Angiosperm classification and phylogeny: a rectifying comment

A commentary is given on the criticism of Dahlgren's recent classification of angiosperms by Corner ( Botanical Journal of the Linnean Society, 82: 81–87 (1981)). In his dissatisfaction with the current, (almost) generally accepted nomenclatural concepts he has chosen to use my classification as a target. It is agreed that nomenclature is not 'fair' to plant groups playing the most important role in building up the biosphere, and that nomenclatural constructions do not reflect the consideration given to various parts of the plant. Corner does not seem to be familiar with the fact that his so-called 'pseudons' are common to all current systems of classification, nor that the termination '-florae' has been used by Thorne (1968) and in a number of publications since. This suffix does not imply that the botanists using it neglect vegetative characters, nor characters from fruits and seeds. Other misunderstandings are also pointed out. In no case has it been satisfactorily demonstrated by Corner that my orders or superorders are unnatural entities (even though a number of them most likely are).     

A phylogenetic analysis of the land plants

Phylogenetic systematics (cladistics) is a theory of phylogeny reconstruction and classification widely used in zoology. Taxa are grouped hierarchically by the sharing of derived (advanced) characters. The information is expressed in a cladogram, a best estimate of a phylogeny. Plant systematists generally use a phenetic system, grouping taxa on overall similarity which results in many groups being formed, at least in part, on the basis of shared primitive characters.
The methods of phylogenetic systematics are used to create a preliminary cladogram of land plants. The current classification of land plants is criticized for its inclusion of many groups which are not monophyletic.
Objections to the use of phylogenetic systematics in botany, apparent convergences within major groups and frequent hybridization, are shown to be invalid. It is concluded that cladistic analysis presents the best estimate of die natural hierarchy of organisms, and should be adopted by plant systematists in their assessment of plant interrelationships.     

Soybean leaf photosynthesis in relation to maturity classification and stage of growth

Leaf photosynthetic rates were measured on field-grown soybeans during the 1980 season. Comparisons were made between different cultivars and isolines representative of maturity groups I–IV. Mature, fully expanded leaves at different nodes on the plant were measured in high light to determine which had the highest potential photosynthetic rates at any one time. Successive leaves during the growing season had maximum rates which increased from about 22 mol CO₂ m^-2 s^-1 on 25 June to a peak of 30–44 mol CO₂ m^-2 s^-1 in early August.The persistency and eventual decline in the maximum rate was associated with the maturity group and related dates of flowering, pod fill and onset of senescence. Early maturing cultivars (groups I and II) had higher peak rates (38–44 mol CO₂ m^-2 s^-1) than later maturing cultivars (30–35 mol CO₂ m^-2 s^-1, groups III and IV). However, the photosynthetic rates of early maturing cultivars declined rapidly after attaining their peak, whereas the leaves of later maturing cultivars maintained their photosynthetic activity for much longer.     

The influence of thick floating vegetation (Water hyacinth: Eichhornia crassipes) on the physico — chemical environment of a fresh water wetland

Measurements made in fresh water wetland have shown that temperature, pH, dissolved oxygen and bicarbonate alkalinity in the hyacinth infested area were lower, but dissolved free carbon dioxide concentration was excitingly greater than in the open water area. This extreme hypoxic and hypercarbic condition of hyacinth covered areas was caused by the thick coverage of Eichhornia crassipes which was crucial for the composition of the characteristic flora and fauna.     

Farm pond restoration using Chara vulgaris vegetation

Four aged Madison County, New York farm ponds were selected to see if various treatments could be used to restore the water quality. One pond was untreated and used as a control; another pond was partially drained and exposed to the drying and oxidizing effects of the air over the fall and winter; the other two ponds were drained and the accumulated sediment removed by bulldozing. In these latter two ponds, Chara vulgaris vegetation was inoculated following the restoration process. C. vulgaris growth rapidly became the dominant producer where this inoculation was accomplished in the fall of 1976, and it is expected that the other pond will also become a C. vulgaris pond in 1978 — after its oogonia have undergone the requisite winter dormancy period.Early C. vulgaris growth was found to be associated with clear water conditions and lessened phytoplankton growth; short, bushy, light-inhibited growth by the algae stabilized the bottom against wind-caused turbidity because of its rhizoidal growth within the substrate. Pioneer C. vulgaris growth was also found to be highly productive, significantly lowering the pond's CO₂ readings.Investigators of aquatic systems are cautioned to be cognizant of the effect of epiphytic growth on successional events in such environments. Such epiphytes are surely important, if not prime, causes of the demise of various aquatic macrophytes.The partial draining and exposing of a pond over the fall and winter did not yield significantly improved water conditions.     

Global classification of natural terrestrial ecosystems

Summary A global classification system of natural terrestrial ecosystems (including systematic notation), based on the climate zones of Walter, is presented. The basic units of the system are the ecological units biome and biogeocoene. The zonobiomes, which are climate zones corresponding to the largest vegetation units, are subdivided into subzonobiomes and these into individual biomes. The biomes are thus natural, geographical units within the climate zones. They are in turn subdivided into individual biogeocoenes and their constituent synusiae. In addition, the coordinate concepts of pedobiome and orobiome are introduced. These are distinguished from the zonobiomes as follows:1. the pedobiomes by extreme edaphic conditions which cause azonal vegetation.2. the orobiomes, as mountain ranges, by their vertical climate zonation and the altitudinal belts of vegetation.These relationships are explained, and two subseries of pedo-and oro-subunits are established. Transitional zones (zono-ecotones) between individual zonobiomes are also distinguished. The classification system is summarized in a schematic, and a world map of zonobiomes and zono-ecotones is included. More details are presented in Walter (1976).

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Zusammenfassung Ein globales Gliederungssystem der natürlichen terrestrischen Ökosysteme (einschließlich systematischen Bezeichnungen) wird in Beziehung zu den Walter'schen Klimazonen gesetzt. Grundeinheiten des Systems sind die ökologischen Einheiten Biom und Biogeozön. Die Zonobiome werden unterteilt in Subzonobiome und diese in Biome. Die Zonobiome sind Klimazonen und entsprechen den größten Vegetationseinheiten. Die Biome sind natürliche, geographische Einheiten innerhalb der Klimazonen. Sie werden bis zu einzelnen Biogeozönen und ihren Synusien (Teilsytemen) unterteilt. Parallel dazu werden die Begriffe Pedobiom und Orobiom eingeführt. Diese heben sich aus den Zonobiomen heraus: die Pedobiomen durch extreme Böden, die eine azonale Vegetation bedingen, die Orobiome als Gebirge durch die vertikale Klimagliederung und die Höhenstufen der Vegetation. Diese Beziehungen werden erklärt, und zwei Nebenreihen der Pedo- bzw. Orobiom-Untereinheiten werden aufgestellt. Zwischen den einzelnen Zonobiomen werden Übergangszonen (Zonoökotone) unterschieden. Das Gliederungssytem wird bereits in einem Schema zusammengefaßt, und eine Weltkarte der Zonobiome und Zonoökotone wird beigefügt. Ausführlich werden alle diese Fragen bei WALTER (1976) behandelt.

     

A phytosociological study of weed communities on the southwestern Coastal Plain of North Carolina

Summary The vegetation of cultivated, fallow and ‘old’ fields of Scotland County, N.C. was both randomly and subjectively sampled throughout the growing season of 1973. Relevés were placed in each of the above management units, and the data collected in this relevé analysis were sorted into phytosociological charts, with the aid of the digital computer. Weed associations delimited in the charts reflected the importance of edaphic factors, time (aspect), and man's agricultural activities as causal factors in the determination of characteristic assemblages of weeds. Several character and differential species were denoted, in a tentative classification of the weed associations. The cultivated and fallow stands in the spring aspect were noted to be dominated by a group of spring annuals. Summer annuals were more prevalent in homologous situations in the summer. It was determined that perennials, appearing mainly as seedlings in cultivated and fallow fields, attained dominance in ‘old’ fields, one to five years in age. Within each of the major spheres of management, and in each season, associations of weeds mainly reflected differences in edaphic factors. Many character species were noted to maintain affinities to an assortment of soil types that ranged from moist loams to xeric, sterile sands. A study of roadsides, hedgerows, field margins and other ecotonal areas inhabited by weeds was carried throughout the growing season of 1973, also. Species presence was documented in each of these habitat types and reported in Sharp (1974). The weed flora of Scotland County was found to be rich in species. A total of 506 species representing 248 genera and 80 families were encountered throughout the study. Of the total number of species listed, approximately 25 percent were of foreign origin, and 28 percent represented additions to the flora of Scotland County. This paper is the short version of a masters thesis for the Department of Botany, University of North Carolina at Chapel Hill. The author would like to extend his appreciation and gratitude to Professors H. Lieth, A. E. Radford and J. Hardin for their generous advice and encouragement extended through the duration of the study.     

Regulating Ecosystem Services of forests in ten Italian Metropolitan Cities: Air quality improvement by PM10 and O3 removal

Urban and periurban forests, which are integrated within the concept of Green Infrastructure, provide important Ecosystem Services, including air purification. In this study, we quantified the Ecosystem Service of particulate matter (PM₁₀) and Ozone (O₃) removal from urban and periurban forests in ten metropolitan cities in Italy, and its total monetary value. In order to gain a better understanding of how Ecosystem Services can be regulated on a wider scale, the vegetation ecosystem types were grouped into Physiognomic-Structural Categories of Vegetation according to morphofunctional criteria. The pollution removal was mapped using a remote sensing and GIS approach, by applying a deposition model and a stomatal flux model. We estimated, for the ten metropolitan cities, an overall pollution abatement of 7150 Mg of PM₁₀ and 30,014 Mg of O₃ in the year 2003, which was an extremely hot year. Our findings indicate that structural characteristics (i.e. Leaf Area Index) and functional diversity, linked to stomatal conductance, exert a marked influence on the provision of the regulating Ecosystem Services, whose total monetary value was estimated to be equal to 47 and 297 million USD for PM₁₀ and O₃ removal, respectively. This study represent the first national-scale assessment of the Ecosystem Services of air pollution removal in Europe, thus providing information that may be useful to stakeholders to manage Green Infrastructure more efficiently.     

Modeling grassland aboveground biomass using a pure vegetation index

Remote sensing can be the most effective means of scaling up grassland aboveground biomass (AGB) from the sample scale to the regional scale. Among the remote-sensing approaches, statistical models based on the vegetation index (VI) are frequently used to retrieve grassland AGB because of their simplicity and reliability. However, these types of models have never been comprehensively optimized to overcome VI insensitivity and soil effects. Because grassland AGB is related to grassland type, in our research the integrated orderly classification system for grassland (IOCSG) was used to differentiate grassland types. The study area, located in Inner Mongolia, China, included desert steppe, typical steppe and meadow steppe. A pure VI (PVI) was extracted from the normal VI using spectral mixture analysis (SMA). Using a proportional relationship, PVI models were then constructed based on grassland type. The results demonstrated that the PVI models can have clear advantages over the more commonly used VI models. They simplify the parameterization of VI models and thus enhance models constructed for different regions with different remote sensing data sources. Notably, detailed differentiation of grassland types can improve the accuracy of AGB estimates. The methodology proposed in this study is particularly beneficial for AGB estimates at a national scale, especially for countries such as China with many grassland types.