Bidirectional Nitrogen Transfer and Plant Growth in a Mixed Plantation of N2-Fixing Species and Eucalyptus urophylla × E. grandis under Different N Applications

Abstract

N2-fixing species play a crucial role in mixed-plantations as they improve stand productivity. To quantify the N transfer from N2-fixing species to Eucalyptus (Eucalyptus urophylla × E. grandis) in N2-fixing species/Eucalyptus plantations, we established a pot experiment and confirmed the occurrence of this process under natural conditions. The 15N was traced in labeled species as well as in neighboring tree species after labeling, and the growth was evaluated in short-term natural trials. Our results showed that a bidirectional N transfer occurred. The amount of net N transfer was 21.8–127.0 mg N plant−1, which was equal to 1.5–21.2% of the total nitrogen (TN) that accumulated in Eucalyptus plants under pot conditions, was transferred from Dalbergia odorifera to Eucalyptus. The amount of N transferred significantly decreased with the increasing N application rate but increased with time after labeling. Compared with the results for the Eucalyptus monocrop, the soil N concentration (including NO3−-N and NH4+-N) greatly improved when D. odorifera was introduced together with Eucalyptus under both field and pot conditions. Furthermore, the results under field conditions were consistent with the results of the pot experiment. The dry matter (DM) yield (14.5–16.4%) and the N content (5.1–9.6%) in Eucalyptus increased when mixed together with D. odorifera, but the N content in and DM yield of D. odorifera slightly decreased. It is concluded that the N transfer between Eucalyptus and D. odorifera is a much more important dynamic process than previously recognized, and Eucalyptus and legume intercropping is a successful management practice because N transfer provides a significant amount of N required for Eucalyptus productivity.

Nitrogen transfer between plant species with different temporal N‐demand

“…Complementarity has been mainly approached between species that acquire and exchange different resources. This is the case of legumes that gain a high N content due to their association with N-fixing bacteria and can transfer it to multiple species in their community (Chalk et al, 2014;Montesinos-Navarro et al, 2017;Paula et al, 2015;Yao et al, 2021). Similarly, columnar cacti accumulate water in their vascular tissue and it can be transferred to the dominant legumes with which they co-occur (Montesinos-Navarro, Verdú, et al, 2019).…”

Leaf Traits Explain the Growth Variation and Nitrogen Response of Eucalyptus urophylla × Eucalyptus grandis and Dalbergia odorifera in Mixed Culture

“…Obviously, the interspecific competition in mixed cultivation tilted the balance of resource acquisition compared to the relatively equal intraspecific competition of the same plant species in monoculture. A higher root biomass allows for a greater soil N uptake capacity in urophylla × E. grandis [53], even robbing part of the N in D. odorifera to achieve interspecific N transfer [54,55]. Regarding leaf physiological traits, the Pn in E. urophylla × E. grandis under monoculture increased with N application, and this change was accompanied by an increase in gs and CE and a decrease in Ci (Figure 1).…”

Intercropping and nitrogen enhance eucalyptus productivity through the positive interaction between soil fertility factors and bacterial communities along with the maintenance of soil enzyme activities

“…Since plant growth and adaptability are intricately linked to the highly diverse array of microorganisms in the rhizosphere, a reasonable planting strategy should sustain soil microbial activity and be beneficial for the microbial community structure (Li et al, 2022; Zhang et al, 2021), including increasing soil pH, enzyme activity, organic matter, and N content (Tian et al, 2019). Introducing Dalbergia odorifera with eucalyptus has been proven to support considerable increases in biomass/yield compared with the application of synthetic fertilizer while increasing N availability and maintaining soil fertility (Yao, Goodale, et al, 2021; Yao, Zhang, et al, 2021). Furthermore, a combination of eucalyptus and Acacia mangium enhanced soil quality and increased soil microbial diversity (Koutika et al, 2020; Zagatto et al, 2019), as well as the soil organic carbon content (Forrester et al, 2010; Koutika et al, 2019).…”

“…Significant increases in biomass production and soil N availability have been observed in our previous mixed plantation (Yao, Goodale, et al, 2021); however, the success and failure of intercropping are highly variable with changes in resource availability or fertilization (Forrester et al, 2006;Nouvellon et al, 2012). Thus, we examined…”