Background: Maize-soybean relay-intercropping (MS_R) is a famous system of crop production in developing countries. However, maize shading under this system directly affects the light quality and intensity of soybean canopy. This is a challenging scenario in which to implement the MS_R system, in terms of varieties selection, planting pattern, and crop management since the duration of crop resource utilization clearly differs. Methods: Therefore, this experiment aimed to elucidate the effect of leaf excising treatments from maize top to fully clarify the needs and balance of light quality and intensity of intercrop-soybean under MS_R in field conditions. The effects of different leaf excising treatments (T0, no removal of leaves; T2, removal of two topmost leaves; T4, removal of four topmost leaves; T6, removal of six topmost leaves from maize plants were applied at first-trifoliate stage (V₁) of soybean) on photosynthetically active radiation transmittance (PAR_T), red to far-red ratio (R:FR), morphological and photosynthetic characteristics and total biomass production at second-trifoliate stage (V₂), fifth-trifoliate stage (V₅), and flowering-stage (R₁) of soybean were investigated through field experiments for 2-years under MS_R. Results: As compared to T0, treatment T6 increased the PAR_T and R:FR ratio at soybean canopy by 77% and 37% (V₂), 70% and 34% (V₅), and 41% and 36% (R₁), respectively. This improved light environment in T6 considerably enhanced the leaf area index, SPAD values and photosynthetic rate of soybean plants by 66%, 25% and 49% at R₁, respectively than T0. Similarly, relative to control, T6 also increased the stem diameter (by 29%) but decreased the plant height (by 23%) which in turn significantly increased stem breaking strength (by 87%) by reducing the lodging rate (by 59%) of soybean plants. Overall, under T6, relay-cropped soybean produced 78% of sole soybean seed-yield, and relay-cropped maize produced 81% of sole maize seed-yield. Our findings implied that by maintaining the optimum level of PAR_T (from 60% to 80%) and R:FR ratio (0.9 to 1.1), we can improve morphological and photosynthetic characteristics of soybean plants in MS_R. Therefore, more attention should be paid to the light environment when considering the sustainability of MS_R via appropriate planting pattern selection.

Phosphorus (P) is the restraining aspect in the forest ecosystem, particularly in temperate regions, and makes the ecosystem more liable to nitrogen (N)-derived acidification. However, it remains poorly understood how N and P fertilization together affects soil-P availability and other soil properties. To address this question, a factorial experiment was conducted with N and P additions under two forest ecosystems, i.e., Korean pine plantation (KPP) and natural Korean pine forest (NKPF). Both forests were divided in to three subplots and each subplot underwent four different treatments, i.e., C: control (no N and P addition), L: Low treatment (5 g N m⁻² a⁻¹ + 5 g P m⁻² a⁻¹), M: Medium treatment (15 g N m⁻² a⁻¹ + 10 g P m⁻² a⁻¹), and H: High treatment (30 g N m⁻² a⁻¹ + 20 g P m⁻² a⁻¹). Results revealed that the soil-P fractions changed during N and P fertilization over time although organic-P (Po) fractions were lower than inorganic-P (Pi) fractions. The residual P was increased overall, along with N deposition in soil. Soil organic carbon (SOC) was more present in NKPF soils as compared to KPP. Principal component analysis (PCA) indicated that at medium treatment there is maximum availability of P fractions as compared to other treatments in both forests, while high treatment showed some fixation of P in soils across both forests. Furthermore, SOC showed a negative correlation with residual P, while pH showed a positive correlation. Total N in soil showed a negative correlation with soil pH and residual P. Therefore, it is recommended that application of N and P at the rate of 15 g N m⁻² a⁻¹ + 10 g P m⁻² a⁻¹ is suitable in these two forest types to enhance P availability.

Coarse wood debris (CWD) plays a critical role in forest productivity, nutrient cycling, decomposition, and carbon sequestration, and shapes the carbon pool in the forest ecosystem. However, the elemental composition of CWD varies among different forest types and decay classes for the same dominant tree species (Pinus koraiensis, PK). We compared CWD elemental composition across different forest types (Picea koraiensis-Abies nephrolepis-Pinus koraiensis forest (PAPF), Betula costata-Pinus koraiensis forest (BPF), Tilia amurensis-Pinus koraiensis forest (TPF)), considering four classes of wood decay. Results showed that N, P, Mg, Mn, Na, Zn, S, Al, and Fe concentrations almost totally increased with decay level for all three forest types, except for K in all three forest types and B in Picea koraiensis-Abies nephrolepis-Pinus koraiensis forest (PAPF). Similarly, maximum concentrations of N, P, B, Mg, K, C, Zn, and Mn of CWD were observed in Betula costata-Pinus koraiensis forest (BPF) under varying decay classes, but their maximum concentrations of Fe and S were found in Picea koraiensis-Abies nephrolepis-Pinus koraiensis forest (PAPF) and Tilia amurensis-Pinus koraiensis forest(TPF), respectively. Only C content did not significantly differ in decay classes across all three forest types. The C:N ratio decreased significantly with increasing decay levels across all forest types. The decay rates were significantly related to N concentration and C:N ratio in decay classes across all forest types. These results suggest that C and N concentration are the key factors affecting its decomposition. The variation in nutrient concentrations observed here underscores the complexity of nutrients stored in wood debris in forested ecosystems.

Globally, atmospheric nitrogen (N) deposition is rising, adversely impacting soil health, i.e., increasing soil acidity. While phosphorus (P) is the limiting element in the temperate environment and plays a key role in making the ecosystem more vulnerable to N-derived acidification. The impact of elevated N and P inputs on soil acidity and exchangeable base cations have been extensively studied; however, few studies have focused on these parameters, especially within various soil aggregate fractions in the temperate forest. In 2017, a field experiment was conducted under N and P additions with four soil aggregate fractions (>5 mm, 2–5 mm, 0.25–2 mm, and KPP. Thus, soil acidification is primarily caused by a decrease in base cations, such as Ca²⁺ and Mg²⁺, and increase in exchangeable Fe³⁺ and Al³⁺ ions in large macro-aggregates and macro-aggregates, which leads to the depletion of soil nutrients. The initial pH value (5.69) in >5 mm soil aggregate was decreased to (5.4) under high fertilizer application, while a minimum value of 5.36 was observed in 0.25–2 mm aggregates under high fertilizer application. The same trend was observed in all aggregates because of decrease in base cations, which, in turn, affects the vitality and health of the forests.