No abstract

Paratya curvirostris (Heller, 1862) (Decapoda: Atyidae) is the first member of its family found to be protandrous.Reappraisal of published information on Atya bisulcata, Atya serrata and Caridina richtersi indicates that they are also protandrous.The occurrence and biology of protandry in the Decapoda is reviewed. Analysis of available data suggests that protandry has no adaptive value and its frequency in these Crus:tacea is a result of the ease with which decapod reproductive physiology can be modified to produce the phenomenon.

Effects of annual additions of mineral N and P (100 kg ha -1) on plant species composition and annual aboveground net primary production (ANPP) were investigated during the first three years following disturbance in a semi-arid ecosystem. Additions of N reduced richness of perennial plant species during years 2 and 3, while P reduced the number of perennial species only in year 3. From year 1 to year 2, annual and biennial species richness declined in all treatments while ANPP of annual species increased greatly. Added N increased ANPP of annual species while it decreased ANPP of most perennial species relative to the unfertilized control treatment. Community similarities were higher for the control and native vegetation than for other pairs of treatments using both species presence and plant production data. Nitrogen additions have retarded but not completely arrested secondary succession in this system.

SU MMARYEffects of inoculation of Hedysarum boreale ssp. boreale Nutt. (Fabaceae) witb mycorrbizal fungi (topsoil inoculum) and Rhizobiiiyn (pure inoculum) were studied in tbe field in soutbwestern Wyoming, USA. After 3 years, plants receiving botb itiocula bad greater total aboveground biomass atid leaflet biomass, more leaves, bigber aboveground nitrogen and pbospbotus contents and greater survival tban plants wbicb received single or no inoculum. Soil 20-40 cm deep (wbere roots were concentrated) beneatb Hedysarum individuals from all treatments had a lower concentration of total nitrogen tban did soil between plants. Hedysarum plants, inoculated or not, apparently extracted sufficient nitrogen from tbe soil, as tbey bad similar leaflet nitrogen concentrations. Hedysarum decreased tbe size of tbe pool of soil nitrogen even witb Rhizobium inoculation on disturbed land in a semi-arid environmet-it during tbe first 3 years of growtb.