Fig. 15

Block Cutting

Trees like the Douglas-fir need full sunlight for proper growth. Also, their seeds are carried a good distance by the wind. For these reasons the accepted way of harvesting Douglas-fir is to cut all marketable trees in a block of 100 acres or less. Ample standing timber is left between blocks. Seeds blow in from the surrounding forest and new trees appear. The new stand is thinned periodically to provide growing space and to remove undesirable trees. In about 40 years the 1st cut-over block is mature enough to provide seed for the neighboring block. After a few more decades the 1st block can be harvested again.

Seed-Tree Cutting

Southern pines also need sunlight, and their seeds are carried by the wind. Isolated trees are relatively windfirm. It is therefore possible to remove all trees from a large area except for 4 or 5 per acre, which act as seed trees. These remain until the new seedlings are established. When teh seedlings have grown enough so that they are reasonably safe from fire–5 to 10 years–the seed trees can be removed in their turn. After about 20 years the new stand of pine should be thinnned to prevent crowding. Under favorable conditions the pines can be harvested 30 years after original cutting.

Selective Cutting

Yound red spruce will grow in the shade of larger trees. Thus trees of all ages and sizes are found growing side by side. In harvesting red spruce the most mature and marketable trees are selected for cutting. (In this picture they are the trees shown slightly darker than the others. After the marketable trees have been removed their neighbors provide seed for the new trees that will replace them. In the meantime other trees are maturing. In 10 to 20 years these trees are ready to be harvested in their turn. If carefully harvested, a forest of red spruce can provide a continuous supply of marketable trees.

Fig. 15. Harvesting systems in forest management. [After St. Regis Paper Co.]

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Block Cutting

Trees like the Douglas-fir need full sunlight for proper growth. Also, their seeds are carried a good distance by the wind.	For these reasons the accepted way of harvesting Douglas-fir is to cut all marketable trees in a block of 100 acres or less. Ample standing timber is left between blocks.	Seeds blow in from the surrounding forest and new trees appear. The new stand is thinned periodically to provide growing space and to remove undesirable trees.	In about 40 years the 1st cut-over block is mature enough to provide seed for the neighboring block. After a few more decades the 1st block can be harvested again.
Seed-Tree Cutting

Southern pines also need sunlight, and their seeds are carried by the wind. Isolated trees are relatively windfirm.	It is therefore possible to remove all trees from a large area except for 4 or 5 per acre, which act as seed trees. These remain until the new seedlings are established.	When teh seedlings have grown enough so that they are reasonably safe from fire–5 to 10 years–the seed trees can be removed in their turn.	After about 20 years the new stand of pine should be thinnned to prevent crowding. Under favorable conditions the pines can be harvested 30 years after original cutting.
Selective Cutting

Yound red spruce will grow in the shade of larger trees. Thus trees of all ages and sizes are found growing side by side.	In harvesting red spruce the most mature and marketable trees are selected for cutting. (In this picture they are the trees shown slightly darker than the others.	After the marketable trees have been removed their neighbors provide seed for the new trees that will replace them. In the meantime other trees are maturing.	In 10 to 20 years these trees are ready to be harvested in their turn. If carefully harvested, a forest of red spruce can provide a continuous supply of marketable trees.