Time of germination and establishment success after fire of three obligate seeders in a Mediterranean shrubland of central Spain

Abstract

Aim Determining how differences in time of germination can affect plant establishment in plant communities that, after a disturbance, must reestablish from seeds under climatic conditions subject to extremes, such as the Mediterranean. Although early germination may be beneficial for survival in summer, when drought is severe, this may expose the seedlings to winter extremes, thus to higher mortality. Understanding how sensitive is the establishment of different species to temporal patterns of germination will help to understand the factors that control species distribution and community stability in disturbance-prone environments, as well as its sensitivity to changes in weather patterns as climate changes.Methods An experimental fire was made in early fall in an old Cistus-Erica shrubland in Toledo (central Spain). After fire, germination, survival and growth of the three dominant seeder species (Cistus ladanifer, Erica umbellata and Rosmarinus officinalis) were monitored during the first 3 years after fire. Seedlings were tagged to identify their time of emergence, and divided into cohorts according to their month of germination. Differences in survival of the various cohorts were evaluated by means of a Wilcoxon (Gehan) statistic. Height of surviving, tagged plants was compared among cohorts by means of a KolmogorovSmirnov test.Results The year following fire was one of the driest on record, while the next one was one of the wettest. Germination was more abundant during the first than during the second year. Establishment was mainly from first-year germination, as the majority of second-year germinated seedlings died. Temporal patterns of germination within a year and between years varied between species. Seedling mortality was highest immediately following germination, not in summer. Mortality was related to time of germination: during a given period of time, the mortality of younger seedlings was higher than that of older ones. However, survival was not highest for the first cohorts. In general, the earlier the seedlings germinated the more vigourous they became, more clearly so for Cistus than for Rosmarinus, but differences tended to disappear with time. Overall, time of germination varied between species and affected differently seedling survival and vigour of the various species. Rosmarinus and Cistus had sufficient survivors to reestablish the initial population. Erica, despite abundant germination, suffered a strong population reduction.Main conclusions Mediterranean shrub species differ in their temporal patterns of germination and survival after fire. The effect of time of germination is complex: germinating early is advantageous since old seedlings fared better than younger ones when confronted with the same rigours. However, germinating early might expose the seedlings to greater hazards and the first cohort might not survive best.

Impacts of Land Management on the Resilience of Mediterranean Dry Forests to Fire

“…In a post-fire situation, competing plants include grasses and resprouting species that take less time to regrow than seedlings [20]. Intra-specific competition may also occur several years after the fire in case of massive post-fire recruitment but these situations only affect the individual and not the population level.…”

“…It is difficult to obtain quantitative information about this window for individual Mediterranean plant species, but Quintana et al (2004) suggest, based on empirical measurements, that this optimal window might be pinpointed as the next wet season (i.e., first autumn, winter, and spring) after the fire, and extend to no more than the next two years [20].…”

A klímaváltozás emberi jogi aspektusai

“…Encroachment by grasses (Werkman and Callaghan, 2002) and elevated nitrogen leaching Gorissen et al, 2004;Schmidt et al, 2004) are also likely. In southern Europe, warming and, particularly, increased drought, are likely to lead to reduced plant growth and primary productivity (Ogaya et al, 2003;Llorens et al, 2004), reduced nutrient turnover and nutrient availability Peñuelas 2004, 2005), altered plant recruitment (Lloret et al, 2004;Quintana et al, 2004), changed phenology (Llorens and Peñuelas, 2005), and changed species interactions (Maestre and Cortina, 2004;Lloret et al, 2005). Shrubland fires are likely to increase due to their higher propensity to burn (Vázquez and Moreno, 2001;Mouillot et al, 2005;Nunes et al, 2005;Salvador et al, 2005).…”

Composición vegetal de la estación biológica de la UCM ‘Finca de Ontalba’

“…Environmental managements such as fire, grazing, agriculture and plantations modify natural vegetation and landscape (Mooney et al 1980, Trabaud 1980, Adler et al 2001, Quintana et al 2004). The Mediterranean region has been under human influence for thousands of years.…”