Effects of Fertilizers and Litter Treatment on Soil Nutrients in Korean Pine Plantation and its Natural Forest of Northeast China

Organic and inorganic soil fertilizer addition or removal pose significant effects on soil nutrients. As climate change and other anthropogenic factors are causing deprivation in soil nutrient profiles and altering its proper functioning, complete insight into fertilizer modification and its consequences is required for understanding the sustenance of forest ecosystems. In this regard, an experiment was conducted at Liangshui National Nature Reserve, northeast China, in which two forest soil types (i.e., Korean pine plantation and natural Korean pine forest) were evaluated for their response to external fertilizer applications and litter treatments. The litter treatments were litter application as Ck (undisturbed litter), RL (removed litter) and AL (Alter/double litter i.e., litter removed from RL was added in double litter plots), whereas the synthetic fertilizer treatments were Control (No added N and P), Low (5 g N m(-2) a(-1) + 5 g P m(-2) a(-1)), Medium (15 g N m(-2) a(-1) + 10 g P m(-2) a(-1)) and High (30 g N m(-2) a(-1) + 20 g P m(-2) a(-1)). The outcome showed that soil organic carbon (SOC) was directly proportionate to forest litter amounts. Synthetic fertilizers affected soil total nitrogen (STN) and maximum amounts were recorded in plots with H: 30 g N m(-2) a(-1) + 20 g P m(-2) a(-1), as 3.03 +/- 0.35 g kg(-1) in AL. Similarly, altered litter/double was most effective in enhancing the quantity of soil total phosphorus (STP) (0.75 +/- 0.04 g kg(-1)). Soil sampling carried out during the start and end of the experiment showed decreases in the sixth sampling of: SOC (4-23%), STN (7.5-10.8%) and STP (8.51-13.9%). A positive correlation was observed between SOC and total nitrogen; C:N ratio also increased with SOC. Principal component analysis (PCA) on captured a total of 62.1% variability, on the x-axis (35.1%) and on the y-axis (27%). It was concluded that combined application of N and P at the level of 30 g N m(-2) a(-1) + 20 g P m(-2) a(-1) under AL (Alter/double litter) treatment level improved soil total N and P content. The results clearly depicted that forest litter is an important source for building up of soil organic matter, however for attaining maximum sustenance capabilities in soil, the continuity of fertilizer application in either form is a prerequisite.

Automated summary

Organic and inorganic soil fertilizer addition or removal have significant effects on soil nutrients, and climate change and anthropogenic factors further contribute to soil nutrient deprivation and altered functioning. This study emphasizes the importance of understanding fertilizer modification and its consequences for sustaining forest ecosystems.