**Arid Rangeland**

[57] CEM (Çölleşme ve Erozyonla Mücadele Genel Müdürlüğü). Ulusal İzleme Sistemlerimiz, Havza İzleme ve Değerlendirme Sistemi [Internet]. 2017. Available from: http://www. cem.gov.tr/erozyon/AnaSayfa/ulusal\_izleme\_sistemlerimiz.aspx?sflang=tr [Accessed:

[58] Dellal İ et al. İklim Değişikliğinin Tarım Sektörüne Ekonomik Yansımaları. In: TMMOB Ziraat Mühendisliği Odası, Türkiye Ziraat Mühendisliği VII. Teknik Kongresi Bildiriler

[59] Bayraç NH, Doğan E. Türkiye'de İklim Değişikliğinin Tarım Sektörü Üzerine Etkileri.

[60] Kellogg MCE, Thorp J. Soil Classification. Soils and Men: Yearbook of Agriculture.

[61] Anonymous. Tarım, Gıda ve Hayvancılık Bakanlığı [Internet]. 2017. Available from: http://www.tarim.gov.tr/Konular/Arazi-Toplulastirma-ve-Tarla-Ici-Gelistirme/Projeler

[62] Baldwin M, Kellogg CE, Thorp J. Soil Classification. Soils and Men: Yearbook of Agri-

[63] Rowe AJ, Mason RO, Dickel KE, Mann RB, Mockler RJ. Strategic Management: A

[64] Ommani AR. Strengths, weaknesses, opportunities and threats (SWOT) analysis for farming system businesses management: Case of wheat farmers of Shadervan District, Shoushtar Township, Iran. African Journal of Business Management. 2011;**5**(22):9448-9454

[65] Whalley A. Strategic Marketing. Andrew Whally and Ventus Publishing APS; 2010.

[66] Akça H. Assessment of rural tourism in Turkey using SWOT analysis. Journal of Applied

[67] Diamantopoulou P, Voudouris K. Optimization of water resources management using SWOT analysis: The case of Zakynthos Island, Ionian Sea, Greece. Environmental Geology.

[68] Sing N. SWOT analysis—A useful tool for community vision. Researcher. 2009;**1**(3):25-27

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Kitabı-1; Ankara. 2015. p. 62-80

[Accessed: 04-04-2017]

ISBN: 978-87-7681-643-8

2008;**54**(1):197-211

Sciences. 2006;**6**(13):2837-2839

**Chapter 2**

**Provisional chapter**

**Simulating the Productivity of Desert Woody Shrubs in**

**Simulating the Productivity of Desert Woody Shrubs in** 

In the southwestern U.S., many rangelands have converted from native grasslands to woody shrublands dominated by creosotebush (*Larrea tridentate*) and honey mesquite (*Prosopis glandulosa*), threatening ecosystem health. Both creosotebush and mesquite have well-developed long root systems that allow them to outcompete neighboring plants. Thus, control of these two invasive shrubs is essential for revegetation in arid rangelands. Simulation models are valuable tools for describing invasive shrub growth and interaction between shrubs and other perennial grasses and for evaluating quantitative changes in ecosystem properties linked to shrub invasion and shrub control. In this study, a hybrid and multiscale modeling approach with two process-based models, ALMANAC and APEX was developed. Through ALMANAC application, plant parameters and growth cycles of creosotebush and mesquite were characterized based on field data. The developed shrub growth curves and parameters were subsequently used in APEX to explore productivity and range condition at a larger field scale. APEX was used to quantitatively evaluate the effect of shrub reductions on vegetation and water and soil qualities in various topological conditions. The results of this study showed that this multi modeling approach is capable of accurately predicting the impacts of shrubs on soil water resources.

**Keywords:** arid rangeland, creosotebush, mesquite, ALMANAC, APEX

Rangelands cover 31% of the total land base of the U.S. and occur mostly in western regions [1]. Western rangelands are mostly in arid and semi-arid regions that are subject to low and variable precipitation, high evaporative demand, nutrient poor soils, high spatial and temporal variability in plant production, and low net primary production [2]. Arid and semi-arid rangelands

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

DOI: 10.5772/intechopen.73703

**Southwestern Texas**

**Southwestern Texas**

Sumin Kim, Jaehak Jeong and James R. Kiniry

Sumin Kim, Jaehak Jeong and James R. Kiniry

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.73703

**Abstract**

**1. Introduction**

#### **Simulating the Productivity of Desert Woody Shrubs in Southwestern Texas Simulating the Productivity of Desert Woody Shrubs in Southwestern Texas**

DOI: 10.5772/intechopen.73703

Sumin Kim, Jaehak Jeong and James R. Kiniry Sumin Kim, Jaehak Jeong and James R. Kiniry

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.73703

#### **Abstract**

In the southwestern U.S., many rangelands have converted from native grasslands to woody shrublands dominated by creosotebush (*Larrea tridentate*) and honey mesquite (*Prosopis glandulosa*), threatening ecosystem health. Both creosotebush and mesquite have well-developed long root systems that allow them to outcompete neighboring plants. Thus, control of these two invasive shrubs is essential for revegetation in arid rangelands. Simulation models are valuable tools for describing invasive shrub growth and interaction between shrubs and other perennial grasses and for evaluating quantitative changes in ecosystem properties linked to shrub invasion and shrub control. In this study, a hybrid and multiscale modeling approach with two process-based models, ALMANAC and APEX was developed. Through ALMANAC application, plant parameters and growth cycles of creosotebush and mesquite were characterized based on field data. The developed shrub growth curves and parameters were subsequently used in APEX to explore productivity and range condition at a larger field scale. APEX was used to quantitatively evaluate the effect of shrub reductions on vegetation and water and soil qualities in various topological conditions. The results of this study showed that this multi modeling approach is capable of accurately predicting the impacts of shrubs on soil water resources.

**Keywords:** arid rangeland, creosotebush, mesquite, ALMANAC, APEX

#### **1. Introduction**

Rangelands cover 31% of the total land base of the U.S. and occur mostly in western regions [1]. Western rangelands are mostly in arid and semi-arid regions that are subject to low and variable precipitation, high evaporative demand, nutrient poor soils, high spatial and temporal variability in plant production, and low net primary production [2]. Arid and semi-arid rangelands

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

are susceptible to desertification as the result of cumulative threats such as extreme weather events (e.g. drought), land use change (e.g. suburbanization), inappropriate land management (e.g. livestock overgrazing), and invasion by shrubs and other woody plants [3, 4]. Among these threats, plant invasions are considered as one of the most serious problems in much of the southwestern U.S. [5]. Encroachment of woody shrubs into grasslands has been commonly observed in the arid and semi-arid regions and often reported [6–9]. Encroachment can be defined as increasing density, cover and biomass of shrub and/or woody species in open canopy systems [8]. These woody shrubs are indigenous species that have increased in density or cover because of changes in climate variables (i.e. warmer and more humid conditions), land use modifications, or decreased frequency of disturbance regimes [8, 10, 11]. Extensive expansion of shrubs and woody plant into grasslands has caused largely irreversible changes in ecosystem function (e.g. alterations in landscape net primary production pattern and reduction plant biodiversity) accompanied by increased water erosion, runoff, and leaching. This has also resulted in decreased forage availability for domestic livestock and wildlife [8, 12–18].

services by increasing perennial grasses. Increase in the density of perennial grasses improve soil quality, increase plant richness, and provides forage for livestock and wildlife [13, 14, 17, 18, 38]. Range managers have employed a variety of management practices to remove existing shrubs such as fire [39], herbicide [40], and physical removal [41] (**Figure 1**). However, these practices have common limitations: logistical difficulties and side effects potentially harmful to habitat restoration [42]. These control efforts often target only one part of the life cycle of the invasive species [42]. Moreover, attempts at control have been largely decreasing due to increasing costs [43]. An effective control strategy for invasive shrubs should therefore address these challenges posed by high cost, logistical difficulties, high risk impacts on non-targeted species, and both invasion and vegetation dynamics related to climate change. Also, a successful control strategy should be designed to control the targeted invasive species and to predict their effectiveness under specific environmental conditions. Process-based models can be used to assist range managers in identifying best management strategies through providing various outcomes of short- and long-term western rangeland conditions responding to different land management strategies and rapid changes in climate and other physical processes [44, 45]. To develop processbased model systems for assessing the impacts of creosotebush and mesquite in rangelands, it is important to understand factors that determine their distribution and abundance and how these relate to environmental factors. It is crucial to optimize their plant parameters describing growth

Simulating the Productivity of Desert Woody Shrubs in Southwestern Texas

http://dx.doi.org/10.5772/intechopen.73703

25

Productivity of creosotebush clones is highly dependent on water availability [35, 47–50]. If there is sufficient water, creosotebush increases growth rate as new tillers initiate within a clone [35, 51, 52]. Mesquite productivity is also affected by water availability. According to Easter and Sosebee [52] and Ansley et al. [35], when irrigated, mesquite shrubs produce more foliage, have higher canopy cover, have higher transpirational water loss, and have lower rootto-shoot mass ratio than non-irrigated mesquites in western Texas. Soil type is also an important factor for creosotebush and mesquite establishment as determined by the soil nutrient availability as well as the soil physical characteristics. Soil physical characteristics are important because they influence surface infiltration and surface percolation [53]. Deeper horizons enriched by clay or calcium carbonate have deeper percolation depth and water availability, whereas fine-textured vesicular subsurface and surficial soil horizon development can limit infiltration. These soil characteristics differentially change availability of water for desert plants [53–57]. Landscape position also affects vegetative growth because it determines the

**Figure 1.** Photographs of rangeland management practices: (a) burning, (b) aerial herbicide spraying, and (c) excavator

in models.

grubbing. Source: Adapted from PSSAT [46].

In the southwestern U.S., at lower and more level surfaces, many grasslands have been encroached on by two invasive woody shrubs, creosotebush (*Larrea tridentate*) and honey mesquite (*Prosopis glandulosa*) [7, 16, 19]. Densities of creosotebush and mesquite have increased in desert and arid rangelands in the southwestern U.S. since late in the nineteenth century [20, 21]. The dramatic increases in the density and cover of creosotebush and honey mesquite have greatly affected extensive areas of former desert grassland that were originally dominated by perennial C4 grasses including black grama (*Bouteloua eriopoda*) and blue grama (*Bouteloua gracilis*) [20, 22, 23]. Creosotebush is a xerophytic, evergreen, perennial shrub that has a welldeveloped lateral root system extending far beyond the area under the leaf canopy. This root system allows it to outcompete neighboring plants [12]. Due to a deep, non-overlapping root system and high water use efficiency, creosotebush can maintain lower levels of productivity during dry and hot periods, with growth only stopping during extreme drought [24–26]. Like creosotebush, honey mesquite is highly tolerant to drought because it can draw water from the water table through its long taproot (up to 58 m in depth) [27–29]. Also, mesquite can persist on sites where little or no ground water is available by growing lengthy shallow lateral roots [30]. Fisher et al. [31] reported that mesquite can survive under water limited condition with reduced leaf area, increased thickness of the leaf cuticle and almost complete cessation of growth. Creosotebush and mesquite have different invasive strategies in desert and arid rangelands. Mesquite produces seeds between June and September, which are dispersed by the animals [32]. Mesquite seeds germinate quickly; sprouting in less than 5 days [33]. After germination, it usually takes 10 days until the first true leaf, or cotyledon, is completely developed [34]. In early seedling development, mesquite quickly grows its deep taproot under limited water conditions. Its taproot grows shorter with sufficient water than in dry soil conditions [33, 35]. Based on these results, mesquite invasive strategies are related to quick germination and fast growth of deep roots under limited water conditions. While mesquite has high germination rate, creosotebush has low germinability and requires more water to sprout seeds [36]. Once creosotebush seeds successfully establish in the soil, however, creosotebush can live over a 1000 years by reproducing clones [37].

As creosotebush and mesquite have expanded over large areas of former desert grasslands, control of these invasive shrubs is playing an increasingly important role for restoring lost ecosystem services by increasing perennial grasses. Increase in the density of perennial grasses improve soil quality, increase plant richness, and provides forage for livestock and wildlife [13, 14, 17, 18, 38]. Range managers have employed a variety of management practices to remove existing shrubs such as fire [39], herbicide [40], and physical removal [41] (**Figure 1**). However, these practices have common limitations: logistical difficulties and side effects potentially harmful to habitat restoration [42]. These control efforts often target only one part of the life cycle of the invasive species [42]. Moreover, attempts at control have been largely decreasing due to increasing costs [43]. An effective control strategy for invasive shrubs should therefore address these challenges posed by high cost, logistical difficulties, high risk impacts on non-targeted species, and both invasion and vegetation dynamics related to climate change. Also, a successful control strategy should be designed to control the targeted invasive species and to predict their effectiveness under specific environmental conditions. Process-based models can be used to assist range managers in identifying best management strategies through providing various outcomes of short- and long-term western rangeland conditions responding to different land management strategies and rapid changes in climate and other physical processes [44, 45]. To develop processbased model systems for assessing the impacts of creosotebush and mesquite in rangelands, it is important to understand factors that determine their distribution and abundance and how these relate to environmental factors. It is crucial to optimize their plant parameters describing growth in models.

are susceptible to desertification as the result of cumulative threats such as extreme weather events (e.g. drought), land use change (e.g. suburbanization), inappropriate land management (e.g. livestock overgrazing), and invasion by shrubs and other woody plants [3, 4]. Among these threats, plant invasions are considered as one of the most serious problems in much of the southwestern U.S. [5]. Encroachment of woody shrubs into grasslands has been commonly observed in the arid and semi-arid regions and often reported [6–9]. Encroachment can be defined as increasing density, cover and biomass of shrub and/or woody species in open canopy systems [8]. These woody shrubs are indigenous species that have increased in density or cover because of changes in climate variables (i.e. warmer and more humid conditions), land use modifications, or decreased frequency of disturbance regimes [8, 10, 11]. Extensive expansion of shrubs and woody plant into grasslands has caused largely irreversible changes in ecosystem function (e.g. alterations in landscape net primary production pattern and reduction plant biodiversity) accompanied by increased water erosion, runoff, and leaching. This has also resulted in

In the southwestern U.S., at lower and more level surfaces, many grasslands have been encroached on by two invasive woody shrubs, creosotebush (*Larrea tridentate*) and honey mesquite (*Prosopis glandulosa*) [7, 16, 19]. Densities of creosotebush and mesquite have increased in desert and arid rangelands in the southwestern U.S. since late in the nineteenth century [20, 21]. The dramatic increases in the density and cover of creosotebush and honey mesquite have greatly affected extensive areas of former desert grassland that were originally dominated

*gracilis*) [20, 22, 23]. Creosotebush is a xerophytic, evergreen, perennial shrub that has a welldeveloped lateral root system extending far beyond the area under the leaf canopy. This root system allows it to outcompete neighboring plants [12]. Due to a deep, non-overlapping root system and high water use efficiency, creosotebush can maintain lower levels of productivity during dry and hot periods, with growth only stopping during extreme drought [24–26]. Like creosotebush, honey mesquite is highly tolerant to drought because it can draw water from the water table through its long taproot (up to 58 m in depth) [27–29]. Also, mesquite can persist on sites where little or no ground water is available by growing lengthy shallow lateral roots [30]. Fisher et al. [31] reported that mesquite can survive under water limited condition with reduced leaf area, increased thickness of the leaf cuticle and almost complete cessation of growth. Creosotebush and mesquite have different invasive strategies in desert and arid rangelands. Mesquite produces seeds between June and September, which are dispersed by the animals [32]. Mesquite seeds germinate quickly; sprouting in less than 5 days [33]. After germination, it usually takes 10 days until the first true leaf, or cotyledon, is completely developed [34]. In early seedling development, mesquite quickly grows its deep taproot under limited water conditions. Its taproot grows shorter with sufficient water than in dry soil conditions [33, 35]. Based on these results, mesquite invasive strategies are related to quick germination and fast growth of deep roots under limited water conditions. While mesquite has high germination rate, creosotebush has low germinability and requires more water to sprout seeds [36]. Once creosotebush seeds successfully establish in the soil, however, creosotebush

As creosotebush and mesquite have expanded over large areas of former desert grasslands, control of these invasive shrubs is playing an increasingly important role for restoring lost ecosystem

grasses including black grama (*Bouteloua eriopoda*) and blue grama (*Bouteloua* 

decreased forage availability for domestic livestock and wildlife [8, 12–18].

can live over a 1000 years by reproducing clones [37].

by perennial C4

24 Arid Environments and Sustainability

Productivity of creosotebush clones is highly dependent on water availability [35, 47–50]. If there is sufficient water, creosotebush increases growth rate as new tillers initiate within a clone [35, 51, 52]. Mesquite productivity is also affected by water availability. According to Easter and Sosebee [52] and Ansley et al. [35], when irrigated, mesquite shrubs produce more foliage, have higher canopy cover, have higher transpirational water loss, and have lower rootto-shoot mass ratio than non-irrigated mesquites in western Texas. Soil type is also an important factor for creosotebush and mesquite establishment as determined by the soil nutrient availability as well as the soil physical characteristics. Soil physical characteristics are important because they influence surface infiltration and surface percolation [53]. Deeper horizons enriched by clay or calcium carbonate have deeper percolation depth and water availability, whereas fine-textured vesicular subsurface and surficial soil horizon development can limit infiltration. These soil characteristics differentially change availability of water for desert plants [53–57]. Landscape position also affects vegetative growth because it determines the

**Figure 1.** Photographs of rangeland management practices: (a) burning, (b) aerial herbicide spraying, and (c) excavator grubbing. Source: Adapted from PSSAT [46].

time interval between receipt of rain and its infiltration into the soil [58]. For example, creosotebush and mesquite do poorer on steep slopes with coarse, shallow soil [59–61] which have more runoff and less water available to plants [62]. Hamerlynck and McAuliffe [26] reported that branch mortality of creosotebush tended to increase on hillslopes, while no dead plants were found in alluvial sites.

over several years [72, 74]. In those studies, the annual value for maximum leaf area index for the growing season increased each year to simulate how trees grow. The difficulties when attempting to transfer these approaches to desert evergreen shrubs are: (1) these shrubs do not lose their leaves during the winter of each season, (2) their phenological development is strongly tied to rainfall amount and patterns, and not just degree day accumulation, and (3) these shrubs can lose

Simulating the Productivity of Desert Woody Shrubs in Southwestern Texas

http://dx.doi.org/10.5772/intechopen.73703

27

For this chapter, we used a multi-model combination approach, combining the strengths of two different models. A range of morphological characteristics of creosote and mesquite has been investigated from multiple locations. Based on field data, the ALMANAC model was used to create and optimize both the plant parameters and the growth curve. The resulting simulated biomass yields of creosotebush and mesquite were compared with the measured yields at the sampling locations. The resulting plant parameters and growth curve were subsequently incorporated into APEX to evaluate the effects of rainfall patterns and local soil and topological properties on the growth and productivity of the creosotebush within the sub-watershed scale in multiple regions of western Texas. The multi-model system can describe invasive plant growth and development interaction with environmental factors including light, temperature, soil characteristics and water availability. This is important to help understand why mesquite and creosotebush expand in rangelands. In addition, the multi-model system can quantitatively evaluate the invasive shrubs-perennial grasses competitive interactions in different environments and study the effects of control of invasive plants on soil organic matter and soil water content. This study will provide the desired outcomes in invasive plant management programs on rangelands.

As described by Kim et al. [75], creosotebush morphological measurements were conducted at two sites in Pecos County (Fort Stockton 1 and 3), one site in Reeves County (Fort Stockton 2), and 10 sites in Brewster County (Alpine A, 1–9), all in Texas. Fort Stockton 1 was located in the right-of-way of Highway I-10, 91 km west of Fort Stockton. Fort Stockton 2 was also located in the right-of-way of Highway I-10, 61 km west of Fort Stockton. Fort Stockton 3 was inside Fort Stockton. Ten study sites (Alpine A, 1–9) were randomly selected within a 15 km wide distance on a large ranch 57 km south of Alpine. Alpine A was an airplane landing strip until 2005, so

As described by Kiniry [76], mesquite morphological measurement was conducted in the field located at the Grassland, Soil and Water Research Center near Temple in Bell County, Texas, U.S.

the creosote bushes there have been established for only 11 years.

noticeable amounts of biomass due to tiller death during severe drought periods.

**2. Materials and methods**

*2.1.1. Study sites*

*2.1.1.1. Creosotebush*

*2.1.1.2. Honey mesquite*

**2.1. Morphological data collection**

Based on these results, creosotebush and mesquite growth varies with different rainfall, different soil, and different landscape position. Simulating creosotebush and mesquite growth chronological patterns in different desert rangelands and simulating the effects of control of these two invasive shrubs on vegetation and soil and water qualities are important when trying to control shrub productivity under various climate and soil conditions in the long term. Scaling up from small-scale experiments to large scale field-based monitoring is an important step for reducing the long-term productivity of creosotebush and mesquite under various climate and soil conditions in future. Process-based models can simulate the effects of precipitation and geomorphic patterns in detail, estimating apparent contradictory effects. They can project variation in creosotebush and mesquite production across several different landscapes and climatic conditions. Such models can be used systemically and in combination of characteristics of hydrology, soil erosion, land slope, and nutrient balance, which are hard to approach theoretically or technically in field and plot experiments. Two field-based processlevel models, Agricultural Land Management Alternatives with Numerical Assessment Criteria (ALMANAC) and Agricultural Policy & Environmental eXtender (APEX), have potential to satisfy the needed characteristics in simulating creosotebush growth in desert rangelands.

The ALMANAC model is a process-oriented plant model that effectively simulates growth of a wide range of plant species [63, 64]. Strength of ALMANAC is its capability to accurately simulate competition for light, nutrients, and water for several plant species [65]. APEX can be applied for whole-farm or small watershed (up to 2500 km2 ) analyses and can evaluate plant growth and yield of plant species, with focus on soil and water quality in small-scale watersheds [66]. Both models operate on a daily time step. APEX's major components are climate, hydrology, plant growth, nutrient cycling, soil erosion, carbon cycling, and agricultural management practices [67]. This model uses the ALMANAC plant growth algorithms to predict productivity for over 100 plant species [67]. APEX calculates several surface hydrological parameters (daily runoff, plant transpiration, soil evaporation, water stress for plant growth, and lateral subsurface flow) in different climates having variable land topological characteristics [67, 68]. Through APEX, the effects of control of invasive shrubs on soil quality can be calculated by the net differences in soil organic carbon (SOC) that occur with both invasive shrub control and no control sites.

Simulating plant development of evergreen desert shrubs like creosotebush requires some restructuring of the basic approach of degree days. Typically annual crops are simulated with a degree day sum from planting to physiological maturity for an annual growing season with crop specific values for the base temperature and optimum temperature [63–65, 69]. This approach has also been applied to warm season perennial grasses with annual growing cycles for the leaf area and biomass [70–73]. Unlike creosotebush, mesquite is a perennial deciduous tree that drops its leaves each year and then resumes growth the following spring, each year possibly attaining (in the absence of environmental stress) its potential leaf area index value for that year. When applied to trees in Canada, the degree day sum is for a series of years so that the trees can develop over several years [72, 74]. In those studies, the annual value for maximum leaf area index for the growing season increased each year to simulate how trees grow. The difficulties when attempting to transfer these approaches to desert evergreen shrubs are: (1) these shrubs do not lose their leaves during the winter of each season, (2) their phenological development is strongly tied to rainfall amount and patterns, and not just degree day accumulation, and (3) these shrubs can lose noticeable amounts of biomass due to tiller death during severe drought periods.

For this chapter, we used a multi-model combination approach, combining the strengths of two different models. A range of morphological characteristics of creosote and mesquite has been investigated from multiple locations. Based on field data, the ALMANAC model was used to create and optimize both the plant parameters and the growth curve. The resulting simulated biomass yields of creosotebush and mesquite were compared with the measured yields at the sampling locations. The resulting plant parameters and growth curve were subsequently incorporated into APEX to evaluate the effects of rainfall patterns and local soil and topological properties on the growth and productivity of the creosotebush within the sub-watershed scale in multiple regions of western Texas. The multi-model system can describe invasive plant growth and development interaction with environmental factors including light, temperature, soil characteristics and water availability. This is important to help understand why mesquite and creosotebush expand in rangelands. In addition, the multi-model system can quantitatively evaluate the invasive shrubs-perennial grasses competitive interactions in different environments and study the effects of control of invasive plants on soil organic matter and soil water content. This study will provide the desired outcomes in invasive plant management programs on rangelands.
