Table of Content

20 September 2019, Volume 28 Issue 9

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The community vegetation composition and stability characteristics of alpine meadow under two grazing modes

SHI Ying, HU Ting-hua, GAO Hong-juan, LUO Qiao-yu, YU Ying-wen

2019, 28(9):  1-10.  DOI: 10.11686/cyxb2018571

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Identifying the optimum grazing management regime is not only beneficial for maintenance of grassland health and productivity, but also for enhancing grassland stability. This research analyzed the importance value of species, the vegetation community characteristics, the biomass composition of functional groups, the Raunkiaer frequency coefficient of species, the degree of grassland succession, and the soil nutrient levels of alpine meadow under cold season grazing (CSG) and warm and cold season grazing (WCSG) in the northeast margin of the Qinghai-Tibetan Plateau. The aim in collecting these data was to clarify the characteristics of vegetation composition change and community stability of grazing grasslands subject to the two different grazing regimes, and provide evidence to identify the suitable grazing management regime. It was found that: 1) The dominant species were Poa crymophila for CSG grassland, and Kobresia humilis and Elymus nutans for WCSG grassland. The aboveground biomass dominated by grasses (86.5%) for CSG grassland, while it dominated by sedges (59.1%) for WCSG grassland. 2) The herbage height, vegetation cover and total aboveground biomass of the CSG grassland were significantly higher than those of the WCSG grassland (P<0.001 or P<0.01), with the CSG being about 6.5, 1.1 and 3.0 times as much as the WCSG, respectively. The number of species present in the WCSG grassland was 1.3 times higher (P<0.05) than in the CSG grassland. 3) The hemicryptophyte presence in the CSG grassland was 1.4 times higher (P<0.001) than in the WCSG grassland. However, the biomass proportion of geophytes and therophytes under the CSG grassland were lower than those under the WCSG grassland (P<0.01 or P<0.05), with the former being 18.2% and 6.8% of the latter for geophytes and therophytes, respectively. 4) The CSG management regime was beneficial to the soil organic C and total N contents of the grassland soils. 5) The Raunkiaer frequency coefficient of species of CSG grasslands was a typical anti- “J” diagram, and the CSG grassland community tended to be relatively mature and stable. This research suggests that the CSG management regime can encourage the alpine meadow succession from a sedge/forb community to a grass/forb community, and can further enhance the grassland community stability.

Soil microorganism dynamics during grassland restoration in sub-humid sandy land

SHUAI Lin-lin, ZHOU Qing-ping, CHEN You-jun, GOU Xiao-lin, ZHOU Rong

2019, 28(9):  11-22.  DOI: 10.11686/cyxb2018564

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Variation in soil microorganism populations has a great influence on soil nutrient cycles during the process of ecological restoration. However, little research has been conducted into variation in soil microorganism populations during the restoration of sub-humid desert land in alpine-cold areas. To investigate this topic, we planted a mixture including Avena sativa, Elymus nutans and Festuca sinensis, among others as an experiment in the restoration of sub-humid desert land. Changes in microbial biomass carbon, nitrogen, phosphorus, microbial biodiversity (phospholipid fatty acids, PLFAs), soil organic carbon, soil total nitrogen and soil total phosphate were checked in the 0-10 cm and 10-20 cm soil layers, annually after re-vegetation, and the changes in soil microorganism populations with time and the correlations between microbial biodiversity, microbial biomass and soil nutrients were analyzed. It was found that re-vegetation increased soil microbial biomass from 8.30 to 10.58 nmol·g^-1 after 4 years and the bacteria still accounted for more than 50% in the total amount of microorganisms. Microbial biomass carbon, nitrogen, and phosphate, microbial biodiversity (i.e. bacteria, fungi, actinomycetes, Gram-negative bacteria, Gram-positive bacteria), soil organic carbon, total nitrogen and total phosphate in the 0-10 cm soil layer were all more than in the 10-20 cm soil layer, throughout the re-vegetation process. Over time, all of these measures showed an initial decrease, and then a tendency to increase. For example, after 1 year’s re-vegetation, soil microbes and nutrients of both soil layers decreased significantly, but soil microbes and nutrients increased in the 0-10 cm soil layer after 2 years re-vegetation. Finally, soil microbe numbers and nutrients increased to values similar to or higher than the controls after 3 or 4 years. In particular, soil organic carbon and microbial biomass nitrogen were significantly (P<0.05) higher in restored grassland than in control plots at the end of the experiment. Soil nutrient levels had extremely positive correlations with soil microbial biomass, and microorganism and bacterial counts (P<0.01), and had positive correlations with counts of soil fungi, actinomycetes, Gram-negative bacteria and Gram-positive bacteria. In summary, artificial re-vegetation with a grass mixture increased soil nutrients and microbes in desert land, thus providing a positive contribution to restoration of a degraded ecosystem in this alpine-cold area where this study was carried out.

Effects of nitrogen addition on the soil bacterial community structure of Stipa baicalensis steppe

LIU Hong-mei, YANG Dian-lin, ZHANG Hai-fang, ZHAO Jian-ning, WANG Hui, ZHANG Nai-qin

2019, 28(9):  23-32.  DOI: 10.11686/cyxb2019241

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This research evaluated the responses of the soil bacterial community structure and diversity to different nitrogen (N) addition levels in Stipa baicalensis steppe. High-throughput sequencing technology was used to study the changes in soil under different N treatments (0, 15, 30, 50, 100, 150, 200, 300 kg N·ha^-1·yr^-1). Soil samples were collected from the 0-10 cm soil layer of the eight different N treatments. The Alpha diversity index of the bacterial community was highest in the mid-range of tested N treatments and lower at low and high N rates. There was no significant difference in Alpha diversity index between the seven N treatments and the control. The dominant bacterial phyla were Acidobacteria (19.01%-38.31%), Proteobacteria (6.64%-17.11%), Actinobacteria (5.07%-16.06%), Verrucomicrobia (3.57%-7.40%), Chloroflexi (3.38%-8.42%), Gemmatimonadetes (0.87%-1.81%). The relative abundance of the dominant bacteria and the structure of the soil bacterial community were both affected by the N addition level. The effect of high N addition on the soil bacterial community structure was greater than that of low N addition. A correlation analysis showed that the bacterial community structure was mainly influenced by the pH, nitrate nitrogen, ammonium nitrogen and total phosphorus levels, with pH being the factor most influencing community structure.

Effects of precipitation and N addition on soil C∶N∶P ecological stoichiometry and plant community composition in a desert steppe of Ningxia, northwestern China

ZHU Wan-wan, WANG Pan, FAN Jin, NIU Yu-bin, YU Hai-long, HUANG Ju-ying

2019, 28(9):  33-44.  DOI: 10.11686/cyxb2019232

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Change in precipitation pattern and increase in atmospheric nitrogen (N) deposition are two important consequences of global change. Soil carbon (C)∶N∶phosphorus (P) ecological stoichiometry could reflect soil organic C level and N and P supply and thus would be closely related to plant growth. Previous studies have reported that both of the changes in precipitation and N deposition may lead to the decoupling of soil C∶N∶P ecological stoichiometry. In order to better understand whether the changes in soil C∶N∶P ecological stoichiometry could affect plant community composition under changing precipitation regimes and increasing atmospheric N deposition, we conducted a field experiment in a desert steppe of Ningxia, northwestern China, involving five precipitation treatments (50% reduction in precipitation, 30% reduction in precipitation, natural precipitation, 30% increase in precipitation, and 50% increase in precipitation) and two N addition treatments (0 and 5 g·m^-2·yr^-1) in 2017, and primarily explored the changes in both soil C∶N∶P ecological stoichiometry and plant community composition and their relationships in August, 2018. It was found that increased precipitation led to decreases in soil organic C, total N, and N∶P, whereas N addition and its interaction with precipitation had little influences on soil C∶N∶P ecological stoichiometry; a moderate increase in precipitation stimulated the growth of most plants and thus increased community diversity. An excessive increase in precipitation resulted in a sharp increase of Artemisia scoparia biomass, combined with the positive effects of N addition, resulting in a reduction of community diversity. To a certain extent, soil water content, total N, organic C, and N∶P were closely related to plant population biomass, while soil water content, organic C, C∶P, and C∶N had closer relationships with diversity indices. Taken together, the results above indicate that precipitation could change N and P relationships between soil supply and plant demand through regulating soil water availability, thus changing plant growth strategy and community diversity; short-term N addition had little effect on soil nutrient availability, consequently, a long-term in situ experiment is needed to further explore mechanisms influencing soil C∶N∶P stoichiometric balance effects on plant community composition under N addition and the interaction between these effects and precipitation change.

A study of root system characteristics and carbon and nitrogen metabolism of alfalfa and four grass forages in monoculture or intercropped

LIN Fang, LIU Xiao-jing, TONG Chang-chun, WU Yong

2019, 28(9):  45-54.  DOI: 10.11686/cyxb2019024

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This study aimed to explore the effects of intercropping on root growth characteristics and carbon and nitrogen metabolism characteristics of some common forage crops. Five species monocultures (alfalfa, triticale, oat, maize and sweet sorghum) were used as reference crops in a field experiment, and four intercropping combinations (alfalfa/triticale, alfalfa/oat, alfalfa/maize and alfalfa/sweet sorghum) were evaluated. The root system growth of alfalfa and the four Poaceae crops under monoculture and intercropping were observed in situ through advanced minirhizotron and computer imaging technology, and the key enzymes and products of carbon and nitrogen metabolism under the four intercropping combinations were studied. It was found that the root parameters were very significantly (P<0.01) and positively correlated with carbon and nitrogen metabolism whether in monoculture or intercropping. Root length and surface area were significantly (P<0.05) and positively correlated with ribulose-1,5-bisphosphate carboxylase (RuBPCase) and nitrate reductase (NR) activity, and also with sucrose phosphate synthase (SPS) and glutamine synthetase (GS) activity, indicating that the root characteristics were consistent with carbon and nitrogen metabolism. Root length, root surface area and other root system parameters of the four tested Poaceae forages were significantly enhanced when intercropped with alfalfa, while alfalfa performance differed between monoculture and intercropped treatments. Root systems of alfalfa intercropped with maize and sweet sorghum were significantly inhibited (significantly smaller than in monocropping), and the alfalfa plants showed weak competitive ability. However, root systems of alfalfa intercropped with triticale and oat were unaffected. When intercropped with alfalfa, functional leaf RuBPCase and NR activities of the four Poaceae species were significantly increased, compared with monocropping. For alfalfa functional leaves, RuBPCase and NR activities of alfalfa plants intercropped with maize and sweet sorghum were significantly lower than in monoculture, while leaf enzyme activities of alfalfa intercropped with triticale and oat were not significantly changed, compared to monoculture. In summary, in this study the root system development of the tested forages mirrored the leaf carbon and nitrogen metabolism differences, and the four grasses outcompeted alfalfa in the intercropping treatments. The two intercropping mixtures alfalfa/triticale and alfalfa/oat had the best overall performance.

Effects of nitrogen and phosphorus fertilizer rate on hay yield and nutritional quality of alfalfa under drip irrigation

MIAO Xiao-rong, SUN Yan-mei, YU Lei, MA Chun-hui, ZHANG Qian-bing

2019, 28(9):  55-66.  DOI: 10.11686/cyxb2018566

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This research explored the effects of different nitrogen and phosphorus fertilizer rates and their interaction on productivity and nutritional value of alfalfa under drip irrigation in the oasis region of Xinjiang. A randomized block design of two nitrogen levels (105 and 210 kg·ha^-1) and four levels of P₂O₅ (0, 50, 100 and 150 kg·ha^-1) was used, making a total of 8 treatments (N₁P₀, N₁P₁, N₁P₂, N₁P₃, N₂P₀, N₂P₁, N₂P₂, N₂P₃). Growth traits, hay yield and the nutritional value of the alfalfa were studied. It was found that under the N₁ treatment, the plant height, stem diameter, growth rate, hay yield and crude protein of alfalfa in the P₂ treatment were greater than other treatments in the first three cuts. However, under the N₂ treatment these same responses were greater than other treatments in the P₁ treatment. The contents of acid detergent fiber and neutral detergent fiber in alfalfa leaves and stems in the P₂ treatment were lower than other treatments at each cut under N₁ and N₂ treatments. The plant height, stem diameter, growth rate, hay yield and crude protein of alfalfa in the N₁ treatment were higher than the N₂ treatment under P₀, P₂ and P₃ treatments. Under the same phosphorus application conditions, the contents of acid detergent fiber and neutral detergent fiber in the N₁ treatment were lower than the N₂ treatment in leaves and stems of alfalfa. Through grey correlation analysis between growth traits index and hay yield of alfalfa it was shown that growth rate and stem diameter had major contributions to hay yield of alfalfa, but the plant height and stem∶leaf ratio had lesser contributions. Through fuzzy similarity priority ratio, the optimal fertilization mode at each cut of alfalfa among the eight treatments under drip irrigation was identified as the N₁P₂ treatment. Under this regime alfalfa produced a high hay yield of 25103.19 kg·ha^-1, with a leaf protein content range of 23.60%-26.47% and a stem protein range of 10.57%-11.76%, together with lower acid detergent fiber contents (leaf: 13.28%-17.41%, stem: 38.63%-47.21%) and lower neutral detergent fiber contents (leaves: 18.18%-22.93%, stem: 49.53%-59.83%). Therefore, the combination of nitrogen (N) at 105 kg·ha^-1 and phosphorus (P₂O₅) at 100 kg·ha^-1 were optimal for high hay yield and improved nutritional quality of alfalfa under drip irrigation in the Xinjiang oasis area.

Effects of straw incorporation with decomposer and film mulched ridge furrow tillage on soil carbon and nitrogen accumulation and soil fertility characters in dryland, China

YANG Feng-ke, HE Bao-lin, ZHANG Guo-ping, ZHANG Li-gong, GAO Ying-ping

2019, 28(9):  67-76.  DOI: 10.11686/cyxb2019186

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Full plastic film mulched ridge-furrow tillage (FMRF) and straw incorporation (S) are two effective strategies for managing soil fertility in semiarid areas. However, the effect of these two practices in combination (FMRF_S) and the key mechanisms by which FMRF_S positively modifies soil fertility characteristics, especially following application of cellulose-decomposing microbial cultures has not been well studied. To address this lack of information, a three-year field experiment with six treatments [conventional planting (CP), conventional planting with straw incorporation (CP_S), conventional planting with straw incorporation plus decomposer (CP_SD), FMRF, FMRF_S, and full plastic film mulched ridge-furrow tillage with straw incorporation (FMRF_SD)], and using a randomized block design with three replications, was conducted from 2015-2017. Soil organic matter (SOM), soil total and available nitrogen, phosphorus and potassium (TN, TP, TK and AN, AP, AK), soil bulk density (BD) and pH values of the 0-30 cm soil profile were examined. Soil organic carbon (SOC) content, SOC and TN accumulation as well as straw sequestration efficiency (CSE) were calculated. Results indicated that FMRF_SD considerably accelerated SOC and TN accumulation in topsoil, significantly (P<0.05) increased the content of SOC, total and available N, P and K, especially the AP and AK content, in 0-30 cm soil profile, via enhanced straw decomposition and nutrient release that more than offset the loss of SOC by mineralization and replenished soil nutrients consumed by crop growth uptake, simultaneously enhancing crop growth and vigor, resulting in increased organic matter (litter and roots, etc.) returned to the soil to complement the soil nutrient reservoir through the synergistic effects of modified soil hydrothermal conditions and the added cellulose-decomposing microbial culture. Measurement results showed that, compared to CP, FMRF_SD cumulatively sequestrated 41.17% of the straw carbon added over 3 years, which led to SOC and TN accumulation being increased by 0.79 mg C·ha^-1 and 0.04 mg N·ha^-1,respectively. This in turn increased the content of TN, TP and TK by 0.05, 0.03 and 3.05 g·kg^-1, respectively, and the contents of AN, AP, and AK by 10.80, 8.90 and 101.50 mg·kg^-1, respectively. These increases corresponded to elevations, respectively, of 6.87%, 6.94%, 15.28%, 10.24%, 56.69%, 55.34%. In addition, the soil BD was lowered by 3.9%, and the soil pH by 0.004 units. With the increase of soil carbon and nitrogen storage, nitrogen, phosphorus and potassium nutrient content and the decrease of soil BD and pH values, the ability of soil to supply plant nutrients was increased, the soil structure and properties were improved, and thus the fertility was significantly improved. Therefore, FMRF_SD is a highly effective management regime for improving soil carbon-nitrogen status and fertility characters in dryland.

Comprehensive evaluation of nutritional value and silage fermentation quality of different oat varieties in central Gansu Province

JU Ze-liang, ZHAO Gui-qin, CHAI Ji-kuan, JIA Zhi-feng, LIANG Guo-ling

2019, 28(9):  77-86.  DOI: 10.11686/cyxb2018542

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This research evaluated seven oat varieties (Longyan No.1, Longyan No.3, Dinyou No.7, Bayou No.9, Bayou No.3, Baiyan No.2 and Jinyan No.17) for fresh biomass yield and fermentation quality, in order to identify the best oat variety for silage making. The experiment was conducted at Huajialing, Tongwei County in Gansu Province, and was harvested at the dough stage of grain fill. Fresh biomass, pH value and nutritional characteristics were measured; microbial counts and community analyses were undertaken by plate-culture. Fresh oat was then chopped to 2 cm lengths and ensiled. These silages were sampled 60 days after ensiling, with 3 replicates for each variety. It was found that: 1) There were significant differences (P<0.01) in fresh biomass and dry matter content between the varieties; Longyan No.3 had the highest fresh biomass (45257 kg·ha^-1), 28.13% higher than Dinyou No.7 (35320 kg·ha^-1). The dry matter content of the seven tested varieties ranged between 31.35% and 35.36%, with Longyan No.3 and Dinyou No.7 the highest. The bacterial counts on plants also significantly differed among the varieties (P<0.01). Lactic acid bacteria on Dinyou No.7 exceeded 105 cfu·g^-1 of fresh matter, higher than the others. 2) The nutrient contents also differed significantly between varieties (P<0.01) after 60 days ensiling. The crude protein contents of Longyan No.3 (10.12%) and Dinyou No.7 (11.09%) were significantly higher than the other varieties (P<0.01). The neutral detergent fiber content of Bayou No.3 (55.78%), Longyan No.3 (54.27%) and Dinyou No.7 (52.16%) were significantly higher than the other varieties (P<0.01). Longyan No.3 also had lower acid detergent fiber and the highest hemicellulose content. 3) The indexes of fermentation quality differed significantly among the varieties (P<0.01). Dinyou No.7 had the lowest pH value (4.13), followed by Longyan No.3 (4.20), and the highest pH value was in Jinyan No.17 (4.53). Silage from Dinyou No.7, Longyan No.3 and Bayou No.3 had higher content of lactic acid, lower total volatile fatty acids and lower ammonia nitrogen content, indicating a good fermentation quality. Bayou No.9 and Jinyan No.17 gave poorer fermentation quality performance. 4) The results of sensory evaluations were in accordance with V-Score evaluations. Longyan No.3 and Dinyou No.7 had the best fermentation quality, with level 1 sensory evaluation. Based on yield, nutritional composition and silage fermentation quality, Longyan No.3 was identified as the best among the tested varieties for planting for silage making in Huajialing and surrounding districts.

A study of crown physiological mechanisms for cold tolerance of different alfalfa varieties in Horqin sandy land

HAO Pei-tong, NING Ya-ming, GAO Qiu, LIU Fang, LI Yu-long, ZHANG Shang-xiong, ZHENG Gui-liang, WANG Xian-guo

2019, 28(9):  87-95.  DOI: 10.11686/cyxb2018565

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This research utilised alfalfa varieties which are widely grown in Horqin sandy land of Inner Mongolia, and explored the rate of occurrence of crown desiccation under simulated overwintering and the effect of different soil water contents at different fall dormancy of alfalfa. The results showed that during simulated overwintering, the cold-resistant WL298 and WL168 varieties exhibited strong desiccation, while for Knight T and Gongnong No.1 varieties crown desiccation was medium. Variety WL363 also displayed medium crown desiccation, attributable to a high accumulation of protective sugar, which enhanced regrowth performance. However, the degree of desiccation of variety Magnum 4015 was low. When soil moisture content was maintained at 90% of field capacity during the winter, WL298, WL168, Knight T and Gongnong No.1 displayed better protective sugars and regrowth performance than Magnum 4015. When the moisture conditions were maintained below 40% of field capacity, the degree of crown contraction of all varieties increased significantly. In these conditions, varieties WL298, WL168, and WL363 had better regrowth performance, while Knight T and Magnum 4015 had poor regrowth.

Physiological responses of pea and nodule symbiosis to water stress

MA Lei, MA Shao-ying, CHEN Gui-ping, CHAI Qiang, LI Sheng

2019, 28(9):  96-109.  DOI: 10.11686/cyxb2018608

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This research investigated the effect of rhizobia inoculation on drought response of pea (Pisum sativum) plants under water stress. A drought-resistant variety ‘Ding wan 8’ and a non-drought resistant variety ‘Long wan 6’ were compared with or without inoculation with rhizobia strains ‘15735’ or ‘Da99’, and under three different water supply conditions: adequate water supply (soil at 75% field capacity), mild stress (soil at 55% field capacity), and severe stress (soil at 35% field capacity), the superoxide dismutase (SOD), catalase (CAT), peroxidase (POD) activity, and proline (Pro), soluble sugar and malondialdehyde (MDA) content in aboveground and root tissues of pea plants under the three water treatments were assayed. It was found after water stress that SOD, POD and CAT activities, and Pro and soluble sugar contents in pea plants inoculated with rhizobia were higher than those without rhizobia inoculation, and in line with those results the content of MDA was lower. Additionally, these responses were more pronounced in ‘Ding wan 8’ inoculated with rhizobium ‘15735’ than in the same variety inoculated with rhizobium ‘Da99’, and also higher than in ‘Long wan 6’ inoculated with rhizobium ‘15735’. A subordination function analysis showed that ‘Ding wan 8’ inoculated with ‘15735’ strain had the highest average score and the strongest drought resistance under the three water treatments. Variety ‘Long wan 6’ inoculated with the ‘Da99’ rhizobium strain showed stronger drought resistance under sufficient water and mild water stress treatments. However, under severe water stress, variety ‘Ding wan 8’ inoculated with ‘Da99’ rhizobium strain showed stronger drought resistance. The results indicate that inoculation with rhizobia enhanced the drought-resistance of pea plants, and the rhizobium strain ‘15735’ had a stronger effect than strain ‘Da99’, while, the variety ‘Ding wan 8’ inoculated with rhizobium strain ‘15735’ still showed greater tolerance to drought than ‘Long wan 6’.

Effect of different cultivation patterns on yield and nutritional contents of photoperiod-sensitive sorghum-sudangrass hybrids

HE Zhen-fu, HE Chun-gui, WANG Guo-dong

2019, 28(9):  110-122.  DOI: 10.11686/cyxb2018279

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The aim of this study was to ascertain the optimal cultivation regime and cutting time of the photoperiod-sensitive sorghum-sudangrass hybrid varieties “Monster” and the brown midrib (BMR) type “Big Kahuna”, when grown on dryland in eastern Gansu. Performance was assessed at 70, 84, 98, 112, 126 and 140 days after planting. Measurements made at each of these 6 growth stages were dry matter yield, total digestible nutrients, and the main nutritional components, including crude protein (CP), neutral detergent fibre (NDF), acid detergent fibre (ADF), total digestible nutrients (TDN), and brix (BX). Four cultivation regimes were compared: plastic-film full mulching on double ridged soil surface (FF-RS), plastic-film full mulching on a flat soil surface (FF-FS), plastic-film semi-mulching on a flat soil surface (FS-FS), and no plastic-film mulching on a flat soil surface (NM-FS, i.e. the traditional planting method). During crop development from 70 to 140 days, CP levels of all cultivation regimes in both varieties fell from 12%-23% to <10% and brix content steadily rose from <4% to 10%-15%, while NDF and ADF gradually rose, apart from a temporary decrease at late head emergence. The BMR genotype, “Big Kahuna”, generally outperformed “Monster” with approximately 15% higher dry matter yield, lower ADF than “Monster” (average across planting regimes 33.13% and 40.39%, respectively), and higher TDN (average 58.14% and 52.24%, respectively). However, the BX content of non-BMR type hybrid, “Monster”, was higher (average 12.41% and 14.59%, respectively). There was no significant effect of cultivation regime on the nutritional contents. However, yield ranked across cultivation regimes: FF-RS (>30 t·ha^-1) =FF-FS>FS-FS>NM-FS (≈20 t·ha^-1), so that TDN yield was enhanced by plastic film mulching. The relative equilibrium point between TDN content and dry matter yield was about 126 days. In conclusion, considering the higher forage production, the BMR type hybrid, “Big Kahuna”, should be used in conjunction with an FF-RS or FF-FS mulching regime and be cut between 120 and 140 days after emergence, for optimal results in this region. These guidelines are best practice for cultivation and utilization for silage forage of the photoperiod-sensitive sorghum-sudangrass hybrids.

Dynamic effects of exogenous fibrolytic enzyme supplementation on nutritive value, fermentation quality and enzyme activities of fermentation total mixed ration

CHEN Guang-ji, WU Jia-hai, SHANG Yi-shun, ZHANG Rong, HE Ting-zhang, WU Yan, LOU Fen, XIONG Jun, GAN Xiao-bo, CHEN Yin-qiong, WANG Pu-chang, HAN Yong-fen, LI Shi-ge, SHU Jian-hong

2019, 28(9):  123-134.  DOI: 10.11686/cyxb2018602

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The objective of this study was to determine the effect of exogenous fibrolytic enzyme (EFE) supplementation in fermentated total mixed ration (FTMR) on the nutritional value, fermentation quality and enzyme activities, and to find out the optimal level of EFE addition. A completely randomized experimental design was adopted, and 5 levels of EFE (0, 0.4, 0.8, 1.6 and 3.2 g·kg^-1 dry matter) were added to FTMR as the 5 experimental treatments. At 7, 14, 35, 49, 70 days after initiation of fermentation, major nutrients, water soluble carbohydrate (WSC), fermentation parameters and activities of four enzymes were determined. It was found: 1) With increased fermentation time, the dry matter (DM), neutral detergent fiber (NDF), acid detergent fiber (ADF), and WSC contents and the activities of the four enzymes monitored showed a decrease (P<0.05), while acetic acid accumulated with time (P<0.05). 2) With increased EFE supplementation, the DM, NDF, ADF and WSC contents, pH value, ammonia nitrogen content, and the activities of carboxyl peptidase and acid protease decreased (P<0.05) until day 35 and then stabilised, while the acetic acid content, and cellulase and xylanase activities increased and stabilized over the same time period (P<0.05). At day 35, the EFE supplementation treatments of 0.8 and 1.6 g·kg^-1 showed lower pH values, NDF and ADF contents, and higher activity of cellulase and xylanase (P<0.05). It was found that the addition of EFE promoted fiber degradation and the accumulation of organic acids through enzymatic activity, inhibited the activities of carboxypeptidase and acidic protease, and reduced the loss of protein in FTMR. The dose effect was additive and the optimum EFE dose was 0.8-1.6 g·kg^-1 DM.

An in vitro study of fermentation properties of four high-quality forages and their mixtures treated with rumen fluid from beef cattle in northwest China

ZHANG Xia, LI Miao-shan, ZHOU En-guang, WANG Hu-cheng

2019, 28(9):  135-145.  DOI: 10.11686/cyxb2018577

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The aim of this study was to investigate the fermentation performance and combination effect of high-quality forages treated with beef cattle rumen fluid in vitro. The four forages studied were packaged silage of maize, oat and alfalfa, and alfalfa hay. The feeds were sourced from the Loess Plateau region. Seven mixtures of the four forages were also tested: C₁ (50% maize silage+50% oat silage), C₂ (50% maize silage+50% alfalfa silage), C₃ (80% maize silage+20% alfalfa hay), C₄ (50% oat silage+50% alfalfa hay), C₅ (70% maize silage+10% oat silage+20% alfalfa silage), C₆ (65% maize silage+15% oat silage+25% alfalfa silage) and C₇ (50% maize silage +20% oat silage+30% alfalfa silage). It was found that: at each time point, the gas production (GP) was highest for maize silage and lowest for alfalfa silage, among the four forages tested singly (P<0.05). For the seven mixtures, the highest and lowest GP was from C₃ and C₄, respectively (P<0.05). Gas production was partitioned into a rapid degradation component (a), a slow degradation component (b), and a gas production rate constant (c). Among the four single feeds, maize silage had the highest value of a, while alfalfa hay had the highest value of c, and values differed significantly (P<0.05) between the four single feeds for both a and c. Among the seven feed mixtures, the highest values of a and c occurred in mixture C₂, while values of c, and potential gas production (a+b) were higher (P<0.05) in mixture C₃, than in the other mixtures. Among the four single feeds, the highest dry matter digestibility (DMD) after 48 h was for maize silage, and there were also significant differences among the other three forages (P<0.05); the pH values differed among the four feeds (P<0.05), and ranged from 6.27 to 6.72; while the NH₃-N concentration was the highest in oat silage (P<0.05). For the seven feed mixtures, the DMD of C₂ was lower than C₅ and C₇ (P<0.05); the pH values ranged from 6.40 to 6.69, and the pH value of C₃ was significantly lower than that of the other six feed mixtures (P<0.05); The NH₃-N concentration of C₁ and C₂ was higher than that of the other five feed mixtures (P<0.05). Among the four single forages, the total volatile fatty acids (TVFA) alfalfa silage and hay were significantly lower than for maize and oat silage (P<0.05). Among the feed mixtures, the TVFA concentrations of C₂ and C₄ were significantly lower than those of C₅ and C₆ (P<0.05). In conclusion, the GP, DMD, TVFA and acetic acid production from maize silage was the highest, while the lowest GP occurred in alfalfa silage. For the seven feed mixtures positive associative effects were detected, and according to the ‘MAFEI’ index, these effects ranked C₄>C₂>C₅>C₁>C₃>C₆>C₇.

Effect of silage feeding rape on the rumen fermentation parameters and microbial diversity of goats

ZHAO Na, YANG Xue-Hai, CHEN Fang, GUO Wan-zheng, LI Xiao-feng, WEI Jin-tao, CHEN Ming-xin, ZHOU Guang-sheng, FU Ting-dong, TAN Zhi-ping

2019, 28(9):  146-154.  DOI: 10.11686/cyxb2018613

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The purpose of this experiment was to study the effects of feeding rape silage on the rumen fermentation parameters and rumen flora composition of goats. Twenty-four Yichang white goats of about 3 months old [average weight (14.83±0.32) kg, 12 male and 12 female] were randomly divided into two groups. The experimental group was fed a total mixed ration containing ensiled forage, and the control group was fed a total mixed ration containing ensiled whole maize. There was a pre-test period of 7 days and a feeding period of 90 days. At the end of the experiment, 6 goats were slaughtered in each group, and the rumen fluid was used to measure pH, ammonia nitrogen, rumen liquid bacterial protein, volatile fatty acids and other indicators. High-throughput sequencing (16S) method was used to analyze the bacterial population structure in the rumen. There was no significant difference in average daily gain, dry matter intake or feed ratio between the experimental group and the control group (P>0.05). There was no significant difference in rumen fluid pH and ammonia nitrogen between goats in the two groups (P>0.05). The contents of bacterial protein and isobutyric acid in rumen fluid of goats fed ensiled forage rape were significantly higher than those of the control group (P<0.05), and differences in levels of other volatile fatty acids did not significantly (P>0.05) between the two groups. There were 15 bacterial taxa with relative abundance greater than 0.1% identified in the experimental group and 14 in the control group. The most taxa common to both experimental and control groups were Bacteroides, Firmicutes, Proteobacteria, Spirochaetae and Saccharibacteria. At the genus level, the most abundant taxon was Prevotella.Compared to the control group, the only significant differences in bacterial abundance observed in the experimental group were a reduction in Prevotella_1 from 21.10% to 16.66% abundance and an increase in ambiguous taxa (for which reads could not be assigned to a species) from 1.95% to 3.19% abundance. For all other taxa, there was no significant difference between the control and experimental groups in the species abundance in the rumen flora. In summary, in this experiment feeding of silage rape maintained the rumen environment and microbial community structure of Yichang white goats without disruption to normal rumen fermentation.

Effects of sweet sorghum forage and grape seed on production performance and blood physiological parameters of small-tailed Han sheep

WANG Ting, WANG Hu-cheng, GOU Na-na, FENG Qiang, HE Chun-gui, SHANG Zhan-huan

2019, 28(9):  155-163.  DOI: 10.11686/cyxb2018578

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This experiment aimed to provide a theoretical basis for safe and efficient utilization of sweet sorghum forage and grape seed. The experiment was conducted in Dingxi City, Gansu Province. A total of 28 Small-tailed Han sheep (17.3±1.20) kg were randomly selected and divided into four groups and fed: sweet sorghum silage+concentrate (SN group), sweet sorghum silage+6% grape seed concentrate (SY group), sweet sorghum hay+concentrate (DN group), sweet sorghum hay+6% grape seed concentrate (DY group). The sheep were weighed before morning feeding on days 1, 30, 60, and 100 of the experiment feeding period. Blood was sampled before the morning feeding on days 20, 50, and 100 days and blood indicators were measured. It was found that: the sweet sorghum forage and grape seed had no significant effect on the dry matter intake (DMI), average daily gain (ADG) or feed conversion ratio (F/G) of the sheep (P>0.05), but the ADG of the SY group was 30% higher than the DN group, and the final weight gain was 15.4% more. The grape seed had no significant effect on the blood physiological parameters of the sheep (P>0.05). The red blood cell (RBC) and hematocrit (HCT) were significantly higher in sweet sorghum silage groups (SN and SY) than sweet sorghum hay groups (DN and DY) (P<0.05). The mean corpuscular hemoglobin (MCH) and mean corpuscular hemoglobin concentration (MCHC) were very significantly higher in sweet sorghum hay groups (DN and DY) than in sweet sorghum silage groups (SN and SY) (P<0.01). Platelet counts (PLT) of the sheep in the sweet sorghum silage groups (SN and SY) on the 20th and 100th days were all significantly lower than that in sweet sorghum hay groups (DN and DY) (P<0.05). The blood physiological parameters of the experimental animals were all within the safe range, but feeding sweet sorghum silage provided a beneficial improvement of red blood cell and platelet indicators of the sheep, and the combination of sweet sorghum silage and grape seeds improved the daily growth rates of the sheep.

Several important issues of soil respiration under climate warming

ZHANG Zhi-qi, ZHANG Li-xu, XU Wei, WANG Hao, WANG Jin-zhou, WANG Wei, HE Jin-sheng

2019, 28(9):  164-173.  DOI: 10.11686/cyxb2018547

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Soil respiration (R_s) is a major pathway through which soil organic carbon returns to the atmosphere, and its response to climate warming has always been the focus of attention in global change ecology researches. During the past thirty years, great progress has been made in understanding mechanisms by which climate warming affects R_s and the impacts of warming on R_s, based on numerous temperature-raising experiments and models. However, most studies are focused on the direct effects of topsoil warming on R_s, and little attention has been paid to processes in the subsoil, and even less to the indirect effects of climate warming through soil animals and soil freezing-thawing processes, which could reduce the confidence in predictions of CO₂ emission under climate warming. Thus, this paper proposes several issues urgently require resolution: 1) the response of deep soil respiration to temperature rise; 2) the effects of soil animals on soil respiration; and 3) the effects of soil freezing-thawing processes on soil respiration. For these three questions, this paper summarizes the research advances, identifies the existing knowledge deficiencies, provides details of opportunities for improvement, and presents suggestions for future research directions. This outline will certainly be helpful for understanding the response of soil respiration to warming and as a catalyst for building more precise carbon cycle models of terrestrial ecosystems.

Advances in understanding molecular mechanisms of K⁺ uptake and transport in higher plants

DUAN Hui-rong, ZHOU Xue-hui, HU Jing, DUAN Xiao-rong, TIAN Fu-ping, CUI Guang-xin, WANG Chun-mei, YANG Hong-shan

2019, 28(9):  174-191.  DOI: 10.11686/cyxb2019123

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As one of the major nutrients, potassium (K⁺) is essential for plant growth and development. Large amounts of K⁺ need to be taken up from the soil and transported throughout the plant. The K⁺ transporters and the K⁺ channels mainly mediate K⁺ transport across the plasma membrane and the tonoplast membrane in plants. The HAK/KUP/KT family and the HKT family are two main groups of proteins which have been widely associated with K⁺ uptake and transport, and they fulfill diverse roles in plant growth processes, salt tolerance and osmotic potential regulation. K⁺-permeable members of HKT family seem to be present in monocots only. The Shaker family, comprising voltage-gated channels, dominate the plasma membrane conductance of K⁺ in most environmental conditions. This review summarizes recent research and progress in understanding of the structure, localization, expression, function and regulation of three main K⁺ transport families. We also propose research hotspots and directions for future K⁺ research.

The impact of different introduced artificial grassland species combinations on community biomass and species diversity in temperate steppe of the Qinghai-Tibetan Plateau

GUAN Hui-ling, FAN Jiang-wen, LI Yu-zhe

2019, 28(9):  192-201.  DOI: 10.11686/cyxb2019100

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The temperate steppe ecosystem on the Qinghai-Tibet Plateau has degenerated greatly in recent decades. Cultivating artificial grassland can alleviate the degradation of natural grassland and result in higher biomass yield. However, the influence and suitability of different species combinations when used to establish artificial grassland in this region remain unclear. Therefore, we selected one natural pasture (NP) as a comparison and three different adjacent artificial seeding regimes [Elymus nutans monoculture (A₁), oat monoculture (A₂) and oat-highland barley-oilseed rape mixed-culture (A₃)] to establish artificial grasslands for experimental comparison in temperate steppe of Guinan county, Qinghai Province. The research aim was to evaluate the influence that different forages (oat and E. nutans; A₁ and A₂) and sowing methods (monoculture or mixed-culture; A₂ and A₃) would have on herbage yield and vegetation community stability. Results were obtained by community investigation and sampling in each plot. In this study, the three artificial grasslands under agricultural management significantly decreased the biomass of poisonous plants (P<0.05), and also significantly improved the proportion of high-quality forage (P<0.05). A₂ provided the highest aboveground biomass (1263.21 g·m^-2) and was 9.77 times more productive than NP and significantly higher than the other three grasslands (P<0.05). The three artificial grasslands did not significantly change the belowground biomass or the total biomass, and no significant difference of these two indices was found among artificial grasslands. Artificial grasslands in this study changed the species composition, especially A₂ and A₃, which were quite different from NP. The Pielou evenness index of A₂ was significantly lower than NP and A₃ (P<0.05), while the Shannon-Wiener index of A₃ was significantly lower than NP (P<0.05). In contrast, A₁ had a high species diversity index, by various measures, including Gleason index, Shannon-Wiener index and Pielou evenness index, was similar to NP. Our results demonstrate that the oat monoculture grassland (A₂) changed the species composition of the NP temperate steppe vegetation community more strongly than other treatments and produced higher aboveground biomass in comparison to E. nutans grassland. By contrast, E. nutans grassland did not greatly improve aboveground biomass, but maintained community species diversity and evenness, which was conducive to retention of a relatively stable community productivity under harsh conditions.

Adaptability of different quinoa germplasm lines in Harbin

LI Ji-kai, WANG Jian-li, SHANG Chen, ZHANG Hai-ling, LIU Jie-lin, CHEN Ji-shan, PAN Duo-feng, LIU Kai

2019, 28(9):  202-208.  DOI: 10.11686/cyxb2019190

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This paper researched the agronomic traits, seed quality traits and lodging resistance of eight quinoa germplasm lines in Harbin, Heilongjiang Province. All the eight tested lines matured normally, with the growth period ranging from 112 to 121 days. The plant height ranged from 133.2 to 173.1 cm, the number of branches per plant was 18.1-23.1, the effective branching rate was 64.34%-72.87%, and the highest yield among the quinoa lines at Harbin was 2966 kg·ha^-1. The ranges for protein, starch, and fat contents were, respectively, 13.74%-14.50%, 42.15%-60.11%, and 4.26%-6.74%, and the range for ash was 3.94%-6.46%. The lodging rate was between 9.00%-13.67%. Based on comprehensive consideration of evaluated yield and seed quality traits, the germplasm line LM-3 had the best performance, and production potential. This material is therefore recommended as suitable to be planted more widely in the Harbin region.

Effects of interplanting with Dolichos lablab on agronomic traits and yield of two varieties of silage maize

LI Ya-jiao, MA Pei-jie, WU Jia-hai, MU Qiong, QIN Tao-ying, WANG Xiao-qiang, MA Ning, ZHANG Rong, LI De-fang, LANG Yong-xiang, WU You-song, TIAN Ying-xue, HAN Yong-fen

2019, 28(9):  209-216.  DOI: 10.11686/cyxb2018569

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This research investigated intercropping of two varieties of silage maize (‘Zheng Silage No. 1’ and ‘Yu silage 23’) with Dolichos lablab with the aim of developing new methods to improve the agronomic traits and yield of silage maize. The experiment was carried out at Jiujiang Township, Songtao County, Guizhou Province, and included three treatments: silage maize with no intercropping, alternate rows of silage maize of D. lablab, and two rows of D. lablab between each row of silage maize. The yield of silage maize was higher for ‘Yu silage 23’ than for ‘Zheng silage No.1’ in all planting regimes and for both varieties yield was highest when interplanted with two rows of D. lablab between each row of maize, (55350 and 75411 kg·ha^-1 FM for ‘Zheng silage No.1’ and ‘Yu silage 23’, respectively), and lowest for the monoculture, with the one-row D. lablab interplanting regime having intermediate yield. The plant height was highest (299 cm for ‘Yu silage 23’) when intercropping one row of D. lablab, but yield was reduced compared to two-row intercropping (62014kg·ha^-1 FM for ‘Yu silage 23’). The leaf length of the agronomic character index of ‘Zheng silage No.1’ increased with the increase in the number of D. lablab interplanting lines, the leaf width and the panicle number decreased, but the variation of the agronomic traits of ‘Yu silage 23’ was just the opposite. The panicle length of ‘Zheng silage No.1’ was 37.24 cm when interplanted with two rows of D. lablab, while that of ‘Yu silage 23’ when not interplanted with D. lablab was 43.57 cm. In variation analysis, the yield and panicle number of two silage maize varieties were larger than 17%. The maximum income from ‘Zheng silage No.1’ and ‘Yu silage 23’ was calculated as 29336and 38 665 CNY·ha^-1, respectively. Thus, the economic benefit of ‘Yu silage 23’ is significantly better than ‘Zheng silage No.1’, and interplanting with two rows of D. lablab per row of maize is recommended.