ANALYSIS OF DRIVING FORCES ON THE CHANGE OF HISTORICAL FARMLAND USE IN SHANDONG PROVINCE DURING THE QING DYNASTY (1644-1911)

National Natural Science Foundation of China [40201005]; Knowledge Innovation Project of Chinese Academy of Sciences [KZCX3-SW-321, KZCX2-314, KZCX1-SW-321-4]

粗枝云杉( Picea asperata Mast.)天然群体的遗传变异

西南地区在我国的经济发展和生态环境建设中占重要地位，但也是我国生态环境最脆弱的地区之一，生态系统退化，生态功能减弱，严重制约着西南林业的可持续经营与发展。本项目采用DNA 分子标记SSR 研究不同生境条件下粗枝云杉群体的遗传变异及其时空分布格局，考察遗传变异与复杂的山地生态环境间的潜在联系，系统地揭示粗枝云杉天然群体与环境系统相互作用的生态适应与分子进化机制。粗枝云杉适应性强，生长迅速，在植树造林和工业用材方面占有重要地位，研究成果可为中国西南部亚高山天然林的可持续经营及退化生态系统的恢复与重建提供理论依据和科学指导。主要研究结果如下： 1. SSR 位点变异丰富，等位基因频率的分布格局多样。7 个SSR 标记全是多态位点，每位点的等位基因数变化范围为13~24，平均为19.9 个。SSR 位点的等位基因片段长度范围变化较大。73.1%的等位基因变异遵循逐步突变模型(SSM)而发生1 个重复基元的变化，22.3%和4.6%的变异分别按两阶段突变模型(TMP)发生1 个重复基元以上的变化和在SSR 位点侧翼区发生1 个碱基变化的插入-删除事件。 2. 粗枝云杉拥有中等偏高水平的遗传多样性和相对大的群体间遗传分化。通过分析代表10 个群体的250 个个体在7 个SSR位点的变化，调查了源自中国西南山区的粗枝云杉的微卫星变异。相当高的遗传多样性和强烈的群体分化发生在粗枝云杉中， 其群体平均Nei's 期望杂合度为0.707 ， 群体间遗传距离为0.121~0.224(FST)和0.100~0.537(RST)。然而，群体间遗传距离与地理距离之间无相关性，从而排除了简单的距离分离模式并暗示迁移不是影响粗枝云杉遗传变异格局的主要因素。事实上，使用私有等位基因估算的基因流数量非常低，仅等于0.753。等位基因置换检验(Allele permutation tests)揭示逐步突变及遗传漂变都对群体间分化有贡献。另外，在多数位点检测到显著的群体间遗传差异，这个结果说明自然选择，假设通过环境压力，是引起粗枝云杉微地理分化的主要因素之一。根据SSR基因型，250 个粗枝云杉个体的70%被正确地归类入其各自的来源群体，结果表明微卫星(SSR)对区分来自中国不同生态地理位点的粗枝云杉基因型是有效的。 3. 在SSR、RAPD 和AFLP 位点，显著的群体间遗传结构被发现的，但三种标记间遗传分化程度和群体遗传关系有差异。利用来自10 个群体的247 个个体，我们报告了关于样本粗枝云杉群体间遗传关系的总体看法。根据各自对评价遗传关系的信息能力和适用性，SSR、RAPD 和AFLP 标记被选用，三种技术非常有效地区别这些基因型。使用的SSR、RAPD 和AFLP 标记分别估计平均Dice 相似性系数。Mantel 检验产生显著但相对低的共表型适合度(RAPD = 0.63£AFLP = 0.60和SSR = 0.75)。比较三种标记系统，RAPD 和AFLP 共表型指数相对高地相关(r =0.59)，而RAPD 和SSR 及SSR 和AFLP 之间的相关系数分别是0.53 和0.35。所有系统树，包括不同标记资料结合获得的系统树，反映了多数群体依据它们的地理条件而成某种特定关系。结果暗示单个或结合标记系统能用来深入洞察粗枝云杉遗传研究，并且不同标记系统合并资料能提供更可靠的信息。 Southwestern region plays an important role in economic developmentand ecological construction in China. Yet, it is also one of the weak regionsof ecological environment in China with degraded ecosystem and imperfectfunction, which restricts the sustaining management and development ofsouthwestern forestry. The genetic variation and spatial distribution patternof P. asperata populations originating from different habitats wereinvestigated using SSR molecular markers in this study. The correlationsbetween genetic variation and ecological and environmental conditionswere detected, and the interaction between P. asperata populations andenvironmental system and the mechanism of ecological adaption -molecular evolution were revealed. Given the significant ecological andeconomic roles of the fast-growing and wide-adaptive species in reforestation and production of pulp wood and timber, the study couldprovide a strong theoretical evidence and scientific direction for thesustaining management of subalpine natural forest, and the afforestationand rehabilitation of degraded ecosystem. The results are as follows: 1. The genetic variation at SSR loci was abundant and the distributionof allelic frequencies was uneven. All seven loci were polymorphic, and thenumber of alleles per locus varied from 13 to 24 with a mean valueequaling 19.9. The allele sizes at SSR loci were found to vary widely.73.1% of allelic variation followed stepwise mutation model (SSM) whichresults increase or decrease by one repeat type, and 22.3% and 4.6% wereresulted from two-phase mutation model (TMP) with allele size varying bymore than one repeat type and from insertion-deletion events in theflanking regions at SSR loci with a single basepair changing, respectively. 2. P. asperata possessed a moderate to high level of genetic diversityand considerable genetic differentiation. Microsatellite variation of P.asperata. originating from the mountains of southwestern China wasinvestigated by analyzing variation at seven SSR loci in 250 individualsrepresenting ten populations. A fair degree of genetic diversity and strongpopulation subdivision occurred with the mean gene diversity (H) of 0.707,and genetic distances among populations varying between 0.121 and 0.224(FST) and between 0.100 and 0.537 (RST). However, inter-populationgenetic distances showed no correlation with geographic distances between the population sites. This ruled out a simple isolation by distance modeland suggested that migration does not have a great impact. In fact, theamount of gene flow, detected using private alleles, was very low, equalingonly 0.753. Allele permutation tests revealed that stepwise-like mutations,coupled with genetic drift, could contribute to population differentiation.Moreover, significant genetic differences between populations weredetected at most loci. The results indicate that natural selection, presumablythrough environmental stress, may be one of the main factors causingmicro-geographical differentiation in the genetic structure of P. asperata.Based on SSR genotypes, 70% of the 250 individuals were correctlyclassified into their sites of origin. This suggests that microsatellites (SSRs) are effective in distinguishing genotypes of P. asperata originating fromdiverse eco-geographical sites in China. 3. Using a set of 247 individuals from ten P. asperata populations wereport an overview on the genetic relationship among the sampled P.asperata populations. RAPD, AFLP and SSR were used in terms of theirinformativeness and applicability for evaluate relationship and all threetechniques discriminated the genotypes very effectively. Mean Dicesimilarities coefficient were estimated using RAPD, AFLP and SSR,respectively. The Mantel test resulted in a significant but relatively low fit(RAPD = 0.63, AFLP = 0.60 and SSR = 0.75) of cophenetic values.Comparing the three marker systems to each other, RAPD and AFLP cophenetic indices were highly correlated (r = 0.59), while correlationcoefficient between RAPD and SSR was r = 0.53 and between SSR andAFLP was r = 0.35. For all markers a relatively high similarity indendrogram topologies was obtained although some differences wereobserved. All the dendrograms, including that obtained by the combineduse of all the marker data, reflect some relationships for most of thepopulations according to their geographic conditions. The results indicatethat single or combined marker system could be used to insight into geneticstudy in P. asperata and the combined data of different marker systems canprovide more reliable information.

Degradation of porphyran from Porphyra haitanensis and the antioxidant activities of the degraded porphyrans with different molecular weight

In the present paper, ascorbate and hydrogen peroxide (H2O2) were used to degrade porphyran. It was found that porphyran could be degraded by free radical that was generated by ascorbate and H2O2 in combination. It was possible to prepare desired porphyran products with different molecular weight by adjusting ascorbate to H,02 proportions and their concentrations. The molar ratio of I was demonstrated more effective than in other ratios. Higher concentrations accelerated the degradation. Moreover, results of chemical analysis and FT-IR spectra suggested that the main structure of degraded products still remained although some changes happened. The degraded and natural porphyrans possessed scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH)-radical activity and reducing power. Higher antioxidant activities were found in both systems when the molecular weight was reduced. The results indicated that the antioxidant activities were closely related to the molecular weight. The degraded porphyrans are potential antioxidant in vitro. (c) 2006 Elsevier B.V. All rights reserved.

The effect of land management on plant community composition, species diversity, and productivity of alpine Kobersia steppe meadow

Grassland degradation is widespread and severe on the Tibet Plateau. To explore management approaches for sustainable development of degraded and restored ecosystems, we studied the effect of land degradation on species composition, species diversity, and vegetation productivity, and examined the relative influence of various rehabilitation practices (two seeding treatments and a non-seeded natural recovery treatment) on community structure and vegetation productivity in early secondary succession. The results showed: (1) All sedge and grass species of the natural steppe meadow had disappeared from the severely degraded land. The above-ground and root biomass of severely degraded land were only 38 and 14.7%, respectively, of those of the control. So, the original ecosystem has been dramatically altered by land degradation on alpine steppe meadow. (2) Seeding measures may promote above-ground biomass, particularly grass biomass, and ground cover. Except for the grasses seeded, however, other grass and sedge species did not occur after seeding treatments in the sixth year of seeding. Establishment of grasses during natural recovery treatment progressed slowly compared with during seeding treatments. Many annual forbs invaded and established during the 6 years of natural recovery. In addition, there was greater diversity after natural recovery treatment than after seeding treatments. (3) The above-ground biomass after seeding treatment and natural recovery treatment were 114 and 55%, respectively, of that of the control. No significant differences in root biomass occurred among the natural recovery and seeded treatments. Root biomass after rehabilitation treatment was 23-31% that of the control.

Salt-assisted acid hydrolysis of chitosan to oligomers under microwave irradiation

The effect of inorganic salts such as sodium chloride on the hydrolysis of chitosan in a microwave field was investigated. While it is known that microwave heating is a convenient way to obtain a wide range of products of different molecular weights only by changing the reaction time and/or the radiation power, the addition of some inorganic salts was shown to effectively accelerate the degradation of chitosan under microwave irradiation. The molecular weight of the degraded chitosan obtained by microwave irradiation was considerably lower than that obtained by traditional heating. Moreover, the molecular weight of degraded chitosan obtained by microwave irradiation assisted under the conditions of added salt was considerably lower than that obtained by microwave irradiation without added salt. Furthermore, the effect of ionic strength of the added salts was not linked with the change of molecular weight. FTIR spectral analyses demonstrated that a significantly shorter time was required to obtain a satisfactory molecular weight by the microwave irradiation-assisted inorganic salt method than by microwave irradiation without inorganic salts and conventional technology. (C) 2005 Elsevier Ltd. All rights reserved.

Extension of life span and improvement of vitality of Drosophila melanogaster by long-term supplementation with different molecular weight polysaccharides from Porphyra haitanensis

Polysaccharides isolated from Porphyra (porphyran) have been known to have diverse biological activities, including immunomodulatory and antioxidant activities. The molecular weight-antiaging activity relationship of degraded porphyrans was examined in this study. Natural porphyran was extracted from P. haitanensis, and then was degraded into different molecular weight fractions, P1 molecular weight 49 kDa, P2 molecular weight 30 kDa, P3 molecular weight 8.2 kDa, by free radical. The influence on life span and vitality of porphyrans were carried out on Drosophila melanogaster. We found that all the degraded porphyrans and natural porphyran (P), added daily to the diet, can significantly increase the life span of D. melanogaster, except for P3. Among them, P1 exhibited the most prolonging life span activity. Furthermore, vitality of middle-aged flies (assessed by measuring their mating capacity) receiving porphyrans was increased considerably in comparison with the controls. Finally, in the heat-stress test, we observed a remarkable increase in survival time, especially in P3-diet groups. These results suggest that porphyrans may be effective in reducing the rate of the aging process and molecular weight has important influence on the effects. It seems that P1 and P2, possessed higher molecular weight, may be more useful in normal metabolic condition and P3, possessed the lowest molecular weight, may be more beneficial for D. melanogaster in stress condition. (C) 2007 Elsevier Ltd. All rights reserved.

浑善达克退化生态系统恢复研究

　　浑善达克沙地是我国四大沙地之一，地处北方干旱半干旱区，为草原区向荒漠区过渡的地带。长期以来，由于人类不合理的生产活动，加上这里脆弱的生态环境，已引起了严重的土地退化问题：流动沙丘面积由1950s年占沙地总面积的2%增加到1990s的近50%。因此浑善达克沙地成为我国研究土地退化、防治沙尘暴的重点地区，本文从自然科学和人文科学相结合的角度出发，对浑善达克沙地草地退化原因、自然恢复潜力、恢复过程、适宜物种选择，以及社区生存、生产等方面进行了综合研究，得出以下主要结论： 　　 1) 浑善达克沙地土壤种子库中含有大量的种子，在退化草地自然恢复中表现出极大的潜力。这些种子在摆脱人和牲畜干扰的前提下，可以萌发、定居并形成植物群落，使退化草地恢复;当地表达到一定程度的植被覆盖，可有效减少沙尘暴的危害。土壤种子库中的植物种类与地上植被有极显著的相似性(P<0.05)，这是地上植被形成稳定群落的基础。种子库中的物种组成影响植被恢复演替的进程;反之，恢复演替也制约着种子库组成和幼苗建立。 　　2)退化沙地草地围封后，对不同恢复阶段草地的群落学调查表明，该地区自然恢复过程大致分为3个阶段：围封2年的恢复早期，流动沙丘向半固定沙丘转变;围封3-5年的恢复中期，半固定沙丘向固定沙丘转变;围封6年后的恢复后期，为固定沙丘稳定发展阶段。根据生活型及植物种类随恢复演替的变化规律，浑善达克沙地植被演替的总体趋势可归纳为：沙米 (Agriophyllum squarrosum)+ 雾冰藜(Bassia dasyphylla)群落→黄柳(Salix gordejevii)+ 冰草(Agropyron cristatum)群落→褐沙蒿(Artemisia intramongolica) + 冰草群落→沙地榆(Ulmus pumila var. sabulosa)疏林+冰草群落。在围封禁牧下，浑善达克退化沙地草地在较短时间内实现自然恢复，因此制约退化草地恢复演替的关键因素主要是人为和牲畜的干扰，只要排除了这种干扰因素，浑善达克大面积的退化沙地草地完全能够借助自然力实现生态恢复。 　　3) 浑善达克沙地3种生境下84种植物叶片渗透势值和含水量，表现出不同功能型上的差异。总体变化趋势为： 深根系 > 浅根系;灌木 > 乔木 > 草本;分布在湿地和丘间低地的植物叶片渗透势和含水量较高，而生长在沙丘上的植物叶片渗透势较低，需要有发达的根系吸收土壤深层的水。不同植物具有独特的水分利用特性，使它们能共存于同一生态系统中。这些不同植物功能型表现出的植物水分生理生态特性，表明浑善达克天然分布的植物群落发育有完善的利用水资源的能力，能够保证在很大降水波动条件下分布有丰富的植物群落和较高的生物生产力，构成该特殊类型生态系统很强的恢复潜力。另外，浑善达克沙地沙丘的存在是该类生态系统恢复弹性较高的另一重要原因。 　　4)本地种与引入种在生理生态上表现出不同的适应能力。在相似的太阳辐射和叶片温度下，引入种旱柳的叶片水势较高，而净光合速率、气孔导度、水分利用效率则较低。这表明它的光合潜能在改变环境中没有正常发挥。同时，引入种较低的最大光化学效率进一步表明它抵抗环境胁迫的能力较低。当土壤水分可利用程度降低而导致水分竞争时，引入种很可能在竞争中被淘汰。因此，在生态恢复中，应尽量避免引入外来种，大量使用本地种。 　　5) 生态恢复不仅是自然科学问题，更重要的是社会经济问题。为了充分认识当地社区的参与对生态恢复的作用，在实验过程中，调查了当地居民自本实验开展以来的思想观念、经济收入和生产效益等变化。在生态恢复中当地社区的积极参与是保证恢复成功与否的关键因素。从发挥“自然力” 和“以人为本”的指导思想出发，在生态恢复中应注重充分利用自然的力量;在管理方面，要以解决社区居民的生产生活实际需求为目标。只有这样，才能保证生态、社会和经济可持续发展。

冷蒿和糙隐子草的竞争策略对冷蒿退化草原恢复过程的影响

有很多因子调控植物群落中哪些物种存在或是哪些缺失，评价这些因子中某些因子的重要性因为因子间潜在的交互作用而变得十分复杂。已经有很多人对内蒙古典型草原生态系统的结构和功能进行了研究，这个系统的植物群落易受多种相互交互的因子影响，其中包括干旱、动物粪尿斑、放牧家畜的采食以及物理干扰等。一些研究认为在大气条件一致的区域内，牧压对群落施加的影响可以超越不同地段其它环境因子的影响，成为控制群落特征的主导因子。因而内蒙古典型草原群落的演替主要是由在一定放牧压力维持下不同植物种群的消长来实现的。但是对于在多个因子相互作用下的内蒙古草原的演替机制并没有得到很好的认识。采食伴随着土壤养分的变化交互到一起影响植物群落的结构动态和组成。本论文采用野外和室内可控试验相结合的方法，选取不同演替阶段的优势物种冷蒿（小半灌木、直根系、C3植物，在重度放牧区占统治地位）和糙隐子草（小丛生禾草、须根系、C4植物，中度放牧区的下层优势钟）为研究对象，对内蒙古草原放牧演替的机制进行了探讨。希望这些信息有助于我们理解内蒙古草原退化的机理，并对内蒙古草原潜在的恢复措施提供一些有意义的建议。 本文提出三个假设：第一，退化草原土壤养分亏缺，因此养分利用率高的物种将占优势，并成为优势物种;第二，在轻度刈割或是不刈割条件下，糙隐子草的竞争能力将加强，施肥也将有利于增加糙隐子草的竞争能力;第三，冷蒿高的竞争能力而不是放牧忍耐力决定冷蒿在过度放牧样地占统治地位。 我们得到的结论如下： 通过三年的恢复，在原过牧区并没有发现很低的氮素养分，恰恰相反，土壤的微生物态氮和土壤无机氮含量较高。冷蒿的养分利用效率较低（以每形成100g碳所需的养分量计算），但在退化草原却是优势物种。因此否定了第一个假设。恢复四年后，糙隐子草在群落中所占的比例仍然很低，恢复过程中糙隐子草并没有成为优势种。同样的，温室内模拟放牧试验的结果与野外数据结果相符。即：同冷蒿相比,糙隐子草在各氮水平和各刈割强度下始终是一个弱的竞争者。在分析竞争能力时，施氮和刈割之间有交互作用。刈割对两物种竞争能力的影响不显著，但随着氮肥水平的提高，在所有刈割强度下，冷蒿对糙隐子草的相对竞争力下降。因此部分支持第二个假设。冷蒿高的种间竞争能力（高的生物量、高的氮产量、高的氮素吸收速率以及高的氮素回收率）决定其在退化草原成为优势种。此外，冷蒿能够成为重牧地段的优势物种可能也归因于其很强的空间拓殖能力、避食机制、干旱的忍耐能力、根系的生态位分异、高的种子生产能力以及可能存在的它感作用。而糙隐子草能够较经济的利用养分和具有较好的放牧抗性是它能与冷蒿在一定的放牧压力下共存的原因。因此，我们的研究结果支持第三个假设。

退耕还林(草)工程对吴起县农村经济发展的驱动力分析

以陕西省吴起县为例,在实地调查的基础上,通过对退耕还林(草)工程实施后农村就业结构变化、基本农田种植结构及种植方式的改变、后续产业的发展与农民收入和农村经济进行相关性分析及灰色关联度分析,结果表明:非农行业就业人数占总人数的比例、农业中间物质消耗以及作为后续产业代表的肉类产量四个驱动因素对农村经济总收入提高的相对贡献率分别为:33.64%,32.17%,34.19%。对农民年收入提高的相对贡献率分别达到了33.30%,33.24%,33.46%。退耕还林(草)工程对农村经济的发展起到了巨大的驱动作用。

农地承载力影响因素及拓展途径分析

在分析农地承载力内涵的基础上,指出农地资源承载力的影响因素众多,概括为自然环境因素和社会经济因素;农地承载力是动态变化的,改变农地所处的条件和影响因素可以拓展其承载力;从系统耦合,开放条件,农地制度,农地结构方面探讨农地承载力的拓展途径。