Enhanced rock weathering (ERW) is a technique proposed to remove large amounts of CO2 from the atmosphere (i.e. a negative emission technology) in which finely fragmented silicate rocks such as basalts (ground basalt) are distributed over agricultural or other land plots. The weathering process involves trapping CO2 but will also typically ameliorate soil properties (pH, soil moisture retention, cation exchange capacity, availability of Si), and can therefore be expected to positively affect plant and microbiological activity. This technique has been proposed in different modified forms over the past decades. In its current format, mainly its potential for near global application (e.g. Beerling et al. 2020) is stressed, and its acceptance is helped by the positive reception by e.g. nature organisations that already apply it as a technique for ecological restoration. Two main and largely separated processes result in trapping of CO2. The first is precipitation of carbonates, often as nodules, in the soil. The second is increased CO2 solubility in groundwater and eventually ocean water due to an increase of the pH value, referred to as the pH-trap. Most of the pH-trapping schemes are built on the assumption that CO2 is dissolved in infiltrating and shallow ground water, then discharged into surface water and consecutively transported to the seas and oceans. In that reservoir CO2 is expected to remain dissolved for centuries and possibly up to ten thousands of years, depending on surfacing times of deep oceanic currents. Another pathway that is systematically overlooked is that of groundwater fluxes that recharge deeper groundwater bodies. Depending on the regional geology, a significant fraction of infiltrating water will engage in deeper and long-term migration. For Belgium, the contribution of hydrodynamic trapping, depending on the hydrogeological setting, could be any part of the 15 to 25% of precipitation that infiltrates. Once infiltrating water enters these cycles, it will not come into contact with the atmosphere for possibly fifty thousand years. In this model, the long-term impact of ERW as a climate mitigation measure rests on a good understanding of the larger hydrogeological context, which encompasses infiltration and the deeper aquifers. Deep aquifers, as well as the migration paths towards them, are strictly isolated and residence times are much longer than for oceans. Recharge areas for deeper aquifer systems may therefore become preferential sites for ERW application, becoming an additional evaluation factor for siting ERW locations that is currently based on surface factors alone.
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RBINS Staff Publications 2021
Epiphytic myrmecophyte distribution along an altitudinal gradient in Papua New Guinea and their role in ant mosaics M. Leponce1 , J. Jacquemin1 & P. Klimes2,3 1Biodiversity Monitoring & Assessment, Royal Belgian Institute of Natural Sciences, Brussels, Belgium (Maurice.Leponce@naturalsciences.be); 2 Biology Centre of ASCR, Czech Republic; 3Faculty of Science, University of South Bohemia in Ceske Budejovice, Czech Republic. In Papua New Guinea, ants of the genera Philidris, Anonychomyrma, Monomorium are found in epiphytic myrmecophytes of the genera Myrmecodia and Hydnophytum. Several myrmecophytes are found in the same tree and accomodate a high ant population. This omnipresence in some tree canopies allow these ants to be potential actors of ant mosaics. Ants mosaics refer to mutual exclusion of numerically dominant ants from tree tops and are a common feature of tree plantations and lowland tropical forests. Our aim was to verify if ants associated with myrmecophytes were found co-occurring with typical dominant ants (e.g. Oecophylla smaragdina and Crematogaster polita) and if the interaction between dominant canopy ants was affected by elevation. We mapped the distribution of numerically dominant ant colonies, often spreading on several neighbour trees, in ¼ ha plots distributed between 200 and 2700m asl along Mt Wilhelm, Papua New Guinea. Ants were captured at tuna/honey baits spread along tree trunks from the ground to the top of canopy trees. Epiphytic myrmecophyte were collected by climbing or by using a balloon. In lowland forests (200-700m) Crematogaster polita large carton nests were omnipresent and often formed supercolonies. Other major players were Oecophylla smaragdina nesting in leaves and Anonychomyrma cf scrutator nesting in live plant tissues. Ants associated with myrmecophytes were never found co-occuring with these dominant ants. At mid-elevation (1200-1700m) dominant ants were Anonychomyrma spp. and two species found in myrmecophytes (Monomorium sp. nov. aff. edentatum and Philidris cf. cordata). At 2200m ants found in the canopy (e.g. Ancyridris, Pheidole) were probably living in suspended soil. No ants were observed in the canopy above 2700m. With increasing elevation it seems that there is a progressive filtering of the most abundant arboreal ant species. Typical territorial ants, living in carton or leaf nests are eliminated first. At mid-elevation epiphytic myrmecophytes allow to maintain high ant populations in trees. At high elevation only species nesting in suspended organic matter remain.
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RBINS Staff Publications 2016
