Donald Urquhart's exhibition Fields, which has just finished its run at Kilkenny's Butler Gallery and opens next week at the Orchard Gallery in Derry, is about landscape. That is, it comes across more as a series of speculations and propositions about the representation of landscape than as a series of landscapes per se. Its tone is one of cautious, sceptical inquiry about how we might approach landscape in making art now and, as such, it is continually engaging and stimulating.

A range of approaches are manifest throughout. Oil glazes are brushed over photographic prints of cloudy skies in Washed Sky. Close-up photographic views of several kinds of broken terrain - Burren limestone, slate, an Icelandic plain, the surface of the moon - are rendered in monochrome, in sketchy line or quasi-photographic tone. It's all rigorously done, with an abiding austerity of means and effects.

The presence of water is vividly evoked in a beautiful photographic floor-piece that is strikingly reminiscent of David Hockney's Paper Pools paintings. Everywhere images are processed, interrupted and contained, presumably to convey a sense of the pervasive management of landscape and its meanings. Finally, Urquhart gives up on images altogether and resorts to language. Three small blue canvases each feature a word descriptive of landscape, in neat script: still, calm, quiet. Another features the repeated, handwritten sentence: "It was a beautiful place". It is as though the question of visual representation has become too fraught, too problematic.

Urquhart is Scottish, and Scotland shares with Ireland landscapes of spectacular natural beauty that have become deeply politicised by virtue of their history of ownership, bitter conflict and national symbolism. There, as much as anywhere, the notion of a natural realm, a wilderness untouched by human concerns seems both tantalisingly possible and simultaneously denied by the facts of history.

Francis McKee's catalogue essay emphasises the tension between randomness and order in Urquhart's work. That is, the rationalising gaze of ownership and exploitation is set against untameable randomness of nature in the landscape . . . " The apogee of an orderly view is represented by the lunar landscape, derived from some of the 32,000 or so images recorded by Apollo astronauts on missions in the late 1960s and early 1970s. This triumph of mathematical calculation stands for the quantification of nature.

It could be that there is an underlying implication here that a quantitative view negates an appreciation of nature in and for itself. Certainly, Urquhart continually emphasises the way the landscape is pervasively mediated. He interrupts an already heavily formalised image of the Burren rockscape, for example, with a series of arbitrary vertical bands, as though suggesting that our mode of perception is itself a construct on the landscape.

An expanse of blank white across the base of the large Lunar Field (not exhibited at the Butler) recalls the Belgian painter Luc Tymans's practice of depicting the blank surrounds of magazine images he uses as sources. In both cases we are being reminded that what we are looking at comes second or third hand, that we are inescapably remote from the "real".

In fact, it's clear that nearly everything about Urquhart's work reinforces this point. Nearly, but not quite. McKee comments on the almost paradoxical sensual beauty of the work. There is a feeling that a residual richness gets through even the most stringent attempts to rationalise it out of existence. This is strikingly apparent in the watery Noted Pool. The almost tangible impression of sun-touched flowing water shimmers invitingly against the slate bedrock. It is an illusion that emerges from a composite of inkjet prints on textured paper, but a compelling one.

Less compelling is the implied opposition between order and beauty. McKee mentions several times what could be called the elusive randomness of nature, its unclassifiable chaos and mutability. Against this we have human efforts to enclose it in a deterministic, orderly system. Yet, arguably, that is simply not to comprehend what understanding natural processes actually means. The "anonymous section of rocky terrain", apparently "randomised by geological events, climate and the erosion of time" is random and anonymous in a certain sense only. It is, in all likelihood, perfectly intelligible to a geologist. The randomness fits into a pattern, but to understand the pattern is not to rob the landscape of its randomness, or its beauty.

You get the feeling that Urquhart is instinctively drawn to landscapes without boundaries, that he loves the anomalous and wild. He is by no means only a gallery artist: he has done a great deal of work in outdoor settings, much of it in natural, or close to natural settings. One of his current projects, Lines/Planes (Larus/Cygnus), is a commission for Sligo County Council to be sited at four points of the River Garavogue in Sligo. It's encouraging to know that the analytical quality of his work doesn't preclude the contact with the landscape that, the work in Fields suggests, is inevitably problematic.

Donald Urquhart's Fields is at the Orchard Gallery, Derry from November 24th to December 22nd.