Using the RBFN model and GIS technique to assess wind erosion hazard of inner Mongolia, China

Soil wind erosion is the primary process and the main driving force for land desertification and sand-dust storms in and and semi-arid areas of Northern China. While many researchers have studied this issue, this study quantified the various indicators of soil wind erosion, using the GIS technology to extract the spatial data and to construct a RBFN (Radial Basis Function Network) model for Inner Mongolia. By calibrating sample data of the different levels of wind erosion hazard, the model parameters were established, and then the assessment of wind erosion hazard. Results show that in the southern parts of Inner Mongolia wind erosion hazards are very severe, counties in the middle regions of Inner Mongolia vary from moderate to severe, and in eastern are slight. Comparison of the results with other research shows conformity with actual conditions, proving the reasonability and applicability of the RBFN model. Copyright (C) 2007 John Wiley & Sons, Ltd.

Effects of nitrogen fertilization on soil respiration in temperate grassland in Inner Mongolia, China

Nitrogen addition to soil can play a vital role in influencing the losses of soil carbon by respiration in N-deficient terrestrial ecosystems. The aim of this study was to clarify the effects of different levels of nitrogen fertilization (HN, 200 kg N ha(-1) year(-1); MN, 100 kg N ha(-1) year(-1); LN, 50 kg N ha(-1) year(-1)) on soil respiration compared with non-fertilization (CK, 0 kg N ha(-1) year(-1)), from July 2007 to September 2008, in temperate grassland in Inner Mongolia, China. Results showed that N fertilization did not change the seasonal patterns of soil respiration, which were mainly controlled by soil heat-water conditions. However, N fertilization could change the relationships between soil respiration and soil temperature, and water regimes. Soil respiration dependence on soil moisture was increased by N fertilization, and the soil temperature sensitivity was similar in the treatments of HN, LN, and CK treatments (Q (10) varied within 1.70-1.74) but was slightly reduced in MN treatment (Q (10) = 1.63). N fertilization increased soil CO2 emission in the order MN > HN > LN compared with the CK treatment. The positive effects reached a significant level for HN and MN (P < 0.05) and reached a marginally significant level for LN (P = 0.059 < 0.1) based on the cumulative soil respiration during the 2007 growing season after fertilization (July-September 2007). Furthermore, the differences between the three fertilization treatments and CK reached the very significant level of 0.01 on the basis of the data during the first entire year after fertilization (July 2007-June 2008). The annual total soil respiration was 53, 57, and 24% higher than in the CK plots (465 g m(-2) year(-1)). However, the positive effects did not reach the significant level for any treatment in the 2008 growing season after the second year fertilization (July-September 2008, P > 0.05). The pairwise differences between the three N-level treatments were not significant in either year (P > 0.05).

Evaluation of a sequential extraction for the speciation of thorium in soils from Baotou area, Inner Mongolia

Sequential extraction procedures were widely applied for speciation of radioactive elements. In this study, the sequential extraction procedure developed by Martinez-Aguirre was employed for quantification of different chemical forms of thorium in the soil. The total amount of thorium in contaminated soil was much higher by four-fold than the local background value. The soil properties affect the amount of thoriurn and distribution of fractions in contaminated soil. Results showed that the proportion of thorium in soils from Baotou was found as the residual fraction (F5 + F6) > absorbed fraction (F3), coprecipitated fraction (F4) > carbonates fraction (172) and exchangeable fraction (F1) that could be available to plants. The recovery, calculated by ratio of the sum of the six fractions to the pseudo-total content of thorium, was in the range from 96% to 110%. A comparison was carried out between the sequential extraction and the single extraction to evaluate the selectivity of the extractants. It was found that the amount of thorium of absorbed fraction (H) was higher in the single extraction than that estimated in the sequential extraction, possibly duo to transform of the labile form. While for non-residual fraction analysis, the single extraction scheme was a desirable alternative to the sequential extraction procedure.

Effect of long-term grazing on soil organic carbon content in semiarid steppes in Inner Mongolia

To clarify the response of soil organic carbon (SOC) content to season-long grazing in the semiarid typical steppes of Inner Mongolia, we examined the aboveground biomass and SOC in both grazing (G-site) and no grazing (NG-site) sites in two typical steppes dominated by Leymus chinensis and Stipa grandis, as well as one seriously degraded L. chinensis grassland dominated by Artemisia frigida. The NG-sites had been fenced for 20 years in L. chinensis and S. grandis grasslands and for 10 years in A. frigida grassland. Above-ground biomass at G-sites was 21-35% of that at NG-sites in L. chinensis and S. grandis grasslands. The SOC, however, showed no significant difference between G-site and NG-site in both grasslands. In the NG-sites, aboveground biomass was significantly lower in A. frigida grassland than in the other two grasslands. The SOC in A. frigida grassland was about 70% of that in L. chinensis grassland. In A. frigida grassland, aboveground biomass in the G-site was 68-82% of that in the NG-site, whereas SOC was significantly lower in the G-site than in the NG-site. Grazing elevated the surface soil pH in L. chinensis and A. frigida communities. A spatial heterogeneity in SOC and pH in the topsoil was not detected the G-site within the minimal sampling distance of 10 m. The results suggested that compensatory growth may account for the relative stability of SOC in G-sites in typical steppes. The SOC was sensitive to heavy grazing and difficult to recover after a significant decline caused by overgrazing in semiarid steppes.

磷酸肌醇信号途径对青扦花粉萌发和花粉管发育的调控作用及芦苇叶细胞壁结构的生理生态学研究

植物在长期的进化过程中，已经对其生存环境具备了各种适应对策。放牧影响下草原植物的生态适应策略，决定了其是否能够忍耐或者适应放牧生境从而维持自身的生存和种群的延续。研究植食性动物对植物的影响有助于制定合理的放牧制度和草地利用方式，从而为防止草原退化和恢复退化草地提供重要的理论依据;同时研究植物对放牧的响应策略，对于草原生物多样性的保护和草原生物资源的合理利用具有重要的理论和实践意义。 本文以中科院内蒙古草原生态系统定位研究站放牧综合试验样地中的小叶锦鸡儿为主要研究对象。通过长期不同放牧强度的放牧试验和唾液涂抹等模拟试验，从形态学、有性生殖、种子萌发和遗传多样性等方面，探讨了小叶锦鸡儿对放牧家畜（绵羊）采食的生物学响应。本研究得到以下主要结论： 1. 通过小叶锦鸡儿形态和有性生殖的实验，可以看到放牧改变了该种植物的形态和生殖特性，不同放牧强度对其影响的程度是不相同的。在啃食压力下，小叶锦鸡儿的营养、生殖和防御之间存在消长关系。随着放牧强度的增加，小叶锦鸡儿对营养器官和有性生殖器官的投资均减少，而对防御器官的投资有增加的趋势，主要体现在：个体的小型化（植株高度、叶轴长度、小叶大小）和果荚数目及成熟种子数都随着放牧强度的增加而明显减少;物理性防御器官――刺，其密度和长度都明显的增加。同时，放牧也对植物花粉的品质产生了消极影响。 2. 放牧不仅影响了植物体本身的生物学特性，而且影响了子代的生物学特性。不同放牧强度下的植株产生的种子，其萌发速率明显不同。同时放牧强度和沙埋深度对小叶锦鸡儿的出苗率均具有显著影响，随着沙埋深度增加，出苗率明显降低，0～2cm是其适宜出苗的沙埋深度;浅层沙埋处理下，轻度放牧和重度放牧的出苗率差异显著。与轻度放牧相比，重牧条件下同一沙埋深度的种子出苗时间明显推迟;在相同放牧压力下，沙埋深度也影响了出苗时间。 3. 采食活动对植物本身的形态、生殖以及子代的萌发特性都产生了影响;通过AFLP实验证明了小叶锦鸡儿在长期的放牧历史活动中已经发生了遗传多样性的变化，重度放牧强度下的植株与轻度放牧条件下的植株具有相对较远的遗传距离，也就是说，小叶锦鸡儿种群的分化与放牧强度具有密切的关系。 4. 三种不同生活型植物（灌木-小叶锦鸡儿、半灌木-冷蒿和草本-羊草）对绵羊唾液涂抹的响应不同，刈割和涂抹绵羊唾液能够增加植物的净地上生物量，并促进植株增加地上部分的光合产物投资。同时表明，简单的机械剪除不能够真正反应放牧家畜采食所产生的生物学效应。

放牧对内蒙古冷蒿小禾草草原植物群落特征的影响

了解天然草原放牧生态系统中，不同管理措施对草－畜系统的影响及系统中草－畜互作方式，是实现草原生态系统持续管理的基础。在内蒙古典型草原区，我们建立了24hm2围栏放牧实验样地。本文通过对试验样地5个放牧率（1.33，2.67，4.00，5.33和6.67羊／hm2）和两种放牧方式下（连续放牧与轮牧）一年排除放牧后植被变化的研究，试图揭示8年的放牧对草地群落的作用结果，探寻放牧率与植物群落生产力、种类组成和演替方向的关系，以求为建立合理的放牧制度提供佐证。 研究发现：①不同的放牧率下8年的放牧使地上生物量出现显著差异，中度放牧（SR3）下的草原群落达到了最大地上生物量，在较轻的放牧率（SR1，SR2）下有超补偿生长出现，地下生物量随着放牧率的升高而下降。②放牧使群落植物组成发生重大变化，随着放牧率的升高，表现出明显的向星毛委陵菜退化草原演替的趋势，无牧的群落表现出恢复演替的趋势。③在轻牧（SR1）处理下植物群落达到了最高的多样性，在多样性与生物量之间，不能发现较具规律性的关系。④轮牧群落的生产力潜力显著高于连续放牧，连续放牧方式造成植物斑块状分布，降低了草场的利用效率。⑤放牧造成了草原植物生态位分化。