The role of deep roots in the hydrological and carbon cycles of Amazonian forests and pastures

Nepstad, Daniel C.; Carvalho, Carlos Roberto Ribeiro; Davidson, Eric A.; Jipp, Peter; Lefebvre, Paul; Negreiros, Gustavo; Silva, Elson D. da; Stone, T.A.; Trumbore, Susan E.; Vieira, Simone A.

doi:10.1038/372666a0

Cited by 1,255 publications

(990 citation statements)

References 19 publications

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“…However, deep roots have been observed down to around 18 m in the Amazon (Nepstad et al 1994), and deep roots may be particularly important in arid and semiarid regions (Canadell et al 1996). To test how important this is, we perform an additional sensitivity test that is the same as VAR except that root fractions are allowed in all layers.…”

Section: Resultsmentioning

confidence: 99%

“…As the focus of this paper is on the effects of variable soil thickness and not on vegetation, we do this to keep the model as similar to the CLM4.5 release as possible. However, deep roots have been observed in places like the Amazon (Nepstad et al 1994;Zeng et al 1998) and may play more of a role in arid and semiarid environments (Canadell et al 1996). The root fraction distribution might need to be adjusted to account for the possibility of these deep roots in the future.…”

Section: The Modelmentioning

confidence: 99%

“…In fact, some plants are highly reliant on groundwater (Orellana et al 2012;Rossatto et al 2012). Roots have been documented down to around 18 m in the Amazon (Nepstad et al 1994) and even deeper elsewhere (Canadell et al 1996). Fan et al (2013) estimated that the water table was high enough to be used by plants in between 7% and 17% of global land.…”

Section: Introductionmentioning

confidence: 99%

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Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5)

et al. 2016

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One of the recognized weaknesses of land surface models as used in weather and climate models is the assumption of constant soil thickness because of the lack of global estimates of bedrock depth. Using a 30-arc-s global dataset for the thickness of relatively porous, unconsolidated sediments over bedrock, spatial variation in soil thickness is included here in version 4.5 of the Community Land Model (CLM4.5). The number of soil layers for each grid cell is determined from the average soil depth for each 0.98 latitude 3 1.258 longitude grid cell. The greatest changes in the simulation with variable soil thickness are to baseflow, with the annual minimum generally occurring earlier. Smaller changes are seen in latent heat flux and surface runoff primarily as a result of an increase in the annual cycle amplitude. These changes are related to soil moisture changes that are most substantial in locations with shallow bedrock. Total water storage (TWS) anomalies are not strongly affected over most river basins since most basins contain mostly deep soils, but TWS anomalies are substantially different for a river basin with more mountainous terrain. Additionally, the annual cycle in soil temperature is partially affected by including realistic soil thicknesses resulting from changes in the vertical profile of heat capacity and thermal conductivity. However, the largest changes to soil temperature are introduced by the soil moisture changes in the variable soil thickness simulation. This implementation of variable soil thickness represents a step forward in land surface model development.

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Section: Resultsmentioning

confidence: 99%

Section: The Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5)

et al. 2016

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“…Thus, despite the deeper root systems of the forests (cf. Nepstad et al, 1994), mean soil water use for the agricultural crops under consideration, pasture, and forests is quite similar, possibly due to the relatively rainy climate prevailing in Puerto Rico all year round (Calvesbert, 1970). To this, rainfall interception losses (higher for forest) should be added.…”

Section: Field-based Estimates Of Vegetation Water Usementioning

confidence: 99%

The impact of forest regeneration on streamflow in 12 mesoscale humid tropical catchments

Beck

Bruijnzeel

Dijk

et al. 2013

Hydrol. Earth Syst. Sci.

103

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Abstract. Although regenerating forests make up an increasingly large portion of humid tropical landscapes, little is known of their water use and effects on streamflow (Q). Since the 1950s the island of Puerto Rico has experienced widespread abandonment of pastures and agricultural lands, followed by forest regeneration. This paper examines the possible impacts of these secondary forests on several Q characteristics for 12 mesoscale catchments (23-346 km 2 ; mean precipitation 1720-3422 mm yr −1 ) with long (33-51 yr) and simultaneous records for Q, precipitation (P ), potential evaporation (PET), and land cover. A simple spatially-lumped, conceptual rainfall-runoff model that uses daily P and PET time series as inputs (HBV-light) was used to simulate Q for each catchment. Annual time series of observed and simulated values of four Q characteristics were calculated. A least-squares trend was fitted through annual time series of the residual difference between observed and simulated time series of each Q characteristic. From this the total cumulative change (Â) was calculated, representing the change in each Q characteristic after controlling for climate variability and water storage carry-over effects between years. Negative values ofÂ were found for most catchments and Q characteristics, suggesting enhanced actual evaporation overall following forest regeneration. However, correlations between changes in urban or forest area and values ofÂ were insignificant (p ≥ 0.389) for all Q characteristics. This suggests there is no convincing evidence that changes in the chosen Q characteristics in these Puerto Rican catchments can be ascribed to changes in urban or forest area. The present results are in line with previous studies of mesoand macro-scale (sub-)tropical catchments, which generally found no significant change in Q that can be attributed to changes in forest cover. Possible explanations for the lack of a clear signal may include errors in the land cover, climate, Q, and/or catchment boundary data; changes in forest area occurring mainly in the less rainy lowlands; and heterogeneity in catchment response. Different results were obtained for different catchments, and using a smaller subset of catchments could have led to very different conclusions. This highlights the importance of including multiple catchments in land-cover impact analysis at the mesoscale.

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“…Moreover, some soils contain significant soil C even below 3 meters. For example, some tropical soils and many Histosols contain as much C below 1 m as they do above 1 m (Eswaran et al 1993;Nepstad et al 1994). In general, highly weathered soils are often very deep (tens of meters) so that even very low C concentrations may add up to a large amount of stored C in the total (Sombroek et al 1993).…”

Section: Empirical Estimates Of Global Carbon Stocks In Soilsmentioning

confidence: 99%

Storage and Turnover of Organic Matter in Soil

Torn

Swanston

Castanha

et al. 2009

Biophysico‐Chemical Processes Involving Natural Nonliving Organic Matter in Environmental Systems

114

107

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The role of deep roots in the hydrological and carbon cycles of Amazonian forests and pastures

Cited by 1,255 publications

References 19 publications

Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5)

Implementing and Evaluating Variable Soil Thickness in the Community Land Model, Version 4.5 (CLM4.5)

The impact of forest regeneration on streamflow in 12 mesoscale humid tropical catchments

Storage and Turnover of Organic Matter in Soil

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