Many plant species are found in the Taiga, but coniferous trees are obviously the dominant plant form. These trees shed snow easily, and they retain their needles through the winter. The conical shape of many conifers prevents too much snow from accumulating and breaking their branches. The needles themselves are well-adapted, with thick waxy coatings and small surface area, to resist cold conditions and minimize water loss, an important consideration even in the swampy taiga where water may be frozen much of the year. Together, these adaptations mean that even in cool conditions, if the temperature rises above freezing during the day photosynthesis can proceed. Broadleaf plants usually lose their leaves at the onset of freezing conditions in the fall and will not regrow them until most of the danger of frost has passed. This means that the growing season of broad-leafed trees is much shorter than it is for coniferous trees, and the advantage the coniferous trees gain allows them to dominate in the cold taiga climate (note that broad leaves are much more efficient, so if conditions are favorable (warm and moist) they are the preferred leaf type). Important conifer types include firs and pines, spruces, hemlocks, and larches. All of these tree types bear cones of one sort or another. The seeds are retained in these structures until they open and cast the seeds out, often from a considerable height. Some species of birds and mammals may also open the cones foraging for the seeds. With two seeds per scale, it is likely that as the animal breaks one seed loose the other will fall free to the forest floor. Some cones do not open until there has been a fire, but since fire is not an important aspect of the taiga that is probably not the case for most taiga conifers. In addition to the conifers, mosses and lichens are also important in the taiga and may be an important part of the diet for many animals. The diversity of plants in the shrub and herb layers of these forests is lower than in temperate broadleaf forests.