Changes in water fluxes partition related to the replacement of native dry forests by crops in the Dry Chaco
JOURNAL OF ARID ENVIRONMENTS
Authors: Rodriguez, Paula; Gimenez, Raul; Nosetto, Marcelo D.; Jobbagy, Esteban G.; Magliano, Patricio N.
Abstract
Land-use change has been the strongest driver of vegetation cover change in the world. In the South American Dry Chaco (similar to 1 M km(2); PPT/ET0 < 0.65), native dry forests are experiencing high deforestation rates that tend to continue in the coming years. Here, we used a hydrological model (Hydrus 1-D) to analyze changes in the water balance triggered by the replacement of dry forests by annual rainfed summer crops. We found that transpiration represented the main water vapour flux in both vegetation covers (59 and 48% of annual rainfall in dry forest and cropland, respectively), followed by evaporation (31 and 30%, respectively) and interception (11 and 9%, respectively). Runoff was five times higher in the cropland compared to the dry forest (10 vs. 2%; p < 0.01). Deep drainage was a negligible water flux in dry forests but it represented 4% of annual rainfall in croplands (p < 0.01), reaching values of zero and 130 mm year(-1) for dry and wet years, respectively. Our results highlight the key role of vegetation cover controlling ecosystem water fluxes in the Dry Chaco. More generally, we suggest that the expansion of dryland cultivation can modify the regional water balance and threaten the primary production of ecosystems in the long run.
Compact formulations for multi-depot routing problems: Theoretical and computational comparisons
COMPUTERS & OPERATIONS RESEARCH
Authors: Bektas, Tolga; Gouveia, Luis; Santos, Daniel
Abstract
Multi-depot routing problems mainly arise in distribution logistics where a fleet of vehicles are used to serve clients from a number of (potential) depots. The problem concerns deciding on the routes of each vehicle and the depots from which the vehicles depart, so as to minimize the total cost of travel. This paper reviews a number of existing compact formulations, and proposes new ones, for two types of multi-depot routing problems, one that includes the depot selection decisions, and the other where depots are pre-selected. The formulations are compared theoretically in terms of the strength of their linear programming relaxation, and computationally in terms of the running time needed to solve the instances to optimality. (c) 2020 Elsevier Ltd. All rights reserved.