Terroir isn’t just about the ground, the grape and the guy: every winery wall, every barrel, every concrete tank is a bustling colony of microscopic life. This, Matt Walls says, is what ’house style’ really means

Is proximity to gum trees the reason why some Australian vineyards produce Shiraz with eucalyptus notes? What about aromas of herbal fynbos in a Swartland Syrah? Does an old Barolo develop distinctive perfumed notes over time due to the white truffles growing nearby? I’ve heard winemakers make all these claims, some more credible than others.

Wild thyme grows among the rocks in some Cornas vineyards. Is that why I find that scent in some local wines? Don’t be so romantic, I told myself as I knocked on the door at Domaine Clape; it’s just the power of suggestion.

Olivier Clape answered, we shook hands, chatted awhile, then we took the tiny elevator to the cramped cellar underneath their house. We stood in a small, square room around a spittoon, surrounded by tall oval barrels, painted black with red rims. The bare bulb above us battled the gloom.

One wall is covered in old metal tools: filters, wrenches and other winemaking paraphernalia. Another has deep bins gouged out of it, more or less full of unlabelled bottles. Some glass still reflects the light, but most are being smothered by waves of thick mould, tufts of black, grey and white like a history teacher’s beard.

Before a single bottle is opened, I realise I can smell wine. Not just any wine – I can detect the unique aroma of Clape Cornas. It’s like a decomposing pine log in a damp forest, its blackened wood dotted with ceps and violet flowers, woodsmoke on the breeze. It’s unmistakable. It’s in the air. In the place. Is it possible that – like a vineyard – a cellar can imbue a wine with flavour, too?

Surely every barrel room has a unique microbiome. Put the seemingly smooth staves of an ancient barrel under a microscope and see a world within. One a bristling forest; another riven with great canyons; the third a bustling cityscape. Saccharomyces going about their daily business, Brettanomyces lurking in the back alleys.

Redirect the microscope to some concrete tanks. A polished patina reveals deep pores; delve inside to follow a network of cuboid caves, running water and mushrooms sprouting.

That’s an accurate description of Henri Bonneau’s cellar underneath his terraced property in Châteauneuf-du-Pape, as it happens. Successive caves connected by chiselled stairs hewn from the beige sandstone, some walls dusty black, others glistening wet. Was it these slimy subterranean conditions that imbued his wines with such depth and earthy fecundity? Ascend back to daylight and his backyard shelves have rows of spades, picks and secateurs, the table piled high with pumpkins and squashes.

Leaving Domaine Clape in Cornas, I crossed the road to visit Domaine Alain Voge. Lionel Fraisse took over the estate when Voge died, and Fraisse told me that he’s just employed a microbiologist to study their cellar’s resident microorganisms. Perhaps they will shed some light on the matter.

When we talk about terroir, and sense of place, it’s often a sweeping landscape that springs to mind. But perhaps that image should be more localized – on an individual building. House style, if you will.