Herbaceous species

Land use changes in the tropics have resulted in a landscape characterized as a mosaic of logged forests, cleared fields, and successional forests. This results in the transformation from extremely fire resistant rainforest ecosystems to anthropogenic landscapes in which fire is a common event (16, 17), Fires occur in disturbed tropical forests because deforestation has a dramatic effect on microclimate. Deforestation results in lower relative humidities, increased wind speeds, and increased air temperatures. In addition, deforestation results in increased quantities of biomass that are susceptible to fire. This biomass may be in the form of forest slash, leaf litter, grasses, lianas or herbaceous species (16, 18). 

Crick, J.C. Grime, J.P. (1987). Morphological plasticity and mineral nutrient capture in two herbaceous species of contrasted ecology. New Phytologist, 107, 403-14. 

Turner, N.C., Schulze, B.-D. Gollan, T. (1985). The response of stomata and leaf gas exchange to vapour pressure deficits and soil water content. II. In the mesophytic herbaceous species Helianthus annuus. Oecologia, 65, 348-55. 

Phytovolatilization Soils, sediments, sludges, groundwater Chlorinated solvents, MTBE, some inorganics (Se, Hg, As) Herbaceous species Trees Wetland species... 

Gasification coupled with water-gas shift is the most widely practiced process route for biomass to hydrogen. Thermal, steam, and partial oxidation gasification technologies are under development. Feedstocks include both dedicated crops and agricultural and forest product residues of hardwood, softwood, and herbaceous species. 

The Seasonal Tropical Forest and Woody Savanna ecosystems are common in tropical regions with a short dry period. The characteristic features of soils from these ecosystems are the neutral reaction of soil solution and periodic leaching during wet season. The herbaceous species favor the formation of both sward and humus horizons. 

It is widely believed that vegetation growing in the humid eastern United States would be severely injured if oxidant concentrations reached the daily peak concentrations (0.20-0.40 ppm) commonly experienced in the less humid sections of California. An air pollution episode that occurred on July 27-30, 1970, in the Washington, D.C., area is indicative of what may happen. During this 4-day period, the peak oxidant concentrations ranged from 0.14 to 0.22 ppm and were accompanied by a low concentration of sulfur dioxide (0.04 ppm). Oxidant injury was observed on 31 tree, 15 shrub, and 18 herbaceous species in an area of 72 mi (about 187 km ). Increased emisskm of the precursors of photochemical-oxidant formation could result in repeated episodes of acute injury or even chronic injury to eastern vegetation. 

The test seeds used for the bioassays were Mimosa pudica, Achyranthes aspera, Bidens pilosa, and Crusea calocephala (herbaceous species) Ochroma lagopus and Heliocarpus donell-smithil (arboreal species). 

Ferns were the more Inhibitory of the 2 herbaceous species. 

One of the hypotheses regarding evolutionary aspects of flavonoid diversification concerns the concept of flavonol accumulation in basal Angiosperms versus flavone accumulation in advanced families. Recently, some further efforts have been made towards defining the flavone/flavonols ratio in Dicotyledonae and their relation to lignification, indicating an increased tendency towards flavonol accumulation in lignified plants, whereas herbaceous species tend to accumulate more of the flavones. From the presented entries, it appears that flavone derivatives are more abundant in Lamiaceae than flavonols. In the Asteraceae, however, more data concern the flavonols. Both families are more or less herbaceous and members of the more advanced Angiosperms. 

If Asteraceae, which are primarily herbaceous, are examined on a per-sample basis, the 192 samples that actually have been collected, are well below the predicted number of 472. Thus, while close to the predicted number of genera of Asteraceae have been sampled, the majority of species have been sampled only a single time as whole plants and the family is underrepresented on a per-sample basis. Figure 3.2 presents actual values for representative plant families with a line for predicted values. Again, most families beneath the predicted line are composed mostly of herbaceous species, but on a per sample basis, it becomes more apparent how underrepresented families like Asteraceae, Poaceae, and Orchidaceae actually are. Likewise, both Figures 3.1 and 3.2 clearly demonstrate that those families consisting mainly of woody species that are major structural elements of forests have been collected at a rate greater than would be predicted by chance. 

In addition to the variations in the LHC composition that occur from species to species, each species has its extractives, which include resins and waxes. These constituents are capable of interfering with cellulose hydrolysis because of their hydrophobic nature. Tannins and other highly reactive materials are constituents of some woody species. When LHC is obtained from nonwoody (herbaceous) species, the range of interfering constituents increases greatly. Sugars, starches, dextran, carotenoids, and many isoprenoids are to be found. Operators of a cellulose hydrolysis process that uses municipal solid waste as its biomass resource may experience seasonal variations in composition and chance inclusion of crankcase oil and other products that inhibit enzymes or kill yeast. 

Modifications have been made to the original protocol in order to apply this method to herbaceous species. Iiyama and Wallis (1990) added 100 pL perchloric acid (HC104) to improve the dissolution of wall material. This decreased the overall time required for the procedure and made the use of hydroxylamine unnecessary. 

Hydraulic conductivities (l/p ) also can be used for the phloem e.g., the phloem hydraulic conductivity can be about 1 x 10-4 m2 s-1 MPa-1 for herbaceous species and 4 x 10-3 m2 s 1 MPa-1 for trees pressure gradients along the phloem are generally much higher in small herbaceous species than in tall trees. 

Table 13 Site preference of terrestrial herbaceous species in the floodplains of the Central Amazon, per number of species and percentage of occurrence.

TABLE 4.11 Average Annual Yields of Most Productive Herbaceous Species in Field Trials in U.S. Southeast and Midwest/Lake States ... 

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