Two species of buttercup are found in a field in North Dakota, and they tend to flower at approximately the same time in early spring. When some ecology students decided to conduct an experiment in community dynamics, they selectively removed one species from the field by hand-picking all emergent plants. The remaining species showed a significant increase in its population size during the next season. This study demonstrated

these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.  

answer;

c. a tree whose roots are surrounded by wet sand.

explanation;

water stress is an important factor limiting the growth and productivity of forests.water stress is the most often cited cause of poor survival and growth of woody landscape plants.

-insufficient soil moisture is the most common form of water stress, but excess moisture that leads to poor soil aeration (hypoxia) can also result in reduced plant vitality. a tree whose roots are surrounded by wet sand would be least likely to experience water stress.