Changes in nitrogen and phosphorus cycling suggest a transition to phosphorus limitation with the stand development of larch plantations

Phosphorus (P) is one of the most important factors influencing the growth and quality of larch plantations. A systematic knowledge of the dynamic changes of P in soil-plant systems can provide a theoretical basis for the sustainable development of larch plantations. We determined the concentration, biomass, and accumulation of P in five tree components (i.e., leaf, branch, bark, stem, and root), and the concentrations of various soil P fractions of larch plantations in 10-, 25-, and 50-year-old stands in northeast China. Our results showed that the N:P ratio and P concentration in leaves increased with stand age, indicating that the growth of larch plantations might be limited by P in the development of stands. The N:P ratio and P concentration in roots, and P resorption efficiency, increased with stand age, indicating the use efficiency of P could be enhanced in older stands. The concentrations of soil-labile P fractions (Resin-P, NaHCO 3 -Pi, and NaHCO 3 -Po) in 25and 50-year-old stands were significantly lower than those in 10-year-old stands, indicating the availability of soil P decreases with the development of larch plantations.

Section: Variations Of Larch N:p Ratio Pre P Concentration and P Asupporting

confidence: 91%

Section: Introductionmentioning

confidence: 99%

Distribution Changes of Phosphorus in Soil–Plant Systems of Larch Plantations across the Chronosequence

Zeng

Chen

Huang

et al. 2018

“…Larch is a fast-growing tree species, especially during the middle-age period (21-30 years). Thus, in the medium term after thinning, the uptake of P by rapidly growing larch trees leads to a decrease in soil P [58].…”

Section: Temporal Effects Of Thinning On Light Availability and Soil mentioning

confidence: 99%

Temporal Effects of Thinning on the Leaf C:N:P Stoichiometry of Regenerated Broadleaved Trees in Larch Plantations

Xie

Yan

Yuan

et al. 2020

The shift from natural mixed broadleaved forests to pure coniferous plantations results in soil degradation and the unsustainable development of plantations due to the simple stand structure and low species diversity. Thinning can practically sustain the forest structure and promote the regeneration and growth of broadleaved trees in these pure coniferous plantations. The growth of regenerated broadleaved trees is closely related to leaf ecological stoichiometry, which is strongly restricted by environmental factors such as light, soil moisture, and nutrients after thinning. However, the temporal effects of thinning on leaf C:N:P stoichiometry are still not well understood, which constrains our understanding of implementing thinning in coniferous plantations to promote the regeneration and growth of broadleaved species, and further forming the mixed larch-broadleaf forests. Here, we compared canopy openness (i.e., light availability) and the soil and leaf stoichiometry for regenerated broadleaved trees in larch (Larix keampferi) plantations in short-term (1–3 years), medium-term (4–9 years), and long-term (≥10 years) periods after thinning, taking natural mixed broadleaved forests as a control in Northeast China. The results showed that the temporal effects of thinning were not significant with respect to soil C concentrations, but significant with respect to soil C:P and N:P ratios. The regenerated broadleaved trees adjusted their leaf N concentrations and C:N ratios in response to the changed environmental conditions after thinning over time. The responses of soil and leaf stoichiometry to thinning and their significant correlation indicated a strong interaction between the soil and understory regeneration following thinning. Thus, thinning affects the soil and leaf stoichiometry of regenerated trees over time. These findings provide new insights into the conversion of pure coniferous plantations into mixed larch-broadleaf forests by controlling thinning intervals.

“…Hence, information regarding nutrient allocation in different compartments of diverse forest ecosystems is needed to reliably judge the sustainability of more intensive harvest regimes [22].Larches (Larix spp.) are an important component in many cold-temperate and boreal forests in the Northern Hemisphere [23],and the dominant timber species in plantation forests in China [24,25]. Larch plantations provide a high proportion of the timber supply, and they now cover 3.14 × 10 6 ha in China (Chinese Ministry of Forestry, 2014).…”

mentioning

confidence: 99%

“…Larches (Larix spp.) are an important component in many cold-temperate and boreal forests in the Northern Hemisphere [23],and the dominant timber species in plantation forests in China [24,25]. Larch plantations provide a high proportion of the timber supply, and they now cover 3.14 × 10 6 ha in China (Chinese Ministry of Forestry, 2014).…”

mentioning

confidence: 99%

Nutrient Allocation to Different Compartments of Age-Sequence Larch Plantations in China

Wang

Chen

Sun

2019

Increased demand for forest-derived biomass has led to more intensive harvesting practices. However, the export of large nutrient quantities with the harvested biomass may lead to the depletion of soil nutrients. Therefore, improved knowledge concerning macronutrient allocation (N, P, K, Ca, and Mg) to different components in forests along age sequences is crucial for their sustainable management. In this study, we quantified nutrient allocation to different ecosystem components, including trees, understorey, forest floor, and different soil depths within a chronosequence (6-, 15-, 23-, and 35-year-old) of larch plantations in China. We then assessed the danger of significant nutrient losses from whole tree harvesting (WTH). Nutrient amounts in trees increased with stand age due to an increase in biomass. Stems accounted for 59%–72% of tree biomass and contained 40%–50% of total tree nutrients in the 15- to 35-year-old stands. The forest floor’s nutrient quantities increased from the 6- to 23-year-old stands and then decreased in the 35-year-old plantations. Conversely, most soil indicators initially declined from 15- to 23-year-old stands and then increased in the 35-year-old stand. The total nutrient stocks were greatest in the soil (0–40 cm), which accounted for about 93%–99% of total nutrients in the larch ecosystem. These data indicate that WTH causes nutrient losses about 2.0–2.5 times higher than stem-only harvesting, when thinning 15- or clear-cut harvesting 23- and 35-year-old stands. However, nutrient losses by WTH have little effect on the soil nutrient pools. Prolonging the crop cycle of larch plantations may be beneficial to improve nutrient return through litterfall and allow available soil nutrients to recover.