The seasonal course of physiological processes in Juniperus occidentalis

Miller, P. M.; Eddleman, Lee E.; Miller, Jeffrey M.

doi:10.1016/0378-1127(92)90145-y

Cited by 28 publications

(20 citation statements)

References 37 publications

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“…The increase in gas exchange for live oak coincided with initiation of new leaf growth in the spring. Juniper showed limited fluctuations in gas exchange, in relation to time of year or new leaf growth, similar to results from other studies of juniper physiology (Miller et al, 1992;Owens and Schreiber, 1992). SLA of live oak increased in April and June indicating much greater leaf area per unit of weight (Table I), whereas SLA of juniper needles which are retained for multiple years did not change.…”

Section: Seasonal and Environmental Influences On Gas Exchangesupporting

confidence: 78%

Carbon exchange and water loss from two evergreen trees in a semiarid woodland

Bendevis¹,

Owens²,

Heilman³

et al. 2009

Ecohydrology

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Ashe juniper (Juniperus ashei Buchholz) has encroached into the historical grasslands of the Edwards Plateau, an environmentally sensitive area that serves as the recharge zone for the Edwards Aquifer. An understanding of gas exchange and water relations of the two dominant tree species, Ashe juniper and live oak (Quercus virginiana P. Mill. var. fusiformis), is important to assess the trade-offs between potential aquifer recharge and carbon storage during woody plant encroachment. Over a 12-month period, juniper consistently had lower instantaneous carbon assimilation, transpiration rates and stomatal conductance than live oak. Oak exhibited greater seasonal variation and a greater correlation with antecedent precipitation in gas exchange measurements, whereas juniper did not respond to precipitation events. The consistent low rates of gas exchange and stomatal responses in juniper could indicate shallower rooting structure and/or limitation of hydraulic conductivity, as well as lower photosynthetic capacity. The higher rates of photosynthesis, transpiration and stomatal conductance exhibited by live oak during drought suggest alternate sources of soil moisture and possibly a deeper rooting pattern than Ashe juniper. Water-use efficiency was greater for juniper than for live oak suggesting that juniper may sequester more carbon than oak trees for a given amount of water. This finding implies that Ashe juniper may not be the extravagant water user previously reported but may serve an important role in carbon sequestration.

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Section: Seasonal and Environmental Influences On Gas Exchangesupporting

confidence: 78%

Carbon exchange and water loss from two evergreen trees in a semiarid woodland

Bendevis¹,

Owens²,

Heilman³

et al. 2009

Ecohydrology

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“…Second, the isotopic signatures of the components of the respiration flux may change over time. For example, soil moisture at our sites changes dramatically throughout the year (Gholz 1982;Miller et al 1992;Anthoni et al 1999;Law et al 2000), affecting C and N mineralization rates and altering the organic substrates available for decomposition. Activity of soil microbes, macrofauna, and mycorrhizae are likely to differ seasonally in response to soil moisture and nutrient availability (e.g., , and their isotopic contribution to the total ecosystem CO 2 flux will change as different substrates are utilized.…”

Section: Discussionmentioning

confidence: 99%

“…a Site E is an AmeriFlux long-term CO 2 flux study site (Metolius Research Natural Area), and site F is near (but not identical to) the sites used by Gholz (1982) and Miller et al (1992) b Sites E and F have two age and height classes c Measured precipitation at site E is the mean of 1996-2000 any points where the absolute value of the residual was greater than 2 standard deviations (SDs) of all the absolute residuals, (3) recalculating the GM regression with the remaining points, and (4) repeating steps 2 and 3 until all residuals were within 2 SD. This resulted in the removal of 64 individual air samples from analysis (6.0% of the total).…”

Section: Air Samplingmentioning

confidence: 99%

13C content of ecosystem respiration is linked to precipitation and vapor pressure deficit

et al. 2002

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Variation in the carbon isotopic composition of ecosystem respiration (δC) was studied for 3 years along a precipitation gradient in western Oregon, USA, using the Keeling plot approach. Study sites included six coniferous forests, dominated by Picea sitchensis, Tsuga heterophylla, Pseudotsuga menziesii, Pinus ponderosa, and Juniperus occidentalis, and ranged in location from the Pacific coast to the eastern side of the Cascade Mountains (a 250-km transect). Mean annual precipitation across these sites ranged from 227 to 2,760 mm. Overall δC varied from -23.1 to -33.1‰, and within a single forest, it varied in magnitude by 3.5-8.5‰. Mean annual δC differed significantly in the forests and was strongly correlated with mean annual precipitation. The carbon isotope ratio of carbon stocks (leaves, fine roots, litter, and soil organic matter) varied similarly with mean precipitation (more positive at the drier sites). There was a strong link between δC and the vapor saturation deficit of air (vpd) 5-10 days earlier, both across and within sites. This relationship is consistent with stomatal regulation of gas exchange and associated changes in photosynthetic carbon isotope discrimination. Recent freeze events caused significant deviation from the δC versus vpd relationship, resulting in higher than expected δC values.

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“…5). Similar relationships with winter climate may also exist for junipers (Chambers et al 1999, West et al 2008), but increases in disturbed and relatively open conditions would have favored juniper seedling survival and development, given its greater drought tolerance and ability to obtain water in open interspace environments, while discouraging pin˜on seedlings more dependent on shade and nurse plants (Meagher 1943, Miller et al 1992, Chambers et al 1999, Nowak et al 1999. Similar relationships with winter climate may also exist for junipers (Chambers et al 1999, West et al 2008), but increases in disturbed and relatively open conditions would have favored juniper seedling survival and development, given its greater drought tolerance and ability to obtain water in open interspace environments, while discouraging pin˜on seedlings more dependent on shade and nurse plants (Meagher 1943, Miller et al 1992, Chambers et al 1999, Nowak et al 1999.…”

Section: Climate Forcing Of Population Age Structuresmentioning

confidence: 94%

Historical fire and multidecadal drought as context for piñon–juniper woodland restoration in western Colorado

Shinneman

Baker

2009

Ecological Applications

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Fire is known to structure tree populations, but the role of broad-scale climate variability is less clear. For example, the influence of climatic "teleconnections" (the relationship between oceanic-atmospheric fluctuations and anomalous weather patterns across broad scales) on forest age structure is relatively unexplored. We sampled semiarid piñon-juniper (Pinus edulis-Juniperus osteosperma) woodlands in western Colorado, U.S.A., to test the hypothesis that woodland age structures are shaped by climate, including links to oceanic-atmospheric fluctuations, and by past fires and livestock grazing. Low-severity surface fire was lacking, as fire scars were absent, and did not influence woodland densities, but stand-replacing fires served as long-rotation (>400-600 years), stand-initiating events. Old-growth stands (>300 years old) were found in 75% of plots, consistent with a long fire rotation. Juniper and piñon age structures suggest contrasting responses during the past several centuries to dry and wet episodes linked to the Atlantic Multidecadal Oscillation (AMO) and Pacific Decadal Oscillation (PDO). Juniper density increased slightly during periods of drought, positive (warm) AMO (after approximately 10-year lag), and negative (cool) PDO. In contrast, piñon populations may still be recovering from a long, drought-filled period (AD 1620-1820), with pulses of recovery favored during cool AMO, warm PDO, and above-average moisture periods. Analysis of 20th-century tree establishment and instrumental climate data corroborate the long-term relationships between age structure and climate. After Euro-American settlement (AD 1881), livestock grazing reduced understory grasses and forbs, reducing competition with tree seedlings and facilitating climate-induced increases in piñons. Thus tree populations in these woodlands are in flux, affected by drought and wet periods linked to oceanic-atmospheric variability, Euro-American livestock grazing, and long-rotation, high-severity fires. Reductions in livestock grazing levels may aid ecological restoration efforts. However, given long-term fluctuations in tree density and composition, and expected further drought, thinning or burning to reduce tree populations may be misdirected.

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The seasonal course of physiological processes in Juniperus occidentalis

Cited by 28 publications

References 37 publications

Carbon exchange and water loss from two evergreen trees in a semiarid woodland

Carbon exchange and water loss from two evergreen trees in a semiarid woodland

13C content of ecosystem respiration is linked to precipitation and vapor pressure deficit

Historical fire and multidecadal drought as context for piñon–juniper woodland restoration in western Colorado

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