Leaf Longevity in a Timberline Tree Species Juniperus saltuaria in the Sergymla Mountains, Southeastern Tibet

doi:10.5814/j.issn.1674-764x.2022.01.004

Abstract

Abstract:

Leaf longevity is an important adaptive strategy that allows plants to maximize photosynthetic carbon gain. Due to the difficulty of identifying overwintering bud scars and distinguishing the age sequence of twigs, leaf longevity is rarely studied in Cupressaceae species, which further limits our understanding of the leaf economic spectrum (LES) for these populations. Here, we investigated the leaf longevity, as well as mass-based leaf nitrogen concentration (N_mass), of Juniperus saltuaria at different canopy heights for both subalpine and alpine timberline forests in the Sergymla Mountains, southeastern Tibet. We found that the mean leaf longevity was 4.2±1.2 years, and overall it did not differ significantly between different elevations. Along the vertical profiles of juniper canopies, the leaf longevity did not reflect a linear trend. With increasing leaf longevity, N_mass showed declining trends. We further analyzed the relationship between leaf longevity and the corresponding length of green twigs, and found that the length of green twigs could only explain 1%-3% of the variation in leaf longevity, indicating that the length of green twigs is a poor predictor for the variation in leaf longevity. In summary, for the J. saltuaria species in timberline or nearby subalpine forests, the effects of elevation and canopy depths on leaf longevity are minor, and the leaf trait analysis is in accordance with the prediction of LES.

Key words: canopy height, elevation, leaf nitrogen concentration, length of green twigs, Cupressaceae

ZHANG Lin, YANG Liu, GUO Ying, SHEN Wei, CUI Guangshuai. Leaf Longevity in a Timberline Tree Species Juniperus saltuaria in the Sergymla Mountains, Southeastern Tibet[J]. Journal of Resources and Ecology, 2022, 13(1): 34-40.

Figures/Tables 7

Fig. 1 (a) A map of the study area and sampling plot; (b-d) The physiognomy and an individual of Juniperus saltuaria in the Sergymla Mountains.

Table 1 Stand characteristics for Juniperus saltuaria forests at the two elevations

Forest type	Elevation (m)	Stand age (yr)	Mean tree height (m)	Mean DBH (cm)	Basal area (m² ha^-1)	Tree density (trees ha^-1)
Timberline forest	4425	300-400	6.0	13.3	39.8	2050
Subalpine forest	4290	400-500	9.5	26.8	60.7	708

Fig. 2 Normal distribution in leaf longevity for Juniperus saltuaria at different elevations in the Sergymla Mountains

Fig. 3 Variations in leaf longevity among canopy depths for Juniperus saltuaria at different elevations in the Sergymla Mountains Note: Different upper-case letters indicate significant differences among different canopy depths, while different lower-case letters indicate significant differences between different elevations.

Fig. 4 Relationship between leaf longevity and mass-based leaf nitrogen content (Nmass) for Juniperus saltuaria at different elevations in the Sergymla Mountains

Fig. 5 Variations in leaf longevity with length of green shoots for Juniperus saltuaria at different elevations in the Sergymla Mountains

Table 2 Comparisons in leaf longevity for some of Cupressaceae species

No.	Species	Location	Leaf longevity (range)(yr)	Reference
1	Juniperus saltuaria	Linzhi, Tibet, China	4.2 (1-8)	This study
2	Juniperus scopulorum	Coastal Washington State, USA	2.5 (1-4)	Pease (1917)
3	Juniperus thurifera	France/Spain	2.46 (2.0-3.2)	Montesinos et al. (2010)
4	Juniperus monosperma	New Mexico, USA	6.5	Wright et al. (2004)
5	Chamaecyparis obtusa	Karakawa, Japan	3.9 (2.7-5.9)	Miyamoto et al. (2013)
6	Chamaecyparis obtusa	Okuono, Japan	6.3 (4.6-7.8)	Miyamoto et al. (2013)
7	Thuja plicata	Coastal Washington State, USA	3.5 (1-7)	Pease (1917)
8	Thuja plicata	Northern Idaho, USA	8.9 (6.8-10.6)	Harlow et al. (2005)
9	Thuja occidentalis	Wisconsin, USA	4	Wright et al. (2004)
Mean			4.7

References 26

[1]	Boonman A, Pons T L. 2007. Canopy light gradient perception by cytokinin. Plant Signaling & Behavior, 2(6): 489-491.
[2]	Ellsworth D S, Reich P B. 1993. Canopy structure and vertical patterns of photosynthesis and related leaf traits in a deciduous forest. Oecologia, 96(2): 169-178. DOI PMID
[3]	Field C. 1983. Allocating leaf nitrogen for the maximization of carbon gain: Leaf age as a control on the allocation program. Oecologia, 56(2-3): 341-347. DOI PMID
[4]	Field C, Mooney H A. 1986. The photosynthesis-nitrogen relationship in wild plants. In: Givnish T J (ed.). On the economy of plant form and function. Cambridge, UK: Cambridge University Press.
[5]	Gower S T, Reich P B, Son Y. 1993. Canopy dynamics and aboveground production of five tree species with different leaf longevities. Tree Physiology, 12(4): 327-345. PMID
[6]	Harlow B A, Duursma R A, Marshall J D. 2005. Leaf longevity of western red cedar (Thuja plicata) increases with depth in the canopy. Tree Physiology, 25(5): 557-562. DOI URL
[7]	He J S, Wang Z H, Wang X P, et al. 2006. A test of the generality of leaf trait relationships on the Tibetan Plateau. New Phytologist, 170(4): 835-848.
[8]	Kikuzawa K. 1995. Leaf phenology as an optimal strategy for carbon gain in plants. Canadian Journal of Botany, 73(2): 158-163. DOI URL
[9]	Liu X S, Luo T X. 2011. Spatiotemporal variability of soil temperature and moisture across two contrasting timberline ecotones in the Sergymla Mountains, southeast Tibet. Arctic Antarctic and Alpine Research, 43(2): 229-238. DOI URL
[10]	Liu X S, Nie Y, Luo T X, et al. 2016. Seasonal shift in climatic limiting factors on tree transpiration: Evidence from sap flow observations at alpine treelines in Southeast Tibet. Frontiers in Plant Science, 7: 1018. DOI: 10.3389/fpls.2016.01018. DOI
[11]	Lu X M, Liang E Y, Wang Y F, et al. 2019. Past the climate optimum: Recruitment is declining at the world’s highest juniper shrublines on the Tibetan Plateau. Ecology, 100(2): e02557. DOI: 10.1002/ecy.2557. DOI URL
[12]	Luo T X, Luo J, Pan Y D. 2005. Leaf traits and associated ecosystem characteristics across subtropical and timberline forests in the Gongga Mountains, eastern Tibetan Plateau. Oecologia, 142(2): 261-273. DOI URL
[13]	Miehe G, Miehe S, Vogel J, et al. 2007. Highest treeline in the Northern Hemisphere found in southern Tibet. Mountain Research and Development, 27(2): 169-173. DOI URL
[14]	Miyamoto K, Okuda S, Inagaki Y, et al. 2013. Within- and between-site variations in leaf longevity in hinoki cypress (Chamaecyparis obtusa) plantations in southwestern Japan. Journal of Forest Research, 18(3): 256-269. DOI URL
[15]	Montesinos D, García-Fayos P, Verdú M. 2010. Relictual distribution reaches the top: Elevation constrains fertility and leaf longevity in Juniperus thurifera. Acta Oecologica, 36(1): 120-125. DOI URL
[16]	Pease V A. 1917. Duration of leaves in evergreens. American Journal of Botany, 4(3): 145-160. DOI URL
[17]	Pérez-Harguindeguy N, Díaz S, Garnier E, et al. 2013. New handbook for standardised measurement of plant functional traits worldwide. Australian Journal of Botany, 61: 167-234. DOI URL
[18]	Reich P B, Walters M B, Ellsworth D S. 1997. From tropics to tundra: Global convergence in plant functioning. Proceedings of the National Academy of Sciences of the USA, 94(25): 13730-13734. DOI URL
[19]	Seiwa K. 1999. Changes in leaf phenology are dependent on tree height in Acer mono, a deciduous broad-leaved tree. Annals of Botany, 83(4): 355-361. DOI URL
[20]	Smith L, Primack R B, Zipf L, et al. 2019. Leaf longevity in temperate evergreen species is related to phylogeny and leaf size. Oecologia, 191(3): 483-491. DOI URL
[21]	Tworkoski T, Miller S, Scorza R. 2006. Relationship of pruning and growth morphology with hormone ratios in shoots of pillar and standard peach trees. Journal of Plant Growth Regulation, 25(2): 145-155. DOI URL
[22]	Wang X H, Zhang J, Zhang Z X. 2000. Leaf longevity of evergreen broad-leaved species of Tiantong National Forest Park, Zhejiang Province. Acta Phytoecologica Sinica, 24(5): 625-629. (in Chinese)
[23]	Wright I J, Reich P B, Westoby M, et al. 2004. The worldwide leaf economics spectrum. Nature, 428(6985): 821-827. DOI URL
[24]	Yu H Y, Chen Y T, Xu Z Z, et al. 2014. Analysis of relationships among leaf functional traits and economics spectrum of plant species in the desert steppe of Nei Mongol. Chinese Journal of Plant Ecology, 38(10): 1029-1040. (in Chinese) DOI URL
[25]	Zhan F, Yang D M. 2012. Relationships among light conditions, crown structure and branch longevity: A case study in Osmanthus fragrans and Metasequoia glyptostroboides. Acta Ecologica Sinica, 32(3): 984-992. (in Chinese) DOI URL
[26]	Zhang L, Luo T X, Zhu H Z, et al. 2010. Leaf life span as a simple predictor of evergreen forest zonation in China. Journal of Biogeography, 37(1): 27-36. DOI URL