Search Results (10)

Mongolian pine (Pinus sylvestris var. Mongolia) has been widely utilized as a key species for afforestation projects within the Three-North Shelterbelt of Liaoning Province in China. Its impressive ecological resilience has made it a favorite choice for this endeavor. However, as the stands mature and climate conditions shift, some areas are experiencing premature decline or even mortality. Ecological stoichiometry is capable of uncovering the supply and equilibrium of plant and soil nutrients within ecosystems and is extensively utilized in the identification of limiting elements. Therefore, studying its ecological stoichiometry and internal stability dynamics is of crucial significance for clarifying the nutrient cycling process in the Mongolian pine region and alleviating the decline situation. The eastern and northwestern regions of Liaoning differ significantly in precipitation and soil nutrient availability. This study examines Mongolian pine plantations in both regions, analyzing the carbon (C), nitrogen (N), and phosphorus (P) content in plant tissues, soil, microbial biomass, and stoichiometric ratio under distinct environmental conditions. In order to provide a theoretical basis for alleviating the decline of artificial poplar forests and healthy management. Results indicate that (1) leaf C, N, and P contents in the eastern Liaoning region averaged 496.67, 15.19, and 1.66 g·kg⁻¹, respectively, whereas those in northwestern Liaoning were 514.16, 14.82, and 1.23 g·kg⁻¹, respectively. Soil C, N, and P concentrations exhibited notable regional differences, with eastern Liaoning recording 34.54, 2.62, and 0.48 g·kg⁻¹, compared to significantly lower values in northwestern Liaoning (7.74, 0.77, and 0.21 g·kg⁻¹). Similarly, microbial biomass C, N, and P were higher in eastern Liaoning (18.63, 5.09, and 7.72 mg·kg⁻¹) than in northwestern Liaoning (10.18, 3.46, and 4.38 mg·kg⁻¹). (2) The stoichiometric ratio of soil in the Mongolian pine plantations is higher than that in northwestern Liaoning, but the stoichiometric ratio of plants shows the opposite trend. Specifically, microbial carbon-to-nitrogen (MBC/MBN) ratios are higher in eastern Liaoning, whereas microbial carbon-to-phosphorus (MBC/MBP) and nitrogen-to-phosphorus (MBN/MBP) ratios are greater in northwestern Liaoning. Correlation analysis of plant–soil–microbe stoichiometry indicates that plant growth in both regions is co-limited by nitrogen, with Mongolian pine exhibiting strong internal stability. Full article

Afforestation has been considered to be the cost-effective way to sequestrate carbon (C) dioxide from the atmosphere in the soils, while concurrent responses of soil inorganic C (SIC) and soil organic C (SOC), and their turnover are still not well-defined. During the C cycle, inorganic C is enriched in heavy isotopes (¹³C), while organic C, due to photosynthetic fractionation, is enriched in light isotopes (¹²C). This leads to distinct C isotope fractionation in terrestrial ecosystems. In this study, 72 paired soils (0–20 cm) from poplar shelterbelts and adjacent farmland sites were collected in six regions (Zhaozhou, Fuyu, Dumeng, Zhaodong, Lanling, and Mingshui) of northeastern China. Five soil fractions of dissolved organic C (DOC), particulate organic matter (POM), sand and stable aggregates (S + A), silt and clay (S + C), and resistant SOC (rSOC) and bulk soils were used in C content assay and the natural δ¹³C determination. The results showed that, compared with SOC, poplar shelterbelts resulted in SIC accrual in the soils across all six sites; however, only half of the six sites showed SOC accrual, indicating an ambiguous effect of afforestation on SOC. The natural δ¹³C method could identify the SOC turnover owing to the C isotopic discrimination. The δ¹³C–SOC-derived turnover ratio was 23%. When SIC was included in the δ¹³C measurement, bulk soils and four soil fractions (S + C, S + A, rSOC, DOC) showed a 2%–10% lower turnover percentage than the δ¹³C–SOC-derived turnover ratios. The SIC inclusion resulted in the dependency of δ¹³C–TC (TC = SIC + SOC) values on SOC (negative, R²: 0.21–0.44) and SIC content (positive, R²: 0.39–0.63). By contrast, when SIC was excluded, the δ¹³C–SOC values were independent of them (R² < 0.18). Redundancy ordination analysis manifested that more SOC in the soils, together with more POM and farming uses would be accompanied with the lower δ¹³C values. Moreover, forest characteristics (e.g., age and density) and farmland backgrounds (e.g., crop history and distance between forest and farmland) could explain differences in δ¹³C-related features. Our results highlighted that SIC in natural δ¹³C determination underestimated the C turnover ratio in general. However, SIC storage should be included in the soil C sequestration evaluation owing to a general SIC accrual pattern across regions when compared with those of SOC. Full article

Sustainable forest management faces challenges from various biotic and abiotic stresses. The Asian longhorned beetle (ALB) and drought stress both induce water shortages in poplar trees, but require different management strategies. In northwestern China, ALB and drought stress caused massive mortality in poplar shelterbelts, which seriously affected the ecological functions of poplars. Developing a large-scale detection method for discriminating them is crucial for applying targeted management. This study integrated UAV-hyperspectral and LiDAR data to distinguish between ALB and drought stress in poplars of China’s Three-North Shelterbelt. These data were analyzed using a Partial Least Squares-Support Vector Machine (PLS-SVM). The results showed that the LiDAR metric (elev_sqrt_mean_sq) was key in detecting drought, while the hyperspectral band (R970) was key in ALB detection, underscoring the necessity of integrating both sensors. Detection of ALB in poplars improved when the poplars were well watered. The classification accuracy was 94.85% for distinguishing well-watered from water-deficient trees, and 80.81% for detecting ALB damage. Overall classification accuracy was 78.79% when classifying four stress types: healthy, only ALB affected, only drought affected, and combined stress of ALB and drought. The results demonstrate the effectiveness of UAV-hyperspectral and LiDAR data in distinguishing ALB and drought stress in poplar forests, which contribute to apply targeted treatments based on the specific stress in poplars in northwest China. Full article

The concentrations of exogenous nitrogen and calcium can significantly regulate plant growth and photosynthesis and mutually affect their absorption and utilization. However, whether there is an optimal nitrogen–calcium ratio (N:Ca ratio) in poplar seedling growth and physiological adaptation and what the mechanism of changes in the transcriptome is remain unclear. In this study, three different N:Ca ratios were used to grow poplar seedlings, and physiological and transcriptomic methods were used to study the molecular mechanisms of poplar growth under nitrogen–calcium synergy and to determine the optimal N:Ca ratio for poplar seedling growth. The results of this study showed that maximum poplar seedling growth occurred in the treatment with an N:Ca ratio of 2, which resulted in significantly greater induction of growth than the two other treatments (p < 0.05). Under the lowest N:Ca ratio, poplar seedlings can ensure normal development by regulating photosynthesis, while under the highest N:Ca ratio, regulating nitrogen metabolism can achieve the same result. These results contribute to a better understanding of the molecular mechanisms by which poplar seedlings respond to different ratios of N:Ca. This study provides a valuable basis for exploring the synergistic effects of nitrogen and calcium on the growth of poplar shelterbelts. Full article

Poplar is an important shelterbelt, timber stand, and city tree species that has been the focus of forestry research. The regulatory role of the long non-coding RNA molecule (lncRNA; length > 200 nt) has been a research hotspot in plants. In this study, seedlings of 741 poplar were irradiated with LED blue and white light, and the Illumina HiSeq 2000 sequencing platform was used to identify lncRNAs. |logFC| > 1 and p < 0.05 were considered to indicate differentially expressed lncRNAs, and nine differentially expressed lncRNAs were screened, the target genes of which were predicted, and three functionally annotated target genes were obtained. The differentially expressed lncRNAs were identified as miRNA targets. Six lncRNAs were determined to be target sites for twelve mRNAs in six miRNA families. LncRNAs and their target genes, including lncRNA MSTRG.20413.1-ptc-miR396e-5p-GRF9, were verified using quantitative real-time polymerase chain reaction analysis, and the expression patterns were analyzed. The analysis showed that the ptc-miR396e-5p expression was downregulated, while lncRNA MSTRG.20413.1 and GRF9 expression was upregulated, after blue light exposure. These results indicate that lncRNAs interact with miRNAs to regulate gene expression and affect plant growth and development. Full article

As one of the world’s largest ecological rehabilitation programs, the three-north (Northern China, Northeastern China, and Northwestern China) shelterbelts program in China were not well evaluated on its effects on multiple soil properties. This paper aims to quantify this. Seven hundred twenty soils from paired plots of farmlands and neighbor shelterbelts were sampled from six regions of Songnen Plain in northeastern China. Multivariate analysis of variance and regression analysis were used to detect the impacts of shelterbelt plantations. For the overall 1 m soil profiles, shelterbelt plantations had a 4.3% and 7.4% decreases in soil bulk density and soil moisture (p = 0.000), a 4.8% increase in soil porosity (p = 0.003). It also evidently recovered soil fertility with a 40% increase in total P, a 4.4% increase in total K, and a 15.1% increase in available K (p < 0.05). However, without overall changes were in SOC and N (p > 0.05). Compared with farmland, shelterbelt plantations produced a 7.8% SOC increase in 20–40 cm soil and much more minor changes in surface soil (0–20 cm). Compared with the younger plantation, mature shelterbelts tended to sequestrate more SOC in soils (from a 0.11% decrease to a 3.31% increase) and recover total K from a 2.24% decline to a 16.5% increase. Correlation analysis manifested that there is a significant relationship between SOC sequestration and the changes in bulk density, porosity, soil moisture, pH, EC, total N, total P, and alkaline hydrolyzed N. In contrast, the strongest relationship was observed between total N and SOC (r > 0.50, p < 0.001). The increase in total N was accompanied by 1.01–1.67-fold higher SOC sequestration in deep soils >20 cm in poplar forests. Our results highlight that the over-40-year shelterbelts afforestation on farmland in northeastern China could strongly affect soil physics, soil water, and nutrient of P and K. The effects on SOC sequestration were dependent on soil depths, growth stages, and regions. Our data support the precise soil evaluation of agroforestry projects in the black soil region in the high-latitude northern hemisphere. Full article

This study aimed to determine the distribution, stability, and soil organic carbon (SOC) of aggregates, and the contribution of soil aggregate proportion, stability index, and aggregate-associated SOC to the total SOC. Three hundred and sixty soil samples were gathered from shelterbelts and neighboring farmlands in five layers of 1 m profiles in Songnen Plain, northeastern China. The shelterbelt plantations were found to increase by 69.5% and 103.8% in >2 mm and 0.25–2 mm soil aggregates, respectively, and their R_0.25, mean weight diameter (MWD), and geometric mean diameter (GMD) were enhanced by 96.3%, 33.2%, and 40.0%, respectively, compared to those of farmlands in soil layers at 0–20 cm depth (p < 0.05). The total SOC content increased by 13.3% at 0–20 cm soil depth, and the SOC content and stock in >2 mm aggregates increased by 21.5% and 18.7% in the 20–40 cm layer (p < 0.05), respectively. The SOC content and stock in total soil had a significantly positive relationship with the proportion of >2 mm soil aggregates and a negative relationship with the value of fractal dimension (D). The enhancement in the SOC of the total soil was dependent on the increase in aggregate-associated SOC, with larger-particle aggregates having a greater contribution. Based on the study results, afforestation improved soil stability and the structure of soil aggregates, and SOC accumulation in the total soil was not only governed by SOC concentration and stock within the aggregate size class, but also the proportion of >2 mm soil aggregates and the value of the fractal dimension. Full article

Windbreaks or shelterbelts are a management tool to protect crops from damaging horizontal wind flow, and may provide a useful buffer between farmland and urbanized areas by reducing pesticide drift, dust, and noise associated with farming activities. Plant selection for windbreaks in the Intermountain West can be difficult as high elevation coupled with extreme temperatures, high pH soils, and limited access to water are common. This study assessed eight tree species for suitability as a windbreak in the Intermountain West, with a particular focus on initial establishment and use at the urban–agriculture interface. Species were assessed for mortality, size, canopy density, insect and disease issues, and initial cost. Measurements of shadow characteristics were used as a novel approach to compare canopy density and porosity. Standard poplar (Populus x canadensis) and ‘Theves’ columnar poplar (Populus nigra ‘Afghanica’) were the most effective at rapid establishment, but species with more moderate growth rates, such as aspen, juniper, and hackberry, may provide lower long-term maintenance costs for the environmental conditions found in the Intermountain West. Full article

The Three-North Shelter Forest (TNSF) is a critical ecological barrier against sandstorms in northern China, but has shown extensive decline and death in Populus simonii Carr. in the last decade. We investigated the characteristics—tree-ring width, basal area increment (BAI), carbon isotope signature (¹³C_cor), and intrinsic water-use efficiency (iWUE)—of now-dead, dieback, and non-dieback trees in TNSF shelterbelts of Zhangbei County. Results from the three groups were compared to understand the long-term process of preceding drought-induced death and to identify potential early-warning proxies of drought-triggered damage. The diameter at breast height (DBH) was found to decrease with the severity of dieback, showing an inverse relationship. In all three groups, both tree-ring width and BAI showed quadratic relationships with age, and peaks earlier in the now-dead and dieback groups than in the non-dieback group. The tree-ring width and BAI became significantly lower in the now-dead and dieback groups than in the non-dieback group from 17 to 26 years before death, thus, these parameters can serve as early-warning signals for future drought-induced death. The now-dead and dieback groups had significantly higher δ¹³C_cor and iWUEs than the non-dieback group at 7–16 years prior to the mortality, indicating a more conservative water-use strategy under drought stress compared with non-dieback trees, possibly at the cost of canopy defoliation and long-term shoot dieback. The iWUE became significantly higher in the now-dead group than in the dieback group at 0–7 years before death, about 10 years later than the divergence of BAI. After the iWUE became significantly different among the groups, the now-dead trees showed lower growth and died over the next few years. This indicates that, for the TNSF shelterbelts studied, an abrupt iWUE increase can be used as a warning signal for acceleration of impending drought-induced tree death. In general, we found that long-term drought decreased growth and increased iWUE of poplar tree. Successive droughts could drive dieback and now-dead trees to their physiological limits of drought tolerance, potentially leading to decline and mortality episodes. Full article

Cities at the fringe of the Taklimakan desert in NW China are prone to dust and sand storms with serious consequences for human well-being. The Kökyar Protection Forest was established in the 1980s as an ecological engineering project with the intent of protecting the city of Aksu, NW China, from these impacts. It is designed as a combination of poplar shelterbelts and orchards, irrigated by river water from the Aksu River, the main tributary of the Tarim River. Prevalent literature describes it as an afforestation project for combatting desertification with manifold positive effects for the economic, social, and environmental dimension of sustainable development. This paper sets out to challenge these claims by a sustainability assessment in which the plantation is examined from a broader perspective, embedding it to the wider context of social and environmental problems in South Xinjiang. Methods comprise evapotranspiration calculations, interviews, a socioeconomic household survey, stakeholder dialogues, and literature research. Results affirm its economic sustainability, but see a mixed record for the social sphere. From the nature conservation point of view, it has to be classified as unsustainable because its high irrigation water consumption results in the downstream desiccation and desertification of natural riparian forests along the Tarim River, causing a forest loss in the downstream area twice the size of the forest gain in the upstream area. There is a trade-off between artificial shelterbelt plantations for urban ecosystem services on the one hand side, and natural riparian forests and their biodiversity on the other hand side. The paper recommends restricting agricultural extension, and using locally adapted less water consuming agroforestry schemes to protect urban dwellers from dust stress. Full article