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  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant, cell & environment 15 (1992), S. 0 
    ISSN: 1365-3040
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: To help ascertain the maximal productivity of plants with Crassulacean acid metabolism, measurements were undertaken on four potentially highly productive CAM species at optimal leaf or stem area indices of 4 to 6. Shoot area and shoot biomass were based on regression equations for material harvested from adjacent plants at 3-month intervals; in addition, the monitored platyopuntias were harvested to determine their dry weight at the end of the observation period. Agave mapisaga and A. salmiana near Mexico City had a productivity averaging 40Mg ha−1 year−1 and exhibited higher maximal rates of net CO2 uptake than previously reported for CAM plants (29–34 μmol m −2 s−1). When irrigated and fertilized daily, Opuntia amyclea and O. ficus-indica in Saltillo, Coahuila, Mexico, had an average productivity of 46Mg ha−1 year−1. These are among the highest productivities ever reported for any plant species.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1573-5052
    Keywords: Canonical ordination ; Community dynamics ; Floristic fluctuations ; North American grassland ; Species composition ; Succession ; Weather
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Compositional patterns of vegetation and their relationship to temporal and spatial environmental variation, with emphasis on climatic factors, were investigated in plant communities located in the southernmost portion of the North American Graminetum, in central México. Data from 353 samples, obtained in four ecologically contrasting plant communities during 11 years, were analyzed by partial canonical correspondence analysis. Eight climatic variables and eighteen covariables (seventeen edaphic and one resource management) were included in the ordination. A relationship between floristic change and weather variation, once covariables effects were fitted, was examined. Despite a strong contrast in ecological conditions among study sites, a set of four climatic variables was finally found in which each variable contributed independently and statistically (P 〈 0.01) to the total variance in the vegetation data. Thus, environmental variables other than climatic could not conceal the important role of weather as a mediator of floristic change through time. Summer precipitation and summer maximum temperature showed the highest correlations with the first two species axes, 0.77 and –0.39, respectively. Contribution of these two climatic variables to variance in the vegetation data explained by environmental variables was approximately 81%. Annual species were abundant during rainy years, while abundance of perennial grasses and shrubs showed no clear relationship to weather variation. This study explicitly probes the important role of rain patterns in shaping structure and composition of semiarid communities and considers how other environmental factors can affect plant communities at the southernmost part of the North American Graminetum.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1573-5036
    Keywords: biomass ; decomposition ; Distichlis spicata ; Echinochloa polystachya ; Eulalia trispicata ; Lophopogon intermedius ; Pennisetum mezianum ; primary production ; primary productivity ; Themeda triandra
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Studies of net primary production in four contrasting tropical grasslands show that when full account is taken of losses of plant organs above- and below-ground these ecosystems are far more productive than earlier suggested. Previous values have mainly been provided by the International Biological Programme (IBP), where estimates of production were based on a change in vegetation mass alone and would not necessarily have taken full account of organ losses and turnover. Calculation at three of our sites based on estblished methodology using changes in plant mass alone (i.e. that used by the International Biological Programme, IBP) proved to be serious underestimates of when acount was taken of losses simultaneously with measurement of change in plant mass. Accounting for the turnover of material at these three sites resulted in productivities up to five times higher than were obtained using the standard IBP procedure. An emergent C4 grass stand at a fourth site in the Amazon achieved a productivity which approached the maximum recorded for agricultural crops. In this case, productivity values, when organ losses were taken into account, only slightly exceeded that obtained with IBP methods. The findings reported here have wider implications, in prediction of global carbon cycling, remote sensing of plant productivity and impact assessment of conversion to arable cropping systems.
    Type of Medium: Electronic Resource
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