and where onlyMicrochloa indicagerminates provided the seed stock is not limiting.

Nitrogen and Biomass Dynamics following Brush Control in the Cross Timbers

Converting marginal hardwood forest to grassland has the potential of increasing economic output with livestock grazing. Nitrogen (N) management during conversion needs to be evaluated to minimize possible adverse effects on the environment. This study was conducted to determine temporal changes in quantities of N and biomass within ecosystem compartments after herbicide application in a mature post oak (Quercus stellata Wangenh.)-blackjack oak (Quercus marilandica Muenchh.) forest. The 4 treatments evaluated included; 1) no brush kill with no grass overseeding, 2) brush kill with no grass overseeding, 3) brush kill with cool-season grass overseeding, 'K-31' tall fescue (Festuca arundinacea Schreb.), and 4) brush kill with warm-season grass overseeding, 'Plains' Old World bluestem [Bothriochloa ischaemum var. ischaemum (L.) Keng.]. Excellent brush kill was accomplished with 2.2 kg a.i. ha(-l) tebuthiuron (N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2 yl]-N,N'-dimethylurea) applied in spring 1993. Total N was measured during a 21-month period (June 1993 to February 1995), in 15- X 25-m plots, within 8 compartments; soil (0 to 60 cm), roots (0 to 60 cm), litter, top growth of herbaceous plants, woody plants 2.5 cm in diameter. Stored N in tall fescue forage was 6 to 7 times greater than in Old World bluestem or native vegetation by June 1994 and was 2 times greater in October 1994 and February 1995. Above-ground biomass of tall fescue and Old World bluestem was not different in October 1994 or February 1995, but both were greater than native vegetation. Litter biomass and total N in litter decreased, especially in the tall fescue overseeding treatment. Total N in the soil for all treatments averaged 5,100 kg ha(-1) and fluctuations were not detectable among treatments. Total N changes in other compartments were not observable or were minimal. Brush kill and overseeding with grass had little influence on total N stored within the ecosystem for 21 months after treatment. N was redistributed to the herbaceous biomass compartment and away from the litter compartment after herbicide application, regardless of the overseeding treatment applied.

Soil phosphorus in a managed Mediterranean woodland ecosystem: herbage response and cattle grazing effects

A study of soil-plant relations in scrub woodlands on terra rossa soil in Israel, examined the following hypotheses: (a) that herbaceous plant growth on terra rossa is limited by phosphorus deficiency; (b) that shrub control and tree thinning can release available P for use by herbaceous vegetation; (c) that cattle fed P-rich poultry litter as a nitrogen supplement, can increase the available P level in the soil by recycling excess P through their excrements. Soil available P (bicarbonate-soluble) content was 4–9 mg kg −1 soil in the surface 15 cm soil layer and 2–3 mg kg −1 soil in the deeper 15–30 cm layer. A bioassay showed that plant growth was restricted when P concentration was less than 11 mg P per kg soil. Addition of nitrogen did not increase herbaceous yield, Neither thinning of trees nor shrub control using herbicide had any significant effects on available soil P. There was a significant increase in available soil P concentration in the surface 3 cm layer of soils on sites that had been partially cleared and grazed for 3 years by cattle supplemented with poultry litter. Only near centers of cattle activity was there a significant increase of P in the 3–15 cm layer, and only there was the enrichment sufficient to remove phosphorus limitation to herbage growth.

THE EFFECTS OF FILM-FORMING ANTITRANSPIRANTS ON LEAF WATER RELATIONS OF BEDDING PLANTS

The effectiveness of antitranspirant type and concentration on the leaf water relations of Saliva splendens F. `Firebird and Petunia × hybrida Juss. `Comanche'. Two film-forming antitranspirants, Cloud Cover and Folicote, were tested at three different concentrations in two different environments. The leaf water potential, stomatal conductance, and relative water content were evaluated. Transpiration per unit vapor pressure deficit and stomatal conductance for both crops decrease slightly but there was no trend with respect to the film type, environment or concentration rate. The leaf water potentials and relative water content did not show significant difference after antitranspirant application. In order for antitranspirant application to be of benefit to the growth of herbaceous plants, a more durable coating that remains semipermeable would have to be utilized.

Reforestation of Orchard Stands and Savannahs on Pennsylvania's Allegheny Plateau

Abstract Orchard stands and savannahs are forest openings that failed to regenerate after turn-of-the-century logging and have been dominated by dense herbaceous plant growth for 50 or more years. The effectiveness of herbicide application, mechanical site preparation, and fertilization on survival and growth of five species of seedlings was tested over a 6-year period. Neither site preparation nor fertilization significantly increased survival of any species above the control during the first 2 years after planting. Residues of picloram, one of the herbicides used during site preparation, reduced survival of all species, except white ash, below that of the control. Fertilization reduced survival of all species. Black cherry was the only species that grew better as a result of the treatments. Weed removal significantly increased black cherry seedling growth, but much of this increased growth was in branches, rather than the terminal shoot. Mechanical site preparation plus herbicide did not increase growth of black cherry seedlings above that of herbicide alone during the first 2 years and had the disadvantage of stimulating reinvasion by grass. Deer which penetrated the protective fence interfered with evaluation of growth after the second year. North J. Appl. For. 2:22-26, Mar. 1985.

Preliminary observations on the effect of removal of black bluebush (Maireana pyramidata) and Pearl Bluebush (M. sedifolia) on shrub regeneration, herbage production and erosion potential.

The effects of mechanical removal of shrub tops and grazing on two bluebush communities, one with Maireana pyramidata (black bluebush)and the other with M. pyramidata and M. sedifolia (pearl bluebush) as co-dominants, were examined on the western edge of the Riverine Plain in New South Wales Measurements were made on shrub regeneration, the relationship of shrub units to a critical value for an erosion index, the change in soil surface levels, and the growth of herbaceous plants over time Shrub regeneration was slower under grazed than ungrazed conditions and occurred mainly from basal shoots of established plants rather than from seedling establishment. Herbage yields Increased on the mounds previously occupied by shrubs, whereas production between shrubs was not affected by shrub removal. After four years there was sufficient shrub growth to prevent wind erosion, except on the cleared and grazed plot at the M. sedifolia site.

Seasonality in New Zealand Plants

Summary Leaf and shoot flush, leaf-fall and cambial gro~vth in ~voody plants, seasonal begetative growth in herbaceous plants, flowering, fruiting, and periodicity are discussed. Although information is somewhat fragmentary, it appears that it? the lowlands most aspects of seasonal behaviour are less well defined and morc protracted than in regions 1%-ith strongly seasonal climates. .It high altitudes, short growing seasons impose a more rigid phenological cycle on most species.

Allelopathic Mechanisms of Arctostaphylos glandulosa var. zacaensis

Arctostaphylos glandulosa var. zacaensis is a strong dominant of chaparral vegetation on Zaca Ridge in the San Rafael Mountains, California. It occurs in pure stands, sometimes openly spaced with the canopies covering 50 to 75% of the soil surface, or it may form completely closed cover. A barren soil surface, without seed- lings of any species in spite of sufficient light and soil moisture, char- acterizes the stands. Fire or artificial removal of shrubs results in growth of herbs and shrub seedlings until shrub dominance is again established. Detrimental biochemical interference (allelopathy) between Arcto- staphylos and associated plants is involved in this phenomenon. Aqueous leachate from Arctostaphylos foliar branches and from leaf litter is toxic to the growth of annual grasses. The allelopathic constituents leachable from Arctostaphylos plant organs have been identified as arbutin, hydro- quinone, and gallic, protocatechuic, tannic, vanillic, chlorogenic and p-hydroxybenzoic acids. Toxins such as p-hydroxybenzoic, p-coumaric, ferulic, syringic and o-coumaric acids are found in the soils beneath Arctostaphylos shrubs. These toxins can inhibit the germination and suppress the radicle growth of herbaceous plants at concentrations below 400 ppm; e.g., hydroquinone significantly inhibits radicle growth of Avena fatua and Bromus rigidus at a concentration of 50 ppm. Chem- ical constituents present in leaf litter appear to be more leachable after subjection to temperatures up to 160 C-resulting in increases of toxic- ity to herb growth-but are denatured at temperatures above 180 C, with complete loss of toxicity at temperatures above 200 C. Allelopathy

Gibberellin modifications of photoperiod controlled growth in herbaceous plants

Gibberellin modifications of photoperiod controlled growth in herbaceous plants

Studies of Localized Stages of Growth in Some Common New England Plants

IN the following are given some of the stages in detail found in a few of our common plants, and some general notes which may be safely drawn, and which may be useful in studying plants from this point of view. The cases given are not chosen as particularly striking ones, but are such as would come naturally under the notice of any one. In a following paper the writer hopes to present more striking examples from some of the less generally known plants now in the Botanic Gardens of Harvard University. The few given, however, will show the truth of the principle involved as well as more striking ones. In a paper by Robert T. Jackson, ' Localized Stages in Development of Plants and Animals, ilcizoirs Boston Sociely of Nlatural Histori, Vol. V, No. 4, I899, this principle was worked out and applied to plants. It was there applied to shoots and various growths of trees almost exclusively. It is in the spirit of that paper that I have attempted this one, giving the results of my study of plants from this point of view. My thanks are due to Dr. Jackson for reading this in manuscript and for many suggestions. The new point intended to be brought out here is the application of the principle of localized stages to the early spring growth of herbaceous plants. These are adult plants, not young plants or seedlings. The principle is also applied to the stages immediately preceding the floxver. The principle of localized stages in development, to quote from the above paper, is that, throughout the life of the 865