江河源区高山嵩草(Kobresia pygmaea)草甸植物和土壤碳、氮储量对覆被变化的响应

以青海省果洛州藏族自治州甘德县青珍乡高山嵩草Kobresia pygmaea草甸轻度退化草地和重度退化草地为研究对象,通过植物地上部分主要功能群（禾草类、杂类草、莎草类）、植物根系和土壤碳、氮浓度及储量动态研究,结果表明：高寒小嵩草草甸轻度退化草地地上部分主要功能群碳、氮浓度和C∶N比值明显高于重度退化草地的浓度。同一草地类型主要功能群比较,碳、氮浓度依次为杂类草>禾草类>莎草类;植物地上部分的碳、氮浓度明显高于地下根系的碳、氮浓度。重度退化草地植物根系碳、氮浓度高于轻度退化草地植物根系碳、氮浓度。重度退化草地土壤总有机碳浓度显著低于轻度退化草地土壤总有机碳浓度,随着土层的加深碳、氮浓度有减少的趋势。江河源区高山嵩草草甸的土壤有机碳、氮储量最大,植物根系碳、氮储量居中,植物地上部分碳、氮储量最小。重度退化草地总有机碳储量（13554.3 g/m2）较轻度退化草地储量（14669.2 g/m2）下降7.60%。其中,0～40cm土壤层碳储量下降4.10%,植物根系碳储量下降59.97%,植物地上部分碳储量下降15.39%;重度退化草地总氮储量（3780.6 g/m2）较轻度退化草地储量（3352.7 g/m2）高12.76%,其中,0～40cm土壤中总氮储量高13.07%,植物根系全氮储量下降5509%,植物地上部分全氮下降16.00%。由于草地退化损失有机碳11149 kg/hm2,而全氮增加4278 kg/hm2。     

闽江河口湿地自然保护区及其周边区域景观自然性评价

闽江河口湿地自然保护区是福建省沿海湿地自然保护区网络中的重要组成部分,通过解译2003年和2013年两个时相的遥感影像,利用RS和GIS空间分析技术计算自然景观特征、生态学干扰和景观破碎化程度3项指标,并在此基础上构建2个层次的景观自然性评价指标体系。同时,运用层次分析法计算各个指标层的权重,定量分析了2003—2013年间研究区域的景观自然性的变化,并进一步探讨了不同距离的环状带对湿地保护区及周边区域景观自然性的影响,对闽江河口湿地保护区及其周边区域景观自然性变化进行分析。结果显示:2003—2013年间,闽江河口湿地自然保护区内景观自然性降低,降幅为9.17%,景观自然性有随着距离自然保护区距离增加而减小的趋势。景观自然性变化的自然驱动力为气候、水文、植被演替,人为驱动力为人类开发活动和政策导向。据此,提出3条建议以便更有效地保护自然保护区和周边区域的自然性,为闽江河口湿地自然保护区的科学管理提供参考。     

中国自然保护区空间分布特征

我国自然保护区经过60余年建设,在维护国家生态安全、保护生物多样性、保存自然遗产和改善生态环境质量等方面发挥着重要作用。研究系统整理了我国现有2672个自然保护区空间分布数据,形成了较为完整的空间信息数据库,从发展历程、保护类型、建设规模等方面进行了特征统计。运用地理集中指数和核密度指数等方法,对全国自然保护区从海陆分布、省级分布、时空分布、集聚分布等不同维度进行了空间分布特征分析。结果表明:(1)我国自然保护区数量和类型丰富,大致经历了"起步-停滞缓慢发展-稳步发展-快速发展-稳固完善"的5个发展阶段,以中小型的森林生态系统、野生动物、内陆湿地和水域生态系统自然保护区为主;(2)空间上为集聚分布,省域分布差异悬殊,沿"胡焕庸线"呈"西少东多、西聚东散"的特点;(3)不同类型和管理级别的自然保护区分布集群态势差异明显,形成了黄山-怀玉山、粤东北丘陵、南岭、武夷山等11个显著聚集区;(4)建设规模和连片聚集效应自西向东呈递减趋势,与我国地形的三级阶梯构造变化趋势存在紧密联系。最后,本文讨论了形成我国现有自然保护区空间格局的主要原因,包括客观自然条件及主观人为等因素,并结合我国自然保护区空间分布和建设发展中存在的问题进行了分析,从建立布局完善和海陆统筹的保护区网络,科学界定保护地类型,逐步优化自然保护区边界及稳步提升科研监测成效等方面提出了发展建议。在我国自然保护地体系由自然保护区向国家公园为主体的全面深化改革阶段,本研究弥补了现有研究成果的局限性和时效性问题,以期为未来自然保护区的空间布局优化及发展提供科学参考。     

川滇高山栎灌丛萌生过程中的营养元素供应动态

萌生更新是森林更新的重要方式, 是硬叶栎林受到干扰后植被恢复的主要机制。以位于青藏高原东南缘的川西折多山东坡川滇高山栎(Quercus aquifoliodes)灌丛为研究对象, 调查分析了砍伐后灌丛萌生过程中基株根系和萌株生物量动态、营养元素含量, 以及基株根系和土壤对萌株生长过程中的营养元素供应动态。结果表明, 川滇高山栎灌丛平均地上和地下生物量分别为(11.25 ± 0.92) t·hm^-2和(34.85 ± 2.02) t·hm^-2, 具有较大的根冠比(3.10:1); 萌生过程中, 萌株生物量呈线性增加趋势, 以灌丛活细根生物量变化为最大, 其次是活中根和活粗根, 树桩和根蔸生物量变化最小; 萌生过程中, 灌丛细根和中根N、P含量表现为先增加、后降低的变化趋势, 萌生初期树桩、粗根和根蔸中N和K的含量明显下降, 根蔸中Ca含量略有下降, 而P没有明显下降, 根系Mg含量变化幅度较大, 灌丛地下根系储存了较多的营养元素; 土壤、树桩、粗根和根蔸是川滇高山栎灌丛砍伐后0-120天萌生生长的主要营养来源, 砍伐后60天, 萌株生长所需的营养除K元素主要来源于根系外, 其余营养元素主要来源于土壤; 在砍伐后60-120天, 基株根系对萌株生长所需的N、K和Ca贡献较大, 而对P和Mg的贡献较小; 在砍伐后120-180天, 根系除K元素对萌生生长还保持较大的贡献外, 对其余营养元素的贡献均较小。高山栎林管理要注重加强地下根系的保护。     

长期围封对疏勒河源区高寒草甸地表节肢动物多样性的影响

围封会促进退化高寒草甸植被和土壤环境恢复,长期围封也会导致生物多样性及其功能下降,影响高寒草甸生态系统的稳定,但这种影响会随着季节和生境条件变化而异。为了探究不同退化程度高寒草甸地表节肢动物群落变化对围封禁牧的响应,利用陷阱法调查了疏勒河源区沼泽化草甸、草甸和草原化草甸3种不同退化梯度高寒草甸围封禁牧和自由放牧处理下地表节肢动物群落结构变化。结果表明：围封禁牧对高寒草甸地表节肢动物群落组成及多样性的影响随生境条件不同而异。禁牧降低了沼泽化草甸地表节肢动物的物种丰富度,而提高了草甸和草原化草甸地表节肢动物的物种丰富度;围封禁牧对沼泽化草甸地表节肢动物群落结构影响较小,显著降低了草甸生境地表节肢动物活动密度、提高了地表节肢动物多样性和均匀度,相反,禁牧显著提高了草原化草甸生境地表节肢动物活动密度、降低其多样性和均匀度;豹蛛属1种是高寒草甸主要的地表节肢动物类群（相对多度为67.0%）,高寒草甸土壤水分有效性等生境条件不同影响了豹蛛属1种对围封禁牧的响应模式,进而影响了地表节肢动物群落结构变化。总之,高寒草甸退化程度影响了地表节肢动物多样性对禁牧和放牧的响应模式,沼泽化草甸适度放牧有利于提高地表节肢动物多样性及其功能。     

Prospects for conserving biodiversity in Amazonian extractive reserves

Non‐timber forest product (NTFP) extraction is a popular alternative to timber extraction that figures prominently in efforts to utilize tropical forests sustainably. But the ability to conserve biodiversity through NTFP management, particularly in extractive reserves in Amazonia, has remained untested. We found that intensive management of Euterpe oleracea (Palmae) fruit, one of the most important extractive products in the Amazon, has substantial impacts on biodiversity, whereas moderate management does not. We mimicked traditional levels of fruit harvest in a replicated experiment over one fruiting season. High‐intensity harvest (75% of fruits removed) reduced avian frugivore species diversity by 22%. Low‐intensity harvest (40% of fruits removed), however, had no effect on diversity. On a larger scale, we found that forests with enriched densities of E. oleracea supported more fruit‐eating birds but fewer non fruit‐eating birds than non‐enriched forests. Taken together, these results suggest that intensive NTFP management to meet market demands may trigger substantial ecological impacts, at least at the level of our study. E. oleracea harvest should be limited where conservation of biodiversity is a goal.     

Marine reserves have rapid and lasting effects

Marine reserves are becoming a popular tool for marine conservation and resource management worldwide. In the past, reserves have been created with little understanding of how they actually affect the areas they are intended to protect. A few recent reviews have evaluated how reserves in general affect the density and biomass of organisms within them, but little work has been done to assess temporal patterns of these impacts. Here we review 112 independent measurements of 80 reserves to show that the higher average values of density, biomass, average organism size, and diversity inside reserves (relative to controls) reach mean levels within a short (1–3 y) period of time and that the values are subsequently consistent across reserves of all ages (up to 40 y). Therefore, biological responses inside marine reserves appear to develop quickly and last through time. This result should facilitate their use in the management of marine resources.     

Size and accumulation of fuel reserves at stopover predict nocturnal restlessness in a migratory bird

Early arrival at the breeding site positively affects the breeding success of migratory birds. During migration, birds spend most of their time at stopovers. Therefore, determining which factors shape stopover duration is essential to our understanding of avian migration. Because the main purpose of stopover is to accumulate fat as fuel for the next flight bout, fuel reserves at arrival and the accumulation of fuel are both expected to affect stopover departure decisions. Here, we determined whether fuel reserves and fuel accumulation predict a bird''s motivation to depart, as quantified by nocturnal migratory restlessness (Zugunruhe), using northern wheatears (Oenanthe oenanthe) that were captured and temporarily contained at spring stopover. We found that fuel reserves at capture were positively correlated with Zugunruhe, and negatively correlated with fuel accumulation. This indicates that fat birds were motivated to depart, whereas lean birds were set on staying and accumulating fuel. Moreover, the change in fuel reserves was positively correlated with the concurrent change in Zugunruhe, providing the first empirical evidence for a direct link between fuel accumulation and Zugunruhe during stopover. Our study indicates that, together with innate rhythms and weather, the size and accumulation of fuel reserves shape stopover duration, and hence overall migration time.     

Factors affecting poly-β-hydroxybutyrate accumulation in cyanobacteria and in purple non-sulfur bacteria

Abstract Spirulina maxima and Rhodopseudomonas palustris , which are known to be capable of synthesizing poly-β-hydroxybutyrate (PHB), were grown under different conditions in order to investigate the metabolic significance of PHB synthesis in phototrophic microorganisms. The intracellular concentration of PHB in S. maxima , growing photoautotrophically in batch cultures under either balanced or unbalanced (depletion of nitrogen or phosphorus in the mineral medium) conditions, was below 0.005% of cell dry weight. PHB was synthesized (up to 0.7% of dry weight) only after a prolonged period of N-starvation (although no PHB synthesis occurred when N-starvation was induced by azaserine addition) or when cells, after the exhaustion of intracellular phosphorus reserves, became P-starved. Under the latter condition, the PHB concentration reached a value of 1.2% of cell dry weight, the same figure reached in the presence of the uncoupler carbonylcyanide- m -chlorophenylhydrazone (CCCP). When photosynthetic activity was enhanced by a sudden shift of the culture to higher light intensity or when S. maxima was grown at 18°C, no PHB synthesis was detectable. Under all the photoautotrophic growth conditions tested, glycogen was much more heavily accumulated than PHB. Batch cultures of R. palustris , growing photoheterotrophically on acetate with varying nitrogen sources and regimens of nitrogen supplementation, demonstrated that some competition for reducing equivalents exists between nitrogenase activity and PHB biosynthetic pathway. The results seem to suggest that, in phototrophic bacteria able to synthesize both PHB and glycogen, the polyester acts mainly as a regulator of the intracellular reduction charge.     

Density dependence and the economic efficacy of marine reserves

Predictions on the efficacy of marine reserves for benefiting fisheries differ in large part due to considerations of models of either intra- or inter-cohort population density regulating fish recruitment. Here, I consider both processes acting on recruitment and show using a bioeconomic model how for many fisheries density dependent recruitment dynamics interact with harvest costs to influence fishery profit with reserves. Reserves consolidate fishing effort, favoring fisheries that can profitably harvest low-density stocks of species where adult density mediates recruitment. Conversely, proportion coastline in reserves that maximizes profit, and relative improvement in profit from reserves over conventional management, decline with increasing harvest costs and the relative importance of intra-cohort density dependence. Reserves never increase profit when harvest cost is high, regardless of density dependent recruitment dynamics. I quantitatively synthesize diverse results in the literature, show disproportionate effects on the economic performance of reserves from considering only inter- or intra-cohort density dependence, and highlight fish population and fishery dynamics predicted to be complementary to reserve management. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.