The vegetation grown on grasscretes along channelized rivers have been regularly mown in Hong Kong. However, no baseline information on the relationship between different mowing regimes and the biodiversity of such riverbed vegetation is available. We therefore carried out a manipulative experiment along a channelized river to test the effect of mowing frequency and intensity on the abundance and species richness of terrestrial biodiversity. We conducted point counts and transect counts to survey birds, butterflies and Odonates, night surveys for amphibians and reptiles, quadrat surveys for vegetation and sweep net and pan traps for other macroinvertebrates. The results from Generalized Linear Mixed Models (GLMMs) showed a taxon-specific effect of mowing regime. Bird species richness was significantly suppressed in plots mown with high frequency. Both butterfly abundance and species richness were greatly enhanced by low intensity and low frequency mowing. Odonate abundance, and the abundance and species richness of other macroinvertebrates remained high whenever a portion of vegetation was retained as refuge. Amphibians and reptiles did not prefer to utilize the vegetation grown on grasscretes, and thus showed no impact from different mowing regimes. The overall species richness of vegetation was not affected by mowing regimes, but the domination of tall invasive Brachiaria mutica was suppressed by any mowing activity. To cater for the need of most taxa, we propose a mosaic mowing regime, in which most parts along the channelized river could be mown infrequently to 600 mm tall while some of the patches remain unmown.

Ecological studies conducted on lucanids in Asia are limited, resulting in considerable knowledge gaps in the fundamental ecology of these charismatic species (e.g. larval substrate associations), despite their potential importance in wood decomposition. We conducted 25 transect surveys in secondary forest sites in Hong Kong and sampled wood parameters and site‐level wood availability data to test whether these habitat features significantly affected abundance or occurrence of lucanids. Out of 412 wood fragments sampled, we found two species: Prosopocoilus oweni was broadly distributed across sites (but still uncommon at the level of wood fragments occurring in 6.07%) while Nigidius sinicus was comparatively rarer (occurring in 0.73% of examined wood fragments). The dominant species P. oweni was more likely to appear in wood fragments in later decay stages and can be classified as a secondary forest generalist with respect to wood resource utilisation. The surveys failed to detect four additional lucanid species known in Hong Kong (Neolucanus sinicus, E. gracilis, P. biplagiatus, and Aegus chelifer) potentially because of their rarity or usage of other habitats or microhabitats. Protection of existing secondary forests in Hong Kong is recommended to secure supply of suitable habitat and resources. Results obtained by standardised surveys can furthermore serve as a baseline for future assessment of lucanid population change. This study provides ecological insights into lucanids within secondary forest ecosystems of subtropical and tropical Asia.