内蒙古山杏种群表型变异

为明确内蒙古山杏(Armeniaca sibirica)种群间和种群内的表型变异程度和变异规律, 以内蒙古山杏自然分布区的13个种群的23个表型性状为研究对象, 采用巢式方差分析、多重比较、变异分析、相关性分析和主成分分析等多种分析方法, 对种群间和种群内的表型多样性及其与地理生态因子的相关性进行了讨论。研究结果表明: 内蒙古山杏的表型性状在种群间和种群内均存在丰富的变异, 种群间的变异大于种群内的变异, 表型性状的平均分化系数为73.03%, 种群间变异是山杏表型变异的主要变异来源。各性状的平均变异系数为14.28%, 变异幅度为7.01%-27.23%, 其中核的变异系数最大, 果的变异系数最小。土默特左旗万家沟种群表型多样性最丰富, 科尔沁右翼前旗察尔森种群表型多样性最小。表型性状主要受经度、年降水量以及年日照时间3个主要地理生态因子影响。通过主成分分析可以把13个种源区划为四大类, 其中乌拉山种群的叶性状和阿鲁科尔沁旗种群的核性状受地理生态因子影响最大。     

东北杏种质资源多样性及其地理变化

东北杏(Armeniaca mandshurica)是集观赏、经济、用材于一体的重要树种, 长期以来主要处于野生和半野生状态, 鲜有相关研究报道。该研究对东北杏主要分布区内种质资源状况开展了调查, 选择来自辽宁、吉林与黑龙江的47份典型种质进行了22个定量描述性状和7个定性描述性状的观测, 旨在为该树种的种质资源收集、评价与保护提供重要参考。采用变异系数等指标分析定量描述性状多样性, 使用频率分布等指标分析定性描述性状多样性。通过趋势面方法分析定量描述性状的地理变化规律。利用99对SSR引物对47份东北杏种质进行PCR扩增, 应用遗传相似系数分析东北杏种质的遗传多样性。基于表型性状和SSR分子标记采用聚类分析方法分别对种质进行分类。东北杏不同种质间呈现出较高的表型多样性, 其中19个定量描述性状指标的变异系数在9.40%-55.98%之间, 变异系数最大的为小枝长度, 变异系数最小的为种仁宽; 7个定性描述性状的Shannon-Wiener指数在0.58-1.22之间。由于调查区域的地理位置与主要气候因子间存在着显著的相关性, 东北杏种质的定量描述性状与其地理位置有着密切的关系。其中, 小枝长度呈由东向西逐渐增大的梯度变化, 小枝粗度、种子质量呈由北向南逐渐增大的梯度变化, 果柄长呈由东北向西南逐渐增大的梯度变化; 小枝长度、果柄长与海拔呈正相关关系, 小枝粗度与海拔呈负相关关系, 种子质量与海拔相关性很小。基于26个表型性状进行系统聚类, 将47份东北杏种质分为4类, 分类结果主要体现了东北杏种质特征的差别, 同时也在一定程度上体现了种质产地的效应; 基于遗传相似系数进行聚类分析, 将47份东北杏种质也分为4类, 分类结果体现了种质产地效应; 卡方检验表明, 两种聚类结果相关性不显著, 外在环境是影响东北杏表型变异的重要因素。     

Effects of competition and climate on tree radial growth of Pinus sibirica in Altai Mountains,Xinjiang, China

阿尔泰山的北方森林是中亚以及全球的生态系统的重要组成部分, 其生长动态可以影响到全球范围的热辐射、碳平衡等。因此, 探究影响阿尔泰山树木径向生长的主要因素至关重要。该研究以新疆喀纳斯国家级自然保护区的西伯利亚五针松(Pinus sibirica)为研究对象, 建立西伯利亚五针松年表, 通过分析不同时间间隔累年生长量、竞争指数以及气候因子之间的关系, 运用线性混合效应模型、相关分析等方法, 探究竞争和气候对新疆阿尔泰山西伯利亚五针松树木径向生长的影响。结果表明: (1)线性混合效应模型结果显示竞争树胸径和与西伯利亚五针松过去30年的累年生长量之间的拟合效果最好; (2)标准年表与3月的平均气温、平均最高气温、平均最低气温之间有显著正相关关系; (3)累年生长量最高值出现在气温0-5 ℃, 竞争指数低于100的时候。累年生长量最低时, 气温达到-10 ℃, 竞争指数也超过了300。目标树的树木径向生长受到竞争树胸径和及生长季前期气温的影响, 两者共同作用。但相较于气候因子而言, 竞争对西伯利亚五针松的树木径向生长有更大的影响作用。     

Phenotypic variations in cones and seeds of natural Pinus kesiya var. langbianensis populations in Yunnan Province,China

以云南省思茅松(Pinus kesiya var. langbianensis)天然分布区的11个种群的16个种实性状为研究对象, 采用巢式方差分析、变异系数、相关分析和非加权配对算术平均法(UPGMA)等多种分析方法, 探讨思茅松种群间和种群内的表型变异。结果表明: 思茅松种实表型性状在种群间和种群内均存在着较丰富的差异, 种群内的变异(54.76%)大于种群间的变异(10.44%), 种群间平均分化系数为11.95%, 分化程度相对较小。球果总种子数的平均变异系数最高(35.51%), 其次是球果质量(35.1%), 种子大小的平均变异系数最小(8.86%), 成为最稳定的种实性状; 景谷县的表型多样性最丰富, 景洪市则最小。球果和种子大部分表型性状之间存在显著或极显著相关, 其中球果长和球果质量越大, 种鳞长、种子长、种翅长、千粒重、球果总种鳞数和球果总种子数就越大。生态因子中, 年平均气温对表型性状影响最大, 其次是1月平均气温和>5 ℃积温。利用种群间聚类分析可以把思茅松的11个种群分为2类4个亚类, 表型性状依据地理距离进行聚类, 聚类结果与年降水量和>5 ℃积温相关性显著。     

阿尔泰山西伯利亚落叶松径向生长对气候变化的分异响应

在全球气候变暖的背景下, 北半球中高纬度地区出现了树轮径向生长对气候变化的分异响应现象, 但是阿尔泰山优势针叶树种对气候因子响应的稳定性还存在不确定性。该研究选择阿尔泰山中段高海拔西伯利亚落叶松(Larix sibirica)样本建立了树轮宽度年表, 并对年表特征及树木径向生长-气候的动态关系进行了分析。结果表明: 生长季初期和中期的气温是研究区树木生长的主控气候因子; 树木径向生长与当年4月的气温显著负相关, 与当年6-7月的气温显著正相关; 研究区西伯利亚落叶松径向生长与当年4月和6-7月的气温发生了分异现象, 表现为随着气候变化, 树木径向生长对生长季初期由高温引起的干旱的响应敏感性越来越强, 而对生长季中期气温的敏感性表现出先减弱再增强的趋势。阿尔泰山西伯利亚落叶松径向生长对气候变化的响应比较敏感, 适合开展树木生长-气候变化的研究; 检验树木径向生长对气候变化分异响应为该区域基于树木年轮开展历史气候重建和提高未来森林生态系统发展趋势预测的准确性提供了科学依据。     

Phenotypic variations in natural populations of Amygdalus pedunculata

Aims Our objectives were to determine the phenotypic variations, adaption and distribution patterns in seven natural Amygdalus pedunculata populations.Methods We analyzed 14 phenotypic traits from 120 individuals in seven populations of A. pedunculata by variance analysis, correlation analysis, and cluster analysis.Important findings Results showed that there were plentiful phenotypic variation within and among populations. In particular, the phenotypic variation within population was 40.91%, higher than that among populations (35.29%), which indicated that the phenotypic variation within population was the main source of the phenotypic variation in A. pedunculata. Mean differentiation coefficient was 45.90%, and mean coefficient of variation of 14 traits was 15.59%, ranged from 9.39% to 31.98%. Mean annual temperature, latitude, length of frost-free period, longitude and altitude appear to be prominent ecological factors influencing phenotypic traits. Mean annual temperature and length of frost-free period were key indicators to phenotypic of A. pedunculata in different site conditions. According to principal component analysis and unweighted pair-group method with arithmetic means (UPGMA) cluster analysis, the seven populations of A. pedunculata could be divided into two groups. In mountainous region, A. pedunculata’s leaf blade was usually rotund to oblong, fruit nearly spherical shape with shorter fruit stem, stone was usually ovoid to spherical shape. In contrast, in sandy region, leaf blade was long oval to ovate-lanceolate, fruit and stone was usually flat ovoid with longer fruit stem. Our results provide critical information for the resource collection and breeding of this ecologically important species.     

Leaf phenotypic variation in natural populations of Cerasus dielsiana

为揭示中国特有植物尾叶樱桃(Cerasus dielsiana)在现代核心分布区天然种群的叶表型地理变异规律及其生态适应性特征, 该研究通过多重比较、巢氏方差分析、相关性分析、主成分分析(PCA)、主坐标分析(PCoA)、非加权配对算术平均法(UPGMA)聚类分析等数理方法, 对来自四川、湖北、湖南、江西、台湾5省8个尾叶樱桃天然种群的11个叶表型性状进行了比较分析, 研究其不同地理单元间叶表型多样性和地理变异规律及对地理气候的响应。结果显示: 1)尾叶樱桃主要叶表型性状变异在种群内和种群间均存在显著差异, 平均变异系数为22.44%, 其中变异系数最大和最小的分别为叶面积(50.83%)与一级侧脉数(7.96%); 平均叶表型性状的分化系数为30.78%, 种群内的变异(51.55%)大于种群间的变异(22.55%)。2) PCA表明对尾叶樱桃叶表型性状变异起主要贡献作用的前三大主成分累计贡献率达到92.400%, 可以综合概括和排序为“大小性状” (73.242%)与“形状性状” (19.158%)。3)叶宽(r = -0.641)、叶面积(r = -0.658)和一级侧脉数(r = 0.659)性状均与经度呈显著负相关或正相关关系, 气温季节变化和最湿季降水量对叶表型性状变异影响较大。4)基于PCoA和UPGMA聚类分析可将8个天然种群划分为4类。尾叶樱桃天然种群叶表型性状变异丰富, 在数量上表现出一定的连续性, “大小性状”是性状间变异的主要来源, 平均表型分化处于中等程度水平, 种群内是叶表型性状变异的主要来源; 各种群间表型分化划分结果与地理位置基本一致, 在地理空间上呈现以经度为主的梯度变异模式, “气候变异性”与“展叶期降水量”是驱动叶表型性状变异的主要气候因子, 推测这是尾叶樱桃在长期进化中与亚热带季风气候环境相适应的结果。     

内蒙古西鄂尔多斯地区半日花荒漠群落特征及其分类

半日花(Helianthemum songaricum)为亚洲中部特有种和古地中海残遗植物, 其群落为内蒙古西鄂尔多斯地区的特有荒漠植物群落。该文以2016-2017年野外调查数据为基础, 结合相关文献资料, 对半日花荒漠群落的分布、群落特征及其分类进行了总结。结果表明: (1)半日花荒漠群落集中分布于黄河以东内蒙古西鄂尔多斯的阿尔巴斯山麓南北部、千里沟; 少量分布于黄河以西贺兰山北端内蒙古乌海市与阿拉善盟交界处及贺兰山最南端的内蒙古阿拉善盟与宁夏交界处明长城沿线的石质残丘。(2)根据样地调查, 半日花荒漠群落记录到种子植物58种, 隶属于17科39属, 其中灌木、半灌木18种, 多年生草本27种, 一年生草本植物13种; 水分生态类型中强旱生植物(15种)和旱生植物(29种)占绝对优势; 区系地理成分以中亚东部成分为主, 其次为古地中海成分和戈壁成分。(3)根据生活型和优势度, 半日花荒漠群落可分为半日花-草本荒漠群丛组、半日花-灌木-草本荒漠群丛组和半日花-半灌木荒漠群丛组, 进一步分为10个群丛。     

Defense strategies of dominant plants under different grazing intensity in the typical temperate steppe of Nei Mongol,China

放牧是草原的主要利用方式, 但对牧草造成了一定的生物胁迫。面对生存压力, 牧草会通过调节初级与次级代谢过程启动防御机制。该研究以内蒙古温带典型草原优势种植物为研究对象, 通过测定其在5个放牧水平下不同营养器官中的次级代谢产物及木质素等含量, 探讨大针茅(Stipa grandis)和羊草(Leymus chinensis)的各营养器官在防御机制中的角色及其碳氮权衡策略。结果表明: 面对放牧胁迫, 大针茅和羊草会产生大量的单宁、总黄酮、酚类以及生物碱等次级代谢产物, 并以叶片为主要的合成及储存器官。中度放牧使羊草的化学防御机制得到较充分的诱导及表达。但二者地上部分木质素含量并无显著增加, 因此, 二者在避牧性机制上更倾向于化学防御而非机械防御。由于羊草有更高的氮利用效率, 这使得羊草可以通过碳氮两种代谢途径进行防御, 但大针茅在生长初期并不能将氮高效地分配到化学防御中。大针茅和羊草在生长初期面对轻度放牧胁迫, 较多的资源仍然用于初级代谢, 增加了植物耐牧性。因此, 轻度放牧有利于提高牧草的碳氮资源利用效率、提高生态系统生产力及稳定性。     

浙江楠种群表型变异

以探讨浙江楠(Phoebe chekiangensis)种群间和种群内的表型变异程度和变异规律为目的, 对其分布区9个种群的10个表型性状进行了研究。采用巢式方差分析、变异系数、多重比较和相关分析等多种分析方法, 对种群间和种群内的表型多样性及其与地理生态因子的相关性进行了讨论。研究结果表明: 浙江楠叶片、种子等表型性状在种群间和种群内均存在着丰富的变异, 10个性状在种群间、种群内的差异均达极显著水平; 种群内的变异(21.74%)大于种群间的变异(18.45%), 表型性状的平均分化系数为41.43%, 种群内变异是浙江楠表型变异的主要变异来源。各性状平均变异系数为12.78%, 变化幅度为6.50%-19.38%。种群间叶片的平均变异系数(16.99%)高于种群间种子的平均变异系数(8.58%), 表明种子的稳定性高于叶片。叶宽、叶面积与叶片其他性状间多呈显著或极显著相关, 种子千粒重与种子宽、种子体积显著正相关; 而种子和叶片的各性状间多无显著相关性。种子宽、种子体积和种子千粒重随着海拔的增加出现减小的趋势, 种子体积受纬度控制, 随着纬度的增大表现出增大的趋势。     

内蒙古西伯利亚杏种质资源表型多样性研究

为了明确内蒙古西伯利亚杏(Armeniaca sibirica(L.)Lam.)种质资源表型性状的变异特点和多样性,对来自14个种源的143份西伯利亚杏种质资源的37个表型性状进行聚类、相关性、主成分等分析。结果表明,内蒙古西伯利亚杏表型性状的变异系数均值为20.38%,单果重的变异系数(56.69%)最大,果形指数的变异系数(7.99%)最小,数量性状的Shannonweaver多样性信息指数(2.648)大于质量性状(0.265);各部位数量性状变异系数大小顺序为叶果核仁,多样性信息指数大小顺序为叶核仁果。基于37个表型性状数据,将种质资源分为4个类群:第Ⅰ类群核仁大且饱满,适用于选育大仁品种;第Ⅱ类群核壳薄,出仁率高,丰产潜力大;第Ⅲ类群核壳厚,适用于选育核壳用品种;第Ⅳ类群果实、果核、核仁均大但核仁不饱满,适用于改良并选育仁用杏品种。数量性状的前6个主成分累计方差贡献率达到87.20%,反映的信息与聚类分析和相关分析结果基本一致。核干重、仁干重、出核率、出仁率等经济性状受果核性状指标的影响较大,结合相关性分析和主成分分析,23个数量性状可简化为单果重、核干重、仁干重、核侧径、核壳厚、仁横径、果形指数、核形指数、仁形指数等9个主要性状。以上结果为西伯利亚杏的资源评价和品种选育提供了重要的物质基础和理论依据。     

Effects of nitrogen addition on photosynthetic characteristics of Leymus chinensis in the temperate grassland of Nei Mongol,China

Aims The increased atmospheric nitrogen (N) deposition due to human activity and climate change greatly causes grassland ecosystems shifting from being naturally N-limited to N-eutrophic or N-saturated, and further affecting the growth of grass species. The aims of this study are: 1) to evaluate the effects of different N addition levels on morphology and photosynthetic characteristics of Leymus chinensis; 2) to determine the critical N level to facilitate L. chinensis growth.
Methods We conducted a different N addition levels experiment in dominant species in the temperate steppe of Nei Mongol. The aboveground biomass, morphological and leaf physiological traits, pigment contents, chlorophyll a fluorescence parameters and biochemical parameters of L. chinensis were investigated.
Important findings Our results showed that aboveground biomass first increased and then decreased with the increased N, having the highest values at the 10 g N·m^-2·a^?1 treatment, but the 25 g N·m^-2·a^?1 still significantly increased the aboveground biomass relative to 0 g N·m^-2·a^?1. Leymus chinensis accommodate low N situation through allocating less N to carboxylation system and decreasing leaf mass per area (LMA) in order to get more light energy. Moderate N addition captured more light energy through increasing total chlorophyll (Chl) contents and decreasing the ratio of Chl a/b. Moderate N addition increased LMA, carboxylation efficiency, maximum carboxylation rate (V_cmax), maximum electron transport rate (J_max) and decreased J_max/V_cmax, thus allocating more N to carboxylation system to enhance carboxylation capability. Moreover, the photochemical activity of PSII was increased through higher effective quantum yield of PSII photochemistry, electron transport rate and photochemical quenching coefficient. Excessive N addition had negative effects on physiological variables of L. chinensis due to lower carboxylation capability and photochemical activity of PSII, further leading to decreased net photosynthetic rate, whereas increased non-photochemical quenching coefficient and carotenoids played the role in the dissipation of excess excitation energy. Overall, moderate N addition facilitated the photosynthetic characteristics of dominant species, but excessive N addition inhibited photosynthetic characteristics. The most appropriate N addition for the growth of L. chinensis was 5-10 g N·m^-2·a^?1 in the temperate steppe of Nei Mongol, China.     

Phenotypic variations in seed and fruit traits of Liquidambar formosana populations

为了明确我国枫香树(Liquidambar formosana)种子与果实表型变异程度和变异规律, 采用方差分析、相关分析和回归分析等方法对36个天然种群枫香树的10个种子与果实的表型性状在种群间和种群内表型变异和地理变异模式进行探讨。研究结果表明, 枫香树平均表型分化系数为57.55%, 种群间的变异是其表型变异的主要来源; 种子和果实表型性状的变异丰富, 变异幅度为10.05%-24.31%, 平均变异系数为15.83%; 不同种群间变异差别明显, 安福种群平均变异系数最大(16.73%), 建阳种群平均变异系数最小(11.48%)。枫香树多数种子与果实表型性状在地理变化上是随机的, 地理相近种群在表型上没有显著相关性。地理气候因子中1月平均气温、海拔和纬度对种子与果实性状起主要的影响。种子与果实性状与海拔相关分析表明, 枫香树种子长宽比随海拔的升高而减小, 种子长宽比可以推测种群所在的海拔高度。探讨枫香树种群表型多样性, 可为野生优异种质的收集、多目标品种选育等工作提供依据。     

Relationships between soil nutrients and plant functional traits in different degradation stages of Leymus chinensis steppe in Nei Mongol,China

Aims Understanding ecological implications of plant functional traits is helpful in exploring community assembly under different environments of nature and human disturbances, and then to reveal the maintenance mechanism of the ecosystem services. By analyzing vegetation and soil data derived from field observations in Leymus chinensis steppe of Xilin River Basin in Nei Mongol, we aimed to explore the responses of plant functional traits to changing soil nutrients at different degradation stages. Methods We observed 69 plots for both plant community structure and soil attributes using quadrat and soil-drilling methods. Five plant functional traits, namely the specific leaf area (SLA), leaf dry matter content (LDMC), leaf carbon to nitrogen ratio (C:N), leaf lignin content (LLC), and maximum height (MH), were measured for each plot. We also tested soil attributes, such as total nitrogen (TN), total phosphorus (TP), available nitrogen (AN), available phosphorus (AP), and organic carbon (OC). The sixty-nine communities were classified into four groups (undegraded L. chinensis + forbs, slightly degraded L. chinensis + Stipa sp., moderately degraded L. chinensis + Cleistogenes squarrosa, and heavily degraded L. chinensis + Artemisia frigida) using TWINSPAN software. The relationships between plant functional traits and soil nutrient variables were analyzed for the four community groups using the Pearson’s correlation test with SPSS 21.0 software. Important findings (1) The soil nutrients decreased with the grassland degradation process and there were significant differences in TN and TP between the undegraded L. chinensis + forbs and heavily degraded L. chinensis + A. frigida communities; (2) plant functional traits also showed strong differences between the degradation stages. MH and C:N decreased with degradation. A significant difference was observed in MH between the undegraded L. chinensis + forbs and slightly degraded L. chinensis + Stipa sp. communities. The difference in C:N was also significant between the undegraded L. chinensis + forbs and heavily degraded L. chinensis + A. frigida communities; (3) the effects of soil nutrients on plant functional traits changed with grassland degradation. AN was negatively correlated with MH, LLC, and C:N in the slightly degraded L. chinensis + Stipa sp. community. In the moderately degraded L. chinensis + C. squarrosa community, those three traits mentioned above showed significantly positive correlations with TP; (4) while analyzing the degraded grassland, different relationships between plant functional traits were found. In the slightly degraded L. chinensis + Stipa sp. community, LLC was positively correlated with all other traits. Moreover, positive correlations also occurred between C:N and MH, C:N and LDMC, and C:N and LLC. In the heavily degraded L. chinensis + A. frigida community, all traits demonstrated the most significantly positive correlations.     

Population structure and spatial pattern of Caragana tibetica communities in Nei Mongol shrub-encroached grassland

Aims The community structure and function of the shrub-encroached grassland, as well as its formation mechanism, is one of hot scientific problems in vegetation science. The spatial pattern analysis is an important means for studying plant population interactions and the relationships between plant population and environment. The shrub-encroached grassland is one major vegetation type in Nei Mongol. Knowledge on the spatial pattern of shrub can improve our understanding on adaptive characteristics of shrub to steppe environment.
Methods We chose Caragana tibetica encroached grassland distributed in Ordos City as research objects. The spatial position of each C. tibetica individual in 64 m × 64 m study plot was determined by a method of “three-distance location method”, and then the spatial pattern and intraspecific associations of C. tibetica individuals was analyzed with the point pattern analysis.
Important findings The results showed that C. tibetica population was at the rising stage. The mature individuals showed a uniform distribution at the scale of less than 3.7 m, subsequently exhibiting a random distribution with an increased scale. The juvenile individuals showed an aggregation distribution at the scale of 0.3-20.4 m, but a uniform distribution at other scales. The dead C. tibetica individuals were distributed aggregately at the scale from 0.7 to 1.4 m, but randomly at other scales. An indistinctive positive association was found for live C. tibetica individuals to dead individuals at the scale of less than 9.9 m, but no associations was found between them at other scales. The mature individuals negatively interacted with juveniles at the scale of larger than 2.2 m, but unassociated at the other scales.     

Carbon storage of the forests and its spatial pattern in Nei Mongol,China

Aims
Forest carbon storage in Nei Mongol plays a significant role in national terrestrial carbon budget due to its large area in China. Our objectives were to estimate the carbon storage in the forest ecosystems in Nei Mongol and to quantify its spatial pattern.
Methods
Field survey and sampling were conducted at 137 sites that distributed evenly across the forest types in the study region. At each site, the ecosystem carbon density was estimated thorough sampling and measuring different pools of soil (0-100 cm) and vegetation, including biomass of tree, grass, shrub, and litter. Regional carbon storage was calculated with the estimated carbon density for each forest type.
Important findings
Carbon storage of vegetation layer in forests in Nei Mongol was 787.8 Tg C, with the biomass of tree, litter, herbaceous and shrub accounting for 93.5%, 3.0%, 2.7% and 0.8%, respectively. Carbon density of vegetation layer was 40.4 t·hm^-2, with 35.6 t·hm^-2 in trees, 2.9 t·hm^-2 in litter, 1.2 t·hm^-2 in herbaceous and 0.6 t·hm^-2 in shrubs. In comparison, carbon storage of soil layer in forests in Nei Mongol was 2449.6 Tg C, with 79.8% distributed in the first 30 cm. Carbon density of soil layer was 144.4 t·hm^-2. Carbon storage of forest ecosystem in Nei Mongol was 3237.4 Tg C, with vegetation and soil accounting for 24.3% and 75.7%, respectively. Carbon density of forest ecosystems in Nei Mongol was 184.5 t·hm^-2. Carbon density of soil layer was positively correlated with that of vegetation layer. Spatially, both carbon storage and carbon density were higher in the eastern area, where the climate is more humid. Forest reserves and artificial afforestations can significantly improve the capacity of regional carbon sink.     

内蒙古典型草原优势种冷蒿和克氏针茅对土壤低磷环境适应策略的比较

为探究典型草原植物长期共存的生理生态机制, 以典型草原的优势物种克氏针茅(Stipa krylovii)和冷蒿(Artemisia frigida)为材料, 采用基质培养方法, 通过比较不同供磷浓度对二者生物量、根系形态、质子分泌、酸性磷酸酶和有机酸分泌以及磷吸收利用效率的影响, 探讨克氏针茅和冷蒿对土壤磷缺乏的适应策略。研究结果表明: 冷蒿主要通过根系分泌酸性磷酸酶和酸化根际来适应低磷环境; 而克氏针茅主要是通过根系分泌有机酸(主要是苹果酸)来适应土壤磷缺乏。在低磷条件下, 克氏针茅和冷蒿的磷吸收效率没有显著差异, 但克氏针茅的磷利用效率显著高于冷蒿。随着供磷浓度增加, 二者的磷吸收速率增加, 磷利用效率降低。在生物量、地上部分性状以及根系生长方面, 克氏针茅和冷蒿对磷供给的响应都表现先增长后降低的趋势; 克氏针茅的生物量在外源供0.25 mmol·L^-1磷时达到最大, 而冷蒿的生物量在外源供0.50 mmol·L^-1磷时达到最大, 表明冷蒿对磷的生理需求高于克氏针茅。因此, 克氏针茅和冷蒿具备各自不同的适应土壤有效磷缺乏的生理策略, 这可能是它们在土壤贫瘠的温带典型草原长期共存的重要机制。     

Responses of soil moisture to precipitation pattern change in semiarid grasslands in Nei Mongol,China

Aims Under global climate change, precipitation patterns were predicted to change with larger seasonal and annual variations and more extreme events in the semiarid regions of northern China. Water availability is one of the key limited factors in semiarid grasslands. Changes in precipitation patterns will inevitably affect ecosystem structure and function through soil water condition. Our objective was to investigate the response of soil water content to changes of precipitation pattern, especially its pulse response to precipitation events.
Methods Two semiarid steppe sites (Duolun and Xilinhot) in Nei Mongol were chosen and meteorological stations were installed to monitor precipitation and soil volumetric water content (VWC) at five soil depths (0-10 cm, 10 cm, 20 cm, 30 cm, 50 cm) from 2006 to 2013. The pulse response of VWC at 0-10 cm to an individual precipitation event was simulated by an exponential equation.
Important findings Significant seasonal and inter-annual variations of VWC were observed at the Duolun and Xilinhot sites. VWC at 50 cm soil layer in Xilinhot showed an obvious increase during the early spring due to the influences of snow melting. Mean surface (0-10 cm soil layer) VWC was significantly correlated with annual precipitation across eight years, but VWC in the deeper soil layers (10-50 cm) were not impacted by precipitation. We also found that the precipitation event larger than 2 mm could induce a significant increase in surface (0-10 cm soil layer) VWC, and could be regarded as an effective precipitation in this region. The maximum increment of surface VWC after the events and lasting time (T_lasting) were determined by the event size, while showed negatively linear correlations with the initial soil water content before the events. Vegetation development (leaf area index) did not show significant impacts on the responses of surface soil moisture to precipitation pulses. The infiltration depth of rain water was also determined by rain size and pre-event soil moisture. In average, soil water can infiltrate 1.06 cm and 0.79 cm deeper in Duolun and Xilinhot with 1 mm more precipitation, respectively. Therefore, our results suggest that the event size and pre-event soil moisture were the most important factors affecting response patterns of soil moisture to rain events in semiarid ecosystems.     

降水变化对内蒙古典型草原地上生物量的影响

降水格局的变化是气候变化影响干旱和半干旱区草原植物群落结构和功能的关键过程。作为植物群落结构和功能的基本组成单位——植物功能群——对气候变化的响应差异明显。有关不同植物功能群如何响应降水格局的研究, 有助于揭示气候变化对干旱与半干旱区生态系统关键功能与过程稳定性的变异机制。该文利用1982-2015年的典型草原群落地上生物量长期动态监测数据及其所对应的气候数据, 系统揭示降水变化对干旱与半干旱区生态系统生产力的影响。主要研究结果如下: 1) 1982-2015年内蒙古典型草原区降水变化特征明显, 主要表现在降水集中度呈显著的降低趋势; 小降水事件(≤5 mm)明显增多。2)降水变化导致群落生物量呈下降趋势。其中, 多年生丛生禾草的生物量呈上升趋势; 一二年生植物、多年生杂类草、多年生根茎禾类草的生物量均呈下降趋势。3)群落生物量与生长季降水量、降水集中度呈显著的正相关关系。各功能群中, 多年生杂类草、半灌木和生长季降水量呈显著正相关关系, 灌木与降水集中度呈显著负相关关系。4)群落生物量与各等级降水的频率相关性均不显著, 但与I-II类(0.1-10 mm)降水贡献率显著负相关。各功能群中, 多年生杂类草与I类降水(0.1-5.0 mm)的发生频率和降水贡献率均呈显著的负相关关系, 与VI类降水(20-25 mm)的发生频率和贡献率均呈显著的正相关关系。多年生根茎禾类草和VIII类降水(>35 mm)的发生频率和贡献率均呈显著的正相关关系。说明小降水事件的增加将显著降低群落的地上生物量, 小降水事件对干旱、半干旱区植被生长具有重要的生态学意义。     

Seasonal dynamics of leaf C,N and P stoichiometry in plants of typical steppe in Nei Mongol,China

分析植物叶片(C)、氮(N)、磷(P)含量及其比值的季节动态, 不仅有助于认识植物生长发育和养分吸收利用等生理生态过程, 也有利于认识植物化学计量的动态平衡关系。该文选择内蒙古典型温带草原18种常见植物, 在生长季的6-9月, 每半月一次进行连续采样, 在此基础上分析了叶片C、N、P含量及其比值在生长季内的变化。主要结果: 1)植物叶片C、N、P含量及其比值的季节性变化在不同功能类群间不同步, 其中叶片N、P含量的季节变化体现了明显的稀释作用。2)叶片C、N、P含量及其比值在不同功能类群间差异显著, 单子叶、多年生禾草类的叶片N、P含量显著低于双子叶和多年生杂类草植物, 而其叶片C:N、C:P则高于双子叶和多年生杂类草植物。3)叶片N、P含量显著正相关, 叶片C:N和C:P分别与N和P含量显著负相关, 可能体现了植物体内营养元素间的内在耦合机制。4)叶片N含量与C:N, 叶片P含量与C:P以及叶片N含量与P含量均呈现等速生长关系, 且等速生长关系在生长季保持稳定。