Plastic responses of stem and leaf functional traits in Leymus chinensis to long-term grazing in a meadow steppe

doi:10.3724/SP.J.1258.2014.00040

Abstract

Abstract:

Aims Adaptation of plants to their habitats through phenotypic plasticity in which they trade off various kinds of functional traits is an important ecological strategy. Whereas plant functional traits and its effects on grassland ecosystem functioning have received much attention, the importance of grazing effects on functional traits is poorly understood. This study, therefore, aimed to analyze the responding model of Leymus chinensis functional traits to long-term grazing in semi-arid grassland.
Methods The study was conducted in a field experiment involving treatments with various grazing and enclosure schemes in Nei Mongol. We compared the effects of long-term enclosure, short-term enclosure (SE), moderate grazing (MG), and heavy grazing on plant functional traits in L. chinensis. Partial Least Squares Regression was used to analyze the contributions of controlling factors on changes in biomass in response to grazing.
Important findings The size of L. chinensis became smaller in plots subject to long-term grazing compared with in the plots of enclosures. It had a significant conservative property of plant dwarf which can be found in the SE plot. Interestingly, the variability increased significantly with the increasing of plasticity index of different functional traits. Also, some functional traits, such as aboveground biomass, plant height, mean leaf length etc., were sensitive traits to grazing. However, other indicators, such as leaf numbers, stem diameter, mean leaf width etc., which were inert functional traits. Stem length, plant height and other traits were main factors which cased the decreasing of L. chinensis aboveground biomass. On the whole, phenotypic change is an important adaptive strategy of L. chinensis to long term grazing.

Key words: functional trait, Leymus chinensis, meadow steppe, overgrazing, phenotypic plasticity, plant dwarf of grassland

LI Xi-Liang,HOU Xiang-Yang,WU Xin-Hong,null null,JI Lei,CHEN Hai-Jun,LIU Zhi-Ying,DING Yong. Plastic responses of stem and leaf functional traits in Leymus chinensis to long-term grazing in a meadow steppe[J]. Chin J Plant Ecol, 2014, 38(5): 440-451.

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URL: https://www.plant-ecology.com/EN/10.3724/SP.J.1258.2014.00040

https://www.plant-ecology.com/EN/Y2014/V38/I5/440

Figures/Tables 10

Fig. 1 Distribution map of the research site.

Fig. 2 Effects of enclosure and grazing to leaf phenotypic trait of Leymus chinensis (mean ± SE). LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, mean leaf width; LWE, leaf mass; TLA, total leaf area; TLW, total leaf mass. Plots see Fig. 1. Different small letters indicate significant differences (p < 0.05).

Fig. 3 Effects of enclosure and grazing to stem phenotypic trait of Leymus chinensis (mean ± SE). SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SW, stem mass. Plots see Fig. 1. Different small letters indicate significant differences (p < 0.05).

Fig. 4 Effects of enclosure and grazing to functional traits of Leymus chinensis (mean ± SE). AB, aboveground biomass; PH, plant height; SLW, stem mass/leaf mass. Plots see Fig. 1. Different small letters indicate significant differences (p < 0.05).

Fig. 5 Sorting of Leymus chinensis leaf and stem trait plasticity index (PI) change in short-term enclosure (SE), moderate grazing (MG) and heavy degree grazing (HG). AB, aboveground biomass; LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, leaf width; LWE, leaf mass; PH, plant height; SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SLW, stem mass/leaf mass; SW, stem mass; TLA, total leaf area; TLW, total leaf mass.

Fig. 6 Comparisons of variation in leaf and stem functional traits in Leymus chinensis. AB, aboveground biomass; LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, leaf width; LWE, leaf mass; PH, plant height; SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SLW, stem mass/leaf mass; SW, stem mass; TLA, total leaf area; TLW, total leaf mass.

Fig. 7 Relationships between variation of coefficient (CV) and plasticity index (PI) of functional traits in Leymus chinensis.

Table 1 The coordinated variation of Leymus chinensis leaf and stem phenotypic traits

	PH	LN	LL	LW	LLW	TLA	LA	SL	SD	SLD
PH	1.00
LN	0.20	1.00
LL	0.94^**	0.12	1.00
LW	0.70^**	0.11	0.75^**	1.00
LLW	0.84^**	0.08	0.88^**	0.37^**	1.00
TLA	0.92^**	0.32^*	0.94^**	0.81^**	0.75^**	1.00
LA	0.91^**	0.08	0.97^**	0.84^**	0.77^**	0.96^**	1.00
SL	0.98^**	0.24	0.92^**	0.68^**	0.81^**	0.91^**	0.89^**	1.00
SD	0.64^**	0.01	0.66^**	0.76^**	0.37^**	0.70^**	0.73^**	0.63^**	1.00
SLD	0.95^**	0.28^*	0.87^**	0.57^**	0.83^**	0.85^**	0.82^**	0.96^**	0.44^**	1.00

Fig. 8 Regression fitting of Leymus chinensis individual aboveground biomass and functional traits. AB, aboveground biomass; LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, leaf width; LWE, leaf mass; PH, plant height; SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SLW, stem mass/leaf mass; SW, stem mass; TLA, total leaf area; TLW, total leaf mass.

Fig. 9 The variable importance in projection values (VIP) (mean ± SE) (bar charts) and weights of influential factors (pie charts) of individual aboveground biomass by the biomass components (A) and functional traits (B). LA, leaf area; LL, leaf length; LLW, leaf length/width ratio; LMA, leaf mass per area; LN, leaf number; LW, leaf width; LWE, leaf mass; PH, plant height; SD, stem diameter; SL, stem length; SLD, stem length/stem diameter; SLW, stem mass/leaf mass; SW, stem mass; TLA, total leaf area; TLW, total leaf mass.

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