Table of Content

15 August 2022, Volume 33 Issue 8

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Special Features of Qinling ecosystem

Shrub layer structure and species diversity of warm temperate deciduous broadleaved forests of the Qinling Mountains Huangguan plot in China

GUO Xiang-yao, LUO Ying, YIN Qiu-long, YANG Zhi-chun, JIA Shi-hong, HAO Zhan-qing

2022, 33(8):  2017-2026.  doi:10.13287/j.1001-9332.202208.009

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Shrub is an important part of forest ecosystem. Exploring the species composition, structure and spatial distribution of shrub layer can lay an important foundation for further clarifying the mechanisms underlying species coexistence, biodiversity maintenance and community succession. In this study, species composition, spatial distribution, and species diversity of shrub layer were analyzed in 25 hm² of Huangguan forest plot. A total of 20716 individual shrubs (with 10463 branches) were recorded in the plot, belonging to 54 species, 45 genera, 28 families. The status of dominant species in the shrub layer was not obvious, with all the importance values being less than 10. The diameter structure of shrub layer vegetation was inverted ‘J' type. Shrubs showed aggregated distribution in the plot, with obvious altitude differences in spatial distribution. The diameter structure and spatial distribution of the nine shrub species with the largest abundance in the plot were consistent with the overall situation of shrub layer. With increasing altitude, the Shannon diversity index (H) and Simpson dominance index (D) did not change significantly, while the Pielou evenness index (E) decreased. Those indices decreased with the increases of the abundance of dominant species in tree layer, and E increased with the increase of the number of dominant species in sub-tree layer. The indices of H, D, E were significantly negatively correlated with soil total phosphorus (TP). The H index was significantly positively correlated with soil pH, and the E index was significantly positively correlated with soil total potassium. The shrub layer was rich in species, stable in community structure and well regenerated. The species diversity of shrub layer was mainly affected by the number of dominant species in the tree layer, soil pH, and TP.

Spatial distribution patterns and intraspecific and interspecific associations of dominant shrub species Lonicera fragrantissima var. lancifolia in Huangguan of Qinling Mountains, China

HAN An-xia, QIU Jing, HE Chun-mei, YIN Qiu-long, JIA Shi-hong, LUO Ying, LI Chen-lu, HAO Zhan-qing

2022, 33(8):  2027-2034.  doi:10.13287/j.1001-9332.202208.003

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In this study, the spatial distribution patterns of individuals with different diameter classes of dominant shrub Lonicera fragrantissima var. lancifolia and the intraspecific and interspecific relationships were analyzed in Qinling Huangguan Plot. The results showed that the diameter class structure of L. fragrantissima var. lancifolia showed a pyramid shape, with a wide bottom and a narrow top. The number of small-diameter class individuals was the largest, showing a good state of renewal and a stable growth, which was conducive to community renewal and succession. Based on Ripley's K function, using univariate and bivariate paired correlation functions, under complete spatial randomness model, heterogeneous Poisson model and antecedent condition model, all individual of the species and their diameter-dividing classes were mainly aggregated, and the aggregation degree decreased with the increases of research scale, and gradually tended to random distribution. Affected by habitat heterogeneity, diffusion restriction and negative density dependence, there was a positive correlation among different intraspecific dia-meter classes, and also a certain degree of no correlation, but without negative correlation. The interspecific relationship was complex. All types of association (no, positive and negative) were observed, but negative association and no association were dominated.

Spatial distribution pattern and intraspecific association of dominant species Quercus aliena var. acu-tiserrata in Qinling Mountains, China

QIU Jing, HAN An-xia, HE Chun-mei, YIN Qiu-long, JIA Shi-hong, LUO Ying, LI Chen-lu, HAO Zhan-qing

2022, 33(8):  2035-2042.  doi:10.13287/j.1001-9332.202208.002

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To explore the spatial distribution and intraspecific correlation of Quercus aliena var. acutiserrata, a domi-nant tree species in a 25 hm² plot of warm temperate deciduous broadleaved forest in Qinling Mountains, the pair-correlation function g(r) was used to study the spatial pattern and intraspecific association. The results showed that the diameter class structure of Q. aliena var. acutiserrata was bimodal, with a large proportion of young trees (1 cm≤DBH＜5 cm), indicating an increase population structure with good capability of regeneration. The abundance of middle trees (15 cm≤DBH＜25 cm) was slightly more than that of big trees (25 cm≤DBH＜35 cm) and old trees (DBH≥35 cm), but far less than that of young trees and small trees. The spatial distribution of Q. aliena var. acuteserrata was obviously altitude dependent, which mainly distributed in the middle and high altitude areas. Results of complete spatial randomness (CSR) model analysis showed that young trees, small trees, adult trees, big trees, and old trees were aggregated in the large scale (＜60 m). Heterogeneous Poisson (HP) model was used to eliminate habitat heterogeneity. The results of HP model showed that the individual aggregation degree of each diameter class decreased, indicating that the distribution was affected by habitat heterogeneity. At the small scale (＜40 m), spatial correlation was positively correlated between individuals with small diameter gap, whereas the spatial correlation was negative correlation and no correlation between individuals with large diameter gap. At large scale (>40 m), the spatial correlation was positively correlated between large-diameter individuals, but negatively correlated and unrelated between saplings and other diameter individuals. Our results indicated that biological cha-racteristics of Q. aliena var. acutiserrata and habitat heterogeneity were important drivers for the formation of population spatial pattern.

Responses of radial growth of Pinus tabuliformis to climate change at the northern slopes of Qinling Mountains, China

LI Ying-hui, QI Gui-zeng, FENG Rong-rong, LIU Kang

2022, 33(8):  2043-2050.  doi:10.13287/j.1001-9332.202208.040

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A standard chronology (STD) was established with Pinus tabuliformis samples collected from Nanwutai at the northern slopes of the Qinling Mountains. The correlations between radial growth of P. tabuliformis and climatic factors were explored. The results showed that radial growth was positively correlated with moisture factors in previous September and current May. The radial growth was positively correlated with temperature factors in pre-vious November and negatively with that in previous October and current May. There was significant lag effect of climatic factors on the radial growth. The radial growth of P. tabuliformis was well correlated with the PDSI drought severity index, with positive correlations being identified from September to December of the previous year and in May of the current year. The regression model was able to simulate the relationship between STD and PDSI. The formations of extremely wide and narrow tree-ring were mainly a result of drought condition. Combined with climatic factors, PDSI could better reflect the radial growth characteristics of P. tabuliformis.

Nutrition diagnosis and fertilization of Pinus armandii forest in the Qinling Mountains, China

DONG Zhen-jie, GUO Ya-ru, HOU Lin

2022, 33(8):  2051-2056.  doi:10.13287/j.1001-9332.202208.001

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We examined the contents of total nitrogen (TN) and total phosphorus (TP) in needle, litter, and soil of Pinus armandii forest on the southern slope of the Qinling Mountains in Shaanxi, China. We conducted nutrition diagnosis of P. armandii forest, analyzed nutrient limitation pattern, the fertilization types and amount to increase growth, to provide support for precision fertilization and scientific cultivation of big timber of P. armandii. The results showed that the proportion of big timber (DBH>26 cm) and individuals with the potential to grow into big timber (18 cm<DBH≤26 cm) was 29.0% and 60.6%, respectively. The needle N and P contents were 12.65 and 1.34 g·kg^-1, respectively, and the N:P was 10.24 (<14, unrestricted threshold of forest growth). The N and P resorption efficiency of needle was 33.8% and 48.0%, respectively. In 0-10 cm soil layer, soil N and P contents were significantly negatively correlated with that in the needle, but positively correlated with that in litter. The relationship between the needle N:P and soil N storage was expressed by a quadratic function. The growth of P. armandii was N limited, and an addition rate of 0.42 t N·hm^-2 would ensure normal growth of all individual trees. We recommended the rate of 0.16 t N·hm^-2 to the trees with the potential to grow into big timber to promote them to be big timber in a short period, allocating nitrogen to individual plants in proportion to the biomass of individual trees in the stand per unit area.

Spatial and temporal variations of ecosystem service synergy and trade-off in Qinling Mountains, China

WANG Xi, MU Qi, LUO Man-ya, ZHAO Yong-hua, YANG Shu-yuan, ZHANG Lei, QU Zhi

2022, 33(8):  2057-2067.  doi:10.13287/j.1001-9332.202208.019

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The Qinling Mountains are an important ecological function area in China. Exploring the trade-offs and synergies of ecosystem services is important for ecological protection and sustainable development in the Qinling Mountains. In this study, we analyzed the spatio-temporal variations of land uses in the Qinling Mountains in 2000, 2010 and 2020 based on remote sensing, meteorological, and soil texture data. The amounts of carbon sequestration, water yield, habitat quality, and soil conservation were calculated with CASA, InVEST and RUSLE models. The relationships between its spatially heterogeneous characteristics and various ecosystem services were analyzed. The results showed that, from 2000 to 2020, the area of arable land and grassland in the study area continued to decrease, the area of forest and building land increased, and the change of water body and unused land was not noticeable. Carbon sequestration was high in the east and low in the west, with an increasing trend. Water production continued to decrease, showing a tendency of higher on the south slope and lower on the north slope. Habitat quality increased steadily, while soil conservation increased and then decreased. Ecosystem services varied across land classes and across ecosystems in the same land class. In general, there was a synergistic relationship between carbon sequestration and soil conservation, habitat quality and soil conservation, carbon sequestration, and habitat quality. There was trade-off between carbon sequestration and water production, soil conservation and water production, habitat quality, and water production. There were significant differences in the relationship between service volumes under different conditions. The results could reduce the risk of trade-offs and maximize overall benefits, and provide a reference for promoting ecologically high-quality development and achieving a win-win situation for natural resource management and human well-being.

Original Articles

Temporal variation and influencing factors of albedo in a deciduous broad-leaved forest

RUAN Ying, WANG Chuan-kuan, LIU Fan, WANG Xing-chang

2022, 33(8):  2068-2076.  doi:10.13287/j.1001-9332.202208.011

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In situ measurement of albedo is important for estimating ecosystem energy budget and its remote sensing application. However, the measurement method of albedo on sloping land is limited and the difference in temporal variation in albedo between visible and near-infrared bands remains unclear. Taking a deciduous broad-leaved forest at the Maoershan Forest Ecological Station in Northeast China as an example, we explored the temporal variation and influencing factors of albedo for three bands: incident and reflected solar radiation (SR, 300-2800 nm), photosynthetically active radiation (PAR, 400-700 nm), and near infrared radiation (NIR, 700-2800 nm). The temporal difference in albedo measurements between the two installation methods of radiometers was analyzed. The results showed that, in sunny days, the diurnal variation in SR and NIR albedo had an asymmetric U-shaped curve around the local noon, while PAR increased from sunrise to sunset. In cloudy days, the albedo decreased sharply and then tended to be stable. The measurement with parallel sensors to the slope increased the daily mean value of albedo, but reduced the daily asymmetry of SR and NIR. For the whole growing season, the maximum albedos of SR, NIR and PAR in horizontal measurement were 0.16, 0.27 and 0.11, respectively, and the minimums were 0.07, 0.11 and 0.03, respectively. Albedo in the SR and NIR wavebands increased first and then decreased (the peak value was in July), while PAR showed a contrasting pattern. SR albedo was mainly controlled by NIR rather than PAR. The contribution of the influencing factors was ranked in the order of normalized difference vegetation index (61.7%-78.5%, representing leaf area index) > solar altitude angle (15.4%-36.9%) > clearness index (0.4%-36.9%).

Structure and dynamics of co-dominant species in different succession stages of natural forests in Daxing'an Mountains, China

DONG Ling-bo, MA Rong, TIAN Dong-yuan, WANG Tao, LIU Zhao-gang

2022, 33(8):  2077-2087.  doi:10.13287/j.1001-9332.202208.013

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Affected by the disturbance of forest fire and logging, the primary forest in Daxing'an Mountains gradually degenerates into secondary forest. In this study, we established 16 plots in each of three typical forests, including natural Betula platyphylla pure forest (pioneer stage), natural B. platyphylla and Larix gmelinii mixed forest (transition stage) and natural L. gmelinii pure forest (top stage). The methods of population age and tree height structure, static life table, survival analysis, dynamic index and time series prediction were used to quantitatively analyze the dynamics of dominant species (B. platyphylla and L. gmelinii) and all the arbors, aiming to provide scientific basis for the restoration and development of natural L. gmelinii forest. The results showed that the abundance of young co-dominant species and total arbors in each stage was large, and that all population had strong self-renewal potential. With the progress of succession, the abundance of B. platyphylla in each age class gradually decreased, whereas that of L. gmelinii gradually increased. The mortality and disappearance rates of total arbors and B. platyphylla in the transition stage and L. gmelinii in the pioneer stage gradually increased with the increases of age class, and the survival curve was Deevey-Ⅰ type. The survival analysis results showed that the population was stable in the early stage, increased in the middle stage, and declined in the later stage. In other stages, the mortality rates fluctuated slightly, the survival curves were Deevey-Ⅱ type, and the population increased in the early stage, declined in the middle stage, and stable in the later stage. The co-dominant species and total arbors were growing in the three succession stages, among which B. platyphylla in the pioneer stage, L. gmelinii and total arbors in the top stage showed the lowest sensitivity to the environment. The results of time series prediction showed that the co-dominant species and total arbors in each stage would increase in the future. During forest succession, it was necessary to strengthen the protection of seedlings and young trees, thin the forest with large coverage, and take appropriate measures to ensure population renewal.

Spatial structure characteristics of plain ecological plantation in Tongzhou District, Beijing, China

CUI Cheng-cheng, ZHA Tong-gang, ZHANG Xiao-xia, CHEN Yu-jia, GAO Lian-wei, BAI Ling-ran, MA Zi-ao, YU Yang

2022, 33(8):  2088-2096.  doi:10.13287/j.1001-9332.202208.007

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Forest spatial structure (FSS) directly reflects resource competition and growth space distribution among different trees. The characteristics of FSS play an important role in mastering the growth status of ecological forest, formulating stand structure regulation measures, and improving forest quality and ecological services. In this study, seven plain ecological plantations including Pinus tabuliformis, Fraxinus chinensis, Salix matsudana, Populus tomentosa, Sophora japonica, Robinia pseudoacacia, and Salix babylonica in Tongzhou District, Beijing were selected as the research objects. The spatial structure characteristics of plain ecological plantations were evaluated by aggregation degree, angle index, neighborhood comparison, open degree, canopy index, competition index, edge benefit, and spatial structure comprehensive index. The horizontal distribution pattern of stand was well, with the aggregation degree of 0.32-1.41, the angle index of 0.4, and the neighborhood comparison mainly around 0.5. The vertical distribution pattern of stand was not well and needed to be improved, with the open degree of 0.19-0.52, most canopy indexes of about 0.7. The competition index presented a high competitive status with the all values of >50. Except the comprehensive evaluation index of R. pseudoacacia plantation presented in grade Ⅲ, the other six kinds of plain ecological plantations fell to grade Ⅱ, with low stand openness and low vitality. The comprehensive evaluation indices of FSS followed the order of R. pseudoacacia > S. babylonica > P. tabuliformis > S. matsudana > F. chinensis > S. japonica > P. tomentosa.

Responses of radial growth of Juniperus przewalskii to different droughts over the northeastern Tibetan Plateau, China

XU He-nian, WANG Jiang-lin, PENG Xiao-mei, REN Zi-jian

2022, 33(8):  2097-2104.  doi:10.13287/j.1001-9332.202208.006

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To study the responses of radial growth of Juniperus przewalskii to climate factors of the different periods (pre-growing season (February-April), growing season (May-July)), and the vulnerability (resistance, R_T; recovery, R_C) of J. przewalskii to different drought events (precipitation, temperature and the both caused), we used tree ring width data of J. przewalskii from 17 sampling sites across the northeastern Tibetan Plateau to analyze the correlation between radial growth and climate factors of different periods, and the vulnerability in different drought events. The results showed that radial growth of J. przewalskii had significant positive correlation with drought index and negative correlation with temperature in the growing season (P<0.1). The vulnerability of J. przewalskii to drought events of different periods had significant difference. In the pre-growing season drought events, the R_T of J. przewalskii at low altitude was 2.3% higher than that at high altitude, the R_C of J. przewalskii at low altitude was 25.1% lower than that at high altitude. For drought events in the growing season, the R_T of J. przewalskii at low altitude was 23.7% lower than that at high altitude, the R_C of J. przewalskii at low altitude was 107.1% higher than that at high altitude. The mean R_C(1.68) of J. przewalskii in precipitation-caused drought events was strong, while the mean R_T(1.43) of J. przewalskii in temperature-caused drought events was strong. The growth of J. przewalskii, especially for that at low altitude, would be largely limited by drought caused by global warming in the future.

Response of vegetation productivity to drought in the Qinling-Daba Mountains, China from 2001 to 2020

WANG Xiao-hong, LIU Xian-feng, SUN Gao-peng, LIANG Juan

2022, 33(8):  2105-2112.  doi:10.13287/j.1001-9332.202208.021

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To quantitatively evaluate the effects of drought on vegetation productivity in the Qinling-Daba Mountains, we analyzed the temporal and spatial characteristics of gross primary productivity (GPP) and drought, identified the fluctuation of negative GPP extremes under different vegetation types, and quantified the drought vulnerability and drought risk of GPP from 2001 to 2020 with MODIS GPP products and standardized precipitation evapotranspiration index (SPEI). The results showed that the annual GPP from 2001 to 2020 had an increasing trend in 98.0% of areas in the Qinling-Daba Mountains. The GPP of all vegetation types except wetlands increased significantly. SPEI decreased in 23.8% of area in the Qinling-Daba Mountains from 2001 to 2020. The number of negative GPP extremes had no significant trend, but abnormal GPP fluctuations had intensified, especially in the cultivated land. After 2011, the proportion of concurrent negative GPP extreme and drought had decreased for all vegetation types, but the spatial and temporal range of drought in these negative GPP extremes showed an expanding trend. Compared with the pattern during 2001-2010, the proportion of area with positive drought vulnerability and drought risk increased by 104.1% and 6.7% after 2011, indicating that the area with drought-induced GPP decline had expanded. Among all the vegetation types, drought caused the largest decrease of GPP in wetlands. The results revealed that drought led to an aggravation of GPP fluctuations and increased frequency of GPP extremes in the Qinling-Daba Mountains from 2001 to 2020, which resulted in GPP decline with different magnitudes in most vegetation types.

Litter storage and water-holding capacity of typical forests in mountainous area of Southwest China

LIU Yan-ping, WANG Gen-xu, HU Zhao-yong, GUO Lin-mao

2022, 33(8):  2113-2120.  doi:10.13287/j.1001-9332.202208.014

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Current studies on water conservation capacity of litter in the mountainous area of Southwest China (MASC) mainly focus on local scale. Such results are difficult to evaluate the storage and water-holding capacity of litter in the whole MASC. In this study, the results of site-scale research in the MASC from 2004 to 2021 were collated (a total of 16 research sites and 70 data), as well as the storage and water-holding characteristics of litters of three typical forests in the MASC were compared and analyzed. The results showed that the water-holding processes of litter in coniferous forest, broadleaved forest and mixed forest were similar, which could be divided into three stages: rapid water absorption, gradual slowing, and stable. The absorption rate and duration of different forests were different in each stage. The broadleaved forest had the fastest water absorption rate, while coniferous forest had the slowest with the longest duration to reach stability. There was no significant difference in litter storage among diffe-rent forest types. The total litter storage of coniferous forest, broadleaved forest and mixed forest ranged from 8.26 to 8.82 t·hm^-2. The significant spatial variations of litter storage in semi-decomposed layer resulted in that of total litter storage. The total maximum water-holding capacity of litters of the three forests ranged from 17.85 t·hm^-2 to 19.87 t·hm^-2, and the maximum water-holding rate of litter ranged from 200.6% to 228.0%. There was a positive correlation between the maximum water-holding capacity and litter storage in different forests. The total effective retention capacity of three forest litters ranged from 11.66 to 12.29 t·hm^-2, while the total effective retention rate of three forests ranged from 128.1% to 145.2%. There were no significant differences in litter storage and water holding capacity among three forest types with two decomposition degrees in MASC.

Dissolved organic matter dynamics and spectral characteristics of twig litter from different Castanopsis carlesii forests in the middle subtropical region, China

WEI Wen-tao, NI Xiang-yin, YUE Kai, GUO Hong-rong, WU Ruo-bing, ZHU Ling, WU Fu-zhong

2022, 33(8):  2121-2128.  doi:10.13287/j.1001-9332.202208.005

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To assess the dynamics and spectral characteristics of dissolved organic matter of twig litter in continuous increase stage, peak stage, and continuous decrease stage of twig litter production in different types of Castanopsis carlesii forest in middle subtropical China, a field experiment was conducted in C. carlesii natural forest, secondary forest and plantation. The results showed that litter production stage and forest type significantly affected the content and spectral characteristics of dissolved organic matter of twig litter were . Compared with the secondary forest and plantation, natural forest had higher dissolved organic carbon (DOC) content and lower special ultraviolet-visible absorption values at 254, 260 and 280 nm (SUVA₂₅₄, SUVA₂₆₀, SUVA₂₈₀) at the continuous decrease stage of twig litter production, indicating high twig litter quality of natural forest and high cycling efficiency with dissolved organic matter in the natural forest at this stage. In contrast, the higher contents of total nitrogen (TN), total phosphorus (TP), total dissolved nitrogen (TDN), total dissolved phosphorus (TDP), and lower DOC:TDP and TDN:TDP ratios of twig litter in the plantation were observed at the peak stage of twig litter production, while no differences were detected in dissolved organic matter contents and spectral values in the secondary forest among the stages. In addition, the DOC, TDN, TDP of twig litter were negatively correlated with temperature and precipitation in the natural forests and secondary forests, but TDN and TDP of twig litter were positively correlated with temperature and precipitation in the plantations. These results suggested that the higher nutrient content at the peak stage of twig litter production in the C. carlesii plantation might lead to more efficient material cycling and that there would be a higher efficiency of material cycling for twig litter dissolved organic matter in C. carlesii natural forest at reduction stage of twig litter production.

Responses of chlorophyll fluorescence and non-structural carbohydrate accumulation of Castanopsis kawakamii seedlings to seed dispersal positions

ZHU Jing, JIN Xing, HE Zhong-sheng, XIAO Qian-ru, CHEN Jia-jia, XING Cong, LIU Jin-fu, SHEN Cai-xia

2022, 33(8):  2129-2138.  doi:10.13287/j.1001-9332.202208.008

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When seeds fallen from the mother trees, their initial contact physical environment was litter or soil. The dispersal positions of seeds (seeds positioned on top of the litter, the soil surface and beneath the litter) determine the process of their natural regeneration. We simulated three different dispersal positions of Castanopsis kawakamii, including seeds positioned on top of the litter (2 and 4 cm litter was placed below the seed layer), soil surface (without litter), and seeds beneath the litter (2, 4, 6 and 8 cm litter covers in the upper layer of seeds). We examined the effects of seed dispersal position on the chlorophyll fluorescence characteristics, non-structural carbohydrate, specific leaf area, leaf dry matter content and nutrient content of seedlings. The results showed that leaf nitrogen content per area of seedlings had significantly positive correlation with soluble sugar content, non-structural carbohydrate content, and negative correlation with specific leaf area across different dispersal positions. Seedlings of the moderate litter cover (2 and 4 cm) adopted resource acquisitive strategies by increasing relative chlorophyll content, soluble sugar content, non-structural carbohydrate content, leaf dry matter content, leaf nitrogen content and phosphorus contents per area, and decreasing specific leaf area to achieve their demands for rapid growth. Seedlings grew on soil surface and beneath the deep litter (6 and 8 cm) adopted the resource conservative strategies with higher leaf nitrogen content per mass and specific leaf area, lower leaf dry matter content, and non-structural carbohydrate content to intercept more effective light resources to compensate for the shady environment brought by deep litter. This would further decrease the probability of seedling mortality due to ‘carbon starvation'. Seedlings under litter layer stored starch in leaf, and reduced the energy consumption of photosynthetic tissues (low PSⅡ maximum photochemical efficiency) to maintain seedling growth. Comprehensive analysis of entropy method indicated that low amount of litter cover (2 cm) significantly promoted seedling growth of C. kawakamii. In the future, we could regulate the thickness of litter layer to promote the growth and regeneration of C. kawakamii seedlings in natural forest.

Climate changes in southern Taihang Mountain area from 1980 to 2019

HUANG Hui, ZHENG Chang-ling, ZHANG Jin-song, MENG Ping

2022, 33(8):  2139-2145.  doi:10.13287/j.1001-9332.202208.025

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Southern Taihang Mountain area is an important part of the key ecological regions along the Yellow River in China. Understanding the climate change trend in this area is of significance for the maintenance of ecological security and the planning and decision-making of major ecological projects in the Yellow River Basin. Taking Jiyuan City in southern Taihang Mountain area as the research area, we analyzed the climate change trend in Jiyuan based on the meteorological data from 1980 to 2019. The results showed that climate in Jiyuan tended to be warmer and wetter during the study period. The change rates of temperature and precipitation were 0.48 ℃·(10 a)^-1 and 14.21 mm·(10 a)^-1, respectively. The rise of temperature in spring and summer was higher than that in autumn and winter. Climate was warmer and drier in spring, while warmer and wetter in the other three seasons. Potential evapotranspiration and aridity index showed increasing and decreasing trends, with the average value of 748 mm and 1.36, respectively. The first and last days ≥10 ℃ were about 3 days in advance and 1 day in delay every 10 years. The change rate of effective accumulated temperature ≥10 ℃, duration days ≥10 ℃ and high temperature days were 116.57 ℃·(10 a)^-1, 4 d·(10 a)^-1, and 5 d·(10 a)^-1, respectively. The 1990s was the driest decade in Jiyuan during the study period, with strongest increases of temperature. Half of the years showed the characteristics of semi-arid climate in that decade. From 2010 to 2019, the trend of climate warming and wetting in Jiyuan had accelerated significantly, which was the warmest and wettest decade. In recent 10 years, duration days ≥10 ℃ and the effective accumulated temperature increased by about 28 days and 389.36 ℃, respectively. The frequency and intensity of high temperature weather also increased significantly in this decade.

Effects of management on the content and spectral characteristics of soil dissolved organic carbon in a subtropical forest

YU Heng, XU Chao, ZHANG Wen-qiang, ZHOU Jia-cong, CHEN Shi-dong, XIONG De-cheng, LIU Xiao-fei, YANG Zhi-jie

2022, 33(8):  2146-2152.  doi:10.13287/i.1001-9332.202208.012

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The differences of artificial measures, such as logging residue management, between assisted natural regeneration and afforestation may change the content and structure of soil dissolved organic carbon (DOC) and affect forest carbon cycle. In this study, we investigated the effects of managements on the content and spectral characteristics of DOC in a subtropical forest, which contained the forest of assisted natural regeneration (Ⅱ), and the plantation (Ⅲ), both were converted from mature secondary forests (Ⅰ). Results showed that DOC content in the 0-10 cm soil layer was significantly decreased by 21% and 50% in Ⅱ and Ⅲ, respectively, compared with that in Ⅰ. The DOC/SOC (soil organic carbon) ratios of 0-10 cm and 10-20 cm soil layers were significantly decreased by 27% and 43% after the conversion, respectively. In the 0-10 cm soil layer, the aromatic index and humification index of DOC in Ⅱ were significantly higher than that in Ⅲ. The infrared absorption ratio of soil DOC in the range of 3700-3000 cm^-1, 1650-1620 cm^-1, 1160-1000 cm^-1, and 690-530 cm^-1 in Ⅱ was higher than that in Ⅲ, indicating that the DOC in Ⅱ had higher carboxylic acids and aromatic substances than Ⅲ. The fluorescence index of DOC in Ⅱ and Ⅲ ranged from 1.4 to 1.9, and the biological index of Ⅱ was significantly higher than that of Ⅲ, indicating that Ⅲ had higher protein components in DOC and being more bioavailable. Thus, the differences of the content and structure of DOC between Ⅱ and Ⅲ might cause higher soil carbon pool of Ⅱ than that of Ⅲ.

Responses of plant community diversity to human disturbance in temperate grassland with different soil parent materials

HOU Xing-chen, LU Shao-wei, XIANG Chang-lin, LI Shao-ning, ZHAO Na, XU Xiao-tian

2022, 33(8):  2153-2160.  doi:10.13287/j.1001-9332.202208.015

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Based on community investigation data from grasslands on two different soil parent material types (loess and sand parent materials) and under three human utilization modes in the Saihan Ullah Reserve, we calculated human disturbance index (HDI) and biodiversity indices and analyzed the interactions between species diversity and degradation levels. The results showed that degradation status varied across different soil parent material types and human utilization modes, and that degradation levels of loess and sand parent materials both increased with the enhancement of human utilization intensification. HDI of loess parent material grasslands (mean value of 1.21) was lower than sand parent material grasslands (mean value of 1.48) in the same human utilization. Biodiversity indices declined with soil sandy degree and the utilization intensification. The mean values of Margarlef richness index, Shannon diversity index, Simpson dominance index and Pielou evenness index were between 1.57-4.27, 1.16-2.39, 0.76-0.87, and 0.71-0.80, respectively. The Margalef richness index, Shannon diversity index and Simpson dominance index decreased with increasing HDI, while Pielou evenness index increased. Overgrazing could lead to serious threat on both grasslands with soil parent material types, and the optimum utilization mode of loess and sand parent material grasslands were enclosure with mowing and seasonal grazing. In the future works of biodiversity conservation, it is important to consider the influence of both different soil patent material and human utilization modes of grassland. It is urgent to develop different utilization modes for grassland under different soil parent material types, which would enhance the matchness of grassland restoration and management with local conditions.

Interannual variations in natural abundance of nitrogen stable isotopes in soil and plant and their implications in a meadow steppe

WANG Bin, WANG Ru-zhen, ZHANG Ying, GU Bai-tao, LI Tian, ZHANG Yu-ge, JIANG Yong

2022, 33(8):  2161-2170.  doi:10.13287/j.1001-9332.202208.016

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Nitrogen is the most limiting nutrient for ecosystems. The natural abundance of δ¹⁵N (¹⁵N/¹⁴N) can efficiently indicate ecosystem nitrogen cycling processes. We investigated the interannual variations in natural abundance of δ¹⁵N in soil-plant system and soil net nitrogen mineralization in a meadow steppe of Inner Mongolia. Results across the four sampling years (2017-2020) showed that the content of soil NO₃^--N (9.83-14.79 mg·kg^-1) was significantly higher than that of NH₄⁺-N (3.92-5.00 mg·kg^-1) and that δ¹⁵N value of soil NH₄⁺ (13.3‰-18.3‰) was significantly higher than that of NO₃^-(3.76‰-6.14‰). The δ¹⁵N value of soil NO₃^- was negatively correlated with soil NO₃^- content. The δ¹⁵N value of soil NH₄⁺ was relatively higher in the dry years, while the δ¹⁵N value of soil NO₃^- significantly decreased in the wetter and drier years. Soil net mineralization and ammonification rates were significantly higher in the dry years than that of the wet years, while soil nitrification rates showed no correlation with annual precipitation. The δ¹⁵N values of plants were not related to that of soils, but nega-tively correlated with plant nitrogen content. Both δ¹⁵N values and nitrogen contents were significantly and positively correlated between the leguminous and non-leguminous plants, suggesting that legume could facilitate nitrogen uptake of non-leguminous plants. These results could provide supporting data for nitrogen cycling and their responses to changes in precipitation in grassland soil-plant systems.

Responses of leaf functional traits of clonal plant Phragmites australis to heterogeneous environments

ZHOU Yi, JIAO Liang, QIN Hui-jun, WU Jing-jing, CHE Xi-chen

2022, 33(8):  2171-2177.  doi:10.13287/j.1001-9332.202208.010

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The spatial variation of leaf functional traits in Phragmites australis could reflect the changes of resource allocation. The coupling relationship between leaf functional traits and soil environmental factors represents the ecological adaptation strategies of clonal plants to heterogeneous environments. The research object clonal plant, P. australis, was selected from an inland wetland in northwest China. We examined leaf functional traits of P. australis and their responses to soil environmental factors in wetland, salt marsh, and desert habitats. The results showed that from wetland to desert habitat, foliar contents of C, N and P decreased by 7.2%, 40.0% and 64.1%, respectively, and N and P use efficiency increased, leaf length, leaf width, leaf area, leaf dry weight, specific leaf area and leaf thickness showed a decreasing trend. The coevolution of leaf functional traits was observed, indicating a significant correlation between leaf nutrient elements and specific leaf area. Soil bulk density, salinity, and water availability were the most important environmental factors driving the variation of leaf functional traits of P. australis in wetland, salt marsh and desert habitats, respectively.

Effects of nitrogen addition on the kinetic parameters of soil acid phosphomonoesterase in a Moso bamboo forest

ZENG Quan-xin, YUAN Xiao-chun, ZHOU Jia-cong, WU Jun-mei, LI Wen-zhou, LIN Hui-ying, ZHANG Xiao-qing, CHEN Yueh-min

2022, 33(8):  2178-2186.  doi:10.13287/j.1001-9332.202208.018

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Soil phosphatases are important in the mineralization of organophosphates and in the phosphorus (P) cycle. The kinetic mechanisms of phosphatases in response to nitrogen (N) deposition remain unclear. We carried out a field experiment with four different concentrations of N: 0 g N·hm^-2·a^-1(control), 20 g N·hm^-2·a^-1(low N), 40 g N·hm^-2·a^-1(medium N), and 80 g N·hm^-2·a^-1(high N) in a subtropical Moso bamboo forest. Soil samples were then collected from 0 to 15 cm depth, after 3, 5 and 7 years of N addition. We analyzed soil chemical properties and microbial biomass. Acid phosphatase (ACP) was investigated on the basis of maximum reaction velocity (V_m), Michaelis constant (K_m), and catalytic efficiency (K_a). Results showed that N addition significantly decreased soil dissolved organic carbon (DOC), available phosphorus, and organophosphate content, but significantly increased soil ammonium, nitrate-N content, and V_m. There was a significant relationship between V_m and the concentrations of available phosphorus, organophosphate, and soil DOC. In general, N addition substantially increased K_a, but did not affect K_m. The K_m value in the high N treatment group was higher than that in the control group after five years of N addition. K_m was significantly negatively associated with both available phosphorus and organophosphate. Medium and high N treatments had stronger effects on the kinetic parameters of ACP than low N treatment. Results of variation partition analysis showed that changes in soil chemical properties, rather than microbial biomass, dominated changes in V_m(47%) and K_m(33%). In summary, N addition significantly affected substrate availability in Moso bamboo forest soil and modulated soil P cycle by regulating ACP kinetic parameters (especially V_m). The study would improve the understanding of the mechanisms underlying soil microorganisms-regulated soil P cycle under N enrichment. These mechanisms would identify the important parameters for improving soil P cycling models under global change scenarios.

Effects of attapulgite addition on soil evaporation and crack characteristics

YANG Ting, XING Xu-guang, MA Xiao-yi

2022, 33(8):  2187-2195.  doi:10.13287/j.1001-9332.202208.020

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Water is one of the most important factors limiting vegetation recovery and agricultural development in arid and semi-arid areas. The reduction of ineffective soil evaporation can improve soil water use efficiency. As a kind of clay mineral, attapulgite (ATP) plays a critical role in limiting soil evaporation due to its hydrophilicity and adsorption. In this study, three typical soils with different textures (dark loessial soil, cultivated loess soil, and sandy soil) were selected from the arid and semi-arid area of the Loess Plateau, and five ATP additions (0%, 1%, 2%, 3% and 4%) were set for conducting soil evaporation experiments under natural conditions using micro-evaporators to investigate the effects of ATP addition on different soil evaporation processes and the characteristics of evaporation surface cracks. The results showed that the cumulative evaporation and evaporation loss ratio of the same soil decreased with the increases of ATP addition when the ATP addition was <3%. When ATP was added at 3%, the cumulative evaporation and evaporation loss ratio of dark loessial soil and sandy soil decreased, while those of cultivated loess soil increased. When ATP was added at 4%, the cumulative evaporation decreased and the evaporation loss ratio increased for dark loessial soil, the cumulative evaporation increased and the evaporation loss ratio decreased for sandy soil, and the cumulative evaporation and evaporation loss ratio decreased for cultivated loess soil. The average cumulative evaporation of different soils followed an order of dark loessial soil > cultivated loess soil > sandy soil. Soil water content of ATP treatment was consistently higher than that of control throughout the whole evaporation process in the same soil. Simulations of cumulative evaporation versus the square root of time indicated that the amount of water released from the ATP-treated soil samples at the end of evaporation was higher than that of the control. After the addition of ATP, the crack area density of dark loessial soil and cultivated loess soil increased significantly, and the crack area density of sandy soil increased with the increase of ATP addition. The crack area density of all three soils reached the maximum at 4% of ATP addition. In summary, ATP addition of 3% could minimize the ineffective evaporation of soil water.

Changes in physicochemical property and microbial community of Pseudostellaria heterophylla soil at diffe-rent fallow ages

GAO Hui-fang, MENG Ting, XIONG Qi, ZHANG Hong-yu, QIU Jun-zhi, LIN Wen-xiong, ZHANG Liao-yuan

2022, 33(8):  2196-2204.  doi:10.13287/j.1001-9332.202208.029

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Pseudostellaria heterophylla is authentic traditional Chinese herbal medicine in Fujian Province. P. hete-rophylla suffers from serious consecutive monoculture problems. Fallow can alleviate such problems, but the mecha-nism is still unclear. In this study, high-throughput sequencing was performed to analyze the changes in soil microbial community structure and diversity in the P. heterophylla soil at different fallow ages as well as their relationships with soil physicochemical properties and phenolic acids. The results showed that fungal community diversity decreased but bacterial community diversity increased in fallow soils compared with the control soil of P. heterophy-lla. For bacterial communities, the relative abundance of Acidobacteria increased, while that of Proteobacteria and Actinobacteria decreased in fallow soils. For fungal communities, the relative abundance of dominant phyla had no significant difference between fallow and control soils. Soil acidity and organic matter content showed a trend of weakening and decreasing, respectively, with the increases of fallow years. In addition, with the increases of fallow years, the content of phenolic acids in soil, including benzoic acid and salicylic acid, showed significant decrease, while some other phenolic acids such as p-coumaric acid were accumulated obviously. Taken together, fallow could efficiently ameliorate the structure of soil microbial community and soil properties of P. heterophylla, and thus alleviate the effects of continuous cropping.

Characteristics and influencing factors of soil nitrification potential in coastal salinized farmland

LI Hong-qiang, YAO Rong-jiang, YANG Jing-song, WANG Xiang-ping, XIE Wen-ping, ZHANG Xin

2022, 33(8):  2205-2212.  doi:10.13287/j.1001-9332.202208.017

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Understanding the nitrification capacity of coastal saline farmland soils and its main drivers is of great significance to regulate soil nitrification and improve the utilization efficiency of nitrogen fertilization in farmland. Using a combination of field investigations and laboratory analyses, we examined farmland soil nitrification potential and soil physical, chemical, and biological properties in the coastal muddy tidal flat saline soil area (Dongying and Dongtai). We established the correlation between soil properties and soil nitrification potential with multiple stepwise regression analyses and structural equation modeling (SEM). The results showed that soil pH value was relatively stable and other soil properties and soil nitrification potential varied in coastal saline farmland. The soil nitrification potential ranged from 0.04 to 10.42 mg·kg^-1·d^-1 and decreased with the increases of soil salinization level. Soil nitrification potential had the strongest correlation with soil organic matter, cation exchange capacity, and Cl^-, with the correlation coefficient being 0.409, 0.397 and -0.337, respectively. The results of multiple stepwise regression analysis showed that Na⁺, silt, cation exchange capacity, and CO₃^2-+HCO₃^- were the main influencing factors of soil nitrification potential. The results from the SEM analysis suggested that Na⁺, silt, cation exchange capacity, and CO₃^2-+HCO₃^- directly affected soil nitrification potential, and soil organic matter, clay, Cl^- and SO₄^2- had indirect effects. In all, soil Na⁺ and cation exchange capacity were the two main factors affecting nitrification. Adjusting soil NaCl content and cation exchange capacity was an effective means of regulating soil nitrification.

Urban thermal environment effects based on visual indices: A case study in Xuzhou City, China

ZHOU Hong-xuan, PU Hong-tong, CUI Lu-lu, ZHOU Feng-lin, SUN Jing

2022, 33(8):  2213-2220.  doi:10.13287/j.1001-9332.202208.024

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Urban thermal environments are closely related to habitats, citizens' health, and sustainable development. Based on green view index (GVI), we proposed two new visual indices, construction view index (CVI) and imperious surface view index (R&PVI). Mobile observation was used to obtain urban thermal environment data, images and coordinates synchronously in Xuzhou City in late summer, including urban area (U), scenic area (S), exterior of university campus (E), and university campus inside (CUMT). We analyzed the impacts of the urban composition represented by the visual index on the urban thermal environment. The results showed that, along the sampling line, mean air temperature (T_a) was highest (30.42 ℃) and mean relative humidity (RH) was lowest (40.7%) in urban area, while mean T_a was lowest (29.35 ℃) and mean RH was highest (48.4%) in scenic area. The situation of mean wind-chill temperature (T_aW) was the highest (32.95 ℃) in the urban area and the lowest (31.93 ℃) in the scenic area. As for CVI, urban area, university campus inside, exterior of university campus and scenic area ranked in descending order, while GVI showed an opposite pattern. CVI was significantly positively correlated to T_a and T_aW, but negatively to RH. GVI was significantly negatively correlated to T_a and T_aW, but positively to RH. R&PVI was significantly positively correlated to T_a and T_aW, but not correlated to RH. CVI and GVI influenced T_a significantly, with the independent effects being 10.4% and 18.9%, and joint effects being 7.8% and 11.3%, respectively. As for RH, CVI and GVI contributed significantly as well, independent effects were 37.5% and 15.7%, and joint effects were 51.4% and 30.2%, respectively. As for T_aW, the three visual indices contributed significantly, but independent and joint effects were lower than those on T_a. Moreover, visual indices contributed more on RH than T_a or T_aW. The results could provide ideas for optimizing urban thermal environments and mitigating urban heat island effects, and have practical implications for urban renewal and improvement of the quality of human living environment.

Spatial characteristics and source apportionment of urban environmental black carbon concentrations based on mobile monitoring

WU Qiu-tong, LIU Min, LI Shu-hui, GAO Chan-chan, CAO Shan-shan, SU Ling, ZHANG Shi-qing

2022, 33(8):  2221-2228.  doi:10.13287/j.1001-9332.202208.023

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Black carbon (BC) is an important component of airborne fine particulate matter, with significant impacts on global climate change and human health. Taking Minhang District of Shanghai as the study area, a microaethalometer (MA200) and GPS were installed on the electric taxi to form a mobile observation platform to identify the spatial distribution and hot spots of atmospheric BC in urban environment. We analyzed the sources and influencing factors of BC. The results showed that the overall characteristics of the spatial distribution pattern of near surface atmospheric BC in Minhang District of Shanghai were high in the north and low in the south. The average BC concentration was (4.11±4.87) μg·m^-3. The average concentrations of BC in working days and non-working days were (4.22±1.49) and (3.52±2.26) μg·m^-3. The variability of BC concentration in the high value area was large, indicating that the increases of BC concentration in mobile observation were related to traffic accidents in the road section. In addition to human activities, large-scale dense vegetation might inhibit BC diffusion. The Absorption ngström Exponent (AAE) was (0.82±0.54), which was closer to that of fossil fuel combustion. The contributions of fossil fuel emissions, biomass combustion, and mixed sources to BC sources were 67.5%, 4.9% and 27.6%, respectively.

Pattern evolution and impact factor of Jiuduansha Wetland at the Yangtze Estuary during 1989-2020

SHI Yu-xiao, LI Yang, MENG Yi, ZHAO Zhi-yuan, ZHANG Ting-yu, WANG Dong, YUAN Lin

2022, 33(8):  2229-2236.  doi:10.13287/j.1001-9332.202208.022

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Affected by the changes of drainage basin and marine environment and human activities, estuarine wetland is fragile, sensitive, and complex in evolution. Jiuduansha Wetland is the largest estuarine shoal wetland in the Yangtze Estuary, and is undergoing rapid changes due to the reduction of sediment inputs and the invasion of alien species Spartina alterniflora. In this study, the changes of Jiuduansha Wetland from 1989 to 2020 were analyzed through remote sensing interpretation, field investigation, and topographic data analysis. The impacts of watershed sediment reduction and S. alterniflora invasion on Jiuduansha Wetland were analyzed based on the hydrological data of Datong station and the invasion history of S. alterniflora. The results showed that the total area of Jiuduansha Wetland (above -5 m) first increased and then decreased since 1991, reaching its maximum in 2005 (421.16 km²). The area of tidal flat wetland (above 0 m) and wetland vegetation increased continuously from 1989 to 2020, with 1.5 times and 47.1 times increases, respectively. The decreases of sediment supply led to a decrease in the total area of Jiuduansha Wetland (above -5 m) and a decrease growth rate of tidal flat wetland area above 0 m and vege-tation area. The invasive species S. alterniflora had expanded rapidly, occupied the space of native species, and became the dominant species in Jiuduansha Wetland since it was introduced in 1997. Sediment reduction and S. alterniflora invasion had led to the rapid changes of Jiuduansha Wetland structure. In order to avoid the degradation of ecological service, wetland protection and restoration should be taken to maintain the stability and health of Jiu-duansha Wetland.

Spatio-temporal variations in species composition and diversity of fish communities in the adjacent waters of Changshan Islands, China

ZOU Jian-yu, XUE Ying, JI Yu-peng, ZHANG Chong-liang, LIU Xiao-hui, REN Yi-ping, XU Bin-duo

2022, 33(8):  2237-2243.  doi:10.13287/j.1001-9332.202209.029

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In order to understand species composition and diversity of fish communities in the ecotone between the Yellow Sea and Bohai Sea, we examined species composition and temporal and spatial variations of fish species diversity using the relative importance index (IRI), species diversity index and k dominance curve based on bottom trawl survey data of fish resources in the adjacent waters of the Changshan Islands in October 2016, January, May and August 2017. The results showed that 77 fish species were captured, mainly temperate water fishes, demersal fishes and migratory fishes. The dominant species exhibited obvious seasonal variation. The dominant species in spring and winter were Lophius litulon, and those in summer were pelagic species such as Scomber japonicus and Engraulis japonicus. A total of 46 migratory fish species were found throughout the year. The seasonal species migration indices were all higher than 100, while the species migration index was the largest in autumn. The species diversity index showed high spatial and temporal dynamics, with the highest species richness in spring and the highest Shannon diversity and evenness in autumn. There was a significant negative correlation between species richness and sea surface temperature in summer, significant positive correlations between species richness and depth and bottom temperature in winter, and a significant positive correlation between Shannon diversity index and sea bottom temperature. In short, fish community showed high species diversity, rich migratory species and obvious temporal and spatial heterogeneity in the adjacent waters of the Changshan Islands, which is an ecotone between the Yellow Sea and the Bohai Sea.

Growth heterogeneity of Larimichthys polyactis in spring and autumn along the coast of Zhejiang, China

WANG Ya-li, ZHU Hai-chen, LI Xiao-dong, XU Kai-da, ZHOU Yong-dong, JIANG Ri-jin, LI Zhen-hua

2022, 33(8):  2244-2250.  doi:10.13287/j.1001-9332.202209.028

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In order to understand the growth dynamics of Larimichthys polyactis in spring and autumn along the coast of Zhejiang Province, we used the survey data of bottom trawlers in spring (April) and autumn (November) from 2014 to 2019 along the coast of Zhejiang Province to examine the heterogeneity of L. polyactis growth by constructing a generalized linear model (GLM) and nine linear mixed effect models (LMEM). The results showed that body length of L. polyactis ranged from 15 mm to 210 mm, with an average of 124.12 mm. The dominant body length group ranged from 110 mm to 140 mm. The body weight ranged from 0.04 g to 156.2 g, with an average of 33.28 g. The dominant body weight group ranged from 30 to 50 g. According to the AIC minimum criterion, the LMEM model with the random effects of seasons and water zones on growth parameters a and b was the best. The results of cross validation also showed that the prediction of this model was the best. In the optimal model, the fixed value of growth parameter a was 0.61×10^-4, which ranged in (0.32-1.91)×10^-4 after adding season and water random effect. The fixed value of parameter b was 2.73, and ranged from 2.49 to 2.86 after adding the random effects of season and water area, indicating that small yellow croaker was under negative allometric growth. Season and water zone had significant effects on the relationship between body length and body weight of small yellow croaker. From a seasonal perspective, the growth rate of small yellow croaker in spring was higher than that in autumn. From water zone perspective, the closer the offshore distance, the faster the growth rate of small yellow croaker.

Baseflow variation and its response to precipitation in Jiuqushui watershed, Southern Jiangxi Province, China

LI Jun, SHENG Fei, LIU Shi-yu, ZHANG Ting, YU Min-qi

2022, 33(8):  2251-2259.  doi:10.13287/j.1001-9332.202208.027

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Baseflow is an important part of water resources. Exploring the characteristics of baseflow and its response to precipitation is of great significance to optimize the partition of water resources. Based on the data of daily precipitation and runoff from 1982 to 2019 in Jiuqushui watershed, we analyzed the characteristics of baseflow change, investigated the time lag effect of baseflow on precipitation, and calculated the contribution rate of precipitation to baseflow change by using digital filtering method, cross wavelet transform method, and slope change ratio of accumulative quantity method. The results showed that during the study period, the variation trend of annual baseflow depth and annual baseflow index was not significant, with annual average values of 384.21 mm and 0.44, respectively. The depth of baseflow in spring and summer was greater than that in autumn and winter, while the baseflow index showed an opposite pattern. Annual precipitation affected the dynamic change of annual baseflow depth, with the effects in spring and summer being stronger than that in autumn and winter. The lag time of baseflow in spring, summer, autumn and winter were 3.5-10.3, 1.5-8.5, 2-10, 2-13 and 5-20.5 days, while the average annual lag time was 6.4, 4.9, 5.3, 6.8 and 10.8 days, respectively. The annual baseflow depth changed abruptly in 1992. The contribution rate of precipitation to baseflow change was 68.2%, and that of other factors was 31.8%. The results could provide scientific basis for evaluating the hydrological effects of forests and ensuring water ecological security of rivers in the red soil region of southern China.

Reviews

Black microplastics in the environment: Origin, transport and risk of tire wear particles

CHEN Yao, LIU Jin, ZHANG Ying-xin, LI Jia-yang, LI Gui-ju

2022, 33(8):  2260-2270.  doi:10.13287/j.1001-9332.202208.028

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With the continuous growth of vehicle per capita in recent years, tire wear particles (TWP) produced by tire wear on roads have been widely found in various environmental media, whose environmental behavior and effects have attracted extensive attention. After being produced, these microsized and nanosized TWP will drift into the atmosphere or enter the surrounding soil, rivers, and even into the ocean with rain and runoff. The existence of TWP significantly affects the composition of organic materials in the environment. Meanwhile, the release of heavy metals and organic additives from TWP will be harmful to organisms and human health. We summarized the sources and characteristics of TWP, their migration and diffusion in water, atmosphere, and soil environment. By analyzing the environmental impacts and ecological risks of TWP pollution, we proposed the key questions urgently to be solved and prevention measures.

Collaborative monitoring network of ecologically fragile areas in China and its application in carrying capacity research

YI Shu-hua, CHEN Shi-ping, LI Ying-nian, HU Zhong-ming

2022, 33(8):  2271-2278.  doi:10.13287/j.1001-9332.202208.026

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Ecologically fragile areas account for more than 60% of land area in China. Global change and human activities are aggravating ecosystem degradation and reducing the carrying capacity of resources and environment. It is important to accurately quantify the carrying capacity of resources and environment in ecologically fragile areas to deal with the risk and challenge of global change and to speed up the construction of ecological civilization. How-ever, existing methods evaluating carrying capacity of resources and environment are difficult to reflect the transmission effect of ecosystem structures, processes and functions changes among resource, environment and carrying capacity. Therefore, it is essential to establish a field observation network and obtain the comprehensive data set of resource and environment elements-ecosystem structure, function and process-ecosystem carrying capacity for develo-ping the theory and evaluation method. We introduced the collaborative monitoring networks of flux and UAV photographing, including the thoughts, practice, and preliminary results in the study of ecosystem structure, process and function in the fragile ecosystems of China. Based on the achievements and progress, we proposed the application of collaborative monitoring networks in capacity evaluation.

Research progress on nurse effects of shrubs in ecological restoration

TANG Jiao, YIN Jin-zhong, PAN Fei-fei, LI Jun-na, ZHAO Yun-fei, WU Da-fu

2022, 33(8):  2279-2285.  doi:10.13287/j.1001-9332.202208.004

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Shrubs are the major components of vegetation in arid and semi-arid areas, and play a pivotal role in maintaining ecosystem stability and function. The nurse effects of shrubs can help with the regeneration of native target plant species by alleviating the adverse influences that limit their growth and reproduction in degraded habitats. We summarized the main research results and application of shrub nurse effects in the last 20 years. We discussed several facilitation mechanisms of nurse shrubs, including microhabitat amelioration, fertile island formation, defense and resistance against herbivores, introduction of beneficial microorganism and propagule propagation or preservation, as well as changes in the patterns of interspecific competitive networks. Key factors affecting nurse effects were analyzed, including abiotic environments, biological disturbances, plant life history as well as growth and reproductive strategies. Prospects for future research were also considered from the aspects of improving theore-tical mechanisms of nurse effects by shrubs and building models involved in multiple plant species interaction affec-ted by multifactors.

Biological characteristics of heat shock transcription factors and their roles in abiotic stress adaptation of higher plant

SHAO Kun-zhong, LYU Xin-pei, LI Jia-lyu, CHEN Jia, ZHAO Ling-yu, REN Wei, ZHANG Jin-lin

2022, 33(8):  2286-2296.  doi:10.13287/i.1001-9332.202208.039

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Heat shock transcription factors (HSFs) are involved in the regulation of plant growth and development. Furthermore, HSFs regulate the expression of a series of genes related to various abiotic stress adaptations. HSFs usually form homotrimers to activate their transcriptional activity and function. Here, we review the basic structure, subcellular localization, transcriptional regulation, functional diversity of HSFs, and their roles in plant adaptation to abiotic stresses, such as extreme temperature, salinity, drought, strong light and oxidative stress, etc. HSFs are high-quality candidate genes for improving the resistance of higher plants to multiple stresses. Studies of HSFs have important application value. In the future, using HSFs to improve the resistance of various crops through genetic engineering would be prospects of development.

Research advances in the impacts of oil pollutants on birds and the cleaning and repairing techniques

XIE Yu-cheng, ZHU Zi-qiang, XU Ji-liang, LEI Wei-pan, CHEN De, LI Dong-lai, LI Jian-qiang, ZHANG Zheng-wang

2022, 33(8):  2297-2304.  doi:10.13287/j.1001-9332.202208.030

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Oil and its pollutants, which enter environment through natural oil seepage and many human activities, have considerable impacts on birds. We summarized the research advances in how oil pollutants influence birds and the cleaning technology of polluted birds and their habitats. The toxicity and destruction to feather structure are the major impacts of oil pollution on birds. Oil pollution can lead to birds' death, and also produce many chronic harms, including causing hemolytic anemia, reducing their immunity, disrupting thermal insulation and waterproo-fing performance of feather. It is an important way to reduce the impacts of oil pollution on birds by timely cleaning up the oil in bird habitats as well as carrying out the clean and repair work to the polluted birds. As a big oil-consuming country, China has been left behind by foreign countries in the studies of the effects of oil pollution on birds. More attention should be paid on the short-term and long-term impacts of oil pollution on birds and the cleaning and remediation technologies of the polluted birds and their habitats.