Analysis of the contributions of human factors and natural factors affecting the vegetation pattern in coastal wetlands

Figures & data

Figure 1. Location (a) and functional zones (b) of the study area

Table 1. Criteria for evaluating the interference intensity of human activities in different cover type

Human disturbance index (HDI)		Score by expert
Value	Level	Scoring criteria	Typical land cover type
≥ 0.8	Very high	Frequent human activity throughout the year (constructed wetland)	Aquaculture ponds, salt pans, and rice fields assignment 5
≥ 0.6	High	Frequent human activity during some seasons (semi-constructed wetland)	Rivers, and Phragmites australis marshes assignment 4
≥ 0.4	Medium	Vegetation cover type dominated by annual herbaceous plants	Suaeda glauca marshes, Aeluropus littoralis marshes, assignment 3
≥ 0.2	Low	Vegetation cover type dominated by perennial herbaceous plants	Spartina alterniflora marshes assignment 2
< 0.2	Very low	Lacking vegetation cover and not fully utilized	Bare mud flats and coastal waters assignment 1

Notes: In this study, construction land is regarded as a land cover type with the strongest effects of human activities (Assignment>5, Value = 1). Therefore, the construction land equivalent is designated as the basic unit to unify the measure of the effects on the land surface.

Figure 2. Spatial distribution characteristics of soil moisture and salinity for different sampling sites (from A to T) in the different functional zones (southern experimental zone, SEZ; northern experimental zone, NEZ; southern buffer zone, SBZ; and northern buffer zone, NBZ) in the different plant communities (Phragmites australis, P. australis; Suaeda glauca, S. glauca; Spartina alterniflora, S. alterniflora; and bare mudflat, Bf)

Figure 3. Canonical correspondence analysis ordination diagram for different plant communities (Phragmites australis, P. a; Suaeda glauca, S. g; Spartina alterniflora, S. a; and bare mudflat, Bf) and soil moisture and salinity in typical sections in the different functional zones (a: northern experimental zone, NEZ; b: northern buffer zone, NBZ; c: southern experimental zone, SEZ; d: southern buffer zone, SBZ)

Figure 4. The spatial heterogeneity of soil moisture (a) and salinity (b) in the study area

Table 2. Spatial variation functions and relevant parameters of soil moisture and salinity under different human disturbance index (HDI) backgrounds in the subarea

Subarea (HDI)	Indicator	Nugget (Co)	Sill (Co+C)	Range	Co/(Co+C)	Goodness of fit
NEZ (0.558/Medium)	Moisture	0.002	0.021	12.45	9.52%	92.45%
	Salinity	0.000	0.215	5.21	0.00%	86.89%
NBZ (0.526/Medium)	Moisture	0.000	0.016	12.62	0.00%	85.21%
	Salinity	0.015	0.201	8.27	7.46%	94.33%
SBZ (0.612/High)	Moisture	0.010	0.013	3.29	76.92%	90.56%
	Salinity	0.023	0.029	11.22	79.31%	88.72%
SEZ (0.657/High)	Moisture	0.018	0.023	8.66	78.26%	92.26%
	Salinity	0.009	0.011	6.33	81.82%	95.36%

Nugget (Co) reflects the variability and measurement error of the variable on the minimum sampling scale; sill (Co+c) is the semivariance corresponding to when the model increases to a relatively stable value for the step size and reflects the overall characteristics of the regionalized variable; range is the step at which the variation function reaches the sill for a limited step size and reflects the maximum distance of spatial autocorrelation.