Mixed Broadleaved Tree Species Increases Soil Phosphorus Availability but Decreases the Coniferous Tree Nutrient Concentration in Subtropical China

Abstract

Phosphorus (P) is a key limiting nutrient in subtropical forests and mixed forests with broadleaved species have been expected to stimulate P cycling, compared to pure conifer plantations. However, the mixture effect of Chinese fir (Cunninghamia lanceolata (Lamb.) Hook.) and broadleaved species on rhizosphere soil and coniferous tree P dynamics is unclear. In our study, eight plots of a single species of a Chinese fir plantation (pure plantation, PP) and eight mixed plantations (mixed plantation, MP) with broadleaved tree species (Michelia macclurei Dandy in Hunan Province or Schima superba Gardn. et Champ. in Fujian Province) were selected in subtropical China. Six P fractions in the rhizosphere and bulk soils were analyzed by a modified Hedley P fractionation method. Phosphorus fractions and nitrogen (N) concentrations in different root orders, different age fresh needles and twigs, and needle and twig litter of Chinese fir were measured. Our results showed that available P, slowly released P, occluded P, and the total extractable P in rhizosphere soil were significantly higher in MP than PP (p < 0.05). In contrast, P and N concentrations in the transportive roots and two-year old needles were generally higher in PP than MP. Meanwhile, the slowly released P, occluded P, total extractable P, and residual P in rhizosphere soil were negatively correlated with P concentrations in young (absorptive and transportive roots, one- and two-year old needles) but not old tissues (storative roots, three-year old needles and litters). In conclusion, mixture may increase soil P availability through the rhizosphere effect, but can decrease P and N concentration of Chinese fir tissues by competition between Chinese fir and broadleaved species. Clearly, the mixture effect may differ in soil and plant nutrients, and this issue needs be taken into consideration when converting a pure conifer plantation into a mixed-species forest.

Mixed planting enhances soil multi‐nutrient cycling by homogenizing microbial communities across soil vertical scale

“…We found that mixed planting effectively improved soil nutrient content in the surface soil (0–20 cm), with soil AP, NH 4 + ‐N, and SOC contents significantly higher therein than those in pure plantations. These observations were consistent with those of previous studies reporting a reduced soil fertility in pure Chinese fir or other coniferous species plantations (Bu et al, 2020; Ma & Chen, 2018; Nunes et al, 2011; Wang, Liu, et al, 2018). This suggests that raising forest productivity by planting should mainly focus on the surface soil.…”

“…In this study, we aimed to assess the effects of different afforestation models on SMC in the surface (0–20 cm) and subsurface (20–40 cm) soils, and to decode the roles and underlying mechanisms of bacterial and fungal communities that drive SMC. Since mixed afforestation alters the allocation schema of litter and root exudates in different soil layers (Bu et al, 2020; Jackson et al, 2017), we hypothesized that: (1) mixed afforestation maintains SMC down to the subsurface soil; and (2) the ecological importance of soil bacterial and fungal communities in driving SMC varies along the vertical spatial scale.…”

“…Since mixed afforestation alters the allocation schema of litter and root exudates in different soil layers (Bu et al, 2020;Jackson et al, 2017), we hypothesized that: (1) mixed afforestation maintains SMC down to the subsurface soil; and (2) the ecological importance of soil bacterial and fungal communities in driving SMC varies along the vertical spatial scale. The afforestation history of the study area spans over 50 years.…”

High within-tree leaf trait variation and its response to species diversity and soil nutrients

“…Inversely, diversity of co-existing species can decrease competition and promote the availability of resources through resource-use complementarity (Loreau and Hector 2001; Cardinale et al 2007; Barabás, Michalska-Smith, and Allesina 2016). For example, several studies showed higher soil total phosphorus supply in species mixtures, because a greater number of different forms of soil P were used compared to those present in monocultures (Zou, Binkley, and Caldwell 1995; Bu et al 2020). Additionally, in forests, increased species richness can increase litter diversity, abundance (Huang et al 2017) and decomposition (Lin et al 2021), thus increasing the incorporation of organic matter in the soil and contributing to enriching it with nutrients (Gartner and Cardon 2004).…”

Study on Microwave Pretreatment Technology to Improve the Effect of Shellac Impregnation of Fast-Growing Chinese Fir

“…Chinese fir (Cunninghamia lanceolata) is an important species in the southern provinces of China [1,2]. Chinese fir wood that was harvested from natural forests has been widely used as furniture and building materials owing to its excellent characteristics, such as a straight texture, uniform structure, and ability to resist insects and wood-rot fungi [3].…”