Growth and recession of aquatic macrophytes on an unshaded section of the River Lambourn, England, from 1971 to 1976

Abstract

Freshwater Biology i\9S]) n, Growth and recession of aquatic niacrophytes on an unshaded section of the River Lamhourn, England, from 1971 to 1976 SUMMARY. The growth and recession of the macrophytes on an unshaded f section of the R. Lamboum was documented by a mapping procedure from March 1971 to December 1976. The seasonal patterns were determined mainly by the dominant macrophytes. RanututUiis penicillalns var. calcareus and Ranuncultis peltatiis. Ranunculus grew rapidly in spring and early summer, mainly colonizing areas of gravel and reached a summer maximum. TTie greatest loss of plants was in August and September but losses continued through the winter to give minimum cover in March. Berula and Callitriche did not show regular seasonal growth patterns but their 'growth was largely confined to times when there was little growth of Ranunculus. Increase in area of Ranunculus in the spring was positively correlated with the mean discharge at that time. The growth of Ranunculus appeared to be restricted when shading was caused by turbid water due to dredging or by accumulation of epiphytic algae on the surface of the plants in years when discharge was low. Discharge also influenced the substrata underlying Ranunculus and the area of silt under Ranunculus beds was negatively correlated with discharge. The factors thought to influence growth of Ranunculus were used to develop a conceptual model of growth.

Measuring submerged macrophyte standing crop in shallow rivers: A test of methodology

“…Our estimated values of macrophyte standing crop over a cycle of growth and recession were within the seasonal ranges reported in other studies of the chalk river macrophyte community (Dawson, 1976;Ham et al, 1981;Armitage and Cannan, 2000;Flynn et al, 2002). Percentage cover, percentage volume, and dry weight 8 biomass co-varied in accordance with our first hypothesis, concordant with previous studies which had reported positive relationships (O'Hare et al, 2010b;Yin et al, 2011).…”

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

“…Although biomass and cover do not necessarily show a simple linear relationship (Dawson, 1976), percentage cover is also considered as a good measure of plant abundance too (Kershaw, 1973 ;Ham et al, 1981), and is easier to evaluate . The sampling method used the cover scale of Braun-Blanquet (1932) but, because of the non-linear nature of this scale, it was necessary to convert it into cover percentages for the statistical analysis .…”

“…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.…”