Re: How/why does trampling affect plants ?

You are correct that grasses are well adapted to stand up to trampling because 
of their intercalary meristems. Trampling can cause a direct effect on plants 
by physically damaging the meristems as you indicate, and can also damage 
stems, leaves, flowers and fruits. However, trampling can also damage the soil 
in more long term ways. Soil compaction can reduce air and water availablity to 
the plants. A compacted soil surface can cause rain to run off rather than 
penetrate the soil, thereby causing drought. If the rain does not run off, it 
may pond on the surface and cause root aeration problems. 

Compaction also often increases the mechanical resistance to root growth, 
termed soil strength. Soil strength can be measured with a penetrometer, which 
uses pressure units. The soil bulk density is another method of expressing 
compaction. Some types of soils naturally tend to form a hard pan or 
impenetrable layer at a certain depth. Trampling may promote the formation of a 
hardpan. 

The soil compaction can have very dramatic and long lasting effects so they are 
often more important than the direct effect of trampling on plants. For 
example, soil compaction can also greatly reduce seed germination, which could 
have a long term, if not permanent, effect on species distribution.

High traffic turfgrass areas such as football fields and golf greens are often 
grown in a layer of pure sand rather than regular soil. The sand basically 
eliminates the possibility of soil compaction and greatly reduces problems of 
high traffic. However, even without soil compaction, turfgrass will eventually 
be killed if trampling or traffic is high enough.  

Soil compaction is a major concern in agricultural crops, and there are lots of 
websites discussing it. 
 
References


Response of five native plant communities to trampling in the Wind River Range, 
Wyoming, USA


Addressing soil strength problems on restoration projects 


Soil Strength


Soil strength and plant roots


Soil Hardpan


Soil Compaction And Drainage


Prescription Athletic Turf Construction Overview