Conservation assessment and spatial distribution of endemic orchids in Sabah, Borneo

Orchids are among the most threatened plants due to habitat loss and illegal harvesting for horticultural demands. Sabah is a centre of orchid diversity, with approximately 1300 species of which 250 orchid taxa are endemic to Sabah. In this study, we conducted an IUCN Red List assessment on 136 endemic species and used Maximum Entropy (MaxEnt) to develop species distribution models for 47 species. The species distribution models were developed using presence-only data and six environmental predictors. The accuracy of the models were assessed using the area under the curve (AUC) and models with an AUC of higher than 0.8 stacked together to produce a species richness heatmap. We found that 83% of the researched species were threatened, of which 14 species were assessed to be Critically Endangered, eight species as Endangered and 93 species as Vulnerable. The heatmap shows that all of the species occurred within the Totally Protected Area (TPA) network in western Sabah. The heatmap highlighted the mid-altitude areas adjacent to the Kinabalu and Crocker Range parks and Ulu Sipitang regions as areas with a high species richness that were outside the TPA network. These areas are also important for the conservation of the majority of the species assessed as Critically Endangered and Endangered. Urgent conservation actions are needed to protect these species from extinction. The results from this work will be used as part of an intensive conservation action plan for threatened endemic orchids of Sabah and used to identify important plant areas currently not within the existing TPA networ

Ecology of nickel hyperaccumulator plants from ultramafic soils in Sabah (Malaysia)

Sabah (Malaysia) has one of the largest surface expressions of ultramafic rocks on Earth and in parallel hosts one of the most species-rich floras. Despite the extensive knowledge of the botanical diversity and the chemistry of these substrates, until recently the records for nickel (Ni) hyperaccumulator plants in the area have been scant. Recent intensive screening has resulted in 19 new records, adding to the 5 previously known from Sabah. The results of this study indicate that most Ni hyperaccumulator plants in Sabah are restricted to successional habitats (ridges, river banks, secondary vegetation) at elevations < 1200 m a.s.l. Moreover, Ni hyperaccumulators are locally common both in terms of number of individuals and relative number of species. Nickel hyperaccumulation occurs most frequently in the Order Malpighiales (families Dichapetalaceae, Phyllanthaceae, Salicaceae, Violaceae), and is particularly common in the Phyllanthaceae (genera Phyllanthus, Glochidion). Comparison of soil chemistry with elements accumulated in hyperaccumulator foliage showed significant correlation between soil exchangeable Ca, K, P and the foliar concentrations of these elements. No direct relationship was found between soil Ni and foliar Ni, although foliar Ni was negatively correlated with soil pH. Nickel hyperaccumulation has been hypothesised to fulfil herbivory protection functions, but extensive herbivory-induced leaf damage on Ni hyperaccumulators in Sabah was common, and specialist (Ni-tolerant) insect herbivores were found on several species in this study. The identification of Ni hyperaccumulators is necessary to facilitate their conservation and potential future utilisation in Ni phytomining

Brevi annotazioni sparse (a est di Berlino)

Localized ultramafic outcrops in Kinabalu Park (encompassing Mount Kinabalu and Mount Tambuyukon) in Sabah (Malaysia) are known for high levels of plant diversity and endemism, which have been stimulated by extreme soil chemistry and biogeographic factors, such as isolation. Characteristic of these outcrops are edaphic endemics of insectivorous pitcher plants from the Nepenthaceae-family including Nepenthes burbidgeae, N. edwardsiana, N. macrovulgaris, N. rajah and N. villosa, all of which (except N. macrovulgaris) are confined solely to the protected area of Kinabalu Park. Although the various aspects of plant taxonomy and nutrition of this genus have been extensively studied, the habitat of these rare species has to date not been studied in detail. It was hypothesized that while the Nepenthes of Mount Kinabalu and Mount Tambuyukon are excluders of excess trace elements, soil chemistry is nevertheless a major driver for creating the specific habitats in which ultramafic edaphic endemic Nepenthes occur, and that this is reflected in vegetation physiognomy and co-occurring species composition as well as in the foliar chemistry of Nepenthes. The results show that the characteristics of the physical environment and soil chemistry 'induces' a vegetation physiognomy that varies among sites and produces a series of different niches that are colonised by different Nepenthes-species. Although other plant species associated with these niches do not directly influence the distributions of the Nepenthes-species, some are characteristic. The unusual ultramafic soil chemistry is not reflected in the foliar chemistry of Nepenthes and they appear to be 'Excluders' of potentially toxic soil trace element concentrations. The populations of Nepenthes burbidgeae, N. edwardsiana, N, rajah, N. villosa are small (in particular, N. burbidgeae) and these species are thus likely to be vulnerable to the potential effects of climate change-induced drought and fire

Biogeochemical cycling of nickel and nutrients in a natural high-density stand of the hyperaccumulator Phyllanthus rufuschaneyi in Sabah, Malaysia

The extend of biogeochemical cycling of nickel (Ni) by tropical hyperaccumulator plants in their native habitat is largely unknown, although these unusual plants are suspected to play a major role in the recycling of this element in ultramafic ecosystems. In this study, we have assessed the biogeochemical cycling of Ni (and other elements, including mineral nutrients) by a tropical Ni hyperaccumulator plant, i.e., Phyllanthus rufuschaneyi, which is one of the most promising species for tropical Ni agromining. The study site was a young secondary forest in Sabah (Malaysia) where Phyllanthus rufuschaneyi occurs as the dominant species on an ultramafic Cambisol. For 2 years, we monitored a 100-m2 plot and collected information on weather, biomass increase, soil fertility, water fluxes to the soil and litter fluxes for a wide range of elements, including Ni. The Ni cycle is mainly driven by internal fluxes, notably the degradation and recycling of Ni-rich litter. Over the period of investigation, the Ni litter flux corresponded to the total Ni stock of the litter (5.2 g m−2 year−1). The results further show that Ni turnover varies significantly with the accumulation properties of the plant cover. This points to the major influence of Ni hyperaccumulator plants in building up Ni available stocks in the topsoils, as has also been shown in temperate ultramafic systems. Litterfall and throughfall contribute substantially to the cycling of phosphorus, sulphur and potassium in this ecosystem, with throughfall contributing 2-, 220- and 20-fold higher to the respective nutrient fluxes relative to litterfall. The magnesium:calcium ratio far exceeded 1 in the soil, but was < 1 in the leaves of Phyllanthus rufuschaneyi. The insights from this study should be taken into account when designing tropical agromining operations; as Ni stocks could be more labile than initially thought. The removal of Ni- and nutrients-rich biomass will likely affect available Ni (and major nutrients) for the next cropping seasons, and requires sustainable fertilisation, to be utilized to replenish depleted major nutrients. These findings also have major ecological implications

Improving tropical nickel agromining crop systems : the effects of chemical and organic fertilisation on nickel yield

Abstract: Aims The agronomy of tropical ‘metal crops’ had not yet been tested until a recent pot trial was undertaken to test the growth and nickel (Ni) yield of two promising Ni ‘metal crops’ (Phyllanthus rufuschaneyi and Rinorea cf. bengalensis) from Sabah, Malaysia. The present study investigates the growth and Ni yield in P. rufuschaneyi in response to inorganic and organic fertilisation under field conditions. Methods: A two-year field experiment was undertaken on an ultramafic Cambisol in Sabah. Two experiments were set up with different types of fertilisers, either organic or inorganic. Ten 9-m2 plots were amended with either NPK (370 kg ha−1) or N (120 kg ha−1) fertilisation and were monitored during the first year. Another experiment with 25-m2 plots was set up to test three treatments of organic amendment (0, 1 or 2 kg m−2 of shredded P. rufuschaneyi biomass). Results: The results show that despite considerable variability, Ni concentration was generally lower in plant shoots amended with N only (i.e. urea). However, treatments showed no statistical effect on plant biomass and Ni yield in the short-term, even though organic treatments had a strong positive effect on the availability of Ni. Conclusion: The short-term effects of inorganic and organic treatments on Ni yield of the tropical ‘metal crop’ Phyllanthus rufuschaneyi were not apparent (75 kg Ni ha−1 yr−1). The field trials are ongoing to assess long-term effects. The preliminary results suggest that with appropriate agronomic systems and plant breeding, the Ni yield could be substantially increased

Soil amendments affecting nickel uptake and growth performance of tropical ‘metal crops’ used for agromining

Ultramafic soils are usually marginal in macronutrients (nitrogen (N), phosphorus (P), potassium (K) and calcium (Ca)) for growth of crop plants. Commercial nickel (Ni) agromining is dependent on attaining high yield and high Ni concentration in harvestable biomass of Ni hyperaccumulator species. We previously reported on the biomass responses of two promising tropical ‘metal crops’ (Phyllanthus rufuschaneyi and Rinorea cf. bengalensis) to rates of N, P, and K fertilisers. Calcium, sulphur (S) and organic matter amendments have varied effects on the biomass production and Ni uptake in temperate Ni hyperaccumulator species used in agromining, but the trends in tropical ‘metal crops’ are not reported to-date. We investigated the effects of these amendments on the growth performance and the Ni (and other elements) uptake in P. rufuschaneyi and R. cf. bengalensis The experiments consisted of a large 12-month randomised growth trial in large pots in Sabah (Malaysia) using ultramafic soils under different treatment levels of soluble Ca and S, and organic matter amendments. We found that Ca and S additions had no significant effects on the growth of P. rufuschaneyi and R. cf. bengalensis. Organic matter amendments had strong positive effect on the growth of R. cf. bengalensis (p < 0.05), but we recorded significant negative growth response in P. rufuschaneyi. Whereas Ca and S additions improved the Ni uptake in these species, organic matter amendments significantly reduced the shoot Ni concentrations in both species. Our findings indicate that Ca and S additions are important in the agronomy of tropical ‘metal crops’ to be used in economic Ni agromining, but organic matter amendments may not be useful

Variation in the ionome of tropical ‘metal crops’ in response to soil potassium availability

Background and Aims: In tropical ultramafic soils, potassium (K) is typically the most growth limiting nutrient. However, tropical nickel (Ni) hyperaccumulator plants, including Phyllanthus rufuschaneyi and Rinorea cf. bengalensis (which are ‘metal crops’ used in agromining) from Malaysia, have unusually high K shoot accumulation compared to other species, despite naturally growing on severely K-impoverished ultramafic soils. This study aimed to establish the response to soil K availability in relation to uptake of K and other elements in the roots and shoots of P. rufuschaneyi and R. cf. bengalensis. Methodology: We undertook an experiment in which soluble K was dosed to ultramafic soil in pots with P. rufuschaneyi and R. cf. bengalensis in Sabah (Malaysia). Results: The results show that root K concentrations increased markedly as the soil K availability increased by 35-fold, whilst the corresponding effect on K accumulation in the shoots of P. rufuschaneyi and R. cf. bengalensis was not significantly different in relation to soil K dosing. Observed divergent responses between root and shoot K accumulation in these species suggests a separate genetic control of K uptake and xylem loading in P. rufuschaneyi and R. cf. bengalensis. Conclusion: The tight control of root-to-shoot K translocation and constrained K accumulation in shoots under a soil K gradient is likely an adaptive mechanism to the evolution of these species to grow in highly nutrient-impoverished ultramafic soils. This study provides information that will be useful for better nutrient management of tropical Ni metal farms that use K-efficient Ni ‘metal crops’

Growth effects in tropical nickel-agromining ‘metal crops' in response to&nbsp;nutrient dosing

Agromining is an emerging technology that utilizes selected ‘metal crops' (= hyperaccumulator plants) to extract valuable target metals from unconventional resources for profit from mineralised soils. Growth characteristics, shoot metal concentrations, and agrominable locations are important considerations in economic agromining. Globally, the greatest potential for nickel (Ni) agromining exists in the tropics. However, the agronomic systems of tropical ‘metal crops' have not been previously tested. Furthermore, it is currently unknown whether nutrient dosing of prospective tropical agromining Ni ‘metal crops’ could possibly cause a shoot Ni-dilution effect which may ultimately limit economically viable Ni yields.We undertook a pioneering study on Ni uptake and growth responses to nutrient dosing in two promising tropical ‘metal crops' (Phyllanthus rufuschaneyi and Rinorea cf. bengalensis). The experiment consisted of a large randomised block growth trial in large pots over 12 months in Sabah (Malaysia). At 3-month intervals, the plants were exposed to soluble treatments that altered available concentrations of nitrogen (N), phosphorus (P), and potassium (K). We found strong positive growth responses to N and P additions in P. rufuschaneyi, whereas K additions had negative growth effects. In R. cf. bengalensis, all treatments had positive growth effects. The increases in biomass in response to nutrient dosing did not significantly reduce shoot Ni concentrations in both species, with the exception of N addition in P. rufuschaneyi. This study reveals that Ni uptake and growth responses to nutrient dosing are species-dependent, primarily influenced by the ecophysiology of the species. Inorganic fertilization could possibly be an important component of the management of local ‘metal crops' to be used in viable commercial agromining in the tropics, but this needs to be tested in the field with different formulations of N, P, and K

Phyllanthus rufuschaneyi: a new nickel hyperaccumulator from Sabah (Borneo Island) with potential for tropical agromining

Nickel hyperaccumulator plants are of much interest for their evolution and unique ecophysiology, and also for potential applications in agromining-a novel technology that uses plants to extract valuable metals from soil. The majority of nickel hyperaccumulators are known from ultramafic soils in tropical regions (Cuba, New Caledonia and Southeast Asia), and one genus, Phyllanthus (Phyllanthaceae), is globally the most represented taxonomic entity. A number of tropical Phyllanthus-species have the potential to be used as 'metal crops' in agromining operations mainly because of their ease in cultivation and their ability to attain high nickel concentrations and biomass yields.One of the most promising species globally for agromining, is the here newly described species Phyllanthus rufuschaneyi. This species can be classified in subgenus Gomphidium on account of its staminate nectar disc and pistillate entire style and represents the most western species of this diverse group. The flower structure indicates that this species is probably pollinated by Epicephala moths.Phyllanthus rufuschaneyi is an extremely rare taxon in the wild, restricted to Lompoyou Hill near Kinabalu Park in Sabah, Malaysia. Its utilization in agromining will be a mechanism for conservation of the taxon, and highlights the importance of habitat and germplasm preservation if rare species are to be used in novel green technologies

Contrasting phosphorus (P) accumulation in response to soil P availability in ‘metal crops’ from P-impoverished soils

Background and aims: Phosphorus is one of the major nutrients that directly or indirectly affects all aspects of plant growth. Tropical nickel hyperaccumulators, including Phyllanthus rufuschaneyi and Rinorea cf. bengalensis from Borneo Island (in the Malaysian state of Sabah), have evolved to grow in extremely P-impoverished ultramafic soils. This study aimed to establish the response of the root and shoot ionome of these two agromining ‘metal crops’ to soil P availability. Methods: We undertook a soil P dosing trial on P. rufuschaneyi and R. cf. bengalensis in Sabah (Malaysia) over a period of 12 months. We measured the elemental concentrations in the soil solution and roots, as well as in the developed and developing stems and leaves. Results: The results show that root and shoot P accumulation increased markedly as soil P availability increased by 80-fold in P. rufuschaneyi, whereas R. cf. bengalensis did not increase as strongly to P supply, despite a 135-fold increase in soil solution P. The contrasting observations on the root and shoot P accumulation patterns in these species suggests distinct P acquisition strategies in these species. The non-responsiveness of R. cf. bengalensis to increasing soil P availability may be related to its possible association with mycorrhizal fungi. Conclusion: The findings of this study reveal the complexities of phosphate uptake, transport and accumulation in these ‘metal crops’. This information is essential to develop appropriate nutrient management in nickel agromining operations