Spatial and Temporal Patterns of Xylem Water Potential in Juniperus ashei Seedlings

Wayne, Rob; Auken, O. W. Van

doi:10.2307/3672901

Cited by 10 publications

(3 citation statements)

References 31 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The highest growth rates were found for J. ashei seedlings growing in the edge habitats, which has not been previously reported, though high irradiance is a suggested requirement for the growth of Juniperus seedlings ͑Burkhardt and Tisdale 1976; McKinley and Van Auken 2004͒. The conditions present beneath the canopy of an adult tree or shrub should be less extreme compared to the associated open areas and these sites could be more favorable for the survival of newly emerging seedlings ͑Breshears et al 1997Anderson et al 2001;Wayne and Van Auken 2002;Phillips and Barnes 2003͒. We report significant relationships between emergence and mortality of J. ashei seedlings and temperature and rainfall. Seedling appearance was significantly, inversely related to temperature, with the greatest number found during the coolest months of both years of the study, following higher rainfall by one to four months.…”

Section: Discussionmentioning

confidence: 75%

Survival and growth of Juniperus seedlings in Juniperus woodlands

2005

View full text Add to dashboard Cite

Juniperus woodlands are widely distributed in western North America. Few studies of seedling emergence, longterm survival, growth or mortality of the dominant Juniperus spp. in these woodlands have been carried out. Consequently, regeneration dynamics in these woodlands are poorly understood. Juniperus ashei is the dominant woody plant in the majority of woodland and savanna communities of the Edwards Plateau region in central Texas. We examined the emergence, mortality and growth of various spatial and temporal cohorts of J. ashei seedlings over an eight or nine-year period. Greatest emergence was found during the cool, mostly winter months and under the canopy of mature J. ashei trees. Emergence was significantly inversely related to temperature and significantly linearly related to rainfall, but only if the monthly rainfall and emergence were offset by one to four months. Greatest survival occurred below the J. ashei canopy, but greatest growth was at the canopy edge. Emerging seedlings were not from the current year's seed crop, but from one or more previous year's seed crops. Greatest mortality occurred mostly during the summer months and in the grassland habitat. There was a significant inverse logarithmic or exponential relationship between mean monthly temperature and mean monthly mortality. A large number of J. ashei seedlings or immature plants with reduced growth were found beneath the canopy of mature trees. These plants seem to serve as a seedling bank, providing the source of recruitment into the population should the overstory trees be removed. Survival of the two canopy cohorts with known emergence dates declined with time ͑negative exponential function͒ and was 1.0-3.4% after eight or nine years depending on the cohort. The pre-existing cohort seemed to have constant mortality ͑and presumably replacement͒, with about 8% of the population dying each year. Higher growth rates for seedlings were found at the edge of the established woodland canopy, which suggests that conditions in the edge habitat or possibly in canopy gaps are best for growth beyond the seedling stage.

show abstract

Section: Discussionmentioning

confidence: 75%

Survival and growth of Juniperus seedlings in Juniperus woodlands

2005

View full text Add to dashboard Cite

show abstract

“…The woodland canopy and season are major factors attenuating light, but also affect water availability and temperature (Hutchinson and Matt, 1977;Baldocchi et al, 1984;Breshears et al, 1998;Baldocchi and Wilson, 2001;Wayne and Van Auken, 2004;Breshears, 2008). In arid and semiarid communities, water availability is a major factor affecting plant growth and survival (Fowler and Dunlap, 1986;Donovan and Ehleringer, 1992;Bragg et al, 1993;Breshears et al, 1997;Yager and Smeins, 1999;Wayne and Van Auken, 2002). When water becomes limiting, stomatal closure is initiated to conserve hydraulic conductance, preventing catastrophic cavitation, and maintain cellular processes (Tyree and Sperry, 1989;Collatz et al, 1991;Dewar, 2002;Chaves et al, 2003;Tuzet et al, 2003;Galmé s et al, 2007).…”

Section: Introductionmentioning

confidence: 98%

Light responses of Carex planostachys from various microsites in a Juniperus community

Wayne

Auken

2009

Journal of Arid Environments

View full text Add to dashboard Cite

“…For example, large portions of the Intermountain West have been encroached by Western juniper (Juniperus occidentalis) at mid-to low-elevations (Miller and Rose, 1995;Weisberg et al, 2007;Bradley and Fleishman, 2008), while semi-arid grasslands of the south-west at lower elevations have been encroached by velvet or honey mesquite or their hybrids (Prosopis velutina and Prosopis glandulosa; Archer et al, 1988;Schlesinger et al, 1990;Van Auken, 2000;Browning et al, 2008). J. occidentalis is a drought tolerant evergreen tree with an extensive but shallow root system and no central taproot (Hall, 1952;Dealy, 1990), while members of the Prosopis genus are among the most deep-rooted tree species in the world (Phillips, 1963 Like J. occidentalis, J. ashei is also evergreen, chiefly shallow-rooted, and extremely drought tolerant (Owens, 1996;Wayne and Van Auken, 2002;Schwinning, 2008). On sites with highly fractured bedrock, roots of this species have been found in caves 9 m from the surface (Jackson et al, 1999), however, where geology prohibits the formation of deep roots, J. ashei appears to persists without deep taproots, relying instead on an extensive system of shallow fibrous roots (Thurow and Hester, 1997).…”

Section: Introductionmentioning

confidence: 99%

Biogeography of woody encroachment: why is mesquite excluded from shallow soils?

Eggemeyer

Schwinning

2009

Ecohydrology

View full text Add to dashboard Cite

While some studies aim to generalise the attributes of woody encroachers, examining their functional differences across biogeographic regions may also be instructive. Most of Texas is encroached by Prosopis glandulosa, but on the eastern Edwards Plateau, a limestone plateau with thin soils, P. glandulosa is rare and Juniperus ashei is dominant. We hypothesised that P. glandulosa is excluded from sites where bedrock at a depth of 1 m or less restricts the development of taproots, thus rendering this normally deep-rooted species too vulnerable to drought. To test this idea, we monitored the physiological status of the two species on a site where both species were encroaching and the soil was 1Ð5-2Ð5 m deep, thus relatively deep for the Edwards Plateau region but not for regions where P. glandulosa dominates. Data were collected across three tree size classes from May to November 2006. Stem water potentials were similar across species and water potentials and photosynthetic rates decreased with tree size. Based on isotopic evidence, the effective rooting depth of P. glandulosa increased with tree size, but not in J. ashei. P. glandulosa had a higher rate of leaf gas exchange overall as expected for a drought-avoider; except for large trees during a summer drought, when species differences in photosynthesis rates diminished and the stomatal conductance for J.ashei exceeded that of P. glandulosa. We speculate that restrictions of soil depth may limit the invasiveness of P. glandulosa in part through negative effects on large trees, which may lower fecundity.

show abstract

Spatial and Temporal Patterns of Xylem Water Potential in Juniperus ashei Seedlings

Cited by 10 publications

References 31 publications

Survival and growth of Juniperus seedlings in Juniperus woodlands

Survival and growth of Juniperus seedlings in Juniperus woodlands

Light responses of Carex planostachys from various microsites in a Juniperus community

Biogeography of woody encroachment: why is mesquite excluded from shallow soils?

Contact Info

Product

Resources

About