Water cycle
The role of vegetation in precipitation and drought resilience
Analysis
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There is an urgent need that agricultural research focuses on how to close water cycles in the landscape and the development of farming systems with a more vertically-layered vegetation structure keeping water and lower temperatures during a sunny day.
Vegetation cover has been shown to affect local, regional and continental climates
Forests and trees are prime regulators within the water, energy and carbon cycles. Land cover change accounts for some 18% of global warming trends.
An average tree can transpire hundreds of litres of water per day. Every 100 litres of water transpired equates in cooling power to the daily output of two central air-conditioning units for an average home.
Diversity key to drought resilience in forests (Higher forest biodiversity - specifically plant functional diversity related to water, or hydraulic, transport - engenders greater ecosystem resilience to drought).
Diversity key to drought resilience in grasslands. Subordinate species in species rich grassland drive the resistance to drought - this is probably because of their ability to increase water availability through specific interaction with the soil microbial community e.g. mycorrhizal fungi
Deforestation is as large a driving force as irrigation in terms of changes in the hydrological cycle. Deforestation has decreased global vapor ows from land by 4% (3,000 km3/yr), a decrease that is quantitatively as large as the increased vapor ow caused by irrigation (2,600 km3/yr).
Changes in precipitation and radiation [greenhouse effect] do not play the primary role in future drying and moistening in most regions. Rather, biosphere interactions are key for predicting future continental water stress (evapotranspiration, long-term runoff, EF, or leaf area index). Vegetation water stress largely regulates land carbon uptake.
Enhanced evapotranspiration can increase moist convection, leading to increased precipitation. Earth system models underestimate these precipitation and radiation feedbacks. Biosphere–atmosphere feedbacks cluster in specific climatic regions that help determine the net CO2 balance of the biosphere.
The capacity of continents to act as a future carbon sink critically depends on the nonlinear response of carbon fluxes to soil moisture and on land–atmosphere interactions. Soil moisture has large influence on carbon uptake. Therefore, agricultural systems that increase soil moisture, on average, also increase soil carbon.
While runoff volume was reduced, lateral and groundwater flow increased under ICL system scenarios. This indicates that incorporation of cattle grazing of corn residue or winter barley might positively affect processes involved in soil water storage and transit. Of the three components contributing to water yield (i.e. runoff volume, lateral and groundwater flow), groundwater flow had the largest relative impact on stream flow through increased base flow. Ecosystem services derived from the adoption of ICL systems would be valuable to flooding managers and watershed planners
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