2000—2020年青藏高原产水服务时空分布格局及影响因素

产水服务是生态系统服务的重要组成部分,对生态系统平衡和区域可持续发展具有重要意义.青藏高原是“亚洲水塔”,是我国和亚洲的“江河源”,它提供了大量的淡水资源和产水服务.基于InVEST模型分析2000—2020年青藏高原产水服务时空分布及时空演变特征,利用地理探测器方法探究气候、植被、土壤、地形、土地利用等不同因素对青藏高原产水服务空间分异的驱动机制.结果表明,近20年来青藏高原产水量和降水量年际变化呈波动增加的趋势,且具有明显的空间分异性,产水量高值集中分布在青藏高原东南部,低值区主要分布在柴达木盆地和西部的阿里地区;青藏高原产水服务呈增加趋势、减少趋势和无明显变化的面积分别占79.08%,16.45%和4.47%,年降水量与实际蒸散量的交互作用对产水保持服务空间分异的影响最强.研究结果可以为区域水资源综合利用及合理配置提供科学支撑.

氮肥不同施用量下拉萨达孜地区饲用黑麦的生产性能和营养价值

为探究氮肥施用量对拉萨达孜地区饲用黑麦(Secale cereale)生产性能和营养价值的影响,以‘冬牧70’饲用黑麦为研究材料,设置5个不同纯氮施氮水平(0、75、150、225、300 kg·hm^(−2),分别用N_(0)、N_(75)、N_(150)、N_(225)、N_(300)表示),连续两年测定饲草的株高、枝条数、鲜草产量、干草产量以及营养价值相关指标。结果表明,饲用黑麦的生产性能和营养价值在适宜氮肥施用量范围内显著提高(P<0.05)。氮肥施用量为225 kg·hm^(−2)下的饲用黑麦生产性能和营养价值最为优良,2020年和2021年饲草干草产量分别为9898.33和9390.14 kg·hm^(−2);饲草粗蛋白、粗脂肪、粗灰分、淀粉、中性洗涤纤维、酸性洗涤纤维等重要营养价值评价指标均随着氮肥施用量的增加得到改善。从饲草生产性能和营养价值综合考虑,试验区饲用黑麦种植建议氮肥施用量为225 kg·hm^(−2)。

藏北高原高寒草甸地上生物量与气候因子的关系

采用收获法测量了藏北不同海拔高度（4300-4700m）2010年（6-8月）嵩草草甸群落地上总生物量,通过相关分析和多重回归分析法探讨了地上生物量与土壤温度、土壤含水量、空气温度、相对湿度、饱和水汽压亏缺以及比湿的关系。结果表明：总体而言,随着海拔高度的升高地上生物量逐渐增加,地上生物量与相对湿度、比湿以及土壤含水量分别呈极显著的正相关关系,与饱和水汽压亏缺呈极显著的负相关关系,而与土壤温度、空气温度呈不显著的负相关关系;相对湿度和饱和水汽压亏缺共同解释了地上生物量94%的变异,其中相对湿度的贡献较大。相对湿度是决定高寒嵩草草甸沿海拔分布的主导因子。

藏北高原高寒草甸光能利用效率对增温增水的响应

量化植被光能利用效率对增温增水的响应是全球碳循环研究的重要组成部分。为了探讨藏北高原高寒草甸光能利用效率对气候变暖和降水增多的响应,2014年6月在藏北高原高寒草甸布设了1个增温增水实验平台,采用了完整的两因子(增温和增水)实验设计,每个因子设置3个处理水平(不处理、低幅度和高幅度处理),共9个处理组合。设置40 cm和80 cm的开顶式生长箱实现两个幅度的实验增温(分别增加了0.34℃和1.11℃的日最低空气温度),低幅度和高幅度增水处理分别增加了15%和30%的降水。基于中分辨率成像光谱仪的植被光能利用效率算法,利用观测的饱和水汽压差和日最低空气温度模拟了2014—2016年生长季节(6—9月)植被的光能利用效率。结果表明,增温对日最低空气温度(F=39.10,P=0.000)、饱和水汽压差(F=47.45,P=0.000)和光能利用效率(F=4.20,P=0.032)都有显著影响,而增水对饱和水汽压差(F=5.72,P=0.012)有显著影响。增温引起的光能利用效率的变化与增温幅度表现为二次曲线关系,与增温引起的饱和水汽压差的变化量表现为负相关关系。增水处理对光能利用效率无显著影响,且增水引起的光能利用效率的变化与增水引起的饱和水汽压差的变化量呈负相关关系。因此,降水增多可能对藏北高原高寒草甸的光能利用效率无显著影响,而光能利用效率随着增温幅度的变化而变化。

西藏日喀则地区8个引进燕麦品种的生产性能和营养品质比较

草畜平衡对于西藏草原的可持续发展和畜牧业的高效生产非常必要,为了筛选出适宜在西藏日喀则地区种植的燕麦(Avena sativa)品种,缓解过度放牧对天然草地的压力,本研究在西藏日喀则地区南木林县艾玛岗草原站对8个燕麦品种的干重、株高、叶茎比、穗长、穗重和千粒重以及粗蛋白、粗脂肪、粗灰分、酸性洗涤纤维、中性洗涤纤维、木质素指标进行综合评比。生产性能结果表明,青引1号的干草产量最高(12 406.95 kg·hm–2)、穗重最大(3.67 g),青引3号的穗长最长(25.60 cm)、株高最高(159 cm),林纳的千粒重最大(43.94 g);营养品质结果表明:青引2号的粗蛋白含量最高(6.40%),青燕1号的酸性洗涤纤维含量最低(28.55%),林纳的中性洗涤纤维含量最低(52%),青引1号的粗脂肪含量最高(52.7%),青燕1号的灰分含量最高(4.97%),青引2号的木质素含量最低(24.18%)。应用灰色关联度理论对燕麦的产量与营养品质进行综合分析发现,青引1号、青引3号和青引2号适宜在西藏日喀则地区种植推广。

A Meta-analysis of the Effects of Organic and Inorganic Fertilizers on the Soil Microbial Community

In order to investigate the general tendency of soil microbial community responses to fertilizers, a meta-analysis approach was used to synthesise observations on the effects of inorganic and organic fertilizer addition(N: nitrogen;P: phosphorus;NP: nitrogen and phosphorus;PK: phosphorus and potassium;NPK: nitrogen, phosphorus and potassium;OF: organic fertilizer;OF+NPK: organic fertilizer plus NPK) on soil microbial communities. Among the various studies, PK, NPK, OF and OF+NPK addition increased total phospholipid fatty acid(PLFA) by 52.0%, 19.5%, 334.3% and 58.3%, respectively;while NP, OF and OF+NPK addition increased fungi by 5.6%, 21.0% and 8.2%, respectively. NP, NPK and OF addition increased bacteria by 6.4%, 9.8% and 13.3%, respectively;while NP and NPK addition increased actinomycetes by 7.0% and 14.8%, respectively. Addition of ammonium nitrate rather than urea decreased gram-negative bacteria(G–). N addition increased total PLFA、bacteria and actinomycetes in croplands, but decreased fungi and bacteria in forests, and the F/B ratio in grasslands. NPK addition increased total PLFA in forests but not in croplands. The N addition rate was positively correlated with the effects of N addition on gram-positive bacteria(G+) and G–. Therefore, different fertilizers appear to have different effects on the soil microbial community. Organic fertilizers can have a greater positive effect on the soil microbial community than inorganic fertilizers. The effects of fertilizers on the soil microbial community varied with ecosystem types. The effect of N addition on the soil microbial community was related to both the forms of nitrogen that were added and the nitrogen addition rate.

A Meta-analysis of the Effects of Warming and Elevated CO_2 on Soil Microbes

Soil microbes play important roles in terrestrial ecosystem carbon and nitrogen cycling. Climatic warming and elevated CO2 are two aspects of climatic change. In this study, we used a meta-analysis approach to synthesise observations related to the effects of warming and elevated CO2 on soil microbial biomass and community structure. Ecosystem types were mainly grouped into forests and grasslands. Warming methods included open top chambers and infrared radiators. Experimental settings included all-day warming, daytime warming and nighttime warming. Warming increased soil actinomycetes and saprotrophic fungi, while elevated CO2 decreased soil gram-positive bacteria(G+). Mean annual temperature and mean annual precipitation were negatively correlated with warming effects on gram-negative bacteria(G–) and total phospholipid fatty acid(PLFA), respectively. Elevation was positively correlated with the warming effect on total PLFA, bacteria, G+ and G–. Grassland exhibited a positive response of total PLFA and actinomycetes to warming, while forest exhibited a positive response in the ratio of soil fungi to bacteria(F/B ratio) to warming. The open top chamber method increased G–, while the infrared radiator method decreased the F/B ratio. Daytime warming rather than all-day warming increased G–. Our findings indicated that the effects of warming on soil microbes differed with ecosystem types, warming methods, warming times, elevation and local climate conditions.

Comparative Study of the Impact of Drought Stress on P.centrasiaticum at the Seedling Stage in Tibet

Pennisetum centrasiaticum is widely distributed in arid and semi-arid areas of Tibet. Its rhizome system is developed and has strong resistance to adversity. In this study, the physiological characteristics and drought resistance of P.centrasiaticum seedlings from 12 drought-stressed sites in Tibet were examined at the Lhasa Plateau Ecosystem Research Station of the Chinese Academy of Sciences. PEG-6000 solution with five levels of water potential(0, –0.7, –1.4, –2.1, and –2.8 MPa) was used to simulate drought stress, and malondialdehyde(MDA), proline(Pro) and chlorophyll contents were determined. The balance between production and elimination of reactive oxygen species in P.centrasiaticum was destroyed, leading to membrane lipid peroxidation and the production of MDA, and accelerating the decomposition of chlorophyll. P.centrasiaticum absorbed water from the outside to resist drought by secreting proline and other osmotic regulating substances. The Pro and chlorophyll contents in P.centrasiaticum showed a temporary rising trend, and then decreased with the decrease in water potential. MDA content increased with the decrease in water potential. By using the membership function method, the drought resistance of P.centrasiaticum seedlings from the 12 areas was evaluated, and the results showed that the drought resistance at the sites went from strong to weak in this order: Xietongmen > Linzhou > Sog > Damxung > Tingri > Namling > Gyirong > Linzhi > Purang > Dingjie > Longzi > Sa’gya. The drought resistance of P.centrasiaticum was strong in Xietongmen, Linzhou and Sog. Whether P.centrasiaticum from these three areas is suitable for cultivation in arid and semi-arid areas of Tibet needs further study.

The Effect of Higher Warming on Vegetation Indices and Biomass Production is Dampened by Greater Drying in an Alpine Meadow on the Northern Tibetan Plateau

In order to understand whether or not the response of vegetation indices and biomass production to warming varies with warming magnitude,an experiment of field warming at two magnitudes was conducted in an alpine meadow on the northern Tibetan Plateau beginning in late June,2013.The normalized difference vegetation index（NDVI）,green normalized difference vegetation index（GNDVI） and soil adjusted vegetation index（SAVI） data were obtained using a Tetracam Agricultural Digital Camera in 2013–2014.The gross primary production（GPP） and aboveground plant biomass（AGB） were modeled using the surface measured NDVI and climatic data during the growing seasons（i.e.June–September） in 2013–2014.Both low and high warming significantly increased air temperature by 1.54 and 4.00°C,respectively,and significantly increased vapor pressure deficit by 0.13 and 0.31 kP a,respectively,in 2013-2014.There were no significant differences of GNDVI,AGB and ANPP among the three warming treatments.The high warming significantly reduced average NDVI by 23.3%（-0.06）,while the low warming did not affect average NDVI.The low and high warming significantly decreased average SAVI by 19.0%（-0.04） and 27.4%（-0.05）,respectively,and average GPP by 24.2%（i.e.0.21 g C m^（-2） d^（-1）） and 44.0%（i.e.0.39 g C m^（–2） d^（-1））,respectively.However,the differences of the average NDVI,SAVI,and GPP between low and high warming were negligible.Our findings suggest that a greater drying may dampen the effect of a higher warming on vegetation indices and biomass production in alpine meadow on the northern Tibetan Plateau.

Response of Plant Growth and Biomass Accumulation to Short-term Experimental Warming in a Highland Barley System of the Tibet

Highland barley is an important staple food in the Tibet,and the Tibetan Plateau is experiencing obvious climatic warming.However,few studies have examined the warming effects on highland barley growth and biomass allocation under conditions of controlled experimental warming.This limits our ability to predict how highland barley will change as the climate changes in the future.An experiment of field warming at two magnitudes was performed in a highland barley system of the Tibet beginning in late May,2014.Infrared heaters were used to increase soil temperature.At the end of the warming experiment（September 14,2014）,plant growth parameters（plant height,basal diameter,shoot length and leaf number）,biomass accumulation parameters（total biomass,root biomass,stem biomass,leaf biomass and spike biomass）,and carbon and nitrogen concentration parameters（carbon concentration,nitrogen concentration,the ratio of carbon to nitrogen concentration in root,stem,leaf and spike）were sampled.The low-and high-level experimental warming significantly increased soil perimental warming did not significantly change.The low-and high-level experimental warming did not significantly affect plant growth parameters,biomass accumulation parameters,and carbon and nitrogen concentration parameters.There were also no significant differences of plant growth parameters,biomass accumulation parameters,and carbon and nitrogen concentration parameters between the low-and high-level experimental warming.Our findings suggest that the response of highland barley growth,total and component biomass accumulation,and carbon and nitrogen concentration to warming did not linearly change with warming magnitude in the Tibet.

Effect of Long-term Experimental Warming on the Nutritional Quality of Alpine Meadows in the Northern Tibet

The nutritional quality of grasslands is closely related to recruitment of young and population dynamics of livestock and wild herbivores. However, the response of nutritional quality to climate warming has not been fully understood in the alpine meadow on the Tibetan Plateau, especially in the Northern Tibet. Here, we investigated the effect of experimental warming(beginning in 2008) on nutritional quality in three alpine meadows(site A: 4313 m, B: 4513 m and C: 4693 m) in the Northern Tibet. Crude protein(CP), neutral detergent fiber(NDF), acid detergent fiber(ADF), crude ash(Ash), ether extract(EE) and water-soluble carbohydrate(WSC) were examined in 2018–2019. Experimental warming only increased the content of CP by 27.25%, ADF by 89.93% and NDF by 41.20%, but it decreased the content of Ash by 57.76% in 2019 at site B. The contents of CP and WSC both increased with soil moisture(SM). The content of CP decreased with vapor pressure deficit(VPD). The combined effect of SM and VPD was greater than air temperature(Ta) in controlling the variations of the CP content, ADF content and nutritional quality. Compared to Ta, VPD explained more of the variation in NDF and Ash content. All of these findings suggest that warming effects on nutritional quality may vary with site and year, and water availability may have a stronger effect on the nutritional quality than temperature in the alpine meadow of the Northern Tibet.

Driving Mechanism of Gross Primary Production Changes and Implications for Grassland Management on the Tibetan Plateau

The contribution of climatic change and anthropogenic activities to vegetation productivity are not fully understood.In this study,we determined potential climate-driven gross primary production(GPPp)using a process-based terrestrial ecosystem model,and actual gross primary production(GPPa)using MODIS Approach in alpine grasslands on the Tibetan Plateau from 2000 to 2015.The GPPa was influenced by both climatic change and anthropogenic activities.Gross primary production caused by anthropogenic activities(GPPh)was calculated as the difference between GPPp and GPPa.Approximately 75.63%and 24.37%of the area percentages of GPPa showed increasing and decreasing trends,respectively.Climatic change and anthropogenic activities were dominant factors responsible for approximately 42.90%and 32.72%of the increasing area percentage of GPPa,respectively.In contrast,climatic change and anthropogenic activities were responsible for approximately 16.88%and 7.49%of the decreasing area percentages of GPPa,respectively.The absolute values of the change trends of GPPp and GPPh of meadows were greater than those of steppes.The GPPp change values were greater than those of GPPh at all elevations,whereas both GPPp and GPPh showed decreasing trends when elevations were greater than or equal to 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.Climatic change had stronger effects on the GPPa changes when elevations were lower than 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.In contrast,anthropogenic activities had stronger effects on the GPPa changes when elevations were greater than or equal to 5000 m,4600 m and 4800 m in meadows,steppes and all grasslands,respectively.Therefore,the causes of actual gross primary production changes varied with elevations,regions and grassland types,and grassland classification management should be considered on the Tibetan Plateau.

Response of Plant Community Carbon and Nitrogen Stoichiometry to Experimental Warming on the Qinghai-Tibet Plateau

Low temperature is an important limiting factor for alpine ecosystems on the Tibetan Plateau. This study is based on data from on-site experimental warming platforms(open top chambers, OTC) at three elevations(4300 m, 4500 m, 4700 m) on the Qinghai-Tibet Plateau. The carbon and nitrogen stoichiometry characteristics of plant communities, both above-ground and below-ground, were observed in three alpine meadow ecosystems in August and September of 2011 and August of 2012. Experimental warming significantly increased above-ground nitrogen content by 21.4% in September 2011 at 4500 m, and reduced above-ground carbon content by 3.9% in August 2012 at 4300 m. Experimental warming significantly increased below-ground carbon content by 5.5% in August 2011 at 4500 m, and the below-ground ratio of carbon to nitrogen by 28.0% in September 2011 at 4300 m, but reduced below-ground nitrogen content by 15.7% in September 2011 at 4700 m, below-ground carbon content by 34.3% in August 2012 at 4700 m, and the below-ground ratio of carbon to nitrogen by 37.9% in August 2012 at 4700 m. Experimental warming had no significant effect on the characteristics of community carbon and nitrogen stoichiometry under other conditions. Therefore, experimental warming had inconsistent effects on the carbon and nitrogen stoichiometry of plant communities at different elevations and during different months. Soil ammonium nitrogen and nitrate nitrogen content were the main factors affecting plant community carbon and nitrogen stoichiometry.

Response of Microbial Communities in Soil to Multi-level Warming in a Highland Barley System of the Lhasa River

No studies have examined the effect of experimental warming on the microbial biomass and community composition of soil in agricultural ecosystem on the Qinghai-Tibet Plateau. Thus it is unclear whether the influences of experimental warming on microbial communities in soil are related to warming magnitude in croplands on this Plateau. This study performed warming experiment(control, low-and high-level) in a highland barley system of the Lhasa River in May 2014 to examine the correlation between the response of microbial communities in soil to warming and warming magnitude. Topsoil samples(0–10 and 10–20 cm) were collected on September 14, 2014. Experimental warming at both low and high levels significantly increased soil temperature by 1.02 ℃ and 1.59 ℃, respectively at the depth of 15 cm. Phospho lipid fatty acid(PLFA) method was used to determine the microbial community in soil. The low-level experimental warming did not significantly affect the soil’s total PLFA, fungi, bacteria, arbuscular mycorrhizal fungi(AMF), actinomycetes, gram-positive bacteria(G+), gram-negative bacteria(G–), protozoa, the ratio of fungi to bacteria(F/B ratio), and ratio of G+ to G–(G+/G– ratio) at the 0–10 and 10–20 cm depth. The low-level experimental warming also did not significantly alter the composition of microbial community in soil at the 0–10 and 10–20 cm depth. The high-level experimental warming significantly increased total PLFA by 74.4%, fungi by 78.0%, bacteria by 74.0%, AMF by 66.9%, actinomycetes by 81.4%, G+ by 67.0% and G– by 74.4% at the 0–10 cm depth rather than at 10–20 cm depth. The high-level experimental warming significantly altered microbial community composition in soil at the 0–10 cm depth rather than at 10-20 cm depth. Our findings suggest that the response of microbial communities in soil to warming varied with warming magnitudes in the highland barley system of the Lhasa River.

Estimation of Daily Vapor Pressure Deficit Using MODIS Potential Evapotranspiration on the Tibetan Plateau

Vapor pressure deficit（VPD） is an important parameter in modelling hydrologic cycles and vegetation productivity. Meteorological stations are scarce in remote areas,which often results in imprecise estimations of VPD on the Tibetan Plateau. Moderate Resolution Imaging Spectroradiometer（MODIS） provides evapotranspiration data,which may offer the possibility of scaling up VPD estimations on the Tibetan Plateau. However,no studies thus far have estimated VPD using MODIS evapotranspiration data on the Tibetan Plateau. Therefore,this study used MODIS potential evapotranspiration（PET） to estimate VPD in alpine meadows,alpine steppes,croplands,forests and shrublands for the year,spring,summer,autumn and winter in 2000-2012. A series of root-meansquared-error（RMSE） and mean-absolute-error（MAE） values were obtained for correlating measured VPD and estimated VPD using MODIS PET data for each listed time period and vegetation type： whole year（0.98-2.15 hPa and 0.68-1.44 hPa）,spring（0.95-2.34 hPa and 0.72-1.54 hPa）,summer（1.39-2.60 hPa and 0.89-1.96 hPa）,autumn（0.78-1.93 hPa and 0.56-1.36 hPa）,winter（0.48-1.40 hPa and 0.36-0.98 hPa）,alpine steppes（0.48- 1.39 hPa and 0.36-1.00 hPa）,alpine meadows（0.58-1.39 hPa and 0.44-0.90 hPa）,croplands（1.10-2.55 hPa and 0.82-1.74 hPa）,shrublands（0.98-1.90 hPa and 0.78-1.37 hPa）,and forests（1.40-2.60 hPa and 0.98-1.96 hPa）,respectively. Therefore,MODIS PET may be used to estimate VPD,and better results may be obtained if future studies incorporate vegetation types and seasons when the VPD data are estimated using MODIS PET on the Tibetan Plateau.