Controls of seed quantity and quality on seedling recruitment of smith fir along altitudinal gradient in southeastern Tibetan Plateau

Abstract

Abstract

Treeline Research—From the Roots of the Past to Present Time. A Review

“…It has been and still is being debated, whether the scarcity of viable seeds or paucity of safe sites are more restrictive to tree establishment within and above the current treeline ecotone (e.g., [93,109,168,171,182,186,361,[368][369][370][371][372][373][374][375][376][377][378]). Whatsoever, increased production and availability of viable seeds will not necessarily initiate successful seedling recruitment (e.g., [171,182,186,261,367,[379][380][381]) Altogether, seed-based regeneration in and above the treeline ecotone depends on the availability of viable seeds, varying locally, and on the distance from the seed sources, suitable seed beds, and multiple Forests 2020, 11, 38 9 of 31 disturbances (e.g., [2,3,160,191,261,353,355,361,366,367]). Last but not least, mycorrhization is essential for a successful seedling establishment in and especially above the treeline ecotone, where it is closely related to locally varying site conditions (e.g., [382][383][384][385][386]).…”

Seedling Survival at Timberline Is Critical to Conifer Mountain Forest Elevation and Extent

“…For example, studies on the relationship between altitude and seed mass are mixed, with some showing declines with altitude (e.g., Tranquillini, 1979;Marcora et al, 2013) or increases (Holm, 1994;Kollas et al, 2012). These differences are likely site and species specific, as well as dependent on both biotic (e.g., seed predation; Jameson et al, 2015) and abiotic conditions (Cuevas, 2000;Holtmeier, 2009;Wang et al, 2016). Parent-tree abundance within close proximity to the timberline boundary may also be critical (Kroiss and HilleRisLambers, 2015;Lyu et al, 2016;Wang et al, 2016).…”

“…These differences are likely site and species specific, as well as dependent on both biotic (e.g., seed predation; Jameson et al, 2015) and abiotic conditions (Cuevas, 2000;Holtmeier, 2009;Wang et al, 2016). Parent-tree abundance within close proximity to the timberline boundary may also be critical (Kroiss and HilleRisLambers, 2015;Lyu et al, 2016;Wang et al, 2016). Broadly, subalpine forest migration upward into the alpine could be constrained by seed-source limitation, along with low seedling survival or the low occurrence of favorable microsites (Smith et al, 2009;Wang et al, 2016;Kueppers et al, 2017).…”

“…Parent-tree abundance within close proximity to the timberline boundary may also be critical (Kroiss and HilleRisLambers, 2015;Lyu et al, 2016;Wang et al, 2016). Broadly, subalpine forest migration upward into the alpine could be constrained by seed-source limitation, along with low seedling survival or the low occurrence of favorable microsites (Smith et al, 2009;Wang et al, 2016;Kueppers et al, 2017). Comprehensive studies comparing the combination of seed abundance, germination success, and new seedling establishment near conifer timberlines do not exist.…”

Anatomical and hydraulic responses to desiccation in emergent conifer seedlings

“…Extensive first‐year seedling mortality, which can be greater than 99% (Cui and Smith, 1991; Johnson and Smith, 2005; Mellmann‐Brown, 2005) suggests a life history bottleneck that is fundamentally important to determining rates of recruitment, population persistence, and migration (Haig et al, 1941; Burns and Honkala, 1990; Cui and Smith, 1991; Johnson et al, 2011; Calama et al, 2015; Reinhardt et al, 2015; Clark et al, 2016; Wang et al, 2016; Conlisk et al, 2017; Brodersen et al, 2019). Unlike saplings and adult trees, young seedlings are exposed to dramatic ground‐level microclimate variability (Germino and Smith, 1999, 2001; Johnson and Smith, 2005; Maher et al, 2005; Johnson et al, 2011).…”