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Quantitative assessment of soil physical quality is of great importance for eco-environmental pollution and soil quality studies. in this paper, based on the S-theory, data from 16 collection sites in the haihe river Basin in northern China were used, and the effects of soil particle size distribution and bulk density on three important indices of the S-theory were investigated on a regional scale. the relationships between unsaturated hydraulic conductivity K i at the inflection point and S values (S/h i ) were also studied using two different types of fitting equations. The results showed that the polynomial equation was better than the linear equation for describing the relationships between -log K i and -log S, and -log K i and -log (S/h i ) 2 ; and clay content was the most important factor affecting the soil physical quality index (S). the variation in the S index according to soil clay content was able to be fitted using a double-linear-line approach, with decrease in the S index being much faster for clay content less than 20 %. in contrast, the bulk density index was found to be less important than clay content. the average S index was 0.077, indicating that soil physical quality in the haihe river Basin was good.Keywords: friability, hard-setting, S index, soil water retention curve.

Increased attention has been paid to effects of coal mining subsidence on the growth of plants. Studying the changes of plants photosynthetic physiology under the disturbance of coal mining subsidence is the basis for understanding dynamic exchanges of plant energy and water at that mining area. The 52302 working face of the Shendong mining area was selected as the experimental site, with Artemisia ordosica, Caragana korshinskii, and Populus spp. as the research targets. Changes in leaf photosynthesis were monitored in plants at a subsidence crack area. We showed collapse cracks decreased soil moisture and caused drought stress. The photosynthetic capacity of leaves was reduced. Compared with plants from the control area, stomatal conductance, photosynthetic CO2 assimilation, and transpiration rate were reduced in all three plant species. The activity of PSII reaction center and electron transport at the donor and acceptor sites significantly decreased.