Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China

Intra-annual density fluctuation (IADF) is a structural modification of the tree ring in response to fluctuations in the weather. The expected changes in monsoon flow would lead to heterogeneous moisture conditions during the growing season and increase the occurrence of IADF in trees of the arid ec...

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Autores principales:	Jiani Gao, Sergio Rossi, Bao Yang
Formato:	article
Lenguaje:	EN
Publicado:	Frontiers Media S.A. 2021
Materias:	water availability IADF xylogenesis cambial activity Chinese pine cell enlargement Plant culture SB1-1110
Acceso en línea:	https://doaj.org/article/9e690e85c8c148fd96edb9d6d53422d4
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spelling	oai:doaj.org-article:9e690e85c8c148fd96edb9d6d53422d42021-11-22T05:30:17ZOrigin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China1664-462X10.3389/fpls.2021.777753https://doaj.org/article/9e690e85c8c148fd96edb9d6d53422d42021-11-01T00:00:00Zhttps://www.frontiersin.org/articles/10.3389/fpls.2021.777753/fullhttps://doaj.org/toc/1664-462XIntra-annual density fluctuation (IADF) is a structural modification of the tree ring in response to fluctuations in the weather. The expected changes in monsoon flow would lead to heterogeneous moisture conditions during the growing season and increase the occurrence of IADF in trees of the arid ecosystems of continental Asia. To reveal the timings and physiological mechanisms behind IADF formation, we monitored cambial activity and wood formation in Chinese pine (Pinus tabuliformis) during 2017–2019 at three sites in semi-arid China. We compared the dynamics of xylem formation under a drought event, testing the hypothesis that drought affects the process of cell enlargement and thus induces the production of IADF. Wood microcores collected weekly from April to October were used for anatomical analyses to estimate the timings of cambial activity, and the phases of enlargement, wall thickening, and lignification of the xylem. The first cells started enlargement from late April to early May. The last latewood cells completed differentiation in mid-September. Trees produced IADF in 2018. During that year, a drought in June limited cell production in the cambium, only 36% of the xylem cells being formed in IADF trees, compared to 68% in normal tree rings. IADF cells enlarged under drought in early July and started wall thickening during the rainfall events of late July. The drought restricted cell enlargement and affected wall thickening, resulting in narrow cells with wide walls. Cambium and cell enlargement recovered from the abundant rainfall, producing a new layer with large earlywood tracheids. IADF is a specific adaptation of trees to cope with water deficit events occurring during xylem formation. Our findings confirmed the hypothesis that the June-July drought induces latewood-like IADFs by limiting the process of cell enlargement in the xylem. Our finding suggests a higher occurrence of IADF in trees of arid and semi-arid climates of continental Asia if the changes to monsoon flows result in more frequent drought events during the earlywood formation in June.Jiani GaoJiani GaoJiani GaoSergio RossiSergio RossiBao YangBao YangBao YangFrontiers Media S.A.articlewater availabilityIADFxylogenesiscambial activityChinese pinecell enlargementPlant cultureSB1-1110ENFrontiers in Plant Science, Vol 12 (2021)
institution	DOAJ
collection	DOAJ
language	EN
topic	water availability IADF xylogenesis cambial activity Chinese pine cell enlargement Plant culture SB1-1110
spellingShingle	water availability IADF xylogenesis cambial activity Chinese pine cell enlargement Plant culture SB1-1110 Jiani Gao Jiani Gao Jiani Gao Sergio Rossi Sergio Rossi Bao Yang Bao Yang Bao Yang Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China
description	Intra-annual density fluctuation (IADF) is a structural modification of the tree ring in response to fluctuations in the weather. The expected changes in monsoon flow would lead to heterogeneous moisture conditions during the growing season and increase the occurrence of IADF in trees of the arid ecosystems of continental Asia. To reveal the timings and physiological mechanisms behind IADF formation, we monitored cambial activity and wood formation in Chinese pine (Pinus tabuliformis) during 2017–2019 at three sites in semi-arid China. We compared the dynamics of xylem formation under a drought event, testing the hypothesis that drought affects the process of cell enlargement and thus induces the production of IADF. Wood microcores collected weekly from April to October were used for anatomical analyses to estimate the timings of cambial activity, and the phases of enlargement, wall thickening, and lignification of the xylem. The first cells started enlargement from late April to early May. The last latewood cells completed differentiation in mid-September. Trees produced IADF in 2018. During that year, a drought in June limited cell production in the cambium, only 36% of the xylem cells being formed in IADF trees, compared to 68% in normal tree rings. IADF cells enlarged under drought in early July and started wall thickening during the rainfall events of late July. The drought restricted cell enlargement and affected wall thickening, resulting in narrow cells with wide walls. Cambium and cell enlargement recovered from the abundant rainfall, producing a new layer with large earlywood tracheids. IADF is a specific adaptation of trees to cope with water deficit events occurring during xylem formation. Our findings confirmed the hypothesis that the June-July drought induces latewood-like IADFs by limiting the process of cell enlargement in the xylem. Our finding suggests a higher occurrence of IADF in trees of arid and semi-arid climates of continental Asia if the changes to monsoon flows result in more frequent drought events during the earlywood formation in June.
format	article
author	Jiani Gao Jiani Gao Jiani Gao Sergio Rossi Sergio Rossi Bao Yang Bao Yang Bao Yang
author_facet	Jiani Gao Jiani Gao Jiani Gao Sergio Rossi Sergio Rossi Bao Yang Bao Yang Bao Yang
author_sort	Jiani Gao
title	Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China
title_short	Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China
title_full	Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China
title_fullStr	Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China
title_full_unstemmed	Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China
title_sort	origin of intra-annual density fluctuations in a semi-arid area of northwestern china
publisher	Frontiers Media S.A.
publishDate	2021
url	https://doaj.org/article/9e690e85c8c148fd96edb9d6d53422d4
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Origin of Intra-annual Density Fluctuations in a Semi-arid Area of Northwestern China

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