Multifunctionality and Thresholds of Alpine Grassland on the Tibetan Plateau

Ecosystems can simultaneously provide multiple functions and services. Knowledge on the combinations of such multi-dimensional functions is critical for accurately assessing the carrying capacity and implementing sustainable management. However, accurately quantify the multifunctionality of ecosystems remains challenging due to the dependence and close association among individual functions. Here, we quantified spatial patterns in the multifunctionality of alpine grassland on the Tibetan Plateau by integrating four important individual functions based on data collected from a field survey and remote sensing NDVI. After mapping the spatial pattern of multifunctionality, we extracted multifunctionality values across four types of grassland along the northern Tibet Plateau transect. Effects of climate and grazing intensity on the multifunctionality were differentiated. Our results showed that the highest values of multifunctionality occurred in the alpine meadow. Low values of multifunctionality were comparable in different types of grassland. Annual precipitation explained the large variation of multifunctionality across the different types of grassland in the transect, which showed a significantly positive effect on the multifunctionality. Grazing intensity further explained the rest of the variation in the multifunctionality (residuals), which showed a shift from neutral or positive to negative effects on multifunctionality across the different types of grassland. The consistently rapid declines of belowground biomass, SOC, and species richness resulted in the collapse of the multifunctionality as bare ground cover amounted to 75%, which corresponded to a multifunctionality value of 0.233. Our results are the first to show the spatial pattern of grassland multifunctionality. The rapid decline of the multifunctionality suggests that a collapse in the multifunctionality can occur after the vegetation cover decreases to 25%, which is also accompanied by rapid losses of species and other individual functions. Our results are expected to provide evidence and direction for the sustainable development of alpine grassland and restoration management.     

放牧对古尔班通古特沙漠南部半固定沙垄地表性质的影响

Intensive grazing in spring-summer has been responsible for environmental deg- radation of the Gurbantunggut Desert in recent years. The coverage of plants and biological crusts, sand surface stability and physicochemical characteristics of soil on the dune surface were conducted in 2002 (winter grazing) and 2005 (spring-summer grazing). The results showed that over 80% of the total area of the dune surface was covered by well-developed biological crusts and plants in 2002, when the interdune and middle to lower part of dune slopes were stabilized and only the crest had 10-40 m wide mobile belt. Affected by spring-summer grazing in 2005, over 80% of the total cover of biological crust was destructed and the plant coverage only reached 1/5 of that in 2002, especially the ephemeral plant cover had a great change. The value of sand transport potential in 2005 only reached 1/3 of that in 2002, but the total surface activity in 2005 was 1.6 times stronger than that in 2002. Mean- while the mobile area began to expand from the dune top to the whole dune surface following spring-summer grazing. Compared with 2002, medium sand content of the dune surface soil increased by 13.9%, while that of fine and very fine sands decreased by 7.4% and 8.0% re- spectively in 2005 and the soil organic matter in 2005 was only about 1/2 of that in 2002. It is obvious that the presence of snow cover and frozen soil in winter could avoid the surface structure destruction in winter, while spring--summer grazing made excessive damage to biologic crusts and ephemeral plants. Spring is the main windy season in Gurbantunggut Desert and therefore intensive activity of dune surface occurred following spring-summer grazing, which led to a great loss of fine sand and organic matter. It can be seen that grazing season have a significant influence on the sustainable development of the desert ecosystem in Northwest China.     

放牧对阿拉善荒漠草地土壤性状的影响

对阿拉善荒漠草地不同放牧条件下土壤理化性状的变化进行了研究,结果表明:在草地基况一致的条件下,经过连续6a不同强度的放牧,0~ 20cm土层土壤容重轻牧和重牧区低于中牧区。随着放牧强度的增加,土壤颗粒组成极粗砂、粗砂和中砂含量增加,细砂、极细砂、粉砂和粘粒含量减少,过度放牧加快了土壤风蚀沙化。0~20cm土层中土壤有机C、全P的含量和C/N随着放牧强度的增加而依次降低;全N、全K、pH末发生明显变化;速效N和速效K重牧区显著高于轻牧区和中牧区;速效P轻牧区高于中、重牧区。土壤有机C与全P、速效P呈显著正相关;全P与速效N和K呈显著负相关,与速效P呈显著正相关(P<0.05)。     

不同放牧方式对岩溶区土壤养分的影响 ——以广西桂林岩溶区实验基地为例

根据实验数据,探讨了不同放牧方式对岩溶区土壤的肥力、微量元素含量、水涵养性等的影响。结果表明,在正常放牧的情况下,能迅速提高牧草区土壤的养分和水的涵养性,减少水土流失,灌木种植初期不宜进行放牧;而在人为破坏和过度放牧的情况下,可在短期内导致岩溶区生态环境向着恶化的方向演替,土壤养分的各项指标下降到甚至低于未修复前的状态。     

土壤重金属生物有效性研究进展

土壤重金属污染具有巨大环境风险。笔者围绕土壤重金属元素生物有效性(可给性)概念、元素形态与有效性影响因素、有效态(可给态)实验技术,综述了国内外研究现状。土壤金属元素形态和生物有效性取决于其地球化学行为、元素成因来源、土壤理化条件(p H值、有机质、粘土矿物与化学活性矿物、土壤粒级组成等)以及植物根际效应等。选择性单步提取和连续提取是检测土壤元素形态、有效态的有效和可行方法。针对手—口是土壤铅等污染物在儿童群体暴露的重要途径,发展了生物可给态体外试验方法。土壤污染物生物有效性和可给性已成为土壤污染风险评价的重要指标参数,实验成果也为土壤污染修复提供了重要依据。     

蒙脱石等粘土矿物对重金属离子吸附选择性的实验研究

矿物质与重金属离子间的相互作用已是当今环境科学、矿物学,土壤化学等学科领域研究的热点。通过蒙脱石,伊利石和高龄石在一定的介质条件下对Ｃｕ＾２＋、Ｐｂ＾２＋、Ｚｎ＾２＋、Ｃｄ＾２＋、Ｃｒ＾３＋五种重金属离子的竞争吸附实验研究,阐明了三种粘土矿物对五种重金属离子的吸附选择性。     

利用改进三分量分解与Wishart分类的极化SAR图像建筑提取

本文针对基于Freeman分解的建筑提取方法存在的问题, 提出采用圆极化相关系数实现选择性去取向, 同时引入广义体散射模型, 构建面向建筑提取的改进三分量分解模型, 以准确分析地物的散射特性。在此基础上, 发展了一种综合利用改进三分量分解与Wishart迭代分类算法的极化SAR图像建筑提取方法。使用E-SAR全极化数据的试验结果表明, 本文方法能够有效减少建筑与植被的误分, 并提高建筑信息提取的准确性。     

野生坛紫菜的选育及经济性状的研究

从福建平潭岛不同生境采集的野生坛紫菜,经过2~3 a的筛选和培育获得野生品系b,c和d,通过体细胞酶解和自繁,获得丝状体和叶状体。实验结果表明:(1)野生选育品系b,c,d生长较快,日生长达3.25~3.75 cm/d,未选育的品系a日生长为2.12 cm/d,传统的养殖品种生长速度慢,日生长仅有1.37 cm/d;(2)选育的品系b对高温具有明显的耐受性,在高温30℃培养10 d,日平均增重率达4.34%,而对照组在水温27℃时培养5 d以上,藻体就开始腐烂;(3)品系b耐低氮、磷能力较强,在低氮、磷培养条件下,第9天色泽变为浅黄色,但没有腐烂死亡,此时将藻体移至含有氮、磷的正常培养液下培养3 d,藻体就可恢复正常,对照组的藻体在相同条件下,第6天藻体中部就开始糜烂,第9天叶片就有2/3溃烂;(4)在品质方面,品系b的总藻胆蛋白含量高达98.89mg/g,对照组的总藻胆蛋白含量仅有50.04 mg/g;本研究结果可为坛紫菜的遗传改良、野生品系选育及利用奠定基础。     

放牧强度对内蒙古半干旱草原地气间能量和物质交换的影响

利用涡度相关技术, 于2006年7月27日至8月10日在内蒙古半干旱草原三种放牧强度的下垫面进行微气象观测。本文分析了放牧强度对内蒙古半干旱草原地气间能量和物质交换的影响, 发现: (1)放牧降低植被覆盖率, 使地表反射率增大。(2)放牧使潜热通量减小。而放牧强度最大的锡林河河道潜热通量最大,表明土壤水分状况是半干旱草原地表能量收支的决定性因素。(3)羊草和冬季放牧观测点日平均CO2通量分别为-1.92 g?m-2?d-1和0.73 g?m-2?d-1, 表明放牧可以使草地由CO2的汇转变为源。锡林河河道为CO2的汇, 日平均CO2通量-3.35 g?m-2?d-1, 与羊草比较, 锡林河河道吸收CO2更多, 表明土壤湿度是影响半干旱草原CO2通量交换的重要因素。(4) 放牧通过减小叶面积指数, 减弱植被的光合作用能力。     

牧户对退牧还草工程的行为响应及其影响因素研究——以高寒牧区玛曲县为例

 以高寒牧区玛曲县为例,应用最优尺度回归模型对当地牧民在退牧还草工程影响下的行为响应及其影响因素进行定量分析,以研究牧民在进行行为选择时的规律性因素。研究表明,牧户的受教育程度、家庭收入水平、牧户从政府保护草原的政策中的获益程度和草地退化认知程度对牧户参与退牧还草工程的响应程度有显著正向影响,而户主的年龄、家庭规模和草场面积有显著负向影响。为了使退牧还草工程变成牧户的自觉行动并长期坚持下去,应把牧户的经济发展与退牧还草工程紧密相连,只有着眼于牧民畜牧生产观念的转变,牧户的经济有很大发展,退牧还草的持续性才能保证。