224 V. Alexander et al. 

 ROOTED AQUATIC PLANTS* 



Biology 



There are three rooted aquatic plants found in the shallow ponds at 

 Barrow: Carex aquatilis, Arctophila fulva, and Ranunculus pallasii. Only 

 the first two are important in the ponds we have studied, although in the 

 immediate area of the research site ponds can be seen that are completely 

 covered by each of the three. Carex aquatilis is also one of the three 

 dominant terrestrial plants and so was intensively studied in the terrestrial 

 IBP study (see Brown et al. 1980). Arctophila fulva, on the other hand, is 

 found only as an emergent in standing water. 



Within the ponds we have studied, C aquatilis is found in a pure 

 stand in the shallow water less than approximately 15 cm in depth, while 

 A. fulva is found in a pure stand in slightly deeper water (15 to 25 cm). In 

 pond J in 1971, C aquatilis occupied 32% of the pond area while A. fulva 

 covered 13%. These percentages vary from pond to pond, of course, and 

 the depths will also change with changes in water level of the pond. In 

 some summers the entire C. aquatilis zone will become dry land. 



Reproduction in the monocots at Barrow is usually vegetative 

 (Johnson and Tieszen 1973). The result is that C. aquatilis, for example, 

 produces a network of individual tillers connected by subsurface rhizomes 

 (Shaver and Billings 1975). These authors define tiller as "the horizontal 

 rhizome, stem, stembase and leaves originating at the point of insertion of 

 the rhizome at the parent plant or 'mother tiller'." A typical part of this 

 network (Figure 5-29) contains both spreading tillers, which produce 

 almost all of the roots, and their daughter tillers called clumping tillers, 

 which rarely produce roots or daughter tillers. 



The life history of Carex is well known but we know little about 

 Arctophila. Both Carex and Arctophila plants have almost complete 

 aboveground die-back each year so that almost 100% of the living biomass 

 is underground during the winter. Growth begins only when the snow and 

 ice melt in mid-June. At this time, most surviving leaves are brown except 

 for some with several centimeters of live material at the leaf base (Tieszen 

 1978a). These elongate rapidly at first (about 4 mm day ^) and must draw 

 on nutrient reserves from the stem base and rhizome as the roots are still 

 frozen. In a typical Carex plant (Tieszen 1978a), two leaves had started 

 growth the previous season; these attained their maximum length by 9 July 

 after which they senesced. Other leaves (no. 3, 4, 5) exserted early in the 

 season, grew for about 25 days, remained mature for another 20 days, and 

 then senesced. Total leaf life for these three leaves averaged around 48 

 days. Finally, on terrestrial sites some tillers produced a sixth leaf later in 



*C. P. McRoy 



