Convolutional neural network tree species identification based on tree-ring radial section image features.

Convolutional neural networks can automatically identify tree species based on the images of structural features of tree-rings samples. In this study, we used a tree-ring image dataset for different species to achieve tree-ring based species automatic identification with high accuracy by four convolutional neural network models (LeNet, AlexNet, GoogLeNet, and VGGNet), aiming to determine the identification accuracy of the models, clarify the species misidentification during the automatic processes, and explore the identification differences among the models. The results showed that tree species identification derived from the trained convolutional neural network models was reliable, with the GoogLeNet and LeNet showed the highest (96.7%) and lowest (66.4%) identification accuracy. The tree species identifications using different models were highly consistent. Quercus mongolica and Abies nephrolepis showed the highest (100% for AlexNet) and lowest identification accuracy, respectively. Misidentification could occur among tree species with similar tree-ring structure. The identification accuracy of the models was higher at family and genus levels than that at the species level. The identification accuracy of broadleaf tree species was higher than that of coniferous trees due to distinct radial structure among broadleaf species. Overall, our method achieved a high accuracy for tree species identification, and provided a fast, convenient, and automatic tree species identification by detecting specific tree-ring properties with convolutional neural network.

[Warming-drying climate intensifies the restriction of moisture on radial growth of Pinus tabuli-formis plantation in semi-arid area of Northeast China]. / æš–å¹²åŒ–åŠ å‰§ä¸œåŒ—åŠå¹²æ—±åœ°åŒºæ²¹æ¾äººå·¥æž—å¾„å‘ç”Ÿé•¿çš„æ°´åˆ†é™åˆ¶.

Plantation ecosystems are more vulnerable than natural ones to global climate change. Using the dendrochronology method, we established tree-ring width chronologies of Pinus tabuliformis distributed in the semi-arid region of Northeast China. We examined its growth dynamics, analyzed the relationship between radical growth and climate factors, and explored the effects of global warming on the growth and distribution of P. tabuliformis. The results showed that tree-ring width chronologies of P. tabuliformis were negatively correlated with mean temperature of growing season (May-July), and positively correlated with precipitation and Palmer drought severity index (PDSI) in the early growing season (April) and in the growing season (May-July). Water availability was the main limiting factor for the radial growth of P. tabuliformis. Along the increasing precipitation gradient from southwest to northeast, tree growth became more sensitive to annual mean temperature, and the correlation with annual precipitation shifted from positive to negative, indicating that tree growth in the relative arid area (southwest of the study area) was more severely restricted by water availability. Drought stress caused by climate warming resulted in growth declines at some sites in the southwest area. With the continuous warming-drying climate, the distribution boundary of P. tabuliformis in the study area would shrink locally, with the suitable growth boundary moving northward.

[Effects of moisture and heat coupling on xylem growth of Pinus tabuliformis in Shenyang, China]. / 水热耦合对沈阳地区油松木质部生长的影响.

Based on the micro-core technology, we can accurately examine the tree cambium phenology and the radial growth at the cellular scale, and reveal the relationship between tree growth and climate. Pinus tabuliformis is one of the constructive species in forests of northern China. We investigated the growth pattern of P. tabuliformis in Shenyang and the changes in cambium and xylem cells throughout the growing season (April to November) in 2020. Results showed that the dividing activity in cambium started in early April and ended at the end of September. Xylem began to grow from the appearance of enlargement cells (mid April) to the end of the disappearance of lignified cells (late October), with a growth trajectory of 'S' shape curve. Approximately 53 xylem cells per row in radical direction were produced in 2020. The maximum growth rate (0.55 ind/row/day) occurred at the end of May, while the change of earlywood and latewood cells occurred at the end of July. When the minimum temperature above 0 ℃ in Shenyang, the cambium began to divide. The minimum critical temperature that affected the beginning and ending of xylem growth was 2-3 ℃. Precipitation promoted the growth in the growing season. The high temperature and insufficient water supply at the end of July were the main factors driving the differentiation of xylem cells to form earlywood and latewood.

[Tree species identification of wooden funeral utensil from Qing Dynasty's tombs and its potential of ecological and environmental indicator in Shenyang, Northeast China]. / æ²ˆé˜³æ¸ å¢“æœ¨è´¨è‘¬å ·çš„æ ‘ç§é‰´å®šåŠç”Ÿæ€çŽ¯å¢ƒçš„æŒ‡ç¤ºæ½œåŠ›.

The wood used for funeral utensil in ancient tomb is a kind of valuable materials and important for understanding vegetation, climate and society conditions in the history. Here, we identified the tree species and dated the time of wooden utensils for funeral excavated from tombs in Shuijia Village, Shenyang, using wood anatomy methods and dendrochronological techniques. The results showed that 7 out of the 16 wood samples were identified as Pinus tabuliformis from Pinaceae, 8 were Larix sp. from Pinaceae and most likely Larix olgensis, and the rest one was Acer sp. from Aceraceae. Currently, these tree species are still widely distributed in Liaoning Province, indicating that forest structure (tree species composition) is relatively stable and that the climate at that time was quite similar to that at present. The timbers used for wooden utensils of funeral for civilian tombs had regional biogeographic characteristics and reflected regional social productivity development level in Mukden (now Shenyang) in Qing Dynasty: most of them were native tree species with low cost and high availability; the main timber trees were conifer species, and a few of them were broadleaved trees. These timbers were likely from the forest in Shenyang or mountainous areas in Eastern Liaoning, with Hunhe River waterway being an important transport way for timbers to Shenyang. Some P. tabuliformis and Larix sp. timbers could be cross-dated well, and the growth period of the trees was determined to be 1680s-1770s (early to mid-Qing Dynasty). The variations of tree-ring width of these timbers had good consistency and high climate sensitivity, reflecting the consistency of regional climate and environment. These timbers have the potential to indicate the climate condition of the early to mid-Qing Dynasty.

[Altitudinal differentiation in the radial growth of Betula platyphylla and its response to climate in cold temperate forest: A case of Oakley Mountain, Northeast China].

Climate change has profound impacts on the structure and function of forest ecosystem. Under the background of climate warming, the growth patterns and climate responses of different species in different environments determine the development and stability of ecosystems. Using the method of tree chronology with ring width data of Betula platyphylla in Oakley Mountain of Daxing'an Mountains, we examined the relationship between the growth climate response of the pioneer B. platyphylla in larch forest and temperature rise and altitudinal changes. The results showed that climate warming resulted in the differentiation on B. platyphylla in different altitude. The radial growth of B. platyphylla increased significantly at the low altitude area (1050 m), while there were little changes at the relatively high altitude area (1250 m). Before the time of rapid warming (1980), the radial growth of B. platyphylla on two altitude areas were significantly stressed by low temperature in winter (October to February). During the period of rapid warming (1981-2010), low temperature stress in winter did not affect tree growth, with the growing season (May to July) temperature becoming the main limiting factors to the radial growth of B. platyphylla at the relatively high altitude areas. The growth of B. platyphylla increased in the low altitude stands with favorable water and heat conditions. The distribution of B. platyphylla may generally spread to high altitude sites in the study area under climate warming.

[Impacts of rapid warming on radial growth of Larix gmelinii on two typical micro-topographies in the recent 30 years]. / 近30å¹´å¿«é€Ÿå‡æ¸©å¯¹ä¸¤ç§å ¸åž‹å°åœ°å½¢ä¸Šå ´å®‰è½å¶æ¾å¾„å‘ç”Ÿé•¿çš„å½±å“.

Ravine and slope are the two typical micro-topographies in the Great Xing'an Mountains. Permafrost in the two micro-topographies is extremely sensitive to global warming. To compare the differences in responses of Larix gmelinii radial growth to rapid warming in the recent 30 years, tree-ring samples were collected from northern part of Great Xing'an Mountains in Inner Mongolia and tree ring-width chronologies were developed. The results showed that the divergence between tree growth and temperature occurred in 1980 in Mo'erdaoga and in 2000 in Hanma, respectively. Since 2000, tree growth on ravine sites was greater than that on the slope stands. Chronology of two topographies reached significant level by t test in 1984-2008, the Euclidean distance was 0.937-2.742 between chronologies, and far greater than the average (0.809-1.304). The rapid warming caused a significant radial growth response in L. gmelinii to hydrothermal conditions. On the slope sites, tree growth was mainly controlled by temperature and declined gradually in recent years, while the trees growing in ravines showed an accelerating growth rate with permafrost degeneration. L. gmelinii was undergoing profound environmental pressures caused by rapid warming, and it would experience a complex growth and development process. More seriously, L. gmelinii might disappear in China with a warming climate and permafrost degeneration.

[Vertical variability of Pinus sylvestris var. mongolica tree ring delta13C and its relationship with tree ring width in northern Daxing' an Mountains of Northeast China].

A measurement was made on the vertical direction tree ring stable carbon isotope ratio (delta13C) and tree ring width of Pinus sylvestris var. mongolica in northern Daxing' an Mountains of Northeast China, with the relationship between the vertical direction variations of the tree ring delta13C and tree ring width analyzed. In the whole ring of xylem, earlywood (EW) and bark endodermis, the delta13C all exhibited an increasing trend from the top to the base at first, with the maximum at the bottom of tree crown, and then, decreased rapidly to the minimum downward. The EW and late-wood (LW) had an increasing ratio of average tree ring width from the base to the top. The average annual sequence of the delta13C in vertical direction had an obvious reverse correspondence with the average annual sequence of tree ring width, and had a trend comparatively in line with the average annual sequence of the tree ring width ratio of EW to LW above tree crown. The variance analysis showed that there existed significant differences in the sequences of tree ring delta13C and ring width in vertical direction, and the magnitude of vertical delta13C variability was basically the same as that of the inter-annual delta13C variability. The year-to-year variation trend of the vertical delta13C sequence was approximately identical. For each sample, the delta13C sequence at the same heights was negatively correlated with the ring width sequence, but the statistical significance differed with tree height.

[Effects of elevated ozone on Pinus armandii growth: a simulation study with open-top chamber].

By using open-top chamber (OTC) and the techniques of dendrochronology, this paper studied the growth of Pinus armandii under elevated ozone, and explored the evolution dynamics and adaptation mechanisms of typical forest ecosystems to ozone enrichment. Elevated ozone inhibited the stem growth of P. armandii significantly, with the annual growth of the stem length and diameter reduced by 35.0% and 12.9%, respectively. The annual growth of tree-ring width and the annual ring cells number decreased by 11.5% and 54.1%, respectively, but no significant change was observed in the diameter of tracheid. At regional scale, the fluctuation of ozone concentration showed significant correlation with the variation of local vegetation growth (NDVI).

[Responses of Pinus tabulaeformis forest ecosystem in North China to climate change and elevated CO2: a simulation based on BIOME-BGC model and tree-ring data].

Based on BIOME-BGC model and tree-ring data, a modeling study was conducted to estimate the dynamic changes of the net primary productivity (NPP) of Pinus tabulaeformis forest ecosystem in North China in 1952-2008, and explore the responses of the radial growth and NPP to regional climate warming as well as the dynamics of the NPP in the future climate change scenarios. The simulation results indicated the annual NPP of the P. tabulaeformis ecosystem in 1952-2008 fluctuated from 244.12 to 645.31 g C x m(-2) x a(-1), with a mean value of 418.6 g C x m(-2) x a(-1) The mean air temperature in May-June and the precipitation from previous August to current July were the main factors limiting the radial growth of P. tabulaeformis and the NPP of P. tabulaeformis ecosystem. In the study period, both the radial growth and the NPP presented a decreasing trend due to the regional warming and drying climate condition. In the future climate scenarios, the NPP would have positive responses to the increase of air temperature, precipitation, and their combination. The elevated CO2 would benefit the increase of the NPP, and the increment would be about 16.1% due to the CO2 fertilization. At both ecosystem and regional scales, the tree-ring data would be an ideal proxy to predict the ecosystem dynamic change, and could be used to validate and calibrate the process-based ecosystem models including BIOME-BGC.

[Responses of Pinus sylvestris var. mongolica radial growth to climate warming in Great Xing' an Mountins: a case study in Mangui].

Based on the theory and methodology of dendrochronology, the tree ring width chronology of Pinus sylvestris var. mongolica in Mangui of Great Xing' an Mountains was developed, and the relationships between the standardized tree ring width chronology and local climate factors (temperature and precipitation) as well as the effects of climate factors on the P. sylvestris var. mongolica radial growth were analyzed. In this region, the mean monthly temperature in April-August of current year was the main factor limiting the radial growth, and the increasing mean monthly temperature from April to August had negative effects to the radial growth. The simulation of the variations of the radial growth by the mean monthly temperature change in April-August showed that the radial growth of P. sylvestris var. mongolica would present a declining trend accompanied with the warmer and drier regional climate condition.

[Larix gmelinii tree-ring width chronology and its responses to climate change in Kuduer, Great Xing' an Mountains].

Based on the established tree-ring width chronology of Larix gmelinii in Kuduer, Great Xing' an Mountains, this paper analyzed the relationships between L. gmelinii tree-ring width chronology and related climatic variables, including air temperature, precipitation, and PDSI. In the study area, the L. gmelinii tree-ring width chronology was significantly negatively correlated with the air temperature in May and July (P<0.01), had no significant correlation with precipitation, but significantly positively correlated with the PDSI in June-August (P<0.05), suggesting that hydro-thermal variables had significant coupling effects to the radial growth of L. gmelinii in its growth season, particularly in May and July. The L. gmelinii tree-ring width chronology had significant correlations with large scale climatic regimes such as the Pacific Decadal Oscillation (PDO) in both low and high frequency variations, illustrating the significant effects of the remote oceanic climatic regimes to the local tree growth.

[Effects of elevated O3 concentration on anti-oxidative enzyme activities in Pinus tabulaeformis].

An open-top chamber experiment was conducted to study the effects of high concentration O3 (80 nmol x mol(-1)) on the superoxide anion radical (O2*-) generation rate, hydrogen peroxide (H2O2) content, activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDHAR) and glutathione reductase (GR), and ascorbic acid content in Pinus tabulaeformis leaves. Under high concentration O3 exposure, the superoxide anion radical generation rate and H2O2 and malondialdehyde (MDA) contents increased, while the ascorbic acid content and the activities of SOD, APX, DHAR, MDHAR, and GR increased in early growth season but decreased then to a level lower than the control, which illustrated that the antioxidant system of P. tabulaeformis did respond in an acclimation way in the early growth season, but could not bear the damage of long-term elevated O3 exposure.

[Dendrochronology of Chinese pine in Mulan-Weichang, Hebei Province: a primary study].

Dendroclimatic methods were used to investigate the relationships between the growth of Chinese pine (Pinus tabulaeformis Carr.) and the climatic parameters in Mulan-Weichang of Hebei Province. The results showed that Chinese pine presented high sensitivity to climatic changes, and its earlywood width showed the highest sensitivity. There was a significant negative correlation between the tree-ring width chronology of Chinese pine and the air temperature in May-June. The precipitation and relative humidity in June had strong positive effects on the growth of earlywood, the precipitation from September to next September had significant positive effects on Chinese pine growth, and the relative humidity in winter more strongly affected the growth of latewood than of earlywood. There was a definite correlation between the tree-ring width chronology of Chinese pine and the large scale climate fluctuation. From 1951 to 2006, the increase of air temperature in study area was significant, and the sensitivity of Chinese pine to the variations of local temperature and precipitation decreased, presenting an inverse transforming trend with increasing temperature. Greater differences were observed between the reconstructed and observed data of mean temperature in May - June in a century scale, suggesting that the tree-ring growth of Chinese pine in study area had a greater fluctuation of sensitivity to the variation of climatic factors.

[Responses of Chinese pine tree ring in Shenyang suburb (Fu Mausoleum) to global temperature fluctuation].

In this paper, the correlations between the variations of Chinese pine (Pinus tabulaeformis Carr.) tree ring width in Shenyang suburb (Fu Mausoleum) and the local temperature variables, Global Surface Air Temperature Anomaly (GSATA) from 1880 to 2004, Global Land-Ocean Temperature (GLOTI) from 1880 to 2004 and North Hemisphere Temperature Anomaly (NHTA) from 1880 to 2004 were studied. Some close correlations were detected, and the local temperature variables, GSATA, GLOTI and NHTA had some similar influences on the Chinese pine tree ring width. The air temperature in last winter (December and January) and in spring (April and May) affected the growth of Chinese pine significantly (P < 0.05). There existed a 3-8-year periodicity of the variation of Chinese pine tree ring width and the GSATA, GLOTI and NHTA, and the 19.3-year and 23.2-year quasi-periodicity of the variation of Chinese pine tree ring width corresponded with the 20.8-year quasi-periodicity of GSATA, GLOTI and NHTA. This study suggested that the Chinese pine tree ring width in Shenyang Fu Mausoleum had positive correlations with global-scale temperature fluctuation, and the temperature increase in the past had a positive effect on the Chinese pine growth.

[Chinese pine tree ring width chronology and its relations to climatic conditions in Qianshan Mountains].

Taking Chinese pine in Qianshan Mountains as a sample, the tree ring width chronology including standard, residual, and Arstan chronologies was established. The results showed that the tree ring width of Chinese pine had a higher correlation with the temperature in May - July and in September - November, and significant positive correlations were observed between the tree ring width and the extreme minimum temperature in July and mean minimum temperature in September. The chronology had significant or very significant correlations with the extreme minimum temperature in December and next January, mean minimum temperature in January, annual precipitation, and the precipitation in April, May and last December. Chinese pine had stronger responses to the monthly/yearly water vapor pressure and relative humidity. The yearly and most monthly evaporation had negative effects on the growth, being most significant for the evaporation in April - July. The narrowed tree rings recorded by the chronology demonstrated the 30 times of extreme drought since 1 800. The growth of Chinese pine in Qianshan Mountains was also affected by the climate changes on global and hemisphere scales. There existed 11-, 23- and 50- year- common periodicity between the chronology and solar activity, and 10-, 20- and 45- year- common periodicity between the chronology and geomagnetic activity.