Too much of a good thing: phosphorus over-fertilisation in rehabilitated landscapes of high biodiversity value

Fertilisers supply essential nutrients lacking in post-mining substrates in nearly all terrestrial rehabilitation schemes. Regulators typically require the rapid revegetation of post-mining lands as an indicator of early rehabilitation success, mapping to perceived pathways of successful ecosystem recovery. However, we will show how this approach can lead to poorer outcomes in terms of vegetation composition and potentially, long-term issues in ecosystem biogeochemistry. Many mines exist in remote areas and on highly weathered, ancient, nutrient poor soils. Examples of these are the Fynbos of South Africa, the western and northern forests of Australia, the Campos rupestres of South America, and many tropical areas. Typically, restoration requirements in these areas require the return of a native vegetation community that existed prior to mining. This is particularly common for surface strip mining where large areas of land are cleared of vegetation annually. In this paper, we show how, where, and why over-fertilisation can occur. Based on examples from western and northern Australia, we demonstrate that the application of phosphoruscontaining fertilisers to these nutrient depleted soils can result in long-term elevated soil phosphorus, with species-specific negative impacts on plant health and growth. We show the rehabilitation benefits that can be gained by judicious fertilisation in terms of vegetation community structure and ecosystem development. Finally, to assess where these findings may have wider applicability, we identify further global regions with nutrient depleted soils, high plant diversity, and current or prospective strip mining operations

Enduring effects of large legumes and phosphorus fertiliser on jarrah forest restoration 15 years after bauxite mining

Restoring nutrients lost in the mining process and re-establishing nutrient-cycling are often key goals of mine restoration. One common strategy to facilitate these goals is to seed fast-growing legumes combined with one application of P-fertiliser to maximise legume growth and increase soil-N. However, the longer term effects of this strategy have received little attention. Here we report the results of a 15-year-old experiment that was established to test the effects of fertiliser-P application and seeding large understorey legumes, both singly and in combination, on jarrah forest restoration after bauxite mining. Fifteen years after the establishment of this experiment, the majority of the seeded legumes had senesced, with total legume cover having declined significantly compared with results of the same experiment at 5-years-of-age. Yet, despite the legumes having senesced there were still negative effects of both large legumes and P-fertiliser on species richness and abundance of non-leguminous understorey species. These negative effects may be mediated by the persistent effects of legume competition that was evident at 5 years and the accumulation of significant quantities of leaf litter and fine woody debris in the large legume × P-addition treatments. Compared with the 0 kg P ha−1 treatment, application of 20 kg P ha−1 significantly increased jarrah tree growth, but there was no additional benefit of 80 kg P ha−1. These data suggest that moderation of P-fertiliser and large understorey legumes could maximise understorey cover, tree growth and understorey species richness, and therefore simultaneously address multiple key restoration goals

Canary in the coal mine: lessons from the Jarrah Forest suggest long-term negative effects of phosphorus fertilizer on biodiverse restoration after surface mining

Despite nutrient enrichment having widely reported negative impacts on biodiversity, fertilizer is routinely applied in post mining restoration to enhance plant growth and establishment. Focusing on surface mine restoration (predominately bauxite and mineral sands), we outline the long-term negative impacts of fertilizer, particularly phosphorus fertilizer, on plant community composition, species richness, fire fuel loads, and belowground impacts on nutrient-cycling. We draw from extensive research in south-western Australia and further afield, noting the geographical coincidence of surface mining, phosphorus impoverished soil and high plant biodiversity. We highlight the trade-offs between rapid plant-growth under fertilisation and the longer-term effects on plant communities and diversity. We note that the initial growth benefits of fertilisation may not persist in water-limited environments: growth of unfertilised forests can eventually match that of fertilised forest, throwing doubt on the premise that fertilisation is necessary at all

The where, when and what of phosphorus fertilisation for seedling establishment in a biodiverse jarrah forest restoration after bauxite mining in Western Australia

Fertiliser application to restore nutrients lost in the mining process and facilitate early plant establishment and growth is a key step in the restoration of sites disturbed by mining. However, few studies have investigated the effects of different fertiliser types and application methods on mine restoration outcomes, especially in highly biodiverse ecosystems such as the jarrah forest. This forest is a unique, floristically diverse landscape with species adapted to growth on highly weathered phosphorus impoverished Ferralsol. In this study we investigated the effect of fertiliser type (rock phosphate, single superphosphate, and an NPK fertiliser), application method (top-dressed versus incorporated), and the timing of application (winter vs. summer) on the trajectory of jarrah (Eucalyptus marginata) forest restoration following bauxite mining compared to an unfertilised control. All fertilised soil had elevated Colwell-P concentrations (bar rock phosphate) and had considerably less N than found in the native forest, even after N fertilisation. Fertiliser incorporation resulted in a more even distribution of P down the soil profile and increased overall plant growth (as assessed by percentage cover) compared with either top-dressed fertiliser application and no fertiliser, potentially offering better erosion control. In contrast, native species richness was highest in the zero fertiliser and NPK treatments and lowest in the phosphorus incorporation treatments. On average, unfertilised plots had 10 more native species per plot than those fertilised with P only. Fertiliser application also reduced the abundance and cover of Bossiaea ornata and Lomandra spp., both of which are small slow-growing understorey taxa. In contrast, the legume Acacia celastrifolia exhibited a vigorous growth response to fertiliser, with growth being greatest when P (either rock phosphate or SSP) was incorporated. These data suggest that P fertiliser incorporation is a potential strategy to both maximise early plant growth and cover and increase the efficiency of P application. However, if the goal of restoration is to maximise diversity then moderation in P application and using fertilisers that also contain N and K may be appropriate

Phosphorus supply affects seedling growth of mycorrhizal but not cluster-root forming jarrah-forest species

Aims Fertiliser is often used to kick-start ecological restoration despite growing evidence of the potentially negative impacts on plant diversity. Jarrah (Eucalyptus marginata) forest species growing on nutrient (especially phosphorus) impoverished soils in southwestern Australia have a suite of adaptations for phosphorus (P) acquisition, including the formation of cluster roots, and associations with mycorrhizal fungi. Here we investigated how escalating P supply, along with a stoichiometric adjustment of nitrogen (N) supply, impacted the growth and nutrition of a wide range of jarrah forest seedlings. Methods In a pot experiment, we measured seedling biomass and nutritional responses of 12 jarrah forest species to a gradient of P supply in relation to N supply, and for the mycorrhizal species, inoculation with arbuscular mycorrhizal fungi. Results Three cluster-root forming species did not respond to increasing P, probably because they were reliant on seed P. Generally, mycorrhizal species showed a positive biomass response to increasing P when N was available. Mycorrhizas benefited seedling growth at low P (9 mg P added per kg of jarrah forest soil) when N was also available, and were parasitic to seedling growth at high P (243 mg P/ kg soil) without additional N. Conclusions These results highlight importance of P and N supply in determining the nature of the symbiosis between plants and mycorrhizal fungi. Since P supply has the potential to reduce plant growth, for a range of species, our results suggest careful consideration of fertiliser amounts for ecological restoration of ecosystems adapted to nutrient poor soils

Nutrient enrichment diminishes plant diversity and density, and alters long-term ecological trajectories, in a biodiverse forest restoration

Nutrient enrichment can negatively affect natural plant communities and result in the loss of species diversity and productivity. Despite this, fertiliser (especially phosphorus) is typically applied to restore highly biodiverse communities. Long-term effects of nutrient addition to restored plant communities, particularly those adapted to inherently low nutrient soils, have received little attention. We report results of a large-scale 20-year field experiment established in West Australian jarrah forest restored after bauxite mining Three P-application rates were applied (0, 80 and 120 kg ha−1) once at the beginning of the experiment, and plant communities monitored after 1, 6, 13 and 20 years. One year after the onset of restoration, native plant species richness and plant density was highest at 80 and 120 kg P ha−1. Subsequently, native species richness, plant density, and the richness and density of seeder and slow-growing resprouter species were highest without fertilisation, establishing the negative impact of P enrichment on plant community and ecosystem development in P impoverished soils. Total plant cover was similar for all P treatments across the chronosequence which, when combined with higher stem densities at zero P, suggests zero P favoured smaller, slower growing species. Applied-P initially favoured weeds and ephemerals and, while these species declined over time, other species were lost from these plots. The similarity of the restored communities to unmined reference jarrah forest increased over time and was consistently highest at in the absence of P fertiliser. Jarrah forest restoration is assumed to follow the initial floristic model of plant succession. However, we question this assumption and instead suggest that successional outcomes are contingent on P fertilisation rather than initial floristics per se. Applied P retarded recruitment of resprouter species that were present at zero P, debunking the assumption under IFM that these species do not disperse to restored areas. Consequently, based on the most comprehensive long-term study of P-fertilisation in the context of restoration of P-impoverished ecosystems yet reported, we propose that P limitation is important for the recreation of species diversity in inherently P impoverished forests. These results highlight the necessity of long-term experiments for understanding forest successional dynamics and implications for restoration practices

The determinants of election to the United Nations Security Council

This is the author's accepted manuscript. The final publication is available at Springer via http://dx.doi.org/10.1007/s11127-013-0096-4.The United Nations Security Council (UNSC) is the foremost international body responsible for the maintenance of international peace and security. Members vote on issues of global importance and consequently receive perks—election to the UNSC predicts, for instance, World Bank and IMF loans. But who gets elected to the UNSC? Addressing this question empirically is not straightforward as it requires a model that allows for discrete choices at the regional and international levels; the former nominates candidates while the latter ratifies them. Using an original multiple discrete choice model to analyze a dataset of 180 elections from 1970 to 2005, we find that UNSC election appears to derive from a compromise between the demands of populous countries to win election more frequently and a norm of giving each country its turn. We also find evidence that richer countries from the developing world win election more often, while involvement in warfare lowers election probability. By contrast, development aid does not predict election

Equitable representation in councils: theory and an application to the United Nations Security Council

We analyze democratic equity in council voting games (CVGs). In a CVG, a voting body containing all members delegates decision-making to a (time-varying) subset of its members, as describes, e.g., the relationship between the United Nations General Assembly and the United Nations Security Council (UNSC). We develop a theoretical framework for analyzing democratic equitability in CVGs at both the country and region levels, and for different assumptions regarding preference correlation. We apply the framework to evaluate the equitability of the UNSC, and the claims of those who seek to reform it. We find that the individual permanent members are overrepresented by between 21.3 times (United Kingdom) and 3.8 times (China) from a country-level perspective, while from a region perspective Eastern Europe is the most heavily overrepresented region with more than twice its equitable representation, and Africa the most heavily underrepresented. Our equity measures do not preclude some UNSC members from exercising veto rights, however

Fruit / seed freezing tolerance is dependent on developmental status in relation to provenance: a study of Acer pseudoplatanus across Europe

The effects of fruit maturity, at the time of natural dispersal, on subsequent desiccation tolerance and sub-zero storage was investigated in three lots of Acer pseudoplatanus (sycamore) collected from northern to southern Europe. Fruits from the native plant distribution range in Italy had significantly higher desiccation tolerance (0.16 g H2O g-1 DW) than those from England (0.30) and Norway (0.50), confirming that the maximum potential desiccation tolerance in sycamore exceeds that of the recalcitrant type. In contrast, the unfrozen water content varied only slightly between seedlots, but systematically reduced with development (0.35 to 0.27 g H2O g-1 DW). Maximum survival (60% fruit germination) of seven days sub-zero temperature storage coincided with drying the Italian fruit lot to c. 0.2 g H2O g-1 DW followed by holding at -20ºC, above the onset temperature for freezing, or at -196ºC (liquid nitrogen). Fruit survival was much lower in the Italian fruits when held at this water content and -70ºC, and in all other combinations of water content, temperature and fruit lot provenance. As the risk of nucleation in partially dried fruits held at -20ºC is high, we recommend sycamore fruits are cryopreserved for long-term conservation (1).vokMyynti MTT, Tietopalvelut 31600 Jokioine

Can we learn more from fewer seeds?

The vital role that 'design of experiment' (DOE) plays when investigating dormancy, germination and potentially influential factors is discussed. The Taguchi analysis, developed by Dr. Genichi Taguchi, is a special application and analysis of the fractional factorial aimed at achieving maximum information from minimum effort and resources