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Irrigation and nitrogen application directly affect the availability and distribution of soil nutrients. Understanding the response of soil nutrients to long-term water–fertilizer coupling conditions is helpful to improve the management and use efficiency. Irrigation was divided into three gradient levels, which accounted for 45%, 60%, and 75% (W1, W2, and W3) of the field water holding capacity. Based on pure nitrogen, four levels of nitrogen application were set: 0.0, 101.6, 203.2, and 304.8 kg·hm−2 (N0, N1, N2, and N3). We measured tree height and diameter at breast height (DBH), and we analyzed the chemical properties of the soil at 0–40 cm depth, from 2007 to 2020. The ranges of DBH, tree height, individual volume, and stand volume were 5.80–25.25 cm, 6.10–16.47 m, 0.01–0.37 m3, and 11.76–481.47 m3·hm−2, respectively. The contents of organic matter, total nitrogen, available phosphorus, and available potassium in the soil ranged from 8.60 g·kg−1 to 18.72 g·kg−1, from 0.21 g·kg−1 to 0.79 g·kg−1, from 8.09 mg·kg−1 to 47.05 mg·kg−1, and from 90 mg·kg−1 to 322 mg·kg−1, respectively. Soil pH value decreased rapidly at a rate of 0.31 units per year for the first five years. Irrigation and nitrogen application, and their interaction, had significant (p < 0.01) effects on soil total nitrogen, available phosphorus, available potassium, and nitrate-nitrogen. We suggest maintaining the field water holding capacity above 60%, with a nitrogen application rate of 203.2 kg·hm−2, to save water, maintain soil fertility, and optimize soil nitrogen supply. Our study aimed to achieve scientific and accurate fertilization of Populus tomentosa stands over different periods, to alleviate the decline of soil fertility, and to improve the utilization rate of water and fertilizer through long-term nutrient monitoring.

Traditional methods to deal with thinning shreds (twigs, bark, etc.) include using them as fuelwood (artificially taken out of the forest) and stacking in situ natural decompositions (slow decomposition and nutrient return to the field). These methods will cause the loss of nutrients in the forest, and composting with additives can effectively promote nutrient circulation effectively. The purpose of our study was to explore the effects of composts of forest thinning shreds with different additives on soil and tree growth in semimature Pinus tabuliformis Carr. We selected four composts of forest thinning shreds (T1 adjustment of C/N and C/P + 0.2% priming; T2: adjustment of C/N and C/P + 0.2% common compost; T3: adjustment of C/N and C/P only; T4: raw material grinding of thinning shreds) and applied them in the volume of 900 g·m−2, which were made in the early stage. The soil nutrient content, microbial characteristics, and growing volume of Pinus tabuliformis were measured at 0.5, 1, and 1.5 years after fertilization. The soil became acid after one year of fertilization, having a great impact on the 0–20 cm soil layer. At 0.5 years of fertilization, the total nitrogen (TN) content of the soil with priming compost (T1) was 1.5 times higher than that of the control group (T5); the soil organic matter (SOM) was increased by 4.93–6.41 mg·kg−1. After one year of fertilization, the difference in the soil microbial carbon and nitrogen (MBC and MBN) content of each treatment decreased gradually. Soil sucrase activity was the highest after fertilization, and different composts had the greatest impact on urease activity in the 0–20 cm layer; the alkaline phosphatase (AKPase) activity of soil with common compost (T2) changed the most, and after 0.5 years of fertilization, the acid phosphatase (APase) activity of T1 in the two layers increased by 0.31 mg·g−1 and 0.1 mg·g−1, and the increase in of T2 was slightly lower than that of T1. There were significant differences in the number of bacteria, fungi, and actinomycetes compared to T1 and T2 with other treatments. T1 promoted the height growth (H) of trees three times higher than T5 and T2 promoted the growth of diameter at breast height (DBH) by 2.5 cm. The results showed that T1 and T2 had obvious effects on promoting soil nutrient content, microbial biomass accumulation, and forest growth, and the application of compost had no significant effect on promoting understory regeneration. The findings of this study show that using compost with priming can effectively increase the soil nutrient content, microbial activity, and quantity of Pinus tabuliformis effectively in terms of promoting the growth of trees and reducing the nutrient loss caused by thinning.

This study aimed to explore the effects of different additives on tending shreds of Platycladus orientalis (L.) Franco. Two different additives (priming 0.2% and common compost 0.2%) combined with C, N, and P adjustment of raw material treatments were tested on the temperature, moisture, EC, pH, lignocellulose degradation rate, nutrient content, and toxicity of compost. Priming made the compost temperature rise rapidly, and the peak temperature of the composting group with priming reached 51 °C. At the end of composting, the moisture in each treatment from high to low was in the order: common compost > priming > C/N, C/P adjustment only > control group. The increase of EC in the treatments with additives was great, and the peak value of EC in the treatment of priming was 1.30 ms·cm−1, which was 3.9 times higher than that of the control group. At the end of composting, the decomposition rate of cellulose in priming compost was 1.7 times higher than that in the control group, and the hemicellulose decomposition rate in the common compost group was 3.2 times higher than that in the control group. By the end of composting, the pH value of the composts in additive treatments was above 7.0, and the pH value of the priming treatment was the highest (7.5). The highest content of organic matter was found in the priming treatment, which was 52%, 1.7 times higher than that in the control group. The total nutrient content (TN + K2O + P2O5) of additive treatments was higher than 5.0%, and the priming treatment was 2.7% higher than that of the control group. By the end of composting, the germination rate and germination index ranged from 88% to 91% and 60% to 81%. Except for the control group, the C/N ratio of other treatments decreased to below 25. Additives can accelerate the decomposition of raw materials, shorten the composting cycle, and improve the quality of composts, and the effect of adding priming is the most significant.

Foliar spraying is employed in this study to test the effect of 5-aminolevulinic acid (hereafter 5-ALA), aqueous-organic solvents and their compounds on the quality of Rosa rugosa. The results showed that, compared with the control group (foliar spraying of fresh water), foliar application of 5-ALA or aqueous-organic solvents singly, or in combination, all have various improving effect on rose leaf area, flower diameter (indicating size of the flower), stem length, opening rate, flower color and the total biomass; foliar spraying of 5-ALA and aqueous-organic solvents jointly or mere 5-ALA both can increase the chlorophyll content of unit area leaf, while mere aqueous-organic solvents will decrease the unit area leaf chlorophyll content. The conclusion is that, joint foliar spraying of 5-ALA and aqueous-organic solvents will lead to the optimal result on the quality of Rosa rugosa by way of making full use of the mutually beneficial interaction between 5-ALA and aqueous-organic solvents. This finding no doubt, will shed light on the improvement of Rosa rugosa quality and benefit the future development of the Rosa rugosa industry.

Understanding the spatial distribution and controlling factors of soil organic carbon (SOC) at different scales is essential for an accurate estimation of soil organic carbon stocks. Furthermore, this understanding is vital for evaluating the impact of soil management on both soil quality and climate change. This study was conducted in a Loess revegetated small watershed and the effects of the topography and vegetation factors on the content and distribution of SOC at different soil depths were evaluated. Soil profiles (0–200 cm; n = 122) were sampled that represent six vegetation types (i.e., natural mixed forests, artificial mixed forests, artificial forests with a single tree species, shrubbery, and grassland) and four topographic factors (i.e., elevation, slope gradient, slope position, and slope aspect). The following results were obtained: (1) The mean SOC of the 200 cm soil profile ranged from 2.34 g kg−1 to 5.70 g kg−1, decreasing with increasing soil depth. (2) The interactions between vegetation type and topography and soil depth significantly impacted SOC (P

Stand density directly affects the distribution of ecological factors such as light, heat, and water in forest communities and changes the diversity and structure of undergrowth species, thereby affecting soil health. Fine roots can provide water and nutrients to plants rapidly in the fierce competition of soil resources, so as to get rid of environmental factors. This study examined the fine-root responses of the Populus tomentosa clone S86 to three stand densities (plant &times, row spacing: 2 &times, 2 m, 4 &times, 3 m, 4 &times, 5 m). We measured the biomass, morphology, and nitrogen content of lower- (1&ndash, 3 order) and higher-order (&gt, 3 order) fine roots, and analyzed soil chemical properties in 10&ndash, 30 cm. The soil from the density (2 &times, 2 m) stands showed lower soil organic matter content, available nitrogen, available phosphorous, and available potassium than others. Obviously, lower and higher-order fine roots were different: biomass of the &gt, 3 order accounted for 77&ndash, 87% of the total biomass, 1&ndash, 3-order fine-root diameter around 0.28&ndash, 0.38 mm, while &gt, 3-order fine root were 1.28&ndash, 1.69 mm, the length of 1&ndash, 3-order fine root was longer than the &gt, 3 order, and root length density, specific root length, and nutrient content between the 1&ndash, 3 and &gt, 3 orders were different. At 2 &times, 2 m, 1&ndash, 3-order fine-root biomass was the highest, 132.5 g/m3, and the 1&ndash, 3-order fine-root length, diameter, surface, root length density was also the highest, at the same time, the 1&ndash, 3-order fine-root total nitrogen and organic matter content was also the highest, while the &gt, 3 order was highest under 4 &times, 3 m or 4 &times, 5 m. The findings of this study show that stand density affected the available nutrient content of the soil. When soil resources were poor, the biomass, morphology, and chemical content of fine roots were adjusted to increase the nutrient absorption rate, particularly in the lower-order roots.

The objective of this research was to investigate the morphology, genesis and classification of soils formed on the Sygera Mountain in Tibet. Five typical soil profiles were collected in genetic soil regions, such as alpine frozen desert soil, alpine meadow soil, brown soil, etc., and their soil-forming environments were investigated, and then soil samples were taken from various soil layers of the soil profiles for analysis of physical and chemical properties. According to the current diagnostic criteria of the Chinese soil taxonomy (CST) and world reference base for soil resources (WRB) classification systems, the five soil profiles were identified and classified. Results showed that (1) the main diagnostic horizons and diagnostic characteristics are mollic epipedon, umbric epipedon, cambic horizon, lithic contact, aridic soil moisture regime, udic soil moisture regime, gaelic soil temperature regime, cryic soil temperature regime, and base saturation. (2) Based on the “Key to the Chinese Soil Taxonomy (Third edition)”, the five soil profiles could be sorted into two orders, two suborders, three groups, and three subgroups (lithic calic-cryic aridisols, typic molli-cryic cambosols, and typic umbri-cryic cambosols). However, based on WRB, the five soil profiles are classified into two orders, four suborders, four groups, and four subgroups (yermic calcisols, humic cambisols, dystric cambisols, and haplic cambisols). (3) The differentiations of the classification of the five profiles between the two classification systems varied significantly with classification level, and the relationships between the various classification levels of CST and WRB are complicated ones rather than the simple one-to-one type.