Table of Content

20 June 2022, Volume 31 Issue 6

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A study on restoration potential of degraded grassland on the Qinghai-Tibetan Plateau

Rui-jing WANG, Qi-sheng FENG, Zhe-ren JIN, Jie LIU, Yu-ting ZHAO, Jing GE, Tian-gang LIANG

2022, 31(6):  11-22.  DOI: 10.11686/cyxb2021164

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In recent years， the alpine grassland ecosystem on the Qinghai-Tibetan Plateau has shown an overall improvement， but some areas of grassland are still degenerating to various extents. It is very important to evaluate the grassland status and restoration potential in the Qinghai-Tibetan plateau to support policy-making relating to grassland restoration. Based on meteorological data and MODIS remote sensing images from 2001 to 2019， the Carnegie-Ames-Stanford-Approach （CASA） model and the Thornthwaite Memorial model were used to estimate values for the actual net primary productivity （NPP） and potential net primary productivity （PNPP） across the Qinghai-Tibetan Plateau. The difference between them was used to evaluate the potential benefit of grassland restoration. The main conclusions were as follows： 1） The spatial distribution of NPP over the Qinghai-Tibetan Plateau from 2001 to 2019 was a gradient from high in the southeast to low in the northwest. On the Qinghai-Tibetan Plateau， 41.0% of the grassland areas were being continuously restored， 12.7% of the grassland areas were exhibiting a stable status， and only 3.5% were exhibiting ongoing degradation. Overall， the Plateau grassland is in a state of sustainable restoration. 2） Similarly， the spatial distribution pattern of maximum potential net primary productivity（PNPP_m）in the Qinghai-Tibet Plateau from 2001 to 2019 was significantly higher in the southeast and southwest， and lower in the north. The PNPP_m of individual grassland types was typically about 1000 g C·m^-2. 3） From 2001 to 2019， the grassland recovery potential of the Qinghai-Tibet Plateau was higher in the southwest and southeast， and lower in the north. It was found that most grasslands in Shigatse， southern Ali， Aba Tibetan and Qiang Autonomous Prefecture and Gannan Tibetan Autonomous Prefecture regions have high restoration potential， so that the prospect of grassland restoration in these areas is better. The results of this study provide scientific and theoretical support for policy development relating to grassland restoration on the Qinghai-Tibet Plateau， and provide important data to guide grassland protection and ecosystem restoration on the Qinghai-Tibetan Plateau.

Estimating grassland above ground biomass based on the STARFM algorithm and remote sensing data——A case study in the Sangke grassland in Xiahe County， Gansu Province

Yu-zhuo ZHANG, Zhi-gui YANG, Hong-yan YU, Qiang ZHANG, Shu-xia YANG, Ting ZHAO, Hua-hua XU, Bao-ping MENG, Yan-yan LV

2022, 31(6):  23-34.  DOI: 10.11686/cyxb2021180

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Characteristics of remote sensing data include that they are real-time， dynamic and large-scale， so such data have been widely used in grassland resource monitoring and management research. However， a single remote sensing vegetation index can not meet the needs of temporal and spatial resolution in grassland above ground biomass （AGB） monitoring. Therefore， this study generated a high spatial and temporal resolution vegetation index data set based on a time series of Landsat NDVI and MODIS NDVI data， combined with the spatial and temporal adaptive reflectance fusion model （STARFM）. The data set so generated （NDVI_STARFM） had a temporal resolution 16 d and a spatial resolution 30 m. The optimum grassland above ground biomass inversion model was constructed based on measured grassland above ground biomass and NDVI_STARFM during the grass growth seasons of 2013-2016_. Finally， the spatiotemporal dynamic variation trends of grassland above ground biomass in the study area were analyzed for the period from 2000-2016. It was found that： 1） the optimal estimation model based on NDVI_STARFM was a power model， with an R² of 0.58 and an RMSE 795.62 kg·ha^-1. The performance of this model was lower than that of the Landsat NDVI optimal estimation model （R² =0.76， RMSE=634.83 kg·ha^-1）， but better than that of the MODIS NDVI optimal estimation model （R² =0.24， RMSE=937.79 kg·ha^-1）. 2） The overall accuracy of the optimal estimation model was 84.05%， it was higher than that of MODIS NDVI but lower than that of Landsat NDVI. 3） The grassland above ground biomass showed an increasing trend in most areas from 2000-2016. About 90% of the study area showed an increasing trend with annual increment more than 30 kg·ha^-1， while only 2.3% of the study area showed a decreasing trend.

A bibliometric evaluation of the status of the water conservation function of grassland ecosystems

Xiao-ning ZHANG, Xiao-dan LI, Li-li NIAN, Ying-bo YANG, Xue-lu LIU

2022, 31(6):  35-49.  DOI: 10.11686/cyxb2021160

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Grassland ecosystems are the largest ecosystem category of the terrestrial surface. Changes in grassland water conservation function are an important indicator of ecosystem condition， and respond to regional water cycles and global climate change. Using the Web of Science core collection and the China Knowledge Network database， the knowledge structure of water conservation research in grassland ecosystems was mapped using the visualization software packages VOSviewer and CiteSpace and bibliometric summaries of the relevant literature were compiled. It was found that there was a growing awareness of the field globally， with a fluctuating upward trend in the number of publications. The countries producing the highest numbers of studies were China and the United States， and the top three research institutions were all Chinese institutions； namely the Chinese Academy of Sciences， the University of the Chinese Academy of Sciences， and Beijing Normal University. Core author groups for this literature exhibited a pattern of “large dispersion and small aggregation” with the core authors as the nodes of research and little cooperation among research groups. Major publications included Science of The Total Environment， Catena， Agriculture Ecosystems & Environment， Journal of Ecology and Journal of Soil and Water Conservation. The keywords ecosystem services， land use change， soil moisture， soil physical and chemical properties， and InVEST model were the most frequently mentioned topics of research in this field， both in China and abroad， in recent years. Soil moisture-soil physicochemical properties， combined with remote sensing technology to construct spatial and temporal scale evaluation models have become the frontier of research in this field. This study seeks to understand the current international research frontiers， clarify the developing trends in this field and summarize the research themes in order to promote further development of water conservation research in grassland ecosystems.

Soil microbial biomass carbon and nitrogen levels and their controlling factors in alpine grassland， Qinghai-Tibet Plateau

Yang LI, Yi WANG, Guo-dong HAN, Jian SUN, Ya-feng WANG

2022, 31(6):  50-60.  DOI: 10.11686/cyxb2021161

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The Qinghai-Tibet Plateau is an important geographically isolated and distinctive ecological zone in China. Soil microbes are important drivers of the biogeochemical cycle. Microorganisms are considered the core content of soil biochemical processes. Hence， exploring the content characteristics of soil microbial biomass carbon and nitrogen and their drivers is highly relevant to the understanding of ecosystem function. In this study， a field investigation is conducted in alpine meadows and steppes across the Qinghai-Tibet Plateau. Soil microbial biomass carbon （MBC） and microbial biomass nitrogen （MBN） levels were measured and their relationships with climate， plant community， and soil physicochemical properties were identified. It was found that MBC and MBN contents were higher in alpine meadows than those in alpine steppes. Furthermore， the growing season precipitation （GSP） showed significantly positive correlations with MBC and MBN in both alpine grassland types （P<0.01）， while there were significant negative correlations between the growing season temperature （GST） and MBN in the alpine steppe （P<0.01）. A structural equation model suggested that soil total nitrogen could mediate the MBC and MBN in the alpine meadow， and soil organic carbon may be the key factor of regulating MBC and MBN in the alpine steppe under the influence of growing season precipitation. The findings provide a theoretical framework for the sustainable management of these grassland ecosystems.

Characteristics of understory herb communities across time during restoration in coal mine reclamation areas and their coupling with soil properties

Rui GAO, Ning AI, Guang-quan LIU, Chang-hai LIU, Fang-fang QIANG

2022, 31(6):  61-68.  DOI: 10.11686/cyxb2021151

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This research studied the understory herbaceous plant communities and associated soil factors over years 3-7 of a restoration process at Juxinlong Coal Mine， Ordos Basin， in order to understand the characteristics of understory herbaceous plant communities and their coupling with soil factors across time during the site restoration. Nearby managed grassland and abandoned grassland plots were used as controls. The species composition and soil physical and chemical properties of herbaceous communities in different plots were investigated， and the relationships between herbaceous plant communities and soil factors， and the response mechanisms were studied using the grey correlation coupling model. It was found that： 1） A total of 55 species of herbaceous plants were present in the study area， and 60% of the species present belonged to the families Poaceae， Asteraceae and Fabaceae. 2） With the passage of time during restoration， the number of understory herbaceous plants initially decreased and then increased， and gradually approached to the number of plant species in managed grassland. The Margalef index and Shannon-Wiener index of the studied plots also showed a trend of initial decrease and then increase， while the Pielou index and Simpson index did not change significantly over time. 3） The diversity of herbaceous plant communities in the study area was closely related to soil silt and gravel content， and to soil pH and bulk density. 4） The degree of coupling and correlation between herbaceous plant diversity and soil properties in the study area followed a pattern of “increase-decrease-increase” with the passage of time during the restoration. Among the collected data， the coupling between herbaceous plants and soil in the sample plots after seven years restoration was the highest （R=0.72）. In summary， the correlation between understory herbaceous plant diversity and soil properties in the studied plots exhibited gradual development， but after seven years has not yet reached its climax.

Effects of different nitrogen application rates on antioxidant activity and content of substances involved in osmotic adjustment in Cynodon dactylon under drought stress

Xiao-fan SUN, Yi-long ZHANG, Pei-ying LI, Zong-jiu SUN

2022, 31(6):  69-78.  DOI: 10.11686/cyxb2021179

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This experiment investigated whether application of nitrogen fertilizer could promote the improvement of drought resistance for Cynodon dactylon. Nitrogen fertilizer at various rates including zero nitrogen （0 mmol·L^-1）， low nitrogen （1.5 mmol·L^-1）， medium nitrogen （7.5 mmol·L^-1） and high nitrogen （15.0 mmol·L^-1） was applied to pot of C. dactylon cv.‘Xinnong No.1’with a slowly developing moisture deficit. The turf quality， relative water content， relative electrolyte leakage， malondialdehyde content， antioxidant enzyme activities ［superoxide dismutase （SOD）， peroxidase （POD）， catalase （CAT）］， hydrogen peroxide content， electrical conductivity and levels of substances linked to osmotic adjustment （soluble protein， proline， soluble sugar） were determined at 0， 7 and 14 d after water deficit commencement and 7 d after-watering. Heat map cluster and principal component analysis of drought resistance indexes at 7 and 14 days after water deficit commencement were carried out. The results showed that the effect of nitrogen application rates on turf quality differed depending on the degree of water deficit stress. Turf quality of C. dactylon was better under the high nitrogen treatment （15.0 mmol·L^-1） under normal irrigation and moderate drought stress， and medium nitrogen treatment （7.5 mmol·L^-1） significantly improved turf quality under severe drought stress. Compared with drought control plants， the relative water content， CAT activity， SOD activity， soluble protein， proline and soluble sugar contents of C. dactylon leaves were increased by 60.98%， 154.40%， 163.73%， 61.75%， 144.71% and 31.53%， respectively， with medium nitrogen application under drought stress， and thus maintained higher lawn quality. After re-watering， turf quality of C. dactylon recovered more quickly under medium and high nitrogen treatments， than in low nitrogen treatments. This may be due to reduced damage under drought stress. In conclusion， medium nitrogen application prior to drought stress partially alleviated water deficit damage to C. dactylon seedlings under drought stress.

Change in plant community characteristics along altitudinal gradients in the main browsing areas of Pseudois nayaur in the Helan Mountains

Peng-bo ZHAO, Kai-yang QIU, Ying-zhong XIE, Wang-suo LIU, Xiao-wei LI, Lin CHEN, Ji-fei WANG, Wen-fen MENG, Ye-yun HUANG, Xiao-cong LI, Hao-nan YANG

2022, 31(6):  79-90.  DOI: 10.11686/cyxb2021186

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In this research a vegetation survey was conducted to evaluate the changes in plant community composition and species diversity along altitudinal gradients in the main browsing areas of Pseudois nayaur （blue sheep） in the Helan Mountains. Such data is important for the successful management and protection of P. nayaur. One way ANOVA and regression analyses were performed for data from different altitudes. Changes in plant species composition and species diversity were elucidated for four altitudes （1100-1500 m， 1500-2000 m， 2000-2500 m， and above 2500 m） in the main browsing areas of P. nayaur. The influence of altitude on plant species diversity and the relationships between vegetation and herbivores such as P. nayaur are discussed. There were found to be 87 plant species， 62 genera， and 30 families in total， mainly Poaceae， Rosaceae， and Asteraceae in the P. nayaur browsing areas. Meanwhile， there were differences between altitudes in the number and composition of families， genera， and species. With increasing altitude， the species richness of herbaceous plants also increased， while other indices including the Pielou evenness index， Shannon-Wiener diversity index， and Simpson dominance index all initially decreased and then increased. For shrubs， the species richness and Pielou evenness index decreased with increasing altitude； While the Shannon-Wiener diversity index and the Simpson dominance index both peaked at intermediate altitudes. Therefore， in view of the different plant species diversity patterns at different altitudes， it is suggested that different measures should be taken at different altitudes to prevent vegetation degradation and promote the sustainable conservation of the P. nayaur population.

Seed germination strategy and seedling growth characteristics of heteromorphic seeds of the invasive weed Cenchrus incertus

Ting QU, Li-ye ZHOU

2022, 31(6):  91-100.  DOI: 10.11686/cyxb2021174

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Cenchrus incertus is a noxious invasive weed in Horqin sandy land of Northeastern China. C. incertus is by seed and the seeds are heteromorphic with two phenotypes， a larger mango-shaped type （type M） and a smaller plum-shaped type （type P）. This study explored whether the pericarp of C. incertus has an effect on the germination of heteromorphic seeds， whether the type M seeds has an inhibitory effect on the germination of type P seeds， and whether the germination of two heteromorphic seeds affects the population expansion. In this study， the germination and early seedling growth of M and P type seeds was tested when planted alone or together and imitate the spiniferous bracts （wrapping the two heteromorphic seeds with the cloth again to simulate the spiniferous bracts） ， and the spiniferous bracts under normal condition （only germinating M-type）， single M-type， P-type and P-type seeds in the spiniferous bracts （removing the seedlings from the germinating M-type seeds） were measured to form the seedling growth characteristics. It was found that： 1） The pericarp had no significant effect on the germination of the two heteromorphic seed types. 2） The M type seeds inhibited the germination of P type seeds， the inhibition rate was up to 52.5%. 3） The aboveground biomass and underground biomass of M type seeds in spathes was 0.1298 and 0.1068 g·plant^-1， respectively， greater than P type seeds， and the leaf area and root∶shoot ratios of M type seeds in bracts were， respectively， 84.3% and 356.3% （P<0.05） higher than those of P type seeds. The above studies show： the M type seed in the bract has stronger germinating ability than the P type seed， the M type seed produces seedlings with better survival strategies through more rapid early growth； the P type seed acts as a reserve seed in the current year or the following year to enhance the population numbers.

Phenotype changes during aging over six years of Elymus sibiricus stands and the effects of nutrient addition

Yong-chao ZHANG, Xiao-xing WEI, Guo-ling LIANG, Yan QIN, Wen-hui LIU, Zhi-feng JIA, Yong LIU, Xiang MA

2022, 31(6):  101-111.  DOI: 10.11686/cyxb2021103

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In this study， stands of Elymus sibiricus cv. Qingmu No.1 （which is widely distributed and used in the grasslands of Qinghai Province on the Qinghai-Tibetan plateau） were studied. Three field experiments were set up； namely the normal growth over years one to six from establishment of Qingmu No.1 without fertilizer application， the effect of fertilizer addition to six year old stands and annual fertilizer application over the six year experiment. The aboveground biomass and characteristics relevant to seed production or plant growth， such as specific leaf area were recorded and the effect of fertilizer in the two fertilizer treatments were analyzed. It was found that the aboveground biomass increased from one to three years old and peaked at two-three years old， and then decreased from three years old onwards. We identified four developmental stages over the six-year experiment period： in the first year the initial growth and establishment stage； at two-three years old， the maximum biomass stage； at four-five years old， the decline stage and at six years old and beyond， the aging stage. The single ear weight increased year by year up to five years of age then decreased significantly in the sixth year. The ear dry weight as a proportion of above ground biomass showed the same trend as the single ear weight. In six year old plots of E. sibiricus， nitrogen and phosphorous addition increased the aboveground biomass significantly compared with the control treatment， and the effect of nitrogen was greater than the effect of phosphorous. The biomass of six year old E. sibiricus stands was much higher with the addition of 75 kg·ha^-1 N than at lower rates of N. With the addition of 60 kg·ha^-1 N the single ear weight was much higher than at higher or lower rates of N. With annual fertilization， the aboveground biomass was significantly higher than the control which received no fertilizer. The aboveground biomass was highest under a treatment receiving 60 and 75 kg·ha^-1 of N and P， respectively， and the single ear weight was highest under a treatment receiving 75 kg·ha^-1 of both N and_{P （N75P75）. The proportion of stem in the aboveground biomass increased year by year from year two to year six without fertilizer addition. Under an annual fertilizer addition of 45 kg·ha^-1 N and 90 kg·ha^-1 P， the proportion of stem was decreased， and the proportion of ear and leaf was significantly increased. Long-term fertilizer addition treatments of 60 and 90 kg·ha^-1 of N and P， respectively， and N75P75 also had enhanced the ratio of ear effectively.}

Effect of water deficit stress on the chlorophyll fluorescence parameters of Avena sativa ‘Qingyan No.1’ over the whole crop growth period

Yi-ting JIN, Wen-hui LIU, Kai-qiang LIU, Guo-ling LIANG, Zhi-feng JIA

2022, 31(6):  112-126.  DOI: 10.11686/cyxb2021154

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Drought is one of the key factors limiting the growth of oats （Avena sativa）. This experiment explored the effect of water deficit stress on the photosynthetic system of oats. The oat cultivar studied was ‘Qingyan No.1’ and plants were grown in pots in order to control water supply. A gradient of four water treatments was set up， namely： normal water supply ［CK， 75% field capacity （FWC）］， mild stress （60% FWC）， moderate stress （45% FWC）， and severe stress （30% FWC）. Water deficit stress during the crop growth period was applied at four growth stages， namely： jointing stage water deficit （SJ）， heading stage water deficit （SH）， flowering stage water deficit （SF）， and milky-grain stage water deficit （SM）. Normal water supply throughout the growth period was used as the control treatment （CK）. By exploring the response to water deficit stress of oat chlorophyll fluorescence parameters at different crop growth stages， it was hoped to provide theoretical insight for breeding drought-resistant， water-saving and high-yielding oat cultivars for cultivation on the Tibetan Plateau. It was found that： 1） The overall impact of different water deficit stress levels was： 30% FWC>45% FWC>60% FWC； 2） The overall impact of stress at different growth periods was： SM>SF>SH>SJ； 3） The interaction between stress degree and stress period （Sd×Sp） has the most significant effect on the chlorophyll parameters of oats. The chlorophyll fluorescence parameters were most affected in the treatment with 30% FWC at SM. At this time， non-stomatal factors are the main limitation to photosynthesis， mainly manifested as the inactivation of the PS Ⅱ reaction center and hindered photosynthetic electron transfer. At 60% FWC and SJ， chlorophyll fluorescence parameters were the least affected. The main factor affecting photosynthesis was stomatal limitation； 4） At 45% FWC， in the SH and SF periods the oat plants were able to coordinate transpiration and carbon assimilation through the stomatal conductance of the leaves. 5） Observed changes in chlorophyll fluorescence parameters indirectly reflected changes in the photosynthetic capacity of oats under drought stress. Compared with CK， Y（NO）， NPQ， Y（NPQ） and β increased by 85.52%， 65.21%， 33.76% and 26.60%， respectively， while F_v， F_m， ΦPS Ⅱ， ETR， F_m'， F_s，F₀'， qP， F₀， α and F_v/F_m decreased by 84.86%， 75.41%， 75.03%， 75.00%， 70.89%， 61.38%， 57.73%， 57.06%， 48.86%， 45.61% and 38.50%， respectively. The comprehensive analysis showed that oat chlorophyll fluorescence parameters had different degrees of response to drought during the whole growth period， and the capacity to affect photosynthesis increased synchronously with the water deficit gradient.

A study of the mechanism of drought stress alleviation by exogenous proline applied to Reaumuria soongorica

Shi-ping SU, Yi LI, Xiao-e LIU, Pei-fang CHONG, Li-shan SHAN, You-li HOU

2022, 31(6):  127-138.  DOI: 10.11686/cyxb2021367

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Reaumuria soongorica is an important and extremely drought-resistant tree species found in arid and semi-arid desert ecosystems in the Northwest of China. R. soongorica plays an important role in maintaining the stability of plant communities in semi-desert environments. In recent years， because of frequent occurrence of extreme drought conditions， R. soongorica desert plant communities have sustained large areas of death and are exhibiting degradation. To counter this trend， adoption of artificial measures to improve the drought resistance of plants in arid desert areas may be helpful. In this study， 5 proline （Pro） concentrations （50， 100， 150， 200， 250 mg·L^-1） were applied as a spray treatment to R. soongorica seedlings to investigate the extent of alleviation of damage caused by drought stress. Antioxidant enzyme activities， metabolic regulatory indicators， photosynthetic pigment levels and photosynthetic performance in leaves of R. soongorica seedlings were measured on the day before Pro treatments （day 0）， and on the 1st， 3rd， 6th and 9th days after Pro treatments. A growth index of R. soongorica seedlings was compiled on the 9th day after Pro treatments， in order to elucidate the mechanism of action of Pro protection of plants under drought stress. It was found that the various exogenous Pro treatments had significant effects on the antioxidant enzyme system， metabolic regulation system， photosynthetic pigment levels， photosynthetic performance and growth status of R. soongorica seedlings. Among the measured traits， significant differences between year， among times of spraying， among Pro concentrations， and the interaction between treatment concentration and treatment time were detected. However， chlorophyll a/b （Chl a/b） showed no significant difference among treatment times， and soluble sugar （SS） showed no significant difference among treatment concentrations. The 100 mg·L^-1 Pro treatment had the best overall effect. Soluble protein （SP）， Pro， catalase activity （CAT） and peroxidase activity （POD） on the 9th day after the 100 mg·L^-1 Pro treatment were increased by 4.48%， 131.07%， 30.66% and 12.30%， respectively. SS levels on the 9th day after the 100 mg·L^-1 Pro treatment were decreased by 6.42%， and superoxide dismutase activity （SOD） was decreased by 1.95%. Photosynthetic pigment concentrations ［Chl （a+b）， Chl a， Chl b］ on the 9th day after the 100 mg·L^-1 Pro treatment were decreased by 5.81%， 1.47% and 22.22%， respectively， compared with the results for day 0， and these reductions were the smallest among the five Pro treatments tested. The photosynthetic traits： net photosynthetic rate， stomatal conductance， transpiration rate， intercellular CO₂ concentration and water use efficiency on the 9th day after Pro treatment were decreased by 16.07%， 10.00%， 6.44%， 7.68% and 9.92%， respectively， compared with results for day 0. On the 9th day after treatment， the mean plant height for 100 mg·L^-1 Pro treatment was 2.48 cm， the mean number of side buds was 3.67， the mean growth of side buds was 1.87 cm， and the mean stem diameter at ground level was 0.27 mm； these values were， respectively， 0.68 cm， 0.34， 0.32 cm， and 0.07 mm higher than those of the 250 mg·L^-1 treatment， respectively. Therefore， it was concluded that the 100 mg·L^-1 Pro treatment significantly improved the resistance of R. soongorica plants to drought stress， compared with other Pro rates tested.

Effects of P fertilization rate on tuber yield， quality， plant physiological attributes and P use efficiency of Helianthus tuberosus

Duo ZHANG, Lan-tao LI, Di LIN, Long-hui ZHENG, Sai-nan GENG, Wen-xuan SHI, Kai SHENG, Yu-hong MIAO, Yi-lun WANG

2022, 31(6):  139-149.  DOI: 10.11686/cyxb2021408

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This research aimed to provide reference data to promote efficient utilization and scientific management of phosphate （P） in farmland， and investigated the effect of P fertilization rate on Helianthus tuberosus tuber yield， tuber quality， plant physiological attributes and P use efficiency. Two field experiments were conducted over two consecutive growing seasons （2019-2020） at two sites （Yuanyang and Fangcheng County） in Henan Province， China. The details of the P fertilization treatments in the two growing seasons were as follows： 0， 60， 120， 180 and 240 kg P₂O₅·ha^-1 in 2019 and 0， 45， 90， 135， 180 and 225 kg P₂O₅·ha^-1 in 2020. The tuber yield， quality （inulin and reducing sugar content） at maturity and plant P accumulation， leaf chlorogenic acid content， leaf SPAD value， soluble sugar and soluble protein were determined. In addition， phosphorus harvest index （PHI）， apparent use efficiency of phosphorus （AUP， %） and agronomic efficiency of phosphorus use （AEP， kg·kg^-1） for H. tuberosus were also analyzed. The results indicated： 1） the application of P fertilizer significantly increased the fresh yield of H. tuberosus in both 2019 and 2020 growing seasons. An overall linear effect of P rate on tuber yield was observed with a yield step ［here say if it is a yield increase or yield decrease and at what rate of P fertilization it is seen］. The optimal P fertilization rates for the two growing seasons were 155 and 107 kg·ha^-1 for 2019 and 2020， respectively. Additionally， P application significantly increased the inulin and reducing sugar content of H. tuberosus tubers. Compared with the control treatments （0 kg·ha^-1） in the study， the average increase in the total sugar content was 11.6% in 2019 and 18.3% in 2020. 2） The plant physiological indicators， such as plant P accumulation， leaf chlorogenic acid content， leaf SPAD value， soluble sugar and soluble protein were increased with increasing P rate. 3） The PHI， AUP （%） and AEP （kg·kg^-1） were decreased with increasing the P rates. The values of PHI， AUP and AEP， averaged across P rates and for the two growing season were 0.813， 15.1% and 23.9 kg·kg^-1， respectively. Therefore， high rates of P fertilization in H. tuberosus significantly improved tuber yield and quality and enhanced the physiological and biochemical traits measured. Considering the yield and utilization efficiency of P fertilizer， the recommended P application rates for H. tuberosus， based on this experiment， are between 105-150 kg P₂O₅·ha^-1.

A differential gene expression analysis of miRNA in Dactylis glomerata in response to flooding stress

Xing-yun YANG, Dan-dan QIAO, Ya-jie ZHANG, Shao-qing WANG, Jun-cai REN, Ming-yang LI, Ming-hao QU, Pan-pan SHANG, Cheng YANG, Lin-kai HUANG, Bing ZENG

2022, 31(6):  150-162.  DOI: 10.11686/cyxb2021130

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Waterlogging stress is the main environmental factor that restricts the improvement of yield and quality of orchard grass （Dactylis glomerata） in Southwest China， and it has become a category of abiotic stress that can’t be ignored， from a research perspective. This research aimed to identify functional genes related to waterlogging tolerance of orchard grass， and explore its regulation mechanisms， as a means of improving the waterlogging tolerance of this grass. In this research， the waterlogging tolerant variety “Dian bei” was studied. After being subjected to flooding stress for 0， 8 and 24 h， RNA was extracted from orchard grass leaves and sequencing was carried out using an Illumina Hiseq sequencing platform. A total of 208 differentially expressed genes were identified under flooding stress， 38 genes were up-regulated and 34 genes were down-regulated， accounting for 34.62% of the differentially expressed genes （DEGs）. The genes identified as differentially in “Dian bei” orchard grass under flooding stress mainly belong to five miRNA gene families： miR166， miR167， miR159， miR396 and miR156. Based on the predicted function of target genes of differentially expressed miRNA and functional analysis using GO（gene ontology） and KEGG （kyoto encyclopedia of genes and genomes） of target genes， it was determined that the identified DEGs were mainly involved in plant stress response processes， such as cellular processes， metabolic processes， the IL-17 signaling pathway， Th17 cell differentiation， and others. These results provide initial direction for further study of the molecular regulation and response mechanisms of orchard grass under flooding stress.

The relationship between attack by Prosodes dilaticollis and desert grassland changes in Xinjiang： A case study of southern mountain grassland in Changji

Jiang-long SHEN, Ji-jun CHEN, Abuduwali IMAM, Kun YANG, Ya-ting GUO, Jiang-hua ZHENG

2022, 31(6):  163-177.  DOI: 10.11686/cyxb2021165

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This research explored the coupling relationship between the occurrence of the pest Prosodes dilaticollis and grassland degradation. The impact of the pest on grassland vegetation was quantitatively analyzed， so as to provide a theoretical basis for government officials managing grasslands to scientifically and effectively manage the pests. The study used multi-temporal remote images obtained from the HJ-1 satellite system （HJ-1 satellite system is an earth observation system of China specially used for environmental and disaster monitoring. It is composed of two optical satellites and one radar satellite. It has a variety of optical， infrared and hyperspectral detection means， and has the ability of wide-range， all-weather， all-time and dynamic environmental and disaster monitoring）， land cover product and meteorological data to infer grassland vegetation coverage and climatic drivers. Based on field survey data using overlay analysis， correlation analysis， one-way ANOVA and linear trend analysis were used to quantitatively analyze the interaction between grassland status， climatic factors and P. dilaticollis occurrence， to investigate factors and mechanisms involved in pest outbreaks. The results showed that： there was a significant negative correlation between the insect density and NDVI （normalized differential vegetation index）. The NDVI decreased with the aggravation of pest， and was assigned four damage categories： level 3 （severe）<level 2 （moderate）<level 0 （control）<level 1 （mild）. There was no correlation between the population density of P. dilaticollis and the interannual vegetation coverage variation and there was no significant difference among the damage categories. Bare land such as riverbeds， river flood beaches， and farming-pastoral zone are highly prone to outbreaks of P. dilaticollis， but the insect density is low in grasslands. Sites with a high measured density of P. dilaticollis have no spatial correlation with the degraded areas of grassland. Desert grassland ecosystems are fragile and sensitive. Grassland degradation is the result of the interaction of aridity and overgrazing， and is not directly caused by P. dilaticollis.

Effects of different cultivation measures on the establishment and turf quality characteristics of Achnatherum inebrians lawn

He-na LIAN, Chun-jie LI

2022, 31(6):  178-188.  DOI: 10.11686/cyxb2021396

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Achnatherum inebrians carries the Epichlo? endophytic fungus and as a result exhibits insect resistance and bird repellency. It has great potential as a bird repellent grass species for use on airport surrounds in Northwest China. In order to develop the application of drunken horse grass as a bird repelling ground cover in airport surrounds， different establishment methods were trialed. In particular， the effects on establishment and lawn turf quality of seed soaking with plant growth regulator （0.136% gibberellic acid·indol-3-ylacetic acid·brassinolide wettable powder）， covering with different mulch materials at establishment and a combination of the two， were explored for drunken horse grass lawn. In this experiment， the seedling emergence rate， speed of turf formation， growth rate， density， ground cover， color， texture， uniformity， grass height and other indexes were measured at the seedling emergence and turf formation stages， and the data were subjected to multivariate evaluation. It was found that non-woven fabric mulching and seed soaking with growth regulator+non-woven fabric mulching treatments had the earliest seedling emergence and the fastest turf formation rate. For the treatment of seed soaking with plant growth regulator+non-woven fabric mulching， the growth rate of drunken horse grass was slower； However， the grass density， chlorophyll content and turf uniformity all exceeded those of the control and other treatments. The lawn ground cover was higher under non-woven fabric mulching and seed soaking with plant growth regulator+straw mulching. The multivariate evaluation results showed that the overall quality of drunken horse grass lawn under seed soaking with plant growth regulator+non-woven fabric mulching was the best. This establishment methodology is therefore recommended as the best cultivation measure and suitable for adoption in industry practice.

Dynamic changes in biomass accumulation and nutritional quality of triticeae forages

Yong-liang YOU, Hai-ming ZHAO, Yuan LI, Rui-xin WU, Gui-bo LIU, Jian-dong ZHOU, Jun-feng CHEN

2022, 31(6):  189-201.  DOI: 10.11686/cyxb2021445

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To elucidate the dynamics of biomass accumulation and nutritional quality of triticeae forages， seven species or varieties of triticeae forages （rye， winter triticale， winter wheat， grain-forage triticale， oats， barley， spring triticale） were studied. The growth and development process from the jointing stage to the dough stage and the dynamic changes in dry matter yield and nutrient content were analyzed for crops in the North China Plain from 2016 to 2018. It was found that rye， winter triticale， winter wheat， grain-forage triticale generally reached the milk stage in mid to late May， while oats， barley and spring triticale generally reached the milk stage in early June. The average biomass of the seven tested triticeae forages increased from 2.72 t·ha^-1 at the jointing stage to 10.19 t·ha^-1 at the dough stage. The biomass of winter triticale at each growth stage was significantly higher than that of the other six triticeae forages tested （P<0.05）， and was 61.4% higher than the average for those six crops. The crude protein content of all seven crops decreased gradually as the crops developed and matured， while the starch content increased gradually. The acid detergent fiber and neutral detergent fiber contents increased gradually up to flowering， but decreased slightly thereafter. The software Milk 2006 was used to perform a multi-trait evaluation of the feeding quality of the seven triticeae forages. This analysis indicated that the feeding quality of winter wheat was better than that of the other six tested crops after the booting stage， and the milk yield per ton dry matter was predicted to be 6.9% higher on average than that of the other six crops. Multivariate analysis of biomass and feeding quality across growth stages showed that the milk yield per hectare of winter triticale from the jointing stage to the dough stage was on average 46.3% higher （P<0.05） than that of the other six tested crops. In this research， on the North China Plain， winter triticale performed best among the tested crops and it is recommended that the planting of winter triticale should be promoted.

Effects of addition of Neolamarckia cadamba leaves and chitosan oligosaccharides on fermentation quality and aerobic stability of sugarcane top silage

Xiang GUO, Shuo WU, Ming-yang ZHENG, De-kui CHEN, Xuan ZOU, Xiao-yang CHEN, Wei ZHOU, Qing ZHANG

2022, 31(6):  202-210.  DOI: 10.11686/cyxb2021176

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The purpose of this study was to investigate the effect of adding Neolamarckia cadamba leaves （NCL） on the fermentation quality and aerobic stability of sugarcane top silage with or without chitosan oligosaccharides （CO）. There were 6 treatments in the experiment： No addition （control， CK）， 15%NCL， 30%NCL， CO， 15%NCL+ CO， and 30%NCL+CO. After 210 days， the ensiled materials were analyzed for fermentation quality. The analyses showed that NCL treatments significantly decreased （P<0.05） the pH， the non-protein-N （NPN） and ammonia-N （NH₃-N） contents and significantly increased （P<0.05） the lactic acid （LA）， acetic acid （AA）， crude protein （CP）， and true protein contents. After aerobic exposure for 7 days， the pH （P<0.05）， NPN content， and NH₃-N content （P<0.01） decreased in the NCL treatment， but the CP content increased （P<0.01） in the NCL and CO treatments. In addition， the LA content increased （P<0.01） in the NCL treatment. The 30%NCL， 15%NCL+CO， and 30%NCL+ CO treatments improved （P<0.05） aerobic stability. In summary， the addition of both NCL and CO had positive effects on the fermentation quality and aerobic stability of sugarcane top silage， and the 15%NCL+CO treatment performed better than the other treatments.

The effect of Ageratina adenophora on the structure of various intestinal segments and on intestinal mucosal immune barrier function in rats

Yu-jing CUI, Pei GAO, Juan WEN, Kumi Samuel OKYERE, Yan-chun HU

2022, 31(6):  211-220.  DOI: 10.11686/cyxb2021171

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In order to analyze the toxicity mechanisms of Ageratina adenophora on the intestine of animals， sixteen 7-week-old male Sprague Dawley rats were randomly divided into two groups， a control group （fed 10 g·100 g^-1 body weight （BW） normal diet without A. adenophora powder supplementation） and a treatment group （fed 10 g·100 g^-1 BW of experimental diet prepared by mixing the normal diet and A. adenophora powder in a ratio of 7∶3）， after a 7-day period of adaptation to the normal diet. The test cycle was 14 days. After the experiment， we observed the structural damage， counted the immune cells， and determined the levels of sIgA and inflammatory cytokines of each intestinal segment （duodenum， jejunum， ileum， cecum， colon and rectum） tissue samples. It was found that A. adenophora caused duodenal villi bleeding， mild necrosis， abscission at the top of the duodenum and increased the villi height， crypt depth and and their ratio compared with the control group （P<0.01）. The jejunum was congested with erosive necrosis and abscission at the top of the villi， and also showed a significant increase in the villi height and villi height∶crypt depth ratio （P<0.01）. A large number of intestinal villi at the top of ileum showed coagulated necrosis， accompanied by bleeding， inflammatory infiltration， and a significant increase in villi height， crypt depth and their ratio （P<0.01）. In addition， cecum edema and congestion， colonic lymphocytosis， large numbers of lymphocytes infiltrating and lymphocyte proliferation in the rectum were also observed. Among the intestinal sections the ileum and rectum had the most serious loss of structural integrity with the ileum injury score increasing 722% and rectum score increasing 976%. A. adenophora also significantly increased the number of intestinal intraepithelial lymphocytes， lamina propria lymphocytes and goblet cells （GC_S） （P<0.01） in each intestinal segment. It also significantly increased the secretion of sIgA （P<0.01） and expression of pro-inflammatory factor （IL-1β， IL-2、TNF-α and IFN-γ）， however， the expression of IL-4 and IL-10 was significantly decreased （P<0.01）. In summary， A. adenophora induced an extensive intestinal inflammatory response， destroyed the intestinal mucosal immune barrier and caused intestinal injury.

Research progress on effects of nitrogen deposition on soil nitrogen cycling in grassland ecosystems

Jiao-yun LU, He-shan ZHANG, Hong TIAN, Jun-bo XIONG, Yang LIU

2022, 31(6):  221-234.  DOI: 10.11686/cyxb2021156

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The intensification of human activities and the use of fossil fuels has increased atmospheric nitrogen deposition， which has a significant impact on the nitrogen cycling processes of terrestrial ecosystems， thus affecting ecosystem productivity and stability. Grasslands， are an important component of terrestrial ecosystems， and in many cases are subject to resource loss and nutrient imbalance due to human overuse and lack of awareness of protection needs， in which case the development of animal husbandry enterprises can be severely limited. It is highly relevant to explore the influence of nitrogen deposition on nitrogen cycles of grassland ecosystems for rational development of policy and practice with respect to utilization of grassland resources. This paper tracks published research results at home and abroad and a key finding is that most nitrogen addition inhibits biological nitrogen fixation processes， promotes nitrification， denitrification and mineralization in soils， inhibits the activity of nitrogen fixing microorganisms， and increases the abundance of ammonia-oxidizing bacteria of nitrifying microorganisms and expression of functional genes of denitrifying microorganisms， such as nirK， nirS， nirG and nosZ. However， the responses of the soil nitrogen cycle to nitrogen deposition in a few studies differed from the above due to differences in nitrogen nutrition and nitrogen application measures in a grassland environment. Through summarizing the existing studies， we found that： 1） The effects of nitrogen deposition on the nitrogen cycle differ between studies due to different soil background nutrient levels and nitrogen absorption thresholds； 2） Microorganisms are important participants in the soil nitrogen cycle， and the responses of microorganisms to nitrogen addition differ with different nitrogen application time， frequency and quantity. 3） The various steps of the nitrogen cycle in soils are closely coupled and influence each other， but most of the existing studies only focus on a particular step， and therefore the results do not provide comprehensive insight. Therefore， in future studies， it will be necessary to pay more attention to the study of soil nitrogen cycle microbial changes under particular nitrogen supply conditions in grasslands with different nutrient levels， and consider the multi-step coupling relationship， which is very important to the improvement of grassland ecosystem function and reduction of the threat caused by nitrogen loss from the environment.