Re: In temperate grasslands, what is the limiting factor limiting plant growth?

Dear Alex,
	I  think the answer you need is two-fold;
Firstly the plants in grassland tend to form huge communities of single
species which can resist the cold winters, hot Summers and light rainfall 
(water shortage). Secondly, because of this lack of biodiversity, there is
less variety in the producers to feed the animals, and their predators too.
Many species inhabit these vast areas, excepting tree species and the
animals which would live in or on them. That alone could account for the
lack of biodiversity. On an emotional level, the organisms which use this
biome for their habitats can be just as fascinating in their adaptations
and their huge successes in overcoming natural problems as their relatives
in tropical forests, however. Think of Rhinos and early man as just two
examples!
You won’t find direct answers in your text unless you diversify into
different types of source. I would always use Wikipaedia to check unknown
answers, although there are dangers in relying on just one source once
again. (Don’t worry, in your case I can see why Wiki was virtually
useless!). Perhaps you can work on these ideas I gave you and concentrate
on the prairies, or better-preserved - the steppes, to work on species
lists for your project or homework. Then ask another question if you need
to and we’ll quickly get back to you.