. Bulletin. Natural history; Natural history. Aug. 1979 Bellrose et al.: Waterfowl and the Chancing Illinois Valley 21 R = r = 0,01- 0,01 200 I 600 11000 I WOO I 1800 I 2200 I 2500 0 too 800 1200 1600 2000 2400 MOIST-SOIL WATER-LEVEL INDEX Fig. 7.—The linear relationship of the Moist-Soil Water-Level Index to the abun- dance of moist-soil plants per hectare of lake basin in the Illinois River valley. lake basins covered with moist-soil plants likewise increased. The coef- ficient of determination (R^ = ) in- dicates tliat about 60 percent of the annual
. Bulletin. Natural history; Natural history. Aug. 1979 Bellrose et al.: Waterfowl and the Chancing Illinois Valley 21 R = r = 0,01- 0,01 200 I 600 11000 I WOO I 1800 I 2200 I 2500 0 too 800 1200 1600 2000 2400 MOIST-SOIL WATER-LEVEL INDEX Fig. 7.—The linear relationship of the Moist-Soil Water-Level Index to the abun- dance of moist-soil plants per hectare of lake basin in the Illinois River valley. lake basins covered with moist-soil plants likewise increased. The coef- ficient of determination (R^ = ) in- dicates tliat about 60 percent of the annual coverage of moist-soil plants was related to the Moist-Soil Water- Level Intlex. Small rises in water during the growing season of moist-soil plants destroyed extensive areas of these plants, the extent depending upon the lieight of the rise and the lateness of the season. The havoc that these mid- sununer fluctuations wrought on the development of moist-soil plant beds is only partially measured by the Moist- Soil Water-Level Index and is the ])rincipal reason that it accounted for only 60 percent of the plants' coverage of lake ijasins. Once eradicated by a brief inundation, moist-soil plants might not have sufficient time to regen- erate, or mud flat areas might be re- duced. Effects on Aquafic and Marsh Plants Through the years, 1938-1959, only a small coefficient of determination oc- curred between the area covered yearly by aquatic and marsh plants and the yearly variation in the seasonal fluc- tuation of water levels. The Water- Stability Index for seasonal stability on all lakes studied compared with the development of marsh vegetation gave a coefficient of determination of (11 percent of the variable accounted for by fluctuating levels); for aquatic plants it was ( percent). Two items were proposed for further analysis: (1) Water levels had various effects on aquatic and marsh plants in different lakes that we attributed to difl^erent elevations and b
Size: 1314px × 1902px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., booka, bookcentury1900, bookdecade1910, booksubjectnaturalhistory
