Wildfires have environmental, economic, and social impacts, and can shape the landscape and benefit ecosystems such as the Cerrado. This study evaluated the diversity, similarity, and floristic and structural differences of woody savanna and forest formations of the Cerrado, when affected and not affected by fire. Twenty-eight 25–400 m² plots were randomly allocated and divided into Burnt Cerrado and Unburnt Cerrado, Burnt Forest, and Unburnt Forest, and divided into three levels of inclusion according to diameter class (smaller than 2 cm, 2–5 cm and larger than 5 cm). Species were identified, DBH and height measured, and phytosociological parameters such as volume, diversity, and floristic similarity evaluated. Burnt Cerrado had lower diversity, density, and dominance at all inclusion levels compared to the Unburnt Cerrado, and showed similarities between treatments at the inclusion levels. Burnt Forest had smaller differences in diversity, density, and dominance than Unburnt Forest. Forest formation was similar at level 1 of inclusion and in the total area. However, it was dissimilar at lower levels. The lower density and diversity of species at the lowest levels of inclusion was associated with mortality from fire.

A century and a half ago, in the European part of Russia (Moscow), forest scientists established the first long-term observations of forests, many of which are under observation to the present day. In the twentieth century, climate changes and, due to industrial development, forest areas were under air pollution. Based on observations from 157 sites, this study shows that the growth and density of Scots pine (Pinus sylvestris L.) have decreased by the end of the twentieth century. The environment has changed, and the growth and development of plantations has slowed. Pine yields (− 34% stand volume) and their life expectancy (on average 50 years) have decreased. These changes are critical for forestry and for the management of forests in urban centers. Due to the decline in growth, ecosystem functions by urban forests has decreased. In order to increase the sustainability of urban forests and the provision of ecosystem services, it is preferable to create multi-species stands with a complex structure.

Spatial and environmental processes are two ecological processes that have attracted considerable attention in plant community assembly, depending on sampling scale and life history. However, the processes that determine community assembly have not been studied in the karst region of southwest China. In this study, a 25-ha (500 m × 500 m) monitoring plot within the subtropical climax forest in the karst region was established and canonical correspondence analysis was used to reveal the effects of topography and soil on the spatial patterns of tree community assembly. Our study suggests that spatial processes dominate species composition and the combined effects of spatial and environmental processes play an important role. Overall interpretation rate increases with enlarging the sampling scale. However, the pattern of variation partitioning was similar in different life stages. Environmental variables significantly affected species composition at different sampling sizes and life histories and had a higher interpretation rate of species composition on larger sampling sizes. Topographic wetness index was the most important variable to explain species composition of the environmental variables. These results suggest that it is necessary to consider the relative importance of environmental and spatial factors on community assembly to better understand, conserve, and manage subtropical karst forests.

Dead fine fuel moisture content (DFFMC) is a key factor affecting the spread of forest fires, which plays an important role in evaluation of forest fire risk. In order to achieve high-precision real-time measurement of DFFMC, this study established a long short-term memory (LSTM) network based on particle swarm optimization (PSO) algorithm as a measurement model. A multi-point surface monitoring scheme combining near-infrared measurement method and meteorological measurement method is proposed. The near-infrared spectral information of dead fine fuels and the meteorological factors in the region are processed by data fusion technology to construct a spectral-meteorological data set. The surface fine dead fuel of Mongolian oak (Quercus mongolica Fisch. ex Ledeb.), white birch (Betula platyphylla Suk.), larch (Larix gmelinii (Rupr.) Kuzen.), and Manchurian walnut (Juglans mandshurica Maxim.) in the maoershan experimental forest farm of the Northeast Forestry University were investigated. We used the PSO-LSTM model for moisture content to compare the near-infrared spectroscopy, meteorological, and spectral meteorological fusion methods. The results show that the mean absolute error of the DFFMC of the four stands by spectral meteorological fusion method were 1.1% for Mongolian oak, 1.3% for white birch, 1.4% for larch, and 1.8% for Manchurian walnut, and these values were lower than those of the near-infrared method and the meteorological method. The spectral meteorological fusion method provides a new way for high-precision measurement of moisture content of fine dead fuel.

Plantations of Rupprecht’s larch (Larix principis-rupprechtii) have been widely established in the drylands of northwest and north China under traditional fast-growing plantation management strategies. These strategies and the long-term logging ban have led to over-populated stands with lower structural and functional stability, less economic benefit and higher water consumption. To guide the sustainable management of larch plantations, field surveys and historical data compilation were undertaken in the Liupan Mountains of northwest China. The main influencing factors (stand structure and site condition) and their effects on mean tree height, mean DBH and timber volumes were determined based on up-boundary line analysis. Tree growth models coupling the effects of tree age, stand density, and elevation were established. Both height and DBH markedly increased initially and then slowly with tree age, decreased with stand density, and showed unimodal change with elevation. The coupled growth models accounted for 72–78% of the variations in tree height, DBH and timber growth. Recommendations for future plantation management are: (1) prolong the rotation to at least 60 years to produce large-diameter, high-quality timber and maintain greater carbon stocks; (2) zone the target functions of stands by elevation; and, (3) reduce stand density for balanced supply of multiple ecosystem services. The growth models developed can predict growth response of larch plantations to density alteration under given ages and elevations, and assist the transformation from traditional management for maximum timber production to site-specific and multifunctional management with longer rotations and moderate tree density.

Accurate decay detection and health assessment of trees at low temperatures is an important issue for forest management and ecology in cold areas. Low temperature ice formation on tree health assessment is unknown. Because electric resistance tomography and stress wave tomography are two widely used methods for the detection of tree decay, this study investigated the effect of ice content on trunk electrical resistance and stress wave velocity to improve tree health assessment accuracy. Moisture content, trunk electrical resistance and stress wave velocity using time domain reflectometry were carried out on Larix gmelinii and Populus simonii. Ice content is based on moisture content data. The ice content of both species showed a trend of increasing and then decreasing. This was opposite with ambient temperatures. With the decrease of temperatures, daily average ice content increased, but the range narrowed gradually and both electrical resistance and stress wave velocity increased. Both increased rapidly near 0 °C, mainly caused by ice formation (phase change and freezing of free water) in live trees. In addition, both are positively correlated with ice content. The results suggest that ice content should be considered for improving the accuracy of tree decay detection and health evaluation using electric resistance tomography and stress wave velocity methods under low temperatures.

With the expansion of eucalyptus crops to areas with severe water limitations, physiological studies involving eucalyptus clones to identify those that are tolerant to water stress become important. The objective of this study was to assess morphological and physiological responses by eucalyptus clones subjected to drought stress and rehydration. The experiment consisted of three eucalyptus clones: VC865, I224 and I144 and two water regimes: control and water stress followed by rehydration, with six replicates. Leaf water potential, gas exchange, maximum quantum efficiency of photosystem II and plant height and stem diameter were evaluated under drought stress and rehydration. After 6 d of rehydration, the number of leaves, leaf area and dry mass of root, leaf, stem and their total were evaluated. All clones showed intense reduction of gas exchange during the drought stress period, and only VC865 and I144 showed rapid recovery with 3 d of rehydration. Clone I224 showed greater reduction in height, stem diameter, number of leaves, water potential at midday (Ψ _{w Midday}), and maximum quantum efficiency of photosystem II (F _v/F _m). Clones VC865 and I144 showed lower reductions in Ψ _{w Midday} and F _v/F _m under stress. VC865 had lower reductions in leaf number, leaf area and higher leaf dry mass, while clone I144 had higher height and lower reduction in root dry mass under. Both these clones showed higher water use efficiency with 3 d of rehydration. These different phenotypic plasticities gave the clones VC865 and I144 efficient mechanisms of acclimatization to stress and more drought tolerance, enhancing their greater capacity for recovery after stress, which allowed lower dry mass reduction. Clone I224, however, was more susceptible to drought stress, undergoing greater physiological damage with only partial recovery during rehydration.

Carpinus tschonoskii Maxim. exhibits rich leaf phenotypic variation and various leaf shapes, but few studies show why leaf phenotypic traits have such a large variation. Basic morphological markers may provide guidance for studying plant genetic variation and species protection and utilization. To study leaf phenotypic variations and the relationship between variation characteristics and climatic and geographical factors, phenotypic traits among natural populations were investigated. Results revealed that leaf phenotypes varied significantly among and within populations. Some populations had higher phenotypic diversity, while others had lower phenotypic diversity. Among the phenotypic traits, leaf area and petiole length had the most variation. Leaf index and primary lateral veins were the most stable phenotypes, which may be important reference indexes for phenotype identification in field investigations. There was a strong consistency between leaf phenotypic traits and geographical location. Plants in high latitudes tend to have longer leaves, and plants in low temperatures tend to have longer leaves and larger leaf perimeter. In addition, plants in areas with less rainfall have longer petioles. The 13 populations of C. tschonoskii can be divided into four branches by cluster analysis, and the results show a good relationship with the geographical location of each population. Additionally, some populations geographically isolated also had unique leaf phenotypes.

Plant growth and productivity are negatively affected by soil salinity. This study investigated the effects of the rhizosphere-promoting bacterium, Bacillus paramycoides JYZ-SD5, and the ectomycorrhizal fungus, Schizophyllum commune Be, on the growth of Metasequoia glyptostroboides under salt stress. Changes in biomass, root growth, root ion distribution and in vivo enzyme activities were determined under different treatments (Be, JYZ-SD5, and Be + JYZ-SD5). The results show that all inoculations increased chlorophyll content, shoot length and root diameter with or without salt stress, and the effect of Be + JYZ-SD5 was the strongest. JYZ-SD5 and Be + JYZ-SD5 treatments significantly increased root length, surface area, bifurcation number, tip number, main root length and diameter under salt stress. Normal chloroplast structures developed under both single and double inoculations. Relative to the control, root activities of M. glyptostroboides in the Be, JYZ-SD5, and Be + JYZ-SD5 treatments increased by 31.3%, 17.2%, and 33.7%. All treatments increased the activities of superoxide dismutase (SOD), peroxidase (POD), Na⁺–K⁺-ATPase and Ca²⁺–Mg²⁺-ATPase. The strongest effect was by Be + JYZ-SD5. Analysis of root ion distribution showed that, under salt stress, Na⁺ and K⁺ decreased and were concentrated in the epidermis or cortex. Na/K ratios also decreased. The Be + JYZ-SD5 treatment increased betaine by 130.3% and 97.9% under 50 mM and 100 mM salt stress, respectively. Together, these changes result in the activation of physiological and biochemical processes involved in the mitigation of salinity-induced stress in M. glyptostroboides.

Sex has a significant effect on various traits among dioecious plants. In this analysis of the sex effect on the radial growth and wood density of numerous 20-year-old trees of Populus deltoides growing in a common garden, male trees performed better than the females in radial growth, but sex did not significantly affect wood density. Growth rate and wood density were weakly negatively correlated. Sex selection is also critical for controlling seed-hair pollution from P. deltoides plantations. However, because the juvenile period of P. deltoides lasts for years, a reliable technique to determine the sex of juveniles has been needed. Here we developed a marker-aided technique to discriminate the sexes of P. deltoides seedlings. This study provides essential information on target traits and a highly desirable genetic toolkit for accelerate breeding programs for this important tree species.