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Soil Ecosystem Services at Statewide and Catchment Scales: A Climate Change Perspective.

Record Type:	Electronic resources : Monograph/item
Title/Author:	Soil Ecosystem Services at Statewide and Catchment Scales: A Climate Change Perspective./
Author:	Devine, Scott.
Published:	Ann Arbor : ProQuest Dissertations & Theses, : 2019,
Description:	158 p.
Notes:	Source: Dissertations Abstracts International, Volume: 81-03, Section: B.
Contained By:	Dissertations Abstracts International81-03B.
Subject:	Soil sciences. -
Online resource:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=13811900
ISBN:	9781085795012

Soil Ecosystem Services at Statewide and Catchment Scales: A Climate Change Perspective.
Devine, Scott.

Soil Ecosystem Services at Statewide and Catchment Scales: A Climate Change Perspective. - Ann Arbor : ProQuest Dissertations & Theses, 2019 - 158 p.

Source: Dissertations Abstracts International, Volume: 81-03, Section: B.

Thesis (Ph.D.)--University of California, Davis, 2019.

This item must not be sold to any third party vendors.

Ecosystem services are the mostly unpaid and often unrecognized work natural systems do to support and enrich human life. The objective of this dissertation was to improve understanding of and highlight several ecosystem services provided by California soils, water, and agroecosystems. The studies were undertaken at two scales (statewide and catchment) in both cultivated (perennial crops) and relatively unmanaged (rangeland) landscapes. Results are discussed from a climate change perspective.In the first chapter, green water (soil stored rainfall) was quantified at statewide scale for five irrigated perennial crops (alfalfa, almonds, grapes, pistachios, and walnuts) that cover 1.46 million hectares, approximately 50% of California's irrigated landscape and representing a multi-billion dollar industry. The study objective was to evaluate green water use in irrigated agriculture as a possible opportunity to enhance water security for farmers while providing several wider environmental benefits (e.g., more water for fish, less energy needed to pump water, and fewer nitrates leached to groundwater). Using the FAO-56 dual crop coefficient model, open-source software, and integration of several statewide public datasets, I tested different rooting depths and irrigation management thresholds (allowable depletion) to determine how size of the soil water reservoir affects green water utilization and, consequently, blue water demand (irrigation). The 13-year cumulative green water utilization ranged from 17-36 million km3 out of a 57 km3 rainfall input and 162-263 km3 cumulative blue water demand. Deeper rooting or greater allowable depletion reduced blue water demand more than the increase in green water utilization, due to less frequent irrigations, which reduced soil evaporative loss. Compared to a "business-as-usual" shallow irrigation management scenario (0.5 m rooting; 30% allowable depletion), a moderate scenario (1.0 m rooting; 50% allowable depletion) saved 30 km3 blue water evaporation and increased green water use by 7 km3 through 13 years. This was a 14% reduction in blue water demand with no increase in crop water stress, assuming crop roots can extract easily available, deeper soil water. Such savings would fill California's largest reservoir, Shasta Lake, 6.6 times. The study demonstrated an opportunity for climate-smart management of soil water storage, by delayed spring irrigation, applying deeper irrigations less often, and ending fall irrigation early.In the second and third chapters, the study focus switched to less intensively managed rangelands. Many California rangelands are located in foothill regions having a wide range of topographic characteristics with contrasting microclimates that strongly affect annual range production. However, few studies have examined the effect of topography on forage growth and compared these variations to differences in soil moisture availability, which is generally accepted as a major constraint to annual range production in California's Mediterranean climate. This study's objective was to improve our understanding of the relationship between microclimate and forage growth, an ecosystem provisioning service (food) that may be threatened by climate change. This ecosystem service currently supports California's fourth largest agricultural industry, the sale of cattle and calves, which grossed $3.6 billion in 2017. At a 10-ha catchment in a precipitation shadow of California's Central Coast Range, I tracked forage growth through two strongly contrasting precipitation years and monitored soil temperature and moisture at two depths (0-15 and 15-30 cm) in the root zone. The first growing season (2016-17) was wet with 287 mm precipitation producing an average 2790 kg ha−1 peak standing forage while plant available soil water storage at 0-15 cm was greater than half full for 80% of the growing season (Dec 1-Apr 15). The second growing season (2017-18) was dry with 123 mm precipitation producing an average 970 kg ha−1 peak standing forage. Plant available water storage was more than half full for only 29% and 11% of the dry growing season at 0-15 and 15-30 cm, respectively. Among topographic positions, peak forage production ranged from 462-1496 kg ha−1 in the dry year compared to 1597-4570 kg ha−1 in the wet year. Differences in aspect drove 3-10 °C soil temperature differences through both growing seasons and were amplified in the dry year. In the wet year, forage growth through early March appeared energy limited (i.e., light and temperature) and warmer sites produced more forage (360 kg ha−1 °C−1). By mid-April, late season growth was associated with moister sites that were not necessarily cooler. In the dry year, the warmest locations showed reduced forage production until late season rainfall in March. Linear models that included an interaction between soil moisture and temperature explained about half of the variance in forage growth during rapid growth periods. Wet periods favored the warmer south-facing locations, but production suffered more in this location during mid-winter droughts. These findings have implications for drought monitoring in rangelands and climate change modeling, revealing catchment scale differences in microclimate and dynamically shifting relationships to forage growth.In the third chapter, I continued work in the same 10-ha Central Coast rangeland catchment but with a new study focus: soil organic carbon (SOC) storage, an ecosystem regulating service. Accurate assessments of SOC stocks are needed at multiple scales given their importance to both local soil health and global C cycles. Rangelands cover 54% of California, representing a large stock of SOC, but existing SOC estimates are uncertain. The objective of this study was to improve understanding of fine-resolution SOC patterns in complex terrain to provide guidance to rangeland SOC inventories. I grid sampled 105 locations (21-m grid cells) at two depths (0-10 and 10-30 cm) across the catchment. Soils were analyzed for bulk density, coarse fragments, SOC, and texture. An unmanned aerial vehicle was used to gather monthly site imagery (30-cm resolution) to compare surface reflectance during two contrasting growing seasons (wet vs dry) to SOC patterns. The top 30 cm of soil held 3.64 ± 0.71 kg SOC m−2 (mean ± SD) with a range of 1.97-5.49 kg SOC m−2. The 0-10 cm soil layer stored 47% of the 0-30 cm SOC stock because of more concentrated SOC (1.40 ± 0.38%), twice that in the 10-30 cm layer (0.71 ± 0.15% SOC). Lower hillslope positions, concave landforms, and enhanced greenness were associated with more SOC (0-30 cm) and each explained 11, 24, and 31% of variability in SOC stocks, respectively. Multiple linear regression (MLR) models explained 50-53% of SOC variability at 0-30 and 10-30 cm, but only 15% of variability at 0-10 cm, and revealed a negative association between south-facing locations and SOC. In cross-validation tests, MLR outperformed spatial interpolation methods and Random Forest models, best explaining SOC patterns with five environmental co-variates: wet year greenness, mean curvature, elevation, annual clear sky insolation, and slope. This study demonstrates that a fine-resolution, regional scale SOC map of California rangelands needs to consider microclimatic and topographic controls on SOC at the catchment scale, in addition to broader scale mineralogical and macroclimatic controls discovered in previous SOC studies. Finally, given the association between SOC and forage growth patterns, future possible shifts in forage productivity (Chapter 2) would be expected to feedback and impact SOC stocks in California rangelands.

ISBN: 9781085795012Subjects--Topical Terms:

2122699
Soil sciences.
Subjects--Index Terms:

Annual rangeland

Soil Ecosystem Services at Statewide and Catchment Scales: A Climate Change Perspective.
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300 $a 158 p.
500 $a Source: Dissertations Abstracts International, Volume: 81-03, Section: B.
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502 $a Thesis (Ph.D.)--University of California, Davis, 2019.
506 $a This item must not be sold to any third party vendors.
520 $a Ecosystem services are the mostly unpaid and often unrecognized work natural systems do to support and enrich human life. The objective of this dissertation was to improve understanding of and highlight several ecosystem services provided by California soils, water, and agroecosystems. The studies were undertaken at two scales (statewide and catchment) in both cultivated (perennial crops) and relatively unmanaged (rangeland) landscapes. Results are discussed from a climate change perspective.In the first chapter, green water (soil stored rainfall) was quantified at statewide scale for five irrigated perennial crops (alfalfa, almonds, grapes, pistachios, and walnuts) that cover 1.46 million hectares, approximately 50% of California's irrigated landscape and representing a multi-billion dollar industry. The study objective was to evaluate green water use in irrigated agriculture as a possible opportunity to enhance water security for farmers while providing several wider environmental benefits (e.g., more water for fish, less energy needed to pump water, and fewer nitrates leached to groundwater). Using the FAO-56 dual crop coefficient model, open-source software, and integration of several statewide public datasets, I tested different rooting depths and irrigation management thresholds (allowable depletion) to determine how size of the soil water reservoir affects green water utilization and, consequently, blue water demand (irrigation). The 13-year cumulative green water utilization ranged from 17-36 million km3 out of a 57 km3 rainfall input and 162-263 km3 cumulative blue water demand. Deeper rooting or greater allowable depletion reduced blue water demand more than the increase in green water utilization, due to less frequent irrigations, which reduced soil evaporative loss. Compared to a "business-as-usual" shallow irrigation management scenario (0.5 m rooting; 30% allowable depletion), a moderate scenario (1.0 m rooting; 50% allowable depletion) saved 30 km3 blue water evaporation and increased green water use by 7 km3 through 13 years. This was a 14% reduction in blue water demand with no increase in crop water stress, assuming crop roots can extract easily available, deeper soil water. Such savings would fill California's largest reservoir, Shasta Lake, 6.6 times. The study demonstrated an opportunity for climate-smart management of soil water storage, by delayed spring irrigation, applying deeper irrigations less often, and ending fall irrigation early.In the second and third chapters, the study focus switched to less intensively managed rangelands. Many California rangelands are located in foothill regions having a wide range of topographic characteristics with contrasting microclimates that strongly affect annual range production. However, few studies have examined the effect of topography on forage growth and compared these variations to differences in soil moisture availability, which is generally accepted as a major constraint to annual range production in California's Mediterranean climate. This study's objective was to improve our understanding of the relationship between microclimate and forage growth, an ecosystem provisioning service (food) that may be threatened by climate change. This ecosystem service currently supports California's fourth largest agricultural industry, the sale of cattle and calves, which grossed $3.6 billion in 2017. At a 10-ha catchment in a precipitation shadow of California's Central Coast Range, I tracked forage growth through two strongly contrasting precipitation years and monitored soil temperature and moisture at two depths (0-15 and 15-30 cm) in the root zone. The first growing season (2016-17) was wet with 287 mm precipitation producing an average 2790 kg ha−1 peak standing forage while plant available soil water storage at 0-15 cm was greater than half full for 80% of the growing season (Dec 1-Apr 15). The second growing season (2017-18) was dry with 123 mm precipitation producing an average 970 kg ha−1 peak standing forage. Plant available water storage was more than half full for only 29% and 11% of the dry growing season at 0-15 and 15-30 cm, respectively. Among topographic positions, peak forage production ranged from 462-1496 kg ha−1 in the dry year compared to 1597-4570 kg ha−1 in the wet year. Differences in aspect drove 3-10 °C soil temperature differences through both growing seasons and were amplified in the dry year. In the wet year, forage growth through early March appeared energy limited (i.e., light and temperature) and warmer sites produced more forage (360 kg ha−1 °C−1). By mid-April, late season growth was associated with moister sites that were not necessarily cooler. In the dry year, the warmest locations showed reduced forage production until late season rainfall in March. Linear models that included an interaction between soil moisture and temperature explained about half of the variance in forage growth during rapid growth periods. Wet periods favored the warmer south-facing locations, but production suffered more in this location during mid-winter droughts. These findings have implications for drought monitoring in rangelands and climate change modeling, revealing catchment scale differences in microclimate and dynamically shifting relationships to forage growth.In the third chapter, I continued work in the same 10-ha Central Coast rangeland catchment but with a new study focus: soil organic carbon (SOC) storage, an ecosystem regulating service. Accurate assessments of SOC stocks are needed at multiple scales given their importance to both local soil health and global C cycles. Rangelands cover 54% of California, representing a large stock of SOC, but existing SOC estimates are uncertain. The objective of this study was to improve understanding of fine-resolution SOC patterns in complex terrain to provide guidance to rangeland SOC inventories. I grid sampled 105 locations (21-m grid cells) at two depths (0-10 and 10-30 cm) across the catchment. Soils were analyzed for bulk density, coarse fragments, SOC, and texture. An unmanned aerial vehicle was used to gather monthly site imagery (30-cm resolution) to compare surface reflectance during two contrasting growing seasons (wet vs dry) to SOC patterns. The top 30 cm of soil held 3.64 ± 0.71 kg SOC m−2 (mean ± SD) with a range of 1.97-5.49 kg SOC m−2. The 0-10 cm soil layer stored 47% of the 0-30 cm SOC stock because of more concentrated SOC (1.40 ± 0.38%), twice that in the 10-30 cm layer (0.71 ± 0.15% SOC). Lower hillslope positions, concave landforms, and enhanced greenness were associated with more SOC (0-30 cm) and each explained 11, 24, and 31% of variability in SOC stocks, respectively. Multiple linear regression (MLR) models explained 50-53% of SOC variability at 0-30 and 10-30 cm, but only 15% of variability at 0-10 cm, and revealed a negative association between south-facing locations and SOC. In cross-validation tests, MLR outperformed spatial interpolation methods and Random Forest models, best explaining SOC patterns with five environmental co-variates: wet year greenness, mean curvature, elevation, annual clear sky insolation, and slope. This study demonstrates that a fine-resolution, regional scale SOC map of California rangelands needs to consider microclimatic and topographic controls on SOC at the catchment scale, in addition to broader scale mineralogical and macroclimatic controls discovered in previous SOC studies. Finally, given the association between SOC and forage growth patterns, future possible shifts in forage productivity (Chapter 2) would be expected to feedback and impact SOC stocks in California rangelands.
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