It maters imensly but as Bam has said in moderation and more importantly gather your wood over a vast area instead of one part of the wood.
The following extract is taken from the BTCV woodland book.
Rotting wood, both on and off the tree, is a very important habitat for invertebrates. The information below refers to fallen deadwood.
Clearing up and removing or burning rotting timber is an act of vandalism, which in a single act can destroy an important invertebrate habitat. The general rule is that fallen, rotting wood should be left where it is. Large fallen trunks and branches are particularly valuable, and should never be rolled over, chopped up or otherwise disturbed. This can easily happen, either by misguided 'tidying up', or as thoughtless destruction by children for example.
Large dead or dying branches on trees should not be removed unless they are a danger to the public.
Old, rotting wood should always be left where it is, unless you have to move it, for example, to clear a path. In that case, move it carefully the smallest distance, and leave it under similar conditions of light and shade, the same way up, and with the same orientation.
Newly cut wood
Thinning, coppicing or clearance work in woodlands produces a large volume of cut material. For commercial operations, much of this material will be removed from the wood. Where management is mainly for conservation or amenity, commercial use of the cut material may not be feasible. In this case, larger cut material is best left where it falls. Sned off the smaller side and top branches.
Scattered, newly cut coppice poles and thinnings look untidy, and the temptation is to stack them in a neat pile. This should only be done if the wood is going to be removed and reused. Cut poles, branches and trunks are of much greater value to invertebrates if scattered through the wood, rather than piled up, although piles do have some value. Scattered wood not only gives more useful habitat per volume of wood, but it is also less likely to be disturbed in the future, as it will not be attractive to vandals or firewood gatherers. A few piles of cut wood at the edge of a sunny ride or glade is acceptable. If the stacks are likely to get disturbed, either by deliberate or thoughtless action, some old stock netting or similar covering the stack and buried around the base should prove a deterrent. Log habitat piles should be no bigger than about 1m (3') high by 2-3m (6-10') long.
Where stacked wood is going to be removed, it's best stacked somewhere where it will not attract invertebrates or other animals, or the habitat will be destroyed when the stack is taken apart and moved. Preferably stack outside the wood, in a barn or open-sided shelter, or partly cover the stack with plastic to reduce the entry of invertebrates.
Brushwood
The smaller branches and twiggy growth produced from felling and clearing takes up a lot of space. The option of burning versus other methods is discussed on page 86. Cut material is useful for dead hedging (see coppicing) access barriers, or it can be bundled or chipped for uses outside the wood (see felling, clearing and extraction). 'Habitat piles' of twiggy material, left in shady conditions in the wood, are of little value for wildlife. Such material further reduces light reaching the woodland floor, so damaging the woodland flora, and is a nuisance for access and management. Piles of brash left in open spaces can be a quick way of producing a scrub or woodland edge type habitat, with bramble and other plants rapidly disguising the brash and providing a habitat for birds, small mammals and other creatures.
This can normally only 'use up' a small proportion of the total brushwood produced. For invertebrates, brushwood is of greater value if bundled tightly, rather than in a loose pile, as well as taking up less space. The close packing provides relatively constant moist conditions in the centre of the bundles. Tie the material as for fascines (see coppicing), and stack the bundles in dappled shade.
Creating deadwood habitats
In addition to the procedures above for cut material, other measures can be taken to increase the amount of deadwood in a woodland.
In commercial woodlands, thinning operations favour the straightest and healthiest trees, and remove those that are misshapen or damaged. In non-commercial woodlands, it's possible instead to keep trees which have splits, sap runs, fungal growth or other signs which indicate premature rotting. Jagged stumps, splits and holes in the trunks of trees are potentially very useful, and should not be treated or tidied up. One can even go so far as to damage an otherwise healthy tree, although this is best done without publicity!
Newly felled timber can also be brought in from elsewhere, into an area of new woodland. Trunks of trees or large branches from thinning operations, storm damage or other sources can be transported to the wood, and placed on the ground in dappled shade where they are unlikely to be disturbed. Trunks can also be set upright, to provide standing deadwood habitat. This should only be done if you have the skills and equipment to handle and position the timber. Choose a location where the dead tree will not be a danger to the public in following years as it rots. Set it upright in a deep hole, secured by wire guys as necessary.
