Quaking Aspen (Populus tremuloides) reproduce via rhizomes, creating immense colonies that may include thousands of trees. One colony in Utah, nicknamed Pando, consists of a grove of ~47,000 trunks. Despite their massive size, scientists worry that these stands are vulnerable–why?

These strands are clones, however, due to their low genetic variability, the population becomes susceptible to diseases taking place in plants. Pando comprises grove of about 47000 trunks, these all are genetically similar that develops from a solitary underground species, Quaking aspen tree. Pando is an extremely large clone.  

However, for the past some years, scientists are worried about Pando's health. For the past thousands of years, Pando was living in fine tune with the native wildlife population, but for the past some years, a shift in balance is noticed. As in the absence of the development of novel stems, nothing will be able to substitute the natural withering of the older ones, if this goes on, the death of Pando will take place.  

estuaries are the partially enclosed coastal bodies of brackish water formed at the mouth of sea where river meets an ocean. it is a transition zone between river and sea water so estuaries are influenced to both marine environment such as tides, waves and to riverine such as flow of fresh water and sediments. the mixing of sea and fresh water provide high level of nutrients, making estuaries a high product habitats.

many estuaries suffers degradation from a variety of human activities like erosion from deforestation, overgrazing, overfishing, drainage and eutrophication.

so from the above statement answers will be

1. false as estuaries are formed due to both brackish and freshwater.

2.true, due to high productivity estuaries are breeding ground for many marine species.

3. direct and indirect activities of man that contribute to pollution and deposition of sediments.