Cutting trees and selling logs or turning them into wood chips is a new feature in Farming Simulator 15. The player can use special equipment the enables him to manage forested areas. Cut trees in small forests. You will find a few on both maps.
The first tool that you will need is of course a chainsaw (it costs only 1000$). Using it, you will be able to cut trees and trim them to appropriate length. There are three types of chainsaw in the game, which you activate by pressing ,  or . After choosing the saw, you can rotate it using [J] and [N]. To cut down a tree, the chainsaw has to be rotated a bit. Next, approach the tree and notice a blue circle on it, which shows you where exactly you will be cutting. Now you just have to choose the right place (the lower the better) and start the engine [hold LMB]. When you start cutting, the circle will turn green and the chainsaw will start moving automatically. After the tree falls down, you can cut it into transportable pieces. Remember to get rid of the branches.
When you have some more money, you can make the process of cutting trees quicker, by purchasing a special machine - Scorpionking (it costs 317 000$). Cutting trees with it takes only a moment. First, you have to drive close to the chosen tree, place the harvester in appropriate position and set the length [O]. Next, start the harvester [B] and press [X] cut. The machine will "grab" the tree in the chosen place. Then, cut as many times as you need, to divide the tree into even pieces (you can change the size of the log at any moment).
The next, slightly more difficult step, is to load the wood onto a trailer. You need a special machine for that - FHL 13 AK (later - Buffalo - the crane works the same way, but you don't need to switch places). In FHL 13 AK, you have to first drive with a tractor to a chosen place and than go to the machine at the back. The most difficult thing here is to learn to properly operate the crane, as there are a lot of options. You can raise or lower the whole loader ([N], [J]), and move it to the sides ([M]/[K]). Moreover, when holding [CTRL] and pressing the keys responsible for moving the crane, you will move the whole trailer. Also, when holding [SHIFT] and pressing [N] or [J], you can bend one of the arms (it will allow you to place the logs with precision) and by pressing [M] or [K], you can extend the arm. There's one more combination - [CTRL] + [SHIFT] with [N] or [J] moves the grab and [K] or [M] opens and closes it. As you can see, it's complicated even in theory and you will have to spend a lot of time to learn to properly do it in practice.
During loading, first place the grab above the log, lower it a little and eventually catch the log. Next, pick it up as high as you can, bend the arm and place the log in the right place. The log shouldn't stick out from the vehicle too much.
When you load enough logs, you can go to the shop and sell them. You just need to pick them up from the vehicle and throw into the pond. If you drop some log accidentally and it won't reach the water, you just need to push it there with the tractor. For one log, you will receive about 3700$. Generally - the longer and thicker the log, the more money you get. One tree of average size will give you should give you 12 000$ - 13 000$. You can also sell the wood by unloading it near the train.
Selling logs is not the only way of earning money here. If you cut a tree onto smaller pieces (about 2m), you can use it to make wood chips. You will need HEM 538 Z, which costs 88 000$. Grab a log with the crane and place it near the wood chipper. Don't forget to place a tractor with a trailer on the other side, to collect the wood chips. From 5m of wood, you will make about 4t of chips, which will earn you about 3000$. Selling logs is more profitable and you don't need a trailer and a tractor.
When you cut some part of the forest, it will be time for removing the stumps. The machine you will need is very cheap, as it costs only 5000$. It is good to remove cut trees and plant new ones. Place the machine right next to the stump and switch it on. After a while, the stump will be gone. However, this task is not obligatory - you can plant new trees next to the stumps or in some other place.
Planting new trees is the last task that you need to complete. Remember about being environment-friendly. This task requires you to by a special machine - PL 75 for 26 000$. You can buy seeds in the Garden center. Now, choose an appropriate place and start the machine. You will see young trees appearing on the ground. Plant trees in advance, as they need a few days to grow. However, this task is not obligatory, as there is a lot of trees on the map, but if you do a lot of woodcutting, they may eventually end.
Woodcutting is very time-consuming, but also very profitable. To start this business, you only need a chainsaw (1000$) and a machine for transporting logs (54 000$). The biggest difficulty here is operating the crane, with which you pick up and place the logs on the trailer. If you have the two best machines in the game, you can shorten the process of cutting to a few moments and the Buffalo will allow you to transport a lot of logs in one trip. You can earn a lot on woodcutting, but eventually the tasks may appear as very boring and irritating.