@article{SandhageHofmannLinstaedterKindermannetal.2021,
  author    = {Sandhage-Hofmann, Alexandra and Linst{\"a}dter, Anja and Kindermann, Liana and Angombe, Simon and Amelung, Wulf},
  title     = {Conservation with elevated elephant densities sequesters carbon in soils despite losses of woody biomass},
  series = {Global change biology},
  volume    = {27},
  journal   = {Global change biology},
  number    = {19},
  publisher = {Blackwell Science},
  address   = {Oxford [u.a.]},
  issn      = {1354-1013},
  doi       = {10.1111/gcb.15779},
  pages     = {4601 -- 4614},
  year      = {2021},
  abstract  = {Nature conservation and restoration in terrestrial ecosystems is often focused on increasing the numbers of megafauna, expecting them to have positive impacts on ecological self-regulation processes and biodiversity. In sub-Saharan Africa, conservation efforts also aspire to protect and enhance biodiversity with particular focus on elephants. However, elephant browsing carries the risk of woody biomass losses. In this context, little is known about how increasing elephant numbers affects carbon stocks in soils, including the subsoils. We hypothesized that (1) increasing numbers of elephants reduce tree biomass, and thus the amount of C stored therein, resulting (2) in a loss of soil organic carbon (SOC). If true, a negative carbon footprint could limit the sustainability of elephant conservation from a global carbon perspective. To test these hypotheses, we selected plots of low, medium, and high elephant densities in two national parks and adjacent conservancies in the Namibian component of the Kavango Zambezi Transfrontier Area (KAZA), and quantified carbon storage in both woody vegetation and soils (1 m). Analyses were supplemented by the assessment of soil carbon isotopic composition. We found that increasing elephant densities resulted in a loss of tree carbon storage by 6.4 t ha(-1). However, and in contrast to our second hypothesis, SOC stocks increased by 4.7 t ha(-1) with increasing elephant densities. These higher SOC stocks were mainly found in the topsoil (0-30 cm) and were largely due to the formation of SOC from woody biomass. A second carbon input source into the soils was megaherbivore dung, which contributed with 0.02-0.323 t C ha(-1) year(-1) to ecosystem carbon storage in the low and high elephant density plots, respectively. Consequently, increasing elephant density does not necessarily lead to a negative C footprint, as soil carbon sequestration and transient C storage in dung almost compensate for losses in tree biomass.},
  language  = {en}
}
@article{SandhageHofmannAngombeKindermannetal.2022,
  author    = {Sandhage-Hofmann, Alexandra and Angombe, Simon and Kindermann, Liana and Linst{\"a}dter, Anja and M{\"o}rchen, Ramona},
  title     = {Conservation with elephants and agricultural intensification},
  series = {Geoderma : an international journal of soil science},
  volume    = {425},
  journal   = {Geoderma : an international journal of soil science},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {0016-7061},
  doi       = {10.1016/j.geoderma.2022.116009},
  pages     = {15},
  year      = {2022},
  abstract  = {Nature conservation is currently shaping many terrestrial ecosystems in Africa. This is particularly evident in Sub-Saharan Africa (SSA), where conservation is intended to recover wildlife populations, with special focus on elephants. Rising numbers of elephants induce woody biomass losses but increase soil organic carbon (SOC) stocks from decaying wood and dung. We hypothesized that these increases under wildlife conservation in SSA go along with rising contents of plant residues in SOC, traceable by the molecular markers lignin and n-alkanes. In contrast, agricultural intensification would reduce them due to lower C input and faster SOC turnover through tillage. To test this, we analyzed lignin by the CuO oxidation method and n-alkanes by fast pressurized solvent extraction in topsoils (0-10 cm) of Arenosols and corresponding plant samples (trees, grasses and crops). Sampling sites followed conservation gradients with low, medium and high elephant densities and intensification gradients with rangeland and cropland in the woodland savanna of the Namibian Zambezi Region. Patterns of lignin-derived phenols were retained in the soil, whereas n-alkanes showed shifts in chain lengths. n-Alkanes also showed no clear increase or decrease under conservation or intensification, respectively. Differently, lignin-derived phenols showed lower values under intensification than under conservation. Confirming our hypothesis, rising SOC contents with rising elephant densities (from 4.4 at low to 5.7 g kg(-1) SOC at high elephant densities) went along with an increasing accumulation of lignin-derived phenols (24.4-34.8 g kg(-1) VSCOC). This increase is associated with the input of woody debris to the soil, as indicated by V-units and carbon isotopes, modulated by clay and woody biomass. We conclude, that increasing input of woody residues into soil by browsing behaviour of elephants is an important mechanism for controlling SOC supply in the context of wildlife conservation and is traceable with lignin-derived phenols, but not with n-alkanes.},
  language  = {en}
}