Cambial phenology in Abies pindrow (Pinaceae) along an altitudinal gradient in northwestern Himalaya

Abstract

Climate change is expected to be heterogeneous across the world, with high impacts on the Himalayan ecosystems. There is a need to precisely document cambial phenology and wood formation in these regions to better understand climate-growth relationships and how trees face a warming climate. This study describes the dynamics of cambial phenology in pindrow fir (Abies pindrow) along its altitudinal gradient in the Himalaya. The stages of xylem phenology, and the duration and rate of wood formation were assessed from anatomical observations during the growing season from samples collected weekly from three sites at various altitudes (2392–2965 m a.s.l.) over two years. There were significant differences in the duration and rate of cell formation along the altitudinal gradient, which decreased at increasing altitudes. The growing season duration decreased by 5.2 and 3.7 days every 100 m of increase in altitude in 2014 and 2015, respectively, while the rate of cell formation decreased from 0.38 and 0.44 cells /day to 0.29 and 0.34 cells/day in 2014 and 2015, respectively. Cell production decreased from 63.3 and 67.0 cells to 38.3 and 45.2 cells with a decrease of 4.3 and 3.8 cells per 100 m increase in altitude in 2014 and 2015, respectively. The higher precipitation in 2015 increased the growth rate and resulted in a higher xylem production. Our findings give new insights into the dynamics of cambial phenology and help in better understanding of the potential impacts of climate change on tree growth and forest productivity of Himalayan forests.

Intra-annual dynamics of cambial and xylem phenology in subalpine conifers at Deogyusan National Park in the Republic of Korea

“…Several past studies reported that intra-annual xylem formation follows a sigmoid curve [32,33,36,37,48,49,53,62,73]. This intra-annual dynamics of wood-formation was confirmed as well in our study of coniferous tree species growing at a subalpine site in the Republic of Korea.…”

“…Republic of Korea was observed around 1-4 weeks later than the initiation of the cambial activity. Such restricted time delay was also reported for conifers at high altitudes [33,48,71].…”

“…The cambium cells are vulnerable meristematic tissues under cold condition [39]. Therefore, cambium cell division in the subalpine zones starts later than the trees at low elevations [33,48,67]. Prior studies stated that in the Republic of Korea [50,52,60], conifer trees, such as Chamaecyparis pisifera, Pinus koraiensis and Pinus densiflora, growing under 600 m a.s.l.…”

“…However, the mean DCA of the subalpine conifers was found to be similar to the DCAs of the conifers located higher than 1280 m a.s.l. in the north-western Himalayas in India, which is around 120-150 days [33], and at 3850 m a.s.l. in the south-eastern Tibetan Plateau in China which is around 119 days [71].…”

“…The radial growth integrates exogenous influences as well as endogenous factors, which are archived in each annual ring [28,29]. Unlike the annual rings, the cambial activity and xylem formation can be monitored in a short time rather than a growing season [30][31][32][33]. Based on these advantages, researchers explored the intra-annual dynamics of cambium, the xylem phenology and their growth rates to achieve a deeper insight into the treegrowth strategy depending upon climate [32,[34][35][36][37].…”