what biotic and abiotic resources in the boreal forest limit size of organism populations?

Answer 1

Organisms in the boreal forest are limited by the amount of (a) heat and (b) light penetarting the canopy. Boreal forest differs from equatorial forest in this way primarily because it is COLD much of the year and relatively CLOUDY. Photosynthesis is nowhere near as rapid as in the tropics. When it does rain, the soil can easily become waterlogged and relatively acid in pH because evaporation is low below 20 deg C and very low below about 10 deg. In places where snow lies regularly, mammals such as foxes can live but there will be few if any cold-blooded creatures such as snakes and lizards, creatures that need to warm up in the morning sun before they can get going.

Answer 2

Today forest health in every country is threatened by the greater movement of people and goods, including various plant materials, considerably increasing the risks of insect and disease diffusion.
The higher incidence and gravity of insect attacks and diseases worldwide can be attributed to two factors: the decrease in natural forests and the increase in plantations and managed and planned forests, which have simpler ecosystems than natural forests; and air pollution in and near industrial and urban areas. Artificial and modified forests tend to have a limited genetic base, in spite of efforts to increase the number and mix of species.