DOI: 10.5061/dryad.2280gb5sh
title: Large tree mortality census KNP (2006-2018)

description: Fire and elephant herbivory are major drivers of large tree mortality in
 savanna ecosystems. While the spatial variation of these agents is
 well-studied, less attention has been paid to how disturbance history
 influences mortality risk for trees over time. In a long-term cohort
 study, we examined how the sequence of fire- and elephant-induced damage
 influences mortality of trees, and determined whether risk of mortality is
 compounded with time. Data on over 2500 large trees were collected from 22
 transects in Kruger National Park, South Africa, in 2006, and trees were
 re-sampled in 2008, 2011, 2015, and 2018. Over the twelve year period, we
 recorded a cumulative death toll of 47.6% with an estimated annual
 mortality rate of 3-5% between 2006 and 2015, and a sharp increase to 8.8%
 in 2018. The main attributed agent of tree mortality was elephant damage,
 occurring either once or across multiple census periods. A classification
 tree (CT) analysis partitioned over different census periods showed that
 the probability of mortality for the ten most common species depended not
 only on the type and intensity of fire and elephant-induced damage, but
 also on the historical sequence of damage by these agents. In fact,
 elephant damage to the main stem incurred even up to 12 years earlier
 increases risk of mortality for large trees, especially in combination
 with fire damage. As expected, vulnerability to damage and risk of
 mortality varied between species, resulting in the potential for long-term
 changes in species composition at the landscape scale. Overall, this study
 highlights how multiple interacting agents cause emergent and lagging
 patterns of mortality risk for large trees in savanna ecosystems; a result
 that only becomes apparent through fine-scale long-term tracking of
 cohorts.
description: This dataset was used in the analysis of the causes of large tree
 mortality in Kruger National Park, South Africa, as presented in the
 manuscript titled, "The Importance of History in Understanding Large
 Tree Mortality in African Savannas". A cohort of
 large trees (&gt; 5m in height) was tracked across 22 transects in KNP
 between 2006 and 2018. The survival status of the trees and the type and
 severity of elephant and fire damage to individual trees was measured for
 the following census years: 2006, 2008, 2011, 2015 and 2018.
 The excel workbook contains metadata information, which is
 presented in the first tab of the workbook and explains each data field.
 The actual data is presented in the 'alldata' tab of the excel
 workbook and the codes for type and severity of elephant and fire damage
 are presented in the 'key' tab of the excel workbook.
 The study area, transect locations and sampling strategy are
 described in detail in Druce et al. (2008), Shannon et al. (2008) and
 Vanak et al. (2012). In the 2006 survey, the following
 were recorded: Tree characteristics: 1) species, 2)
 total height, 3) lower crown height, 4) crown diameter, 5) diameter of
 main stems, Landscape features: 1) landscape type
 (Gertenbach classification), 2) geology, 3) soil type, 4) slope position,
 5) distance to nearest water body, 6) distance to nearest river, 7)
 distance to nearest road, 8) elevation, 9) aspect In
 all surveys: Damage status: 1) Type and intensity of
 elephant damage, 2) Type and intensity of fire damage, 3) Incidences of
 mortality