Definition of "hectad"

Those taxa that show interesting distributions have been mapped and included here, their maps incorporating earlier records made by Laflin and others from 1958 to 1968 which had been based only on localities with hectad grid references.

1998, John Killick, Alan Roy Perry, Stan[ley Reginald John] Woodell, The Flora of Oxfordshire, [Newbury, Berkshire]: Pisces Publications

This comprises the proportion of each hectad covered by each of ten land-cover types: sea, coastal, arable, broadleaf forest, built-up, conifer forest, improved grassland, open water (rivers, lochs, etc.), semi-natural and upland. The temperature used was taken to be the annual temperature per hectad averaged over the period 1920–1999 […]

2007, Glenn Marion et al., “Towards an Integrated Approach to Stochastic Process-based Modelling: With Applications to Animal Behaviour and Spatio-temporal Spread”, in David L. Swain et al., editors, Redesigning Animal Agriculture: The Challenge of the 21st Century, Wallingford, Oxon., Cambridge, Mass.: CAB International, page 166

They took figures for the abundance of invasive weeds mapped according to the normal grid unit of the 'hectad', or 10 × 10 km square, and then looked at how abundant these species were mapped at a much finer scale – in 'tetrads', or 2 × 2 km squares, inside these hectads.

2010, Richard Mabey, Weeds: How Vagabond Plants Gatecrashed Civilisation and Changed the Way We Think about Nature, London: Profile Books

Certainly pampas grass made a slow start in the wild in this country [United Kingdom]; despite being grown here since 1848, it was recorded in only 21 hectads (10 x 10km squares) up to 1986, but is now recorded in 425.

2014 December 12, Ken Thompson, “Do plants have a gender? Most plants are hermaphrodite, but not all – and an interesting situation arises when only one sex is imported into the UK [print version: Alien plant species in search of a mate: Although most plants are hermaphrodite, some come in two distinct genders. So how does a single-sex community develop?, page W28]”, in The Daily Telegraph (Weekend)‎, archived from the original on 15 March 2016