Known as ‘weeds’ or ‘weeds’ are all those herbaceous plants that grow spontaneously and undesirably in fields, gardens, parks, and other areas where the vegetation is regulated by human beings.
Since the term is defined from a strictly anthropocentric point of view , depending on the type of human activity to which it refers, the same species can be weedy in one environment and desirable in another. For example, on a golf course, grasses that make up the lawn are desirable, but a spontaneously growing mint plant would be considered a weed. And on the contrary, in a mint crop for pharmacological use, lawn grasses would be weeds.
Due to their importance in agriculture and horticulture, weeds or weeds have been the object of study, especially aimed at discovering methods for their eradication. However, their ecological characteristics also make them excellent for the study of adaptation and evolution.
Weeds have a ruderal behavior, that is, they are capable of developing in habitats altered and disturbed by human activity. In addition to crop fields or parks and gardens, they also colonize roadsides and highways, burned areas, abandoned fields and even the streets and houses of uninhabited towns.
They tolerate high concentrations of nutrients in the soil, grow and reproduce rapidly. Its seeds are easily dispersed, can take root in cracks with a small volume of substrate, and are very resistant to adverse conditions. They can remain dormant in the soil for months or years, until the environment is right, and then germinate.
In relation to the advantages that they provide as an object of study, it is possible to document their history in a specific geographical area and to have evidence of their recent evolution under human influences that can be identified.
Confusion between an invasive weed and a weed is not uncommon. Many invasive species behave like weeds, and many of the weeds are indeed invasive. However, the differences between the two, although they may seem subtle, is not a trivial matter.
An invasive species, by definition, is an exotic species transported by the human hand to a new ecosystem, where it has been released, has survived, has formed reproductive populations, and has expanded colonizing new environments, different from those where it has been introduced.
Invasive plants have many traits of weeds and very often behave like weeds. But there are other invasive species that do not have that weedy behavior of colonizing land for human use, but prefer to colonize natural environments.
On the other hand, there are weeds that are neither invasive nor exotic. Native wild species that only try to recover the environment that has been taken from them by eliminating a natural ecosystem to turn it into a wheat field, a pasture area or a golf course.
The mere concept of ‘weed’ implies negative connotations that respond only to a very restricted socioeconomic aspect. It is true that weed plants have a certain impact on agriculture and are unpleasant in parks and gardens, and uncomfortable in recreational areas.
But those negative aspects do not at all justify his bad name or his fame. Weed plants, from an ecological point of view, are of great importance . Their presence and their dynamics have a positive impact on the functioning of ecosystems and the services they provide.
On the one hand, their high tolerance to soils highly managed by man makes them a key piece for the recovery of the natural environment in the process of ecological succession. In addition to acting as primocolonizing species of the disturbed environment, they also decontaminate it and optimize it for the later colonization of larger and longer-lasting species. Furthermore, weed communities are usually made up of multiple species that coexist and compete with each other, enriching the biodiversity of the environment.
Their rapid growth and reproduction, added to the fact that most of these plants form communities that are renewed year after year , makes them a good mechanism for capturing carbon that is later stored in the soil.
Referencias:
Baker, H. G. 1974. The Evolution of Weeds. Annual Review of Ecology and Systematics, 5(1), 1-24. DOI: 10.1146/annurev.es.05.110174.000245
Biondi, E. et al. 2012. Nitrophilous and ruderal species as indicators of climate change. Case study from the Italian Adriatic coast. Plant Biosystems – An International Journal Dealing with all Aspects of Plant Biology, 146(1), 134-142. DOI: 10.1080/11263504.2012.672342
Grime, J. P. 1974. Vegetation classification by reference to strategies. Nature, 250(5461), 26-31. DOI: 10.1038/250026a0
Guo, P. et al. 2018. Response of Ruderal Species Diversity to an Urban Environment: Implications for Conservation and Management. International Journal of Environmental Research and Public Health, 15(12), 2832. DOI: 10.3390/ijerph15122832
Sutherland, S. 2004. What makes a weed a weed: life history traits of native and exotic plants in the USA. Oecologia, 141(1), 24-39. DOI: 10.1007/s00442-004-1628-x
