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Mardamootoo T.,Mauritius Sugarcane Industry Research Institute | du Preez C.C.,University of the Free State | Sharpley A.N.,University of Arkansas
Nutrient Cycling in Agroecosystems | Year: 2015

The continuous application of phosphorus (P) to agricultural systems to ensure profitable crop productivity can lead to an accumulation of P in agricultural soils. While this long-term residual pool of soil P is desirable from an agronomic perspective, there is some concern about its possible impacts on surface water quality as it may lead to eutrophication. Since a better understanding of P transport processes provides useful information for the development of site-specific P management strategies, rainfall simulation studies (100 mm h−1 for 30 min) on runoff plots (2.1 m × 0.75 m) were conducted at 20 field sites to study the mobilisation of soil P from sugarcane fields of Mauritius. The research findings indicated that the edge-of-plot P losses were insignificant from an agronomic perspective but only small amounts of P can actually trigger eutrophication in freshwaters. The results also showed that total P concentrations in runoff are more strongly associated with runoff sediments (r2 = 0.92) than runoff volume (r2 = 0.49) indicating that a greater proportion of the P transported in runoff occurred as particulate P rather than dissolved P. Actually, about 89 % of total P loss in runoff waters was mobilised in particulate form, pointing to the importance of erosion as a mechanism for mobilising soil P. The research findings suggest that in addition to the current management practices aiming at reducing runoff volume, such as conservation tillage and trash cover, measures that reduce sediments in runoff, such as grassed waterways and riparian buffers, may further attenuate P losses. © 2015, Springer Science+Business Media Dordrecht. Source


Morgan K.,Max Planck Institute for Developmental Biology | Mcgaughran A.,Max Planck Institute for Developmental Biology | Ganeshan S.,Mauritius Sugarcane Industry Research Institute | Herrmann M.,Max Planck Institute for Developmental Biology | Sommer R.J.,Max Planck Institute for Developmental Biology
Biological Journal of the Linnean Society | Year: 2014

Despite the biological importance and diversity of nematodes, little is known of the factors influencing their dispersal and shaping their evolutionary history. Populations of the cosmopolitan species Pristionchus pacificus are characterized by high genetic diversity and strong spatial structure, which contrasts with patterns detected in nematode species such as Caenorhabditis elegans. The environmentally heterogeneous volcanic Mascarene Islands provide an ideal setting for investigating fine-scale patterns of nematode migration and gene flow. Based on the analysis of data from 19 nuclear microsatellites and one mitochondrial marker, we infer support for the colonization of both La Réunion Island and Mauritius from similar multiple geographical sources. Although the long-term persistence of populations on both islands is well supported, the historical colonization of one island from the other cannot be discounted. In fact, periodic, bi-directional migration between the islands following their initial colonization is strongly supported in isolation with migration analyses, supporting the occurrence of rare trans-oceanic dispersal events in P.pacificus. Through a combination of population and landscape genetic analyses we also infer non-uniform dispersal across the landscape on the island of La Réunion, probably mediated by the movements of beetle hosts. Collectively, we show that gene flow in P.pacificus is limited by environmental and oceanic barriers, and shaped by the intricacies of the nematode-beetle host interaction. © 2014 The Linnean Society of London. Source


Dubuisson J.-Y.,University Pierre and Marie Curie | Rouhan G.,CNRS Systematics, Biodiversity and Evolution Institute | Grall A.,University Pierre and Marie Curie | Grall A.,Natural History Museum in London | And 4 more authors.
Acta Botanica Gallica | Year: 2013

The diversity of species belonging to the filmy fern genus Crepidomanes (Hymenophyllaceae) in the Mascarene archipelago was studied, based on morphological investigations and focusing especially on the most dwarf species that are easily confused in the field and in herbarium collections. Morphological potential clusters and discriminations were then compared with an RBCL phylogeny. As a result, we recognized at least eight morpho-species for the archipelago and defined characters for distinguishing the three smallest ones, Crepidomanes bonapartei, Crepidomanes minutum and Crepidomanes (Trichomanes) trinerve. Morphological evidence and molecules confirm the specific status for T. trinerve (newly combined in Crepidomanes), the inclusion of Crepidomanes mannii into a C. minutum complex, and new records of C. bonapartei for Mauritius. The neotropical Polyphlebium pyxidiferum is found to be closely related to Afro-Madagascan Crepidomanes inopinatum and Crepidomanes melanotrichum species and so is newly combined in Crepidomanes. A key for the eight species of the genus in the archipelago, description of a new section clustering Crepidomanes frappieri and Crepidomanes longilabiatum, and new enhanced descriptions for two dwarf taxa (C. bonapartei and C. trinerve) are provided, and biogeographical origins of the genus in the Western Indian Ocean area are discussed. © 2013 Copyright Société botanique de France. Source


Ogle S.M.,Colorado State University | Buendia L.,College Ville | Butterbach-Bahl K.,Karlsruhe Institute of Technology | Butterbach-Bahl K.,Kenya International Livestock Research Institute | And 7 more authors.
Environmental Research Letters | Year: 2013

Developing countries face many challenges when constructing national inventories of greenhouse gas (GHG) emissions, such as lack of activity data, insufficient measurements for deriving country-specific emission factors, and a limited basis for assessing GHG mitigation options. Emissions from agricultural production are often significant sources in developing countries, particularly soil nitrous oxide, and livestock enteric and manure methane, in addition to wetland rice methane. Consequently, estimating GHG emissions from agriculture is an important part of constructing developing country inventories. While the challenges may seem insurmountable, there are ways forward such as: (a) efficiently using resources to compile activity data by combining censuses and surveys; (b) using a tiered approach to measure emissions at appropriately selected sites, coupled with modeling to derive country-specific emission factors; and (c) using advanced software systems to guide compilers through the inventory process. With a concerted effort by compilers and assistance through capacity-building efforts, developing country compilers could produce transparent, accurate, complete, consistent and comparable inventories, as recommended by the IPCC (Intergovernmental Panel on Climate Change). In turn, the resulting inventories would provide the foundation for robust GHG mitigation analyses and allow for the development of nationally appropriate mitigation actions and low emission development strategies. © 2013 IOP Publishing Ltd. Source


Umrit G.,Mauritius Sugarcane Industry Research Institute | Ng Cheong R.,Mauritius Sugarcane Industry Research Institute | Gillabel J.,Sustainable Materials Management | Merckx R.,Catholic University of Leuven
Plant and Soil | Year: 2014

Aims: Maintenance of adequate levels of soil organic carbon (SOC) is crucial for the biological, chemical and physical functioning of soils. This study was conducted (i) to determine the impact of long-term sugarcane monoculture on total SOC stocks and on its labile fractions and (ii) to quantify the loss of original SOC and the accretion of sugarcane-derived C following the adoption of new management practices namely de-rocking/land grading and mechanized harvesting. Methods: Five study sites representing the five major soil groups under sugarcane in Mauritius were selected with a classical "paired-plot" design adopted. In this design, two sites with similar initial conditions were developed in different ways over time. One represents the reference soil (virgin land with predominantly C3 type vegetation) and the other represents one of the following cropping treatments: (i) fields continuously cultivated with sugarcane for more than 25 or 50 years without de-rocking or land grading, (ii) fields under long-term sugarcane but having undergone de-rocking and land grading for mechanized harvesting in the last 3 years. Soil samples were taken to a depth of 50 cm and analysed for total organic C, labile C, 13C natural abundance, bulk density and stone content. Results: Changes in SOC stock in the 0-50 cm profile following >50 years of cane cropping were not significant (P > 0.05) compared to virgin land at any site. Soil δ13C values revealed that long-term sugarcane cultivation resulted in a depletion of original SOC by 34 to 70 %. However, this loss was fully compensated by C input from sugarcane residues at all sites studied resulting in no net change in SOC stock. Adoption of mechanized harvest did not have any detrimental effect on SOC stocks due to C inputs from crop residues. However, long-term sugarcane cultivation resulted in significant decline in a labile C (KMnO4-oxidizable) fraction. Conclusion: Despite the large losses of original C following conversion from forest to sugarcane, long-term sugarcane cultivation resulted in sequestration of sugarcane-derived C which adequately compensated these losses. Moreover, intensive de-rocking and land grading preceding mechanized harvesting did not have any detrimental effect on SOC stocks. However, the quality of sugarcane soils, as indicated by a decline in labile C, could be degraded. © 2014 Springer International Publishing Switzerland. Source

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