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This work aimed to assess the performance of different thermal infrared (TIR)-based physiological indicators (PI) as an alternative to the stem water potential (Ψs) and stomatal conductance (gs) to monitor the water status of grafted drip-irrigated 'Regina' cherry trees. In addition, we evaluated the usefulness of piecewise linear regression for finding PI thresholds that are important for post-harvest regulated deficit irrigation (RDI) management. With this purpose, an irrigation experiment was carried out in the post-harvest period. Trees were submitted to three Ψs-based water-stress treatments: T0 (fruit grower management treatment, or control) (Ψs > − 1.0 MPa, without-to-low water stress); T1 (low-to-mild water-stress treatment = − 1.0 > Ψs > − 1.5 MPa); and T2 (mild-to-severe water-stress treatment = − 1.5 > Ψs > − 2.0 MPa). The results indicated that the trees were more stressed in T2 than in T0. In the former, averages of Ψs and gs were − 1.75 MPa and 372 mmol m−2 s−1, whereas they were − 1.56 MPa and 427 mmol m−2 s−1 in T0. The piecewise model allowed determining the water-stress thresholds of almost all studied PI. The breakpoints yielded by this analysis indicated that trees at Ψs lower than − 1.5 MPa had a gs lower than 484 mmol m−2 s−1. These results also showed that TIR-based PI, whose equations incorporate a temperature normalization, are a better indicator of cherry tree water status than those without normalization. The derived TIR-based PI threshold values could be used as a reference for managing drip-irrigated 'Regina' cherry trees. [ABSTRACT FROM AUTHOR]

Forest plantations are economically and environmentally relevant, as they play a key role in timber production and carbon capture. It is expected that the future climate change scenario affects forest growth and modify the rotation age for timber production. However, mathematical models on the effect of climate change on the rotation age for timber production remain still limited. We aim to determine the optimal rotation age that maximizes the net economic benefit of timber volume in a negative scenario from the climatic point of view. For this purpose, a bioeconomic optimal control problem was formulated from a system of Ordinary Differential Equations (ODEs) governed by the state variables live biomass volume, intrinsic growth rate, and area affected by fire. Then, four control variables were associated to the system, representing forest management activities, which are felling, thinning, reforestation, and fire prevention. The existence of optimal control solutions was demonstrated, and the solutions of the optimal control problem were also characterized using Pontryagin’s Maximum Principle. The solutions of the model were approximated numerically by the Forward–Backward Sweep method. To validate the model, two scenarios were considered: a realistic scenario that represents current forestry activities for the exotic species Pinus radiata D. Don, and a pessimistic scenario, which considers environmental conditions conducive to a higher occurrence of forest fires. The optimal solution that maximizes the net benefit of timber volume consists of a strategy that considers all four control variables simultaneously. For felling and thinning, regardless of the scenario considered, the optimal strategy is to spend on both activities depending on the amount of biomass in the field. Similarly, for reforestation, the optimal strategy is to spend as the forest is harvested. In the case of fire prevention, in the realistic scenario, the optimal strategy consists of reducing the expenses in fire prevention because the incidence of fires is lower, whereas in the pessimistic scenario, the opposite is true. It is concluded that the optimal rotation age that maximizes the net economic benefit of timber volume in P. radiata plantations is 24 and 19 years for the realistic and pessimistic scenarios, respectively. This corroborates that the presence of fires influences the determination of the optimal rotation age, and as a consequence, the net economic benefit. [ABSTRACT FROM AUTHOR]