Data from: Cross-sectional versus longitudinal research: a case study of trees with hollows and marsupials in Australian forests

How different are insights based on cross-sectional studies from those of
longitudinal investigations? We addressed this question using a detailed
case study encompassing a rare suite of inter-connected cross-sectional
and longitudinal investigations that have spanned the past two decades and
included work on (1) the decay and collapse of large cavity forest trees
(termed trees with hollows), (2) populations of a suite of species of
arboreal marsupials which are reliant on trees with hollows as nesting and
denning sites, and (3) relationships between the abundance, type and
condition of trees with hollows and the presence, abundance and species
richness of these animals. Our case study was from the montane ash
eucalypt forests of the Central Highlands of Victoria, south-eastern
Australia. Our longitudinal studies led to new insights that either would
not have been possible from a cross-sectional study or which were
unexpected because they did not conform, or only partially conformed, to
postulated responses made at the outset based on the results of earlier
research. These new insights included (1) a substantial slowing in rates
of tree fall between 1997 and 2006 which were significantly lower than
predicted from earlier data gathered between 1983 and 1993, (2) no
evidence for a decline in populations of almost all species of arboreal
marsupials between 1997 and 2007, despite the loss of nearly 14% of the
measured population of trees with hollows in that time, (3) changes in
nest tree selection by some species of arboreal marsupials in response to
these changes in hollow availability, (4) concentration effects, in which
populations of animals used the declining tree hollow resource more
intensively, and (5) evidence for significant rainfall effects on temporal
changes in animal abundance. Our case study underscored the additional
ecological insights that can be generated from longitudinal studies,
including how relationships between biota and their habitat can change
over time. Understanding these temporal changes is essential for informed
forest management and biodiversity conservation and points towards the
need for greater use of longitudinal datasets in ecology.