Do pioneer species enhance early performance of native species in subtropical shrublands? An examination involving six native species in South China

Abstract

This paper examines the following questions: (1) Do early pioneer species have a greater impact on the survival and growth of different successional native trees compared to the shrub Rhodomyrtus tomentosa? (2) Do canopy treatments affect soil nutrients and light availability? (3) What is the mechanism underlying the interaction between nurse species and target species? Degraded shrubland sites (Heshan, Guangdong, China), under moist subtropical conditions were studied. About 1-year-old seedlings of Pinus massoniana, Schima wallichii, Schefflera heptaphylla, Castanopsis hystrix, Cryptocarya chinensis and Castanea chinensis were transplanted under the canopy of R. tomentosa, Dicranopteris dichotoma and in open interspaces without vegetation. Survival and growth were recorded from the first growing season after planting. Leaf gas exchange, water potential, soil physicochemical characters and irradiation were then measured. Canonical redundancy analyses (RDA) were used to evaluate the relationships between environmental factors and seedling survival and growth conditions. Both R. tomentosa and D. dichotoma canopy treatment facilitated seedling survival and growth either directly or indirectly. Irradiance/radiation was considered the most important resource (factor) for seedling growth in subtropical regions, however, soil nutrients and species are yet to be examined simultaneously with irradiance/radiation under field conditions. We conclude that early successional species facilitates the survival and growth of late successional species in subtropical shrublands. However, further predictions of successional trajectories remain elusive and are influenced by stochastic processes, including arrival order, shade tolerance, physiological character of the colonizing species and their competitive interactions.