Benefits of crowd-sourced GPS information for modelling the recreation ecosystem service.

Modelling cultural ecosystem services is an enduring challenge, raising issues about the integration and spatialization of immaterial values and benefits, and their contingency on local preferences. Building on the Recreation Opportunity Spectrum framework, we present a novel methodology for assessing the recreation service using GPS tracks downloaded from crowd-sourced websites: the Grelou model (Georeferencing REcreation in Local OUtdoors), here applied to the Grenoble living area (French Alps). GPS tracks revealed the complete spatial extent of visitor presence and enabled modelling visitation networks for ten recreation activities with great spatial accuracy, thus providing a spatial estimate of recreational multifunctionality-expressed as the sum of networks. After coupling track networks with landscape preference and proximity factors, Grelou assessed the recreation service as a combination of opportunity and preferences, and identified recreation hotspots of different profiles such as aroundoor leisure or outdoor sport. We performed an online survey among local sports associations using an interactive map to select districts visited by respondents (~1000 people). The declared visitor presence for recreation purposes was highly spatially congruent with Grelou outputs (R2 = 0.89). Detailed analysis of responses on selection criteria for recreationists validates our choice of critical factors underlying both the recreation opportunity potential and the expected visitation frequency over the whole study area. We also analyzed outputs of the InVESt recreation model against the same visitation explanatory factors. Differences between the two models allowed us to pinpoint biases and weaknesses in the InVESt recreation modelling framework based on crowd-sourced photographs. By making use of an increasingly available data source (GPS tracks), Grelou offers a standardized and flexible way to assess the recreation service associated with multiple recreation practices. Its high spatial accuracy supports the analysis of spatial relationships with other ecoystems services and the integration of recreation into environmental assessments, land management and planning.

Invasive knotweeds are highly tolerant to salt stress.

Japanese knotweed s.l. are some of the most invasive plants in the world. Some genotypes are known to be tolerant to the saline concentrations found in salt marshes. Here we focus on tolerance to higher concentrations in order to assess whether the species are able to colonize and establish in highly stressful environments, or whether salt is an efficient management tool. In a first experiment, adult plants of Fallopia japonica, Fallopia × bohemica and Fallopia sachalinensis were grown under salt stress conditions by watering with saline concentrations of 6, 30, 120, or 300 g L(-1) for three weeks to assess the response of the plants to a spill of salt. At the two highest concentrations, their leaves withered and fell. There were no effects on the aboveground parts at the lowest concentrations. Belowground dry weight and number of buds were reduced from 30 and 120 g L(-1) of salt, respectively. In a second experiment, a single spraying of 120 g L(-1) of salt was applied to individuals of F. × bohemica and their stems were clipped to assess the response to a potential control method. 60 % of the plants regenerated. Regeneration was delayed by the salt treatment and shoot growth slowed down. This study establishes the tolerance of three Fallopia taxa to strong salt stress, with no obvious differences between taxa. Their salt tolerance could be an advantage in their ability to colonize polluted environments and to survive to spills of salt.