While vegetation is usually distributed individualistically along a gradient, the gradient approach is difficult to implement. Instead, categorizing sections (i.e., community associations) along a light spectrum (i.e., gradient) allows for ecological metrics (biomass, diversity) and mapping of landscape units. Community associations are the basis for any classification system, and for management and policy decisions, because the description of classification units provide information about the environment, diversity, and composition of the vegetation. Ecologists also agree these associations change over time due to a variety of internal and external forces. The challenge for any classification is to be able to track these changes. Here we show two case studies to examine the efficacy of current techniques to track changes and utilize change knowledge to maintain a useful classification. One follows community shifts from a resampling of historical plots, and asks ‘does shifting composition result in novel communities?’ The second uses remote sensing imagery to track spatio-temporal changes of natural vegetation due to plantation development, and asks ‘can we track community shifts in real time using remote sensing?’ If a new community is found, how do we incorporate that new concept into the classification system? We subsequently explore some of the possibilities.
Results/Conclusions
The two case studies evidence the need for classifications to be dynamic, capable of incorporating new novel communities, and normal ranges of variation for community concepts or units. Resampling of historical data clearly suggests species-specific responses, while at the same time few novel associations. The results suggest the ability to track many geographic shifts with a current classification. The remote sensing case study showed that we are able to distinguish between natural forest and plantation forest, dominated by the same tree species, using remote sensing techniques. Most of the diagnostic species of former floodplain forest communities vanished, and the herb layer of plantations is now formed by different species combinations, especially neophytes. Whether these plantations represent a new community, or will revert back to floodplain forest, is an open question. The United States National Vegetation Classification was established as a dynamic classification, with a protocol in place for the submission of proposed changes and implementation of those changes following peer review. The review system is set up to not only incorporate novel concepts but also improve the descriptions of existing concepts when more knowledge or data are collected.