Woody Plants in Grasslands: Post‐encroachment Stand Dynamics

Browning, Dawn M.; Archer, Steven R.; Asner, Gregory P.; McClaran, Mitchel P.; Wessman, Carol A.

doi:10.1890/07-1559.1

Cited by 126 publications

(142 citation statements)

References 58 publications

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“…Previous studies on temporal patterns of shrub colonization have mostly focused on the role of site conditions (Browning et al, 2008;Davies et al, 2010;Levick and Rogers, 2011), fire (Malkisnon et al, 2011) and grazing (Roques et al, 2001). We observed that aspect and rock cover were significant predictors of shrub patch density.…”

Section: Discussionmentioning

confidence: 53%

“…Visual interpretation of generated images was performed to mark the presence of patches. Our sample unit was a shrub patch, defined as a woody plant Browning et al, 2008). In each texture layer, the same author (VR) marked the location of each shrub patch within the EU, to minimize observer bias.…”

Section: Aerial Photography Interpretationmentioning

confidence: 99%

“…On the other hand, the formation of new patches dominated by Q. coccifera may also rely on successful acorn dispersal and the availability of safe sites (Eriksson and Ehrlén, 1992). These safe sites may become saturated early, when patch density reaches an asymptote (Browning et al, 2008). However, the slow growth rate of planted Q. coccifera seedlings (Vilagrosa et al, 2014(Vilagrosa et al, , 2003 suggests that seedling establishment was not the main process behind the increase in Q. coccifera patches.…”

Section: Species Identity and Non-linear Patterns Of Shrub Colonizationmentioning

confidence: 99%

“…Information derived from time series of aerial photographs has advanced our knowledge of the dynamics and extent of shrub encroachment (Briggs et al, 2002;Peters et al, 2006). However, research on the drivers of shrub colonization has mostly focused on the effect of physical factors, particularly soil properties and topographic features such as aspect and elevation (Browning et al, 2008;Davies et al, 2010;Levick and Rogers, 2011) or grazing (Bartolomé et al, 2005;Roques et al, 2001;Ward et al, 2014). In contrast, the identity of the colonizing shrub species as major driver of shrub expansion has seldom been studied.…”

Section: Introductionmentioning

confidence: 99%

“…Variable colonization dynamics can also result from changes in climatic conditions, such as water availability during the colonization process (Browning et al, 2008). Thus, coupling species-level information on colonization with data on past climatic events may provide further insights into the linkages between climate and vegetation and, therefore, on the mechanism behind shrub colonization (Munson et al, 2015).…”

Section: Introductionmentioning

confidence: 99%

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Water availability and species identity control shrub colonization in abandoned semiarid steppes

Rolo

Amat

Cortina

2016

Agriculture, Ecosystems & Environment

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Highlights• Shrub cover has increased in former agricultural lands worldwide.• Colonization rates are explained by the identity of shrub species.• Species idiosyncratic effects are contingent on water availability.• Abiotic attributes, such as aspect or rock cover, played a lesser role. 1 AbstractThe increase in shrub cover and density is a widespread phenomenon in drylands worldwide. Its causes and consequences are complex and strongly idiosyncratic. Detailed knowledge of the rate of shrub colonization, and its abiotic and biotic drivers is crucial to fully understand and manage these areas. We used a set of aerial photographs (1956, 1978, 1985, 1998 and 2009) describing early, gradual and late recruitment, respectively. Differences in shrub patch colonization rate were related to the identity of patch-forming species, but contingent on water availability. Total increases in shrub patch density were larger when patches were dominated by late colonizer species. Overall shrub patch dynamics was mostly related to the identity of patchforming species and climatic conditions, and to a lesser extent physical factors such as aspect and rock cover. Given the sensitivity of patch-forming species to climatic conditions, new challenges for steppe management will emerge over the next decades. Species able to thrive under harsh conditions may increase their dominance at the expense of species adapted to less demanding conditions.

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Section: Discussionmentioning

confidence: 53%

Section: Aerial Photography Interpretationmentioning

confidence: 99%

Section: Species Identity and Non-linear Patterns Of Shrub Colonizationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Water availability and species identity control shrub colonization in abandoned semiarid steppes

Rolo

Amat

Cortina

2016

Agriculture, Ecosystems & Environment

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Using observations and a distributed hydrologic model to explore runoff thresholds linked with mesquite encroachment in the Sonoran Desert

Pierini

Vivoni

Robles-Morúa

et al. 2014

Water Resources Research

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Woody plant encroachment is a world wide phenomenon with implications on the hydrologic cycle at the catchment scale that are not well understood. In this study, we use observations from two small semiarid watersheds in southern Arizona that have been encroached by the velvet mesquite tree and apply a distributed hydrologic model to explore runoff threshold processes experienced during the North American monsoon. The paired watersheds have similar soil and meteorological conditions, but vary considerably in terms of vegetation cover (mesquite, grass, bare soil) and their proportions with one basin having undergone mesquite removal in 1974. Long-term observations from the watersheds exhibit changes in runoff production over time, such that the watershed with more woody plants currently has less runoff for small rainfall events, more runoff for larger events, and a larger runoff ratio during the study periods (summers 2011 and 2012). To explain this observation, we first test the distributed model, parameterized with highresolution (1 m) terrain and vegetation distributions, against continuous data from an environmental sensor network, including an eddy covariance tower, soil moisture, and temperature profiles in different vegetation types, and runoff observations. We find good agreement between the model and observations for simultaneous water and energy states and fluxes over a range of measurement scales. We then identify that the areal fraction of grass (bare soil) cover determines the runoff response for small (large) rainfall events due to the dominant controls of antecedent wetness (hydraulic conductivity). These model-derived mechanisms explain how woody plants have differential effects on runoff in semiarid basins depending on precipitation event sizes.

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Impact of land surface states within the flux footprint on daytime land‐atmosphere coupling in two semiarid ecosystems of the Southwestern U.S.

Anderson

Vivoni

2016

Water Resources Research

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Land surface states play important roles in the turbulent exchanges between ecosystems and their overlying atmosphere. Field methods to estimate turbulent fluxes have time-variable source areas, while land surface observations are typically obtained at single plots with a smaller measurement scale. In this study, we characterize land-atmosphere interactions in two semiarid ecosystems in the southwestern U.S. At each study site, we combine the eddy covariance method with a distributed network of soil moisture and temperature sensors, high-resolution imagery of the spatial distribution of vegetation and soil patches, and novel spatiotemporal analyses to characterize the turbulent flux footprint analytically and identify the soil moisture, temperature, and vegetation conditions underlying the eddy covariance measurements. Four methods for aggregating the land surface observations to the scale of the daily flux footprint are tested. Our results reveal a large degree of spatial variability in the footprint, with stronger variations in soil moisture than in soil temperature. Single plot measurements are less reliable than the distributed network in capturing footprint conditions, particularly for soil moisture. Furthermore, a marked improvement is observed in the relations between turbulent fluxes and land surface states for methods capturing the footprint variability. We also identify that the composition of vegetation and soil patches in the time-variable source area affects the relative magnitudes of the turbulent fluxes and the partitioning of evapotranspiration. Our study points to the importance of monitoring the spatial distribution of land surface states (e.g., soil moisture and temperature) and vegetation and soil patches when assessing land-atmosphere interactions.

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Woody Plants in Grasslands: Post‐encroachment Stand Dynamics

Cited by 126 publications

References 58 publications

Water availability and species identity control shrub colonization in abandoned semiarid steppes

Water availability and species identity control shrub colonization in abandoned semiarid steppes

Using observations and a distributed hydrologic model to explore runoff thresholds linked with mesquite encroachment in the Sonoran Desert

Impact of land surface states within the flux footprint on daytime land‐atmosphere coupling in two semiarid ecosystems of the Southwestern U.S.

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