Ecological assessment of energy and carbon pathways in swards of Bromus tectorum L. on contrasting slope exposures

Hinds, W.T.

doi:10.2172/4249321

Cited by 2 publications

(4 citation statements)

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“…The slopes, facing north and south at an angle of 40° ± 1° with the horizontal, were seeded with Bromus tectorum shortly after the mound was constructed in autumn 1971. A full tabulation of experimental details and data is available (Hinds 1974).…”

Section: Site Descriptionmentioning

confidence: 99%

“…Calculated in this manner, all errors from the other measurements were lumped into this flux. Evapotranspiration was measured with smalllysimeters developed during the past 3 yr (Hinds 1973) from a Russian design (Konstantinov 1966) . The construction of the small lysimeters is shown in Fig.…”

Section: ••Heavy Felt Stripmentioning

confidence: 99%

“…An annular gasket of pliable 1.5-mm thick neoprene covered the gap between the lysimeter and the sleeve, and four felt gaskets about 6 mm (% in) thick taped around the lysimeter provided baffles to prevent vertical air motions along the outer surfaces of the lysimeter. Temperature profiles inside the lysimeter were indistinguishable from those in the field, and comparisons of water loss and cheatgrass production with field data showed no significant differences (Hinds 1973). The lysimeters were weighed at 4-to 8-day intervals on a portable scale to ± 5 g ( ± 0.4 mm water); more frequent weighings are not optimal for soil water budget methods (Rouse andWilson 1971/1972).…”

Section: ••Heavy Felt Stripmentioning

confidence: 99%

“…A change in transpiration rate on both exposures was related to the amount of soil water remaining in the profile. Figure 10 shows the temporal coincidence on each exposure of a change of rate of transpiration with a change in the fraction of available energy used for transpiration at the same soil-water content (in the 60-cm profile) of about 7.5 cm 3 cm-2 , or 10%, using a bulk density of 1.25 g cm-3 (Hinds 1973). Ritchie et al (1972) described similar results for corn and cotton, but with the ratio of evapotranspiration to net radiation near unity, rather than about 0.4 as in Fig.…”

Section: Water Relationsmentioning

confidence: 99%

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Energy and Carbon Balances in Cheatgrass: An Essay in Autecology

Hinds¹

1975

Ecological Monographs

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Biotic and abiotic pathways of incident energy are rarely considered together in comparable detail, so little is known about whether energy or carbon relations remain constant in contrasting energy environments. An experiment to determine the fates of energy and carbon in cheatgrass (Bromus tectorum L.) was carried out on steep (40°) north— and south—facing slopes on a small earth mound, using many small lysimeters to emulate swards of cheatgrass. Meteorological conditions and energy fluxes that were measured included air and soil temperatures, relative humidity, wind speed, incoming and reflected shortwave radiation, net all—wave radiation, heat flux to the soil, and evaporation and transpiration separately. The fate of photosynthetically fixed carbon during spring growth (31 March to 31 May) was determined by separation of the plant tissues into mineral nutrients, ash, crude protein, crude fat, crude fiber, and nitrogen—free extract (NFE) (the proximate analysis scheme routinely used for feed analysis) for roots, shoots, and seeds separately. Temperatures and humidities were not notably different between slopes. However, all terms in the radiation balances were significantly larger on the south exposure, and the sensible heat flux to the atmosphere on the south exposure was much greater than on the north. The energy—saturated south exposure was subjected to water stresses much earlier than the north exposure. Total transpired water, the fraction of energy used to transpire water, and soil water content simultaneously showed an abrupt decrease in slope at about 10% soil water content (—14 bars average water potential) in the 60—cm lysimeter soil profile, indicating a rather sudden decrease in water availability to the plants. This change occurred near day 30 on the south exposure, and near day 45 on the north exposure, implying that water was readily available to the north exposure for about 2 wk longer than on the south exposure. Root and seed production were both about 30% greater on the north exposure than on the south, but shoot production was not different. Heats of combustion (caloric content) differed between roots, shoots, and seeds, but not between exposures. Total production and total energy fixation were not statistically different on the two exposures, because the greater biomass and variability of the shoots overwhelmed the statistically significant differences in roots and seeds. Incident shortwave radiation was very much greater on the south exposure than on the north, so the south exposure was much less efficient in converting solar energy into chemical energy stored in plant tissues. The clearest difference in carbon pathways occurred for crude protein in shoot tissues at the end of the growing season (23 g m—2 on the north compared to 30 g m—2 on the south). Since both exposures began the growing season with 33 g m—2, shoot protein was translocated to other tissues during the season, to a greater extent on the north exposure than on the south. The crude fiber and NFE (g m—2) in seed tissues were...

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Section: Site Descriptionmentioning

confidence: 99%

Section: ••Heavy Felt Stripmentioning

confidence: 99%