Pretty (and) invasive: The potential global distribution of Tithonia diversifolia under current and future climates

Tithonia diversifolia (Mexican sunflower) is an invasive plant, native to the New World, and an exemplary conflict species. It has been planted widely for its ornamental and soil fertility enhancement qualities and has become a notorious environmental weed in introduced habitats. Here we use a bioclimatic niche model (CLIMEX) to estimate the potential global distribution of this invasive plant under historical climatic conditions. We apply a future climate scenario to the model to assess the sensitivity of the modelled potential geographical range to expected climate changes to 2050. Under current climatic conditions, there is potential for substantial range expansion into southern Europe with moderate climate suitability, and in southern China with highly suitable climates. Under the near-term future climate scenario there is potential for poleward range expansion in the order of 200 – 500 km. In the tropics, climatic conditions are likely to become less favourable due to the increasing frequency of supra-optimal temperatures. In areas experiencing Mediterranean or warm temperate climates the suitability for T. diversifolia appears set to increase as temperatures warm. There are vast areas in North America, Europe and Asia (particularly China and India) that can support ephemeral populations of T. diversifolia. One means of enjoying the aesthetic benefits of T. diversifolia while avoiding the unwanted environmental impacts as it invades areas prized for environmental attributes is to try to prevent its spread into areas climatically suitable for establishment, and only allow it to be propagated in areas where it cannot persist naturally.

SOC modelling and cropping system managements in contrasting climatic conditions

<p>Conservation agriculture (CA) involves complex and interactive processes that ultimately determine soil C storage, making it difficult to identify clear patterns, particularly, when the results originate from many experimental studies. To solve these problems, we used the ARMOSA process-based crop model to simulate the contribution of different CA components (minimum soil disturbance, permanent soil cover with crop residues and/or cover crops, and diversification of plant species) to soil organic carbon (SOC) sequestration at 0-30 cm soil depth and to compare it with SOC evolution under conventional agricultural practices. We simulated SOC changes in two sites located in Central Asia (Almalybak, Kazakhstan) and Southern Europe (Lombriasco, Italy), which have contrasting soils, organic carbon contents, climates, crops and management intensity.  Simulations were carried out for the current (1998-2017) and future climatic scenarios (period 2020-2040, scenario Representative Concentration Pathway 6.0).</p><p>Five cropping systems were simulated: conventional systems under ploughing at 25-30 cm with monoculture and  residues removed (Conv–R) or residues retained (Conv+R); no-tillage (NT) with residue retained and crop monocultures; CA and CA with a cover crop, Italian ryegrass (CA+CC). In Conv–R, Conv+R and NT, the simulated monocultures were spring barley in Almalybak and maize in Lombriasco. In CA and CA+CC, crop rotations were winter wheat - winter wheat - spring barley - chickpea in Almalybak; maize - winter wheat - soybean in Lombriasco, together with Italian ryegrass in the +CC options.</p><p>In Lombriasco, conventional systems led to SOC decline of 170-350 kg ha<sup>-1</sup> yr<sup>-1</sup>, whereas, NT and CA prevented the decline and kept it on the slightly positive level under both climate scenarios. A low rate of SOC increase most likely stems from, in addition to climates, the low silt-clay fraction (34%), and thus, more vulnerable to mineralization and decay.</p><p>In Almalybak, SOC loss in conventional systems was 480-560 kg ha<sup>-1</sup> yr<sup>-1</sup> under current climate, and NT prevented the loss only under current climate, but not under the future climate scenario. In contrast, CA allowed for the annual C sequestration of 300 kg ha<sup>-1</sup> and up to 620 kg ha<sup>-1</sup> with cover crops. Under the future climate scenario, the model predicted somewhat less C sequestration under CA, probably, due to the reduction of residue biomass. Particularly, in Southern Kazakhstan, CA has the largest potential for C sequestration under both climate scenarios, twice exceeding the objectives of the “4 per 1000” initiative. This initiative claims that an annual growth rate of 0.4% in the soil carbon stocks, or 4‰ per year, in the first 30-40 cm of soil, would significantly reduce the CO<sub>2</sub> concentration in the atmosphere related to human activities.</p>

Different Responses in Geographic Range Shifts and Increase of Niche Overlap in Future Climate Scenario of the Subspecies of Melipona quadrifasciata Lepeletier

Climate change is suggested to be one of the possible drivers of decline in pollinators. In this paper, we applied an ecological niche model to modeling distributional responses in face of climate changes for the subspecies of Melipona quadrifasciata Lepeletier. This species is divided into two subspecies based on difference in the yellow tergal stripes, which are continuous in M. q. quadrifasciata and interrupted in M. q. anthidioides. The geographic distribution of each subspecies is also distinct. M. q. quadrifasciata is found in colder regions in the Southern states of Brazil, whereas M. q. anthidioides is found in habitats with higher temperatures, suggesting that ecological features, such as adaption to distinct climatic conditions may take place. Thus, the possibility of having diff erent responses in geographic range shifts to future climate scenario would be expected. This study aimed to investigate the eff ects of climate changes on the distribution of the two M. quadrifasciata subspecies in Brazil, using an ecological niche model by the MaxEnt algorithm. Our results indicate that the subspecies showed clear diff erences in geographic shift patterns and increased climate niche overlap in the future scenarios. M. q. anthidioides will have the potential for an increase of suitable climatic conditinos in the Atlantic Forest, and towards the Pampa biome, while M. q. quadrifasciata will suffer a reduction of adequate habitats in almost all of its current geographic distribution. Given the potential adverse eff ects of climate changes for this subspecies, conservation actions are urgently needed to avoid that it goes extinct.