Patch dynamics of the stream macrophyte, Callitriche cophocarpa

Abstract

1. We examined changes in position and growth of Callitriche cophocarpa patches in a shallow section of a small Danish streain during the main expansion of plant cover between April and June. Mean upstream growth of patches was only 7.5% of downstream growth. The mean growth rate was 1.02cm day ~' in length and 0.55 cm day "' in width and the growth rates were not significantly dependent on patch size. For patches with an area (A) above 100 cm^ the growth rates in patch area (dA/dt) was proportional to patch circumference and thus y/Aand the relative growth rate {dA/dt A~^) was inversely proportional to y/A.The smallest patches (<100cm^), however, expanded less than expected because of their combined tendency to grow more slowly in patch length and width than larger patches. 2. The expansion of plant cover will be much more rapid in many medium-sized patches compared to few large patches of a similar combined area, because internal selfhmitation by light and space is partially relieved in smaller patches. We anticipate that recruitment and mortality of new-formed patches are critical steps preceding areal expansion. Quantification of these processes are needed fully to evaluate patch dynamics and space occupation.

Underwater Photosynthesis of Submerged Plants – Recent Advances and Methods

“…In softwater containing only 0.15 mmol L −1 ${\text{HCO}}_3^{-}$ the supply rate of the two carbon species would be the same. Terrestrial plant species lack these adaptive features for aquatic life, and when underwater their leaves show dramatically reduced net photosynthesis (Sand-Jensen et al, 1992; Nielsen, 1993) and dark respiration (Colmer and Pedersen, 2008; Pedersen et al, 2009). Thus, 13 terrestrial species submerged in CO 2 rich stream water were unable to use ${\text{HCO}}_3^{-}$ and median rates of underwater net photosynthesis were sevenfold lower than of 10 permanently submerged stream plants and the terrestrial species were unable to support substantial growth (Sand-Jensen et al, 1992; Figure 2).…”

Velocity gradients and turbulence around macrophyte stands in streams

“…The relatively dense canopies will have strong shear forces concentrated at the canopy surface where most of community photosynthesis will take place because of high light intensity and high tissue density (Bijl et al, 1989). The intense turbulence may physically damage the apical tissue and enhance respiratory costs because of leaf flapping (Madsen, Enevoldsen & Jùrgensen, 1993), while tissue deeper into the canopy will be physically protected and nutrient-rich fine particles can accumulate on shielded sediment surfaces (Sand-Jensen & Madsen, 1992;Sand-Jensen, 1998). The pressure drag will be high on the plant stands because of the profound pressure drop from the upstream front to the downstream front.…”

“…Submerged stream macrophytes often form a patchy mosaic of dense monospecific stands which undergo temporal changes in size and location (Butcher, 1933;Gessner, 1955;Sand-Jensen & Madsen, 1992). The stands usually have well-defined margins, leading to strong gradients in water velocity, turbulence and sediment composition at the plant-water boundaries (Chambers, Prepas & Gibson, 1992;Sand-Jensen, 1998).…”

A Survey of the New River Aquatic Plant Community in Response to Recent Triploid Grass Carp Introductions into Claytor Lake, Virginia

“…), a reach that was not sampled in this study. Suitable habitat for aquatic plants in riverine environments is often limited by flow conditions (Butcher 1933, Sand-Jensen and Madsen 1992, Sprenkle et al 2004) as well as through variations in dispersal (Bunn and Arthington 2002, Riis and Sand-Jensen 2005, Santamaria 2002, often leading to patchy distributions on the landscape. Similarly, the amount of plant fragments collected in our drift-net samples varied greatly among sites, which could be attributed to the high gradient and primarily bedrock channel of the upper New River.…”