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.     

Effects of Simulated Diurnal Asymmetrical Warming on the Growth Characteristics and Grain Yield of Winter Highland Barley in Tibet

There has been an obvious diurnal asymmetrical warming effect as a result of the overall climate warming in the Tibetan Plateau. To reduce the uncertainty caused by the diurnal asymmetrical warming effect on future food security predictions in the Tibetan Plateau, this study used winter highland barley (var. Dongqing No. 1) for the experimental materials, and the FATI (Free Air Temperature Increase) field open heating system to carry out a simulated diurnal asymmetrical warming experiment (AW: All-day warming, DW: Daytime warming, NW: Nighttime warming, CK: Control) for two growing seasons (2018-2019 and 2019-2020) at the Lhasa Agroecosystem Research Station. The growth characteristics and yield of Tibetan winter highland barley were investigated in this study. Compared to the control, all the AW, DW and NW treatments had significant effects on the phenological period of winter highland barley, with the advancement of the phenological phase and shortening of the whole growth period. The degree of influence was AW>NW>DW, and all the AW, DW and NW treatments shortened the interval from sowing to heading of winter highland barley and increased the interval from heading to maturity. The effect on the phenological phase was the most obvious for AW and reached a statistically significant level (P<0.05). During the generative growth phase, the biomass above-ground and plant height of winter highland barley had an increasing tendency under the different warming conditions. In the late growth period, the biomass above-ground and plant height of the NW treatment were significantly higher than those of the other treatments. In addition, the warming caused a decrease in the dry matter distribution proportions of leaves and stems at the mature stage, and an increase in the distribution ratios of roots and spikes; and the AW, NW and DW treatments increased grain yields by 16.4%, 24.6% and 9.5%, respectively, on average in the two years. The increasing effect on grain yields of the NW treatment reached a significant level compared with the control in 2019-2020 (t=-2.541, P=0.026). In terms of yield composition, the effective spike number and 1000-grain weight tended to increase. The grain number per spike tended to increase, except for the AW treatment, while panicle length and seed setting rate tended to decrease, except for the NW treatment. Therefore, the effects of different simulated diurnal asymmetrical warming treatments on the growth characteristics and yield of winter highland barley were variable in the Tibetan Plateau.     

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 kPa, 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.     

呼伦贝尔草原对全球变暖的响应

近百年来,尤其近20年,全球气候显著变暖,已导致植物物候与生产力在过去20年中发生显著变化。遥感方法是研究植被对全球变暖的响应的一种非常有效的方式,利用NOAA／AVHRR数据,结合地面气象数据,研究近20年来中国东北地区呼伦贝尔草原NDVI与温度、降水变化的相互关系,认识呼伦贝尔草原对气候变化的响应特征。研究结果表明：(1)呼伦贝尔草原地区近20年温度变化明显,高于全球平均增温幅度。(2)生长季(4～10月)NDVI有较明显上升,线性拟合分析表明,所选4个区域近20年生长季NDVI平均值上升了2．2％。(3)NDVI的增加主要在1988年前后,在草原东部后一阶段(1988～1999)比前一阶段(1982～1987)NDVI平均值增加了7．8％。(4)呼伦贝尔草原对全球变暖响应显著。NDVI与气温,尤其与春季相关性显著。     

西藏纳木错植物物候及其对气候的响应

利用纳木错流域1O种代表性植物2007年和2008年的物候观测资料,分析了植物生殖物候的基本特征及气候条件对其的影响.植物最早5月中旬进入开花期,大部分植物的盛花期在6月中旬至7月下旬,开花的最适温度范围为8.5-8.9℃,花期延续到9月下旬.从6月上旬开始,大部分植物进入果期,多数植物果期与花期重叠.纳木错具有高寒地带植物物候的普遍特征:生长期较短(5个月左右)、早花现象、晚花现象.同2007年相比,2008年雨季提前,虽然气温偏低,大部分植物花期和果期普遍缩短5 d左右,但物候期提前约20 d.植物物候的年际变化对气候变化,特别是对降水量的季节分配更敏感.     

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.     

气候变暖对甘肃种植业结构和农作物生长的影响

采用对农作物生长有指标意义的≥10℃积温和<0℃负积温与农作物适宜种植面积、生长发育速度及产量进行对比统计分析研究,得出气候变暖对农作物种植结构发生了较大改变,冬小麦西伸北扩,棉花面积迅速扩大,多熟制向北和高海拔地区推移。农作物生长发育速度发生了明显变化,春播作物提早播种,喜热和喜温作物生育期延长,越冬作物推迟播种,生育期缩短。喜热作物棉花气候产量明显增加。     

青藏高原东北部与南部地区树木径向生长对气候要素的响应——以祁丰和林周树轮为例

了解树木径向生长对气候响应的区域特征是模拟或预测未来全球变化如何对森林生态系统产生影响的基础。对青藏高原东北部(祁丰)干旱气候条件下与南部(林周)高寒半干旱气候条件下的两条标准化年表分析发现,两年表敏感度均较高,样芯间一致性均较强,为分析树木径向生长对气候要素的响应关系提供了保障。对祁丰和林周树轮宽度序列与其附近酒泉(1951-2009年)和当雄(1963-2009年)气象站上年5月到当年9月的气候因子(月平均气温、月最高气温、月平均最低温和月降水量)进行相关和响应分析发现,祁丰和林周树木的径向生长与当年5-6月平均气温存在负相关关系,相关系数分别为-0.360和-0.466;而与当年5-6月降水量显著正相关,相关系数分别为0.499和0.623。祁丰和林周树轮宽度序列与帕尔默干旱指数(PDSI,1951-2005年)的格网数据在每个月份均呈正相关关系,与5-6月的相关值分别为0.581和0.719。上年7月到当年6月的降水量与祁丰(r=0.529)和林周(r=0.667)树轮宽度序列的相关值也较高,推断干旱状况是限制高原东北部与南部树木径向生长的主要因素。     

我国北方沙区气候变化对全球变暖的响应

我国北方沙区,由于东西跨度很大,各沙区之间气温、降水及湿润度存在着较大差异。西部的沙区气温较高、降水较少、气候干燥;东部的沙区气温较低、降水较多、气候相对湿润。春季各沙区都比较干燥。各沙区气温变化基本是同步的,而降水变化有差异。各沙区夏半年气温与降水之间基本为负相关;冬春季节,河套沙区和东部沙区有明显的正相关时段。在全球变暖的背景下,我国北方沙区的气温总体也在升高(沙区气温每10a上升约03℃,且升温幅度比全国、全球更明显,而降水变化却相对较小。各个沙区对全球变化的响应不尽相同。东部沙区气温升高、降水减少、湿润度下降幅度最大,暖干化趋势最明显;塔里木沙区气温变化平稳、降水及湿润度略增;其他沙区气温略升、降水略减、湿润度略降,呈弱的暖干化趋势。与气候变化相对应,我国北方沙区沙漠化土地面积增大,而且沙漠化主要发生在东部沙区。预计21世纪初10a我国北方沙区的气候将进一步暖干化,因而土地沙漠化的自然过程也将进一步加快和加剧。     

青藏高原中东部植被覆盖对水热条件的响应研究

植被覆盖的变化常是自然因子和人类活动的综合作用,分析植被对水热条件的响应关系有助于认识人类活动在地表植被变化中的作用程度。本文旨在结合1982~2000年地面气象观测资料和NOAA卫星的AVHRR 植被指数（8km）,对气象站点分布相对密集的青藏高原中东部的NDVI（归一化植被指数）空间变化同水热条件的响应关系进行分析。通过水热有关指标的趋势面模拟、植被类型比较和样带分析,表明：在青藏高原中东部地区,水热条件组合较好（如常绿针叶林）或较差（如荒漠半荒漠）的区域,多年平均的NDVI旬值同水热条件的相关性不强;而范围广阔的水热条件组合中等区域（如高山草甸/草原）同水热条件相关性很高;青藏高原周边区域植被对水热条件相对不敏感,而高原主体部分植被覆盖同水热的相关性则很高（0.75以上）;此外,海拔对热量条件影响很大,进而影响植被覆盖。     

1974—2009年西藏羊卓雍错湖泊水位变化分析

羊卓雍错(简称羊湖)是青藏高原南部最大的一个封闭型内陆湖泊,位于西藏自治区浪卡子县境内,与纳木错、玛旁雍错一起并列为西藏三大圣湖,是藏南地区重要的风景旅游区。始建于1989年的羊湖发电站于1997年正式投入运营,为世界上海拔最高的抽水蓄能电站。在全球气候变暖和人类活动的影响下,其湖面水位变化及其成因备受国内外关注。利用1974—2009年羊湖白地水文观测资料,分析了36年来羊湖水位年际、年内变化特征及其与自然要素(气温、降水和蒸发等)和人类活动之间的关系。结果表明,羊湖平均水位为19.06 m,历史最高值出现在1980年,为21.37 m,2009年水位降至17.08 m的历史最低值。自1974年有水位观测资料以来,羊湖水位呈波动式下降趋势,其中,1974—1977年水位表现为逐年下降,幅度为0.26 m/a;之后至1980年以0.4 m/a呈上升态势,1980年羊湖水位达到了历史最高值;此后,至1996年水位呈显著下降趋势,减少速率为2.08 m/(10 a),1996年是羊湖水位上升的一个转折点,至2004年水位在逐年上升;2004—2009年是一个水位显著下降的时段,速率为0.57 m/a,也是水位下降趋势最为显著的时段。羊湖水位下降年份占整个时段的56%,而44%的年份水位在上升。1974—1984年及2001—2005年水位高于多年平均值,而1985—2000年及2006年之后水位都低于多年平均值。羊湖水位的年内最低值一般出现在6月,最高值则在10月。羊湖年内水位变化对流域降水量的响应具有一定的滞后性,时间为2个月左右。羊湖水位变化主要是由降水波动、气温上升、蒸发的变化等自然因素共同作用的结果,特别是,流域年际降水量波动是湖面水位升降的主要影响因子,人为和工程的影响范围和程度均较小。自羊湖电站1997年运行以来,流域的环境在暖湿的气候大背景下有所改善,且对羊湖水位变化无明显影响。但如果电站不能蓄水与发电并举,达不到总体不消耗羊湖水量的设计目标和水量平衡,对羊湖水位的影响将不可忽视。     

近44年来中国西北降水量变化的区域差异以及对全球变暖的响应

利用中国西北地区(75~105°E、35~50°N)最近44年(1958~2001年)77个气象台站观测的降水量、气温资料以及NCAR/NCEP再分析资料,采用回归分析与合成分析等方法研究了西北干旱区降水量的时空变化特征及其与全球气温变化的关系。结果表明,西北干旱区的降水量偏多(偏少)与全球平均气温升高(降低)存在一定的对应关系,但降水量随气温的变化存在地域差异,主要表现为干旱区的西部(93°E以西)区域年降水量随全球气温升高呈现增加趋势,而东部(93°E以东)区域年降水量呈减少趋势。     

黄河流域坡高地系统最小生态需水研究

以保护和恢复流域坡高地生态系统为目的，对坡高地最小生态需水问题进行研究，提出了坡高地生态需水和生态缺水的计算方法。以黄河流域为实例，在GIS和遥感技术支持下对坡高地最小生态需水量和缺水量进行了计算，并从时空两个尺度揭示了黄河流域坡高地生态系统最小生态需水的变化规律，研究成果可为流域生态环境建设和水资源合理配置提供依据。     

近40 a天山北坡气候与生态环境对全球变暖的响应

新疆天山北坡气候变化与生态环境的历史演变过程及未来可能变化趋势是天山北坡经济带可持续发展必须面对的问题,也是正确制定西部大开发战略方针的重要科学基础。通过利用天山北坡18个气象台站在近40a的气温、降水逐年月资料,采用相关分析及线性趋势分析等统计方法,分析了在全球变暖的大背景下,天山北坡生态环境演变特征及其与气候的关系,指出了未来的气候与生态环境变化对天山北坡地区的社会经济发展将产生重要影响。研究表明：天山北坡目前的生态环境正转向好的态势,天山北坡山区和平原普遍存在升温的变化趋势,尤其是平原绿洲升温比较明显。天山北坡在升温的同时,其降水量也呈现上升的趋势。     

Interdecadal change of snow depth in winter over the Tibetan Plateau and its effect on summer precipitation in China

This paper obtained a set of consecutive and long-recorded observational snow depth data from 51 observation stations by choosing, removing and interpolating original observation data over the Tibetan Plateau for 1961–2006. We used monthly precipitation and temperature data from 160 stations in China for 1951–2006, which was collected by the National Climate Center. Through calculating and analyzing the correlation coefficient, significance test, polynomial trend fitting, composite analysis and abrupt change test, this paper studied the interdecadal change of winter snow over the Tibetan Plateau and its relationship to summer precipitation and temperature in China, and to tropospheric atmospheric temperature. This paper also studied general circulation and East Asian summer monsoon under the background of global warming.     

Influence of the regional climate variations on lake changes of Zabuye,Dangqiong Co and Bankog Co salt lakes in Tibet

Journal of Geographical Sciences - The lake hydrological and meteorological data of the Tibetan Plateau are not rich. This research reports the observed climatic data and measured water levels of...     

准噶尔荒漠小山蒜的形态与生物量特征及其相互关系

小山蒜(Allium pallasii)是中国新疆特有的类短命植物。调查了准噶尔荒漠16个20 m×20 m样地内小山蒜种群的分布概况,研究了小山蒜盛花期的生物学特征、器官生物量分配及其相互关系。结果表明:①小山蒜多生于沙丘中下部,密度为0.187株·m–2;平均株高为(22.93±5.15)cm,多为3片叶;花序近球形,平均半径(2.44±0.37)cm,纵断面角度211.39°±60.4°,表面积和体积分别为(50.95±34.19)cm2和(43.37±29.45)cm3。②其形态指标(平均叶长、4个花球指标及鳞茎直径)间、生物量指标(根生物量除外)间,及二者之间多为显著(P<0.05)或极显著(P<0.01)正相关,协同生长关系较强。③小山蒜生物量分配呈鳞茎>花葶>花球>叶片>根的格局,根冠比为0.873,生殖分配占49.66%。④形态指标与生物量间均呈α<1的异速生长关系,而生物量指标间多为等速关系,其中地上、地下生物量间符合α=3/4的异速关系。⑤生物量估测表明,小山蒜单株地上生物量平均为0.312 g,单株地下生物量平均为0.264 g,种群总生物量密度仅为0.106 g·m-2,其生物量在整个荒漠生态系统中可忽略不计,但它作为准噶尔荒漠重要而独特的种质资源,应从多个方面深入研究,同时进行适当保护。     

1960-2017年渭河流域极端气温变化及其对区域增暖的响应

基于逐日最高和最低气温,计算1960-2017年渭河流域16项极端气温指数,发现近58 a渭河流域极端冷指数(冰冻日数、霜冻日数、冷夜日数、冷昼日数和冷持续指数)呈下降趋势,极端暖指数(夏日日数、热夜日数、暖昼日数、暖夜日数、作物生长期和热持续指数)呈上升趋势,特别是20世纪80年代后上升速率明显加快。流域半干旱区对气候变暖的响应更敏感,主要体现在白天温度增高以及冰冻和霜冻日数减少,而半湿润区主要为夜间增暖。相比1960-2003年,2004-2017年流域平均温度升高1.75℃,暖夜/暖昼日数增加10.99/6.79 d,而霜冻/冷夜日数减少8.71/2.35 d。分析发现地形条件是影响流域极端气温空间差异的重要因素。在流域半干旱区,冷夜和冷昼日数的快速减少,有利于农作物的生长。而在相对湿度较大的半湿润区,随着夏季连续高温天气增多,高温热浪事件的危害更大。     

青藏高原植被覆盖对水热条件年内变化的响应及其空间特征

利用1982-2000年NOAA/AVHRR卫星的NDVI数据(时间分辨率旬,空间分辨率8 km×8 km),结合同时期的气温和降水资料,基于时滞互相关方法和GIS工具,分析了青藏高原植被覆盖对水、热条件年内变化的时滞响应及其空间特征。结果如下:①除高寒荒漠、森林外,青藏高原植被NDVI与同期旬均温和旬降水相关性均呈高度正相关。其中,中等覆盖度的植被受水、热影响表现更为强烈。②青藏高原植被NDVI对气温和降水有滞后效应,且滞后水平存在空间差异,高原北部(柴达木盆地、昆仑山北冀)和高原南部植被对降水、和温度的响应比较迟缓,而高原中、东部地区植被对温度和降水的响应比较敏感。③不同植被类型对水热条件的响应程度也存在差异,由高到低依次是草甸、草原、灌丛、高寒垫状植被、荒漠,最后是森林。