. Bulletin. Natural history; Natural history. August 1941 BELLROSE: DUCK FOOD PLANTS 253 that during 1938 there was little develop- ment of such plants in the Illinois River valley. A glance at fig. 6 helps to explain this situation. The water remained high in lakes of this type throughout July. Shortly after the water level dropped in August, exposing mud flats, a subsequent rise drowned the immature moist-soil plants commencing to appear. In 1938, Clear Lake had a dearth of moist-soil plants. In 1939, it had an occurred in the Havana region in the lat- ter part of June and throughout July, 1
. Bulletin. Natural history; Natural history. August 1941 BELLROSE: DUCK FOOD PLANTS 253 that during 1938 there was little develop- ment of such plants in the Illinois River valley. A glance at fig. 6 helps to explain this situation. The water remained high in lakes of this type throughout July. Shortly after the water level dropped in August, exposing mud flats, a subsequent rise drowned the immature moist-soil plants commencing to appear. In 1938, Clear Lake had a dearth of moist-soil plants. In 1939, it had an occurred in the Havana region in the lat- ter part of June and throughout July, 1940, than in the equivalent 1939 period. Consequently, an unusual development of wild and Japanese millets, nutgrasses, smartweeds and water hemp occurred in 1940, table 5, on the mud flats of Qui\er,. SCIRPUS FLUVIATILIS NELUMBO LUTEA SAGITTARIA LATIFOLIA SALIX SPP i^ CERATOPHYLLUM DEMERSUM ^ POLYGONUM MUHLENBERGII X POTAMOGETON AMERICANUS â ; POTAMOGETON PECTINATUS n NAJAS GUADALUPENSIS & HETERANTHERA DUBIA Fig. 10.âVegetation map of Lake Chautauqua showing location of principal duck food beds, 1939. Compare this map with that for 1938. Note the increase in American lotus (Nelumbo lutea). Note also the decrease in coontail [Cercitophyllum demersum) and longleaf pondweed {Polamogeton amerhatius). Sago pondweed iPolaniogeton pectinalus) showed an increase in 1939 but has since suffered a marked decline. The decrease in these three species started after 1937, when the levees were repaired, and has continued because the water depth has been held too high for sufficient light intensity to reach those plants that were established when the lake was shallower. A stabilized water level of increased depth has resulted in an encroachment of duck potato iSugit. taria latifolia) on river bulrush (Scirpas fliiriatiliA. abundance of such plants, table 5. This change represents a typical metamorphosis of Class III lakes. As indicated by fig. 6, the water level of the Illinois River at
Size: 2054px × 1217px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
