Water balance of an Atlantic forest remnant under a prolonged drought period

Abstract

Since prolonged droughts have impacted Atlantic forests in Southeastern Brazil, further investigations to understand the effects of such stressful conditions in their hydrological behavior are required. This study aimed to assess the changes in the water balance of a semi-deciduous Atlantic forest remnant and how the forest responds to droughts. The Standardized Precipitation-Evapotranspiration Index was applied to identify droughts (from 1961 to 2019) and their severity in both the hydrological year and summer scales. Drought impacts on actual evapotranspiration, potential percolation, and soil water storage were assessed using Hydrus-1D, having net precipitation and potential evapotranspiration as inputs. Error analyses (< 10%) confirmed Hydrus-1D suitability for simulating soil moisture. Uncertainties regarding the soil saturated hydraulic conductivity are due to preferential flows, which are not accounted for in Richards’ equation. Drought intensification changed forest hydrology and triggered physiological responses to deal with it. Semi-deciduous Atlantic forests are adapted to dry conditions because of the existence of dry-affiliated species and the activation of physiological mechanisms. However, such adaptations responded differently regarding the drought scales. The intensification of summer droughts increased evapotranspiration and decreased the potential percolation. Leaf shedding changed the canopy structure in a two-year time lag as a response to the intensification of hydrological year droughts. Changes in forest hydrology are sudden and trigger physiological responses, such as leaf shedding, in a delayed process after droughts take place.

Remote sensing environmental indicators for monitoring spatial and temporal dynamics of water and vegetation conditions: applications to the Brazilian biomes

“…From water balance studies in Atlantic Forest, Pereira et al (2010), found an average annual ET of 3.20 mm d -1 , a little higher than that from Table 3. However, also from water balance measurements between 2013 and 2018 in this biome, Rodrigues et al (2021) reported ET mean values from 1.40 to 1.80 mm d -1 , inside the ranges for Q3…”

The Consequences of Climate Change in the Brazilian Western Amazon: A New Proposal for a Fire Risk Model in Rio Branco, Acre

“…An environment with low humidity and precipitation conditions facilitates the spread of fire. Therefore, arboreal individuals inserted in this context are more exposed to fires, normally caused by the management of the area before agricultural activities [43].…”

Impacts of Land Use Changes on Soil Functions and Water Security: Insights from a Three-Year-Long Study in the Cantareira System, Southeast of Brazil

“…The monitoring conducted in August 2020 showed a drier winter with no precipitation when compared to the previous year, in which eucalyptus was the only use that was able to maintain a water content greater than 0.24 m 3 m −3 up to a depth of approximately 0.50 m. During the dry period of the previous year, the extensive pasture exhibited the same drying pattern as before and dried out more compared to the rotated pasture, particularly deeper in the soil. In the following summer (March 2021), high precipitation events were observed (Figure 2) after a long dry period, in which eucalyptus stored water along the soil profile up to 1.50 m. Nonetheless, the estimated percolation cannot be considered as water recharge since the water balance analysis only considered the 1.5 m soil depth, while certain tree species are adapted to extracting water from deeper layers [52]. Yu et al [11] conducted a study on the seasonal variation of soil moisture in medium-textured soil under different land uses to a depth of 5.0 m. They were able to infer that moisture levels stabilized with minor fluctuations below a depth of 2.0 m.…”