Seamus Heaney, photographed at his home in Dublin in 2009: ‘Behind the unforced charm he was one of the most formidable critical intellects of his day.’ Photograph: Antonio Olmos

My first thought on hearing the immeasurably sad news of Seamus Heaney's death was a sensation of a great tree having fallen: that sense of empty space, desolation, uprooting. Heaney's place in Irish culture – not just in Irish poetry – was often compared to that of WB Yeats, particularly after he followed Yeats in winning the Nobel prize in 1995. He possessed what he himself ascribed to Yeats, "the gift of establishing authority within a culture". But whereas Yeats's shadow was seen, by some of his younger contemporaries at least, as blotting out the sun and stunting the growth of the surrounding forest, Heaney's great presence let in the light. Part of this was bound up in his own abundant personality. Generosity, amplitude and sympathy characterised his dealings with people at every level, and he was the stellar best of company. It was as if he had learned the lesson prescribed (though not really followed) by Yeats: that the creative soul, "all hatred driven hence", might recover "radical innocence" in being "self-delighting, self-appeasing, self-affrighting".

But behind the marvellous manner, unforced charm and wicked hoots of laughter he was one of the most formidable critical intellects of his day, a powerfully subtle analyst of political and social nuance, and the possessor of intellectual antennae that let nothing past them. Living in Ireland and being world-famous was not an unmixed blessing – he described the effects of winning the Nobel as "a mostly benign avalanche" – and he knew how to elegantly evade the occasional begrudgery of others and withdraw into his own resources, sustained by a beloved family life. The distinctiveness of his poetry was unmistakable: a Heaney poem carried its maker's mark on the blade. So was the immense labour that went into the deceptive simplicity of his early collections (throughout his writing career he drew terrific metaphors and images from an extraordinary range of physical work practices). And part of the impact of that early work lay in his use of violence.

That this was often done by implication made it no less shocking; the authentic lifting of the hairs on the back of the neck that I still remember when I opened North (1975), with its exploration of the archaeology of atrocity, was replicated in reading Station Island (1984), with its extraordinary title poem tracing a ghostly Dantean journey through the shades of Irish history, meeting with the dead. This culminates in a visionary encounter with Joyce ("His voice eddying with the vowels of all rivers/ came back to me, though he did not speak yet,/ a voice like a prosecutor's or a singer's,/ cunning, narcotic, mimic, definite"), and Joyce spoke to Heaney in more ways than one. Listening to him on Desert Island Discs some years ago, I waited for him to choose Yeats's poems as his elected book, only to hear him demand Ulysses instead; on reflection I was not surprised. His own capaciousness was Joycean.

Like Joyce, Heaney's erudition was immense, and his lectures on literature at Oxford, Harvard and worldwide made wonderful reading and unparalleled listening. They illustrate his openness to world literature and classical history as well as his deep love of unexpected English poets such as Clare and Wordsworth – and his affinity with writers from eastern Europe, Osip Mandelstam above all. "There is an unsettled aspect to the different worlds they inhabit," he wrote in The Government of the Tongue(1988), "and one of the challenges they face is to survive amphibiously, in the realm of 'the times' and the realm of their moral and artistic self-respect." This carried – as he himself pointed out – a resonant echo for a poet afflicted by "the awful and demeaning facts of Northern Ireland's history". He lived in Dublin but never evaded those "facts" of his native territory. Indeed, part of Heaney's immense achievement was to use and expand that "awfulness" and its relation to the creative spirit and artistic commitment, using implication rather than assertion – whether in the haunting parallels and allegories of North, or in later poems like From the Frontier of Writing and From the Republic of Conscience.

The note is there also in his wonderful last collection, Human Chain(2010), where one is pulled – yet again – in the wake of a writer able to push out the boat into a limitless sea. But what struck me most in reading it, along with the almost daunting economy of line, was a whispering sense of elegy – not just because many of the poems were dedicated to the dead, but also because they looped back to his earliest images of pen nibs, farm routines, animal life, the rituals of neighbourhood, and love. This sense of an ending was perhaps a sign of poetic prescience.

At the time of his death, though, I come back to the image of the death of a tree. I remember now that he wrote about this himself – both in a marvellous 1985 essay on the work of Patrick Kavanagh, and then in a sonnet sequence, Clearances, in memory of his mother. The tree in question grew from a chestnut which his aunt planted in a jam jar in 1939, the year of Heaney's birth; it flourished, was transplanted to the garden, became a fully sized tree "that grew as I grew" and came to symbolise his own developing life – until, in his early teens, the family moved away from the house and the new owners cut it down. The absence of the tree then created in Heaney's mind "a kind of luminous emptiness". He now identified, he wrote, with "preparing to be unrooted, to be spirited away into some transparent, yet indigenous afterlife". This is the thought that he put into Clearances (whose final sonnet is below), and I think of it now as I remember the marvellous spirit of a great poet who was also a great man.

I thought of walking round and round a space
Utterly empty, utterly a source
Where the decked chestnut tree had lost its place
In our front hedge among the wallflowers.
The white chips jumped and jumped and skited high.
I heard the hatchet's differentiated
Accurate cut, the crack, the sigh
And collapse of what luxuriated
Through the shocked tips and wreckage of it all.
Deep-planted and long gone, my coeval
Chestnut from a jam jar in a hole,
Its heft and hush became a bright nowhere,
A soul ramifying and forever
Silent, beyond silence listened for.

• Roy Foster
• The Observer, Sunday 1 September 2013

Acceptance of his Nobel Prize lecture: http://www.nobelprize.org/mediaplayer/index.php?id=1506

http://www.theguardian.com