Peter A. Thomas

“Vera’s ideas require a re-thinking of the evidence which has been previously interpreted as showing a dense forest. His view is that the open parkland explains why hazel, pedunculate oak and sessile oak (and other light-demanding species) have been well represented in pollen records for thousands of years, along with that of shade-tolerant species such as limes, elms, ash, common beech and hornbeam. In closed-canopy forests and forest reserves where large gaps are not present, oaks tend gradually to diminish because their seedlings, unlike those of the shade-tolerant trees, cannot grow at the low light levels present in the limited gaps which do form. He also contends that a partial explanation for the very high proportion of tree pollen dating from this period is that grazing may have been so efficient that production of grass pollen per unit area was greatly reduced. Svenning (2002) counters this by pointing out in a review of north-west Europe that in many studies non-tree pollen correlates well with other measures of openness such as beetle, snail and plant macrofossils and concludes that forested conditions were the norm with open vegetation being restricted to floodplains or poor soils (sandy or calcareous) and in the continental interior of north-west Europe.”
― Peter A. Thomas

“Having stressed the value of stable conditions, non-equilibrium mechanisms (such as variation in habitat across an area, or variation in time by periodic disturbance or gentle changes in local climate) can contribute to species co-existence by giving spatial or temporary advantage to different sets of species, again preventing one set from driving others out.”
― Peter A. Thomas, Ecology of Woodlands and Forests: Description, Dynamics and Diversity