TY - JOUR
T1 - Which are the factors controlling tree seedling establishment in North Italian floodplain forests invaded by non-native tree species?
AU - Terwei, André
AU - Zerbe, Stefan
AU - Zeileis, Achim
AU - Annighöfer, Peter
AU - Kawaletz, Heike
AU - Mölder, Inga
AU - Ammer, Christian
N1 - Funding Information:
We would like to thank the Marianne and Dr. Fritz Walter Fischer Foundation within the Stifterverband für die Deutsche Wissenschaft and the Foundation of the Free University Bozen-Bolzano for funding our research and the Ateneo Italo-Tedesco for providing the VIGONI program for supporting project-based exchange of staff. We also thank Thomas Wilhalm and Francesco Sartori for help and support with the determination of the plant species, Fulvio Caronni and the park administration for useful information about the biosphere reserve and providing free accommodation during field work, Armin Schmitt for help with statistical questions, and Anna Radtke for valuable comments on former versions of the manuscript. Finally, we are very grateful for many constructive comments and suggestions of two anonymous reviewers.
PY - 2013/9/15
Y1 - 2013/9/15
N2 - In hardwood floodplain forests of the North Italian Po Plain the non-native and light-demanding tree species Prunus serotina Ehrh. and Robinia pseudoacacia L. coexist with the native tree species Carpinus betulus L., Quercus robur L., and Ulmus minor Mill. In order to identify the factors controlling the establishment of seedlings of these species, we focused on the scale of micro-plots, which provide safe sites for tree species regeneration. We used seedling and sapling counts as the response variable. For modelling the seedling regeneration in relation to a multivariate set of 15 measured soil and stand characteristics, a hurdle negative binomial model was applied and then compared with a non-metric multidimensional scaling ordination, visualising the relationships between the regenerating species and the environmental parameters. In general, it could be shown that there are species-specific differences in the requirements for seedling regeneration between the five target species, and that the most important parameters affecting seedling establishment were the availability of potential seed sources, soil humidity, and light availability. Q. robur and C. betulus showed a wide ecological range regarding soil humidity, whereas U. minor was restricted to moister soils, and the two non-native species only occurred on dry soils. In addition, R. pseudoacacia and Q. robur regenerated very scarcely under the closed canopy inside the stands and were highly dependent on large scale disturbance events. After a disturbance, the presence of R. pseudoacacia in the canopy promoted the seedling regeneration of Q. robur. P. serotina was found to regenerate frequently in the closed forest and to persist for a long time under shade, but also needs forest gaps to establish in the canopy. We believe that P. serotina was wrongly classified as a shade-intolerant species in the past. We suggest that it is a competitive invader in a broad range of resource availability. In conclusion, with regard to the further forest development, it could be assumed that the absence of disturbance events resulting in large openings leads to a reduction in the number of P. serotina, R. pseudoacacia, and Q. robur individuals during succession. Nevertheless, disturbances on wetter soils, e.g. related to the natural river dynamics, will clearly favour the seedling regeneration of Q. robur compared to the non-native species, which are generally limited to the drier sites of the floodplain forests.
AB - In hardwood floodplain forests of the North Italian Po Plain the non-native and light-demanding tree species Prunus serotina Ehrh. and Robinia pseudoacacia L. coexist with the native tree species Carpinus betulus L., Quercus robur L., and Ulmus minor Mill. In order to identify the factors controlling the establishment of seedlings of these species, we focused on the scale of micro-plots, which provide safe sites for tree species regeneration. We used seedling and sapling counts as the response variable. For modelling the seedling regeneration in relation to a multivariate set of 15 measured soil and stand characteristics, a hurdle negative binomial model was applied and then compared with a non-metric multidimensional scaling ordination, visualising the relationships between the regenerating species and the environmental parameters. In general, it could be shown that there are species-specific differences in the requirements for seedling regeneration between the five target species, and that the most important parameters affecting seedling establishment were the availability of potential seed sources, soil humidity, and light availability. Q. robur and C. betulus showed a wide ecological range regarding soil humidity, whereas U. minor was restricted to moister soils, and the two non-native species only occurred on dry soils. In addition, R. pseudoacacia and Q. robur regenerated very scarcely under the closed canopy inside the stands and were highly dependent on large scale disturbance events. After a disturbance, the presence of R. pseudoacacia in the canopy promoted the seedling regeneration of Q. robur. P. serotina was found to regenerate frequently in the closed forest and to persist for a long time under shade, but also needs forest gaps to establish in the canopy. We believe that P. serotina was wrongly classified as a shade-intolerant species in the past. We suggest that it is a competitive invader in a broad range of resource availability. In conclusion, with regard to the further forest development, it could be assumed that the absence of disturbance events resulting in large openings leads to a reduction in the number of P. serotina, R. pseudoacacia, and Q. robur individuals during succession. Nevertheless, disturbances on wetter soils, e.g. related to the natural river dynamics, will clearly favour the seedling regeneration of Q. robur compared to the non-native species, which are generally limited to the drier sites of the floodplain forests.
KW - Hurdle negative binomial model
KW - Natural forest regeneration
KW - Non-metric multidimensional scaling
KW - Prunus serotina Ehrh.
KW - Robinia pseudoacacia L.
KW - Woody invaders
UR - http://www.scopus.com/inward/record.url?scp=84878462196&partnerID=8YFLogxK
U2 - 10.1016/j.foreco.2013.05.003
DO - 10.1016/j.foreco.2013.05.003
M3 - Article
AN - SCOPUS:84878462196
SN - 0378-1127
VL - 304
SP - 192
EP - 203
JO - Forest Ecology and Management
JF - Forest Ecology and Management
ER -