Nature in the Wordsworth poems you ask about is something to be thoroughly experienced, studied, and contemplated. 

For Wordsworth, nature is an essential, not an extra or hobby.  Humans should attempt to be one with nature and cannot fully experience life without it. 

For instance, in "The World Is Too Much With Us," Wordsworth presents the idea that people spend too much time dealing with business and commerce.  He argues that he would rather suffer with an outdated philosophy and be aware of nature, than to follow a contemporary, up-to-date philosophy, and not be aware of nature.  Nature, then, is more important to a human than philosophy or religion, according to Wordsworth.

In "Tintern Abbey," Wordsworth demonstrates how he experiences nature, contemplates it over a long period of time, and learns from it in the process.  The poem actually highlights his writing process.  He experiences the area around Tintern Abbey five years previous to the poem, contemplates it during those five years, returns to the area, and writes about both visits.  This demonstrates Wordsworth's famous idea that poetry is written during periods of reflection and contemplation, after nature is experienced. 

Nature is an essential to Wordsworth in these poems.