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Data Availability: Data will be made available on request. Lignocellulosic material is a natural renewable resource and can provide great potential in bioconversion and bioenergy production. This work studied the bioconversion processes of Pinus yunnanensis with white and brown rot fungi treatment, namely T. versicolor, G. trabeum and R. placenta, aiming to clarify the mechanism of enzymatic process and fungi’s intrinsic selectivity in fungal pretreatment during various conversion stages. The results showed that fungi achieved the decomposition and conversion of biomass through the generation of enzymes as well as their action within wood. White rot fungus T. versicolor caused simultaneous rot, which the bioconversion of wood main components occurred uniformly. Brown rot fungi exhibited the ability to depolymerize carbohydrate but degraded polysaccharides with their own bioconversion pathway, and as such caused different conversion of wood chemical components. Morphology observation proved that both white and brown rot fungal pretreatments increased the porosity and improved the accessibility of wood cells. Three kinds of fungi possess the ability to improve the digestibility, but with various situations of the substrate loss. In addition, these three fungi presented their promising potentials in different aspects as well. The research outcomes could provide insight into the mechanism of enzymatic process and role of fungal selectivity on Pinus yunnanensis bioconversion as well as the potential application of fungal pretreatment in future biorefineries and biochemical productions. Regional Project of National Natural Science Foundation of China (31860186, 32260362, 31360157); Joint project of Yunnan Agricultural Basic Research (202101BD070001-058); 111 Project (D21027).

Vegetation in hot and arid valleys is a crucial indicator of ecosystem health, but is vulnerable to human activities and environmental change. Using the Longkaikou Reservoir in the Jinsha River in southwestern China as a case study, we developed a spatially explicit model that combined the plant growth, fruiting, seed dispersal, and seed germination stages to reveal the potential impact of multiple human activities (reservoir construction, logging, grazing, and aerial seeding) on the vegetation dynamics of Dodonaea viscosa and Pinus yunnanensis. After reservoir construction, the grassland area of 68 km2 in 2003 decreased to 24 km2 in 2018, replaced by forest, shrubland, and bodies of water, and the precipitation increased during the dry season, which indicated the improvement of the local plant and soil environment. Our model predicted that when soil moisture decreased by more than 20% compared to current levels, the area of D. viscosa increased greatly at low elevations; however, when at higher soil moisture, P. yunnanensis would occupy more of the study area. Logging and grazing would slightly change the spatial pattern of vegetation and delay P. yunnanensis communities from achieving stability by directly reducing plant biomass. Countermeasures such as aerial seeding would increase the total area by 13.13 km2 and 8.09 km2 of two plants, respectively, and accelerate the stabilization of plant communities. The effects of multiple human activities on vegetation may counteract each other; for example, logging decreased the P. yunnanensis area whereas aerial seeding increased it, and plant biomass changed in response to this pressure. Given the complex relationships between vegetation and human impacts, our study provides a scientific basis for vegetation restoration and ecological security in this hot and arid valley.

The core collection construction strategies are critical for the conservation and utilization of germplasm resources. The combined data of phenotypic characteristics and SRAP markers in 780 samples were employed to construct a core collection for Pinus yunnanensis Franch. Based on geographical distribution, a total of four P. yunnanensis germplasm subsets were configured by improving a least distance stepwise sampling method at four sampling proportions. The representativeness of germplasm subsets for original germplasms were evaluated by quantitative and qualitative trait independence tests. For the quantitative traits test, the germplasm subset at a 30% sampling proportion was the best of four germplasm subsets by the mean t-test, the variance F-test, the frequency distribution χ2-test, the Shannon diversity index, and five effective evaluation parameters. For the qualitative traits test, there were significant differences between the original germplasm and germplasm subset at a 10% sampling proportion in the mean t-test of genetic diversity indicators. The genetic diversity within the population was significantly different between the original germplasm and germplasm subsets at 20% and 10% sampling proportions, respectively, in the variance F-test. The results of quantitative and qualitative traits tests revealed that the 30% sampling proportion was appropriate for the construction of the core collection.

We evaluated a novel and non-destructive method of the electrical impedance spectroscopy (EIS) to elucidate the genetic and evolutionary relationship of homoploid hybrid conifer of Pinus densata (P.d) and its parental species Pinus tabuliformis (P.t) and Pinus yunnanensis (P.y), as well as the artificial hybrids of the P.t and P.y. Field common garden tests of96 trees sampled from 760 seedlings and 480 EIS records of 1,440 needles assessed the interspecific variation of the P.d, P.t, P.y and the artificial hybrids. We found that (1) EIS at different frequencies diverged significantly among germplasms; P.y was the highest, P.t was the lowest, and their artificial hybrids were within the range of P.t and P.y; (2) maternal species effect of EIS magnitudes in the hybrids and P.d was stronger than the paternal species characteristics; (3)EIS of the artificial hybrid confirmed the mid-parent and partial maternal species characteristics;(4) unified exponential model of EIS for the interspecific and hybrids can be constructed as |Z|=Af -B; (5) cluster analysis for species and hybrid combinations in total corroborated with the previous hybrid model of Pinus densata. Our non-destructive EIS method complemented the previous finding that Pinus densata was originated from P.t and P.y. We conclude that the impedance would be a viable indicator to investigate the interspecific genetic variations of conifers.

Nutrient limitation changed from N–P co-limitation in the native shrubs to N limitation in the plantations. Element stoichiometry is a powerful tool to examine plant–soil nutrient feedbacks. In karst ecosystems, southwest China, afforestation has been widely adopted to restore soil fertility and enhance ecosystem functioning under degraded native shrub stands. However, it is unclear whether and how multiple-element stoichiometry of plants in afforested forests would differ from the native shrub community. We investigated the concentrations of C, N, S, P, K, Ca, Mg, Na, Fe, Al, Cu, Zn, and Mn in leaves and soils in native shrub community and three plantations (Pinus yunnanensis, Alnus japonica, and Platycladus orientalis). We found (1) There was significant discrimination in leaf elemental compositions between native shrub community and plantations in the karst region, southwest China. Native shrubs had lower leaf N, P, S and higher C, Ca, and Mg concentrations, as well as C:P and N:P ratios, compared to plantations; (2) For different plant species, grasses had higher P, K, and Na and lower C:P and N:K, compared to trees and shrubs; (3) N:P, K and S concentrations differed most between the native shrubs and plantations; (4) N:P in native shrubs was close to 12 while decreased to 11.3, 10.2 and 9.7 in three plantations. These results suggest that plantations strongly changed the elemental stoichiometry of native shrub communities in the karst region. N:P, Ca:Mg, K and S are key indicators for plant nutrient status in the study area. P limitation alleviates in plantations compared to native shrubs. Our study could be used to guide reforestation and improve ecosystem functioning in the karst region, Southwest China.

The distribution of the bark procyanidin contents in 26 populations of Pinus yunnanensis and 8 populations of P. kesiya var. langbianensis and 5 populations of P. densata was determined. The results indicated that genetic and environmental factors commonly affected the procyanidin content in the populations of P. yunnanensis and related species. The procyanidin contents in the three related species followed the order of P. densata (54.72 mg/g) > P. kesiya (43.86 mg/g) > P. yunnanensis (37.95 mg/g). Furthermore, the procyanidin content in P. yunnanensis and related species had high variability. The procyanidin contents in the three related species showed that the procyanidin contents of P. densata distributed in northwest Yunnan and P. kesiya distributed in southern Yunnan were high, the procyanidin content of the population with introgression and hybridization or a heterogeneous habitat was also high, and that of P. yunnanensis distributed in central Yunnan was low. The quadratic regression model of procyanidin content and latitude was Y = 1329.06 -100.52* Latitude +1.95 * Latitude2.

We employed capacitance to evaluate the kinship and interspecific variation of homoploid hybrid conifer Pinus densata, P. tabuliformis, P. yunnanensis and artificial hybrids of P. tabuliformis (maternal parent) and P. yunnanensis (paternal parent) which were cultivated and selected in the common garden experiment. By measuring capacitance spectra under different voltage frequencies, we could differentiate different germplasms based on the electrical response. We aims to demonstrate that P. densata as the hybrid of P. tabuliformis and P. yunnanensis based on the capacitance values of the species, and to provide new evidence to the previously known biological evidence, as well as and the parental effect on the hybrids. Our results revealed that capacitance values between the species are significantly different in the spectra where P. yunnanensis positioned at the lowest and P. densata was much higher than all other species, indicating that P. densata had possessed a great capacity to store electrical energy. The capacitance spectra of P. densata and the artificial hybrid are not similar, which rejected our hypothesis. Both of the capacitance values of P. densata and the hybrids were closer to P. tabuliformis than to P. yunnanensis, which shows that the maternal influence was stronger than the paternal influence. Correlation analysis on the relationship between capacitance and fitnessrelated characteristics showed that capacitance is negatively correlated to mortality rate, and positively correlated with second-year survival rate. High capacitance values of P. densata and some of the hybrids reveal their superior adaptability to harsh environment in the Tibet Plateau. We concluded that capacitance as a new indicator for plant fitness and evolution evidence of homoploid hybrid conifers.

The canopy of subtropical natural forests usually consists of several co-dominant populations (CDPs), which play a crucial role in forest structure, formation of the forest environment, and ecological function. However, little attention has been given to changes in spatial patterns in CDPs during natural succession. Cyclobalanopsis glauca (Thunb.) Oerst., Quercus variabilis Blume, and Pinus yunnanensis var. tenuifolia W.C. Cheng & Y.W. Law are canopy species that form CDPs in zonal forests along the Nanpan River in southwest China. We used the g(r) function and its bivariate distribution model, g12(r), which is based on distances between pairs of points, to explore the dynamics of the three CDP species with respect to distribution patterns and spatial correlations in two secondary forests (one 30-year-old forest [30-YF] and one 57-year-old forest [57-YF]). The following key results were obtained: (1) there was a clumped pattern in the 30-YF, but the intensity of aggregation varied among populations and life stages. The distribution pattern gradually shifted to become random with longer succession time (i.e., 30-YF vs. 57-YF), expansion of the observation scale (r = 0–20 m), and at later life stages. (2) Aside from the mid-sized C. glauca trees and large P. yunnanensis trees, the trees repulsed each other at certain scales (r = 0–2, 5–6, 11–12, 14–16 m) in the 30-YF. Almost all of the life stages in the CDPs were independently correlated. This independent correlation was exacerbated by a longer succession time. (3) An increase in life stages and longer succession also promoted independent changes in intraspecific correlations. (4) Intraspecific correlations were stronger than interspecific correlations. Our results showed that reducing exclusive competition is essential to coexistence in CDPs. Inter- and intra-specific repulsion may occur at the same time, but intraspecific repulsion was the main driving force behind the random distributions and independent correlations.

Fifteen metabolites, including two flavonols (1-2), three lignans (3-5), and ten diterpenoids (6-15), were isolated from the leaves of Pinus yunnanensis. Among them, flavanonol (1) were identified as undescribed flavonol derivative with natural rarely B-ring fission lactone. Massive spectroscopic methods, the DP4+ probabilities and CD/ECD calculations were applied to establish the structure of component 1. Among these compounds, taxifolin (2) showed potent cytotoxicity, having IC50 values from 21.33 to 45.48 µg/mL, it also showed broad antibacterial activity against human pathogens with MIC values from 32 to 64 µg/mL.

The effective restoration of degraded areas, resulting in the sequestration of significant amounts of soil organic carbon (SOC) and labile soil organic carbon fractions (LOCF), is essential for mitigating global climatic changes. It is therefore important to improve our understanding of the responses and magnitudes of SOC and LOCF during restoration processes in degraded land like karst ecosystems. In this study, we selected four different restoration strategies: (1) not subjected to any management practices, mainly bare land (BL); (2) Pinus yunnanensis plantation (PY), native and characterized by slow growth and high drought resistance; (3) Eucalyptus maideni plantation (EM), non-native and characterized by rapid growth and high adaptability; (4) natural regeneration of secondary forest (SF). The SOC concentrations, SOC stocks, sensitive indicators of LOCF (microbial biomass C (MBC), permanganate oxidizable C (KMnO4-C), dissolved organic C (DOC), water soluble organic C (WSOC)), non-labile C (NLC), and the carbon pool management index (CPMI) were investigated. The different reforestation strategies had significant effects (p

Ophiostomatalean fungi may facilitate bark beetle colonization and reproduction. In the present study of the fungal community associated with bark beetle species belonging to Tomicus in Yunnan, China, six ophiostomatalean fungi (Ophiostoma canum, O. ips, O. tingens, Leptographium yunnanense, Leptographium sp. 1 and Leptographium sp. 2) were isolated from the beetles or their galleries; O. canum was the most common fungal species. The distribution of O. canum was associated with stands heavily damaged by Tomicus species and a higher percentage of valid galleries of Tomicus yunnanensis and T. minor in Yunnan pine (Pinus yunnanensis). After inoculation of Yunnan pine with the fungus, a phloem reaction zone formed and monoterpenes accumulated in the phloem. These results suggested that O. canum was pathogenic to Yunnan pine and that the wide distribution of the fungus might be beneficial to reproduction of pine shoot beetles in Yunnan pine. However, because the reaction zone and monoterpene accumulation were mild, fungal damage of Yunnan pine might be limited. A more integrated study considering all the fungal species should be done to better understand the interactions among bark beetles, blue-stain fungi, and the tree hosts in the region.

The Sloping Land Conversion Program is also known as the ‘Returning Farmland to Forest Program’ intent to gradually recreate farmlands back to the original forested state. Providing cognition on the effects of the policy on the distribution of dominant species is important to better understand plant community structures, development dynamics, regeneration conditions, and possible underlying ecological mechanisms. The purport of this study is to inspect the population structure of Pinus yunnanensis in a 2500 m2 area of abandoned farmland where restituted to forest in 2004. The results showed that the population structure of P. yunnanensis settled on tree age formed an inverted J-distribution (20.1% seedlings, 34.2% young trees, 38.5% middle-aged trees, and 7.1% adult trees) since 2009, whereas seedlings, young trees, and middle-aged trees showed clustered distribution. Seedlings showed the highest aggregation degree (g(r) = 6.4), followed by young trees (g(r) = 2.3) and middle-aged trees (g(r) = 1.7), but a random distribution showed in adults throughout the research area. The spatial relationships among seedlings, young trees, middle-aged trees, and adults indicated that the aggregation consequences increased with the decreasing difference in the diameter at breast height. Furthermore, the correlation of canopy height and diameter at breast height decreased with the increasing competition among the individuals signified that seedlings and young trees growing in the same area might use fewer resources than needed. Generally, the study illustrated that intra-specific competition due to environmental resources is a rarely occurring event.

This study used multispectral satellite imagery (Sentinel-2 MSI) to evaluate forest type mapping capabilities over a mountainous area (Shangri-La, Yunnan Province, China) at regional level. Coupled with the cloud computing platform of Google Earth Engine, the sentinel-2 satellite images were used to extract multi-temporal and spectral information, and then combined with terrain information. The random forest algorithm was adopted to identify the typical forest types. Firstly, the area is classified into forest and non-forest types. Secondly, the forest cover was sub-classified into coniferous forest and broad-leaved forest. In the end, eight types of coniferous forests (Cupressus funebris forest, Abies forest, Pinus densata forest, Picea forest, Pinus yunnanensis forest, Larix forest, Pinus armandi forest, Tsuga dumosa forest) were identified within the cover of coniferous forest. As for the whole area, the overall accuracy of forest and non-forest was 95.76%, and the Kappa coefficient was 91.34%. Within the forest coverage, the overall accuracy of the coniferous forest and the broadleaf forest was 89.74%, and the Kappa coefficient was 79.26%. And within the coniferous forest, the overall accuracy of the eight types of coniferous forest was 91.59%, and its Kappa coefficient was 90.33%. The classification results indicated that topographic information is beneficial to the extraction of forest type information, and multi-temporal Sentinel-2 imagery has great potential to accurately identify forest type at regional level.

Forest fuel load plays an important role in fire ignition, spread and intensity. Accurate spatial distribution information of fuel load is vital for fire managers to make decisions. However, most of the existing studies using spectral or texture information of optical data, which is seriously affected by atmospheric conditions with limited penetration. SAR with all-day and all-weather work characteristics provides a favorable opportunity to estimate fuel loads in Southwest China with cloudy and foggy. Moreover, SAR can penetrate through leaves to branches and stems, which reflects the forest vertical structure well. However, there was little research applying SAR data to fuel load estimation. In this study, we focus on forest above ground live fuel load estimation (biomass fractions), including stem fuel load (SFL), branch fuel load (BFL) and foliage fuel load (FFL). We explored the potential of dual polarimetric data, Sentinel-1 for coniferous forest fuel loads estimation in the Southwest of Sichuan, China. To understand scattering mechanisms at C-band in Pinus yunnanensis forest, the Michigan Microwave Canopy Scattering (MIMICS) radiative transfer model was used. And Multiple Linear Regression (MLR) method was used to estimate fuel loads. Results show that VH and VV polarizations were both sensitive to three types of fuel load. Combined with the simulation of MIMICS, we found VH polarization was more sensitive to FFL while VV was more sensitive to SFL. Additionally, Sentinel-1 performs well in all three types of fuel load estimation (FFL: R2 = 0.52, RMSE=1.43 Tons/ha; BFL: R2=0.58, RMSE=1.88 Tons/ha; SFL: R2=0.57, RMSE=2.97 Tons/ha), indicating that Sentinel-1 data has great potential in FFL estimation and fire prevention.

Background The relative influence of climate change and drought events on tree growth at different altitude and tree ages remains insufficiently understood in the Jinsha River Basin, southwest China, limiting prediction of forest adaptability to high-frequency droughts and climate change. We conducted a dendroecological study to explore and quantify the dominant climate factors that determining radial growth of Pinus yunnanensis trees of different ages and at different altitudes, to evaluate their resilience to drought events. Results Radial growth of P. yunnanensis at high elevations is typically limited by low temperatures, the explanatory rate of temperature factors on growth increased from 23.6–59.7% with altitude. Tree growth at low elevations is more sensitive to moisture factors, the explanatory rate of moisture factors on growth decreased from 76.4–40.3% with altitude. The young and mature trees are more prone to moisture factors than middle-age and near-mature trees, the young and near-mature trees are more prone to temperature factors than middle-age and mature trees. The older trees usually showed less drought resistance and recovery than the young and middle-age trees. The resistance and recovery of P. yunnanensis weakened with the increased frequency of drought events. Tree resistance and resilience was highly dependent on the average pre-drought growth, whereas the recovery showed weak or no significant relationships with average pre-drought growth. Conclusion Our study demonstrates that radial growth of P. yunnanensis trees showed age- and altitude-specific demand for energy and moisture. P. yunnanensis trees at different altitudes and ages are differentially adapted to varying levels of climate stress and display different strategies to withstand the effects of drought with altitude and ages.

The Yunnan Province of China is wet and warm enough to support magnificent forests. However, many mountains in the region are covered by a shrubland formation dominated by an unusual pine, the shrubby and multistemmed Pinus yunnanensis (Yunnan pine; Fig. 1). This formation is natural, and not the product of forest degradation; and fire appears to be a major factor explaining the features of this pine. This region has a subtropical monsoon climate influenced by both the Indian Ocean Monsoon from the west, and the Pacific Ocean Monsoon from the east. The climate has prominent seasonality in temperature and precipitation, alternating a warm dry season (December to May) with a hot wet season (June to November; Chen et al. 2019). The annual dry season creates conditions that can favor wildfires. Fires are currently common mainly between February and April (Zhao et al. 2009), with area burned depending on the variations in annual precipitation (Chen et al. 2014, Ying et al. 2017). The shrubby pines are found in the upper portions of the landscape, where it is drier and fires are more frequent. The Yunnan pine has several adaptations to frequent crown fires, which suggests that fires have long existed in the region and are not just a product of recent human activity (see Shao et al. 2012 for evidence of paleofires in the region). These fire adaptations include (Fig. 1) serotiny (Su et al. 2015), basal resprouting, and high precocity (, This study was sponsored by the National Natural Science Foundation of China (Project No. 41971228).

Pinus yunnanensis forest is a unique forest type in southwest China and one of the main forest types in Yunnan Province, which also has great ecological, economic and social significance. Understanding the changes in the stoichiometric characteristics is a key to study the nutrient cycling, limiting factors and stability mechanisms of the forest ecosystem. However, the stoichiometric characteristics, stability of the ecosystem of P. yunnanensis natural forests and whether they are limited by nutrients are still poorly understood. Based on a K-S test, ANOVA analysis and OLS regression analysis, we analyzed the concentrations of leaf C, N and P in 48 woody species of natural P. yunnanensis forests from 122 plots to explore the pattern of leaf C:N:P stoichiometry. Our results showed that the mean values of leaf C, N and P plus C:N, C:P and N:P for the 48 woody species were 451.12, 11.05 and 1.11 mg/g and 45.03, 496.98 and 11.27, respectively. The coefficients of variation of leaf C, N and P plus C:N, C:P and N:P were 5.29%, 36.75%, 51.53%, 29.63%, 43.46% and 41.68%, respectively. The geometric mean values of leaf N, P and N:P were 10.49 and 1.00 mg/g and 10.51, respectively. Leaf C and N, and C and P relationships showed significant negative correlations, but a significant positive correlation was observed between leaf N and P. There were significant differences in leaf N and C:N across functional groups. There were significant differences in leaf C and P between evergreen and deciduous, conifer and broadleaf trees. Significant differences in leaf C:P were only observed between evergreen and deciduous trees, and significant differences in leaf N:P were observed between conifer and broadleaf trees. The relatively low N:P in all sampled trees indicated that N was a limiting factor in the distribution of natural P. yunnanensis forests. However, the higher leaf C:N and C:P ratios indicated that the P. yunnanensis natural forest ecosystem was in a relatively stable state.

The effects of low-intensity and high-frequency prescribed burning on the soil CO2 emissions from Pinus yunnanensis forestland should be explored to achieve sustainable operation and management under fire disturbance. A Li-6400XT portable photosynthesis meter (equipped with a Li-6400-09 soil respiration chamber) and a TRIME®-PICO 64/32 soil temperature and moisture meter were used to measure the soil CO2 flux, soil temperature, and soil moisture at fixed observation sites in two treatments (i.e., unburned (UB) and after prescribed burning (AB)) in a Pinus yunnanensis forest of Zhaobi Mountain, Xinping County, Yunnan, China from March 2019 to February 2021. We also determined the relationships between the soil CO2 flux and soil hydrothermal factors. The results showed that (1) the soil CO2 flux in both UB and AB plots exhibited a significant unimodal trend of seasonal variations. In 2020, the highest soil CO2 fluxes occurred in September; they were 7.08 μmol CO2·m−2·s−1 in the morning and 7.63 μmol CO2·m−2·s−1 in the afternoon in the AB treatment, which was significantly lower than those in the UB treatment (p < 0.05). The AB and the UB treatment showed no significant differences in annual soil carbon flux (p > 0.05). (2) The relationship between the soil CO2 flux and moisture in the AB and UB plots was best fitted by a quadratic function, with a degree of fitting between 0.435 and 0.753. The soil CO2 flux and soil moisture showed an inverted U-shaped correlation in the UB plot (p < 0.05) but a positive correlation in the AB plot (p < 0.05). Soil moisture was the key factor affecting the soil CO2 flux (p < 0.05), while soil temperature showed no significant effect on soil CO2 flux in this area (p > 0.05). Therefore, the application of low-intensity prescribed burning for fire hazard reduction in this region achieved the objective without causing a persistent and drastic increase in the soil CO2 emissions. The results could provide important theoretical support for scientific implementation of prescribed burning, as well as scientific evaluation of ecological and environmental effects after prescribed burning.

Bark beetles Tomicus yunnanensis and T. minor are two important pests of Pinus yunnanensis and can cause massive death of pine trees. In this study, we examined several traits related to photosynthesis in P. yunnanensis and their relationship with antibiotic defense responses after joint attack by the two bark beetles at the shoot and the trunk stages. When shoots were attacked by the beetles, the abundance of chlorophylls, carotenoids, and the rates of net photosynthesis (Pn) and transpiration (E) decreased in needles, while the levels of superoxide dismutase and malondialdehyde remained unchanged in both needles and phloem. The activity of peroxidases also remained unchanged in needles, but increased in phloem. The activity of catalases increased in both needles and phloem. When trunks were attacked by the bark beetles, chlorophyll abundance, Pn, E, and antioxidative enzyme activities all declined, and the declines were more pronounced than in the attacked shoots. A decrease in protein concentrations was also observed in needles and phloem from the attacked pines. Attack on shoots by the bark beetles suppressed host defense and provided a favorable environment for larval growth and development, resulting in long-term decline of pine growth potential. The results suggest that attacks on trunks by beetles caused more severe damage to host trees than attacks on shoots.

CephalciachuxiongicaXiao is one of the most dangerous defoliators ofPinusyunnanensisand other pine species in Yunnan province, resulting in serious losses. Its distinguishing characteristics are the females’ aggregation oviposition and larvae’s aggregation feeding. In order to explore the mechanism of aggregation oviposition in this sawfly, preliminary olfactory bioassay was conducted in laboratory. In in-cage choice tests, on average vast majority gravid females selected the shoots that had been loaded and oviposited by a ‘pioneer’ female. In one-choice tests in laboratory by a Y-tube olfactometer, the gravid females were attracted by the odors of eggs-carrying shoots (PE), shoots with one delivering female and her eggs (PGE), needles’ extract (NE), and fresh eggs’ eluent (EL); the virgin females were attracted by odors of fresh needles (P), PE, PGE, and NE, but repelled by odors of virgin and gravid females. In two-choice tests, the odors were tested in pairs for gravid females. When compared with odors of gravid females (G) or P, gravid females showed significantly more tendency to odors of PE or PGE. When given odors EL vs. NE, gravid females preferred the odors of NE, but they did not make obvious selection between G vs. P, and PE vs. PGE. Based on the results, our conjectures were: (1) Delivery female, as a pioneer, can summon her conspecific gravid females to aggregate in the same pine shoot; (2) Pine needles’ odors were attractive for both the virgin and gravid females; (3) Gravid females could be attracted by odors released by the pioneer gravid females; (4) The olfactory sensation of the females may be changed by mating.

Pinus yunnanensis var. Tenuifolia is an important species of timber and grease in southern China, but the characteristics of the soil microbial community in P. yunnanensis var. natural secondary fo...

The bark beetle, Tomicus yunnanensis (Coleoptera: Scolytinae), is a seriously destructive pest of Yunnan pine (Pinus yunnanensis) and is distributed solely in Southwestern China. It has been a challenge to control this pest owing to its resistance to chemical pesticides, which have been used as the main control strategy of this species in recent years. Since this approach will continue until an alternative mitigation strategy is implemented, it is essential to develop novel or improved biocontrol approaches. In the current study, we aimed to identify most, if not all, of the bark beetle's chemosensory genes, and to address their respective phylogenetic relationships and expression characteristics. Digital gene expression (DGE) profiling and a comparison of the profiles at three developmental stages yielded 40,287,265 clean reads and a large number of differentially expressed genes (DEGs), with 21 up- and 20 down-regulated DEGs involved in chemoreception. Transcriptome of the three mixed stages revealed a total of 80 transcripts encoding chemosensory-related proteins comprising 45 odorant-binding proteins (OBPs), 12 chemosensory proteins (CSPs), 20 receptor proteins [9 odorant receptors (ORs), 8 gustatory receptors (GRs) and 3 ionotropic receptors (IRs)] and 3 sensory neuron membrane proteins (SNMPs). As many as 38 full-length sequences were acquired with a combination of transcriptomic analysis and rapid amplification of cDNA ends (RACE) strategy. Phylogenetic analysis showed that T. yunnanensis OBPs were clustered into four sub-groups: 27 Minus-C OBPs, 5 antennal binding proteins (ABPIIs), 10 Classic OBPs and one Plus-C OBP; meanwhile, the ORs were grouped into four clades (1, 2, 7b and Orco). Expression profiles revealed that 66 of 80 genes were detected in the three DGE libraries, and 15 soluble olfactory proteins were antennae-predominant, possibly guiding olfactory-associated behaviors of this beetle. Taken together, our study has provided valuable data for further functional studies of this beetle and will facilitate the identification of potential molecular targets associated with chemosensory reception for use in biocontrol strategies.

Climate change has already had observable impact on the biophysical environment, and lead to the different sensitivity of vegetation to climate factors on spatio-temporal scale. Therefore, understanding how the radial growth respond to climate at different spatio-temporal scales is crucial to recognize forest growth dynamic and make scientific management decisions under the background of climatic change. In the present study, the tree ring of Pinus yunnanensis at six altitudes gradients between 1300 m and 2500 m from a typical arid-hot valley in Jinsha River, were collected. We analyzed the relationship between radial growth and climate at different altitudes, and the sensitivity of growth to climatic factors over time. The results showed that the mean width of tree rings decreased as the altitude increasing. The relationship between climatic factors and radial growth at low or high altitudes was different with that at mid altitudes. Radial growth was negatively correlated to the temperatures from February to July at both low altitudes (1300-1500 m) and at high altitudes (2200-2500 m), but positively correlated to the temperatures in October of the previous year to April at mid altitudes (1700-1900 m). Precipitation in October of the previous year, May, and June in growing year had a positive effect on radial growth at all altitudes. Temperature and precipitation in the previous year showed a time-lag effect on radial growth. A moving correlation analysis of the tree ring index and climate variables showed that the limiting factors for tree growth at different altitudes varied over time. The influence of drought on the tree growth increased gradually as the climate warming. In future research, evaluating the dynamic relationship between vegetation growth and climate warming at spatio--temporal scale will be particularly important to guide forest management.

Understanding the influence of invasive species on understory communities is necessary to maintain ecosystem functions. Here, we describe the effects of different abundances of the invasive species Ageratina adenophora on the composition and structure of understory communities and on Pinus yunnanensis seedling growth under pine stands in mid-Yunnan, China. Our data show that the different abundances of A. adenophora altered species and functional diversity by changing the species composition and abundance in the understory community because of its higher specific leaf area, leaf nitrogen concentration (LNC), and leaf phosphorus concentration compared with native species. Meanwhile, the presence of A. adenophora led to changes in the patterns of species co-occurrence, with a shift from random to segregated patterns as the invasion intensity increased. Furthermore, the order of species loss under invasion was nonrandom. The LNC could be an indicative functional trait predicting the order of species ...

Past studies have provided extensive documentation of changes in species diversity in response to land-cover alteration; however, little is known about the effects of land-cover alteration on the patterns of functional structures and ecosystem functions. In this study, we introduce a functional trait-based methodology for incorporating multiple levels of functional structures into models to assess the impacts of human-induced land-cover changes on functional structures and to evaluate how these functional attributes affect ecosystem functions. To this purpose, different functional structure indices (species diversity, functional diversity, and community-weighted mean trait values) in three widespread communities (a man-made Pinus yunnanensis forest, a man-made Eucalyptus smithii forest, and a natural secondary forest) were determined, with a focus on our study sites in southwest China. Meanwhile, ecosystem functions (soil nutrients, water and soil conservation, and multifunctionality) were quantified. Our results showed that most community diversity indices were affected by human-dominated land-cover changes, except species richness and functional evenness. Changes in the relationship between species diversity and functional diversity displayed two patterns. The first pattern reflected reduced species diversity with an increase in functional diversity, whereas the second pattern was associated with a correlated loss of species and functional diversity, indicating the removal of environmental filters in response to changes from natural secondary forest to man-made forests. Community-weighted mean trait values (related to leaf nitrogen [N] concentration, leaf phosphorus [P] concentration, and seed mass) were negatively correlated with water and soil conservation and multifunctionality, which accounted for 65.9% and 48.5% of the variance, respectively. Functional diversity (based on functional richness, quadratic entropy, and functional dispersion) was positively associated with soil nutrients and explained 33.6% of the variance. These results suggest that the community functional structure was affected by land-cover alteration through changes in environmental filters and replacement by functionally different species. Moreover, changes in functional structure characteristics mediate different ecosystem functions by niche complementarity or the mass ratio effect under land-cover alteration.

Pine shoot beetle (PSB, Tomicus spp.) outbreaks cause widespread Yunnan pine (Pinus yunnanensis Franch) mortality in southwestern China. Early identification of PSB attacks could help forest managers mitigate the infestation before it turns into an outbreak. However, the subtle spectral changes and complex process of PSB-induced crown discoloration make the remote sensing approach difficult. This study employed a manipulated insect infestation experiment to reveal suitable monitoring indicators. Healthy Yunnan pine crowns were infested with PSB adults at different preset densities (light, moderate, and severe) using the bagging method. The crown damage parameters, physiological properties, and corresponding spectral data were systematically measured in time series. Partial least squares regression (PLSR) was used to retrieve crown chlorophylla+b (Cab) and relative water content (RWC) via band reflectance. Random forest (RF) was used to determine the optimum spectral variables capable of capturing dynamic variations in crown shoot damage ratio (SDR). Results showed that (1) after four weeks’ PSB shoot feeding attack, SDR reached saturated (26%-50%) for all damage levels, indicating a crown discoloration “switch point”. (2) A continuous decline was found in Cab and RWC at both shoot and crown levels during the whole infestation process, and the crown level decrease was smaller than the shoot level due to crown heterogeneous discoloration. (3) For PLSR retrieving crown Cab and RWC, estimation accuracy of healthy crowns could reach R2 = 0.70, RMSEcv = 14.60 mg/m2 for Cab, and R2 = 0.82, RMSEcv = 1.25% for RWC, respectively. However, PSB early attack impacted these retrieval accuracies. (4) Spectral differences were evident in the visible region (530–600 nm) and near-infrared (NIR) plateau (780–1300 nm) among the preset damage levels. Significant differences in spectral variables (AMP, CI, OSAVI, RD, and SR) were observed between healthy and moderately damaged crowns. (5) In RF modeling, the importance of spectral variables for SDR estimation varied throughout the shoot feeding process. OSAVI, CI, MSI, PSRI, and SR2 were the top indicators that were suitable for identifying SDR ranging from 5% to 50%. SDR could be estimated with an accuracy of R2 = 0.71, RMSEcv = 8.92%, after 4 weeks’ infestation. Simultaneously, with the RF model, 4 preset damage levels could be differentiated with an out-of-bag error of 14.94% and a kappa coefficient of 0.8835. In conclusion, this study mainly examined the physiological and spectral signatures of PSB early attacked crowns, and provided optimum spectral variables and models which will further help unmanned aerial vehicle (UAV) and satellite remote sensing identify PSB infestation at the early stages.

Estimating individual tree biomass is critical to forest carbon accounting and ecosystem service modeling. In this study, we developed one- (tree diameter only) and two-variable (tree diameter and height) biomass equations, biomass conversion factor (BCF) models, and an integrated simultaneous equation system (ISES) to estimate the aboveground biomass for five conifer species in China, i.e., Cunninghamia lanceolata (Lamb.) Hook., Pinus massoniana Lamb., P. yunnanensis Faranch, P. tabulaeformis Carr. and P. elliottii Engelm., based on the field measurement data of aboveground biomass and stem volumes from 1055 destructive sample trees across the country. We found that all three methods, including the one- and two-variable equations, could adequately estimate aboveground biomass with a mean prediction error less than 5%, except for Pinus yunnanensis which yielded an error of about 6%. The BCF method was slightly poorer than the biomass equation and the ISES methods. The average coefficients of determination (R 2) were 0.944, 0.938 and 0.943 and the mean prediction errors were 4.26, 4.49 and 4.29% for the biomass equation method, the BCF method and the ISES method, respectively. The ISES method was the best approach for estimating aboveground biomass, which not only had high accuracy but also could estimate stocking volumes simultaneously that was compatible with aboveground biomass. In addition, we found that it is possible to develop a species-invariant one-variable allometric model for estimating aboveground biomass of all the five coniferous species. The model had an exponent parameter of 7/3 and the intercept parameter a 0 could be estimated indirectly from stem basic density (a 0 = 0.294 ρ).

Forest stand structural diversity can be examined at different scales. Small-scale structural changes are the basis of forest structural diversity and habitat heterogeneity, and play a key role in biodiversity conservation. Most research on forest structure has focused mainly at stand level and above, with little attention paid to fine-scale structure and correlations among different forest stand attributes. We set up four permanent plots within a secondary forest community of Pinus yunnanensis var. tenuifolia mixed forests along the Nanpan River in southern China. We analyzed their nearest-neighbor relationships using a bivariate distribution of stand spatial structural parameters (SSSP) with the aim of understanding the processes that drive structural diversity in the development of a secondary forest community. Our results revealed that communities with different disturbance histories and species compositions differed in the level of species mixture. Large, small, and medium-sized trees were well mixed within the community, both conspecific and heterospecificindividual with varying densities. All plots exhibited a uniform size differentiation pattern. Trees with different dominance levels or mixture levels were randomly distributed within the plots, and only few of these displayed clumped or regular distribution. Pearson’s correlation analysis revealed that distribution patterns may be related to species composition and diameter differentiation, though their relationship was very weak. The results of this study are relevant to optimize forest management activities in the studied stands, and promote tree growth, regeneration and habitat diversity at the fine scale.

The Tibetan forest is one of the most important national forest zones in China. Despite the potentially important role that Tibetan forest will play in the Earth’s future carbon balance and climate regulation, few allometric equations exist for accurately estimating biomass and carbon budgets of this forest. In the present study, allometric equations, both species-specific and generic, were developed relating component biomass (DW) to diameter at breast height (DBH) and tree height (H) for six most common tree species in Tibetan forest. The 6 species were Abies georgei Orr., Picea spinulosa (Griff.) Henry, Pinus densata Mast., Pinus yunnanensis Franch., Cypresses funebris Endl. and Quercus semecarpifilia Smith.. The results showed that, both DBH-only and DBH2H based species-specific equations showed a significant fit (P

Wood as a renewable engineering material has widely been used for structural purpose for decades, but its static bending modulus of elasticity (E b) has not been seriously researched in large-scale relative humidity fluctuant environment. This paper presents an experimental and numerical study for the assessment of E b of Pinus yunnanensis as a function of moisture content and its distribution in high relative humidity environment. For this, a moisture transfer model based on a multi-phase-type approach and a classical theory of laminated plate was used. The experimental results indicated that the predicted E b had good agreement with measured data making it possible for researchers, designers, and industry in the field of wood mechanics and products to directly obtain the wood E b by way of calculation. Furthermore, it was also found that there was a decrease in E b in the short term when the environment relative humidity increased substantially. This phenomenon reminds designers and industry in the field of wood mechanics and products that using so-called E b with equilibrium moisture content as the actual mechanical value of structural-use wood may bear a potential risk.

Local adaptation, adaptation to specialized niches and environmental clines have been extensively reported for forest trees. Investigation of the adaptive genetic variation is crucial for forest resource management and breeding, especially in the context of global climate change. Here, we utilized a Pinus yunnanensis common garden experiments established at high and low elevation sites to assess the differences in growth and survival among populations and between the two common garden sites. The studied traits showed significant variation between the two test sites and among populations, suggesting adaptive divergence. To detect genetic variation related to environment, we captured 103,608 high quality SNPs based on RNA sequencing, and used them to assess the genetic diversity and population structure. We identified 321 outlier SNPs from 131 genes showing significant divergence in allelic frequency between survival populations of two sites. Functional categories associated with adaptation to high elevation were found to be related to flavonoid biosynthesis, response to UV, DNA repair, response to reactive oxygen species, and membrane lipid metabolic process. Further investigation of the outlier genes showed overrepresentation of the flavonoid biosynthesis pathway, suggesting that this pathway may play a key role in P. yunnanensis adaptation to high elevation environments. The outlier genes identified, and their variants, provide a basic reference for advanced investigations.

Saprophytic fungi (SPF) play vital roles in ecosystem dynamics and decomposition. However, because of the complexity of living systems, our understanding of how SPF interact with each other to decompose organic matter is very limited. Here we studied their roles and interactions in the decomposition of highly specialized substrates between the two genera Auriscalpium and Strobilurus fungi-colonized fallen pinecones of the same plant sequentially. We obtained the genome sequences from seven fungal species with three pairs: A. orientale-S. luchuensis, A. vulgare-S. stephanocystis and A. microsporum-S. pachcystidiatus/S. orientalis on cones of Pinus yunnanensis, P. sylvestris and P. armandii, respectively, and the organic profiles of substrate during decomposition. Our analyses revealed evidence for both competition and cooperation between the two groups of fungi during decomposition, enabling efficient utilization of substrates with complementary profiles of carbohydrate active enzymes (CAZymes). The Auriscalpium fungi are highly effective at utilizing the primary organic carbon, such as lignin, and hemicellulose in freshly fallen cones, facilitated the invasion and colonization by Strobilurus fungi. The Strobilurus fungi have genes coding for abundant CAZymes to utilize the remaining organic compounds and for producing an arsenal of secondary metabolites such as strobilurins that can inhibit other fungi from colonizing the pinecones.

Both Pinus yunnanensis and P. kesiya var. langbianensis are the main components of forest vegetation in central Yunnan and southern Yunnan, respectively. Previous studies have found that these two species may be differentiated from a common ancestor due to differences in precipitation in their respective habitats. To confirm the possible reasons for the differentiation of the two species in southwest China, we studied the seed germination of P. yunnanensis and P. kesiya var. langbianensis under different temperatures, water potentials and storage conditions. The temperature range of 15℃ to 30℃ was appropriate for seed germination and normal seedling emergence of the two pines. Under the water potential of 0 MPa to −0.6 MPa, germination percentages of P. yunnanensis and P. kesiya var. langbianensis were 63.2% to 80.8% and 71.2% to 91.6%, respectively. When the water potential decreased to −0.8 MPa to −1 MPa, the germination percentages of the two species decreased below 30%, but the germination percentage of P. yunnanensis was higher than that of P. kesiya var. langbianensis. After stored for 1, 3, 5 and 7 months at −20, 4, 15 and 25℃, the seed germination percentages of the two species still maintained above 60%. When the seeds of P. yunnanensis and P. kesiya var. langbianensis were buried at Xishuangbanna in southern Yunnan, China, they lost vigor rapidly due to the highest precipitation. Especially, after buried for 2 months, the germination percentage of P. yunnanensis was 0. These results suggested that moisture is a key factor affecting seed germination of P. yunnanensis and P. kesiya var. langbianensis, and the seeds of P. yunnanensis preferred lower moisture levels for germination than P. kesiya var. langbianensis. Thus, the difference in the response of seed germination and storage of the two species to moisture levels may be an important factor causing the difference in their geographical distribution patterns.

International audience; China has recently announced a reform of forestry policy, with a major goal being to transform from plantation to heterogeneous forests, which have higher resistance to pests and disease and house more biodiversity. One driver of reform is increased intensity and frequency of pest-induced tree-dieback events. To inform management, we ask what effects these events have on insect biodiversity in Pinus yunnanensis monocultures in Yunnan province, the province with one of the highest proportions of forest cover in China. We sampled aerial arthropods (mostly insect) biodiversity along gradients of Pinus yunnanensis dieback severity using Malaise traps and used metabarcoding to characterise the insect community. We used MS-GDM ('multi-site generalized dissimilarity modelling of zeta diversity'), zeta-decline analysis, and iNEXT ('Interpolation and extrapolation for species diversity') to assess community change as functions of forest-structure covariates. Metabarcoding of Malaisetrapped insects reveals that bark-beetle induced forest dieback does not result in detectable differences in species diversity but does result in compositional change, with the biggest turnover occurring between 0% and infested-0%-open-canopy forests and 20%-infested-20%-open-canopy forests. Zeta-decline analysis found that the insect community in low-infestation forests is characterized by a stochastic assembly, while in highinfestation forests, the community structure is consistent with niche assembly. Our results thus suggest that bark-beetle dieback mimics natural forest-gap dynamics, consistent with the interpretation of bark beetles as a keystone species in European conifer forests, where it has been proposed that forest heterogeneity can be created efficiently by allowing natural disturbances, including bark-beetle outbreaks, to proceed naturally, without being mitigated by deadwood removal and dense replanting. In Yunnan's situation, and given predicted increases in bark-beetle dieback severity and frequency, this strategy should probably be supplemented with anthropogenic treatments, such as deadwood enhancement and planting of multiple tree species, to accelerate the succession of plantations into heterogeneous forests.

The activity concentration of 137Cs and 40K and total K content in the sclerotia of the Chinese medicinal fungus Wolfiporia cocos collected mainly from Yunnan province of China during the period 2013–2015 were investigated. W. cocos in Yunnan is collected from the wild and is cultivated in field conditions and the wood substrate used is derived from the local pine (Pinus yunnanensis Franch.) logs from neighborhood forests. The outer part of sclerotia was found to be richer than the inner one in both 137Cs and 40K with median values of 7.3 and 3.2 Bq kg−1 dry weight (dw) for 137Cs, 220 and 140 Bq kg−1 dw for 40K. The median K concentrations were 6800 mg kg−1 dw in the outer and 3700 mg kg−1 dw in the inter parts. No statistically significant correlation was found for activity concentrations between the inner and outer parts, both for 137Cs and 40K (p > 0.05). Using the median activities of 137Cs, the nominal values of effective dose (mSv) for exposed adults annually consuming 50 g of sclerotia, were estimated at 0.0035 mSv and 0.084 mSv (outer part), and 0.0020 mSv and 0.040 mSv (inner part) per capita, respectively. Sclerotia of W. cocos seemed to be a relatively good source of K.

Provenance selection plays a major role for the afforestation success, resilience and persistence of forests into the future. Understanding the germination response to water potential and temperature among provenances is crucial for forest restoration initiatives. However, afforestation programs often neglect the seed germination traits from a selected provenance, threatening natural or artificial regeneration in future. In this study, we assessed the impact of water potential (0 and -0.2 MPa) and temperature (20, 25, and 30°C) on germination of Pinus yunnanensis seeds from 15 provenances. We found a clear effect of seed provenance on the germination percentage and mean germination time. In general, the lower water potential (-0.2 MPa) led to a reduction of germination percentage for most provenances, especially at 30°C; and the higher temperature (30°C) and water potential (0 MPa) resulted in low mean germination time. Germination percentage and mean germination time responses to water potential and temperature varied among provenances. We observed that germination percentage was significantly positively correlated with annual mean temperature, mean temperature of driest quarter and seed mass associated with the provenance, but significantly negatively correlated with annual mean precipitation, and mean precipitation of driest quarter and wettest quarter. Significant relationships between mean germination time and those variables were contrary to germination percentage. However, the significance of these relationships varied in all the treatments. Therefore, we conclude that germination of P. yunnanensis seeds from different provenances adapt diversely to abiotic stresses; this is likely to be important for provenance selection in future reforestation. Our results highlight that future re-forestation efforts need to critically evaluate larger numbers of provenances to understand thresholds limiting performance and establishment success.

Long-term, high-resolution proxy records containing cold season temperature signals are scarce on the southeastern Tibetan Plateau (TP), limiting our understanding of regional climate and the potential driving forces. In this study, we present a nearly three centuries long reconstruction of winter (December–February) mean temperature for the central Hengduan Mountains, southeastern TP. The reconstruction is derived from a composite tree-ring width chronology of Pinus yunnanensis Franch from two high elevation sites (>3000 m above sea level). Our reconstruction passes all standard calibration-verification schemes and explains nearly 73 % of the variance of the original instrumental data. However, we were constrained to calibrate our full period (1718–2013) reconstruction of December–February mean temperature on the calibration period from 1959 to 1992 only, due to a decrease in temperature sensitivity of tree-ring index exhibited after 1992. Spatial correlation analysis shows that our reconstruction represents large-scale temperature variations in southwest China and the eastern TP. Our reconstructed December–February mean temperature shows a close association with the Atlantic Multidecadal Oscillation (AMO) over the past three centuries, with warm (cold) periods coinciding with the positive (negative) phases of the AMO. This persistent relationship suggests that the AMO may have been a key driver of multidecadal winter temperature variations on the southeastern TP.

Differences in seed germination and seedling growth among populations of Pinus yunnanensis Franch. were quantified to provide information for use in the regeneration, reforestation, and improvement of this species. Seed germination and seedling growth traits at the nursery stage were investigated at the population level. We evaluated relationships between pairs of measured traits as well as the association between measured traits and geo-climatic variables including longitude, latitude, elevation, temperature and precipitation. Seedling growth showed significant differences although a low magnitude of variation was found in the seed germination traits among the populations. Some populations with strong and stable growth (e.g., the Baoshan population) may be selected as superior seed sources for regeneration and reforestation. Germination percentage was negatively correlated with elevation, and positively with precipitation. In addition, germination index, vigor index and seedling height were positively correlated with precipitation. Seed germination index, cotyledon number and length, and seedling diameter were significantly and positively correlated with seed weight. Strong correlations between pairs of traits will be helpful in early evaluations for the selection of certain prominent traits.

Within-crown heterogeneity exists in multiple vegetation scenes including forest stands with heterogeneous distribution of damaged foliage. The existing radiative transfer approaches implement the within-crown heterogeneity either using complicated three-dimensional (3D) scenes with excessive amounts of parameters, or simplifying the scenes to homogeneous cases by averaging canopy optical properties. In order to ascertain the optical response to within-crown heterogeneity both efficiently and accurately, we proposed a method for simulating bi-directional reflectance factor (BRF) of forests infected by pests based on the stochastic radiative transfer (SRT) theory. Each damaged tree crown was classified into one of the three types: top-only damage, bottom-only damage and random damage. The statistical properties of such canopy structures were described with extended definitions of the stochastic moments of the SRT model, including the probabilities of finding different foliage classes and the conditional pair-correlation functions between healthy and damaged foliage. Field measurements and remote sensing data from unmanned aerial vehicle (UAV) over infected Yunnan Pine (Pinus yunnanensis) forests, and simulations of two 3D models were utilized to evaluate the performance. Results showed that the extended SRT agreed well with 3D models and field measurements, which means it has the capability to model BRF over forests with heterogeneous foliage within crowns based on one-dimensional (1D) theory. The extended SRT provides a framework to analyze the sensitivity of canopy reflectance to the distribution of damaged foliage with the variation of other key scene factors. For the three types of damaged tree crowns, the thresholds of detectable optical changes were quite different, in which 20% for top-only damage, 80% for bottom-only damage and 50% for random damage. The uncertainties caused by other scene factors were also considered. The extended SRT is promising for crown vertical profile specification, forest damage quantitative inversion, and other applications with coupling models.

Forest secondary succession alters plant diversity and soil properties in the forest ecosystems; however, effects of this process on the soil fungal community structure are poorly understood. We used Illumina high-throughput sequencing to identify soil fungal community during forest secondary succession (including 30-, 45-, 60-, and 80-year-old stands) in the Pinus yunnanensis forest. The aims were to explore how plant diversity and soil properties drive soil fungal community structure and elucidate the role of fungal guilds in integrating the linkages of plant diversity and soil properties with forest secondary succession. Our study found that forest secondary succession changed woody species composition, richness, and soil properties, furthermore, this also affected significantly soil fungal diversity, community composition, and the abundances of the different functional guilds along the forest secondary succession. Soil fungal diversity initially increased up to the 60-year-old stand, and then decreased with forest secondary succession. The main phyla included Agaricomycetes, Leotiomycetes, Mortierellomycetes, and Eurotiomycetes, and indicator phyla varied differently with forest secondary succession. Soil fungal community could be clearly divided into the four successional stages. Forest secondary succession affected significantly soil fungal diversity via altering woody species richness and soil properties. Mycorrhizal, saprotrophic, and endophytic fungi interacted differently with forest secondary succession. Ectomycorrhizal fungi (ECM) played a vital role in driving forest secondary succession, and greater ECM fungal abundance could drive the forest secondary succession process through changes in the ECM plant composition. ECM plant community composition displayed different effects on ECM fungal abundance. As a result, ECM fungal abundance increased with a higher abundance of Castanopsis orthacantha, and decreased with a higher abundance of P. yunnanensis. Ericoid mycorrhizal fungal abundance reached its maximum in the 45-year-old stand and then decreased, which could provide valuable information for understory restoration. Undefined saprotrophic fungal abundance decreased with increasing forest secondary succession, accompanied by an increase of ECM fungal abundance, while endophytic fungi increased with forest secondary succession. Our findings suggested that plant-fungal symbionts and environmental selection posed an important constraint in assembly of soil fungal community and functional guild abundances. Altogether, these results provided new insights for predicting shifts in plant and soil fungal community strategies with the forest secondary succession in the P. yunnanensis forest.