248 V. Alexander et al 



aboveground leaves; growth begins from the stem base immediately after 

 snow and ice melt in mid-June. Even though the roots may still be frozen, 

 the leaves elongate rapidly in late June and the two original leaves may 

 attain their maximal length by 9 July and then begin to senesce. Other 

 leaves appear a little later in the season, grow for about 25 days, remain 

 mature for about 20 days, then senesce. Each plant produces around five 

 leaves each year and 20 to 30 during its lifetime of 4 to 7 years. 



In a typical pond, the aboveground biomass of C. aquatilis was 170 to 

 230 g dry wt m *^ while that of A. fulva was 10 to 23 (July and August). 

 Biomass reached a maximum in the first week in August and declined 

 rapidly thereafter. However, it is typical of tundra plants that most of the 

 biomass is belowground; accordingly, some 3000 g dry wt m"^ of roots 

 were found for Carex (90 to 95% of total biomass). Arctophila has smaller 

 root systems and a biomass of 31 g of roots was found (57 to 78% of total 

 biomass). The high ratio of root-to-shoot is an effect of low nutrient levels, 

 low soil oxygen levels, and high soil moisture content; it is typical of other 

 plants found in temperate swamps. Carex roots live for 5 to 8 years while 

 Arctophila roots live one year. 



The aboveground Carex production in ponds ranged from 140 to 180 

 g C m"^ yr \ which is slightly higher than production in the terrestrial 

 tundra. Root production is likely about the same amount; the total 

 quantity equals 308 to 396 g C m'^ yr"'. Additional carbon is used in root 

 respiration; this is probably around 320 g C m~^ yr"'. These data are for 

 plant beds; total pond values are 1 /3 of the above. 



Arctophila production was not too important in the intensively 

 studied ponds as it ranged from 1 8 to 2 1 g C m ~ ^ yr " ' in the plant beds. 



The nutrient content of Carex is as high as or higher than that for 

 similar temperate plants. The content did change throughout the growing 

 season, however, and the percent of nitrogen, phosphorus, and potassium 

 reached a peak in mid-July, well before the peak of biomass. By late 

 August, a large quantity of these nutrients had been retranslocated back to 

 the roots and rhizomes for storage. Thus, by 29 August the N content of 

 Carex was 6 to 8% of the content at maximum (both as percent of dry 

 weight). Some structural carbohydrates may also be removed and 

 translocated. Calcium does not change in the plants because it becomes a 

 part of the cell wall. 



Control of Rooted Plants 



The production of plants in the stands within the ponds is actually 

 higher than production in terrestrial sites. One reason for this is the 

 relative lack of standing dead leaves in the pond plants. As a result, the 

 plants of the tundra appear brown while the plant beds in the ponds are 

 green and the light climate for each leaf is much better. The cause of the 



