summary怎么写

summary about trees
trees are important to our life.trees provide oxygen to us.as we all know during photosythesis,carbon dioxide is taken in while oxygen is given off b the trees.so trees are very important as they replanish the air.trees are also natural resources,we uesed trees to make paper and furniture,we eat the fruits which bear from the tree.besides all these,trees also help to save our environment.the roots of the trees can hold the soil firmly which helps to reduce the chances of surface run-off,soil erosion and even land slide.less sol particles will be washed into the river by rain,thus there will be less water pollution and floods.
leaves are natural fertilizer.when the leaves fall onto the ground.they will decay gradually.the decomposed leaves are source of nutrients which can fertile the soil.
in conclusion,trees are useful in many ways,and they are very important to us.