@article{fdi:010060223,
  title = {{P}ositive versus negative environmental impacts of tree encroachment in {S}outh {A}frica},
  author = {{G}rellier, {S}. and {W}ard, {D}. and {J}aneau, {J}ean-{L}ouis and {P}odwojewski, {P}ascal and {L}orentz, {S}. and {A}bbadie, {L}uc and {V}alentin, {C}hristian and {B}arot, {S}{\'e}bastien},
  editor = {},
  language = {{ENG}},
  abstract = {{W}oody plant encroachment in grasslands is a worldwide phenomenon. {D}espite many studies, the consequences of woody plant encroachment on sub-canopy vegetation and soil properties are still unclear. {T}o better understand the impacts of trees on grassland properties we examined the following questions using a mountainous sub-tropical grassland of {S}outh {A}frica encroached by an indigenous tree, {A}cacia sieberiana as a case study: (1) {D}o trees increase sub-canopy herbaceous diversity, quality and biomass and soil nitrogen content? (2) {D}o large trees have a stronger effect than medium-sized trees on grass and soil properties? (3) {D}oes the impact of trees change with the presence of livestock and position of trees in a catena? {W}e studied grass and non-graminoid species diversity and biomass, grass quality and soil properties during the wet season of 2009. {N}itrogen in grass leaves, soil cation exchange capacity and calcium and magnesium ion concentrations in the soil increased under tall {A}cacia versus open areas. {M}edium-sized {A}cacia decreased the gross energy content, digestibility and neutral detergent fibre of grasses but increased the species richness of non-graminoids. {T}all and medium {A}cacia trees were associated with the presence of {S}enecio inaequidens, an indigenous species that is toxic to horses and cattle. {T}he presence of livestock resulted in a decrease in herbaceous root biomass and an increase in soil carbon and leaf biomass of grass under {A}cacia. {T}ree position in the catena did not modify the impact of trees on the herbaceous layer and soil properties. {F}or management of livestock we recommend retaining tall {A}cacia trees and partially removing medium-sized {A}cacia trees because the latter had negative effects on grass quality.},
  keywords = {{PATURAGE} ; {INVASION} ; {ARBUSTE} ; {IMPACT} {SUR} {L}'{ENVIRONNEMENT} ; {SAVANE} ;  {DYNAMIQUE} {DE} {VEGETATION} ; {COMPETITION} {INTERSPECIFIQUE} ; {DIVERSITE} {SPECIFIQUE} ; {BIOMASSE} ; {HERBACEE} ; {PLANTE} {FOURRAGERE} ; {QUALITE} ; {STRATE} {HERBACEE} ; {SOL} ; {PROPRIETE} {PHYSICOCHIMIQUE} ; {AZOTE} ; {CARBONE} ; {ZONE} {DE} {MONTAGNE} ; {AFRIQUE} {DU} {SUD} ; {KWAZULU} ; {POTSHINI}},
  booktitle = {},
  journal = {{A}cta {O}ecologica},
  volume = {53},
  numero = {},
  pages = {1--10},
  ISSN = {1146-609{X}},
  year = {2013},
  DOI = {10.1016/j.actao.2013.08.002},
  URL = {https://www.documentation.ird.fr/hor/fdi:010060223},
}