When looking at an ecosystem and the communities held within, most people inevitably look first at the biological aspects because it is a very obvious part of the landscape. Plants, animals; they are all part of what a person sees when they look at the ecosystem. These integral parts of the landscape are what characterize a community, the human way of placing order in a very complex system.
However, communities do not necessarily exist, with everything depending on each other for their presence in that environment. For the term 'community' to be true, everything found in one arrangement in one place with the same factors, will inevitably have to be repeated. Communities are repeated entities that are found in similar organizations in other areas. But this is generally not the case. Dominant species such as trees and predators can be used to classify a community, or a particular structure can. But in most cases, everything is not dependent on every other organism in the area.
For example, most plants can grow perfectly well when taken out of their original community and placed in another location with none of the factors the same. If a community does exist, and species are dependent on one another for survival, this would not be the case. Various studies have shown that many plant species do not need to be around a certain set of other species to survive.
So for a plant to survive, what does it need if not interactions with other plants?
Plants basically respond first and foremost to the abiotic factors of their environment. Where the factors are ideal in one place, they will grow there, regardless of what other biota are there. Soils, hydrology, and nutrients are a major factor in where a plant grows. These organisms cannot just grow anywhere. For when a seed floats down from the air after it is released, it does not compete with other plants. It does not form a mutualistic relationship with a fungi. The one thing the seed is looking for is the ideal conditions in the soil, with the hydrology, and the nutrients available. Only after this first fact will its survival be concerned about the other impacts like competition with other organisms, symbiotic relationships with other plants, and even predation.
So, although communities exist in our sight from afar - things such as rain forests, savannas, woodlands, and alpine herb-fields - they do not necessarily occur according to the arrangement of individual plants.