| As an important structure for material and ecological flows in coastal wetland ecosystems,the morphological characteristics of tidal creek have an important influence on soil water salinity and nutrient conditions,which in turn affect the spatial distribution of vegetation.Under the multiple effects of rivers,oceans and land,the Yellow River Delta region has a dense system of tidal creek,and the morphological characteristics of tidal creek are complex and variable with high spatial heterogeneity under the combined influence of natural factors and human activities.Under such background conditions,it is important to study the morphological characteristics,vegetation and soil physical and chemical properties of tidal creek in coastal wetlands.The spatial distribution characteristics of tidal creek morphology,vegetation and soil were analyzed by using the methods of UAV remote sensing,field survey and geostatistics,and the influence of tidal creek morphology on the spatial distribution of vegetation and soil was discussed.This study provides scientific support for the protection and restoration of coastal wetland ecosystems.The main research results are as follows:(1)In the three sub-regions of low tide flats,middle tide flats and high tide flats,the degree of tidal creek development varies.The densities of tidal creeks in the low,middle and high tide flatses were 4.57,8.40 and 5.10,respectively,with the middle tide flats > high tide flats > low tide flats.The curvature of the tidal creek was 1.11,1.26 and 1.09 for the low tide flats,middle tide flats and high tide flats respectively,middle tide flats > low tide flats > high tide flats.The tidal creek divergence rates were 14.20,27.54,and 11.17 for the low tide flats,middle tide flats,and high tide flats,respectively,with the middle tide flats > low tide flats > high tide flats.In general,the tidal creek development of the middle tide flats was the best.(2)The spatial distribution of vegetation cover and above-ground biomass of vegetation both showed a trend of gradual increase from sea to land.The spatial distribution of soil salinity,soil organic carbon and total soil nitrogen had obvious spatial heterogeneity.0～10 cm soil salinity showed a trend of gradually increasing from sea to land,10～20 cm soil salinity was generally low,and only two high values were found in the high tide flats.0～10 cm soil organic carbon showed the lowest value in the middle tide flats where tidal creeks were more developed;10～20 cm soil organic carbon gradually increased from the low tide flats to the high tide flats.The soil organic carbon content gradually increased from the low tide flats to the high tide flats.The spatial distribution pattern of total soil nitrogen content was patchy in both layers,and the high value areas were found in the low tide flats,middle tide flats and high tide flats.(3)The spatial distribution of vegetation and soil around the tidal creek of different grades differed to some extent.In the low tide flats,the vegetation cover near the first tide creek was significantly higher than that in the third tide creek(P < 0.05),and the above-ground biomass of vegetation near the first tide creek was significantly greater than that in the second and third tide creek(P < 0.05).In the 0～10 cm soil layer,there was no significant difference in soil salinity between different levels of tidal creek(P>0.05),in the 10～20 cm soil layer,the soil salinity in the secondary tidal creek of the middle tidal flats was significantly greater than that in the primary tidal creek(P<0.05),and there was no significant difference in soil salinity between the low tidal flats and the high tidal flats(P>0.05).In the 0～10 cm soil layer,the SOC of the third tidal creek was significantly greater than that of the first tidal creek in the low tidal flats(P < 0.05),the SOC of the second tidal creek was significantly greater than that of the third tidal creek in the middle tidal flats(P < 0.05),and the SOC of the second tidal creek was significantly greater than that of the first tidal creek in the high tidal flats(P < 0.05);in the 0～10 cm soil layer,the total soil nitrogen was not significantly different between the different tidal creek grades(P > 0.05).In the 0～10cm soil layer,there was no significant difference in the TN between different tidal creek(P>0.05);in the 10～20 cm soil layer,there was no significant difference in the TN between different tidal creek in the low tide flats(P > 0.05),the TN in the secondary tidal creek in the middle tide flats was significantly greater than that in the primary tidal creek(P<0.05),and the TN in the primary tidal creek in the high tide flats was significantly greater than that in the secondary tidal creek(P<0.05).(4)The spatial distribution of vegetation and soil changed as the lateral distance of the tidal creek increased.In the high tide flats,the vegetation cover gradually increased with the increase of tidal creek lateral distance;in the middle tide flats,the above-ground biomass of vegetation gradually decreased with the increase of tidal creek lateral distance;in the 0～10 cm soil layer,the soil salinity in the middle tide flats gradually increased with the increase of tidal creek lateral distance,but there was no significant correlation between the soil salinity and tidal creek lateral distance in the low tide flats and high tide flats(P>0.05).In the 10～20 cm soil layer,the soil salinity of the low tide flats decreased significantly with the increase of the lateral distance of the tidal creek,and the soil salinity of the middle tide flats and the high tide flats had a significant positive correlation with the lateral distance of the tidal creek(P < 0.05).In the 10～20 cm soil layer,with the increase of tidal creek lateral distance,the SOC of middle tide flats increased significantly(P < 0.05),while the SOC of low tide flats and high tide flats did not change significantly(P > 0.05).0～10 cm soil layer,with the increase of tidal creek lateral distance,the TN of middle tide flats increased significantly(P < 0.01),while the TN of low tide flats and high tide flats did not change significantly;10～20 cm soil layer,with the increase of tidal creek lateral distance,the TN of low tide flats and high tide flats increased significantly(P < 0.01).With the increase of the lateral distance of the tidal creek,the TN of the middle tide flats decreased significantly(P < 0.05),and the TN of the low tide flats and the high tide flats did not change significantly(P > 0.05). |
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