How would using trees as sarcophagi affect the forest?

Question

Long story short the people of the forest use trees to 'bury' their dead instead of actually burying them into the ground. They use plant-manipulation magic to accomplish this, making the tree open up a hollow inside itself where they put the bodies into and then use magic to seal the tree back up, making the area where the body is stored bulge out a little bit because of the space that has been made inside it. Think of it like gradually turning a forest into one giant above ground crypt with the trees acting as living wooden sarcophagi.

The seal is not always air-tight and would sometimes allow air or fluid leakage. The surface of the inside of the hollow is covered in bark due to how the magic works and is as protected from damage as the tree is from the outside so it's not like the tree's innards are entirely exposed to all of the processes of bodily decay but it still concerns me enough to think about how this practice would affect the trees and in turn the forest's health as a whole.

How would using trees as sarcophagi affect the forest?

They've been doing this for hundreds of years, if that helps. The forest's trees are similar to oak trees.

Answer 1

Preternatural vigor

A tree will capture the nitrogen and phosphorus from the decaying corpse. These trees will become unusually vigorous from their diet, putting forth an enthusiastic profusion of growth. An unnatural profusion. Even the roots will sprout, pushing forth new growth from underground.

https://www.plantanswers.com/live_oak_root_sprouts.jpg

The area around the tree turns into thicket, eventually fusing with the trunk of the mother tree and forming an oak like a banyan, with corded, knotty tentacles reaching from the earth...

Answer 2

It can lead to the formation of a forest of mummies...

There are some things loggers expect to come across when cutting down trees. Bird’s nests and things stuck in the branches seem like a given – a mummified dog in the center of a tree, however, does not. But that’s exactly what a team of loggers with the Georgia Kraft Corp. found while cutting down a tree in the 1980s. The loggers were working on a grove of chestnut oaks in southern Georgia when they found a most unusual sight.

After cutting off the top of the tree, and loading it onto a truck for transport, a member of the team happened to peer down the hollow trunk. Inside, he found the perfectly mummified remains of a dog, looking back at him, its teeth still bared in a fight for survival.

Experts who studied the carcass concluded that the pup was most likely a hunting dog from the 1960s, who had chased something such as a squirrel through a hole in the roots, and up the center of the hollow tree.

The higher the dog got, however, the narrower the tree became. From the position of the dog’s paws, experts believe that it continued to climb until it effectively wedged itself in. Unable to turn around, the dog died.

Normally, a dog that had died in the wild would succumb to decay and be eaten by other foragers. However, as the dog had died inside a tree, it was unlikely that other animals could reach it – and, due to the height of the body, it was unlikely that other animals could smell it either.

Additionally, the kind of tree that the dog had lodged itself in was uniquely qualified to lend itself to the natural mummification process. Chestnut oaks contain tannins, which are used in taxidermy and tanning to treat animal pelts so that they don’t decay. The tannins from the inside of the tree seeped out into the dog and prevented it from rotting inside.

The dry environment inside the trunk also provided shelter from the elements and sucked the moisture from the carcass. The air that was sucked into the tree through the base created a sort of vacuum effect, further contributing to the drying process.