Xuejun Dong

Texas A&M University | TAMU · Department of Soil and Crop Sciences

High air temperatures during the crop growing season can reduce harvestable yields in major agronomic crops worldwide. Repeated and prolonged high night air temperature stress may compromise plant growth and yield. Crop varieties with improved heat tolerance traits as well as crop management strategies at the farm scale are thus needed for climate...

We used soil water modeling as a tool to quantify water use of non-cultivated plant communities based on easily measured field data of soil water contents, soil hydraulic properties, and leaf area index. The model was applied in the mixed-grass prairie, considering a dynamic and non-uniform root distribution, the effect of soil water stress on plan...

Belowground properties strongly affect agri- cultural productivity. Traditional methods for quantifying below- ground properties are destructive, labor-intensive and point-based. Ground penetrating radar can provide non-invasive, areal, and repeatable underground measurements. This article reviews the application of ground penetrating radar for soi...

Recent progress in ecological remote sensing calls for a more rapid measurement and a closer assessment of crop drought tolerance traits under field conditions. This study addresses three main questions: (1) If leaf dry matter content (LDMC) is equally effective in indicating cotton drought tolerance as leaf osmotic potential at full turgor (πo); (...

Hemp (Cannabis sativa L. ssp. sativa) has a long history of domestication due to its versatile uses. Recently, different sectors in the economy are investigating hemp cultivation to increase agro-nomic production and to limit delta-9-tetrahydrocannabinol (THC). Despite the rapid growth of hemp literature in recent years, it is still uncertain wheth...

Mustard cover crops can provide multiple soil health benefits but may adversely affect cash crops by depleting soil water. This was tested in a center-pivot irrigated corn cropping system in southwest Texas from 2018 to 2020. Changes in biomass growth of both the cover crops and corn, and soil water content in the root zone were monitored multiple...

The need for improved crop water use efficiency calls for flexible modeling platforms to implement new ideas in plant root uptake and its regulation mechanisms. This paper documents the details of modifying a soil infiltration and redistribution model to include (a) dynamic root growth, (b) non-uniform root distribution and water uptake, (c) the ef...

In hard red winter wheat (Triticum aestivum L.), increased understanding of relationships between grain protein concentration (GPC) and other phenotypic traits is needed for simultaneously achieving high yield and GPC through genetic improvement and management. Two field experiments with 20 genotypes each were conducted in 2018/2019 in Uvalde and C...

Remote-sensing using normalized difference vegetation index (NDVI) has the potential of rapidly detecting the effect of water stress on field crops. However, this detection has typically been accomplished only after the stress effect led to significant changes in crop green biomass, leaf area index, angle and position, and few studies have attempte...

Sesame (Sesamum indicum L.) as an ancient crop has received wide attention in subtropical and temperate regions of the world. Yet there is limited data linking maturity with seed yield, which hampers sesame improvement. We used a multi-channel spectral sensor to measure canopy vegetation indices during the period of drydown to facilitate a rapid yi...

Roots strongly influence the growth and yield of field crops. We characterized root morphological traits of 10 winter wheat varieties in order to determine the extent they were influenced by the environments and impacted grain yield under two irrigation regimes at Bushland (a cooler, drier site with clay loam soil) and Uvalde (a warmer, wetter site...

Bulk leaf carbon isotopic composition (δ ¹³ C bulk ) has been widely used to investigate leaf level water use efficiency (WUE l ) in efforts to boost grain yield relative to crop water use. Although widely used for isotopic analyses, the bulk leaf represents a complex mixture of compounds. Single-compound isotopic analyses carry diagnostic advantag...

Effects of environmental and management factors on the diversity and abundance of rhizosphere microbes in unmanaged ecosystems are well established. However, there is limited information about these interactions in vegetable cropping systems. In this two-year field study, we used organic amendments (humic substances, HS) and water supply (deficit i...

Pattern of vertical distribution of plant roots determines plant water and nutrient uptake and influences various soil processes under field conditions. However, information of root distribution in the whole rooting profile is rarely available in practice. This paper documents a method to quickly quantify root vertical distribution pattern using li...

Rapid and non-destructive assessment of water status is essential to enhance crop performance. This study aimed to evaluate photosynthetic performance and to monitor water status in cotton under field conditions. A two-year experiment was conducted with three irrigation regimes to measure the following parameters: photochemical reflectance index (P...

Aim Ground penetrating radar (GPR) as a non-invasive technique is widely used in coarse root detection. However, the applicability of the technique to detect fine roots of agricultural crops is unknown. The objective of this study was to assess the feasibility of utilizing GPR to detect fine roots in the field. Methods This study was conducted in...

Leaf wax forms the boundary between plant leaf and atmosphere. The properties of the wax layer reflect physiological and biochemical adaptation and response to environmental stress, including drought. Agricultural field cropping experiments provide an intermediary between complex natural ecosystems and controlled laboratory growth experiments, rout...

Tillage practices are critical for sustaining soil quality necessary for successful crop growth and productivity. A three-year study (2012–2014) was carried out to evaluate the influence of strip and conventional tillage practices and three water status levels [T1 = 100% of evapotranspiration (ET) demands, T2 = 0.75T1and T3 = 0.5T1] on plant morpho...

The next generation of plant breeding progress requires accurately estimating plant growth and development parameters to be made over routine intervals within large field experiments. Hand measurements are laborious and time consuming and the most promising tools under development are sensors carried by ground vehicles or unmanned aerial vehicles,...

Despite intensive study in recent decades, soil respiration rate (Rs) and its evolution accompanying vegetation succession remain perplexing. Using a 50-year chronosequence of sand-fixing revegetation in the Tengger Desert of China, we took intact soil columns of 20 cm in depth, incubated them at 12 levels of soil water content (0–0.4 m3 m−3) and a...

The need for improved crop water use efficiency calls for flexible modeling platforms to implement new ideas in plant root uptake and its regulation mechanisms. This paper documents the details of modifying a soil infiltration and redistribution model to include (a) dynamic root growth, (b) non-uniform root distribution and water uptake, (c) the ef...

Deficit irrigation has been used as an agricultural water management strategy to maximize water productivity in vegetable crops worldwide. Eight pepper (Capsicum spp.) cultivars in four distinctive groups differing in pungency levels (Serrano: Diablo and Alcon; Jalapeno: TAMU-JAL and TAMU-J222; Bell: 81447 and S1122; and Habanero: TMH and TAM-Orang...

Soil respiration in water-limited ecosystems is affected intricately by soil water content (SWC), temperature, and soil properties. Eight sites on sand-fixed dunes revegetated in different years since1950s, with several topographical positions and various biological soil crusts (BSCs) and soil properties, were selected, as well as a moving sand dun...

Soil water retention curves are essential for solving water flow problems, but direct measurement usually is laborious, time-consuming and expensive. Thus indirect methods using more easily measured soil properties are frequently used. The model of Arya and Paris (1981) [Soil Sci. Soc. Am. J., 45: 1023-1030] has been used widely to predict water re...

A plant root water uptake model written in Fortran 77. The program was based on A.W. Warrick's soil water infiltration and redistribution model (2003, Soil Water Dynamics, Oxford University Press), with additions in (a) dynamic root growth, (b) non-uniform root distribution and water uptake, (c) effect of water stress on plant uptake, (d) root upta...

This is a Fortran 77 program designed to search for optimal root distribution and rooting depth parameters useful for modeling plant root uptake and soil water dynamics.

Biological soil crusts (BSCs) play an important role in surface soil hydrology. Soils dominated with moss BSCs may have higher infiltration rates than those dominated with cyanobacteria or algal BSCs. However, it is unnown whether improved infiltration in moss BSCs is accompanied by an increase in soil hydraulic conductivity or water retention capa...

The widespread invasion of exotic cool-season grasses, such as Kentucky bluegrass and smooth brome, in the mixed-grass rangelands is diminishing the hope of bringing back the natural native plant-dominated communities. A best management strategy for these rangelands, according to several plant community studies, is perhaps to live with these cool-s...

Control of exotic plant species invading the native prairie relies on our understanding of the eco-physiological mechanisms responsible for the spread of these species as they compete with native plants for soil resources. We used a greenhouse pot experiment to study vegetative biomass allocation in response to drought stress in two exotic grass sp...

Proper management of water is vitally important to maintain and sustain crop production in arid and semi-arid regions, where water is often a limiting factor of crop growth. Despite progress made in the past decade, accurate prediction of water flow in the soil-plant system remains challenging. This paper briefly reviews opportunities for improving...

Proper management of water is vitally important to maintain and sustain crop production in arid and semi-arid regions, where water is often a limiting factor of crop growth. Despite progress made in the past decade, accurate prediction of water flow in the soil-plant system remains challenging. This paper briefly reviews opportunities for improving...

The widespread invasion of exotic cool-season grasses in mixed-grass rangeland is diminishing the hope of bringing back the natural native plant communities. However, ecophysiological mechanisms explaining the relative competitiveness of these invasive grasses over the native species generally are lacking. We used experimental data collected in sou...

Litter decomposition is a complex process involving a diverse group of biological taxa. Nitrogen limitation of fine-root decomposition occurred under moderate grazing but not under heavy grazing. This has implications on nutrient release and cycling in the mixed-grass prairie ecosystem. Summary A modified litter-bag method was used to measure plant...

Production per amount of water used (water use efficiency, WUE) is closely correlated with drought tolerance. Although stomatal aperture can regulate WUE, the underlying molecular mechanisms are still unclear. Previous reports revealed that stomatal closure was inhibited in the calcium-sensing receptor (CAS) antisense line of Arabidopsis (CASas). H...

Worldwide measurements of nearly 130 C3 species covering all major plant functional types are analyzed in conjunction with model simulations to determine the effects of mesophyll conductance (gm ) on photosynthetic parameters and their relationships estimated from A/Ci curves. We find that an assumption of infinite gm results in up to 75% underesti...

Despite heavy study in past decades, responses of the major components of soil respiration (root-derived vs. soil microbe derived) to environmental factors is still not well-understood. This is mainly due to the inaccessibility of major soil organisms for experimental manipulation. Based on data collected in the 2009 growing season, we used a field...

The correlation between forest decline and calcium (Ca) depletion under long-term acid deposition remains elusive in China due to the high level of Ca deposition. We compared two species (Abies fabri and Rhododendron calophytum) for their growth pattern and base elements concentration in both polluted (Mt. Emei) and unpolluted (Mt. Gongga) sites in...

The appearance characteristics of A. fabri forest in Mt. Emei (a) and Mt. Gongga (b) in April 2007. Distinct defoliation was observed in Mt. Emei

This study was conducted on a mixed-grass prairie in south-central North Dakota, USA, to test the effect of animal grazing on rhizome biomass. Below-ground plant biomass samples were collected from pastures with moderate and heavy grazing by beef cattle. Because the biomass data did not meet the normality assumptions, the computer resampling method...

Grazing management can affect grassland carbon (C) dynamics, yet limited information is available documenting management effects on carbon dioxide (CO2) efflux. A study was conducted to quantify the role of long-term grazing management to affect CO2 efflux within the semiarid northern Great Plains of North America. Grazing management systems evalua...

Aims Desert characterized by alkaline soil with low organic matter and nutrients has a high soil oxidative potential. We hypothesized that oxidase activities would recover faster than hydrolases during the succession of sand-fixing community. Methods Sand dunes stabilized in different years, including a moving sand dune and a steppe at the southea...

To assess the potential contribution of nitric oxide (NO) emission from the plants grown under the increasing nitrogen (N) deposition to atmospheric NO budget, the effects of simulated N deposition on NO emission and various leaf traits (e.g., specific leaf area, leaf N concentration, net photosynthetic rate, etc.) were investigated in 79 plant spe...

Aims Aluminum (Al) toxicity is one of the major factors that limit plant growth. Low concentration of hydrogen sulfide (H2S) has been proven to function in physiological responses to various stresses. The objective of this study is to investigate the possible role of H2S in Al toxicity in barley (Hordeum vulgare L) seedlings. Methods Barley seedli...

Both the native Pascopyrum smithii and introduced Poa pratensis are dominant plants in the mixed-grass prairie. Knowledge of leaf-water relations and water use strategies in these two grasses under animal grazing and drought is needed for understanding responses of the prairie to future climate change. We studied leaf-water relations traits of Pasc...

In the context of climate change, there is potential for a higher frequency of natural disasters. Here a linear regression analysis is employed to link the relationship between the natural disaster occurrence and average global temperature from 1980 to 2010. The results indicate that epidemic, extreme temperature, flood and storm events are strongl...

The Arabidopsis calcium-sensing receptor CAS is a crucial regulator of extracellular calcium-induced stomatal closure. Free cytosolic Ca2+ (Ca2+i) increases in response to a high extracellular calcium (Ca2+o) level through a CAS signalling pathway and finally leads to stomatal closure. Multidisciplinary approaches including histochemical, pharmacol...

As a second messenger, the free cytosolic calcium ion (Ca(2+)) plays important roles in many biochemical and physiological processes including photosynthesis in plants. In this study, we investigated morphological changes, chlorophyll accumulation and chloroplast development during early photomorphogenesis in etiolated seedlings of both Arabidopsis...

Hydrogen sulphide (H(2)S) is emerging as a potential messenger molecule involved in modulation of physiological processes in animals and plants. In this report, the role of H(2)S in modulating photosynthesis of Spinacia oleracea seedlings was investigated. The main results are as follows. (i) NaHS, a donor of H(2)S, was found to increase the chloro...

We selected six tree species, Pinus massoniana Lamb., Cryptomeria fortunei Hooibr. ex Otto et Dietr., Cunninghamia lanceolata (Lamb.) Hook., Liquidambar formosana Hance, Pinus armandii Franch. and Castanopsis chinensis Hance, which are widely distributed as dominant species in the forest of southern China where acid deposition is becoming more and...

a b s t r a c t The diurnal variation of nitric oxide (NO) emission fluxes from a Kandelia obovata and Avicennia marina mangrove wetland were studied in the Zhangjiang River Estuary Mangrove National Nature Reserve using a dynamic chamber-based technique and a chemiluminescent analyzer. Results from field exper-iments show that NO emission from K....

Modulation of nitric oxide (NO) on ion homeostasis, by enhancing salt secretion in the salt glands and Na+ sequestration into the vacuoles, was investigated in a salt-secreting mangrove tree, Avicennia marina (Forsk.) Vierh. The major results are as follows: (i) under 400 mM NaCl treatment, the application of 100 µM sodium nitroprusside (SNP), an N...

We applied a method to automate bibliographic management for biomedical and environmental scientists/professionals using a BIBTeX database of the titles and abbreviations of :387 mostly biological journals. This database is readily usable to meet the requirements for journal title format by many of today's leading scientific publishers. This articl...

We applied a method to automate bibliographic management for biomedical and environmental scientists/professionals using a BIBTeX database of the titles and abbreviations of 4,387 mostly biological journals. This database is readily usable to meet the requirements for journal title format by many of today's leading scientific publishers. This artic...

On the edge of the Tengger Desert in northern China, revegetation has changed the landscape from moving dunes to sta-bilized dunes covered by shrubs, which further modifies the pattern of rainfall redistribution. To study rainfall interception loss by shrubs and its relationship to rainfall properties and crown structure, throughfalls passing throu...

http://www.rangelandcongress.org/VIII%20Proceedings/Multifunctional%20Grasslands%20in%20a%20Changing%20World%20Volume%28I%29.pdf Page 178.

Wavelet transforms (WTs) are finding increasing use in the discovery of the scale-specific properties of complex biological data. Although many efforts have been made to explain the main concepts of WT without advanced mathematics, the implicit reliance on digital signal processing terminology is widespread in many popular articles. This may cause...

http://www.rangelandcongress.org/VIII%20Proceedings/Multifunctional%20Grasslands%20in%20a%20Changing%20World%20Volume%28I%29.pdf Page 177

Questions have been raised about whether herbaceous productivity declines linearly with grazing or whether low levels of grazing can increase productivity. This paper reports the response of forage production to cattle grazing on prairie dominated by Kentucky bluegrass (Poa pratensis L.) in south-central North Dakota through the growing season at 5...

In the Mu Us Sandland of China, a diversity of native shrubs make-up an important part of the local vegetation. Based on leaf water relations and anatomy, we show that the water-spending/water-saving paradigm is applicable to assess the drought adaptations of the shrubs. The water spenders showed a more mesic leaf anatomy, higher osmotic potential,...

In the semi-desert environment of the Mu Us Sandland, the vegetation is composed chiefly of shrubs and semi-shrubs, coverage normally amounting to 30-40%. However, an exception can be found in the community of Sabina vulgaris Antoine, an evergreen shrub, which tends to grow so densely that it covers the sand dunes completely. Previous research has...

A one-dimensional spatial simulation model, SLOPE, was developed to simulate the dynamics of soil water and vegetation biomass of semi-arid hilly sandy grasslands. The model stressed interactions between soil water and plant growth for variable geographical locations, slope angle, aspect angle, soil hydraulic properties as well as plant assimilatio...

Porometric analysis of transpiration variance of plant cuttings of 8 species in Maowusu Sandland, Inner Mongolia was carried out. Transpiration rate of a plant part changed immediately after cutting. Quantitation and prediction of such a change were different as the nature of the change was relevant to the leaf-water status of the plant which, in t...