Abstract
Age plays an important role in regulating the intra-annual changes in wood cell development. Investigating the effect of age on intra-annual wood cell development would help to understand cambial phenology and xylem formation dynamics of trees and predict the growth of trees accurately. Five intermediate trees in each stand (total of 5 stands) in five age groupings of Chinese fir (Cunninghamia lanceolata Hook.) plantations in subtropical China were monitored on micro-cores collected weekly or biweekly from January to December in 2019. We modeled the dynamics of wood cell development with a mixed effects model, analyzed the age effect on intra-annual wood cell development, and explored the contribution of rate and duration of wood cell development on intra-annual wood cell development. We found a bimodal pattern of wood cell development in all age classes, and no matter the date of peak or the maximal number of cells the bimodal patterns were similar in all age classes. In addition, compared with the older trees, the younger trees had the longest duration of wood cell development because of the later end of wood cell development and a larger number of wood cells. The younger trees had the faster growth rate than the older trees, but the date of the maximal growth rate in older trees was earlier than younger trees, which led to the production of more wood cells in the younger trees. Moreover, we found that the number of cells in wood cell formation was mostly affected by the rate (92%) rather than the duration (8%) of wood cell formation.
Highlights
The intra-annual radial growth of trees can be monitored using dendrometers, pinning, and microcoring (Seo et al, 2007; Drew and Downes, 2009)
We found that there was a bimodal pattern in the dynamics of the cambial and enlarging phases and divided the wood cell development into two periods, which is similar to the pattern of conifer species (Juniperus thurifera, Pinus halepensis, and Pinus sylvestris) endemic to the western Mediterranean Basin (Spain, Morocco, France and Algeria) (Camarero et al, 2010)
The bimodal pattern of xylem formation was characterized by spring and autumn precipitation; in order to reduce the water consumption during the drought
Summary
The intra-annual radial growth of trees can be monitored using dendrometers, pinning, and microcoring (Seo et al, 2007; Drew and Downes, 2009). Compared with the other two methods, microcoring could monitor cambial cell division and the dynamics of xylem cell formation directly, and combined with paraffin sections to show the details of wood cell development (cambial division, enlarging, wall-thickening, and maturation) (Gruber et al, 2010; Kalliokoski et al, 2011; Lenz et al, 2013). Lundqvist et al (2018) reported that the annual growth, fiber and wood properties of Norway spruce [Picea abies (L.) Karst.] change dynamically, at young ages. K. Fu], young (43 ± 4 years) Smith fir had an earlier onset of xylogenesis, a longer growing season and a higher growth rate, resulting in a higher number of xylem cells (Li et al, 2012)
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