DISTRIBUTION AND ABUNDANCE 



77 



between potassium and geology. Carbonate was slightly associated 

 with geology, so that the preference of the frogs for ponds liigh in 

 carbonate was not so certain. Phosphate was not investigated at the 

 same time nor in the same way, for instead o( single samples of the 

 water from a large number of ponds, weekly samples were taken from 

 six non-spawn ponds and eight spawn ponds, from January to April. 

 Phosphate is one of the plant nutrients that may become depleted in 



HIBERNATION 



PRE- 

 SPAWN 



SPAWN 



16 26 

 JANUARY 



I 5 25 

 FEBRUARY 



17 27 

 MARCH 



APRIL 



Fig. 24. The Course of Phosphate Concentration in Spawn 

 Ponds and Non-spawn Ponds, from January to April 



The first two points of the non-spawn ponds are fi-om single records. The 

 thick line and solid dots indicate the non-spawn ponds, the thin line and open 

 dots the spawn ponds. The non-spawn level is about twice that of the spawn 

 pond level. Note that the rain affects the non-spawn ponds more than the 



spawn ponds. 



ponds where the plants are growing rapidly, and is replenished when 

 rain washes it into the pond from the land. It is therefore interesting 

 to note that it was just this reciprocal relation that was observed. 

 Fig. 24 shows the results. The first two points for the non-spawn ponds 

 may not be reliable, because they were based on only one pond, 

 but at all other dates the values for the non-spawn ponds lie above 

 those for the spawn ponds. Moreover, both curves tended downwards 

 all through the dry January and February, and when rain fell in March, 

 the phosphates, replenished by the run-off, rose more in the non- 

 spawn ponds. After the middle of March, both tended downwards. 

 This suggests that plant activity was higher in the spawn ponds, and 

 it was, of course, these that tended to have high potassium. The result 



