Drought‐induced tree mortality is expected to increase globally due to climate change, with profound implications for forest composition, function and global climate feedbacks. How drought is experienced by different species is thought to depend fundamentally on where they access water vertically below‐ground, but this remains untracked so far due to the difficulty of measuring water availability at depths at which plants access water (few to several tens of metres), the broad temporal scales at which droughts at those depths unfold (seasonal to decadal), and the difficulty in linking these patterns to forest‐wide species‐specific demographic responses. We address this problem through a new eco‐hydrological framework: we used a hydrological model to estimate below‐ground water availability by depth over a period of two decades that included a multi‐year drought. Given this water availability scenario and 20 year long‐records of species‐specific growth patterns, we inversely estimated the relative depths at which 12 common species in the forest accessed water via a model of water stress. Finally, we tested whether our estimates of species relative uptake depths predicted mortality in the multi‐year drought. The hydrological model revealed clear below‐ground niches as precipitation was decoupled from water availability by depth at multi‐annual scale. Species partitioned the hydrological niche by diverging in their uptake depths and so in the same forest stand, different species experienced very different drought patterns, resulting in clear differences in species‐specific growth. Finally, species relative water uptake depths predicted species mortality patterns after the multi‐year drought. Species that our method ranked as relying on deeper water were the ones that had suffered from greater mortality, as the zone from which they access water took longer to recharge after depletion. Synthesis. This research changes our understanding of how hydrological niches operate for trees, with a trade‐off between realized growth potential and survival under drought with decadal scale return time. The eco‐hydrological framework highlights the importance of species‐specific below‐ground strategies in predicting forest response to drought. Applying this framework more broadly may help us better understand species coexistence in diverse forest communities and improve mechanistic predictions of forests productivity and compositional change under future climate.
20 July 2023 in Environment, Development and Sustainability
Pressure management is one of the most efficient ways to reduce leaks in water networks. Conventional pressure management techniques in water networks deals with the control of a single boundary Pressure Reducing Valve (PRV). The real-world water network under study in this work has multiple internal PRVs within the DMA, which makes direct application of the existing pressure management techniques difficult. In this study, we have formulated a simulation-optimization framework that involves network sectorization and PRV control. Initially, the DMA was divided into multiple Pressure Management Areas (PMAs), based on the location and control area of each PRV. The control strategy was then formulated for each PRV based on remote node modulation. The results of this study showed that the use of multiple internal PRVs within a DMA helped in better pressure management than a single boundary PRV. This control strategy helped in reducing the NRW to 18% from 24%.