Acta Prataculturae Sinica

Using the model MaxEnt to predict plant distribution patterns of different functional groups in the alpine meadow ecosystem on Sichuan-Yunnan Plateau

Zhi-yuan YOU, Shu-juan MA, Chang-ting WANG, Lu-ming DING, Xiao-yan SONG, Gao-fei YIN, Jun MAO

2024, 33(3): 1-12. DOI: 10.11686/cyxb2023146

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This research explored the spatial distribution patterns of different main functional groups in the alpine meadow ecosystem on the Sichuan-Yunnan Plateau. Data used were from the second scientific research program on the Qinghai-Tibetan Plateau from 2019 to 2021. The aim was to identify suitable habitats for functional groups， the main climatic factors affecting functional group distribution， and the change trends under climate change. The model MaxEnt was used to predict the special distribution pattern and the main relating climatic factors of four major species from four functional groups （Cyperaceae： Kobresia humilis； Poaceae： Elymus nutans； Mixed grass： Potentilla anserina and Fabaceae： Gueldenstaedtia diversifolia）. The results showed that the areas of suitable habitats for K. humilis， E. nutans， P. anserina and G. diversifolia under the current climate conditions were 110900， 92300， 171200 and 165300 km² respectively， mainly located in the central and northern regions of the Sichuan-Yunnan Plateau. The contribution rate and response curve for environmental factors showed that the habitat suitability of the four species had similarities with their ecological environment requirements. The temperature-related factors such as annual temperature range， isothermality and annual mean temperature were the main environmental factors to affect species distribution. From the future perspective， the suitable habitat of the alpine herbage species will expand under global warming， and the suitable average altitude will increase 100-200 m， but the rate of change will tend to slow down. In conclusion， the species diversity， biomass and stability of alpine meadow ecosystems is predicted to increase with climate change.

Succession mechanism and dynamics in artificial Caragana korshinskii sand-fixing forests of different ages in Baijitan of Lingwu

Shuang YU, Xiao-wei LI, Rui-xia WANG, Jun-long YANG, Long MA

2024, 33(3): 13-23. DOI: 10.11686/cyxb2023150

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This research explored the relationship between the succession sequence of the understory plant community and environmental factors in Caragana korshinskii plantations. We investigated the herbaceous communities in C. korshinskii forests of different ages （3， 5， 10， 20， 30， 40， 50， 60 and 70 years） and determined the soil physical and chemical properties. Two-way indicator species analysis （TWINSPAN）， detrended correspondence analysis （DCA） and redundancy analysis （RDA） were used for quantitative classification and sequencing. The relationship between community distribution and environmental factors was analyzed. It was found that： 1） 27 quadrats in nine plots were divided into a series of four community types by TWINSPAN： Corispermum mongolicum+Agriophyllum squarrosum community→Psammochloa villosa+Artemisia sphaerocephala community→Setaria viridis+Chenopodium album community→Artemisia scoparia+Stipa breviflora community. 2） The results of TWINSPAN and DCA were consistent， and DCA further confirmed the rationality of the TWINSPAN classification. 3） According to the RDA， soil organic carbon and soil pH value were the environmental factors that significantly affected the distribution of the herbage community under the C. korshinskii forest， explaining 19.3% and 13.6% ， and contributing 37.5% and 26.5% （P<0.05）. This research identifies the species succession and its driving factors in the understory herbaceous community in the sand-fixing forest of Baijitan. The results provide a theoretical basis for desertification control and scientific management of the Baijitan nature reserve.

Hydrological effects of highway vegetation slope model under artificial rain conditions

Ya-ru ZHAO, Yun-xiang CAO, Cheng-can YANG, Feng-hou SHI, Hong-xiang FU, Lei CHU

2024, 33(3): 24-33. DOI: 10.11686/cyxb2023137

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Ecological methods are often used in highway slope protection， in particular， the best effect is achieved through vegetation cover. In order to define the optimal slope protection parameters， this study explored the hydrological effects on runoff when different mulch， rainfall intensity， and slope vegetation protection parameters， were tested in a model system utilizing artificial rain. It was found that when the rainfall intensity was 120 mm·h^-1， the runoff of slopes covered with coconut grass blanket， straw fiber blanket and straw curtain was reduced by 23.25%， 15.66% and 17.94%， respectively， compared with that of a bare soil slope， while the water infiltration of the lope increased by 65.19%， 48.10% and 27.89%， respectively. In addition， obvious differences were found in the protective effects of vegetation established for different vegetation growth periods. A model slope with vegetation established 4 months had the smallest runoff， the largest water infiltration， and the strongest resistance to rainwater erosion. At a rainfall intensity of 60 mm·h^-1， no runoff was detected from the model slope due to the vegetation protection effect， compared to bare soil. With successive increases in artificial rainfall intensity， the start time of runoff and water exfiltration in bare soil slope and vegetated slopes incrementally advanced， and the runoff and sediment showed a corresponding increasing trend. In general， a silty subgrade slope mixed sowing with Cynodon dactylon （sowing rate： 12 g·m^-2）， Amorpha fruticosa （sowing rate： 14 g·m^-2）， Lespedeza bicolor （sowing rate： 10 g·m^-2）， and covered with coconut grass blanket （specification： 300 g·m^-2）， under normal management and maintenance conditions， after 3 months of plant growth， exhibited a significantly enhanced ability to resist rainwater erosion. At a rainfall intensity not exceeding 120 mm·h^-1， the combination of vegetation and covering shows extraordinary protective effects. The combination of plants and mulch reduces the impact of rainwater on the slope， and reduces the runoff. In addition， the plant root system facilitates the infiltration of rainwater into the slope， and aids water and soil conservation as well.

The effect of microbial organic fertilizers application on vegetation-soil-microbe in desert steppe

Jun-yao LI, Xing-chi JIANG, Jin-yu HU, Dong-guang WEI, Xue-yong ZHAO, Shao-kun WANG

2024, 33(3): 34-45. DOI: 10.11686/cyxb2023141

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Microbial organic fertilizers （MOF） provide water retention， air permeability and fertility and are prepared from agriculture and animal husbandry waste through aerobic fermentation by high efficiency cellulose decomposer bacteria. An experimental 1 kg·m^-2 application of MOF experiment in the Urat desert steppe showed that applying MOF quickly restored the vegetation-soil-microbial system in degraded desert steppe through promoting vegetation growth， improving soil physical and chemical properties， increasing quantities of microbes and other similar effects. In this experiment it vegetation cover was significantly increased by 33%， soil sticky clay content was significantly increased by 2%， soil total carbon content was significantly increased by 9%， soil total nitrogen content was significantly increased 0.9%； And 11 phyla of soil bacteria and 1 phyla of soil fungi had significant differences in occurrence. Analytically， 92% of the increase in vegetation cover was explained by the MOF application and soil moisture content； 84% of the increase in species richness was explained by the effects of MOF application， soil moisture content and soil electrical conductivity. Overall， these results provide evidence of efficacy， data support and technical support for the restoration of arid desert steppe through application of microbial organic fertilizers.

Effects of compound sand control measures on soil bacterial community structure and function

An-lin WANG, Rui MA, Yan-jun MA, Teng LIU, Yong-sheng TIAN, Zheng-hu DONG, Qiao-di CHAI

2024, 33(3): 46-60. DOI: 10.11686/cyxb2023140

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In this research， the soil of artificial Haloxylon ammodendron forest （Asd） in mobile dune land was taken as the control， and soils from two other compound sand control systems ［nylon grid sand barrier+artificial H. ammodendron forest （Nn） and clay sand barrier+artificial H. ammodendron forest （Cy）］ were selected as experiment treatments. Illumina high-throughput sequencing and PICRUSt2 function prediction technology were used to explore the effects of the compound sand control measures on soil bacterial community structure and function， and redundancy analysis was used to explain the main physical and chemical factors affecting soil bacterial community structure and function. It was found that： 1） The bacterial communities in soil samples from the two composite sand control measures comprised 35 phyla， 90 classes， 172 orders， 259 families and 436 genera. Actinobacteria， Proteobacteria and Chloroflexi were the dominant soil bacterial taxa in the study area， with an average relative abundance of 71.84%. The relative abundance of Actinobacteria was the highest， accounting for 32.16%-37.09%. The occurrences of Bacteroidetes and Cyanobacteria in the Cy plot were significantly higher than those in the Asd plot （P<0.05）. 2） The Chao1 index of soil bacterial diversity in the two plots was significantly higher than that in the mobile dune soil （P<0.05）， but the principal coordinate analysis showed that the soil bacterial community structure of the three plots was similar. 3） Among the 17 secondary functions， carbohydrate metabolism and other functions were the main ecological functions of soil bacteria and showed highly redundant characteristics in different sand control measures areas. 4） Compared with mobile dune soils， the soil organic matter and other nutrients in the area with composite sand control measures showed a common trend of significant increase in bacterial occurrence （P<0.05）， and redundancy analysis showed that physicochemical factors such as soil organic matter and fast-acting potassium levels significantly affected the structure and ecological function of bacterial communities. 5） The dominant phylum among the soil bacteria was significantly correlated with most metabolic functions， and the Mantel test showed a significant positive correlation between differences in soil bacterial community structure and differences in functional potential. In conclusion， the implementation of composite sand control measures improved the desert soil microenvironment， and the research results provide a theoretical basis to manage the ecological restoration of the sandy soil microenvironment.

Changes in phosphorus forms and phosphatase activity in the soil profile after treatment with swine manure and planting with Polygonum hydropiper

Xiu-fang LI, Wen-jing WEI, Yong PU, Ting-xuan LI, Dai-hua YE

2024, 33(3): 61-72. DOI: 10.11686/cyxb2023156

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The excessive application of swine manure in agricultural production can lead to a phosphorus surplus and increased risk of phosphorus losses from soil. In this study， a 3-year field microcosm experiment was conducted to investigate the changes in phosphorus forms and phosphatase activities in soil treated with swine manure and planted with the phosphorus-enriched plant Polygonum hydropiper. Ultimately， the goal of this research was to provide a scientific basis for preventing soil phosphorus losses and enhancing efficient phosphorus extraction by phosphorus-enriched plants such as P. hydropiper. The field microcosm simulation experiment consisted of P. hydropiper planted in soil with three swine manure treatments （1， 2， and 3 kg·m^-2） and a control without swine manure， each with three replicates. During the 3-year field experiment， the aboveground biomass of P. hydropiper and the amount of phosphorus accumulated in its tissues were measured annually. The aboveground parts of the plant and soil at depths of 0-10 cm， 10-20 cm， 20-30 cm， and 30-40 cm were collected every year， and the phosphorus content of the plant and the phosphorus saturation， phosphorus composition， pH， and phosphatase activity along the soil profile were determined. The changes in phosphorus forms and phosphatase activity in the profile of soil treated with swine manure and planted with P. hydropiper were analyzed. The results showed that： 1） During the 3-year field experiment， the aboveground biomass of P. hydropiper increased with increasing swine manure application， as did the amount of phosphorus accumulated in the tissues. In the 3 kg·m^-2 swine manure treatment， the amount of phosphorus in the aboveground parts of P. hydropiper reached 200.31， 195.97， and 195.24 mg·plant^-1 in the first， second， and third year， respectively， remaining stable over the years. 2） During the 3-year experiment， the rate of increase in the phosphorus content in soil in the 0-20 cm and 20-40 cm layers was relatively slow. In the 1 and 2 kg·m^-2 swine manure treatments， the soil phosphorus saturation level was 25% lower than the critical value of soil phosphorus loss. 3） With increasing swine manure application， the phosphorus contents in the 0-10 cm and 10-20 cm soil layers increased， and the application of swine manure at higher concentrations for 3 consecutive years enhanced phosphorus mobility. The pH values of the 0-10 cm and 10-20 cm soil layers gradually decreased， and the phosphatase activities in these layers increased with increasing swine manure application， reaching the highest levels in the 3 kg·m^-2 swine manure treatment. In conclusion， continuous application of swine manure increased the phosphorus contents in the 0-10 cm and 10-20 cm soil layers and enhanced the mobility of phosphorus in the soil profile， and the increase was the largest in the 3 kg·m^-2 treatment. P. hydropiper demonstrated a strong ability to extract excess phosphorus from swine manure-treated soils. Under P. hydropiper cultivation， increasing swine manure application led to a gradual decrease in pH in the 0-10 cm and 10-20 cm soil layers， accompanied by higher activities of acid phosphomonoesterase， alkaline phosphomonoesterase， phytase， and phosphodiesterase in soil. P. hydropiper extracted and accumulated phosphorus， and promoted the transformation of soil phosphorus from less effective fractions to more effective ones， thereby reducing the risk of phosphorus losses from soil.

Interactive effects of intercropping patterns and nitrogen addition on root architectural characteristics of oat and pea in an alpine region

Gen-sheng BAO, Yuan LI, Xiao-yun FENG, Peng ZHANG, Si-yu MENG

2024, 33(3): 73-84. DOI: 10.11686/cyxb2023155

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Interspecific interactions among plant roots are a crucial pathway to improve the productivity of intercropping systems， and the addition of exogenous nitrogen also plays an important role in altering the architectural characteristics of plant roots. However， few studies have explored the interactive effects of intercropping patterns and nitrogen addition on the architectural characteristics of roots in intercropping systems. We conducted a field experiment to examine the effect of intercropping patterns and nitrogen addition on plant biomass and on the morphological and architectural characteristics of roots in oat-pea intercropping systems. We found that the highest values of above- and belowground biomass for oat were in the alternate-row intercropping system with high nitrogen addition， whereas the maximum biomass of pea was in a monoculture with no nitrogen addition. The root morphological traits of oat in the alternate-row intercropping system with high nitrogen addition were superior to those of monocultured oat. In contrast， in pea， the maximum root area， root volume， and number of root tips were in a monoculture with high nitrogen addition， while the highest number of root forks and maximum altitude and magnitude of roots was in a monoculture with no added nitrogen. The maximum values for the altitude and magnitude of oat roots were in an alternate-row intercropping system， while the maximum value for the altitude of pea roots was in a monoculture with no nitrogen addition. Furthermore， nitrogen addition and intercropping simultaneously had positive effects on oat roots through increasing the root area， volume， and magnitude， and promoting lateral root growth， but had negative effects on pea roots by decreasing the number of connections and tips， reducing the root altitude， and suppressing the growth of lateral root growth. Our findings suggest that both nitrogen addition and intercropping can strengthen the nutrient absorption capacity of roots by increasing the contact area between roots and soil， leading to greater accumulation of biomass. These findings support the hypothesis that oat shows stronger competitiveness and higher productivity than pea when grown in oat-pea intercropping systems.

Root and carbon-nitrogen metabolism characteristics of alfalfa-oat mixed stands under continuous intercropping

Xue WANG, Xiao-jing LIU, Jing WANG, Yong WU, Chang-chun TONG

2024, 33(3): 85-96. DOI: 10.11686/cyxb2023143

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This research investigated the root growth characteristics， carbon and nitrogen metabolism characteristics， and the long-term effects of their coupling mechanisms under continuous leguminous-gramineous forage intercropping. A field frame planting， soil culture experiment was conducted to study the root characteristics， carbon and nitrogen metabolism characteristics， and their mutual co-ordination of alfalfa （Medicago sativa）-oat （Avena sativa） intercropping for two consecutive years after planting. Alfalfa monoculture and oat monoculture crops were used as a reference. It was found that the biomass of intercropped oats was significantly higher than monoculture oats （P<0.05）. The root surface area and root average diameter of intercropped oats were significantly higher than monoculture oats （P<0.05）. The transpiration rate （T_r）， net photosynthetic rate（P_n）， stomatal conductance （G_s）， ribulose-1，5-bisphosphate carboxylase （RuBPCase） activity， the activities of four nitrogen metabolism enzymes， and carbohydrate accumulation of intercropped oats were significantly higher than monoculture oats （P<0.05）， while alfalfa showed an opposite trend. Correlation analysis found that the biomass was positively correlated with photosynthetic gas exchange parameters， nitrogen metabolism enzyme activities and root characteristics. Root surface area and root average diameter were significantly positively correlated with T_r， P_n， G_s， nitrate reductase （NR） activity， nitrogen accumulation， and total protein content （P<0.05）. Root volume， root surface area， and root average diameter were highly significantly positively correlated with nitrate reductase activity and glutamate synthase activity （P<0.01）. Thus， the intercropping of alfalfa and oat is more conducive to optimizing the root morphology of oat， while also significantly increasing the net photosynthetic rate and transpiration rate of oat， enhancing the activities of carbon and nitrogen metabolism enzymes such as RuBPCase， NR， and glutamine synthetase in oat， thereby promoting the accumulation of carbohydrate and protein to improve oat biomass and quality. Continuous intercropping weakened the inhibition of root surface area and root volume of alfalfa within the system， and expanded the total root length of alfalfa， but overall， intercropping inhibited root growth and carbon-nitrogen metabolism， which was not conducive to the accumulation of its metabolites and biomass. Moreover， total root length， root surface area， and root volume significantly promote carbon-nitrogen metabolism， the improvement of root system and carbon-nitrogen metabolism in the alfalfa/oat intercropping system effectively increased the biomass and total protein content in the system.

Leaf functional trait characteristics and plasticity of desert steppe plants under nitrogen and phosphorus addition

Ping-an BAO, Kai-yang QIU, Ye-yun HUANG, Si-yao WANG, Lu-yao CUI, Xin-yi LUO, Yun-tao YANG, Ying-zhong XIE

2024, 33(3): 97-106. DOI: 10.11686/cyxb2023176

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Investigating the changes in the functional traits of desert grassland plants under nitrogen （N） and phosphorus （P） addition is crucial for uncovering the mechanisms by which vegetation respond to the environment. In this study， we analyzed the effects of N and P addition on the leaf morphological and chemical traits of the plant community in the desert grassland of Yanchi County， Ningxia. The results showed that the N∶P ratio of the leaf in the plant community was <14， indicating that plant growth in the study area was restricted by N. The addition of P had no significant effect on the leaf functional traits of the plant community. However， N+P addition significantly increased the C/P ratio of the leaf. The addition of N significantly increased the leaf area， specific leaf area， leaf tissue density， and leaf N concentration in the plant community， reflecting that plants adopted a faster nutrient-cycling strategy under changing environmental conditions. Based on plasticity index （PI） rankings， the leaf traits that were sensitive to N and P addition were leaf area， specific leaf area， leaf dry matter content， leaf tissue density， leaf carbon， and leaf nitrogen content （PI>0.5）， with leaf area， specific leaf area， and leaf tissue density showing larger variations. This indicates that the plant community mainly responds to environmental changes by altering its own morphology. The results of correlation analyses showed that there were significant correlations among leaf traits of the plant community， indicative of a synergistic response to changes in nutrient availability. The results of this study provide a theoretical basis for predicting the responses of plants and ecosystems to global climate change， and are crucial for understanding the regional distribution of vegetation and for developing restoration strategies.

A study of mixed sowing effects for oat and common vetch in the Ningxia Yellow River Irrigation Area

Qin FENG, Xiao-li HE, Bin WANG, Teng-fei WANG, Wang NI, Xia MA, Xue-hua MING, Jian-qiang DENG, Jian LAN

2024, 33(3): 107-119. DOI: 10.11686/cyxb2023127

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The ratio of seeding rates in mixed sowings of legumes and grasses is a key factor affecting the yield and quality of mixed grassland. This research investigated the optimal ratio of mixed sowing seeding rates for oat and common vetch in the Ningxia Yellow River Irrigation Area. Six treatments were set up： Four ratios of oat and common vetch ［A₅V₅ （5∶5）， A₆V₄ （6∶4）， A₇V₃ （7∶3） and A₈V₂ （8∶2）］ together with oat and common vetch monocultures， to investigate the production， interspecific competition and nutritional value of the two monocultures and their combinations. It was found that the annual hay yield of the mixed treatments ranged from 14.84 to 17.62 t·ha^-1， which was 4.53% to 24.10% higher than that of oats sown alone and 64.03% to 94.75% higher than that of common vetch sown alone. The A₈V₂ treatment had the highest annual hay yield （17.62 t·ha^-1）， which was significantly higher than that of the single sown and A₅V₅ treatments. The treatment A₆V₄ had the second highest trial yield of 16.61 t·ha^-1. The land equivalent ratio of all mixtures was greater than 1， indicating that the mixtures improved land use efficiency. Interspecies disturbance was less than intraspecies disturbance， and oat and common vetch showed a synergistic relationship， whereby the highest land equivalent ratio of 1.30 was found in the A₈V₂ treatment， indicating that this treatment had the greatest benefit in terms of increased yield. The relative yields of oat were all greater than those of common vetch in the mixed treatments. The aggression intensity of oat was greater than 0 and the competition ratio of oat was greater than that of common vetch， indicating that the aggression of oats was greater than that of common vetch and that oat had a competitive advantage. Regarding the nutritional quality of the forage， there was no significant difference between the mixed treatments. However， A₅V₅ had the numerically highest nutritional quality and A₆V₄ had the numerically highest crude protein yield （1.90 t·ha^-1）. Overall， mixed cropped oat and common vetch had the highest yield， land equivalent ratio， system productivity index （8.94） and net annual income （16418 yuan·ha^-1） with the A₈V₂ mixture. Therefore， it is recommended that oat and common vetch mixtures planted at a ratio of 8∶2 should be promoted in the Ningxia Yellow River Irrigation Area.

Comprehensive evaluation of silage maize hybrids in the Huanghuaihai plain based on mega-environments delineated using envirotyping techniques

Hai-wang YUE, Jian-wei WEI, Guang-cai WANG, Peng-cheng LIU, Shu-ping CHEN, Jun-zhou BU

2024, 33(3): 120-138. DOI: 10.11686/cyxb2023187

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In the context of global climate change， understanding the climate variables that are most strongly associated with environmental kinships can be useful for selecting hybrids that are better suited to growth in environments with large climatic variations. The main goal of this study was to integrate envirotyping techniques （ET） with a genotype-by-yield×trait （GYT） biplot experiment to evaluate the adaptability， productivity， and stability of silage maize （Zea mays） genotypes growing on the Huanghuaihai plain in China. We used ET and meteorological data from 2002 to 2021 to classify the 12 trial sites in a regional trial of silage maize into mega-environments （MEs）. Genotype-by-trait （GT） biplot and GYT biplot experiments were conducted to evaluate 15 silage maize hybrids in the Huanghuaihai National Trial in 2022 in terms of their dry yield， dry matter content， growth period， plant height， ear height， lodging rate， discount rate， empty ear rate， whole plant starch content， neutral detergent fiber content， acid detergent fiber content， and crude protein content. The incidence of common smut， stalk rot， southern leaf blight， curvular leaf spot， and southern corn rust in the 15 silage maize hybrids was also recorded. Additive main effects and multiplicative interaction analyses indicated that the studied agronomic traits were highly significantly （P<0.01） affected by genotype and environment， and the genotype×environment interaction effect reached highly significant levels for all the traits except ear height. Considering 20 years of climate information and 19 environmental covariables， we identi?ed four MEs in the Huanghuaihai plain region； i.e.， the ME analysis grouped locations that share similar long-term weather patterns. Correlation analyses showed that dry yield was significantly and positively correlated with plant height and ear height and negatively correlated with lodging rate and discount rate. The GYT biplot analysis combined with MEs identified the promising genotypes in different MEs. Among the evaluated genotypes， Yudan805 showed outstandingly high yields and good stability in the four MEs， and was the most promising genotype across the four MEs. Wannongkeqingzhu8， Chengdan3601， Zhengda511， and Hengyu1996 showed good productivity and stability in ME₂， ME₃， and ME₄. Genotypes such as Ankeqing2 and KNX2202 were less productive in ME₁ and ME₄， and Jincheng6 was less productive and stable in ME₂ and ME₃. The combination of ET to delineate MEs and the GYT biplot method to evaluate the mean performance and stability of the 15 tested genotypes revealed the overall performance of the different genotypes across a range of environments. These results provide a theoretical basis for integrated multi-trait evaluation of silage maize genotypes growing on the Huanghuaihai plain.

Productivity and adaptability of ‘WL’ alfalfa varieties with different fall dormancy in the extremely arid region of Southern Xinjiang

Yan LI, Fu-long MA, Lu HAN, Hai-zhen WANG

2024, 33(3): 139-149. DOI: 10.11686/cyxb2023165

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To select alfalfa varieties that can grow well in southern Xinjiang， which is an extremely arid area， six ‘WL’ alfalfa varieties with different fall dormancy levels were screened in a 3-year field trial. Their growth characteristics， overwintering rate， regeneration time， leaf∶stem and hay∶fresh ratios， and fresh and hay yields of the early bloom stage were determined over 3 consecutive years. Then， a grey correlation analysis was conducted to determine which factors made the largest contributions to hay yield. The results showed that WL358 was the earliest and WL712 was the latest to regenerate each season. The growth rate was fastest in WL440 （2.30 cm·d^-1） and slowest in WL168 （1.98 cm·d^-1）. The plant height increased during the 3 growing years and decreased with increased frequency of cutting. The growth period gradually shortened from the first cutting to fourth cutting （initial flowering stage）， whereas the growth rate accelerated. The highest average plant height was in WL440 （90.73 cm） over the 3 years， but there was no significant difference in plant height among all the other varieties except for WL343. The leaf∶stem ratio from the first cutting to fourth cutting showed an increasing trend in each year； WL168 had the highest leaf∶stem ratio （0.69） and WL525 had the highest dry∶fresh ratio （0.23）. The fresh and hay yields increased gradually over the 3 growing years， and did not differ significantly among the six varieties （P>0.05）. The highest average fresh and hay yields over the 3 years were in WL358 （98.21 t·ha^-1and 21.26 t·ha^-1， respectively）. The lowest fresh yield was in WL168 （76.37 t·ha^-1） and the lowest hay yield was in WL525 （16.37 t·ha^-1）. The results of the grey correlation analysis showed that the factors affecting hay yield were growth rate， fresh yield， dry∶fresh ratio， plant height， dry weight per plant and leaf∶stem ratio. The six varieties were ranked， from highest comprehensive evaluation score to lowest， as follows： WL358>WL440>WL168>WL343>WL712>WL525. Therefore， WL358 showed the best comprehensive performance and was identified as a cultivar suitable for cultivation in southern Xinjiang.

Effects of straw return on farmland weed abundance and diversity： A meta-analysis

Yao SU, Su-mei YE, Meng-xing LU, Yue MA, Yu-bao WANG, Shan-shan WANG, Ru-shan CHAI, Xin-xin YE, Zhen ZHANG, Chao MA

2024, 33(3): 150-160. DOI: 10.11686/cyxb2023138

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This research involved a meta-analysis of studies on the effects of straw return to farmland on weed control. In this analysis comprehensively assess the role of straw return to farmland in order to develop recommendations to improve the efficiency of straw utilization. In this study， we conducted a meta-analysis involving 426 comparisons of weed abundance and diversity collected from 41 articles on this topic published between 2000 and 2022. The objectives of this study were to assess the effects of straw return on the weed abundance and diversity in agroecosystems of China， as well as the variation of these effects for different crop types， amounts of straw returned， soil textures， climate regimes or other variables. It was found that： 1） Straw return significantly reduced the abundance and diversity of weeds in farmland compared with no straw return， with the suppression effects of -42.4% and -8.5%， respectively. 2） The weed suppression effect of straw return varied under different conditions. Crop species was the key factor affecting the suppression effect of straw return on weed abundance. Returning straw to rice （Oryza sativa）， maize （Zea mays） or rape （Brassica napus） fields significantly reduced weed abundance， with suppression effects of -62.3%， -34.6% and -56.9%， respectively. However， the suppression effect （-7.1%） was not significant when straw was returned to wheat （Triticum aestivum） fields. The amount of straw returned was the key factor influencing the suppression effect of straw return on weed diversity. A regression analysis showed that the suppression effect on weed diversity increased significantly as the amount of straw returned was increased （R²=0.021， P<0.05）. Overall the analysis shows that straw return effectively suppresses weed occurrence and infestation in cropland， but the suppression effect on weed abundance and diversity differs. In conclusion， in the subtropical monsoon climate zone， returning straw to rice fields at a rate>7000 kg·ha^-1 has the best suppression effect on weed abundance， while in the temperate monsoon climate zone， returning the same amount of straw to rape fields can better suppress weed diversity.

Chloroplast genome characteristics of Physocarpus opulifolius ‘Diabolo’ and phylogenetic analysis of the subfamily Spiraeoideae

Xiang HUANG, Meng-yao HE, Zi-xuan WANG, Guang-ming CHU, Ping JIANG

2024, 33(3): 161-173. DOI: 10.11686/cyxb2023153

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Physocarpus opulifolius ‘Diabolo’ is an ornamental flowering shrub that has been introduced into China from North America in recent years. The aims of this study were to determine the structural characteristics of the chloroplast genome of P. opulifolius ‘Diabolo’ and to clarify its taxonomic status within the subfamily Spiraeoideae. The chloroplast genome of P. opulifolius ‘Diabolo’ was sequenced on the Illumina NovaSeq 6000 sequencing platform， and the complete chloroplast genome was assembled and annotated. The chloroplast genome of P. opulifolius ‘Diabolo’ had a typical quadripartite structure， with a total length of 159131 bp， large single copy （LSC） length of 87582 bp， small single copy （SSC） length of 18829 bp， and inverted repeats a （IRa） and inverted repeats b （IRb） length of 26360 bp. A total of 130 genes were annotated， including 83 protein-coding genes， 8 ribosomal RNA （rRNA） genes， 37 transfer RNA （tRNA） genes， and 2 pseudogenes. Twelve codons （UUG， AUU， GUU， GUA， UAA， AAA， UCU， UCC， CCU， ACU， GCU， GGU） were determined. The codon usage bias was mainly affected by natural selection， and mutation was a weak influencing factor. Twenty-seven pairs of long sequence repeats and 87 simple sequence repeat loci were detected. The genes with high nucleotide polymorphism in the chloroplast genome of Physocarpus opulifolius ‘Diabolo’ were psbZ， trnG （UCC）， trnfM （CAU）， trnH （GUG）， psbA， rbcL， rpl20 and rps12. The results of the phylogenetic analysis showed that Physocarpus is closely related to the genus Neillia.

Screening and identification of two strains of nitrogen-fixing bacteria from the silage maize rhizosphere and their roles in plant growth promotion

Chao-nan MENG, Yu-jie ZHAO, Jia-xin CHEN, Yi-lu ZHANG, Yan-jia WANG, Li-rong FENG, Yu-gang SUN, Chang-hong GUO

2024, 33(3): 174-185. DOI: 10.11686/cyxb2023151

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The aim of this study was to screen for high-quality nitrogen-fixing bacteria and evaluate their growth-promoting effects on silage maize （Zea mays）. The dilution spread plate method with Ashby solid medium was used to screen and screen ten strains of nitrogen-fixing bacteria from the rhizosphere soil of silage maize. The nitrogen-fixation capabilities of the strains were analyzed. The results indicated that cultures of ZL-2 and ZL-13 exhibited strong nitrogen-fixing abilities （1.07 and 0.95 μg·mL^-1， respectively）. On the basis of their morphological characteristics， 16S rDNA sequence， and physiological and biochemical characteristics， ZL-2 was identified as Enterobacter cancerogenus， and ZL-13 was identified as Pantoea agglomerans. The growth-promoting characteristics of these two strains were analyzed， and both bacteria were found to secrete ammonium and siderophores， solubilize phosphate， and synthesize indole-3-acetic acid. In a pot experiment， compared with uninoculated silage maize plants， those inoculated with the nitrogen-fixing strains ZL-2 and ZL-13 showed significantly increased plant height， root length， aboveground and underground dry weights， and fresh weight （P<0.05）. In a field experiment， compared with uninoculated silage maize plants， those inoculated with one or both of the nitrogen-fixing strains showed significantly increased plant height， stem diameter， yield， crude protein content， and total phosphorus content （P<0.05）. Silage maize plants inoculated with these two nitrogen-fixing strains showed significantly increased expression levels of genes related to nitrogen metabolism and ammonia assimilation （ZmAMT-4， ZmAMTB， ZmGOGAT2， and ZmGS1-3）（P<0.05）. Therefore， these two nitrogen-fixing bacterial strains have favorable growth-promoting characteristics. Given their important role in enhancing the yield and quality of silage maize， they are valuable resources for the development of microbial agents.

Comparative analysis of growth performance， meat productivity， and meat quality in Hu sheep and its hybrids

Rui ZHANG, Xue-jiao AN, Jian-ye LI, Zeng-kui LU, Chun-e NIU, Zhen-fei XU, Jin-xia ZHANG, Zhi-guang GENG, Yao-jing YUE, Bo-hui YANG

2024, 33(3): 186-197. DOI: 10.11686/cyxb2023157

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This study aimed to investigate the differences in the growth performance， meat productivity， and meat quality of Hu sheep and their hybrids with Southdown and Poll Dorset. Sixteen male lambs， about 3 months old， of Hu×Hu （HH）， Southdown×Hu （NH） and Poll Dorset×Hu （TH） F₁ generation sheep were selected and raised in individual pens under the same nutritional levels and management conditions. The feeding experiment lasted for 95 days （including a 15-day pre-test period）. Feed intake was determined daily from the beginning of the experiment， and body weight and body size were measured every 20 days. Seven sheep close to the average weight of the group were slaughtered at the end of the feeding experiment to measure slaughter performance， carcass traits， and meat quality to further evaluate breeding benefits. The results showed that： 1） The body weights of the TH and NH F₁ generation sheep were significantly higher than that of the HH sheep during the whole experimental period （P<0.05）. Compared with the HH sheep， the TH F₁ generation sheep showed a significantly higher average daily gain weight， with a lower feed conversion ratio （P<0.05）. Compared with the HH sheep， the TH and NH F₁ sheep showed a significantly lower body height and significantly higher heart girth and cannon circumference at the end of the experiment （P<0.05）. 2） Compared with the HH sheep， the TH and NH F₁ generation sheep showed significantly higher live weight， carcass weight， and net meat weight； the NH F₁ generation sheep showed a significantly higher dressing percentage and significantly lower GR value； and the TH F₁ generation sheep showed a significantly higher loin eye area （P<0.05）. 3） The meat pressing loss was significantly lower for the NH F₁ generation sheep than for the HH sheep， while the cooking percentage was significantly higher for NH F₁ generation sheep than for HH and TH F₁ generation sheep （P<0.05）. The protein contents in meat were significantly higher in the NH and TH F₁ generation sheep than in the HH sheep （P<0.05）. 4） The value of the TH and NH F₁ generation sheep （￥320.72 and ￥318.05， respectively） was higher than that of HH sheep （￥249.33）， indicating a breeding benefit of ￥71.39 and ￥68.72 for the TH and NH hybrid sheep， respectively. In conclusion， compared with HH sheep， the hybrid sheep showed stronger growth （hybrid vigor）， a lower feed conversion ratio， improved meat quality， and increased meat palatability and nutritional value. Thus， hybrid breeding benefits the competitiveness of the local sheep industry.

Effect of different ratios of amino acids in low-protein diets on muscle quality， amino acid and fatty acid composition， and vitamin and mineral contents of the longissimus dorsi muscle in Tibetan sheep

Feng-shuo ZHANG, Qiu-rong JI, Ting-li HE, Qu-yang-ang-mao SU, Zhi-you WANG, Sheng-zhen HOU, lin-Sheng GUI

2024, 33(3): 198-208. DOI: 10.11686/cyxb2023191

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The aim of this experiment was to investigate the effects of different ratios of the amino acids lysine and methionine in low-protein diets on the muscle quality， amino acid and fatty acid composition， and vitamin and mineral contents of the longissimus dorsi muscle of Tibetan sheep. Ninety healthy male lambs of Tibetan sheep （plateau type） with similar body weight ［（15.60±0.10） kg］ were selected and randomly divided into three groups of 30. Each group had five replicates of six lambs. The protein level in the dietary concentrate was 12%， and the three groups were as follows： LP-L group （1∶1 lysine to methionine）； LP-M group （2∶1 lysine to methionine）； and LP-H group （3∶1 lysine to methionine）. The total experimental period was 97 days， including a 7-day pre-feeding period and a 90-day feeding period. Analyses of the longissimus dorsi muscle showed that： 1） The thawing loss index was significantly lower in the LP-L group than in the LP-H group （P<0.05）， and the cooking loss index and shear force index were significantly lower in the LP-L group than in the LP-M and LP-H groups （P<0.05）； 2） The different amino acid ratios did not significantly affect the amino acid composition in the longissimus dorsi muscle of each group （P>0.05）； 3） Among the unsaturated fatty acids in the longissimus dorsi muscle， trans-linoleic acid， docosahexatrienoic acid， and pentadecadienoic acid were present at significantly higher levels in the LP-L group than in the LP-M group （P<0.05）； and heptadecadienoic acid， linoleic acid， and α-linoleic acid were present at significantly higher levels in the LP-L group than in the LP-M group and the LP-H group （P<0.05）； 4） The α-vitamin E content， γ-vitamin E content， and vitamin E index of the longissimus dorsi muscle were significantly higher in the LP-L group than in the LP-M group （P<0.05）， while the calcium content was significantly higher in the LP-L group than in the LP-M group （P<0.05）. In conclusion， a diet with a 1∶1 ratio of lysine to methionine can increase the contents of unsaturated fatty acids， vitamins， and minerals in the muscle， thereby improving meat quality， and the ratio of lysine to methionine in the diet does not adversely affect the amino acid composition of the meat.

Fitness cost of the Trp-1999-Leu mutation in plastid ACCase on the growth of Beckmannia syzigachne

Shuang BAI, Qing-hao LYU, Yi-hui LI, Guo-ping LIU, Xiao-yong LUO, Ling-xu LI

2024, 33(3): 209-216. DOI: 10.11686/cyxb2023210

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In this study， we aimed to determine the fitness cost of the Trp-1999-Leu mutation in plastid acetyl co-enzyme A carboxylase （ACCase） on the growth of Beckmannia syzigachne， an important weed of cultivated wheat. The mutant had a homozygous mutation （Leu/Leu， RR） at the 1999 site of ACCase gene’s carboxyl transferase （CT） region， compared with the wild type with Trp/Trp （SS） at the same site. The plant height， aboveground biomass in the early and vegetative stages of growth， fecundity at maturity， and competitiveness with wheat were compared between the wild type and the mutant to clarify the impact of the mutation on the growth of B. syzigachne without herbicide selection pressure. Pot experiments in a greenhouse were conducted to evaluate plant height and aboveground biomass in the early and vegetative stages of growth. The competitiveness of the wild type and the mutant was evaluated using both pot experiments in a greenhouse and field experiments. The results showed that the biomass and plant height of the RR genotype of B. syzigachne were 24.9% and 11.5% lower than that of the SS genotype during 10-15 days of early growth. At the vegetative growth stage， the relative growth rate and net assimilation rate of the RR genotype were 18.2% and 28.6% lower than those of the SS genotype， and the leaf area ratio of the RR genotype was 14.0% higher than that of the SS genotype. However， there was no significant difference in aboveground biomass between the RR and SS genotypes. At the mature stage， the RR genotype allocated less resources to reproductive organs， and the fecundity and total seed weight per plant of the RR genotype were 13.1% and 11.4% lower than their respective values in the SS genotype. In terms of competitiveness， as the density of wheat increased， the aboveground biomass and seed yield of the RR genotype were significantly lower than those of the SS genotype in the greenhouse experiments. This result was confirmed in the field experiment， where the RR genotype showed weaker interspecific competitiveness compared with the SS genotype. Therefore， the ACCase Trp-1999-Leu mutation has significant reproductive and competitive fitness costs in B. syzigachne. These results provide a theoretical basis for the management of this genotype of B. syzigachne.

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