Effects of biocrusts on surface roughness and seed secondary dispersal of shrubs and grasses on the Loess Plateau, China

doi:10.17521/cjpe.2023.0072

Abstract

Abstract:

Aims In order to determine whether biocrusts enhance or impede the secondary dispersal of shrub and grass seeds and identify the key factors that influence seed dispersal, we simulated the process of seed secondary dispersal and measured relevant indicators such as the surface roughness of biocrusts.
Methods On the Loess Plateau, we established experimental plots on biocrusts (cyanobacteria- and moss- dominated crusts) and bare soils from aeolian sand and loess soil. For each selected plot, we utilized oblique photogrammetry to measure the surface roughness in both dry and wet conditions. All the treatments were studied in three replicates. Six species seeds of shrubs and grasses (Caragana korshinskii, Hedysarum scoparium, Artemisia ordosica, Setaria viridis, Xanthium sibiricum, and Bidens pilosa) with different morphological characteristics were selected for secondary dispersal experiments, and their seed displacement ratio (SDR), seed loss ratio (SLR), as well as seed displacement distance (SDD), were calculated following the experiments. The Spearman correlation analysis was then performed to identify the dominant factors.
Important findings (1) When compared with bare soils, the surface roughness of cyanobacteria- and moss-dominated crusts on aeolian sand soil increased by 6.69 and 6.13 times and by 2.52 and 1.45 times on loess soil, respectively. (2) Within contrast to wet conditions, the surface roughness of biocrusts increased by 26.56% on dry aeolian sand soil, whereas it reduced by 9.42% on dry loess soil. (3) The surface roughness of biocrusts of the aeolian sand soil rose by 16.84% under dry conditions and decreased by 16.38% under wet conditions compared with that on loess soil. (4) In comparison to bare soils, the SDR, SLR, and SDD of biocrusts dropped by 77.1%, 95.4%, and 72.2% on aeolian sand soil and by 76.5%, 93.8%, and 66.8% on loess soil, respectively. The characteristics of seed dispersal were not significantly affected by soil types or soil water conditions. (5) The SDR, SLR, and SDD were all significantly and negatively correlated with the surface roughness of biocrusts. However, only the SDR and SLR were significantly negatively linked to soil water content, and only the SLR and SDD were significantly negatively correlated with seed density. To summarize, biocrusts obstruct dispersal and enhance aggregation of seeds by increasing land surface roughness, thereby impacting the spatial structures and community dynamics of shrubs and grasses.

Key words: seed dispersal, vascular plant, surface roughness, cyanobacteria crust, moss crust, Loess Plateau

ZHANG Xue, HAN Feng-Peng, XIAO Bo, SHEN Si-Ming. Effects of biocrusts on surface roughness and seed secondary dispersal of shrubs and grasses on the Loess Plateau, China[J]. Chin J Plant Ecol, 2023, 47(12): 1668-1683.

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Figures/Tables 14

References 46

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测定指标 Measurement	风沙土 Aeolian sand soil			黄绵土 Loess soil
测定指标 Measurement	无结皮 Bare soil	藻结皮 Cyano crusts	藓结皮 Moss crusts	无结皮 Bare soil	藻结皮 Cyano crusts	藓结皮 Moss crusts
结皮盖度 Biocrust coverage (%)	-	77.33 ± 5.83	78.13 ± 4.55	-	66.08 ± 9.49	86.55 ± 1.78
结皮厚度 Biocrust thickness (mm)	-	8.79 ± 0.74	12.41 ± 0.96	-	11.09 ± 1.75	11.45 ± 1.49
密度 Density (g·cm^-3)	1.57 ± 0.05	1.59 ± 0.02	1.42 ± 0.01	1.44 ± 0.03	1.28 ± 0.01	1.28 ± 0.06
黏粒(<2 μm)含量 Clay (<2 μm) content (%)	1.64 ± 0.06	1.88 ± 0.03	4.47 ± 0.07	11.51 ± 0.53	14.24 ± 0.60	14.86 ± 1.22
粉粒(2-50 μm)含量 Silt (2-50 μm) content (%)	3.58 ± 0.42	9.37 ± 0.35	16.65 ± 0.28	4.15 ± 1.14	7.22 ± 0.62	3.55 ± 1.15
砂粒(50-2 000 μm)含量 Sand (50-2 000 μm) content (%)	94.89 ± 0.61	88.75 ± 0.38	78.88 ± 0.35	84.34 ± 1.76	78.54 ± 0.64	81.59 ± 1.08

测定指标 Measurement	风沙土 Aeolian sand soil			黄绵土 Loess soil
测定指标 Measurement	无结皮 Bare soil	藻结皮 Cyano crusts	藓结皮 Moss crusts	无结皮 Bare soil	藻结皮 Cyano crusts	藓结皮 Moss crusts
结皮盖度 Biocrust coverage (%)	-	77.33 ± 5.83	78.13 ± 4.55	-	66.08 ± 9.49	86.55 ± 1.78
结皮厚度 Biocrust thickness (mm)	-	8.79 ± 0.74	12.41 ± 0.96	-	11.09 ± 1.75	11.45 ± 1.49
密度 Density (g·cm^-3)	1.57 ± 0.05	1.59 ± 0.02	1.42 ± 0.01	1.44 ± 0.03	1.28 ± 0.01	1.28 ± 0.06
黏粒(<2 μm)含量 Clay (<2 μm) content (%)	1.64 ± 0.06	1.88 ± 0.03	4.47 ± 0.07	11.51 ± 0.53	14.24 ± 0.60	14.86 ± 1.22
粉粒(2-50 μm)含量 Silt (2-50 μm) content (%)	3.58 ± 0.42	9.37 ± 0.35	16.65 ± 0.28	4.15 ± 1.14	7.22 ± 0.62	3.55 ± 1.15
砂粒(50-2 000 μm)含量 Sand (50-2 000 μm) content (%)	94.89 ± 0.61	88.75 ± 0.38	78.88 ± 0.35	84.34 ± 1.76	78.54 ± 0.64	81.59 ± 1.08

物种 Species	质量 Mass (mg·seed^-1)	长 Length (mm)	宽 Width (mm)	高 Height (mm)	表面积 Area (mm²)	体积 Volume (mm³)	密度 Density (mg·mm^-3)	平面度 Flatness	附属物及黏液 Appendix or mucilage
柠条锦鸡儿 Caragana korshinskii	50.77 ± 13.87^b	6.20 ± 0.85^b	3.79 ± 0.38^b	3.01 ± 0.42^b	23.66 ± 4.68^b	71.80 ± 20.10^b	0.71 ± 0.08^a	1.69 ± 0.28^c	无 None
细枝岩黄耆 Hedysarum scoparium	20.51 ± 8.74^c	5.50 ± 0.54^b	3.88 ± 0.41^b	3.30 ± 0.48^b	21.43 ± 3.55^b	71.69 ± 20.01^b	0.28 ± 0.07^c	1.44 ± 0.18^d	表面有白色密毡毛 White dense hairs on surface
黑沙蒿 Artemisia ordosica	0.76 ± 0.11^d	2.16 ± 0.25^c	1.09 ± 0.13^d	0.77 ± 0.10^d	2.36 ± 0.17^d	1.81 ± 0.10^b	0.42 ± 0.05^b	2.12 ± 0.19^b	分泌黏液 Mucilage secretion
狗尾草 Setaria viridis	1.18 ± 0.17^d	2.50 ± 0.26^c	1.59 ± 0.17^c	1.21 ± 0.16^c	3.96 ± 0.20^d	4.78 ± 0.51^b	0.25 ± 0.05^cd	1.69 ± 0.09^c	无 None
苍耳 Xanthium sibiricum	127.93 ± 43.36^a	15.00 ± 1.71^a	7.13 ± 0.75^a	6.61 ± 0.69^a	108.21 ± 19.66^a	724.67 ± 192.76^a	0.19 ± 0.11^d	1.69 ± 0.15^c	具钩状硬刺 Hooked spine
鬼针草 Bidens pilosa	5.29 ± 0.38^cd	14.37 ± 2.37^a	0.96 ± 0.10^d	0.85 ± 0.09^d	13.73 ± 1.57^c	11.64 ± 1.78^b	0.45 ± 0.08^b	9.04 ± 0.59^a	顶端具倒刺 Barbed spine on head

物种 Species	质量 Mass (mg·seed^-1)	长 Length (mm)	宽 Width (mm)	高 Height (mm)	表面积 Area (mm²)	体积 Volume (mm³)	密度 Density (mg·mm^-3)	平面度 Flatness	附属物及黏液 Appendix or mucilage
柠条锦鸡儿 Caragana korshinskii	50.77 ± 13.87^b	6.20 ± 0.85^b	3.79 ± 0.38^b	3.01 ± 0.42^b	23.66 ± 4.68^b	71.80 ± 20.10^b	0.71 ± 0.08^a	1.69 ± 0.28^c	无 None
细枝岩黄耆 Hedysarum scoparium	20.51 ± 8.74^c	5.50 ± 0.54^b	3.88 ± 0.41^b	3.30 ± 0.48^b	21.43 ± 3.55^b	71.69 ± 20.01^b	0.28 ± 0.07^c	1.44 ± 0.18^d	表面有白色密毡毛 White dense hairs on surface
黑沙蒿 Artemisia ordosica	0.76 ± 0.11^d	2.16 ± 0.25^c	1.09 ± 0.13^d	0.77 ± 0.10^d	2.36 ± 0.17^d	1.81 ± 0.10^b	0.42 ± 0.05^b	2.12 ± 0.19^b	分泌黏液 Mucilage secretion
狗尾草 Setaria viridis	1.18 ± 0.17^d	2.50 ± 0.26^c	1.59 ± 0.17^c	1.21 ± 0.16^c	3.96 ± 0.20^d	4.78 ± 0.51^b	0.25 ± 0.05^cd	1.69 ± 0.09^c	无 None
苍耳 Xanthium sibiricum	127.93 ± 43.36^a	15.00 ± 1.71^a	7.13 ± 0.75^a	6.61 ± 0.69^a	108.21 ± 19.66^a	724.67 ± 192.76^a	0.19 ± 0.11^d	1.69 ± 0.15^c	具钩状硬刺 Hooked spine
鬼针草 Bidens pilosa	5.29 ± 0.38^cd	14.37 ± 2.37^a	0.96 ± 0.10^d	0.85 ± 0.09^d	13.73 ± 1.57^c	11.64 ± 1.78^b	0.45 ± 0.08^b	9.04 ± 0.59^a	顶端具倒刺 Barbed spine on head

因素 Factor	Type III 平方和 Type III sum of squares	df	均方 Mean square	F	p
土壤类型 Soil type (ST)	20.722	1	20.722	2.826	0.095
结皮类型 Biocrust type (BT)	3 172.827	2	1 586.414	216.336	<0.001
水分条件 Soil water condition (SWC)	2.783	1	2.783	0.380	0.539
ST × BT	132.760	2	66.380	9.052	<0.001
ST × SWC	70.176	1	70.176	9.570	0.002
BT × SWC	36.991	2	18.496	2.522	0.084
ST × BT × SWC	22.225	2	11.112	1.515	0.223