Facilitation of Seedling Establishment: Reduction in Irradiance Enhances Winter Growth of Eucalyptus pauciflora

Egerton, John J. G.; Banks, J. C.; Gibson, Ann L.; Cunningham, Ross B.; Ball, Marilyn C.

doi:10.2307/177220

Cited by 47 publications

(55 citation statements)

References 55 publications

(125 reference statements)

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“…Certainly, postfire tree seedling regeneration can be suppressed by frost in the first few years after fire (Wimbush and Forrester, 1988). There is no way to confirm our suggested longer-term mechanism here, although there are numerous examples whereby experimental shading of E. paucifiora seedlings in frost-prone areas improves winter survival and growth (e.g., Slatyer, 1976;Ball et al, 1991;Egerton et al, 2000). However, given that some seedlings have established well beyond the influence of protective tree canopies, changes to factors that affect seedling recruitment at local-and regional-scales may also need to be invoked to help explain the more recent success of seedlings.…”

Section: Temperature and Precipitation Records Across The Boundarymentioning

confidence: 72%

Recent Forest Encroachment into Subalpine Grasslands near Mount Hotham, Victoria, Australia

Wearne

Morgan

2001

Arctic, Antarctic, and Alpine Research

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Establishment of forest trees into subalpine grasslands near Mt. Hotham, southeast Australia, was quantified in 1998 across long-established forestgrassland boundaries in belt transects at four sites. Although the grasslands varied in their dominant species and groundlayer biomass, tree encroachment (principally by Eucalyptus paucijlora) occurred at all sites. Tree encroachment is a recent and synchronous event; all invading saplings were :S31-yr-old and the majority (54%) established between 1991 and 1995. Most sapling establishment (66%) occurred within 5 m of the forest-grassland boundary where the number of plants present was positively associated with the amount of overhanging tree cover at three of the four sites. No correlation between encroachment and groundcover type or biomass, however, was found at any site. Some of the recently established plants are now small trees (1-8 m in height) and have become reproductive, indicating that establishment in grasslands is successful, making ecotone shifts possible. Any changes in boundary position, however, will be slow given the limited distance that trees established from the forest edge. Tree encroachment near Mt. Hotham is likely the outcome of small-scale (e.g., regeneration microsite) and landscape-scale (e.g., climate, grazing) processes that require further clarification.

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Section: Temperature and Precipitation Records Across The Boundarymentioning

confidence: 72%

Recent Forest Encroachment into Subalpine Grasslands near Mount Hotham, Victoria, Australia

Wearne

Morgan

2001

Arctic, Antarctic, and Alpine Research

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“…Egerton et al (2000) found that protected seedlings of Eucalyptus pauciflora at high elevations were less photoinhibited than those in the open. Smith (1999, 2000) found that Abies lasiocarpa and Picea englemanii seedlings were most common in habitats with ;40-80% of the overhead area open to the sky, and demonstrated that seedlings in these habitats benefited from the way in which overstory canopies ameliorated nighttime temperature and lowered light levels.…”

Section: Discussionmentioning

confidence: 93%

FACILITATION BYPINUS FLEXILISDURING SUCCESSION: A HIERARCHY OF MECHANISMS BENEFITS OTHER PLANT SPECIES

Baumeister

Callaway

2006

Ecology

121

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Abstract. Studies of facilitation have primarily been limited to single mechanisms, species, or environments. We examined interacting mechanisms governing the facilitative effects of Pinus flexilis on two later successional understory species, Pseudotsuga menziesii and Ribes cereum, in different microhabitats and seasons at the ecotone between the Rocky Mountain forests and Great Plains grasslands in Montana, USA. In field surveys, 69% of Pseudotsuga and 91% of Ribes were located beneath P. flexilis even though P. flexilis subcrowns accounted for a small proportion of available habitat. For three years, we monitored the survival of Pseudotsuga and Ribes seedlings experimentally planted beneath P. flexilis and in the open at a windward and a leeward site. Survival of both species was highest beneath P. flexilis at a site topographically protected from strong unidirectional winds (38% for Pseudotsuga and 63% for Ribes), and lowest at a windward site and in the open where tree crowns did not provide shelter from winds (2% and 6%, respectively). These results suggest that wind amelioration contributed to the facilitative effect of P. flexilis. However, even at the leeward site, where wind speed was low, survival of Pseudotsuga and Ribes was higher beneath P. flexilis, suggesting the importance of shade. To explore the relative importance of different mechanisms, we designed an experiment with six treatments: ''shade,'' ''shade þ wind,'' ''shade þ drift,'' ''wind,'' ''drift,'' and a ''control.'' After two years, we found shade to be of overwhelming importance for the survival of Pseudotsuga and Ribes. Without shade, no other treatments were significant, but once shade was provided, wind amelioration and snow pack accumulation increased survival of Pseudotsuga, suggesting that these different facilitative mechanisms functioned in a nested hierarchical manner: some mechanisms were important only when others were already functioning. Many studies have demonstrated multiple interacting mechanisms in the way that plants interact, but to our knowledge hierarchical interactive processes have not been previously documented. If the effects of positive or competitive mechanisms are often hierarchical, then studies of isolated mechanisms may not accurately assess their importance in nature.

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“…Moreover, other stresses, such as drought and high-temperature stress, as well as wind-blown ice, snow, and dust, can also reduce seedling survival (Tranquillini, 1979;Baskin & Baskin, 1998). Also, PSII responses to freezing temperatures can be complicated by high PFD, which has been shown to affect recruitment in seedlings of other species (Ball et al, 1997;Egerton et al, 2000). Given the broad distribution of A. tridentata across North America, differences among populations in the ability to tolerate freezing would seem likely when compared across larger scales.…”

Section: Discussionmentioning

confidence: 99%

Microclimate, freezing tolerance, and cold acclimation along an elevation gradient for seedlings of the Great Basin Desert shrub, Artemisia tridentata

Loik

Redar

2003

Journal of Arid Environments

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Facilitation of Seedling Establishment: Reduction in Irradiance Enhances Winter Growth of Eucalyptus pauciflora

Cited by 47 publications

References 55 publications

Recent Forest Encroachment into Subalpine Grasslands near Mount Hotham, Victoria, Australia

Recent Forest Encroachment into Subalpine Grasslands near Mount Hotham, Victoria, Australia

FACILITATION BYPINUS FLEXILISDURING SUCCESSION: A HIERARCHY OF MECHANISMS BENEFITS OTHER PLANT SPECIES

Microclimate, freezing tolerance, and cold acclimation along an elevation gradient for seedlings of the Great Basin Desert shrub, Artemisia tridentata

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