Metrics of hydrological mimicry (‘mimetrics’) reflect similarity in ecological structure and/or functions between managed and natural ecosystems. Only the land-surface parts of hydrological cycles are directly visible and represented in local knowledge and water-related legislation. Human impacts on water cycles (HIWC) can, beyond climate change, arise through effects on local and regional hydrological processes, from both reduced and increased water use compared to a natural reference vegetation with which landscape structure and hydrology are aligned. Precipitationsheds, the oceanic and terrestrial origin of rainfall, depend on evapotranspiration and thus on vegetation. The political commitment to reduce agricultural impact on nature requires hydrological mimetrics to trickle down through institutions to actions. Existing metrics do not suffice. For example, the water footprint metric that relates agricultural water use to consumption decisions, suggests minimizing water use is best, ignoring full hydrological impacts. We explore principles, criteria and indicators for understanding HIWC, via modified evapotranspiration, effects on streamflow (downstream impacts) and atmospheric fluxes and precipitation (downwind impacts). Comprehensive HIWC mimetrics for a set of pantropical watersheds suggest hydrological mimicry options for forest-derived land use patterns through intermediate densities of trees with diversity in rooting depth and water use, interacting with soils, crops and livestock.
Tag: Evapotranspiration
Life-span growth dynamics and xylem anatomical patterns of diffuse-porous Afzelia africana Sm. (Fabaceae) in different ecological zones in Burkina Faso
Tropical West African savannas are exposed to high climatic variability with potential impacts on tree growth, forest dynamics and ecosystem productivity. In such context, understanding the long-term ecological responses of savanna trees to changing environmental conditions is of great relevance for taking appropriate conservation actions. We conducted the first study on tree-ring analysis and quantitative wood anatomy on Afzelia africana Sm. in Burkina Faso, to investigate the life-span growth trajectories and wood anatomical adjustment to site and to climate variations. A total of 24 stem discs was collected in four protected forests along the Sudano-sahelian and the Sudanian climatic zones. Wood samples were analyzed using standard dendrochronological methods and quantitative wood anatomy. The mean annual growth rates varied from 1.002 (± 0.249) mm. year−1 in the Sudanian zone to 1.128 (± 0.436) mm. year−1 in the Sudano-sahelian zone. Analysis of growth trajectories showed high variations within sites and between climatic zones. Wood anatomical traits significantly varied between sites. Principal Component Analysis revealed strong relationships between ring width, wood density and vessel traits, with 82.81 % of the total variance explained. Vessel size significantly increased from the pith to the bark, highlighting the ontogenetic effects on xylem anatomical variations. Inverse relationships were found between vessel size and vessel density across the driest site and the wettest site, suggesting that the higher the rainfall, the taller the tree, the larger vessel size, but the lower vessel density. By contrast, more arid conditions and high evapotranspiration lead to smaller vessel sizes and higher vessel density. Such anatomical adjustments highlight the trade-offs between water conductance efficiency and hydraulic safety, and emphasize physiological responses to climate variability. These variations on the long-term dynamics and xylem anatomical patterns underline complex interactions between ontogenetic effects and contrasting environmental factors that affect the eco-physiological functioning of A. africana throughout the Sudanian region. © 2020 Elsevier GmbH
Water consumption of industrial hemp (Cannabis sativa L.) from a site in northern Kazakhstan
Purpose: This study investigated the water consumption (crop evapotranspiration) of industrial hemp on a newly established hemp field in Aqmola Region of Northern Kazakhstan. Methodology: The water consumption of hemp was investigated through direct measurements of the sapflow movement during the second half of the growing season 2021. These sapflow data yielded data on the water consumption. The water consumption of the first part of the growing season was assessed through the Penman-Monteith approach by FAO. Findings: The water consumption of hemp was 353 mm over the growing season at a stem yield of 10 t/ha. Under the water supply conditions of the study site, hemp offers higher yields than grasslands or grains. Originality/value: This is the first study that revealed data on water consumption of hemp for the region Central Asia as a potential