Clarifying the climate change effects on the radial growth of trees has implications for sustainable forest management, especially under global warming. To investigate tree growth responses to regional climate change of Xiaowutai Mountain, four Chinese pine (Pinus tabulaeformis) ring-width index chronologies were established at different elevations (1290–1600 m). Species growth trends were estimated using climate change projections derived from global climate models. The results show: (1) the four ring-width chronologies exhibited strong statistical characteristics, making them suitable for dendroclimatology studies. Radial growth-climate relationships were highly consistent, showing a negative correlation with previous September temperatures and current May–June temperatures, as well as a positively correlated with precipitation and Palmer Drought Severity Index during the corresponding period; and (2) climate change scenarios revealed that temperature will gradually increase on the Xiaowutai Mountain, and only a slight variation in precipitation is expected. Chinese pine radial growth may show a decline under future climate change.

The sap flow method is widely used to estimate forest transpiration. However, at the individual tree level it has spatiotemporal variations due to the impacts of environmental conditions and spatial relationships among trees. Therefore, an in-depth understanding of the coupling effects of these factors is important for designing sap flow measurement methods and performing accurate assessments of stand scale transpiration. This study is based on observations of sap flux density (SF_d) of nine sample trees with different Hegyi’s competition indices (HCIs), soil moisture, and meteorological conditions in a pure plantation of Larix gmelinii var. principis-rupprechtii during the 2021 growing season (May to September). A multifactorial model of sap flow was developed and possible errors in the stand scale sap flow estimates associated with sample sizes were determined using model-based predictions of sap flow. Temporal variations are controlled by vapour pressure deficit (VPD), solar radiation (R), and soil moisture, and these relationships can be described by polynomial or saturated exponential functions. Spatial (individual) differences were influenced by the HCI, as shown by the decaying power function. A simple SF_d model at the individual tree level was developed to describe the synergistic influences of VPD, R, soil moisture, and HCI. The coefficient of variations (CV) of the sap flow estimates gradually stabilized when the sample size was > 10; at least six sample trees were needed if the CV was within 10%. This study improves understanding of the mechanisms of spatiotemporal variations in sap flow at the individual tree level and provides a new methodology for determining the optimal sample size for sap flow measurements.

In the context of ongoing climate change, relationships between tree growth and climate present uncertainties, which limits the predictions of future forest dynamics. Northwest China is a region undergoing notable warming and increased precipitation; how forests in this region will respond to climate change has not been fully understood. We used dendrochronological methods to examine the relationship between climate and the radial growth of four tree species in a riparian forest habitat in Altai region: European aspen (Populus tremula), bitter poplar (Populus laurifolia), Swedish birch (Betula pendula), and Siberian spruce (Picea obovata). The results reveal that European aspen was insensitive to climate changes. In contrast, bitter poplar showed a positive response to elevated temperatures and negative to increased moisture during the growing season. Swedish birch and Siberian spruce were adversely affected by higher temperatures but benefited from increased precipitation. A moving correlation analysis suggested that, against a backdrop of continuous warming, growth patterns of these species will diverge: European aspen will require close monitoring, bitter poplar may likely to show accelerated growth, and the growth of Swedish birch and Siberian spruce may be inhibited, leading to a decline. These findings offer insight into the future dynamics of riparian forests under changing climate.

Investing in projects that support environmental benefits, such as tree harvesting, has the potential to reduce air pollution levels in the atmosphere in the future. However, this kind of investment may increase the current level of emissions. Therefore, it is necessary to estimate how much the policy affects the current level of CO₂ emissions. This makes sure the policy doesn’t increase the level of CO₂ emissions. This study aims to analyze the effect of the One Billion Trees program on CO₂ emissions in New Zealand by employing the 2020 input–output table analysis. This investigation examines the direct and indirect effects of policy on both the demand and supply sides across six regions of New Zealand. The results of this study for the first year of plantation suggest that the policy increases the level of CO₂ emissions in all regions, especially in the Waikato region. The direct and indirect impact of the policy leads to 64 kt of CO₂ emissions on the demand side and 270 kt of CO₂ emissions on the supply side. These lead to 0.19 and 0.74% of total CO₂ emissions being attributed to investment shocks. Continuing the policy is recommended, as it has a low effect on CO₂ emissions. However, it is crucial to prioritize the use of low-carbon machinery that uses fossil fuels during the plantation process.

In recent decades, the rapid climate warming in polar and alpine regions has been accompanied by an expansion of shrub vegetation. However, little is known about how changes in shrub distribution will change as the distribution of tree species and snow cover changes as temperatures rise. In this work, we analyzed the main environmental factors influencing the distribution and structure of Juniperus sibirica, the most common shrub species in the Southern Ural Mountains. Using mapping and digital elevation models, we demonstrated that J. sibirica forms a well-defined vegetation belt mainly between 1100 and 1400 m a.s.l. Within this zone, the abundance and cover of J. sibirica are influenced by factors such as rockiness, slope steepness, water regime and tree (Picea obovata) cover. An analysis of data spanning the past 9 years revealed an upward shift in the distribution of J. sibirica with a decrease in its area. The primary limiting factors for the distribution of J. sibirica were the removal of snow cover by strong winter winds and competition with trees. As a consequence of climatic changes, the tree line and forest limit have shifted upward, further restricting the distribution of J. sibirica to higher elevations where competition for light with trees is reduced and snow cover is sufficiently deep.

Forest ecosystems within national parks are threatened by various biotic and abiotic factors. To determine the causes of the desiccation and death of trees in mixed coniferous and deciduous forests of Tara National Park (TNP), Serbia, we monitored defoliation and mortality of individual trees in permanent experimental plots. Data on the desiccation of a large number of trees were gathered by determining the total volume of dry trees and areas of forests under drying stress. The two sets of data were combined to determine the impact of climatic events, primarily drought periods, on the desiccation of forests. Combining data from the International Co-operative Program on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) with TNP data helped relate forest desiccation to climate events. Key climate signals were identified by monitoring tree defoliation changes in two permanent experimental plots, and then assessed for their influence on tree desiccation in the entire national park. The standardized precipitation evapotranspiration index (SPEI) was used for a more detailed analysis of the drought period. Despite the lack of climate data for a certain period, the SPEI index revealed a link between climate variables and the defoliation and desiccation of forests. Furthermore, the desiccation of trees was preceded by a long drought period. Although mixed coniferous-deciduous forests are often considered less vulnerable to natural influences, this study suggests that forest ecosystems can become vulnerable regardless of tree species composition due to multi-year droughts. These findings contribute to a better understanding of important clues for predicting possible future desiccation of forests. Continuous monitoring of the state of forests and of more permanent experimental plots in national parks could provide better quality data and timely responses to stressful situations.

Rapid increase in desertification is an environmental concern, especially for the health and sustainability of ecosystems in changing climates. How ecosystems respond to such changes may be partially understood by studying interactions and performance of critically important groups such as soil fungi functional groups. This study investigated variations in diversities of three soil fungi functional guilds (saprotrophic, symbiotic, pathogenic) and influencing abiotic factors in a Pinus densata forest on the southeast Tibetan Plateau where desertification is intense. The results indicate desertification significantly decreased the proportion of dominant fungal guild-symbiotic fungi (mean relative abundance decreasing from 97.0% to 68.3%), in contrast to saprotrophic fungi (increasing from 2.7% to 25.7%) and pathogenic (from 0.3% to 5.9%). Soil pH had the most significant impact on fungal community structure and negatively correlated with symbiotic fungal richness, which was significantly lower in arid soils, and positively correlated with saprotrophic and pathogenic fungal alpha-diversity, which were abundant. Different community structures and regulators of the three fungi communities were observed, with pH, total phosphorus and ammonium (NH₄⁺) as the main determinants. This study links the biotic and abiotic components during desertification and the interactions between them, and may be used as indicators of ecosystem health and for amendments to mitigate the effects of a changing climate.

The use of mobile laser scanning to survey forest ecosystems is a promising, scalable technology to describe forest 3D structures at high resolution. To confirm the consistency in the retrieval of forest structural parameters using hand-held laser scanning (HLS), before operationalizing the method, confirming the data is crucial. We analyzed the performance of tree-level mapping based on HLS under different phenology conditions on a mixed forest in western Spain comprising Pinus pinaster and two deciduous species, Alnus glutinosa and Quercus pyrenaica. The area was surveyed twice during the growing season (July 2022) and once in the deciduous season (February 2022) using several scanning paths. Ground reference data (418 trees, 15 snags) was used to calibrate the HLS data and to assess the influence of phenology when converting 3D data into tree-level attributes (DBH, height and volume). The HLS-based workflow was robust at isolating tree positions and recognizing stems despite changes in phenology. Ninety-six percent of all pairs matched below 65 cm. For DBH, phenology barely altered estimates. We observed a strong agreement when comparing HLS-based tree height distributions. The values exceeded 2 m when comparing height measurements, confirming height data should be carefully used as reference in remote sensing-based inventories, especially for deciduous species. Tree volume was more precise for pines (r = 0.95, and relative RMSE = 21.3 –23.8%) compared to deciduous species (r = 0.91 –0.96, and relative RMSE = 27.3–30.5%). HLS data and the forest structural complexity tool performed remarkably, especially in tree positioning considering mixed forests and mixed phenology conditions.

Unstable environments intensify the frequency of extreme disasters. Long-term climate changes can lead to agricultural and ecological degradation that threatens population sustainability. To better understand past climatic events and consequences, here we present a reconstruction of the self-calibrating Palmer drought severity index (scPDSI) from September to August for the desert margins of northern China, dating back to 1742. The reconstruction accounts for 42.9% of the variation of meteorological data between 1951 and 2020. Our spatial correlation analyses showed significant correlations between scPDSI, runoff, and precipitation. Over the past 279 years, the study area has undergone nine dry and eight wet periods, with the most severe climate extremes between the 1850s and 1890s. This period of prolonged drought in northeastern China coincided with the combined impacts of climatic factors and human influences, contributing to the fall of the Qing Dynasty. Analysis of periodicity and anomalies in sea surface temperatures indicate a strong association between wet and dry cycles and El Niño-Southern Oscillations. Our findings offer insights into long-term dry and wet fluctuations at the desert margins in northern China and elucidate the relationship between drought and the dynamics of civilizations. They also highlight the potential impact of extremes in climate on modern society, especially under the four projected shared socioeconomic pathways climatic scenarios, which predict worsening droughts in northern China.

Forest disturbances at gap levels are one of the most important events for the regeneration and establishment of intermediate tree species. Abrupt canopy openings expose plants to high light intensity and high evaporative demands that stress shade-acclimated plants. Later, the slow closure of gaps reduces light availability to plants established when the incident irradiation was higher. This work evaluated the morphological and physiological acclimation of Cabralea canjerana (Vell) Mart. regeneration to sudden and to gradual changes in canopy cover. A pot experiment was carried out with plants exposed to a sudden opening. A few days after the light shock, plants rapidly increased photosynthetic rates and decreased leaf water potential. After two months, plants activated physiological responses at leaf and whole plant levels to high light and water stresses, e.g., increased stomatal conductance, stomatal index and reduction of leaf: fine roots ratio and chlorophyll. After seven months, hydraulic conductivity of petioles and the whole leaf increased, and growth was much higher than plants that remained under the canopy. In a field experiment in gaps in the rainforest, plants acclimated to all canopy covers. Seven years after planting, growth was maximum in open environments within the gaps, even if the canopy closed during the first 20 months after planting. In conclusion, if this species is planted to enrich the rainforest, positions within gaps with lower canopy cover should be chosen and gap closure will not affect growth. To manage C. canjerana natural regeneration, the opening of gaps and removal of understory will increase survival and growth without the risk that the stress caused by these sudden openings could lead to the death of seedlings. Combining pot and field experiments helps to understand the autecology of trees with particular ecological interest, and to build sound restoration practices.

Different chemical compositions of soil organic carbon (SOC) affect its persistence and whether it significantly differs between natural forests and plantations remains unclear. By synthesizing 234 observations of SOC chemical compositions, we evaluated global patterns of concentration, individual chemical composition (alkyl C, O-alkyl C, aromatic C, and carbonyl C), and their distribution evenness. Our results indicate a notably higher SOC, a markedly larger proportion of recalcitrant alkyl C, and lower easily decomposed carbonyl C proportion in natural forests. However, SOC chemical compositions were appreciably more evenly distributed in plantations. Based on the assumed conceptual index of SOC chemical composition evenness, we deduced that, compared to natural forests, plantations may have higher possible resistance to SOC decomposition under disturbances. In tropical regions, SOC levels, recalcitrant SOC chemical composition, and their distributed evenness were significantly higher in natural forests, indicating that SOC has higher chemical stability and possible resistance to decomposition. Climate factors had minor effects on alkyl C in forests globally, while they notably affected SOC chemical composition in tropical forests. This could contribute to the differences in chemical compositions and their distributed evenness between plantations and natural stands.

As an important material for manufacturing resonant components of musical instruments, Paulownia has an important influence on the sound quality of Ruan. In this paper, a model for evaluating the sound quality of Ruan based on the vibration characteristics of wood is developed using machine learning methods. Generally, the selection of materials for Ruan manufacturing relies primarily on manually weighing, observing, striking, and listening by the instrument technician. Deficiencies in scientific theory have hindered the quality of the finished Ruan. In this study, nine Ruans were manufactured, and a prediction model of Ruan sound quality was proposed based on the raw material information of Ruans. Out of a total of 180 data sets, 145 and 45 sets were chosen for training and validation, respectively. In this paper, typical correlation analysis was used to determine the correlation between two single indicators in two adjacent pairwise combinations of the measured objects in each stage of the production process in Ruan. The vibration characteristics of the wood were tested, and a model for predicting the evaluation of Ruan’s acoustic qualities was developed by measuring the vibration characteristics of the resonating plate material. The acoustic quality of the Ruan sound board wood was evaluated and predicted using machine learning model generalized regression neural network. The results show that the prediction of Ruan sound quality can be achieved using Matlab simulation based on the vibration characteristics of the soundboard wood. When the model-predicted values were compared with the traditional predicted results, it was found that the generalized regression neural network had good performance, achieving an accuracy of 93.8% which was highly consistent with the experimental results. It was concluded that the model can accurately predict the acoustic quality of the Ruan based on the vibration performance of the soundboards.

Trees progress through various growth stages, each marked by specific responses and adaptation strategies to environmental conditions. Despite the importance of age-related growth responses on overall forest health and management policies, limited knowledge exists regarding age-related effects on dendroclimatic relationships in key subtropical tree species. In this study, we employed a dendrochronological method to examine the impact of rapid warming on growth dynamics and climatic sensitivity of young (40–60 years) and old (100–180 years) Pinus massoniana forests across six sites in central-southern China. The normalized log basal area increment of trees in both age groups increased significantly following rapid warming in 1984. Trees in young forests further showed a distinct growth decline during a prolonged severe drought (2004–2013), whereas those in old forests maintained growth increases. Tree growth was more strongly influenced by temperature than by moisture, particularly in old forests. Spring temperatures strongly and positively impacted the growth of old trees but had a weaker effect on young ones. Old forests had a significantly lower resistance to extreme drought but faster recovery compared to young forests. The “divergence problem” was more pronounced in younger forests due to their heightened sensitivity to warming-induced drought and heat stress. With ongoing warming, young forests also may initially experience a growth decline due to their heightened sensitivity to winter drought. Our findings underscore the importance of considering age-dependent changes in forest/tree growth response to warming in subtropical forest management, particularly in the context of achieving “Carbon Peak & Carbon Neutrality” goals in China.