IB Biology SL B4.1.3 Abiotic Variables Affecting Distribution Topic Practice

The tundra ecosystem in Finnish Lapland has a short growing season and a mean temperature of $-2.0^{\circ} \mathrm{C}$. It is also naturally grazed by herbivores such as reindeer (Rangifer tarandus). Different quadrats were set up to include and exclude the reindeer in both normal and warmed temperatures. Open-topped warming chambers were used to heat both the soil and air in the warmed quadrats. The graph shows the changes in plant richness over five years.

Identify two abiotic limiting factors on plant growth in a tundra ecosystem.