Astrid Volder - Academia.edu (original) (raw)
Papers by Astrid Volder
Cultivar evaluations for drought tolerance and irrigation management are very important in water-... more Cultivar evaluations for drought tolerance and irrigation management are very important in water-limited, arid regions of the United States. This study was conducted to investigate the effect of deficit irrigation (50% vs. 100% crop evapotranspiration, ETc) on three melon (Cucumis melo L.) cultivars (Mission and Da Vinci, reticulatus type and Super Nectar, inodorus type). Overall, deficit irrigation significantly reduced photosynthetic rate (Pn) by 30% and stomatal conductance (gs) by 21%. The highest average Pn (20.53 µmol·m-2·s-1 of CO2) and gs (0.31 mol·m-2·s-1 of H2O) were recorded in Mission and Super Nectar, respectively. Transpiration rate and leaf water use efficiency were not significantly affected by either irrigation or cultivar. Throughout the development period, physiological traits were affected by cultivar and irrigation regimes. At fruit set Pn and gs were reduced with deficit irrigation in all cultivars but recovered only in cv. Da Vinci. Deficit irrigation signific...
In multispecies systems, facilitation and complementarity can offset some of the negative effects... more In multispecies systems, facilitation and complementarity can offset some of the negative effects of interspecies competition. This can lead to more efficient use of resources by the plant community as a whole, resulting in an increase in productivity. Overyielding, a phenomenon whereby plant production in mixture exceeds that of production in monoculture, has been attributed to complementary use of resources by different plant functional types. Different combinations of peanut, watermelon, okra, cowpea and pepper in single crop and various intercropping combinations were investigated in a low-input organic system in Texas. Each species was selected to perform a specific function within the system. Results from land equivalent ratio (LER) and per plant production calculations show that the intercropping combination with peanut, watermelon and okra (Wpwo) and peanut, watermelon, okra and cowpea (Wpwoc) consistently overyielded and performed the best overall in both 2011 and 2012. Pla...
Placing impermeable pavement around existing trees can cause declines in tree growth and health d... more Placing impermeable pavement around existing trees can cause declines in tree growth and health due to reduced water infiltration and soil surface gas exchange.Using pervious concrete, with greater water infiltration and gas permeability, could be a good alternative. The purpose of this study was to test soil respiration, root growth and soil extract chemistry in root zones of American sweetgum (Liquidambar styraciflua) as affected by pavement. The experimental setup consisted of twenty-five sweetgum trees, with root zones covered by standard concrete (five plots), pervious concrete (10 plots) or left uncovered (control, 10 plots). Each plot was outfitted with access points for soil respiration measurements. Soil respiration was measured monthly on two access holes per plot, with three sub-measurements per access hole. Data collected from February 2008 to January 2009 indicated that soil respiration correlated with seasonal soil temperatures. We observed tremendous variability in so...
Ecosystem services have been defined as the benefits that human populations derive directly or in... more Ecosystem services have been defined as the benefits that human populations derive directly or indirectly from ecosystem functions. These services range from the obvious, such as provision of food and fiber and timber for homes, to the less obvious, such as microbial nutrient cycling in soil and environmental cooling by vegetation. This chapter discusses the services, resources, and benefits provided in natural and human dominated ecosystems.
Humans significantly affect their ecosystem. Nowhere is this more evident than in our towns and c... more Humans significantly affect their ecosystem. Nowhere is this more evident than in our towns and cities around the world. We have options when it comes to the sustainability of our cities. We have to pay attention to meeting the needs of today without compromising the needs of the future. However, to truly understand those options, we need to have the best knowledge available so that we can make the best decisions possible. It has everything to do with the stewardship of our natural resources, while at the same time using those resources to meet the needs of today’s urban population. This volume deals with the impacts of urbanization on the environment— soils, air, and water quality, the animals and humans who live there—and offers some solutions to contemporary problems. Its coverage exemplifies the wide range of specialties in the agronomic sciences and shows how scientists define ecosystem functions and solve problems. To read this book will give instruction in how agronomy, an ar...
Agriculture Ecosystems & Environment
The presence of vegetation is thought to reduce loss of soil substrate after roof installation; h... more The presence of vegetation is thought to reduce loss of soil substrate after roof installation; however, few attempts have been made to quantify this effect. Twelve green roof modules placed at a 2% slope were used to quantify the effect of wind, precipitation intensity ,vegetation and vegetation type on modular green roof substrate depth. The presence of vegetation reduced substrate loss immediately after installation of equipment, yet had little effect on substrate depth once the substrate had settled. Neither wind speed nor precipitation rate had a direct effect on substrate depth, although after some large rainfall events substrate depth increased due to media expansion caused by the retained water. Overall we observed negligible substrate depth decrease, regardless of vegetation presence, wind speed or precipitation intensity.
Green roofs can improve urban environments by reducing the amount of runoff and in some cases imp... more Green roofs can improve urban environments by reducing the amount of runoff and in some cases improve the quality of runoff leaving urban areas. Water quality and soil chemistry of four green roofs in Houston that harvest and recycle rainwater and irrigation runoff were investigated. The green roofs vary in age from 2.5 to 8 years. Continuous recycling of water is expected to decrease soil and water quality and in turn decrease plant productivity. Soil cores, irrigation samples, and runoff samples were collected and analyzed. Preliminary irrigation samples indicate that the sodium absorption ratios (SAR) are below 2 which are not concerning. Electrical conductivity is relativley high (450, 450 475, 300 µS/cm respective of age) in the irrigation water compared to the soil (all below 200 µS/cm). Soil organic matter percentage was rather high for a green roof substrate ranging from 15% to 18%. Other nutrient concentrations in the soil do not appear to be high enough to become problemat...
ABSTRACT Background/Question/Methods Crop rotations during the heat of Texas’ summers are limited... more ABSTRACT Background/Question/Methods Crop rotations during the heat of Texas’ summers are limited due to the poor availability of crops that can withstand the high temperatures. Additionally, management practices that enhance or sustain soil and crop productivity while reducing inputs can increase producer profit and reduce the potential for nutrient runoff and leaching. We are currently investigating different combinations of watermelon, peanut, okra, cowpea and pepper in single crop and various intercropping combinations and their effects on ecosystem services and plant productivity. Each component crop was selected to perform a specific function within the system. Specifically, we are assessing the effects of plant functional diversity on soil temperature, soil moisture, and soil health (organic matter content, microbial C and N, total and organic C and N) in a system following strict organic guidelines. A randomized complete block design with 3 replicates was utilized for this study. Results/Conclusions Although data analysis is ongoing, preliminary observations suggest that intercropping combinations utilizing watermelon reduce soil temperatures and promote short-term soil moisture retention. Temperatures were reduced by between 2 and 3°C on average and short-term soil moisture retention was increase by 25% VWC in these treatments. Okra benefited most from intercropping when compared to its monocrop with an increase in soil moisture content of 46% VWC. Contradictory to our hypothesized outcome, preliminary results from soil microbial biomass analysis suggest a decrease in soil microbial C in the intercropping combination of peanut, watermelon and okra as compared to peanut, watermelon and okra grown in monocrop, 701, 940, 955 and 1161 µg C/g dry soil respectively. There was no significant difference in soil microbial N between the 4 treatments. We are currently conducting root trait analysis in addition to analyzing other soil chemistry parameters to help explain these observations. The preliminary information gathered from this investigation has the potential for alleviating heat and soil moisture stress on crops during the peak of the summer heat in Texas. However, the potential effects of these systems on soil health and nutrient cycling have yet to be conclusively determined from this study.
Ecological Studies, 2005
... Mechanistic modeling using an optimization or cost-benefit approach can be a powerful tool in... more ... Mechanistic modeling using an optimization or cost-benefit approach can be a powerful tool in ... required for root con-struction, growth, ion uptake and maintenance, as well as costs associated with ... 8.2.4 Variation in Root Life Span in Different Environments and Among Species ...
Urban Forestry & Urban Greening, 2011
Journal of Plant Nutrition, 2013
ABSTRACT We conducted a study to determine if inoculation with arbuscular mycorrhizal fungi (AMF)... more ABSTRACT We conducted a study to determine if inoculation with arbuscular mycorrhizal fungi (AMF) would enhance the tolerance of vinca [Catharanthus roseus (L.) G. Don] plants to sodium chloride (NaCl)-induced salinity in irrigation water. Vinca tolerated salinity levels up to 40 mM. Chlorophyll concentration, proline synthesis, and total antioxidant activity were increased with saline irrigation, while leaf potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and boron (B) content decreased, suggesting a detrimental salinity effect. Despite the limited effect of increasing salinity on N content, NaCl-stressed vinca plants showed a marked decrease in nitrate reductase activity, which was associated with decreased leaf K and Fe total content. Mycorrhizal inoculation resulted in reduced growth when compared to non-AMF plants, regardless of salinity level. The K/sodium (Na) ratio decreased dramatically with increasing salinity regardless of AMF treatment. Suggesting, that the AMF isolate was not able to selectively uptake K and Ca, and avoid uptake of Na.
Global Change Biology, 2012
Global Change Biology, 2010
Global Change Biology, 2013
Pecan is an important nut crop grown throughout much of the southern U.S, with New Mexico, Georgi... more Pecan is an important nut crop grown throughout much of the southern U.S, with New Mexico, Georgia, and Texas ranked as the leading producers. The commercial pecan nursery industry currently relies on improved cultivars grafted on rootstocks derived from open-pollinated seeds. Seedstocks are chosen in relation to their geographical origin and general historical performance as rootstocks. Despite the fact that certain seedstocks are recommended more than others for particular soil or climate conditions, little is known about the physiology of known rootstock cultivars of pecan. An experiment was conducted to investigate the physiological differences between two open-pollinated pecan seedlings (Apache and Elliott) grown in field conditions. Traditionally, ‘Apache' has been recommended for the dryer regions of the pecan producing area, whereas ‘Elliott' is more frequently used in the more humid southeast. The study was conducted from May to September 2007 on rain-fed, six-year-...
Journal of the American Society for Horticultural Science. American Society for Horticultural Science
Increased continuous irrigation due to drought conditions and above average temperatures, and res... more Increased continuous irrigation due to drought conditions and above average temperatures, and resulting salt buildup in soils, can lead to a decline in yields in salt-sensitive species such as watermelon. This greenhouse investigation is phase one of a two-phase study aimed at assessing the potential benefits of utilizing halophytic species as companion crops to watermelon in salt-affected soils. From this initial screening, two species will be selected for intercropping with watermelon in a field setting. Based on a set of criteria, the six species chosen for this screening were four-wing saltbush (Atriplex halimus), barley (Hordeum vulgare), garden orache (Atriplex hortensis), purslane (Portulaca oleracea), saltwort (Suaeda salsa), and wheat (Triticum aestivum). Treatments of 0, 3, and 6 dS/m irrigation water were applied to plants over a 5-week period and plant species were replicated 5 times within each treatment level in a randomized complete-block design. Preliminary results f...
Journal of the American Society for Horticultural Science. American Society for Horticultural Science
After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illi... more After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illinoinensis) trees in 2010, an experiment was conducted to evaluate the consequences of the injury on carbon assimilation and photosynthetic efficiency, and, in particular, to assess if low-to-moderate injury induces a compensatory increase in photosynthesis. Gas exchange and light-adapted fluorescence were measured on non-injured portions of the leaflet lamina adjacent to the injured area as well as on portions of leaflets that included leafminer injury. Results indicate that damage of the photosynthetic apparatus did not extend beyond the injured areas by leafminers. Furthermore, although a strong relationship between the proportion of leafminer injury and area-based net CO2 assimilation rate of injured leaflet tissue was found, there was no evidence that pecan leaves were able to compensate for leafminer injury by upregulating CO2 assimilation in leaflet tissue that was unaffected.
Cultivar evaluations for drought tolerance and irrigation management are very important in water-... more Cultivar evaluations for drought tolerance and irrigation management are very important in water-limited, arid regions of the United States. This study was conducted to investigate the effect of deficit irrigation (50% vs. 100% crop evapotranspiration, ETc) on three melon (Cucumis melo L.) cultivars (Mission and Da Vinci, reticulatus type and Super Nectar, inodorus type). Overall, deficit irrigation significantly reduced photosynthetic rate (Pn) by 30% and stomatal conductance (gs) by 21%. The highest average Pn (20.53 µmol·m-2·s-1 of CO2) and gs (0.31 mol·m-2·s-1 of H2O) were recorded in Mission and Super Nectar, respectively. Transpiration rate and leaf water use efficiency were not significantly affected by either irrigation or cultivar. Throughout the development period, physiological traits were affected by cultivar and irrigation regimes. At fruit set Pn and gs were reduced with deficit irrigation in all cultivars but recovered only in cv. Da Vinci. Deficit irrigation signific...
In multispecies systems, facilitation and complementarity can offset some of the negative effects... more In multispecies systems, facilitation and complementarity can offset some of the negative effects of interspecies competition. This can lead to more efficient use of resources by the plant community as a whole, resulting in an increase in productivity. Overyielding, a phenomenon whereby plant production in mixture exceeds that of production in monoculture, has been attributed to complementary use of resources by different plant functional types. Different combinations of peanut, watermelon, okra, cowpea and pepper in single crop and various intercropping combinations were investigated in a low-input organic system in Texas. Each species was selected to perform a specific function within the system. Results from land equivalent ratio (LER) and per plant production calculations show that the intercropping combination with peanut, watermelon and okra (Wpwo) and peanut, watermelon, okra and cowpea (Wpwoc) consistently overyielded and performed the best overall in both 2011 and 2012. Pla...
Placing impermeable pavement around existing trees can cause declines in tree growth and health d... more Placing impermeable pavement around existing trees can cause declines in tree growth and health due to reduced water infiltration and soil surface gas exchange.Using pervious concrete, with greater water infiltration and gas permeability, could be a good alternative. The purpose of this study was to test soil respiration, root growth and soil extract chemistry in root zones of American sweetgum (Liquidambar styraciflua) as affected by pavement. The experimental setup consisted of twenty-five sweetgum trees, with root zones covered by standard concrete (five plots), pervious concrete (10 plots) or left uncovered (control, 10 plots). Each plot was outfitted with access points for soil respiration measurements. Soil respiration was measured monthly on two access holes per plot, with three sub-measurements per access hole. Data collected from February 2008 to January 2009 indicated that soil respiration correlated with seasonal soil temperatures. We observed tremendous variability in so...
Ecosystem services have been defined as the benefits that human populations derive directly or in... more Ecosystem services have been defined as the benefits that human populations derive directly or indirectly from ecosystem functions. These services range from the obvious, such as provision of food and fiber and timber for homes, to the less obvious, such as microbial nutrient cycling in soil and environmental cooling by vegetation. This chapter discusses the services, resources, and benefits provided in natural and human dominated ecosystems.
Humans significantly affect their ecosystem. Nowhere is this more evident than in our towns and c... more Humans significantly affect their ecosystem. Nowhere is this more evident than in our towns and cities around the world. We have options when it comes to the sustainability of our cities. We have to pay attention to meeting the needs of today without compromising the needs of the future. However, to truly understand those options, we need to have the best knowledge available so that we can make the best decisions possible. It has everything to do with the stewardship of our natural resources, while at the same time using those resources to meet the needs of today’s urban population. This volume deals with the impacts of urbanization on the environment— soils, air, and water quality, the animals and humans who live there—and offers some solutions to contemporary problems. Its coverage exemplifies the wide range of specialties in the agronomic sciences and shows how scientists define ecosystem functions and solve problems. To read this book will give instruction in how agronomy, an ar...
Agriculture Ecosystems & Environment
The presence of vegetation is thought to reduce loss of soil substrate after roof installation; h... more The presence of vegetation is thought to reduce loss of soil substrate after roof installation; however, few attempts have been made to quantify this effect. Twelve green roof modules placed at a 2% slope were used to quantify the effect of wind, precipitation intensity ,vegetation and vegetation type on modular green roof substrate depth. The presence of vegetation reduced substrate loss immediately after installation of equipment, yet had little effect on substrate depth once the substrate had settled. Neither wind speed nor precipitation rate had a direct effect on substrate depth, although after some large rainfall events substrate depth increased due to media expansion caused by the retained water. Overall we observed negligible substrate depth decrease, regardless of vegetation presence, wind speed or precipitation intensity.
Green roofs can improve urban environments by reducing the amount of runoff and in some cases imp... more Green roofs can improve urban environments by reducing the amount of runoff and in some cases improve the quality of runoff leaving urban areas. Water quality and soil chemistry of four green roofs in Houston that harvest and recycle rainwater and irrigation runoff were investigated. The green roofs vary in age from 2.5 to 8 years. Continuous recycling of water is expected to decrease soil and water quality and in turn decrease plant productivity. Soil cores, irrigation samples, and runoff samples were collected and analyzed. Preliminary irrigation samples indicate that the sodium absorption ratios (SAR) are below 2 which are not concerning. Electrical conductivity is relativley high (450, 450 475, 300 µS/cm respective of age) in the irrigation water compared to the soil (all below 200 µS/cm). Soil organic matter percentage was rather high for a green roof substrate ranging from 15% to 18%. Other nutrient concentrations in the soil do not appear to be high enough to become problemat...
ABSTRACT Background/Question/Methods Crop rotations during the heat of Texas’ summers are limited... more ABSTRACT Background/Question/Methods Crop rotations during the heat of Texas’ summers are limited due to the poor availability of crops that can withstand the high temperatures. Additionally, management practices that enhance or sustain soil and crop productivity while reducing inputs can increase producer profit and reduce the potential for nutrient runoff and leaching. We are currently investigating different combinations of watermelon, peanut, okra, cowpea and pepper in single crop and various intercropping combinations and their effects on ecosystem services and plant productivity. Each component crop was selected to perform a specific function within the system. Specifically, we are assessing the effects of plant functional diversity on soil temperature, soil moisture, and soil health (organic matter content, microbial C and N, total and organic C and N) in a system following strict organic guidelines. A randomized complete block design with 3 replicates was utilized for this study. Results/Conclusions Although data analysis is ongoing, preliminary observations suggest that intercropping combinations utilizing watermelon reduce soil temperatures and promote short-term soil moisture retention. Temperatures were reduced by between 2 and 3°C on average and short-term soil moisture retention was increase by 25% VWC in these treatments. Okra benefited most from intercropping when compared to its monocrop with an increase in soil moisture content of 46% VWC. Contradictory to our hypothesized outcome, preliminary results from soil microbial biomass analysis suggest a decrease in soil microbial C in the intercropping combination of peanut, watermelon and okra as compared to peanut, watermelon and okra grown in monocrop, 701, 940, 955 and 1161 µg C/g dry soil respectively. There was no significant difference in soil microbial N between the 4 treatments. We are currently conducting root trait analysis in addition to analyzing other soil chemistry parameters to help explain these observations. The preliminary information gathered from this investigation has the potential for alleviating heat and soil moisture stress on crops during the peak of the summer heat in Texas. However, the potential effects of these systems on soil health and nutrient cycling have yet to be conclusively determined from this study.
Ecological Studies, 2005
... Mechanistic modeling using an optimization or cost-benefit approach can be a powerful tool in... more ... Mechanistic modeling using an optimization or cost-benefit approach can be a powerful tool in ... required for root con-struction, growth, ion uptake and maintenance, as well as costs associated with ... 8.2.4 Variation in Root Life Span in Different Environments and Among Species ...
Urban Forestry & Urban Greening, 2011
Journal of Plant Nutrition, 2013
ABSTRACT We conducted a study to determine if inoculation with arbuscular mycorrhizal fungi (AMF)... more ABSTRACT We conducted a study to determine if inoculation with arbuscular mycorrhizal fungi (AMF) would enhance the tolerance of vinca [Catharanthus roseus (L.) G. Don] plants to sodium chloride (NaCl)-induced salinity in irrigation water. Vinca tolerated salinity levels up to 40 mM. Chlorophyll concentration, proline synthesis, and total antioxidant activity were increased with saline irrigation, while leaf potassium (K), calcium (Ca), magnesium (Mg), iron (Fe), and boron (B) content decreased, suggesting a detrimental salinity effect. Despite the limited effect of increasing salinity on N content, NaCl-stressed vinca plants showed a marked decrease in nitrate reductase activity, which was associated with decreased leaf K and Fe total content. Mycorrhizal inoculation resulted in reduced growth when compared to non-AMF plants, regardless of salinity level. The K/sodium (Na) ratio decreased dramatically with increasing salinity regardless of AMF treatment. Suggesting, that the AMF isolate was not able to selectively uptake K and Ca, and avoid uptake of Na.
Global Change Biology, 2012
Global Change Biology, 2010
Global Change Biology, 2013
Pecan is an important nut crop grown throughout much of the southern U.S, with New Mexico, Georgi... more Pecan is an important nut crop grown throughout much of the southern U.S, with New Mexico, Georgia, and Texas ranked as the leading producers. The commercial pecan nursery industry currently relies on improved cultivars grafted on rootstocks derived from open-pollinated seeds. Seedstocks are chosen in relation to their geographical origin and general historical performance as rootstocks. Despite the fact that certain seedstocks are recommended more than others for particular soil or climate conditions, little is known about the physiology of known rootstock cultivars of pecan. An experiment was conducted to investigate the physiological differences between two open-pollinated pecan seedlings (Apache and Elliott) grown in field conditions. Traditionally, ‘Apache' has been recommended for the dryer regions of the pecan producing area, whereas ‘Elliott' is more frequently used in the more humid southeast. The study was conducted from May to September 2007 on rain-fed, six-year-...
Journal of the American Society for Horticultural Science. American Society for Horticultural Science
Increased continuous irrigation due to drought conditions and above average temperatures, and res... more Increased continuous irrigation due to drought conditions and above average temperatures, and resulting salt buildup in soils, can lead to a decline in yields in salt-sensitive species such as watermelon. This greenhouse investigation is phase one of a two-phase study aimed at assessing the potential benefits of utilizing halophytic species as companion crops to watermelon in salt-affected soils. From this initial screening, two species will be selected for intercropping with watermelon in a field setting. Based on a set of criteria, the six species chosen for this screening were four-wing saltbush (Atriplex halimus), barley (Hordeum vulgare), garden orache (Atriplex hortensis), purslane (Portulaca oleracea), saltwort (Suaeda salsa), and wheat (Triticum aestivum). Treatments of 0, 3, and 6 dS/m irrigation water were applied to plants over a 5-week period and plant species were replicated 5 times within each treatment level in a randomized complete-block design. Preliminary results f...
Journal of the American Society for Horticultural Science. American Society for Horticultural Science
After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illi... more After an outbreak of blotch leafminer (Cameraria caryaefoliella) on field-grown pecan (Carya illinoinensis) trees in 2010, an experiment was conducted to evaluate the consequences of the injury on carbon assimilation and photosynthetic efficiency, and, in particular, to assess if low-to-moderate injury induces a compensatory increase in photosynthesis. Gas exchange and light-adapted fluorescence were measured on non-injured portions of the leaflet lamina adjacent to the injured area as well as on portions of leaflets that included leafminer injury. Results indicate that damage of the photosynthetic apparatus did not extend beyond the injured areas by leafminers. Furthermore, although a strong relationship between the proportion of leafminer injury and area-based net CO2 assimilation rate of injured leaflet tissue was found, there was no evidence that pecan leaves were able to compensate for leafminer injury by upregulating CO2 assimilation in leaflet tissue that was unaffected.