Tree species diversity and utilities in a contracting lowland hillside rainforest fragment in Central Vietnam

Abstract Background Within the highly bio-diverse ‘Northern Vietnam Lowland Rain Forests Ecoregion’ only small, and mostly highly modified forestlands persist within vast exotic-species plantations. The aim of this study was to elucidate vegetation patterns of a secondary hillside rainforest remnant (elevation 120–330 m, 76 ha) as an outcome of natural processes, and anthropogenic processes linked to changing forest values. Methods In the rainforest remnant tree species and various bio-physical parameters (relating to soils and terrain) were surveyed on forty 20 m × 20 m sized plots. The forest's vegetation patterns and tree diversity were analysed using dendrograms, canonical correspondence analysis, and other statistical tools. Results Forest tree species richness was high (172 in the survey, 94 per hectare), including many endemic species (>16%; some recently described). Vegetation patterns and diversity were largely explained by topography, with colline/sub-montane species present mainly along hillside ridges, and lowland/humid-tropical species predominant on lower slopes. Scarcity of high-value timber species reflected past logging, whereas abundance of light-demanding species, and species valued for fruits, provided evidence of human-aided forest restoration and ‘enrichment’ in terms of useful trees. Exhaustion of sought-after forest products, and decreasing appreciation of non-wood products concurred with further encroachment of exotic plantations in between 2010 and 2015. Regeneration of rare tree species was reduced probably due to forest isolation. Conclusions Despite long-term anthropogenic influences, remnant forests in the lowlands of Vietnam can harbor high plant biodiversity, including many endangered species. Various successive future changes (vanishing species, generalist dominance, and associated forest structural-qualitative changes) are, however, expected to occur in small forest fragments. Lowland forest biodiversity can only be maintained if forest fragments maintain a certain size and/or are connected via corridors to larger forest networks. Preservation of the forests may be fostered using new economic incentive schemes

Earliest Mississippian rugose corals of eastern Australia: post-disaster fauna across the Devonian-Carboniferous boundary?

The most earliest Mississippian rugose corals are post-disaster taxa occurring in a biosphere strongly modified by the crises associated with the Devonian-Carboniferous Boundary. In Western Europe, basal Tournaisian rugose corals belong to the genera Conilophyllum, Hebukophyllum and Kizilia. Conilophyllum and Hebukophyllum are either homeomorphs or close relatives of each other and are likely post-disaster fauna showing wide morphological plasticity but with an unknown origin. Kizilia is a Lazzarus taxon, known also from basal Tournaisian strata of China, that suddenly reappeared at the Devonian-Carboniferous Boundary being related to the mid-Devonian stringophyllids. The deeper basinal facies of Western Europe (Montagne Noire, Rhenish Mts, Thuringia, Upper Franconia) yield mostly small non-dissepimented solitary rugose corals, together with some dissempimented ones, amongst which are mostly long-ranging taxa. In N America, Vesiculophyllum, a genus very similar, and probably related, to Kizilia occurs together with non-dissepimented long-ranging corals. Like most of the basal Tournaisian dissepimented rugose corals, Cystodactylon orbum gen. et sp. nov. and Gudmania darumbalae gen. et sp. nov. from the basal Tournaisian of eastern Australia are interpreted as post-disaster fauna. Their origin is not understood to date and they seemingly left no descent in the Carboniferous. Their stratigraphic range is extremely limited as they so far are known only in small reefs at the base of the lower Tournaisian Gudman Formation in the type area