Growth and recession of aquatic macrophytes on a shaded section of the River Lambourn, England, from 1971 to 1980

Abstract

Freshwater Biology (1982) 12, 1-15. Growth and recession of aquatic macrophytes on a shaded section of the River Lamhourn, England, from 1971England, from to 1980 SUMMARY. The growth and recession of macrophytes on a shaded section of the R. Lambourn were documented by a mapping procedure. With the exception of Ranunculus spp.. the changes in total cover did not indicate directly the pattern of growth and recession of the macrophyles. Analysis of gross changes, expressed as gains and losses tn cover, indicated that colonization of gravel and silt by the dominant macrophyte, Bertda erecta, did not vary seasonally. Colonization was at a constant rate of about 8% of the site each month throughout the year and this accounted for 50% of the total number of gains by Berula. Gains of Berula from Ranunculus showed an annual cycle with a maximum during the summer when Ranunculus was in recession. Gains of Berula from Callitriche spp. also varied annually but the maximum was during the autumn. Total losses of Berula were at a constant rate throughout the year but were to gravel and silt during the winter, to Ranunculus in spring and early summer and to Callitriche in late summer and autumn. Analysis of loss of Berula with time indicated that the position of the Berula carpet was constantly changing. The growth and recession of Berula could not be linked in a meaningful way to environmental variables. Callitriche and Rammculus both showed an annual pattern of growth and recession. TTiere was temporal separation of the two macrophytes with Ranunculus growing mainly in spring and early summer and Callitriche showing maximum growth in late summer and autumn, and some evidence of spatial separation. The observed differences between years in the growth of Callitriche could not be attributed to any of the environmental variables measured.Discharge was thought to be an important variable controlling the growth of Ranunculus since increase of Ranunculus in the spring was positively correlated with the mean discharge at that time. In years when discharge was low, the growth of Runtoicultis appeared to be restricted by shading from epiphytic algae which accumulated on the plant surfaces under these conditions. Correspondence; A. D. Berrit. Freshwaier Biological Association, River Laboratory, East Stoke. Wareham. Dorset BH206BB, England. (X)46-5070/S2/()2()()-()(X)l $02.00© 1982 Blackwel! Scientihc Publications .V. F. Ham eta].

Recovery of riverine vegetation after experimental disturbance: a field test of the patch dynamics concept

“…B. erecta and H. vulgaris present both vegetative and sexual reproduction but it seems that they have fewer competitive abilities than other species . Furthermore, B. erecta does not generally show regular growth patterns but often increases at times of the year when other species are in recession (Ham et al, 1981 ;Ham et al ., 1982), and this can explain that it did not occur at the same period as the good colonizers, and did not reestablish rapidly after a disturbance .…”

Analysis of Flora and Vegetation in Rivers: Concepts and Applications

“…For the study of small scale pattem, and also for succession, several methods have been used, for example the very precise study of Jones (1955) mapping individual plants, or the studies of Ham et al (1981Ham et al ( , 1982 and Wiegleb (1983) also referring to small sample plots and using more precise estimation methods.…”

“…(a) Intensive studies that follow the variation of vegetation within a year and from year to year (Wiegleb 1983, Ham et al 1981, Ham et al 1982 General prineiples of ehange, whieh were supposed by Segal (1971) based on his observation in Duteh waters, eannot be realized. Exaet eauses for the observed ehanges ean only be given in ease of intensive study.…”

Spatial and temporal occurrence of invertebrates in a chalk stream, Berkshire, England

“…Each site was mapped monthly in order to document the seasonal growth and recession of the macrophytes and the way in which the other substrata (gravel and silt) varied seasonally and between years in relation to discharge (Ham et al, 1981;Ham et al, 1982). Sampling of the invertebrate fauna was closely linked to the monthly mapping operations and between March 1971 and February 1972 a comprehensive monthly sampling programme was undertaken for invertebrates.…”