Abstract
In forest systems, neighbor-induced root morphological plasticity (RMP) is species specific and environment dependent. However, related studies on leguminous woody trees remain sparse. The objectives of this study were to evaluate the root morphological response of the leguminous woody Dalbergia odorifera T. Chen to different N-fixing niche neighbors under models of root system contact and isolation and to evaluate whether such response can be modified by drought or the application of nitrogen (N). The relationship between root morphology and the relative competitiveness of the whole D. odorifera plantlet was also assessed. D. odorifera plantlets from the woody Leguminosae family were used as target species and were grown with either identical N-fixing niche D. odorifera, the heterogeneous but con-leguminous Delonix regia, or the non-leguminous Swietenia mahagoni. All plants were grown under two water conditions (100% and 30% field capacity) and two N treatments (no N application and N application). Two planting models (root system contact in Experiment 1, root system isolation in Experiment 2) were applied to neighboring plantlets. The RMP of D. odorifera was assessed based on root morphology, root system classification, root nodules, and RMP-related indices. The growth of D. odorifera was estimated based on the relative growth ratio, net assimilation rate, and leaf N content. The relative competitiveness of the whole D. odorifera plantlet was evaluated through relative yield. The results of Experiment 1 showed that D. odorifera had different RMP responses to a different N-fixing niche neighbor with root system contact. The RMP of D. odorifera was promoted by a different N-fixing niche neighbor under conditions of drought or N deficiency. Drought improved the RMP of D. odorifera exposed to a different N-fixing niche neighbor. N application converted the promoting effect of D. regia on RMP to an inhibitory effect under well-watered conditions. Experiment 2 showed that belowground interaction with a different N-fixing niche neighbor may be the only way to influence RMP, as effects of aboveground interaction were negligible. Finally, correlation analysis showed that neighbor-induced RMP might predict the relative competitiveness of the whole D. odorifera plantlet under conditions of drought or N deficiency. These findings highlight the influences of neighbors, drought, and N application on the RMP of D. odorifera and contribute to understanding neighbor-induced dynamic changes in the root traits of leguminous woody species in forest systems in the context of climate change.
Highlights
Water and nitrogen (N) are key resources that often determine individual growth, stand productivity, and dynamics of a community structure
The objectives of this study were to (1) characterize the effects of different N-fixing niche neighbors on the root morphology of leguminous woody D. odorifera with root system contact, (2) test whether the root morphology of D. odorifera is influenced by aboveground interaction with different neighbors with root system isolation, (3) determine whether this is influenced by drought and N application, and (4) evaluate whether the relative competitiveness of whole leguminous woody D. odorifera with different N-fixing niche neighbors can be predicted by Root morphological plasticity (RMP) under a given environmental condition
In the root system contact model, the root length, root surface area, root diameter, root volume, and root branching number of D. odorifera plantlets exposed to interspecific competition (Do-Dr and Do-Sm) were higher than those of plantlets exposed to intraspecific competition (Do-Do) under both the 100% field capacity (FC) and 30% FC conditions (Figure 1)
Summary
Water and nitrogen (N) are key resources that often determine individual growth, stand productivity, and dynamics of a community structure. Their low availability can induce belowground competition for resources. Niche complementarity between species would explore a more exhaustive resource compared with niche similarity (Kahmen et al, 2006). Relevant resource-containing niches between belowground competitors determine the root competitive performance of target species (Zuppinger-Dingley et al, 2014). Empirical evidence of the root plasticity of leguminous woody trees when interacting with different N-fixing niche neighbors is lacking
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
