It is impossible to find out whether the size of a plant population would increase in the future or decrease without proper study of the plant population ecology. It would also tell us that what are the plant species that show growth and what might be the reasons that stop the plants from growing. When this becomes clear, it would be very easy to overcome those reasons and get a better plant population. It would be also known that which two species can survive together and which two species cannot survive together.
Factors affecting plant population
There are many reasons that affect plant population ranging from biotic to abiotic ones. The community assembly might be affected by the biotic interactions between the plants. There might also be plant species that invade some other plant species. This would also become clear after a proper study of the plant population ecosystem has been done. Adaption might be another factor which affects the growth of a plant. While some plants are able to adapt to a particular kind of soil or environmental conditions, some might not be able to.
Know how to interconnect the results
It might become hectic to study all the plant species in the universe. Hence study might be reduced to a considerable level by applying a little extra effort in the beginning itself. For example, there are some traits of the plant species which are found in more than one species. If it is approved that a plant with some particular trait would not be able to survive in a particular environment, it might be assumed that all the plants having that particular trait would not be able to survive there. The species are also interconnected; it is not that every individual plant species would behave the same always.
Relation between genome size and abundance
The growth of the plants might also be related to the genome size. Earlier it was believed that there is no interconnection between them but recently in a study of the plant population it was revealed that there is a direct link between both. No matter how much the plant species are modified, if there is a particular trait present in it then there would always be a connection between the plant species and the genome size. The size of seed, height of plant and the ratio of leaves on stems might be some criteria to measure genome size.
Since there is too much competition these days, newer research results come out frequently. Recently, it has been reported that the species of plants that are closely related to each other must be planted closely if you want them to grow together. They would also provide you a good ecosystem and it would be easier to study the plant population ecology of such an ecosystem.