Soils and Rice-Fields

DOI: 10.1007/0-306-46855-7_8

ABSTRACT Cyanobacteria are an important component of many soils. including the surface crusts that sometimes cover extensive areas
in semiarid regions and mine spoil wastes. They are also abundant in many areas which are wet or submerged for part of the
year. especially rice-fields. Most soils forms have sheaths or mucilage and this polysaccharide has important effects onthe
soil. mostly beneficial. such as improved soil structure. but sometimes adverse where a dense surface layer impedes drainage.
Nitrogen-fixing species often constitute half or more of the species present in soils not enriched with nitrogenous fertilizer
and these can contribute combined nitrogen in several ways to adjacent vascular plants.

Attempts to enhance crop yield by adding cyanobacteria to soils have mostly focussed on paddy rice. Although many studies
have reported positive effects of such ‘algalization’. the number of locations where it has been adopted as routine practice
appear to be few. in contrast to the relatively widespread use of Azolla with rice culture. Algalization is most successful where local species are used to prepare the inoculum. but there is considerable
scope for other improvements. It is important to obtain a much more detailed understanding of cyanobacterial population dynamics
over the whole annual cycle in agricultural systems where rice is grown for only part of the year.

  • [Show abstract] [Hide abstract]
    ABSTRACT: Most of the flooded, open-cast lignite mining lakes of Lusatia (Germany) impacted by the oxidation of iron sulphides (pyrite and marcasite) are extremely acidic. Of 32 lakes regularly studied from 1995 to 1998, 14 have a pH -1). Concentrations of dissolved inorganic carbon (DIC) and phosphorus are typically extremely low. These factors result in a very different environment for algae than found in neutral and acid-rain impacted lakes. The planktonic algal flora is generally dominated by flagellates belonging to genera of Chlorophyta (Chlamydomonas), Heterokontophyta of the class Chrysophyceae (Ochromonas, Chromulina), Cryptophyta (Cyathomonas) and Euglenophyta (Lepocinclis, Euglena mutabilis). Near-spherical non-motile Chlorophyta (Nanochlorum sp.), Heterokontophyta of the class Bacillariophyceae (Eunotia exigua, Nitzschia), Dinophyta (Gymnodinium, Peridinium umbonatum), other Chlorophyta (Scourfieldia cordiformis) and Cryptophyta (Rhodomonas minuta) are also found.
    Hydrobiologia 01/2000; 433(1):123-128. · 2.21 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Since James Hutton established the principle of uniformitarism in 1788, direct comparisons between ancient and present processes have been key elements in geological and paleontological observations. Lyell and Darwin successfully applied uniformitarism using reasoning and inference to obtain the missing data from incomplete evidence (Gould, 1983). This actualistic approach has also permeated the study of stromatolites and their living analogs, modern microbial mats. As early as 1908, Kalkowsky (1908), who coined the term stromatolites, recognized not only the organic nature of stromatolites, but also the participation of microbial life in their construction (Riding, 2008, and references therein), as he wrote: ‘stromatolites have a fine more or less even layered fabric.…and the participation of simple plants gave rise to limestone precipitation’ (translation from Prof. J. Paul, 2008). The structural similarity between algal mats and intertidal stromatolites was documented since the beginning of the twentieth century; Walcott (1914) even presumed the participation of cyanobacteria by then (Awramik and Grey, 2005). The early observations of Black (1933) also included the participation of cyanobacteria in the modern marine microbialites from the Bahamas. The precipitation of calcium carbonate, erosive boring, and binding of sediments were identified as main processes in these algal carbonates (Fritsch, 1945; Pettijohn, 1957; Sharp, 1970). Later Logan et al. (1964) proposed a popular general classification system to group the main morphologies found in ‘algal stromatolites’ when he analyzed recent stromatolites from Shark Bay in Australia.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: In this paper we review the knowledge of the ecology of the largest freshwater ecosystem on Earth: the rice-fields, and in particular the rice-fields from Valencia (Spain) making a special consideration to the cyanobacteria present in this ecosystem. Rice-fields are artificial shallow aquatic ecosystems in which the land management and the agricultural practices together with the rice plant growth govern the major environmental variables affecting the aquatic biota and its relationships. Primary producers are dominated typically by macrophytic algae as Chara and cyanobacteria, both planktonic and benthic (beside the rice plants). Most rice-fields can be considered nutrient replete, since the fertilization inputs and the low ratio volume/surface make that main nutrients are typically available. Under these circumstances other environmental variables as photosynthetically active radiation availability or filtration rates and predation may explain the growth limitation of primary producers. Irradiance availability identify two periods within the cultivation cycle: when plants are short, irradiance is not limiting and some water chemistry variables (as pH, oxygen and dissolved inorganic C concentrations) change drastically as a function of the primary production; when plants are large and the canopy is intense, then irradiance is limiting and the water chemistry changes only slightly along the day. N2-fixation is a main activity in the N cycle in rice-fields, since N2-fixing cyanobacteria represent an important fraction of the aquatic biota of this ecosystem. We will discuss in detail the relevance of this process from the ecological point of view.


Available from
Jan 24, 2015