Abstract: We discuss a property of distance-based measures that has not been addressed with regard to evaluating the geographic concentration of economic activities. The article focuses on the choice between a probability density function of point-pair distances or a cumulative function. We begin by introducing a new cumulative function, M, for evaluating the relative geographic concentration and the co-location of industries in a non-homogeneous spatial framework. Secondly, some rigorous comparisons are made with the leading probability density function of Duranton and Overman (2005), Kd. The merits of the simultaneous use of Kd and M is proved, underlining the complementary nature of the results they provide.

Abstract: Background: Among arboreal ants, both territorially dominant species and plant-ants (e.g. species associated with myrmecophytes or plants housing them in hollow structures) protect their host trees against defoliators. Yet, locally induced responses, or the recruitment of nest-mates when a worker discovers it wound on its host-tree, were only noted in plant-ants. We wondered whether this might be due to the examination of the phenomenon being restricted to only six plant-ant species belonging to four genera. Based on the ant genus Azteca, a Neotropical group of arboreal species, we compared five species. The territorially dominant, carton-nester A. chartifex, three plant-ant species [A. alfari and A. ovaticeps associated with myrmecophitic Cecropia (Cecropiaceae), and A. bequaerti associated with Tococa guianensis (Melastomataceae)], and A. schimperi thought to be a temporary social parasite of true Cecropia ants. Methods: We artificially inflicted wounds to the foliage of the host tree of the different ant species. We then compared the number of workers on wounded versus control leaves. Results: We noted a locally induced response in the three plant-ant species as well as in the territorially dominant species, but very slightly so in A. schimperi.

Abstract: Question: To establish a habitat classification based on functional group co-occurrence that may help the drawing up of conservation plans. Location: Riverine forest fragments in the Grand-duche de Luxembourg, Europe. Methods: Forest fragments were surveyed for their abundance of vascular plants. These were clustered into emergent groups according to 14 life-traits related to plant dispersal, establishment and persistence. Forest fragments were classified according to similar distribution of the identified emergent groups. Environmental factors were related to the emergent group richness in each forest type using generalized linear models. Results: Contrary to former species centred classifications, only two groups of forests, each with clearly different emergent group composition and conservation requirements, were detected: (1) swamp forests characterized by anemogamous perennials, annuals and hydrochorous perennials and (2) moist forests characterized by barochorous perennials, small geophytes and zoochorous phanerophytes. From a conservation point of view, priority should be given to large swamp forest with intact flooding regimes. This is in accordance with the high wind and water dispersal capacities of their typical emergent groups. For the moist forests, conservation priorities should be high forest connectivity and historical continuity since dispersal and establishment of their characteristic emergent groups are highly limited. Conclusions: The described methodology, situated at an intermediate integration level between the individual species and whole community descriptors, takes advantage of both conservation plans built for single species and the synthetic power of broad ecological measures.

Abstract: The fixation of carbon in tropical forests mainly occurs through the production of wood and leaves, both being the principal components of net primary production. Currently field and satellite observations are independently used to describe the forest carbon cycle, but the link between satellite-derived forest phenology and field-derived forest productivity remains opaque. We used a unique combination of a MODIS enhanced vegetation index (EVI) dataset, a wood production model based on climate data and direct litterfall observations at an intra-annual timescale in order to question the synchronism of leaf and wood production in tropical forests. Even though leaf and wood biomass fluxes had the same range (respectively 2.4 ± 1.4 and 2.2 ± 0.4 Mg C ha-1 yr-1), they occurred separately in time. EVI increased with leaf renewal at the beginning of the dry season, when solar irradiance was at its maximum. At this time, wood production stopped. At the onset of the rainy season, when new leaves were fully mature and water available again, wood production quickly increased to reach its maximum in less than a month, reflecting a change in carbon allocation from short-lived pools (leaves) to long-lived pools (wood). The time lag between peaks of EVI and wood production (109 days) revealed a substantial decoupling between the leaf renewal assumed to be driven by irradiance and the water-driven wood production. Our work is a first attempt to link EVI data, wood production and leaf phenology at a seasonal timescale in a tropical evergreen rainforest and pave the way to develop more sophisticated global carbon cycle models in tropical forests. © 2013 Author(s).

Abstract: Precise mapping of above-ground biomass (AGB) is a major challenge for the success of REDD+ processes in tropical rainforest. The usual mapping methods are based on two hypotheses: a large and long-ranged spatial autocorrelation and a strong environment influence at the regional scale. However, there are no studies of the spatial structure of AGB at the landscapes scale to support these assumptions.We studied spatial variation in AGB at various scales using two large forest inventories conducted in French Guiana. The dataset comprised 2507 plots (0.4 to 0.5 ha) of undisturbed rainforest distributed over the whole region. After checking the uncertainties of estimates obtained from these data, we used half of the dataset to develop explicit predictive models including spatial and environmental effects and tested the accuracy of the resulting maps according to their resolution using the rest of the data. Forest inventories provided accurate AGB estimates at the plot scale, for a mean of 325 Mg.ha-1. They revealed high local variability combined with a weak autocorrelation up to distances of no more than10 km. Environmental variables accounted for a minor part of spatial variation. Accuracy of the best model including spatial effects was 90 Mg.ha-1 at plot scale but coarse graining up to 2-km resolution allowed mapping AGB with accuracy lower than 50 Mg.ha-1. Whatever the resolution, no agreement was found with available pan-tropical reference maps at all resolutions.We concluded that the combined weak autocorrelation and weak environmental effect limit AGB maps accuracy in rainforest, and that a trade-off has to be found between spatial resolution and effective accuracy until adequate “wall-to-wall” remote sensing signals provide reliable AGB predictions. Waiting for this, using large forest inventories with low sampling rate (<0.5%) may be an efficient way to increase the global coverage of AGB maps with acceptable accuracy at kilometric resolution. Copyright: © 2015 Guitet et al.