Search Results (7)

The reserve of litter is expected to be reduced on the forest floors of pine plantations dually for the prevention of high risks of forest fires and with a more practical probability of reuse. Lignin and cellulose are the two key constitutive components in litter residues that account for the highest proportion of carbon but are the last to be fully decomposed. The existing trials started examining the mechanisms behind decomposing these two components in response to the combined driving forces of microclimatic factors, forest structure, and stand properties. However, the results were mostly limited to a local-scale ecosystem, and the evidence was reported to be highly scattered across varied conditions globally. Awareness about the combined effects of the driving forces behind the lignin and cellulose contents in the litter of plantations on a large scale is still scarce. In this study, a total of 60 Pinus tabuliformis Carr. plantations (40-year-old) were investigated for their litter quality, regional meteorological factors, soil properties, and stand structure in a provincial area across Liaoning, northeast China. High lignin (40%–43%) and cellulose contents (15%–20%) were found to be located mainly in stands around the biggest city of Shenyang. Rainfall was a key factor that determined the decomposition, but neither the forest structure nor soil nutrient content generated direct effects on the two litter components. The combined factors of low soil pH (~5.8) and high rainfall (~3.0 mm per day) together mainly accounted for the promotion of natural litter decomposition. Full article

This experiment was conducted to define changes in metabolic pathways in response to mandibulate insect feeding and to provide a reference for further investigation of the molecular mechanisms underlying the development of conifer resistance. Chinese pine (Pinus tabuliformis Carr.) in good growth status in natural condition was chosen for stimulation by 10 pine caterpillars (Dendrolimus tabulaefomis Tsai et Liu) as feeding stimulation (FS), leaf clipping control (LCC) as mechanical damage, and CK group (with no treatment) (recorded as 0 h). The metabolome and total flavonoid content were measured in the needles at 0, 2, and 8 h after treatment. Plant hormones were measured with needles at 0, 0.5, 1, 1.5, 2, 4, 6, and 8 h after different treatments. The results show that a total of 30.8% flavonoids are identified by metabolomics analysis. Compared with leaf clipping control, feeding stimulation of Chinese pine caterpillars significantly induced the upregulation of metabolites in the flavonoid pathway in Chinese pine, and the plant hormones JA and IAA showed expression trends consistent with those of the metabolome. According to the biological processes of the four plant hormones involved, JA and SA are mostly involved in resistance formation, and in this study, both of them also have fluctuating expressions influenced by feeding stimulation, while the expressions of the growth-related hormones IAA and ABA have no significant changes at other time points except for 1 h after treatment. Thus, the flavonoid pathway is one of the main pathways involved in resistance formation in conifers, and JA and IAA are involved in the formation of resistance. Full article

Ecological stoichiometry is useful for revealing the biogeochemical characteristics of flows of nutrients and energy between plant and soil, as well as the important implications behind these ecological phenomena. However, the ecological stoichiometric linkages among leaf, litter, soil, and enzymes in the natural forests of the Loess Plateau remain largely unknown. Here, leaf, litter, and soil samples were collected from four age classes of natural Pinus tabuliformis Carr. (P. tabuliformis) to explore the deep linkages among these components. We measured the total carbon (C), total nitrogen (N), and total phosphorus (P) concentrations of leaf and litter, as well as the concentrations of soil organic C, total N, total P, nitrate N, ammonium N, available P, and the activities of β-1,4-glucosidase (a C-acquiring enzyme), β-1,4-N-acetylglucosidase (an N-acquiring enzyme), and alkaline phosphatase (a P-acquiring enzyme) in the topsoil (0–20 cm). The average leaf N:P was 6.9 indicated the growth of P. tabuliformis was constrained by N according to the relative resorption theory of nutrient limitation. The C:N, C:P, and N:P ratios in leaf, litter, and soil and the enzyme activity were not significantly different among age classes (p > 0.05). Litter C:N (43.3) was closer to the ratio of leaf C:N (48.8), whereas the litter C:P (257.7) was obviously lower than the ratio of leaf C:P (338.15). We calculated the stoichiometric homeostasis index (1/H) of leaf responses to soil elements and enzyme activities and found that the relationship between leaf C:P and soil C:P was homeostatic (p < 0.05), whereas the remaining indices showed the leaf stoichiometries were strictly homeostatic (p > 0.05). Correlation analysis showed both litter C:P and N:P were positively correlated with leaf and soil C:P, while the stoichiometric ratios of soil elements and enzymes were obviously irrelevant with leaf stoichiometries (p > 0.05). Partial least squares path modeling indicated that litter significantly changed soil element and enzyme characteristics through direct and indirect effects, respectively. However, soil elements and enzymes impacted leaf stoichiometries barely, which was further confirmed by an overall redundancy analysis. In summary, C:N:P stoichiometry within the plant–soil continuum revealed that natural P. tabuliformis is a relatively stable ecosystem in the Loess Plateau, where the element exchanges between plant and soil maintain dynamic balance with forest development. Further studies are needed to capture the critical factors that regulate leaf stoichiometry in the soil system. Full article

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. Full article

Ovule abortion is a common phenomenon in plants that has an impact on seed production. Previous studies of ovule and female gametophyte (FG) development have mainly focused on angiosperms, especially in Arabidopsis thaliana. However, because it is difficult to acquire information about ovule development in gymnosperms, this remains unclear. Here, we investigated the transcriptomic data of natural ovule abortion mutants (female sterile line, STE) and the wild type (female fertile line, FER) of Pinus tabuliformis Carr. to evaluate the mechanism of ovule abortion during the process of free nuclear mitosis (FNM). Using single-molecule real-time (SMRT) sequencing and next-generation sequencing (NGS), 18 cDNA libraries via Illumina and two normalized libraries via PacBio, with a total of almost 400,000 reads, were obtained. Our analysis showed that the numbers of isoforms and alternative splicing (AS) patterns were significantly variable between FER and STE. The functional annotation results demonstrate that genes involved in the auxin response, energy metabolism, signal transduction, cell division, and stress response were differentially expressed in different lines. In particular, AUX/IAA, ARF2, SUS, and CYCB had significantly lower expression in STE, showing that auxin might be insufficient in STE, thus hindering nuclear division and influencing metabolism. Apoptosis in STE might also have affected the expression levels of these genes. To confirm the transcriptomic analysis results, nine pairs were confirmed by quantitative real-time PCR. Taken together, these results provide new insights into ovule abortion in gymnosperms and further reveal the regulatory mechanisms of ovule development. Full article

Chinese pine (Pinus tabuliformis Carr.) is the main forest species in northern China, with the potential to dramatically affect biotic and abiotic aspects of ecosystems in this region. To discover the rainfall partitioning patterns of different growth periods of Chinese pine forest, we studied the throughfall (Tf), stemflow (Sf) and canopy interception (I) in three stand ages (40-, 50-, 60-year-old) in Liaoheyuan Natural Reserve of Hebei Province during the growing seasons of 2013 and 2014, and analyzed effect of rainfall amount, rainfall intensity, and canopy structure on rainfall partitioning in Chinese pine forest. The results showed that throughfall decreased with the stand age, accounting for 78.8%, 74.1% and 66.7% of gross rainfall in 40-, 50- and 60-year-old Chinese pine forests, respectively. Canopy interception, on the other hand, increased with the stand age (20.4%, 24.8%, and 32.8%, respectively), while the pattern in stemflow was less clear (0.8%, 1.1%, and 0.6%, respectively). As rainfall intensity increased, the Tf and Sf increased and I declined. Additionally, our results showed that leaf area index (LAI) and the diameter at breast height (DBH) increased with age in Chinese pine stands, probably explaining the similar increase in canopy interception (I). On the other hand, the mean leaf angle, openness, gap fraction all decreased with the stand age. Stepwise regression analysis showed that the rainfall amount and LAI were the major determinants influencing the rainfall partition. Our study highlights the importance of stand age in shaping different forest canopy structures, and shows how age-related factors influence canopy rainfall partitioning. This study also significantly adds to our understanding the mechanisms of the hydrological cycle in coniferous forest ecosystems in northern China. Full article

Research Highlights: Natural regeneration is important in pine–oak mixed forests (Pinus armandii Franch., Pinus tabuliformis Carr., and Quercus aliena Bl. var. acuteserrata Maxim.ex Wenz.), but allelopathy as a limiting factor has not been studied. Our research provides insights into allelopathy in pine–oak mixed forest litter. Background and Objectives: Allelopathy among tree species occupying the same ecological niche in mixed forests may adversely affect regeneration. We studied allelopathy in pine and oak forest litter to determine the effect on regeneration, whether it is offset by adding activated carbon or plant ash, and what allelopathic substances are present. Materials and Methods: We used laboratory seed culture and field seeding to determine pine and oak litter regeneration effects on P. tabuliformis and P. armandii in the Qinling Mountains, China. In the laboratory, we irrigated seeds with three different litter concentrations. A fourth treatment incorporated activated carbon. The field study established small quadrats in mixed forest to study how removing or retaining litter and spreading plant ash affected sown seeds. High performance liquid chromatography–mass spectrometry was used to compare differences in chemical substances in extracts with and without activated carbon. Results: Litter extracts significantly affected germination rates in both species. Seedling morphological and physiological indexes showed that litter extracts negatively affected growth in both species, but activated carbon alleviated this inhibitory effect on P. armandii. Forest stand and litter did not affect P. armandii seed germination. Pinus tabuliformis germination rates were significantly higher in plots with removed litter than when litter was retained or plant ash spread, and lower in oak than pine forest. Allelopathic substances detected in pine forest were trioctyl trimellitate, amyloid β-Peptide 10–20, and triisobutyl phosphate, potentially affecting P. armandii seed germination and growth. Conclusions: Appropriate removal of litter in mixed forests can improve the natural regeneration ability of P. tabuliformis. Full article