Mediterranean climate effects. II. Conifer growth phenology across a Sierra Nevada ecotone.
Mediterranean climate effects. II. Conifer growth phenology across a Sierra Nevada ecotone.
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地中海气候影响。
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
M. Barbour
中科院分区：
文献类型：
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作者：
E. Royce;M. Barbour
在加利福尼亚州内华达山脉最南端的地中海山地生境中，对低海拔针叶松、冷杉和高海拔樟子松、冷杉的生长和木质部水势进行了监测。径向树干生长在积雪融化后2周开始，条件是最高气温已达到21°C，在夏季干旱开始时，黎明前水势迅速下降时，径向树干生长结束。如果最低气温对于松树来说是在-4℃以上，对于冷杉来说是+2.5℃，那么领导者的生长就是在一个固定的日期或之后开始的。领头羊生长的线索被推断为光周期。当达到确定的节间长度∼1 mm或黎明前水势迅速下降时，领导者的生长结束。长白冷杉生长速度快于低海拔树种，但生长期较短，其主干年生长量仅为35 mm/年，而低海拔树种为50 mm/年。在没有早期干旱的情况下，针叶生长同样是确定的。这种生长物候有助于确定物种在交错带上的分布。
Growth and xylem water potential of the lower elevation conifers Pinus jeffreyi and Abies concolor and the higher elevation Pinus monticola and Abies magnifica were monitored in their montane Mediterranean habitat of the southernmost Sierra Nevada mountains of California. Measurements were made across the ecotone between the midmontane and upper montane forests and through light and heavy snowfall years.Radial stem growth, averaging ∼1.5 mm/yr, started 2 wk after snow melt, providing that maximum air temperatures had reached 21°C, and ended when predawn water potentials fell rapidly at the onset of the summer drought. Leader growth started on or after a fixed date, providing that minimum air temperatures were above -4°C for Pinus species or +2.5°C for Abies species. The cue for leader growth was inferred to be photoperiodic. Leader growth ended when either a determinate internode length of ∼1 mm was reached or predawn water potentials fell rapidly. Abies magnifica grew more rapidly than the low-elevation species, but had a shorter growth period; its annual leader growth, as a consequence, was only 35 mm/yr vs. 50 mm/yr for the low-elevation species. Needle growth was similarly determinate in the absence of early drought. This growth phenology contributes to determining species distribution across the ecotone.