COVER SHIFT AND MORPHOLOGICAL PLASTICITY OF INVASIVE ALTERNANTHERA PHILOXEROIDES ALONG A RIPARIAN ZONE IN SOUTH CHINA

doi:10.17521/cjpe.2006.0106

Abstract

Abstract:

Background and Aims Biological invasions by non-native species have become a major environmental problem and a focus of ecological research. Relatively few studies have focused on invasibility and invasivness among microhabitats within communities. We compared the abundance and performance of non-native Alternanthera philoxeroides (alligator weed) and its co-occurring native congener, Alternanthera sessilis (sessile joyweed), in a wetland community along a riparian zone in southeast China to test the hypotheses that: 1) the degree of invasion differs between different types of microhabitats within the community; 2) microhabitat types that differ in invasion also differ in soil resource availability or in sediment characteristics likely to affect resource availability; and 3) phenotypic plasticity must have played a key role in adaptation to diverse habitats for A. philoxeroides because of its extremely low genetic diversity throughout China.

Methods Field surveys of natural distribution and performance of the two varieties on adjacent and contrasting microhabitat types (abandoned field, swamp, marsh dunes and gravel dunes) along a riparian zone were conducted in the autumn of 2003.

Key Results Soil organic matter, total N, available P and K were significantly higher and pH was lower in dryland and swamp than in dunes. Total vegetation coverage was significantly higher in dryland and swamp than in dunes. The relative coverage of A. philoxeroides was much higher than that of A. sessilis in more productive habitats (i.e. dry land and swamps), but this pattern reversed in less productive habitats (i.e. marsh and gravel dunes). A. philoxeroides showed greater morphological plasticity in response to habitat variation. Especially, the CV (coefficient of variation) of leaf area and branch angle in A. philoxeroides was 70 and 83 times greater than those in A. sessilis, respectively. Several morphological traits related to light foraging increased significantly from marsh and gravel dunes to more productive habitats (dry land and swamps). These traits included stem length, internode length, the number of nodes, and leaf length and width. Moreover, the leaf-bearing stems grew more vertically in dry land and swamps. Meanwhile, these traits in A. sessilis had no obvious variations among microhabitats.

Conclusions These results suggest that high plasticity in vertical growth and occupancy of soil microhabitat of rich nutrient resources may facilitate the invasions of A. philoxeroides.

Key words: Alternanthera philoxeroides, Alternanthera sessilis, Biological invasions, Light competition, Invasiveness, Resource ratios model

PAN Xiao-Yun, GENG Yu-Peng, ZHANG Wen-Ju, LI Bo, CHEN Jia-Kuan. COVER SHIFT AND MORPHOLOGICAL PLASTICITY OF INVASIVE ALTERNANTHERA PHILOXEROIDES ALONG A RIPARIAN ZONE IN SOUTH CHINA[J]. Chin J Plant Ecol, 2006, 30(5): 835-843.

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URL: https://www.plant-ecology.com/EN/10.17521/cjpe.2006.0106

https://www.plant-ecology.com/EN/Y2006/V30/I5/835

Figures/Tables 8

Fig.1 Location of the study area at the cross between Puyang River and Zhejiang-Jiangxi railway in Zhuji, Zhejiang Province, China

Table 1 Description of the four substrates and their vegetation characteristics

	河间砾石滩 Gravel dune	河边沙石滩 Marsh dune	废弃地 Dryland	沼泽 Swamp
海拔 Elevation (m)	37	34	39	30
坡度Slope (%)	3.1	1.7	<0.3	0
朝向Aspect	NW-SE	NW-SE	NW-SE	N-S
砾石含量Rocks and gravel content (%)	76	50	5	9
土壤含量Soil content (%)	3	30	81	76
有机质Organic matter (g·kg^-1)	0.83	2.53	16.54	24.10
总N Total N (g·kg^-1)	0.05	0.15	1.04	1.58
有效P Available P (mg·kg^-1)	0.31	0.89	12.72	17.49
有效K Available K (mg·kg^-1)	1.53	7.41	66.45	115.16
pH	7.9	7.6	7.3	7.1
植被盖度Vegetation cover (%)	13.7	27.6	94.4	98.1
优势种 Dominant plant species	莲子草 Alternanthera sessilis	莲子草 A. sessilis	喜旱莲子草 A. philoxeroides	喜旱莲子草 A. philoxeroides
次优势种 Sub-dominant species	喜旱莲子草 A. philoxeroides	喜旱莲子草 A. philoxeroides	莲子草 A. sessilis	凤眼莲 Eichhornia crassipes

Fig.2 Cover of Alternanthera philoxeroides (Black bar), A. sessile (White bar), and the other species (Grey bar) among the four microhabitats at the end of the growing season (Oct. 2003)

Fig.3 Canopy height and diameter of patchy distributed Alternanthera philoxeroides (P) and A. sessile (S) on gravel dune and marsh dune at the end of the growing season (Oct. 2003)

Fig.4 Plasticity in stem length, mean internode length, number of nodes, stem diameter, mean leaf area, and branch angle of leaf-bearing stems of Alternanthera philoxeroides (Grey)and A. sessilis (Black) across the four microhabitats at the end of the growing season (Nov. 2003)

Table 2 Coefficient of variation (CV) for several morphological parameters of Alternanthera philoxeroides and A. sessilis among different microhabitats

形态指标 Morphological parameters	喜旱莲子草(%) Alternanthera philoxeroides	莲子草(%) Alternanthera sessilis	相对值 Relative values
茎长 Stem length (cm)	97.7	10.8	9.1
节间长 Internode length (cm)	76.5	1.1	6.9
节数 Nodes number	21.8	11.2	2.0
茎直径 Stem diameter (mm)	44.1	2.7	16.7
叶面积 Leaf area (cm²)	94.0	1.4	69.8
分枝角度Branch angle (°)	24.9	0.3	83.0

Fig.5 Relationship between stem density (30 cm×30 cm quadrate-1) and mean canopy height (above ground on dryland and above water surface on swamp) in monotypic stand of Alternanthera philoxeroides on dryland and swamp substrate at the end of the 2003 growing season

Fig.6 Conceptual model of the shift in dominance of Alternanthera philoxeroides (P) and A. sessile (S) as a result of competitive outcomes between the two species for different limiting resources

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