Como o Cinturão de Melian funcionou?

O poder de Melian e o controle sobre a substância de Arda:

Em primeiro lugar, um pouco de fundo sobre Melian e seus poderes como Maia, bem como seu desenvolvimento em Arda. De baixo, vemos que ela serviu Vána e Estë, que tinham poder sobre a flora e a fauna e para curar todos os males, respectivamente. Ela também era habilidosa em canções de encantamento e tinha poder até sobre os Valar:

Melian was the name of a Maia who served both Vána and Estë; she dwelt long in Lórien, tending the trees that flower in the gardens of Irmo [...] nor more wise, nor more skilled in songs of enchantment. It is told that the Valar would leave their works, and the birds of Valinor their mirth, that the bells of Valmar were silent and the fountains ceased to flow, when at the mingling of the lights Melian sang in Lórien.

For Melian was of the divine race of the Valar, and she was a Maia of great power and wisdom; but for love of Elwë Singollo she took upon herself the form of the Elder Children of Ilúvatar, and in that union she became bound by the chain and trammels of the flesh of Arda. In that form... she gained a power over the substance of Arda.
_{The Silmarillion: Of Beleriand and it's Realms}

Nós vemos que, com o tempo, ela ganhou grande controle sobre seus poderes.

Armadilhas e armadilhas do Cinturão, como isso impedia intrusos:

Note que a única conta verdadeira que temos de alguém sendo impedido no Cinturão é Túrin.

Em segundo lugar, o cinto variou com a localização. Considerando que a maioria de Doriath era cercada por floresta (ver abaixo), as "árvores sem caminhos" provavelmente cercariam Doriath, no entanto certas áreas foram descritas como "envoltas em névoas".

In the south-west of Doriath, where Aros flowed into Sirion, lay great pools and marshes on either side of the river, which halted there in his course and strayed in many channels. That region was named Aelin-uial, the Twilight Meres, for they were wrapped in mists, and the enchantment of Doriath lay over them.
_{The Silmarillion: Of Beleriand and it's Realms}

at last, weary and haggard, they reached the confines of Doriath. But there they became bewildered, and were enmeshed in the mazes of the Queen, and wandered lost amid the pathless trees, until all their food was spent. There they came near to death...
_{The Children of Húrin: The Departure of Túrin}

Este extrato dos Filhos de Húrin, sugere que o Cinturão foi implacável, e provavelmente matou várias pessoas de fome, com Turim só tendo sido salvo por Beleg Strongbow.

Existem também os "Guardiões de Março", embora inicialmente descritos como "caçadores" quando Túrin se torna maior de idade, ele se junta a eles. Nenhum defensor da marcha é chamado de bar do norte, mas os Orcs de Morgoth provavelmente atacariam do norte.

And soon after he put on the Dragon-helm, and took arms, and went away to the north-marches, and was joined to the elven-warriors who there waged unceasing war upon the Orcs and all servants and creatures of Morgoth.
_{The Children of Húrin: The Departure of Túrin}

One only was mightier in arms among the march-wardens of Thingol _{The Children of Húrin: The Departure of Túrin}

Não encontrei nenhuma descrição do tamanho do "anel" ou o que ele abrangia.

Todos os inscritos podem sair à vontade:

The Girdle of Melian does not hinder the going of those that passed in with our leave.
_{The Children of Húrin: The Departure of Túrin}

Inimigos alados:

A única menção de criaturas aladas voando explicitamente declaradas voando perto de Doriath são as Águias de Manwë. No entanto, eles param nas fronteiras. Se isso é porque eles decidiram que voaram longe o suficiente, ou simplesmente não podem entrar é desconhecido.

“And at the last the eagles set them down upon the borders of Doriath;”
_{The Silmarillion: Of Beleriand and it's Realms}

Geografia de Doriath:

Doriath was a realm of forests about the great river Sirion, with in it the forests Neldoreth (also Taur-na-Neldor, the northern beech forest), Nivrim (also West-march, an oak forest), and Region.
_{Tolkien Gateway: Doriath}

Southward lay the guarded woods of Doriath, abode of Thingol the Hidden King, into whose realm none passed save by his will. Its northern and lesser part, the Forest of Neldoreth, was bounded east and south by the dark river Esgalduin, which bent westward in the midst of the land; and between Aros and Esgalduin lay the denser and greater woods of Region. Upon the southern bank of Esgalduin, where it turned westward towards Sirion, were the Caves of Menegroth; and all [All] Doriath lay east of Sirion save for a narrow region of woodland between the meeting of Teiglin and Sirion and the Meres of Twilight. By the people of Doriath this wood was called Nivrim, the West March; great oak-trees grew there, and it also was encompassed within the Girdle of Melian, that so some portion of Sirion which she loved in reverence of Ulmo should be wholly under the power of Thingol.
_{The Silmarillion: Of Beleriand and it's Realms}

Um mapa de Doriath é anexado abaixo (se alguém puder ajudar a identificar a fonte que seria ótima, mas parece algo que Tolkien pode ter desenhado):