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Wojcikiewicz R, Ji W, Hanan NP. Quantifying shrub-shrub competition in drylands using aerial imagery and a novel landscape competition index. New Phytol 2024; 241:1973-1984. [PMID: 38273449 DOI: 10.1111/nph.19505] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Accepted: 12/03/2023] [Indexed: 01/27/2024]
Abstract
The Jornada Basin Long-Term Ecological Research Site (JRN-LTER, or JRN) is a semiarid grassland-shrubland in southern New Mexico, USA. The role of intraspecific competition in constraining shrub growth and establishment at the JRN and in arid systems, in general, is an important question in dryland studies. Using information on shrub distributions and growth habits at the JRN, we present a novel landscape-scale (c. 1 ha) metric (the 'competition index', CI), which quantifies the potential intensity of competitive interactions. We map and compare the intensity of honey mesquite (Prosopis glandulosa, Torr.) competition spatially and temporally across the JRN-LTER, investigating associations of CI with shrub distribution, density, and soil types. The CI metric shows strong correlation with values of percent cover. Mapping CI across the Jornada Basin shows that high-intensity intraspecific competition is not prevalent, with few locations where intense competition is likely to be limiting further honey mesquite expansion. Comparison of CI among physiographic provinces shows differences in average CI values associated with geomorphology, topography, and soil type, suggesting that edaphic conditions may impose important constraints on honey mesquite and growth. However, declining and negative growth rates with increasing CI suggest that intraspecific competition constrains growth rates when CI increases above c. 0.5.
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Affiliation(s)
- Robert Wojcikiewicz
- Plant and Environmental Sciences Department, New Mexico State University, Las Cruces, NM, 88003, USA
| | | | - Niall P Hanan
- Plant and Environmental Sciences Department, New Mexico State University, Las Cruces, NM, 88003, USA
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Fernández PD, Gasparri NI, Rojas TN, Banegas NR, Nasca JA, Jobbágy EG, Kuemmerle T. Silvopastoral management for lowering trade-offs between beef production and carbon storage in tropical dry woodlands. Sci Total Environ 2024; 912:168973. [PMID: 38072278 DOI: 10.1016/j.scitotenv.2023.168973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2023] [Revised: 11/27/2023] [Accepted: 11/27/2023] [Indexed: 12/22/2023]
Abstract
Tropical dry woodlands and savannas harbour high levels of biodiversity and carbon, but are also important regions for agricultural production. This generates trade-offs between agriculture and the environment, as agricultural expansion and intensification typically involve the removal of natural woody vegetation. Cattle ranching is an expanding land use in many of these regions, but how different forms of ranching mediate the production/environment trade-off remains weakly understood. Here, we focus on the Argentine Chaco, to evaluate trade-offs between beef production and carbon storage in grazing systems with different levels of woody cover (n = 27). We measured beef productivity and carbon storage during 2018/19 and used a regression framework to quantify the trade-off between both, and to analyze which agroclimatic and management variables explain the observed trade-off. Our main finding was that silvopastures had the lowest trade-off between beef production and carbon storage, as management in these systems seeks to increase herbaceous forage by removing shrubs, while maintaining most of the bigger trees that contain most above-ground carbon. The most important variable explaining the beef production/carbon storage trade-off was pasture management, specifically the number of shrub encroachment control interventions, with a lower trade-off for higher numbers of interventions. Unfortunately, more interventions can also result in woody cover degradation over time, and shrub encroachment management must therefore be improved to become sustainable. Overall, our study highlights the strong environmental trade-offs associated with beef production in dry woodlands and savanna, but also the key role of good management practices in lowering this trade-off. Specifically, silvopastoral systems can increase beef production as much as converting woodlands to tree-less pastures, but silvopastures retain much more carbon in aboveground vegetation. Silvopastoral systems thus represent a promising land-use option to lower production/environment trade-offs in the Dry Chaco and likely many other tropical dry woodlands and savannas.
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Affiliation(s)
- Pedro David Fernández
- Instituto de Investigación Animal del Chaco Semiárido, Instituto Nacional de Tecnología Agropecuaria, Chañar Pozo S/N, Leales 4113, Tucumán, Argentina; Geography Department, Humboldt-University Berlin, Unter den Linden 6, 10099 Berlin, Germany; Instituto de Ecología Regional, CONICET, Universidad Nacional de Tucumán, Casilla de Correo 34, 4107 Yerba Buena, Tucumán, Argentina.
| | - Nestor Ignacio Gasparri
- Instituto de Ecología Regional, CONICET, Universidad Nacional de Tucumán, Casilla de Correo 34, 4107 Yerba Buena, Tucumán, Argentina
| | - Tobias Nicolás Rojas
- Instituto de Ecología Regional, CONICET, Universidad Nacional de Tucumán, Casilla de Correo 34, 4107 Yerba Buena, Tucumán, Argentina
| | - Natalia Romina Banegas
- Instituto de Investigación Animal del Chaco Semiárido, Instituto Nacional de Tecnología Agropecuaria, Chañar Pozo S/N, Leales 4113, Tucumán, Argentina
| | - José Andrés Nasca
- Instituto de Investigación Animal del Chaco Semiárido, Instituto Nacional de Tecnología Agropecuaria, Chañar Pozo S/N, Leales 4113, Tucumán, Argentina
| | - Esteban Gabriel Jobbágy
- Grupo de Estudios Ambientales e IMASL, Universidad Nacional de San Luis, CONICET, Ejercito de los Andes 950, D5700HHW San Luis, Argentina
| | - Tobias Kuemmerle
- Geography Department, Humboldt-University Berlin, Unter den Linden 6, 10099 Berlin, Germany; Integrative Research Institute on Transformations in Human-Environment Systems (IRI THESys), Unter den Linden 6, 10099 Berlin, Germany
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Niu F, Pierce NA, Okin GS, Archer SR, Fischella MR, Nadoum S. Sandblasting promotes shrub encroachment in arid grasslands. New Phytol 2023; 240:1817-1829. [PMID: 37658674 DOI: 10.1111/nph.19238] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/30/2022] [Accepted: 08/15/2023] [Indexed: 09/03/2023]
Abstract
Shrub encroachment is a common ecological state transition in global drylands and has myriad adverse effects on grasslands and the services they provide. This physiognomic shift is often ascribed to changes in climate (e.g. precipitation) and disturbance regimes (e.g. grazing and fire), but this remains debated. Aeolian processes are known to impact resource distribution in drylands, but their potential role in grassland-to-shrubland state changes has received little attention. We quantified the effects of 'sandblasting' (abrasive damage by wind-blown soil) on the ecophysiology of dryland grass vs shrub functional types using a portable wind tunnel to test the hypothesis that grasses would be more susceptible to sandblasting than shrubs and, thus, reinforce transitions to shrub dominance in wind-erodible grasslands when climate- or disturbance-induced reductions in ground cover occur. Grasses and shrubs responded differently to sandblasting, wherein water-use efficiency declined substantially in grasses, but only slightly in shrubs, owing to grasses having greater increases in day/nighttime leaf conductance and transpiration. The differential ecophysiological response to sandblasting exhibited by grass and shrub functional types could consequently alter the vegetation dynamics in dryland grasslands in favour of the xerophytic shrubs. Sandblasting could thus be an overlooked driver of shrub encroachment in wind-erodible grasslands.
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Affiliation(s)
- Furong Niu
- College of Forestry, Gansu Agricultural University, Lanzhou, Gansu, 730070, China
- School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, 85721, USA
| | - Nathan A Pierce
- USDA-Agricultural Research Service, Southwest Watershed Research Center, Tucson, AZ, 85719, USA
| | - Gregory S Okin
- Department of Geography, University of California, Los Angeles, CA, 90095, USA
| | - Steven R Archer
- School of Natural Resources and the Environment, University of Arizona, Tucson, AZ, 85721, USA
| | - Michael R Fischella
- Department of Geography, University of California, Los Angeles, CA, 90095, USA
| | - Shereen Nadoum
- Department of Geography, University of California, Los Angeles, CA, 90095, USA
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Zhao Y, Wang H, Guo T, Li Z, Mi W, Cao Z. Response of soil C-, N-, and P- acquisition enzymes to moisture pulses in desert grassland to shrubland state transition. Sci Total Environ 2023; 861:160569. [PMID: 36455741 DOI: 10.1016/j.scitotenv.2022.160569] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 11/24/2022] [Accepted: 11/25/2022] [Indexed: 06/17/2023]
Abstract
Grassland-shrubland state transition causes profound effects on soil nutrients and microorganisms, yet little is known about how these soil characteristics are influenced by rainfall and litter changes during transition. Here, we examined water (high or low moisture pulse) and litter (grass or shrub) effects on these soil characteristics in grassland-shrubland mosaics consisting of desert grassland (DG), grassland edge (GE), shrubland edge (SE), and shrubland (SL) sites. The results showed that the transition of DG-GE-SE-SL significantly reduced soil moisture, total carbon (C), total nitrogen (N), total phosphorus (P), microbial biomass carbon, and microbial biomass nitrogen, revealing evident soil degradation during this transition. After applying water and litter, soil microbial respiration (SMR) and the activities of all enzymes were promoted to varying degrees among the sites. Specifically, SMR was promoted under a low moisture pulse but suppressed under a high moisture pulse along the transition from DG to SL. Two C-acquisition enzymes, cellobiohydrolase and β-1,4-glucosidase, became increasingly active from DG to SL. Another C-acquisition enzyme of β-1,4-xylosidase and an N-acquisition enzyme of leucine aminopeptidase showed the strongest preferences for low moisture pulses in SL. These results indicated that shrub encroachment retained certain microbes with an advanced ability to acquire to C and N from dry and infertile soil in SL. Although a P-acquisition enzyme of alkaline phosphatase showed a decreasing trend along the transition from DG to SL, similar like those C- and N- acquisition enzymes, it was not sensitive to varying moisture levels, suggesting that alkaline phosphatase was affected by other soil physicochemical properties rather than soil moisture. The joint analysis of soil extracellular enzymes and nutrients indicated that microbial biomass carbon played a more important role than other soil characteristics in determining soil extracellular enzyme activities along the transition from DG to SL. Future research on dissecting soil microbial communities is warranted to better understand the microbiological mechanisms behind these phenomena in the shrub encroachment process.
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Affiliation(s)
- Yanan Zhao
- School of Agriculture, Ningxia University, Yinchuan, China; Key Laboratory for Restoration and Reconstruction of Degraded Ecosystems in Northwestern China of Ministry of Education, Ningxia University, Yinchuan, China
| | - Hongmei Wang
- School of Agriculture, Ningxia University, Yinchuan, China; Key Laboratory for Restoration and Reconstruction of Degraded Ecosystems in Northwestern China of Ministry of Education, Ningxia University, Yinchuan, China.
| | - Tiandou Guo
- School of Agriculture, Ningxia University, Yinchuan, China; Key Laboratory for Restoration and Reconstruction of Degraded Ecosystems in Northwestern China of Ministry of Education, Ningxia University, Yinchuan, China
| | - Zhili Li
- School of Agriculture, Ningxia University, Yinchuan, China; Key Laboratory for Restoration and Reconstruction of Degraded Ecosystems in Northwestern China of Ministry of Education, Ningxia University, Yinchuan, China
| | - Wenbao Mi
- School of Geography and Planning, Ningxia University, Yinchuan, China
| | - Zhe Cao
- School of Agriculture, Ningxia University, Yinchuan, China.
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Li J, Ravi S, Wang G, Van Pelt RS, Gill TE, Sankey JB. Woody plant encroachment of grassland and the reversibility of shrub dominance: Erosion, fire, and feedback processes. Ecosphere 2022. [DOI: 10.1002/ecs2.3949] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Affiliation(s)
- Junran Li
- Department of Geosciences The University of Tulsa Tulsa Oklahoma USA
| | - Sujith Ravi
- Department of Earth and Environmental Science Temple University Philadelphia Pennsylvania USA
| | - Guan Wang
- Department of Geosciences The University of Tulsa Tulsa Oklahoma USA
| | - R. Scott Van Pelt
- Wind Erosion and Water Conservation Research USDA‐ARS Big Spring Texas USA
| | - Thomas E. Gill
- Department of Earth, Environmental and Resource Sciences and Environmental Science & Engineering Program University of Texas at El Paso El Paso Texas USA
| | - Joel B. Sankey
- Southwestern Biological Science Center, Grand Canyon Monitoring and Research Center U.S. Geological Survey Flagstaff Arizona USA
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Pierce NA, Archer SR, Bestelmeyer BT. Competition suppresses shrubs during early, but not late, stages of arid grassland–shrubland state transition. Funct Ecol 2019. [DOI: 10.1111/1365-2435.13336] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Nathan A. Pierce
- School of Natural Resources and the Environment University of Arizona Tucson Arizona
| | - Steven R. Archer
- School of Natural Resources and the Environment University of Arizona Tucson Arizona
| | - Brandon T. Bestelmeyer
- United States Department of Agriculture‐Agricultural Research Service Jornada Experimental Range, Jornada Basin Long Term Ecological Research Program New Mexico State University Las Cruces New Mexico
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