Jon D. Hanson | None (original) (raw)
Papers by Jon D. Hanson
Ecological Modelling, 1999
spur (Simulation of Production and Utilization of Rangelands) is a grassland ecosystem simulation... more spur (Simulation of Production and Utilization of Rangelands) is a grassland ecosystem simulation model. spur2.4 integrates all previous versions of spur. The changes from spur91 make the model more applicable to the southern Great Plains. The forage submodel from spur2 predicts forage intake and diet selection by grazing herbivores, and the cow-calf submodel from spur2 simulates all individuals in a herd for their full life cycle, based on defined genetic traits. The soil organic matter submodel from century was added to improve soil carbon and nitrogen cycling. spur2.4 output is compared with observed values from the Texas Experimental Ranch, Throckmorton, Texas. The changes made in creating spur2.4 have considerably improved the utility and accuracy of the spur model for north Texas. Soil moisture predictions are improved (spur91 is 137% and spur2.4 is 106% of observed, R=0.79–0.86), but run-off is still not adequate (R=0.65–0.76) and monthly evaporation is lower (spur91 is 94% and spur2.4 is 95%) than observed. Soil carbon level predictions by the century submodel are within range of the data, and output is stable over the simulation period. Predictions of individual plant species productivity compared with observed data are improved with spur2.4 (R=0.79–0.98). Between-season plant growth and long-term persistence are simulated well. The addition of the century soil organic matter submodel increased nitrogen level predictions resulting in more accurate predictions of animal weight gain. Steer weight gains are typical for north Texas. Simulation of cow-calf mass was good (R>0.98) as was production per hectare and per cow. The addition of the cow-calf model increases the utility of the model. The paper identifies portions of the model that need further validation and field research to improve model utility and credibility for use in natural resource management.
assessing the impact of management practices on multiple agroecosystem functions.
Journal of Range Management, 2002
Rangeland plant productivity and species composition are affected by moisture availability and gr... more Rangeland plant productivity and species composition are affected by moisture availability and grazing intensity. We examined warm-and cool-season grass productivity and relative dis-
Advances in Agroecology, 2009
concentrations and on external CO2 and N supplies. We studied the lard, 1997). effect of CO2 and ... more concentrations and on external CO2 and N supplies. We studied the lard, 1997). effect of CO2 and N supply on reserve remobilization during the first The effects of elevated atmospheric CO2 on plant 20 d following defoliation of 9-wk-old alfalfa (Medicago sativa L.), growth and tissue composition have been extensively western wheatgrass (Pascopyrum smithii (Rydb) A. Love), and blue studied. However, few studies have examined the inter- grama (Bouteloua gracilis (H.B.K.) Lag ex Steud). plants. Reserve action between elevated CO2 and defoliation. Elevated remobilization was studied in controlled-environment chambers set atmospheric CO 2 commonly increases TNC in plant tis- at either ambient (350 mmol mol 21 ) or elevated (700 mmol mol 21 ) sues and reduces N concentration (Baur-Hoch et al., CO2. Plants were fertilized twice weekly with Hoaglands solution 1990; Korner and Miglietta, 1994; Wilsey, 1996). Carbo- containing either 0 mg L 21 (low N) or 400 mg L 21 N (high N). Elevated CO2 i...
Soil Biology and Biochemistry, 2003
Soil Biology and Biochemistry, 2002
... Soil at these upland sites belonged to the WernerSenChama complex (loamy, mixed, superactiv... more ... Soil at these upland sites belonged to the WernerSenChama complex (loamy, mixed, superactive, frigid shallow Entic Haplustoll; fine-silty ... The model goodness-of-fit was evaluated by calculating the percentage difference (%D) between the observed (O) and predicted (P) soil ...
Rangeland Ecology & Management, 2005
A modeling approach that assesses impacts of alternative management decisions prior to field impl... more A modeling approach that assesses impacts of alternative management decisions prior to field implementation would reduce decision-making risk for rangeland and livestock production system managers. However, the accuracy and functionality of models should be verified before they are used as decision-making tools. The goal of this study was to evaluate the functionality of the Great Plains Framework for Agricultural Resource Management (GPFARM) model in simulating forage and cow-calf production in the central Great Plains. The forage production module was tested in shortgrass prairie using April-October monthly biomass values from 2000 through 2002 for warm-season grasses (WSG), cool-season grasses (CSG), shrubs, and forbs. The forage module displayed excellent (99% explained variance) agreement in the 2001 calibration year in tracking growth and senescence trends of WSG and CSG, which constitute the vast majority of the aboveground biomass. Less agreement (35%-39% explained variance) was observed for shrubs and forbs. The model-explained variances of biomass in 2000 and 2002 (verification years) were 80% for WSG, 67% for CSG, 78% for shrubs, and 82% for forbs. Further development is needed to improve predicted plant response to environmental stresses. The cow-calf production module was tested in northern mixed-grass prairie using June-November monthly average cow and calf weights from 1996 through 2001 for March-calving, moderately stocked Hereford pairs. Overall, GPFARM performed well and tracked cow (81% explained variance) and calf (94% explained variance) pre-and postweaning weights. The GPFARM model has functional utility for simulating forage and cow-calf production with satisfactory accuracy at semiarid-temperate sites, such as southeastern Wyoming and northeastern Colorado. Continued development will focus on improving plant response to environmental stresses and testing the model's functionality as a decision support tool for strategic and tactical ranch management.
Journal of Plant Nutrition, 2012
Calcium (Ca) and nitrogen (N) treatments (2, 8, and 32 mg L) were investigated on aboveground and... more Calcium (Ca) and nitrogen (N) treatments (2, 8, and 32 mg L) were investigated on aboveground and belowground growth of switchgrass (Panicum virgatum L.) and intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth & D.R. Dewey] in a greenhouse experiment. Switchgrass (cultivars ‘Sunburst’ and ‘Dacotah’), and intermediate wheatgrass (cultivar ‘Reliant’) aboveground and belowground biomass were harvested and analyzed to determine total biomass,
Journal of Environment Quality, 2009
Microbial production and consumption of greenhouse gases (GHG) is infl uenced by temperature and ... more Microbial production and consumption of greenhouse gases (GHG) is infl uenced by temperature and nutrients, especially during the fi rst few weeks after agricultural fertilization. Th e eff ect of fertilization on GHG fl uxes should occur during and shortly after application, yet data indicating how application timing aff ects both GHG fl uxes and crop yields during a growing season are lacking. We designed a replicated (n = 5) fi eld experiment to test for the short-term eff ect of fertilizer application timing on fl uxes of methane (CH 4 ), carbon dioxide (CO 2 ), and nitrous oxide (N 2 O) over a growing season in the northern Great Plains. Each 0.30-ha plot was planted to maize (Zea mays L.) and treated similarly with the exception of fertilizer timing: fi ve plots were fertilized with urea in early spring (1 April) and fi ve plots were fertilized with urea in late spring (13 May). We hypothesized time-integrated fl uxes over a growing season would be greater for the late-spring treatment, resulting in a greater net GHG fl ux, as compared to the earlyspring treatment. Data collected on 59 dates and integrated over a 5-mo time course indicated CO 2 fl uxes were greater (P < 0.0001) and CH 4 fl uxes were lower (P < 0.05) for soils fertilized in late spring. Net GHG fl ux was also signifi cantly aff ected by treatment, with 0.84 ± 0.11 kg CO 2 equivalents m −2 for early spring and 1.04 ± 0.13 kg CO 2 equivalents m −2 for late spring. Nitrous oxide fl uxes, however, were similar for both treatments. Results indicate fertilizer application timing infl uences net GHG emissions in dryland cropping systems.
Ecological Modelling, 1992
Baker, B.B., Bourdon, R.M. and Hanson, J.D., 1992. FORAGE: a model of forage intake in beef cattl... more Baker, B.B., Bourdon, R.M. and Hanson, J.D., 1992. FORAGE: a model of forage intake in beef cattle. Ecol. Modelling, 60: 257-279.
Crop Science, 1999
that N remobilization continued for a longer period of time when N supply was limited. However, w... more that N remobilization continued for a longer period of time when N supply was limited. However, when reserve Early regrowth following defoliation of forage species often de-N supplies were depleted by weekly defoliations, little pends on remobilization of nitrogen and non-structural carbohydrate (TNC) reserves stored in roots and crowns. The degree to which TNC or no N was remobilized from reserves, so that shoot and N remobilization contribute to regrowth can depend on internal growth relied solely on new uptake (Thornton and Milconcentrations and on external CO 2 and N supplies. We studied the lard, 1997). effect of CO 2 and N supply on reserve remobilization during the first The effects of elevated atmospheric CO 2 on plant 20 d following defoliation of 9-wk-old alfalfa (Medicago sativa L.), growth and tissue composition have been extensively western wheatgrass [Pascopyrum smithii (Rydb) A. Love], and blue studied. However, few studies have examined the intergrama [Bouteloua gracilis (H.B.K.) Lag ex Steud]. plants. Reserve action between elevated CO 2 and defoliation. Elevated remobilization was studied in controlled-environment chambers set atmospheric CO 2 commonly increases TNC in plant tisat either ambient (350 mol mol Ϫ1 ) or elevated (700 mol mol Ϫ1 ) sues and reduces N concentration (Baur-Hoch et al., CO 2 . Plants were fertilized twice weekly with Hoaglands solution Korner and Miglietta, 1994;. Carbocontaining either 0 mg L Ϫ1 (low N) or 400 mg L Ϫ1 N (high N). Elevated CO 2 increased the total amount and percent of available TNC that hydrate remobilization after defoliation can also inwas remobilized in alfalfa, and the amount of remobilized TNC in crease under elevated CO 2 (Baur-Hoch et al., 1990). western wheatgrass, but reduced TNC remobilization in blue grama.
Crop Science, 2001
CO 2 . Repeated defoliation decreased CO 2 -in-Little work has been done to assess the impact of ... more CO 2 . Repeated defoliation decreased CO 2 -in-Little work has been done to assess the impact of elevated CO 2 duced growth enhancements in grasses (Hunt et al., on responses of forages to defoliation. This study examines regrowth, 1995) and in Lolium perenne L. (Hebeisen et al., 1997) biomass partitioning, and labile C and N metabolites in three functional plant-types: a C 3 grass [Pascopyrum smithii (Rydb.) A. Love], under nutrient-limited conditions. However, when nua C 4 grass [Bouteloua gracilis (H.B.K.) Lag.], and a forage legume trients were abundant, positive CO 2 -induced growth en-(Medicago sativa L.). Plants were grown from seed, defoliated twice, hancements were maintained under defoliation. These and grown in a controlled environment under a factorial arrangement results indicate the importance of soil nutrients in susof two CO 2 [low CO 2 (LC), 355 mol mol Ϫ1 , and high CO 2 (HC), 700 taining CO 2 -induced growth responses of forages, espemol mol Ϫ1 ] and two N nutrition regimes [low N (LN), watered twice cially when subject to defoliation. weekly with half-strength Hoagland's containing 0 N, and high N The partitioning of biomass between above-and be-(HN), half-strength Hoagland's containing 14 mM N]. High N enlow-ground organs in response to environmental perturhanced regrowth in all three species, while high CO 2 enhanced rebations like CO 2 is another important plant trait that growth only in the two C 3 species. In M. sativa, CO 2 and N treatments has been studied extensively, but little information exists had no significant effect on k, the allometric growth coefficient. In contrast, k was reduced in P. smithii plants grown under LN (0.63) on how defoliation might interact with CO 2 and affect compared with HN (0.99). In B. gracilis, low N also reduced k, but partitioning. The enhanced plant growth that generally it interacted with CO 2 so that k was greatest for plants grown at HN/ occurs under elevated CO 2 concentrations is often ac-HC (0.95) and HN/LC (0.89), intermediate at LN/LC (0.58), and least companied by shifts in biomass partitioning, often (alat LN/HC (0.44). These results indicate greater partitioning to belowthough not always) with increased partitioning of bioground organs (reduced k ) when N is limiting, particularly under mass to belowground organs (Bazzaz, 1990; Rogers et elevated CO 2 . Significant correlations were established between k and al. , 1994, 1996). Several researchers (Campagna and several measures of plant N status, suggesting that the effects of CO 2
Plant and soil, 1999
Plant and Soil 210: 1120, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. .... more Plant and Soil 210: 1120, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. ... Nitrogen uptake and partitioning under alternate-and every-furrow irrigation ... R. Howard Skinner ∗ , Jon D. Hanson and Joseph G. Benjamin USDA-ARS, Pasture ...
Plant and soil, 1998
Plant and Soil 199: 187194, 1998. © 1998 Kluwer Academic Publishers. Printed in the Netherlands.... more Plant and Soil 199: 187194, 1998. © 1998 Kluwer Academic Publishers. Printed in the Netherlands. ... Root distribution following spatial separation of water and nitrogen supply in furrow irrigated corn ... R. Howard Skinner, Jon D. Hanson and Joseph G. Benjamin ...
![Research paper thumbnail of Erratum to “Cattle grazing behavior with season-long free-choice access to four forage types” [Appl. Anim. Behav. Sci. 78 (2002) 29–42]](https://attachments.academia-assets.com/46661477/thumbnails/1.jpg)
](Applied Animal Behaviour Science, 2003
Erratum Erratum to ''Cattle grazing behavior with season-long free-choice access to four forage t... more Erratum Erratum to ''Cattle grazing behavior with season-long free-choice access to four forage types'' [Appl. Anim. Behav. Sci. 78 (2002) 29-42] $
Applied Animal Behaviour Science, 2002
This experiment investigated how season-long, free-choice grazing affected weekly cattle grazing ... more This experiment investigated how season-long, free-choice grazing affected weekly cattle grazing behavior and resource use. Our objectives were to determine if known forage preferences change through the season, if feedbacks from previous grazing intensity affect current use, and if resources such as water and salt in combination with a shorter forage base increase grazing time compared to previously rested pasture. Two replicate 24.4-ha grazing enclosures contained four forage types: smooth bromegrass (Bromus inermis), crested wheatgrass (Agropyron desertorum), western wheatgrass (Pascopyrum smithii) and native range. Each forage type was divided into three sub-areas containing either: a water source, a salt block, or forage deferred from use before the experiment (rested). Resource use was tracked with analysis of aerial photos of the pastures before and after the 3-year study and with weekly direct observation of animal use of each area of the pastures. As each season progressed, use of smooth bromegrass declined and use of crested wheatgrass and western wheatgrass increased. Use of native range remained relatively constant and low throughout the study. The previously rested sub-areas of the replicate pastures had signi®cantly and substantially more grazing than those with salt or water. Signi®cant auto-correlation in the data was well described by an auto-regressive parameter comprised of the sum of the previous 2 weeks grazing time, which showed gradual shifts in forage preference from 1 week to the next. Aerial photo analysis supported the ®ndings of the behavioral data; preference between forage types changed over time, and grazing use within pastures was uneven and negatively correlated with salt and water sites. Cattle can rotate themselves among various pasture types if given free-choice; and season-long grazing may be an effective system if a variety of forage types are available. # (J.S. Fehmi).
Agriculture, Ecosystems & Environment, 2006
Grazing management affects ecosystem function through impacts on soil condition. We investigated ... more Grazing management affects ecosystem function through impacts on soil condition. We investigated the effects of long-term (over 70 years) grazing on soil properties and nitrous oxide (N 2 O) emission within a moderately grazed native vegetation pasture (MGP), heavily grazed native vegetation pasture (HGP), and a fertilized crested wheatgrass (Agropyron desertorum (Fisch. ex. Link) Schult.) pasture (FCWP) near Mandan, ND, USA. Grazing-induced changes in species composition and N fertilizer application contributed to differences in soil properties and N 2 O emission between pastures. Soil organic C (SOC) was 5.7 Mg ha À1 greater in FCWP and HGP than MGP at 0-5 cm, whereas HGP had 2.4 Mg ha À1 more SOC than FCWP and MGP at 5-10 cm. At 30-60 cm, SOC in FCWP was 4.0 and 7.5 Mg ha À1 greater than in HGP and MGP, respectively. Particulate organic matter (POM) C and N in the surface 5 cm of FCWP were three-and five-fold greater, respectively, than in HGP and MGP. Acidification from N fertilization in FCWP decreased soil pH and cation exchange capacity compared to HGP and MGP in the surface 5 cm. Annual N 2 O emission was over three-fold greater in FCWP compared to HGP and MGP, and was positively associated with POM-C across all pastures (P 0.0001; r 2 = 0.85). Results from this study suggest fertilized crested wheatgrass enhances deep storage of SOC, but contributes to surface acidification and greater N 2 O emission relative to native non-fertilized pastures in the northern Great Plains. #
Ecological Modelling, 1999
spur (Simulation of Production and Utilization of Rangelands) is a grassland ecosystem simulation... more spur (Simulation of Production and Utilization of Rangelands) is a grassland ecosystem simulation model. spur2.4 integrates all previous versions of spur. The changes from spur91 make the model more applicable to the southern Great Plains. The forage submodel from spur2 predicts forage intake and diet selection by grazing herbivores, and the cow-calf submodel from spur2 simulates all individuals in a herd for their full life cycle, based on defined genetic traits. The soil organic matter submodel from century was added to improve soil carbon and nitrogen cycling. spur2.4 output is compared with observed values from the Texas Experimental Ranch, Throckmorton, Texas. The changes made in creating spur2.4 have considerably improved the utility and accuracy of the spur model for north Texas. Soil moisture predictions are improved (spur91 is 137% and spur2.4 is 106% of observed, R=0.79–0.86), but run-off is still not adequate (R=0.65–0.76) and monthly evaporation is lower (spur91 is 94% and spur2.4 is 95%) than observed. Soil carbon level predictions by the century submodel are within range of the data, and output is stable over the simulation period. Predictions of individual plant species productivity compared with observed data are improved with spur2.4 (R=0.79–0.98). Between-season plant growth and long-term persistence are simulated well. The addition of the century soil organic matter submodel increased nitrogen level predictions resulting in more accurate predictions of animal weight gain. Steer weight gains are typical for north Texas. Simulation of cow-calf mass was good (R>0.98) as was production per hectare and per cow. The addition of the cow-calf model increases the utility of the model. The paper identifies portions of the model that need further validation and field research to improve model utility and credibility for use in natural resource management.
assessing the impact of management practices on multiple agroecosystem functions.
Journal of Range Management, 2002
Rangeland plant productivity and species composition are affected by moisture availability and gr... more Rangeland plant productivity and species composition are affected by moisture availability and grazing intensity. We examined warm-and cool-season grass productivity and relative dis-
Advances in Agroecology, 2009
concentrations and on external CO2 and N supplies. We studied the lard, 1997). effect of CO2 and ... more concentrations and on external CO2 and N supplies. We studied the lard, 1997). effect of CO2 and N supply on reserve remobilization during the first The effects of elevated atmospheric CO2 on plant 20 d following defoliation of 9-wk-old alfalfa (Medicago sativa L.), growth and tissue composition have been extensively western wheatgrass (Pascopyrum smithii (Rydb) A. Love), and blue studied. However, few studies have examined the inter- grama (Bouteloua gracilis (H.B.K.) Lag ex Steud). plants. Reserve action between elevated CO2 and defoliation. Elevated remobilization was studied in controlled-environment chambers set atmospheric CO 2 commonly increases TNC in plant tis- at either ambient (350 mmol mol 21 ) or elevated (700 mmol mol 21 ) sues and reduces N concentration (Baur-Hoch et al., CO2. Plants were fertilized twice weekly with Hoaglands solution 1990; Korner and Miglietta, 1994; Wilsey, 1996). Carbo- containing either 0 mg L 21 (low N) or 400 mg L 21 N (high N). Elevated CO2 i...
Soil Biology and Biochemistry, 2003
Soil Biology and Biochemistry, 2002
... Soil at these upland sites belonged to the WernerSenChama complex (loamy, mixed, superactiv... more ... Soil at these upland sites belonged to the WernerSenChama complex (loamy, mixed, superactive, frigid shallow Entic Haplustoll; fine-silty ... The model goodness-of-fit was evaluated by calculating the percentage difference (%D) between the observed (O) and predicted (P) soil ...
Rangeland Ecology & Management, 2005
A modeling approach that assesses impacts of alternative management decisions prior to field impl... more A modeling approach that assesses impacts of alternative management decisions prior to field implementation would reduce decision-making risk for rangeland and livestock production system managers. However, the accuracy and functionality of models should be verified before they are used as decision-making tools. The goal of this study was to evaluate the functionality of the Great Plains Framework for Agricultural Resource Management (GPFARM) model in simulating forage and cow-calf production in the central Great Plains. The forage production module was tested in shortgrass prairie using April-October monthly biomass values from 2000 through 2002 for warm-season grasses (WSG), cool-season grasses (CSG), shrubs, and forbs. The forage module displayed excellent (99% explained variance) agreement in the 2001 calibration year in tracking growth and senescence trends of WSG and CSG, which constitute the vast majority of the aboveground biomass. Less agreement (35%-39% explained variance) was observed for shrubs and forbs. The model-explained variances of biomass in 2000 and 2002 (verification years) were 80% for WSG, 67% for CSG, 78% for shrubs, and 82% for forbs. Further development is needed to improve predicted plant response to environmental stresses. The cow-calf production module was tested in northern mixed-grass prairie using June-November monthly average cow and calf weights from 1996 through 2001 for March-calving, moderately stocked Hereford pairs. Overall, GPFARM performed well and tracked cow (81% explained variance) and calf (94% explained variance) pre-and postweaning weights. The GPFARM model has functional utility for simulating forage and cow-calf production with satisfactory accuracy at semiarid-temperate sites, such as southeastern Wyoming and northeastern Colorado. Continued development will focus on improving plant response to environmental stresses and testing the model's functionality as a decision support tool for strategic and tactical ranch management.
Journal of Plant Nutrition, 2012
Calcium (Ca) and nitrogen (N) treatments (2, 8, and 32 mg L) were investigated on aboveground and... more Calcium (Ca) and nitrogen (N) treatments (2, 8, and 32 mg L) were investigated on aboveground and belowground growth of switchgrass (Panicum virgatum L.) and intermediate wheatgrass [Thinopyrum intermedium (Host) Barkworth &amp;amp;amp;amp;amp;amp; D.R. Dewey] in a greenhouse experiment. Switchgrass (cultivars ‘Sunburst’ and ‘Dacotah’), and intermediate wheatgrass (cultivar ‘Reliant’) aboveground and belowground biomass were harvested and analyzed to determine total biomass,
Journal of Environment Quality, 2009
Microbial production and consumption of greenhouse gases (GHG) is infl uenced by temperature and ... more Microbial production and consumption of greenhouse gases (GHG) is infl uenced by temperature and nutrients, especially during the fi rst few weeks after agricultural fertilization. Th e eff ect of fertilization on GHG fl uxes should occur during and shortly after application, yet data indicating how application timing aff ects both GHG fl uxes and crop yields during a growing season are lacking. We designed a replicated (n = 5) fi eld experiment to test for the short-term eff ect of fertilizer application timing on fl uxes of methane (CH 4 ), carbon dioxide (CO 2 ), and nitrous oxide (N 2 O) over a growing season in the northern Great Plains. Each 0.30-ha plot was planted to maize (Zea mays L.) and treated similarly with the exception of fertilizer timing: fi ve plots were fertilized with urea in early spring (1 April) and fi ve plots were fertilized with urea in late spring (13 May). We hypothesized time-integrated fl uxes over a growing season would be greater for the late-spring treatment, resulting in a greater net GHG fl ux, as compared to the earlyspring treatment. Data collected on 59 dates and integrated over a 5-mo time course indicated CO 2 fl uxes were greater (P < 0.0001) and CH 4 fl uxes were lower (P < 0.05) for soils fertilized in late spring. Net GHG fl ux was also signifi cantly aff ected by treatment, with 0.84 ± 0.11 kg CO 2 equivalents m −2 for early spring and 1.04 ± 0.13 kg CO 2 equivalents m −2 for late spring. Nitrous oxide fl uxes, however, were similar for both treatments. Results indicate fertilizer application timing infl uences net GHG emissions in dryland cropping systems.
Ecological Modelling, 1992
Baker, B.B., Bourdon, R.M. and Hanson, J.D., 1992. FORAGE: a model of forage intake in beef cattl... more Baker, B.B., Bourdon, R.M. and Hanson, J.D., 1992. FORAGE: a model of forage intake in beef cattle. Ecol. Modelling, 60: 257-279.
Crop Science, 1999
that N remobilization continued for a longer period of time when N supply was limited. However, w... more that N remobilization continued for a longer period of time when N supply was limited. However, when reserve Early regrowth following defoliation of forage species often de-N supplies were depleted by weekly defoliations, little pends on remobilization of nitrogen and non-structural carbohydrate (TNC) reserves stored in roots and crowns. The degree to which TNC or no N was remobilized from reserves, so that shoot and N remobilization contribute to regrowth can depend on internal growth relied solely on new uptake (Thornton and Milconcentrations and on external CO 2 and N supplies. We studied the lard, 1997). effect of CO 2 and N supply on reserve remobilization during the first The effects of elevated atmospheric CO 2 on plant 20 d following defoliation of 9-wk-old alfalfa (Medicago sativa L.), growth and tissue composition have been extensively western wheatgrass [Pascopyrum smithii (Rydb) A. Love], and blue studied. However, few studies have examined the intergrama [Bouteloua gracilis (H.B.K.) Lag ex Steud]. plants. Reserve action between elevated CO 2 and defoliation. Elevated remobilization was studied in controlled-environment chambers set atmospheric CO 2 commonly increases TNC in plant tisat either ambient (350 mol mol Ϫ1 ) or elevated (700 mol mol Ϫ1 ) sues and reduces N concentration (Baur-Hoch et al., CO 2 . Plants were fertilized twice weekly with Hoaglands solution Korner and Miglietta, 1994;. Carbocontaining either 0 mg L Ϫ1 (low N) or 400 mg L Ϫ1 N (high N). Elevated CO 2 increased the total amount and percent of available TNC that hydrate remobilization after defoliation can also inwas remobilized in alfalfa, and the amount of remobilized TNC in crease under elevated CO 2 (Baur-Hoch et al., 1990). western wheatgrass, but reduced TNC remobilization in blue grama.
Crop Science, 2001
CO 2 . Repeated defoliation decreased CO 2 -in-Little work has been done to assess the impact of ... more CO 2 . Repeated defoliation decreased CO 2 -in-Little work has been done to assess the impact of elevated CO 2 duced growth enhancements in grasses (Hunt et al., on responses of forages to defoliation. This study examines regrowth, 1995) and in Lolium perenne L. (Hebeisen et al., 1997) biomass partitioning, and labile C and N metabolites in three functional plant-types: a C 3 grass [Pascopyrum smithii (Rydb.) A. Love], under nutrient-limited conditions. However, when nua C 4 grass [Bouteloua gracilis (H.B.K.) Lag.], and a forage legume trients were abundant, positive CO 2 -induced growth en-(Medicago sativa L.). Plants were grown from seed, defoliated twice, hancements were maintained under defoliation. These and grown in a controlled environment under a factorial arrangement results indicate the importance of soil nutrients in susof two CO 2 [low CO 2 (LC), 355 mol mol Ϫ1 , and high CO 2 (HC), 700 taining CO 2 -induced growth responses of forages, espemol mol Ϫ1 ] and two N nutrition regimes [low N (LN), watered twice cially when subject to defoliation. weekly with half-strength Hoagland's containing 0 N, and high N The partitioning of biomass between above-and be-(HN), half-strength Hoagland's containing 14 mM N]. High N enlow-ground organs in response to environmental perturhanced regrowth in all three species, while high CO 2 enhanced rebations like CO 2 is another important plant trait that growth only in the two C 3 species. In M. sativa, CO 2 and N treatments has been studied extensively, but little information exists had no significant effect on k, the allometric growth coefficient. In contrast, k was reduced in P. smithii plants grown under LN (0.63) on how defoliation might interact with CO 2 and affect compared with HN (0.99). In B. gracilis, low N also reduced k, but partitioning. The enhanced plant growth that generally it interacted with CO 2 so that k was greatest for plants grown at HN/ occurs under elevated CO 2 concentrations is often ac-HC (0.95) and HN/LC (0.89), intermediate at LN/LC (0.58), and least companied by shifts in biomass partitioning, often (alat LN/HC (0.44). These results indicate greater partitioning to belowthough not always) with increased partitioning of bioground organs (reduced k ) when N is limiting, particularly under mass to belowground organs (Bazzaz, 1990; Rogers et elevated CO 2 . Significant correlations were established between k and al. , 1994, 1996). Several researchers (Campagna and several measures of plant N status, suggesting that the effects of CO 2
Plant and soil, 1999
Plant and Soil 210: 1120, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. .... more Plant and Soil 210: 1120, 1999. © 1999 Kluwer Academic Publishers. Printed in the Netherlands. ... Nitrogen uptake and partitioning under alternate-and every-furrow irrigation ... R. Howard Skinner ∗ , Jon D. Hanson and Joseph G. Benjamin USDA-ARS, Pasture ...
Plant and soil, 1998
Plant and Soil 199: 187194, 1998. © 1998 Kluwer Academic Publishers. Printed in the Netherlands.... more Plant and Soil 199: 187194, 1998. © 1998 Kluwer Academic Publishers. Printed in the Netherlands. ... Root distribution following spatial separation of water and nitrogen supply in furrow irrigated corn ... R. Howard Skinner, Jon D. Hanson and Joseph G. Benjamin ...
Applied Animal Behaviour Science, 2003
Erratum Erratum to ''Cattle grazing behavior with season-long free-choice access to four forage t... more Erratum Erratum to ''Cattle grazing behavior with season-long free-choice access to four forage types'' [Appl. Anim. Behav. Sci. 78 (2002) 29-42] $
Applied Animal Behaviour Science, 2002
This experiment investigated how season-long, free-choice grazing affected weekly cattle grazing ... more This experiment investigated how season-long, free-choice grazing affected weekly cattle grazing behavior and resource use. Our objectives were to determine if known forage preferences change through the season, if feedbacks from previous grazing intensity affect current use, and if resources such as water and salt in combination with a shorter forage base increase grazing time compared to previously rested pasture. Two replicate 24.4-ha grazing enclosures contained four forage types: smooth bromegrass (Bromus inermis), crested wheatgrass (Agropyron desertorum), western wheatgrass (Pascopyrum smithii) and native range. Each forage type was divided into three sub-areas containing either: a water source, a salt block, or forage deferred from use before the experiment (rested). Resource use was tracked with analysis of aerial photos of the pastures before and after the 3-year study and with weekly direct observation of animal use of each area of the pastures. As each season progressed, use of smooth bromegrass declined and use of crested wheatgrass and western wheatgrass increased. Use of native range remained relatively constant and low throughout the study. The previously rested sub-areas of the replicate pastures had signi®cantly and substantially more grazing than those with salt or water. Signi®cant auto-correlation in the data was well described by an auto-regressive parameter comprised of the sum of the previous 2 weeks grazing time, which showed gradual shifts in forage preference from 1 week to the next. Aerial photo analysis supported the ®ndings of the behavioral data; preference between forage types changed over time, and grazing use within pastures was uneven and negatively correlated with salt and water sites. Cattle can rotate themselves among various pasture types if given free-choice; and season-long grazing may be an effective system if a variety of forage types are available. # (J.S. Fehmi).
Agriculture, Ecosystems & Environment, 2006
Grazing management affects ecosystem function through impacts on soil condition. We investigated ... more Grazing management affects ecosystem function through impacts on soil condition. We investigated the effects of long-term (over 70 years) grazing on soil properties and nitrous oxide (N 2 O) emission within a moderately grazed native vegetation pasture (MGP), heavily grazed native vegetation pasture (HGP), and a fertilized crested wheatgrass (Agropyron desertorum (Fisch. ex. Link) Schult.) pasture (FCWP) near Mandan, ND, USA. Grazing-induced changes in species composition and N fertilizer application contributed to differences in soil properties and N 2 O emission between pastures. Soil organic C (SOC) was 5.7 Mg ha À1 greater in FCWP and HGP than MGP at 0-5 cm, whereas HGP had 2.4 Mg ha À1 more SOC than FCWP and MGP at 5-10 cm. At 30-60 cm, SOC in FCWP was 4.0 and 7.5 Mg ha À1 greater than in HGP and MGP, respectively. Particulate organic matter (POM) C and N in the surface 5 cm of FCWP were three-and five-fold greater, respectively, than in HGP and MGP. Acidification from N fertilization in FCWP decreased soil pH and cation exchange capacity compared to HGP and MGP in the surface 5 cm. Annual N 2 O emission was over three-fold greater in FCWP compared to HGP and MGP, and was positively associated with POM-C across all pastures (P 0.0001; r 2 = 0.85). Results from this study suggest fertilized crested wheatgrass enhances deep storage of SOC, but contributes to surface acidification and greater N 2 O emission relative to native non-fertilized pastures in the northern Great Plains. #