Energy balance and water use in a subtropical karst woodland on the Edwards Plateau, Texas

Heilman, J. L.; McInnes, Kevin J.; Kjelgaard, Jim; Owens, M. K.; Schwinning, Susanne

doi:10.1016/j.jhydrol.2009.05.007

Cited by 67 publications

(57 citation statements)

References 27 publications

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“…Changes in land use and land cover -and even the impoundment of small reservoirs -have had negligible impacts on streamflow. These results confirm and add new insight to other research showing that woody plants in this region are shallow rooted and do not rely on deeper, perennial water sources (Heilman, 2009;Schwartz et al, 2013;Schwinning, 2008). It is still not understood why base flow showed a proportional increase .…”

Section: Rainfall and Runoff Trendssupporting

confidence: 88%

Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

Berg

Marcantonio

McAlister

et al. 2016

Hydrol. Earth Syst. Sci.

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Abstract. Rangelands cover a large portion of the earth's land surface and are undergoing dramatic landscape changes. At the same time, these ecosystems face increasing expectations to meet growing water supply needs. To address major gaps in our understanding of rangeland hydrologic function, we investigated historical watershed-scale runoff and sediment yield in a dynamic landscape in central Texas, USA. We quantified the relationship between precipitation and runoff and analyzed reservoir sediment cores dated using cesium-137 and lead-210 radioisotopes. Local rainfall and streamflow showed no directional trend over a period of 85 years, resulting in a rainfall-runoff ratio that has been resilient to watershed changes. Reservoir sedimentation rates generally were higher before 1963, but have been much lower and very stable since that time. Our findings suggest that (1) rangeland water yields may be stable over long periods despite dramatic landscape changes while (2) these same landscape changes influence sediment yields that impact downstream reservoir storage. Relying on rangelands to meet water needs demands an understanding of how these dynamic landscapes function and a quantification of the physical processes at work.

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Section: Rainfall and Runoff Trendssupporting

confidence: 88%

Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

Berg

Marcantonio

McAlister

et al. 2016

Hydrol. Earth Syst. Sci.

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“…If deep soil moisture is available, the tree species may switch their water-use patterns but this is probably not common. In a community level study of energy balance on same site as this study, Heilman et al (2009) found that there was no evidence that woody vegetation had access to deep soil moisture and community level evapotranspiration decreased during drought. Our measurements of species level responses showed that oak trees exhibited the greatest percentage decrease in transpiration during the dry periods and may have been the main contributor to the community level responses.…”

Section: Seasonal and Environmental Influences On Gas Exchangementioning

confidence: 47%

Carbon exchange and water loss from two evergreen trees in a semiarid woodland

Bendevis¹,

Owens²,

Heilman³

et al. 2009

Ecohydrology

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Ashe juniper (Juniperus ashei Buchholz) has encroached into the historical grasslands of the Edwards Plateau, an environmentally sensitive area that serves as the recharge zone for the Edwards Aquifer. An understanding of gas exchange and water relations of the two dominant tree species, Ashe juniper and live oak (Quercus virginiana P. Mill. var. fusiformis), is important to assess the trade-offs between potential aquifer recharge and carbon storage during woody plant encroachment. Over a 12-month period, juniper consistently had lower instantaneous carbon assimilation, transpiration rates and stomatal conductance than live oak. Oak exhibited greater seasonal variation and a greater correlation with antecedent precipitation in gas exchange measurements, whereas juniper did not respond to precipitation events. The consistent low rates of gas exchange and stomatal responses in juniper could indicate shallower rooting structure and/or limitation of hydraulic conductivity, as well as lower photosynthetic capacity. The higher rates of photosynthesis, transpiration and stomatal conductance exhibited by live oak during drought suggest alternate sources of soil moisture and possibly a deeper rooting pattern than Ashe juniper. Water-use efficiency was greater for juniper than for live oak suggesting that juniper may sequester more carbon than oak trees for a given amount of water. This finding implies that Ashe juniper may not be the extravagant water user previously reported but may serve an important role in carbon sequestration.

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“…Consequently, vegetation exerts a strong impact upon water flux (Zhang et al ., ; Huxman et al ., ) by controlling the spatial and temporal dynamics of ET. Direct quantification of water flux confirmed that annual ET was usually 35–85 mm higher in woodlands than in adjacent grasslands in the Edwards Plateau of Texas in the USA (Dugas et al ., ; Heilman et al ., ; Banta and Slattery, ). Using energy balance approaches, Liu et al .…”

Section: Introductionmentioning

confidence: 97%

Alteration of hydrological processes and streamflow with juniper (Juniperus virginiana) encroachment in a mesic grassland catchment

et al. 2013

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To understand the effect of woody plant encroachment on hydrological processes of mesic grasslands, we quantified infiltration capacity in situ, the temporal changes in soil water storage, and streamflow of a grassland catchment and a catchment heavily encroached by juniper (Juniperus virginiana, eastern redcedar) in previously cultivated, non‐karst substrate grasslands in north‐central Oklahoma for 3 years. The initial and steady‐state infiltration rates under the juniper canopy were nearly triple to that of the grassland catchment and were intermediate in the intercanopy spaces within the encroached catchment. Soil water content and soil water storage on the encroached catchment were generally lower than on the grassland catchment, especially when preceding the seasons of peak rainfall in spring and fall. Frequency and magnitude of streamflow events were reduced in the encroached catchment. Annual runoff coefficients for the encroached catchment averaged 2.1%, in contrast to 10.6% for the grassland catchment. Annual streamflow duration ranged from 80 to 250 h for the encroached catchment compared with 600 to 800 h for the grassland catchment. Our results showed that the encroachment of juniper into previously cultivated mesic grasslands fundamentally alters catchment hydrological function. Rapid transformation of mesic grassland to a woodland state with juniper encroachment, if not confined, has the potential to drastically reduce soil water, streamflow and flow duration of ephemeral streams in the Southern Great Plains. Copyright © 2013 John Wiley & Sons, Ltd.

show abstract

Energy balance and water use in a subtropical karst woodland on the Edwards Plateau, Texas

Cited by 67 publications

References 27 publications

Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

Contrasting watershed-scale trends in runoff and sediment yield complicate rangeland water resources planning

Carbon exchange and water loss from two evergreen trees in a semiarid woodland

Alteration of hydrological processes and streamflow with juniper (Juniperus virginiana) encroachment in a mesic grassland catchment

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