Diverse Understory Vegetation Alleviates Nitrogen Competition with Crop Trees in Poplar Plantations

Abstract

Understory vegetation plays a crucial role in nutrient turnover and cycling in plantations, but it also competes for nutrients with crop trees when only a single species is present due to its specific nutrient requirements. However, it remains unclear whether this competition can be alleviated when the species richness of understory vegetation increases. In this study, we tested different gradients of understory vegetation species richness, including understory vegetation removal (UR), the retention of a single main understory vegetation species (RS), and the retention of natural diverse understory vegetation (RD) as part of a poplar (Populus deltoides ‘Nanlin-3804′) plantation, to study their effects on poplar growth, and to evaluate nitrogen (N) usage and how this was affected by the interactions between the poplar and understory vegetation. The results showed a generally lower periodic growth, and a significant decline in the foliar chlorophyll content and glutamine synthetase activity of poplar under treatment with RS and RD compared to those under UR treatment conducted in July 2019, which clearly indicated N competition between the understory vegetation and poplar trees. However, no significant difference was detected in the foliar chlorophyll content and glutamine synthetase activity of poplar under RD and RS treatment; only the nitrate reductase activity in poplar leaves under RD treatment declined significantly, by 22.25%, in June 2019. On the contrary, the diameter at breast height (DBH) of the poplar under RD treatment showed an increase of 34.69% from July to August 2019, compared with that under RS treatment. Furthermore, the increase in the species richness of understory vegetation resulted in an increase in the δ15N values in the poplar leaves, which was strongly regulated by the NH4+-N pool in the 10–20 cm soil layer, indicating the effective coordination of N utilization between poplar and understory vegetation when diversified understory plant species were present. These findings demonstrate the essential role of understory vegetation species diversity in alleviating N competition with crop trees, and provide guidance for understory vegetation management in poplar plantations.

Modelling possible habitats for poplar invasion in South Africa

“…This justifies their occurrence in riparian zones, and warmer and wetter parts of the country (Sperandio et al 2022;Xi et al 2021). While its invasiveness has not been extensively studied, like any other invasive species, it competes with native important species for resources, and at most outcompete them (Poudel et al 2019;Zhang et al 2021). Therefore, the results of this study are important as they enable the understanding of the patterns of their spread across the country and selected protected areas to know what interventions to put in place to monitor and manage them.…”

“…Essentially, poplar species consumes a lot of water in streams, thereby worsening the conditions for aquatic species in the streams (Théroux Rancourt, Éthier & Pepin 2015). Like any woody species, poplar competes with native species for resources, with a better chance of consuming more and more because of its growth structure and crown, which intercepts rain and sunlight that would otherwise be used by native species (Kumschick et al 2020;Zhang et al 2021). For these reasons, it is important to understand their spatial distribution and climatic drivers so that they can be appropriately monitored and managed in the country.…”

Microecological Shifts in the Rhizosphere of Perennial Large Trees and Seedlings in Continuous Cropping of Poplar

“…The poplar tree, belonging to the Populus spp., holds significant importance as a timber forest species globally. However, the practice of short-term rotating harvests and whole-tree harvesting of poplar has resulted in detrimental consequences such as severe site degradation and declining productivity [ 4 ]. At the same time, the prevalence of single cultivation and continuous cropping has become more widespread, significantly constraining wood production and ecological advantages [ 5 ].…”

Age-Related Changes in Water and Nitrogen Utilization in Crop Trees and Understory Vegetation in a Hinoki Cypress Plantation Forest in Kochi City, Southern Japan

“…The development of understory vegetation in conifer plantations is crucial for improving biodiversity and ecosystem services [1][2][3][4][5][6][7]. The method of forest management can affect stream water chemistry [8][9][10][11].…”