Dynamics of below-ground plant organs in grasslands

Abstract

The seasonal and year-to-year dynamics of a standing crop of green phytomass, representing both living and dead below-ground organs of herbaceous plants, were studied in Siberia on a series of grasslands that included primary and secondary successional ecosystems on mining spoil, old fields and native meadows. Living below-ground organs were sorted into roots and rhizomes per dominant species. Standing crops of below-ground phytomass fluctuated in meadows from year to year about a steady state value. In successional grasslands, phytomass increased with time; in the course of secondary succession it increased rapidly, and in the course of primary succession it increased slowly. The growth patterns of different plant organs (shoots, rhizomes, roots) of the individual species (Poa pratensis and Elytrigia repens) varied seasonally and from year to year. The dynamics of roots usually coincided with rhizome dynamics and differed from shoot dynamics. The quantitative dominant structure in above- and below-ground layers and its change over the course of succession were evaluated. In undisturbed native grasslands dominants were usually common for both layers, and their percentage values of contribution to shoot and root + rhizome phytomass were equal. In successional grasslands the relative dominant contribution to total above- and below-ground phytomass changed continuously.