Impact assessment of a super-typhoon on Hong Kong's secondary vegetation and recommendations for restoration of resilience in the forest succession

Sawaid Abbas, Janet E. Nichol (Corresponding Author), Gunter A. Fischer, Man Sing Wong (Corresponding Author), Syed M. Irteza

Research output: Journal article publicationJournal articleAcademic researchpeer-review

6 Citations (Scopus)

Abstract

Typhoons of varying intensities severely impact ecosystem functioning in tropical regions and their increasing frequencies and intensities due to global warming pose new challenges for effective forest restoration. This study examines the impact of a super-typhoon (Mangkhut) on the regenerating native secondary forest and exotic monocultural plantations in the degraded tropical landscape of Hong Kong. The super typhoon, which hit Hong Kong on 16 September 2018 lasted for 10 h (09:40–19:40) and was the most severe storm affecting Hong Kong over the past 100 years. Hong Kong's secondary forest is a mosaic of forest patches recovering through natural succession since 1945, and plantation stands of exotic monocultural species. We determine the loss in biomass by performing NDVI (Normalized Difference Vegetation Index) difference analysis using two Landsat-8 multispectral images acquired before and after the typhoon. This the assessment of typhoon impacts according to successional age group, structural stages of vegetation, landscape topography, and on stands of exotic plantations. Results indicate that hilltops, open shrubland and grassland were hard hit, especially on southwest and southeast facing slopes, and almost 90% of the landscape showed abnormal change. Patches of exotic monoculture plantation (Lophostemon confertus, Melaleuca quinquenervia, and Acacia confusa) were the most severely damaged by the typhoon, showing more than 25% decrease in NDVI, followed by young secondary forest. Field observations confirmed that in exotic plantations, almost the entire canopy was destroyed and there is no generation of young under story trees to replace those lost. The affected young forests and shrublands are mainly dominated by fast growing, soft wooded early successional species such as Mallotus paniculatus or Machilus chekiangensis as well as weak, multi-trunked, fungus infected, or other structurally deficient trees, which were uprooted or seriously damaged by typhoon gusts. The net effect of typhoons in Hong Kong's degraded landscape, appears to reinforce the arrested succession of dense, less diverse stands of weaker early successional species due to the absence of late and middle successional species and native dispersal agents. In order to obtain a stronger, more resilient forest, it would be necessary to enhance biodiversity by artificially planting a species mix, which resembles primary forests in the region. This could be achieved by thinning of young secondary forest followed by enhancement planting of pockets of high diversity forest.

Original languageEnglish
Article number107784
JournalAgricultural and Forest Meteorology
Volume280
DOIs
Publication statusPublished - 15 Jan 2020

Keywords

  • Hong Kong
  • Mangkhut
  • Monoculture plantations
  • NDVI
  • Remote sensing
  • Secondary forest
  • Tropical forest
  • Typhoon

ASJC Scopus subject areas

  • Forestry
  • Global and Planetary Change
  • Agronomy and Crop Science
  • Atmospheric Science

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