Cold ecosystems, such as tundra and alpine grassland, are the least responsive to elevated CO 2 , in some cases showing no growth 
(Cold ecosystems, such as tundra and alpine grassland; are; the least responsive to elevated CO 2) (some cases; showing; no growth)
Cold ecosystems, such as tundra and alpine grassland some cases
are showing
the least responsive to elevated CO 2
no growth