Garnier, E., J. Cortez, G. Billès, M.L. Navas, C. Roumet, M. Debussche, G. Laurent, A. Blanchard, D. Aubry, A. Bellmann, C. Neill, J.P. Toussaint. 2004. Plant Functional Markers Capture Ecosystem Properties During Secondary Succession. Ecology 85(9). 2630-2637.
In this article, the researchers attempted to test the biomass ratio hypothesis in an abandoned vineyard using three traits, specific lead area, leaf dry matter content, and leaf nitrogen concentration. The researchers noted that a major effect which humans are having on Earth’s ecosystems involves changing land use, in this case, an agricultural use for growing grapes for wine making. Once these properties are abandoned, problems arise in terms of restoration, since the soils may have been changed in a way which may cause difficulties with restoration and succession. Traditionally, succession starts with colonial species colonizing a property which has been disturbed. The colonizing species are replaced with mid-successional species, followed by mid-climax, and finally, climax species. From here, the climax species are removed by disturbance, and the process starts over again. In the case of this vineyard, the disturbance was the removal of the previous ecosystem to make room for the components required for a vineyard. This changes the dynamic of the succession process, which could change the biomass ratio.
The study site was an abandoned vineyard in southern France in the subhumid Mediterranean climate with a soil rich in calcium and an alkaline pH. The vineyard was removed between 1962-2002. They calculated the biomass ratio at various parts of the property to account for the time range of removal. Samples were recorded in areas where herbaceous vegetation and small woody plants were found. Net primary production was calculated between May and February (growing season). Leaf characteristics were measured during the peak of the growing season (April-May). An elemental analyzer was used for these measurements. In total, 27 species were used and 54 data points were collected.
Results and Conclusions
Biomass was lowest in the first years following abandonment, which they found started to increase after seven years, but net primary productivity decreased with field age. During this time, soil carbon and nitrogen concentrations increased threefold. The explanation given is that the early, colonial species are fast growing yet small in terms of biomass. After a growing season, they died off. They were followed up by similar species. After multiple growing seasons, the dead mass from these species littered the ground, causing an increase in soil carbon and nitrogen concentrations. After enough time, seven years in this case, later successional species colonized the study site. Later successional grow much slower yet are longer lived. This would lead to a decrease in net primary production but an increase in biomass, as the species live longer. These findings are consistent with the biomass ratio hypothesis from Odum 1969. The findings from this paper resulted in the researchers suggesting that the measured characteristics being labeled as “functional markers,” as they described them as being power quantitative tools which allowed for the prediction of plant succession patterns.