Centaurea tchihatcheffii is a critically endangered annual endemic plant represented as a metapopulation on highly fragmented steppes of Ankara, Turkey. This study is about the conservation biology of the species via plant and seed demography studies during 2003-2008 for the following specific objectives, i) to determine its metapopulation status, ii) the effects of agricultural activities, iii) to construct annual plant population model and, finally iv) to perform population viability analysis (PVA) for the assessment of conservation strategies.
Through GIS based random-roadside surveys, it is revealed that species has a metapopulation status composed of 14 patchily distributed subpopulations on agricultural fields over 700 km2. Effects of herbicide use, tillage and stubble burn were simulated by the field experiments. Herbicide application caused extreme mortality and reduced germination success. Stubble burn had a detrimental effect only on seeds at the surface. Tillage before flowering leads to almost complete loss of that season’s seed production as it destroys aboveground populations but boots them up next year by accelerating seed bank dynamics.
For C. tchihatcheffii, a two-staged, annual plant population model is constructed, considering its seed bank dynamics, density-dependence and stochasticity. Relative risks of extinction and impacts of different management actions involving six scenarios were investigated using RAMAS Metapop through a population viability analysis (PVA).
Results/Conclusions
PVA predicts that the likelihood of extinction for the species is significant with conventional farming under the natural catastrophes. Most important finding of this study is about tillage practice as a form of disturbance which can be a friend or foe for the species. PVA highlights that timing and frequency of tillage is crucial; it can drift population to extinction when applied in spring, especially as it is mostly coupled with herbicide use in conventional farming, and can boost the population when applied in summer and provide soil disturbance without diminishing the above ground population. As the frequency of tillage practice through management action is increased the extinction risks decreases. Moreover the species may survive in nature for many years under herbicide free agriculture.
We propose tillage after seed set every other year as a conservation management option for a few big designated reserves to ensure long term survival of the species. As for the most applicable conservation strategy, delayed tillage every 4 years should be considered for the rest of the metapopulation. Alternatively, unprotected subpopulations elsewhere can benefit from nature-friendly farming.
