Table of Content

15 May 2023, Volume 34 Issue 5

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C, N, and P stoichiometry for leaf litter of 62 woody species in a subtropical evergreen broadleaved forest

LI Aogui, CAI Shifeng, LUO Suzhen, WANG Xiaohong, CAO Lirong, WANG Xue, LIN Chengfang, CHEN Guangshui

2023, 34(5):  1153-1160.  doi:10.13287/j.1001-9332.202305.005

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To understand leaf litter stoichiometry in a subtropical evergreen broadleaved forest, we measured the contents of carbon (C), nitrogen (N) and phosphorus (P) in leaf litters of 62 main woody species in a natural forest of C. kawakamii Nature Reserve in Sanming, Fujian Province. Differences in leaf litter stoichiometry were analyzed across leaf forms (evergreen, deciduous), life forms (tree, semi-tree or shrub), and main families. Additionally, the phylogenetic signal was measured by Blomberg's K to explore the correlation between family level differentiation time and litter stoichiometry. Our results showed that the contents of C, N and P in the litter of 62 woody species were 405.97-512.16, 4.45-27.11, and 0.21-2.53 g·kg^-1, respectively. C/N, C/P and N/P were 18.6-106.2, 195.9-2146.8, and 3.5-68.9, respectively. Leaf litter P content of evergreen tree species was significantly lower than that of deciduous tree species, and C/P and N/P of evergreen tree species were significantly higher than those of deciduous tree species. There was no significant difference in C, N content and C/N between the two leaf forms. There was no significant difference in litter stoichiometry among trees, semi-trees and shrubs. Effects of phylogeny on C, N content and C/N in leaf litter was significant, but not on P content, C/P and N/P. Family differentiation time was negatively correlated with leaf litter N content, and positively correlated with C/N. Leaf litter of Fagaceae had high C and N contents, C/P and N/P, and low P content and C/N, with an opposite trend for Sapidaceae. Our findings indicated that litter in subtropical forest had high C, N content and N/P, but low P content, C/N, and C/P, compared with the global scale average value. Litter of tree species in older sequence of evolutionary development had lower N content but higher C/N. There was no difference of leaf litter stoichiometry among life forms. There were significant differences in P content, C/P, and N/P between different leaf forms, with a characteristic of convergence.

Altitudinal variations and seasonal dynamics of near-surface and soil temperatures in subtropical forests of Mt. Guanshan, Jiangxi Province, China

WANG Fang, LU Yaoshun, ZHANG Zhaochen, CHEN Lin, YANG Yongchuan, ZHANG Hongwei, WANG Xiaoran, SHU Li, SHANG Xiaofan, LIU Pengcheng, YANG Qingpei, ZHANG Jian

2023, 34(5):  1161-1168.  doi:10.13287/j.1001-9332.202305.019

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Temperature lapse rate (TLR), measured as the degree of temperature change along an altitudinal gradient, is a key indicator of multiple ecological processes of mountain systems. Although many studies have examined temperature changes of open air or near-surface along altitudes, we know little about altitudinal variations of soil temperature, which play an important role in regulating growth and reproduction of organisms, as well as ecosystem nutrient cycling. Based on temperature data of near-surface (15 cm above ground) and soil layers (8 cm below ground) from 12 sampling sites of subtropical forest along an altitudinal gradient (300-1300 m) in Jiangxi Guan-shan National Nature Reserve from September 2018 to August 2021, we calculated the lapse rates of mean, maximum, and minimum temperatures, as well as accumulated temperatures by using simple linear regression for both near-surface and soil temperature. The seasonal dynamics of aforementioned variables were also evaluated. The results showed that there were large differences among mean, maximum, and minimum lapse rates for annual near-surface temperature, which were 0.38, 0.31 and 0.51 ℃·(100 m)^-1, respectively. But little variation was documented for soil temperature which were 0.40, 0.38 and 0.42 ℃·(100 m)^-1, respectively. The seasonal variations of temperature lapse rates for near-surface and soil layers were minor except for minimum temperature. The lapse rates of minimum temperature were deeper in spring and winter for near-surface and in spring and autumn for soil layers. For growing degree days (GDD), the accumulated temperature under both layers were negatively correlated with altitude, and the lapse rates of ≥5 ℃ were 163 ℃·d·(100 m)^-1 for near-surface and 179 ℃·d·(100 m)^-1 for soil. The ≥5 ℃ GDD in soil were about 15 days longer than that in near-surface at the same altitude. The results showed inconsistent patterns of altitudinal variations between near-surface and soil temperature. Soil temperature and its lapse rates had minor seasonal variations compared with the near-surface counterparts, which was related to the strong buffering capacity of soil.

Effect of thinning intensity on natural regeneration of Larix principis-rupprechtii

Feng Yonghan, YAN Jue, GUO Yu, ZHAO Yi, DONG Yuan, LIANG Wenjun, WEI Xi, BI Huaxing

2023, 34(5):  1169-1177.  doi:10.13287/j.1001-9332.202305.006

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We analyzed the impacts of thinning intensity on the natural regeneration of Larix principis-rupprechtii in Shanxi Pangquangou Nature Reserve, with an experiment of five thinning intensities (5%, 25%, 45%, 65% and 85%). We constructed a structural equation model of thinning intensity-understory habitat-natural regeneration by using correlation analysis. The results showed that the regeneration index of moderate thinning (45%) and intensive thinning (85%) stand land was significantly higher than that of other thinning intensities. The constructed structural equation model had good adaptability. The effects of thinning intensity on each factor were as follows: soil alkali-hydrolyzable (-0.564) > regeneration index (0.548) > soil bulk density (-0.462) > average height of seed tree (-0.348) > herb coverage (-0.343) > soil organic matter (0.173) > undecomposed litter layer thickness (-0.146) > total soil nitrogen (0.110). Thinning intensity had a positive impact on the regeneration index, which was mainly through adjusting height of the seed tree, accelerating litter decomposition, improving soil physical and chemical properties, and thus indirectly promoting the natural regeneration of L. principis-rupprechtii. Tending thinning could effectively improve the survival environment of regeneration seedlings. From the perspective of natural regeneration of L. principis-rupprechtii, moderate thinning (45%) and intensive thinning (85%) were more reasonable in the follow-up forest management.

Radial growth responses of three coniferous species to climate change on the southern slope of Funiu Mountains, China

LI Zhenjiang, YU Chenyi, LIU Shengyun, YAN Ruihuan, HUANG Xindeng, LIU Xiaojing, CHEN Zhicheng, WANG Ting

2023, 34(5):  1178-1186.  doi:10.13287/j.1001-9332.202305.004

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Funiu Mountains are located in a transition region between warm temperate zone and northern subtropical region, where a variety of plant species are distributed with sensitive response to climate change. Their response characteristics to climate change are still unclear. We developed the basal area increment (BAI) index chronologies of Pinus tabuliformis, P. armandii, and P. massoniana in the Funiu Mountains to examine their growth trend and their sensitivity to climatic change. The results showed that the BAI chronologies gave a clue that the three conife-rous species had similar radial growth rate. The large Gleichlufigkeit (GLK) indices among the three BAI chronologies also indicated that the three species had a similar growth trend. Results of correlation analysis showed that the three species also had similar response to climatic change to a certain extent. Radial growth of all the three species was significantly positively correlated with the total monthly precipitation in December of previous year and June of the current year, but negatively correlated with the precipitation in September and the mean monthly temperature in June of the current year. There were some differences in the responses of the three coniferous to climate change. P. massoniana had a significant negative correlation with the mean temperature in March, and a significant positive correlation with the precipitation in March, while P. armandii and P. massoniana were affected negatively by the maximum temperature in August. Results of the moving correlation analysis showed that the three coniferous species had some similar sensitivity to climate change. Their positive responses to precipitation in previous December consistently increased, as well as the negative correlation with precipitation in current September. As to P. masso-niana, they had a relatively stronger climatic sensitivity and higher stability than the other two species. It would be more suitable for P. massoniana trees on the southern slope of the Funiu Mountains under global warming.

Responses of nitrogen and phosphorus resorption of understory plants to microscale soil nutrient hetero-geneity in Chinese fir plantation

ZHI Kexiang, GUAN Xin, LI Renshan, WANG Jiao, DUAN Xuan, CHEN Bohan, ZHANG Weidong, YANG Qingpeng

2023, 34(5):  1187-1193.  doi:10.13287/j.1001-9332.202305.003

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We compared the interspecific differences in leaf nutrient resorption of two dominant understory species (Lophatherum gracile and Oplimenus unulatifolius), and analyzed the correlations between the intraspecific efficiency of leaf nutrient resorption and nutrient properties of soil and leaves in Chinese fir plantation. The results showed high soil nutrient heterogeneity in Chinese fir plantation. Soil inorganic nitrogen content and available phosphorus content varied from 8.58 to 65.29 mg·kg^-1 and from 2.43 to 15.20 mg·kg^-1 in the Chinese fir plantation, respectively. The soil inorganic nitrogen content in O. undulatifolius community was 1.4 times higher than that in L. gra-cile community, but there was no significant difference in soil available phosphorus content between the two communities. Both leaf nitrogen and phosphorus resorption efficiency of O. unulatifolius was significantly lower than that of L. gracile under the three measurement bases of leaf dry weight, leaf area, and lignin content. Resorption efficiency in L. gracile community expressed on leaf dry weight was lower than that expressed on leaf area and lignin content, while resorption efficiency expressed on leaf area was the lowest in O. unulatifolius community. The intraspecific resorption efficiency was significantly correlated with leaf nutrient contents, but was less correlated with soil nutrient content, and only the nitrogen resorption efficiency of L. gracile had significant positive correlation with soil inorganic nitrogen content. The results indicated that there was significant difference in the leaf nutrient resorption efficiency between the two understory species. Soil nutrient heterogeneity exerted a weak effect on the intraspecific nutrient resorption, which might be attributed to high soil nutrient availability and potential disturbance from canopy litter in Chinese fir plantation.

Effects of liming on soil respiration and its sensitivity to temperature in Cunninghamia lanceolata plantations

TIAN Ning, HUANG Xuemei, CHEN Longchi, HUANG Ke, TAO Xiao

2023, 34(5):  1194-1202.  doi:10.13287/j.1001-9332.202305.011

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The primary distribution area of acid deposition coincides with areas of Chinese fir (Cunninghamia lanceolata) plantations. Liming is an effective method of restoring acidified soil. To understand the effects of liming on soil respiration and temperature sensitivity within the context of acid deposition, we measured soil respiration and its components in Chinese fir plantations for one year beginning in June 2020, with 0, 1 and 5 t·hm^-2 calcium oxide being added in 2018. The results showed that liming considerably increased soil pH and exchangeable Ca²⁺ concentration, and that there was no significant difference among different levels of lime application. Soil respiration rate and components in the Chinese fir plantations exhibited seasonal variations, with the highest values during the summer and the lowest values during the winter. Although liming did not alter seasonal dynamics, it strongly inhibited heterotrophic respiration rate and increased autotrophic respiration rate of soil, with minor effect on total soil respiration. The monthly dynamics of soil respiration and temperature were largely consistent. There was a clear exponential relationship between soil respiration and soil temperature. Liming increased temperature sensitivity Q₁₀ of soil respiration and autotrophic respiration but reduced that of soil heterotrophic respiration. In conclusion, liming promoted soil autotrophic respiration and strongly inhibited soil heterotrophic respiration in Chinese fir plantations, which would facilitate soil carbon sequestration.

Variation in leaf vein traits of Pinaceae plants on the eastern Qinghai-Tibet Plateau, China

ZHU Rong, YANG Xue, GONG Haoxin, WANG Zhibo, CHEN Shuang, WANG Xiaochun, WANG Ruili

2023, 34(5):  1203-1210.  doi:10.13287/j.1001-9332.202305.018

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To explore the adaptative strategies of single-veined plants along the environmental gradient, we collec-ted leaves of 57 Pinaceae species (including Abies, Larix, Pinus and Picea) from 48 sites along a latitudinal gradient (26°58′-35°33′ N) on the eastern Qinghai-Tibet Plateau. By measuring three traits of leaf vein, including vein length per leaf area, vein diameter, and vein volume per unit leaf volume, we analyzed the trade-off between vein traits and their relationship with environmental changes. The results showed no significant difference in vein length per leaf area among different genera, but significant difference in vein diameter and vein volume per unit leaf volume. There was a positive correlation between vein diameter and vein volume per unit leaf volume for all genera. There was no significant correlation of vein length per leaf area with vein diameter and vein volume per unit leaf volume. With the increases of latitude, vein diameter and vein volume per unit leaf volume significantly decreased. In contrast, vein length per leaf area did not show a latitudinal trend. Mean annual temperature was the main factor driving the variation in vein diameter and vein volume per unit leaf volume. The relationships between vein length per leaf area and environmental factors were relatively weak. These results indicated that the single-veined Pinaceae plants have a special adaptative strategy to environmental changes through adjusting vein diameter and vein volume per unit leaf volume, which is quite different from complex vein structures such as reticular veins.

Responses of soil enzyme activity to freeze-thaw alternation in Greater Khingan Mountains, China

WANG Shijia, GUO Yafen, CUI Xiaoyang

2023, 34(5):  1211-1217.  doi:10.13287/j.1001-9332.202305.002

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We examined the effects of freeze-thaw cycles (0, 1, 3, 5, 7, 15 cycles) on the activities of urease, invertase, and proteinase in the different layers of the soil under the four typical stands in the cold temperate zone, i.e., Pinus pumila stand, Rhododendron-Betula platyphylla stand, Rhododendron-Larix gmelinii stand, Ledum-Larix gmelinii stand, with the indoor freeze-thaw simulation culture method being used. The relationship between soil enzyme activity and multiple physicochemical variables was analyzed during freeze-thaw alternation. The results showed that the activity of soil urease was firstly increased and then inhibited during freeze-thaw alternation. After freeze-thaw, urease activity did not differ from that without freeze-thaw. Invertase activity was firstly inhibited and then increased during freeze-thaw alternation, and was significantly increased by 8.5%-40.3% after freeze-thaw. Proteinase activity was firstly increased and then inhibited during freeze-thaw alternation, and was significantly decreased by 13.8%-68.9% after freeze-thaw. After freezing and thawing, there was significant positive correlation between urease activity and ammonium nitrogen and soil water content in Ledum-L. gmelinii stand and P. pumila stand, respectively, and proteinase activity had significant negative correlation with inorganic nitrogen concentration in P. pumila stand, Rhododendron-B. platyphylla stand, and Ledum-L. gmelinii stand. Invertase activity had significant positive correlation with organic matter in Rhododendron-L. gmelinii stand and Ledum-L. gmelinii stand.

Effects of ant nesting on seasonal dynamics of soil N₂O emission in a secondary tropical forest

ZHANG Kunfeng, WANG Shaojun, WANG Ping, ZHANG Lulu, FAN Yuxiang, XIE Lingling, XIAO Bo, WANG Zhengjun, GUO Zhipeng

2023, 34(5):  1218-1224.  doi:10.13287/j.1001-9332.202305.009

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We assessed the seasonal dynamics of N₂O emission in ant nests soils in secondary tropical Millettia leptobotrya forest of Xishuangbanna by using the static chamber-gas chromatography method, and determined the lin-kages between ant-mediated changes in soil properties (e.g., carbon pool, nitrogen pool, and temperature and humidity) and N₂O emission. The results showed that ant nesting significantly affected soil N₂O emission. The ave-rage soil N₂O emission (0.67 mg·m^-2·h^-1) in ant nests was 40.2% higher than that in the control (0.48 mg·m^-2·h^-1). N₂O emission in ant nests and the control showed substantial seasonal variation, with higher rate in June (0.90 and 0.83 mg·m^-2·h^-1, respectively) than that in March (0.38 and 0.19 mg·m^-2·h^-1, respectively). Ant nesting significantly increased the values (7.1%-74.1%) of moisture, temperature, organic carbon, total nitrogen, hydrolytic nitrogen, ammonium nitrogen, nitrate nitrogen, and microbial biomass carbon, but decreased pH (9.9%) compared with the control. Results of structural equation model showed that soil N₂O emission was promoted by soil C and N pool, temperature, and humidity, but was inhibited by soil pH. The explained extents of soil nitrogen pool, carbon pool, temperature and humidity, and pH for N₂O emission changes were 37.2%, 27.7%, 22.9% and 9.4%, respectively. Therefore, ant nesting regulated N₂O emission dynamics by changing nitrification and denitrification substrates (e.g., nitrate and ammoniacal nitrogen), carbon pool, and micro-habitat (temperature and moisture) of soil in the secondary tropical forest.

Diversity and community assembly mechanism of soil ectomycorrhizal fungi in urban parks of Baotou City, China

WANG Yonglong, ZHANG Xuan, XU Ying, ZHAO Yanling, WANG Jiaqi, ZHANG Yujia, YANG Yanci

2023, 34(5):  1225-1234.  doi:10.13287/j.1001-9332.202305.007

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Ectomycorrhizal (EM) fungi play an important role in forest ecosystems. However, little is known about the mechanisms driving diversity and community composition of soil EM fungi in urban forest parks which are intensively affected by anthropogenic activities. In this study, we investigated the EM fungal community using Illumina high-throughput sequencing with soil samples collected from three typical forest parks, including Olympic Park, Laodong Park, and Aerding Botanical Garden of Baotou City. The results showed that soil EM fungi richness index followed a pattern of Laodong Park (146.43±25.17) > Aerding Botanical Garden (102.71±15.31) > Olympic Park (68.86±6.83). Russula, Geopora, Inocybe, Tomentella, Hebeloma, Sebacina, Amanita, Rhizopogon, Amphinema, and Lactarius were the dominant genera in the three parks. EM fungal community composition was significantly different among the three parks. Results of linear discriminant analysis effect size (LEfSe) indicated that all parks had biomarker EM fungi that exhibiting significantly different abundance. The normalized stochasticity ratio (NST) and the inferring community assembly mechanisms by phylogenetic-bin-based null model analysis (iCAMP) showed that both stochastic and deterministic processes determined soil EM fungal communities in the three urban parks, with a dominant role of the stochastic process. Drift and dispersal limitation in the stochastic process and homogeneous selection in the deterministic process were the dominant ecological processes of soil EM fungal community assembly in the three urban parks.

Effects of arbuscular mycorrhizae and extraradical mycelium of subtropical tree species on soil nitrogen mineralization and enzyme activities

CHEN Yuepeng, LI Shikai, AN Bo, ZHU Yong, ZOU Hanlu, CUI Songxiang, FU Hongyan, MAO Rong, ZHANG Yun

2023, 34(5):  1235-1243.  doi:10.13287/j.1001-9332.202305.016

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Through symbiosis with plants, arbuscular mycorrhizal (AM) fungi effectively improve the availability of soil nitrogen (N). However, the mechanism through which AM and associated extraradical mycelium affect soil N mineralization remains unknow. We carried out an in situ soil culture experiment by using in-growth cores in plantations of three subtropical tree species, Cunninghamia lanceolata, Schima superba, and Liquidambar formosana. We measured soil physical and chemical properties, net N mineralization rate, and the activities of four kinds of hydrolase (leucine aminopeptidase (LAP), β-1,4-N-acetylglucosaminidase (NAG), β-1,4-glucosidase (βG), cellobiohydrolase (CB)) and two kinds of oxidases (polyphenol oxidase (POX) and peroxidase (PER)) involved in soil organic matter (SOM) mineralization in treatments of mycorrhiza (with absorbing roots and hyphae), hyphae (hyphae only), and control (mycorrhiza-free). The results showed that mycorrhizal treatments significantly affected soil total carbon and pH but did not affect N mineralization rates and all enzymatic activities. Tree species significantly affected net ammonification rate, net N mineralization rate and activities of NAG, βG, CB, POX and PER. The net N mineralization rate and enzyme activities in the C. lanceolata stand were significantly higher than that in monoculture broad-leaved stands of either S. superba or L. formosana. There was no interactive effect of mycorrhizal treatment and tree species on any of soil properties, nor on enzymatic activities or net N mineralization rates. Soil pH was negatively and significantly correlated with five kinds of enzymatic activities except for LAP, while net N mineralization rate significantly correlated with ammonium nitrogen content, available phosphorus content, and the activity level of βG, CB, POX, and PER. In conclusion, there was no difference in enzymatic activities and N mineralization rates between rhizosphere and hyphosphere soils of three subtropical tree species in the whole growing season. The activity of particular carbon cycle-related enzymes was closely related to soil N mineralization rate. It is suggested that differences in litter quality and root functional traits among different tree species affect soil enzyme activities and N mineralization rates through organic matter inputs and shaping soil condition.

Xylem formation of Populus euphratica and its response to water-heat factors in the lower reaches of Tarim River, China

HE Qingzhi, YE Mao, PAN Xiaoting, ZHAO Fanfan, ZHANG Kaili

2023, 34(5):  1244-1252.  doi:10.13287/j.1001-9332.202305.001

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To deeply understand the effects of water and temperature factors on the xylem formation of Populus euphratica, taking the Yingsu section in the lower reaches of Tarim River as an example, we selected micro-coring samples of P. euphratica around monitoring wells F₂ and F₁₀ in the 100 and 1500 m distance from the channel of Tarim River. We used wood anatomy method to analyze the xylem anatomy of P. euphratica and its response to water and temperature factors. The results showed that the changes of the total anatomical vessel area and the vessel number of P. euphratica in the two plots were basically consistent during the whole growing season. The vessel number of xylem conduits of P. euphratica increased slowly with the increases of groundwater depth, while the total conduit area increased firstly and then decreased. The total vessel area, minimum vessel area, average vessel area, and maximum vessel area of P. euphratica xylem increased significantly with the increases of temperature in the growing season. The contribution of groundwater depth and air temperature to P. euphratica xylem varied among different growth stages. In the early growing season, air temperature had the largest contribution to the number and total area of xylem conduits of P. euphratica. During the middle growing season, air temperature and groundwater depth jointly affected the parameters of each conduit. During the later growing season, groundwater depth had the largest contribution to the number and total area of conduits. Results of the sensitivity analysis indicated that the groundwater depth sensitive to xylem vessel number change of P. euphratica was 5.2 m and that to the change in the total conduit area was 5.9 m. The temperature sensitive to total vessel area of P. euphratica xylem was 22.0 ℃, and that to average vessel area was 18.5 ℃. Therefore, the sensitive groundwater depth affecting xylem growth was at the range of 5.2-5.9 m, and the sensitive temperature was at the range of 18.5-22 ℃. This study could provide scientific basis for the restoration and protection of P. euphratica forest in the lower reaches of Tarim River.

Effects of coal gangue on soil property and plant growth in mining area

NAN Yicong, YANG Yonggang, WANG Zeqing, ZHOU Yang, SU Qiaomei

2023, 34(5):  1253-1262.  doi:10.13287/j.1001-9332.202305.028

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With indoor and outdoor treatments, coal gangue with different ratios (10%, 20%, 30%, 40% and 50%) and different particle sizes (0-2, 2-5, 5-8 and 8-10 mm) were mixed into soil, and formed reconstructed soil with different soil bulk densities (1.3, 1.35, 1.4, 1.45 and 1.5 g·cm^-3). The effects of soil reconstruction modes on soil water condition, structure stability of aggregate and the growth of Lolium perenne, Medicago sativa, and Trifolium repens were investigated. Soil saturated water (SW), capillary water (CW), and field water capacity (FC) were decreased with increasing coal gangue ratio, particle size, and bulk density of reconstructed soil. >0.25 mm particle size aggregate (R_0.25), mean weight diameter (MWD), and geometric mean diameter (GMD) increased first and then decreased with the increases of coal gangue particle size, reaching the peak at 2-5 mm coal gangue particle size. R_0.25, MWD and GMD were significantly and negatively correlated with coal gangue ratio. Based on boosted regression tree (BRT) model, the coal gangue ratio contributed 59.3%, 67.0% and 40.3% to the variation of SW, CW and FC, respectively, which was a main influencing factor of soil water content. The coal gangue particle size contributed 44.7%, 32.3% and 62.1% to the variation of R_0.25, MWD, and GMD, respecti-vely, which was the greatest influencing factor. Coal gangue ratio had a great effect on the growth of L. perenne, M. sativa, and T. repens, which contributed to 49.9%, 17.4% and 10.3% of their variations, respectively. Soil reconstruction mode of 30% coal gangue ratio and 5-8 mm coal gangue particle size was the best condition for plant growth, indicating that coal gangue could change soil water content and structure stability of aggregate. The soil reconstruction mode of 30% coal gangue ratio and 5-8 mm coal gangue particle size was recommended.

Effects of 5-HT on the cold resistance of mangrove Kandelia obovata seedlings

ZHANG Huiyu, YUE Danfei, PAN Xiaojiao, HAO Lulu, LIU Weicheng, ZHENG Chunfang

2023, 34(5):  1263-1271.  doi:10.13287/j.1001-9332.202305.013

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5-hydroxytryptamine (5-HT) participates in plant growth and development, and can also delay senescence and cope with abiotic stress. To explore the role of 5-HT in regulating the abilities of mangrove in cold resis-tance, we examined the effects of cold acclimation and the spraying of p-chlorophenylalanine (p-CPA, 5-HT synthesis inhibitor) on leaf gas exchange parameters and CO₂ response curves (A/Ca), as well as the endogenous phytohormone content levels in the mangrove species Kandelia obovata seedlings under low temperature stress. The results showed that low temperature stress significantly reduced the contents of 5-HT, chlorophyll, endogenous auxin (IAA), gibberellin (GA), and abscisic acid (ABA). It weakened the CO₂ utilization abilities of plants and reduced net photosynthetic rate, which ultimately reduced carboxylation efficiency (CE). Under low temperature stress, exogenous p-CPA reduced the contents of photosynthetic pigments, endogenous hormones, and 5-HT in the leaves, which aggravated the damages caused by low temperature stress on photosynthesis. By enhancing cold acclimation abilities, the endogenous IAA content in the leaves could was reduced under low temperature stress, promoted the production of 5-HT, improved the contents of photosynthetic pigments, GA, and ABA, as well as enhanced photosynthetic carbon assimilation abilities, which would increase photosynthesis in the K. obovata seedlings. Under cold acclimation conditions, the spraying of p-CPA could significantly inhibit the synthesis of 5-HT, promote the production of IAA, and reduce the contents of photosynthetic pigments, GA, ABA, and CE, which would weaken the effects of cold acclimation by improving the cold resistance of mangroves. In conclusion, cold acclimation could improve the cold resistance abilities of K. obovata seedlings by regulating photosynthetic carbon assimilation capacity and the contents of endogenous phytohormone. 5-HT synthesis is one of the necessary conditions for improving the cold resistance abilities of mangroves.

Habitat suitability evaluation of invasive plant species Datura stramonium in Liaoning Province: Based on Biomod2 combination model

WANG Ziwen, YIN Jin, WANG Xing, CHEN Yue, MAO Zikun, LIN Fei, GONG Zongqiang, WANG Xugao

2023, 34(5):  1272-1280.  doi:10.13287/j.1001-9332.202305.017

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Datura stramonium, as a major invasive plant in Liaoning Province, is difficult to be removed after its successful invasion, and is a great threat to ecological environment and biodiversity. To evaluate the habitat suitabi-lity of D. stramonium, we collected its geographic distribution data in Liaoning Province through field investigation and database query, and using the Biomod2 combination model, and investigated its potential and suitable distribution areas and main influencing environmental variables at present and under future climate change scenarios, respectively. The results showed that the combined model which composed of GLM (generalized linear model), GBM (generalized boosting regression model), RF (random forest model), and MaxEnt (maximum entropy model) had a good performance. By classifying the habitat suitability of D. stramonium into four categories: high-, medium-, low- and un-suitable habitats, we found that the high-suitable habitats were generally distributed in the northwest and south of Liaoning Province, with an area of about 3.81×10⁴ km², accounting for 25.8% of the total area. The medium-suitable habitats were mostly distributed in the northwest and central parts of Liaoning Province, with an area of about 4.19×10⁴ km², accounting for 28.3% of the total area. Slope and clay content of topsoil (0-30 cm) were the two main variables explaining the habitat suitability of D. stramonium, and the total suitability of D. stramonium first increased and then decreased with the increasing slope and clay content of topsoil in this region. Under future climate change scenarios, the total suitability of D. stramonium showed an expanding trend, and its suitability would be obviously increased in Jinzhou, Panjin, Huludao, and Dandong.

Effects of elevated CO₂ concentration on cell structure and stress resistance physiology of Setaria italica under drought stress

LI Junliang, WANG Shibo, LI Yajun, HAO Xingyu, ZONG Yuzheng, ZHANG Dongsheng, SHEN Jie, SHI Xinrui, LI Ping

2023, 34(5):  1281-1289.  doi:10.13287/j.1001-9332.202305.015

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The frequency of drought will increase under further warming. The increase in atmospheric CO₂ concentration, along with more frequent drought, will affect crop growth. We examined the changes of cell structure, photosynthetic physiology, antioxidant enzymes, osmotic regulatory substances, and yield of foxtail millet (Setaria ita-lica) leaves under different CO₂ concentrations (ambient air CO₂ concentration and ambient atmospheric CO₂ concentration + 200 μmol·mol^-1) and water treatment (soil moisture content maintained at 45%-55%, and 70%-80% of field capacity, representing mild drought and normal water condition, respectively). The results showed that elevated CO₂ concentration increased the number of starch grains, the area of single starch grains, and the total area of starch grains in the chloroplast of millet mesophyll cells. Under mild drought condition, elevated CO₂ concentration increased net photosynthetic rate of millet leaves at the booting stage by 37.9%, but did not affect water use efficiency at this stage. Elevated CO₂ concentration increased net photosynthetic rate and water use efficiency of millet leaves under mild drought condition at the filling stage by 15.0% and 44.2%, respectively. Under mild drought condition, elevated CO₂ concentration increased the content of peroxidase (POD) and soluble sugar in millet leaves at the booting stage by 39.3% and 8.0%, respectively, but decreased proline content by 31.5%. It increased the content of POD in millet leaves at the filling stage by 26.5% but decreased the content of MDA and proline by 37.2% and 39.3%, respectively. Under mild drought condition, elevated CO₂ concentration significantly increased the number of grain spikes by 44.7% and yield by 52.3% in both years compared with normal water condition. The effect of elevated CO₂ concentration on grain yield under mild drought conditions was higher than that under normal water condition. Under mild drought conditions, elevated CO₂ concentration increased leaf thickness, vascular bundle sheath cross-sectional area, net photosynthetic rate, and water use efficiency of millet, improved the antioxidant oxidase activity, and changed the concentration of osmotic regulatory substances, alleviated the nega-tive effect of drought on foxtail millet, and finally increased the number of grains per ear and yield of foxtail millet. This study would provide a theoretical basis for millet production and sustainable agricultural development in arid areas under future climate change.

Effects of rotted corn straw on soil environment, yield, and quality of cucumber

ZHANG Xiaowei, YANG Xianhe, CHE Haojie, QIN Jing, BI Huangai, AI Xizhen

2023, 34(5):  1290-1296.  doi:10.13287/j.1001-9332.202305.010

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Aiming at solving the problems of soil environment deterioration and the decline of both yield and quality caused by excessive application of chemical fertilizer, we investigated the effects of rotted corn straw on the soil environment of root zone, yield and quality of cucumber with ‘Jinyou 35' cucumber as the experimental material. There were three treatments, namely, combined application of rotted corn straw and chemical fertilizer (T₁, the total nitrogen fertilizer application were 450 kg N·hm^-2, of which 9000 kg·hm^-2 rotted corn straw was used as the subsoil fertilizer, and the rest was supplemented with chemical fertilizer), pure chemical fertilizer (T₂, the total nitrogen fertilizer application was the same as T₁) and no fertilization (control). The results showed that the content of soil organic matter in root zone soil in T₁ treatment was much higher, but no difference between T₂ treatment and the control, after two continuous plantings in one year. The concentrations of soil alkaline nitrogen, available phosphorus, available potassium of T₁ and T₂ in cucumber root zone were higher than that in the control. T₁ treatment had lower bulk density, but markedly higher porosity and respiratory rate than T₂ treatment and the control in root zone soil. The electric conductivity of T₁ treatment was higher than that of the control, but significantly lower than T₂ treatment. There was no significant difference in pH among the three treatments. The quantity of bacteria and actinomycetes in cucumber rhizosphere soil were the highest in T₁, and the lowest in the control. However, the highest quantity of fungi was found in T₂. The enzyme activities of rhizosphere soil in T₁ treatment were markedly higher than those of the control, whereas those of T₂ treatment were significantly lower or had no significant difference relative to the control. The cucumber root dry weight and root activity of T₁ were significantly higher than that of the control. The yield of T₁ treatment increased by 10.1%, and fruit quality improved obviously. The root activity of T₂ treatment was also significantly higher than that in the control. There was no significant difference in root dry weight and yield between T₂ treatment and the control. Furthermore, T₂ treatment revealed a decrease in fruit quality relative to T₁ treatment. These results suggested that the combined application of rotted corn straw and chemical fertilizer could improve soil environment, promote root growth, enhance root activity and improve yield and quality of cucumber in solar-greenhouse, which could be popularized and applied in protected cucumber production.

Effects of drip irrigation frequency on the yield and nutrient utilization efficiency of tomato under long-season cultivation in solar greenhouse

MENG Qingqing, WU Fengling, SONG Jianli, WEI Min, MENG Lun, LI Jing, YANG Fengjuan

2023, 34(5):  1297-1304.  doi:10.13287/j.1001-9332.202305.014

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To improve the utilization efficiency of nutrients and water and determine the best drip irrigation frequency for long-season tomato cultivation in solar greenhouses, we cultivated tomato grafted seedlings in soil using an integrated water and fertilizer technology: drip irrigation under mulch. Seedlings drip-irrigated with balanced fertilizer (containing 20% N, 20% P₂O₅, and 20% K₂O) and high-K fertilizer (containing 17% N, 8% P₂O₅, and 30% K₂O) once every 12 days were set as control (CK) and that with water once every 12 days as CK₁, while other seedling groups, drip-irrigated with a nutrient solution of Yamazaki (1978) formula for tomato, were set as treatments (T₁-T₄). There were four drip-irrigation frequencies, i.e., once every 2 days (T₁), 4 days (T₂), 6 days (T₃), or 12 days (T₄), who received the same total amounts of fertilizer and water over the 12 experimental days. The results showed that, with the decreases of drip irrigation frequency, tomato yield, the accumulation of N, P and K in plant dry matter, the fertilizer partial productivity, and the nutrient utilization rate first increased and then decreased, peaking at the T₂ treatment. Compared with CK, under the T₂ treatment, plant dry matter accumulation and the accumulation of N, P and K increased by 4.9%, 8.0%, 8.0%, 16.8%, the partial productivity of fertilizer and the utilization efficiency of water increased by 142.8% and 12.2%, the use efficiency of N, P and K was better than CK by 241.4%, 466.6% and 235.9%, respectively, and the tomato yield increased by 12.2%. Under the experimental conditions, drip irrigation with the Yamazaki nutrient solution at a frequency of 4 days could increase the tomato yield, as well as the use efficiency of nutrients and water. Under long-season cultivation, these trends would result in considerable saving of water and fertilizer. Overall, our findings provided a basis for improving the scientific management of water and fertilizers under long-season tomato cultivation in protected facilities.

Climate suitability division of solar greenhouse in Inner Mongolia Autonomous Region, China

WU Rongsheng, WU Ruifen, JIN Linxue, WANG Huizhen, LIU Shuning, JIANG Shaojie, LIU Xiaxia, ZHENG Shiran

2023, 34(5):  1305-1312.  doi:10.13287/j.1001-9332.202305.027

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To resolve the issue of scientific planning and rational layout of different vegetable greenhouses in Inner Mongolia Autonomous Region, we selected the days of low temperature in winter, sunshine hours, overcast days, extreme minimum temperature, days of monsoon disaster, days of snow cover in production season of greenhouse as the climate zoning indicators, based on ground-based observation data from 119 meteorological stations (1991 to 2020) and the growing demand of leafy and fruity vegetables in greenhouse, combined with the analysis of key meteorological factors in production season and the study of meteorological disaster indicators such as low temperature and cold damage, wind disaster, snow disaster. We analyzed the indices, classification and division of comprehensive climate suitability zoning of leafy and fruity vegetables at various slopes (35°, 40°) of solar greenhouse by the weighted sum method. The results showed that the climatic suitability zoning grades of leafy and fruity vegetables at 35° and 40° slope of greenhouse was highly consistent, and that the greenhouse climate suitability of leafy vegetables was higher than that of fruity vegetables in the same region. As the slope increased, wind disaster index decreased and snow disaster index increased. Climate suitability was different in areas affected by wind and snow disasters. The northeast of the study area was mainly affected by snow disasters, and the climate suitability of 40° slope was higher than 35°. The southeast of the study area was mainly affected by wind disasters, and the climate suitability of 35° slope was higher than 40°. Alxa League, Hetao Irrigation District, Tumochuan Plain, most parts of Ordos, southeast of Yanshan foothills and the south of West Liaohe Plain were the most suitable area for the solar greenhouse, because they had the suitable solar and hot resources and the low risks of wind and snow damage, which were also the key development areas of current and future facility agriculture. Due to the deficiency of solar and hot resources, high energy consumption in greenhouse production and frequent snow storms, the area around Khingan range in the northeast of Inner Mongolia was unsuitable for greenhouse.

Effects of microbial diversity loss on the stability of CO₂ production and N₂O emission in agricultural soils

QIAN Liubing, LIANG Shanfeng, WEI Zhanbo, ZHANG Bin

2023, 34(5):  1313-1319.  doi:10.13287/j.1001-9332.202305.030

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The relationship between biodiversity and ecosystem stability is a hot topic in ecology. However, current studies focus mainly on aboveground system with plants, little attention has been paid to belowground system with soils. In this study, we constructed three soil suspensions with varying microbial diversity (10⁰, 10^-2, 10^-6) by the dilution method and inoculated separately into agricultural Mollisols and Oxisols to examine the stability (indicated by resistance and resilience) of soil CO₂ production and N₂O emission to copper pollution and heat stress. Results showed that the stability of CO₂ production in Mollisols was not influenced by microbial diversity loss, while the resistance and resilience of N₂O emission in Mollisols were significantly decreased at the 10^-6 diversity. In the Oxisols, the resistance and resilience of N₂O emission to copper pollution and heat stress started to decrease even at the 10^-2 diversity, and the stability of CO₂ production decreased at the 10^-6 diversity. These results suggested that both soil types and the identity of soil functions influenced the relationship between microbial diversity and the stability of function. It was concluded that soils with ample nutrients and resistant microbial communities tend to have higher functional stability, and that the fundamental soil functions (e.g., CO₂ production) are more resistant and resilient than the specific soil functions (e.g., N₂O emission) in response to environmental stress.

Spatial and temporal trends and drivers of fractional vegetation cover in Heilongjiang Province, China during 1990-2020

ZHAO Nan, ZHAO Yinghui, ZOU Haifeng, Bai Xiaohong, ZHEN Zhen

2023, 34(5):  1320-1330.  doi:10.13287/j.1001-9332.202305.021

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Fractional vegetation cover (FVC) is a quantitative indicator for vegetation growth conditions and ecosystem change. Clarifying the spatial and temporal trends and driving factors of FVC is an important research content of global and regional ecological environment. Based on Google Earth Engine (GEE) cloud computing platform, we estimated FVC in Heilongjiang Province from 1990 to 2020 using the pixel dichotomous model. We analyzed the temporal and spatial trends and drivers of FVC using Mann-Kendall mutation test, Sen's slope analysis with Mann-Kendall significance test, correlation analysis, and structural equation model. The results showed that the estimated FVC based on the pixel dichotomous model had high accuracy (R²>0.7, root mean square error <0.1, relative root mean square error <14%). From 1990 to 2020, the annual average FVC in Heilongjiang was 0.79, with a fluctuating upward trend (0.72-0.85) and an average annual growth rate of 0.4%. The annual average FVC at the municipal administrative districts level also showed different levels of increase of FVC. The area with extremely high FVC dominated the Heilongjiang Province with a gradual increase proportion. The area with increasing trend of FVC accounted for 67.4% of the total area, whereas the area with decreasing trend only accounted for 26.2%, and the rest remained unchanged. The correlation of human activity factor on annual average FVC was higher than that of growing season monthly average meteorological factor. The human activity factor was the main driver for FVC change in Heilongjiang Province, followed by land use type. The total effect of monthly average meteorological factor during the growing season on FVC change was negative. The results would serve as technical support for long-term FVC monitoring and driving force analysis in Heilongjiang Province, and provide a reference for ecological environment restoration and protection, as well as the formulation of related land use policy.

Net ecosystem productivity of Panjin Phragmites australis wetland during 1971 to 2020 and its impact factors

LI Chenglong, ZHOU Guangsheng, ZHOU Mengzi, ZHOU Li, LIU Jie

2023, 34(5):  1331-1340.  doi:10.13287/j.1001-9332.202305.008

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Coastal estuarine wetland ecosystem has strong ability for carbon (C) storage and sequestration. Accurate assessment of C sequestration and its environmental impact factors is the basis of scientific protection and mana-gement of coastal estuarine wetlands. Taking the Panjin reed (Phragmites australis) wetland as the object, we used terrestrial ecosystem model, together with Mann-Kendall mutation test, statistical analysis methods, and scenario simulation experiment, to analyze the temporal characteristics, stability, changing trend of net ecosystem production (NEP) of wetlands and the contribution rate of environmental impact factors to NEP during 1971 to 2020. The results showed that the annual average NEP of Panjin reed wetland was 415.51 g C·m^-2·a^-1 during 1971 to 2020, with a steady increase rate of 1.7 g C·m^-2·a^-1, which would still have a continuous increasing trend in the future. The annual average NEP in spring, summer, autumn, and winter was 33.95, 418.05, -18.71, and -17.78 g C·m^-2·a^-1, with an increase rate of 0.35, 1.26, 0.14 and -0.06 g C·m^-2·a^-1, respectively. In the future, NEP would show an increasing trend in both spring and summer, but a declining trend in both autumn and winter. The contribution rates of environmental impact factors to NEP of Panjin reed wetland depended on temporal scale. At the interannual scale, the contribution rate of precipitation was the highest (37.1%), followed by CO₂ (28.4%), air temperature (25.1%) and photosynthetically active radiation (9.4%). Precipitation mainly affected NEP in both spring and autumn with the contribution rates of 49.5% and 38.8%, while CO₂ concentration (36.9%) and air temperature (-86.7%) were dominant in summer and winter, respectively.

Temporal and spatial variations and influencing factors of gross primary productivity in Changbai Mountain Nature Reserve, China

LI Chunbo, ZHANG Yuan, LIU Yage, WU Jiabing, WANG Anzhi

2023, 34(5):  1341-1348.  doi:10.13287/j.1001-9332.202305.026

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Changbai Mountain Nature Reserve (CNR) is a typical temperate forest ecosystem, and gross primary production (GPP) of which is closely related to topography and climate change. Research on the spatio-temporal variations and influencing factors of GPP in the CNR is of great significance for assessing growth status of vegetation and the quality of ecological environment. We calculated GPP in CNR using the vegetation photosynthesis model (VPM), and analyzed the influences of slope, altitude, temperature, precipitation, and total radiation. The results showed that the range of annual average GPP in CNR was 63-1706 g C·m^-2·a^-1 from 2000 to 2020 and that GPP decreased with the increases of altitude. Temperature played the most important role in driving the spatial varia-tion of GPP, with a significant positive correlation with GPP. During the study period, the overall annual GPP showed a significant increase trend in CNR, with an average annual increase of 13 g C·m^-2·a^-1. The areas with increase of annual GPP accounted for 79.9% of the total area, and the area proportion of annual GPP increase differed in each plant functional type. Annual precipitation was significantly negatively correlated with GPP in 43.2% of CNR, while annual mean temperature and annual total radiation were significantly positively correlated with GPP in 47.2% and 82.4% of CNR. GPP would increase continuously in CNR under the scenario of future global warming.

Impacts of nature reserve policy on regional ecological environment quality: A case study of Sanjiangyuan region

WANG Qingyun, ZHOU Dingyang, AN Pingli, JIANG Guanghui

2023, 34(5):  1349-1359.  doi:10.13287/j.1001-9332.202305.023

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Uncovering the ecological effectiveness of nature reserve policies will help protect and manage nature reserves in the future. Taking Sanjiangyuan region as an example, we examined the impacts of the spatial layout characteristics of natural reserves on the ecological environment quality by constructing the dynamic degree of land use and land cover change index, and depicted the spatial differences of the ecological effectiveness of natural reserve policies both inside and outside the natural reserves. Combined with ordinary least squares and field survey results, we explored the influencing mechanism of nature reserve policies on ecological environment quality. The results showed that the ecological quality of the whole region of Sanjiangyuan had been improved significantly since the implementation of the nature reserve policies, and that the transformation of unused land into ecological land was the most important type of land use change for the ecological environment quality improvement. The ecological effectiveness of large-scale nature reserves with concentrated and contiguous distribution was obvious, while the ecological effectiveness of small-scale nature reserves with scattered distribution and close to the administrative boundaries was relatively small. Although the ecological effectiveness of nature reserves was better than that of non-reserved areas, the ecological improvement of nature reserves and the surrounding areas was synchronous. The nature reserve policy had significantly improved ecological environment quality by implementing ecological protection and restoration projects in nature reserves. Meanwhile, it had alleviated the pressure of farmers and herdsmen's activities on the ecological environment by taking measures such as grazing restriction and guiding conversion of industry and production. In the future, we should promote the construction of ecosystem integrity protection network system with National Park as the core, strengthen the integrated protection and linkage management of National Park and surrounding areas, and help farmers and herdsmen further broaden their livelihoods.

Soil quality evaluation of different land use patterns on the southern and northern Qinghai-Tibet Plateau based on minimal data set

GOU Guohua, FAN Jun, WANG Xi, ZHOU Mingxing, YANG Xueting

2023, 34(5):  1360-1366.  doi:10.13287/j.1001-9332.202305.020

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To evaluate soil quality status of forest, grassland, and cropland in the southern and northern Tibetan Plateau, and to clarify the key influencing factors of productivity levels under three land use types, we measured the basic physical and chemical properties of 101 soil samples collected in the northern and southern Qinghai-Tibet Plateau. Principal component analysis (PCA) was used to select three indicators as the minimum data set (MDS) to comprehensively evaluate soil quality of the southern and northern Qinghai-Tibet Plateau. The result showed that soil physical and chemical properties of the three land use types were significantly different in the north and south. The contents of soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP) and available potassium (AK) in the north were higher than those in the south, while the contents of SOM and TN of forest were signi-ficantly higher than those of cropland and grassland in both the north and south. Soil ammonium (NH₄⁺-N) content showed a pattern of cropland > forest > grassland, with significant difference in the south. Soil nitrate (NO₃^--N) content in the north and south was the highest in the forest. Soil bulk density (BD) and electrical conductivity (EC) of cropland were significantly higher than those of grassland and forest, and that of cropland and grassland in the northern part was higher than that of southern part. Soil pH of grassland in the south was significantly higher than that of forest and cropland, and that of forest was the highest in northern part. The selected indicators for eva-luating soil quality in the north were SOM, AP, and pH, and soil quality index of forest, grassland, and cropland was 0.56, 0.53 and 0.47. The selected indicators were SOM, total phosphorus (TP), and NH₄⁺-N in the south, and soil quality index of grassland, forest and cropland was 0.52, 0.51 and 0.48, respectively. There was a significant correlation between soil quality index obtained by the total data set and the minimum data set, and the regression coefficient was 0.69. Soil quality in the north and south of the Qinghai-Tibet Plateau were grade Ⅲ, and soil organic matter was the main indicator limiting soil quality in this area. Our results provide a scientific basis for eva-luating soil quality and ecological restoration in the Qinghai-Tibet Plateau.

Variations of soil quality in the southern Qinghai-Tibet Plateau during 1980s to 2020s

BAI Jinke, LI Xiaoyu, WANG Li

2023, 34(5):  1367-1374.  doi:10.13287/j.1001-9332.202305.012

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Climate warming and thawing of permafrost in the Qinghai-Tibet Plateau have resulted in soil erosion and the decline of soil quality. Determining the decadal variation of soil quality in the Qinghai-Tibet Plateau is the basis for scientific understanding of soil resources and the key to vegetation restoration and ecological reconstruction. In this study, we used eight indicators (including soil organic matter, total nitrogen, and total phosphorus) to eva-luate soil quality of montane coniferous forest zone (Tibet's natural geographical division zone Ⅱ) and montane shrubby steppe zone (zone Ⅳ) by calculating soil quality index (SQI) in the southern Qinghai-Tibet Plateau in the 1980s and 2020s. Variation partitioning (VPA) was used to examine the drivers for the heterogeneity of the spatial-temporal distribution of soil quality. The results showed that soil quality in each natural zone showed a downward trend in the past 40 years, with SQI of zone Ⅱ decreasing from 0.505 to 0.484 and that of zone Ⅳ decreasing from 0.458 to 0.425. The spatial distribution of soil nutrients and quality was heterogeneous, while soil nutrient conditions and quality in zone Ⅱ were better than those in zone Ⅳ in different periods. The VPA results indicated that the interaction of climate change, land degradation, and vegetation differences was the major cause of temporal variation in soil quality. Differences in climate and vegetation could better explain the spatial variation of SQI.

Land carbon metabolism in Xiamen-Zhangzhou-Quanzhou region based on ecological network analysis

LI Jing, CHEN Songlin, LI Chenxin, ZHOU Ping

2023, 34(5):  1375-1383.  doi:10.13287/j.1001-9332.202305.024

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Discovering the underlying mechanisms between carbon metabolism and carbon balance of human-natural system is of important theoretical and practical significance for reducing regional carbon emissions and promoting low-carbon development. Taking Xiamen-Zhangzhou-Quanzhou region from 2000 to 2020 as an example, we constructed the framework of spatial network model of land carbon metabolism based on carbon flow, and inquired into the spatial and temporal heterogeneity in the carbon metabolic structure, function and ecological relationships by using the ecological network analysis. The results showed that the dominant negative carbon transitions related with land use changes came from the conversion of cultivated land to industrial and transportation land, and that the high value areas of negative carbon flow were mainly distributed in the areas with relatively developed industries in the middle and east parts of Xiamen-Zhangzhou-Quanzhou region. Competition relationships were the dominant type and the spatial expansion was obvious, which led to the decreases of the integral ecological utility index and affected the regional carbon metabolic balance. The ecological network hierarchy of driving weight changed from a pyramid structure to a relatively more regular structure, with the producer contributing the most. The ecological network hie-rarchy of pull weight changed from a pyramid structure to an inverted pyramid structure, mainly due to the excessive increase of industrial and transportation land weights. Low-carbon development should focus on the sources of negative carbon transitions caused by land use conversion and its comprehensive impacts on carbon metabolic balance, to formulate differentiated low-carbon land use patterns and carbon emission reduction policies.

Hyperspectral inversion of soil water and salt information based on fractional order derivative technology

WANG Yijing, CHEN Ruihua, ZHANG Junhua, DING Qidong, LI Xiaolin

2023, 34(5):  1384-1394.  doi:10.13287/j.1001-9332.202305.025

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Accurate and efficient acquisition of soil water and salt information is a prerequisite for the improvement and sustainable utilization of saline lands. With the ground field hyperspectral reflectance and the measured soil water-salt content as data sources, we used the fractional order differentiation (FOD) technique to process hyperspectral data (with a step length of 0.25). The optimal FOD order was explored at the correlation level of spectral data and soil water-salt information. We constructed two-dimensional spectral index, support vector machine regression (SVR) and geographically weighted regression (GWR). The inverse model of soil water-salt content was finally evaluated. The results showed that FOD technique could reduce the hyperspectral noise and explore the potential spectral information to a certain extent, improve the correlation between spectrum and characteristics, with the highest correlation coefficients of 0.98, 1.35 and 0.33. The combination of characteristic bands screened by FOD and two-dimensional spectral index were more sensitive to characteristics than one-dimensional bands, with the optimal responses of order 1.5, 1.0 and 0.75. The optimal combinations of bands for maximum absolute correction coefficient of SMC were 570, 1000, 1010, 1020, 1330 and 2140 nm, pH were 550, 1000, 1380 and 2180 nm, and salt content were 600, 990, 1600 and 1710 nm, respectively. Compared with the original spectral reflectance, the validation coefficients of determination (R_p²) of the optimal order estimation models for SMC, pH, and salinity were improved by 1.87, 0.94 and 0.56, respectively. The overall GWR accuracy in the proposed model was better than SVR, where the GWR optimal order estimation models R_p² were 0.866, 0.904 and 0.647, and the relative per-centage difference were 3.54, 4.25 and 1.86, respectively. The overall spatial distribution of soil water and salt content in the study area was characterized by low in the west and high in the east, with more serious soil alkalinization problems in the northwest and less severe in the northeast. The results would provide scientific basis for the hyperspectral inversion of soil water and salt in the Yellow River Irrigation Area and a new strategy for the implementation and management of precision agriculture in saline soil areas.

Distribution patterns and driving mechanism of soil protozoan community at the different depths of Larix principis-chinensis forest in the Luya Mountain, China

REN Qianru, MAO Xiaoya, QI Xiaojun, LIU Jinxian, JIA Tong, WU Tiehang, CHAI Baofeng

2023, 34(5):  1395-1403.  doi:10.13287/j.1001-9332.202305.031

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To reveal the assembly mechanisms of soil protozoan community in subalpine forest ecosystems, we analyzed the composition and diversity of protozoan communities and their drivers at the six strata (the litter profile, humus profile, 0-10 cm, 10-20 cm, 20-40 cm and 40-80 cm) of soil profiles in subalpine Larix principis-rupprechtii forest in Luya Mountain using Illumina Miseq high-throughput sequencing technology. The results showed that protozoa in the soil profiles belonged to 335 genera, 206 families, 114 orders, 57 classes, 21 phyla, and 8 kingdoms. There were five dominant phyla (relative abundance >1%) and 10 dominant families (relative abundance >5%). The α diversity decreased significantly with increasing soil depth. Results of PCoA analysis showed that the spatial composition and structure of protozoan community differed significantly across soil depths. The results of RDA analysis showed that soil pH and soil water content were important factors driving protozoan community structure across soil profile. Null model analysis suggested that the heterogeneous selection dominated the processes of protozoan community assemblage. Molecular ecological network analysis revealed that the complexity of soil proto-zoan communities decreased continuously with increasing depth. These results elucidate the assembly mechanism of soil microbial community in subalpine forest ecosystem.

Diversity of medium and small-sized soil fauna community in different urban-rural green spaces and its influencing factors in Nanchang, China

JIN Taotao, ZHANG Foyi, ZHENG Weibin, XUE Huajian, LUO Tianyu, ZHANG Miao, LIU Wei, WANG Qiong

2023, 34(5):  1404-1414.  doi:10.13287/j.1001-9332.202305.022

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Urbanization is one of the important factors leading to biodiversity loss and habitat fragmentation. As an important component of urban ecosystem, soil fauna community plays a key role in improving soil structure and fertility, and promoting material circulation of urban ecosystem. To investigate the distribution characteristics of medium and small-sized soil fauna community in green space and the mechanisms underlying their responses to environmental change during urbanization, we selected 27 green space plots with a gradient of urban, suburban, and rural areas in Nanchang City as study objects, and measured plant parameters, soil physicochemical properties, and distribution characteristics of soil fauna community in these plots. The results showed that a total of 1755 soil fauna individuals were captured, belonging to 2 phyla, 11 classes, and 16 orders. The dominant groups were Collembola, Parasiformes, and Acariformes, which accounting for 81.9% of total soil fauna community. The density, Shannon diversity index, and Simpson dominance index of soil fauna community were significantly higher in suburban area than those in rural area. In the green space of the urban-rural gradient, there were large structure variations in different trophic levels of medium and small-sized soil fauna community. Herbivores and macro-predators occupied the largest proportion in rural area, and less in other areas. Results of the redundancy analysis showed the crown diameter, forest density, soil total phosphorus contents were the main environmental factors affecting soil fauna community distribution, with interpretation rate of 55.9%, 14.0% and 9.7%, respectively. Results of the non-metric multidimensional scale analysis showed that there were variations in soil fauna community characteristics in green space of the urban-rural gradient, and that the aboveground vegetation was the dominant factor for this change. This study improved our understanding of urban ecosystem biodiversity in Nanchang, and provided basis for maintaining soil biodiversity and urban green space construction.

Reviews

Research review on the pollution of antibiotic resistance genes in livestock and poultry farming environments

WANG Wenjie, YU Liming, SHAO Mengying, JIA Yantian, LIU Liuqingqing, MA Xiaohan, ZHENG Yu, LIU Yifan, ZHANG Yingzhen, LUO Xianxiang, LI Fengmin, ZHENG Hao

2023, 34(5):  1415-1429.  doi:10.13287/j.1001-9332.202305.032

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Increasingly serious pollution of antibiotic resistance genes (ARGs) caused by the abuse of antibiotics in livestock and poultry industry has raised worldwide concerns. ARGs could spread among various farming environmental media through adsorption, desorption, migration, and also could transfer into human gut microbiome by hori-zontal gene transfer (HGT), posing potential threats to public health. However, the comprehensive review on the pollution patterns, environmental behaviors, and control techniques of ARGs in livestock and poultry environments in view of One Health is still inadequate, resulting in the difficulties in effectively assessing ARGs transmission risk and developing the efficient control strategies. Here, we analyzed the pollution characteristics of typical ARGs in various countries, regions, livestock species, and environmental media, reviewed the critical environmental fate and influencing factors, control strategies, and the shortcomings of current researches about ARGs in the livestock and poultry farming industry combined with One Health philosophy. In particular, we addressed the importance and urgency of identifying the distribution characteristics and environmental process mechanisms of ARGs, and developing green and efficient ARG control means in livestock farming environments. We further proposed gaps and prospects for the future research. It would provide theoretical basis for the research on health risk assessment and technology exploitation of alleviating ARG pollution in livestock farming environment.

Research progress on the measurement of insect sensitive wavelength

QIU Kerui, LI Jinggong, LIU Wen, WANG Xiaoping

2023, 34(5):  1430-1440.  doi:10.13287/j.1001-9332.202305.029

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Insects use subtle and complex visual systems to capture spectral information and guide life activities. Spectral sensitivity of insect describes the relationship between the threshold of insect response to light stimulation and wavelength, which is the physiological basis and necessary condition for the generation of sensitive wavelength. The sensitive wavelength is the light wave with the strong reaction at the physiological or behavioral level of insects, which is the special and specific manifestation of spectral sensitivity. Understanding the physiological basis of insect spectral sensitivity can effectively guide the determination of sensitive wavelength. In this review, we summarized the physiological basis of insect spectral sensitivity, analyzed the intrinsic influence of each link in the photosensitive process on spectral sensitivity, and summarized and compared the measurement methods and research results about the sensitive wavelength of different insect species. The optimal scheme of the sensitive wavelength measurement based on the analysis of the key influencing factors can provide references for the development and improvement of light trapping and control technology. Finally, we proposed that neurological research of spectral sensitivity of insect should be strengthened in the future.