Temporal and spatial variation characteristics of China shrubland net primary production and its response to climate change from 2001 to 2013

Aims Net primary production (NPP) is the input to terrestrial ecosystem carbon pool. Climate and land use change affect NPP significantly. Shrublands occupy more than 20% of the terrestrial area of China, and their NPP is comparable to those of the forests. Our objective was to estimate China shrubland NPP from 2001 to 2013, and to analyze its variation and response to climate change.Methods We used a Carnegie-Ames-Stanford Approach (CASA) model to estimate the NPP of six shrubland types in China from 2001 to 2013. Furthermore, we used Theil-Sen slope combined with Mann-kendall test to analyze its spatial variation and a linear regression of one-variable model to analyze its inter- and intra-annual variation. Finally, a multi-factor linear regression model was used to analyze its response to climate change.Important findings We found the annual mean NPP of China shrubland was 281.82 g•m^-2•a^-1. The subtropical evergreen shrubland has the maximum NPP of 420.47 g•m^-2•a^-1, while the high cold desert shrubland has the minimum NPP of 52.65 g•m^-2•a^-1. The countrywide shrublands NPP increased at the rate of 1.23 g•m^-2•a^-1, the relative change rate was 5.99%. The temperate deciduous shrubland NPP increased the fastest with a speed of 3.05 g•m^-2•a^-1 and subalpine evergreen shrubland had a decreasing trend with a speed of -0.73 g•m^-2•a^-1. Moreover, the other four shrublands NPP had a growing trend, only subalpine deciduous shrubland NPP did not change significantly. The response of NPP to climate change of different seasons varies to different shrubland types. In general, the NPP variation was mainly affected by precipitation, and the spring warming also contributed to it. The increase of countrywide shrubland NPP may promote its contribution to the regional ecosystem function.     

Brassinosteroids promote development of rice pollen grains and seeds by triggering expression of Carbon Starved Anther,a MYB domain protein

Transport of photoassimilates from leaf tissues (source regions) to the sink organs is essential for plant development. Here, we show that a phytohormone, the brassinosteroids (BRs) promotes pollen and seed development in rice by directly promoting expression of Carbon Starved Anther (CSA) which encodes a MYB domain protein. Over‐expression of the BR‐synthesis gene D11 or a BR‐signaling factor OsBZR1 results in higher sugar accumulation in developing anthers and seeds, as well as higher grain yield compared with control non‐transgenic plants. Conversely, knockdown of D11 or OsBZR1 expression causes defective pollen maturation and reduced seed size and weight, with less accumulation of starch in comparison with the control. Mechanically, OsBZR1 directly promotes CSA expression and CSA directly triggers expression of sugar partitioning and metabolic genes during pollen and seed development. These findings provide insight into how BRs enhance plant reproduction and grain yield in an important agricultural crop.     

广西石山人工林灌草多样性与环境因子的关系

以广西石山人工林群落调查数据为材料,采用双向指示种分类(TWINSPAN)、冗余分析(RDA)和典范对应分析(CCA)研究了9个生境变量、1林分类型因子与石山人工林多样性、草本和灌木植物组成的关系。结果表明,坡位是影响石山人工林物种组成多样性的最主要因子,露石率和坡度对石山人工林林下有害物种分布影响最大。石山人工林林下植被组成的主要决定因素是生境因子(解释率23%~55%),而树种选择是次要因素(解释率11%~17%)。石山梯地人工林的有害草本种类多于坡地,梯地的有害灌木种类少于坡地。石山人工林的有害植物种类少于封山育林地。     

蚂蚁筑巢对不同恢复阶段热带森林土壤易氧化有机碳时空动态的影响

为探明热带森林恢复过程中蚂蚁筑巢对土壤易氧化有机碳(readily oxidizable carbon, ROC)时空动态的影响及机制, 本研究以西双版纳白背桐(Mallotus paniculatus)群落、野芭蕉(Musa acuminata)群落和崖豆藤(Mellettia leptobotrya)群落3种恢复阶段热带森林为研究对象, 设置“蚂蚁筑巢地”与“非巢地”2种处理进行野外控制实验, 对比分析蚁巢和非蚁巢土壤ROC含量的时空变化特征, 并揭示这些变化与土壤微生物生物量碳及理化性质之间的相互关系。结果表明: (1)蚂蚁筑巢显著影响热带森林土壤ROC含量(P < 0.05), 蚁巢土壤ROC含量较非蚁巢提高了14.2%。不同恢复阶段蚁巢与非蚁巢土壤ROC含量大小顺序为: 野芭蕉群落 > 崖豆藤群落 > 白背桐群落。(2)不同恢复阶段热带森林蚁巢与非蚁巢土壤ROC含量均呈单峰型的时间变化趋势(P < 0.05), 最大值出现在6月, 且各月份蚁巢土壤ROC含量均高于非蚁巢。(3)不同恢复阶段热带森林蚁巢和非蚁巢土壤ROC含量均随土层深度增加呈显著递减的垂直变化趋势(P < 0.05), 且蚁巢土壤ROC含量均大于非蚁巢(P < 0.05)。(4)蚂蚁筑巢引起的土壤理化性质变化对土壤ROC含量产生了一定的影响。土壤ROC含量与土壤pH和容重呈显著负相关(P < 0.05), 与土壤有机碳、微生物生物量碳、全氮、铵态氮及硝态氮呈显著正相关(P < 0.05)。土壤微生物生物量碳与总有机碳是蚁巢土壤ROC时空变化的主要贡献者, 而铵态氮、全氮和总有机碳是非蚁巢ROC时空变化的主控因子。因此, 蚂蚁筑巢改变热带森林土壤微生物量(如微生物生物量碳)及土壤理化性质(如总有机碳、铵态氮与全氮等), 进而显著影响土壤ROC的时空动态。     

土壤活性有机碳的表征及其生态效应

土壤活性有机碳指在一定的时空条件下,受植物、微生物影响强烈、具有一定溶解性、在土壤中移动比较快、不稳定、易氧化、分解、易矿化,其形态,空间位置对植物、微生物来说活性比较高的那一部分土壤碳素。国外描述这一部分碳素的术语为有效碳、水溶性碳、易氧化碳、可矿...     

Is there an associational resistance of winter pea–durum wheat intercrops towards Acyrthosiphon pisum Harris?

Acyrthosiphon pisum Harris (Aphididae: Hemiptera), the pea aphid, is an important pest in organic farming systems. In this work, the objective was to gather empirical field data on the associational resistance of durum wheat–winter pea intercrops towards the pea aphid, compared with pure stands of winter pea. Our results showed that intercropping winter pea with durum wheat significantly decreased A. pisum abundance in all the situations. Moreover, it was systematically observed that pea grew bigger in pure than in intercropped stands but after considering pea dry mass as a covariate, it appeared that the durum wheat–winter pea intercrop was still significantly less attacked by pea aphids than the sole crop. Intercrop sowing designs had an incidence on infestation levels: substitutive diversification systems of different types are more effective in decreasing the level of aphid infestation than does the additive system. In addition, substitutive row intercrop is significantly less infested than substitutive mixture. These results suggest that a mechanism related to the resource concentration hypothesis may explain the associational resistance of the IC of durum wheat–winter pea towards A. pisum.     

Factors controlling the stable isotope composition and C:N ratio of seston and periphyton in shallow lake mesocosms with contrasting nutrient loadings and temperatures

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Cycling of soil carbon in a Japanese red pine forest II. Changes occurring in the first year after a clear-felling

Cycling of soil carbon in the first year after a clear-felling was compared with that before the felling in a Japanese red pine forest in Hiroshima Prefecture, west Japan. The daily mean temperature at the soil surface in summer was increased after the felling in comparison to that before felling, and the water content of both the A₀ layer and the surface mineral soil was decreased due to the loss of the forest canopy. The rate of weight loss of the A₀ layer was reduced after felling. However, accumulation of the A₀ layer rapidly decreased because of the lack of litter supply to the forest floor. Low soil respiration after felling was mainly caused by the cessation of root respiration. Analysis of annual soil carbon cycling was then conducted using a compartment model. The relative decomposition rate of the A₀ layer decreased whereas that of humus and dead roots in mineral soil increased to some extent after felling. The accumulation of carbon in mineral soil, however, increased slightly due to the supply of humus from roots killed by the felling.     

Mechanism of Na‐Ion Storage in Hard Carbon Anodes Revealed by Heteroatom Doping

Hard carbon is the leading candidate anode for commercialization of Na‐ion batteries. Hard carbon has a unique local atomic structure, which is composed of nanodomains of layered rumpled sheets that have short‐range local order resembling graphene within each layer, but complete disorder along the c‐axis between layers. A primary challenge holding back the development of Na‐ion batteries is that a complete understanding of the structure–capacity correlations of Na‐ion storage in hard carbon has remained elusive. This article presents two key discoveries: first, the characteristics of hard carbons structure can be modified systematically by heteroatom doping, and second, that these structural changes greatly affect Na‐ion storage properties, which reveals the mechanisms for Na storage in hard carbon. Specifically, via P or S doping, the interlayer spacing is dilated, which extends the low‐voltage plateau capacity, while increasing the defect concentrations with P or B doping leads to higher sloping sodiation capacity. The combined experimental studies and first principles calculations reveal that it is the Na‐ion‐defect binding that corresponds to the sloping capacity, while the Na intercalation between graphenic layers causes the low‐potential plateau capacity. The understanding suggests a new design principle of hard carbon anode: more reversibly binding defects and dilated turbostratic domains, given that the specific surface area is maintained low.