公海渔业的限制与发展——国际渔业法律环境剖析

本文阐述了公海渔业的概念,论述公海捕鱼自由是国际海洋法中的一条基本规则,指出公海捕鱼的权利必须在国际法规定的有关规则限制下行使。根据近年来一些沿海国家试图对公海渔业进行管辖的实际状况和1992年国际上一些主要的国际渔业会议的主要精神,本文分析了国际渔业法律环境的发展趋向,预测了今后国际上进一步限制公海渔业的可能形式,并结合我国公海渔业发展的实际情况,提出我国发展公海渔业过程中应当给予重视的几个问题。     

Variation in seed rain from Widdringtonia whytei growing in different conditions on Mulanje Mountain in Malawi

Mulanje Mountain is one of the examples of tropical montane landscapes with plant populations varying in size from small fragments of less than 1 ha to riverine strips and stands of more than 100 ha. Seed availability is a potential limiting factor in vegetation recovery in such landscapes. Field observation on seed rain and seed limitation was conducted in 2008 and 2009 in three sizes of forest fragments at three sites on the mountain to investigate: (1) whether size of Widdringtonia whytei forest patches influences seed-rain density; (2) whether W. whytei seed rain occurs in a specific season; and (3) if seed limitation differs from within forest patches to the adjacent non-forest patch habitats. The results showed that there was a distinct difference in seed-rain density among fragments where large fragments (>20 trees) collected higher seed-rain density (10.4 ± 0.9 seeds m^?2 y^?1) than small fragments (1.1 ± 0.4 seeds m^?2 y^?1). The seed-rain density differed significantly between 2008 (2.1 ± 0.6 seeds m^?2 y^?1)and 2009 (6.1 ± 1.1 seeds m^?2 y^?1). Seed rain was recorded every month of the year but the densities were not significantly different among months. Seed-rain density was highest inside the forest fragments (12.04 ± 2.3 seeds m^?2 y^?1) and decreased drastically and very significantly at the edges (1.0 ± 0.8 seed m^?2 y^?1) and outside the forest fragments (0.11 ±0.1 seed m^?2 y^?1). Seed limitation was strong (0.98) on all sites; 0.95 in large fragments and 0.99 in medium and small fragments, respectively. Therefore, it can be concluded from this study that the presence and retention of more seed trees ensures the continued availability of W. whytei seed on the forest floor within the context of limited seed dispersal.     

Plant growth – resource or strategy limited: insights from responses to gibberellin

We used exogenous application of a phytohormone (gibberellin GA₃, ‘GA’) to test the hypothesis that common perennial grasses may not be growing at all times to the limit of resource availability. Plants were taken from the field in winter, and again in summer and their responses to GA assessed under standard conditions, indoors, to reveal their ‘potential’ for growth at different times. Time of year, and associated developmental state, had a major impact on the capacity of plants to respond to exogenous GA, and less so their current growing conditions, temperature and N availability, during measurement. A major increase in dry matter (DM) production in winter‐derived plants took place at both low and high N, with no evidence of a reduction in N content in tissues. That ryegrass plant growth can be stimulated, without externally adding resources, supports the hypothesis there is an element of internal control in how plants respond to ‘signals’ in their environment, that might be manipulated. This offers prospects for reducing environmental impacts (leaching, N₂O) compared with obtaining the same yield increase by adding fertilizer N in early season. Responses to exogenous GA were detected (as significant) but far smaller in summer‐derived plants. Molecular mechanisms of detection of N resource signals, developmental triggers and the role of endogenous gibberellin need to be unravelled to assess scope for breeding ryegrass germplasm to better match demands for increased production with greater resource‐use efficiency.     

外施氯对油菜幼苗生长和光合特征影响的研究

采用盆栽砂培试验,研究了不同浓度氯离子（Cl-）处理对油菜（Brassica napus L.）幼苗干物质积累速率（DMAR）、根冠比（R/S）、叶绿素（Chl）含量、氯离子含量（Cl-）、净光合速率（Pn）、气孔导度（Gs）、细胞间CO2浓度（Ci）、蒸腾速率（Tr）、水分利用效率（WUE）、气孔限制值（Ls）等的影响。结果表明:25～100 mmol/L Cl- 处理9 d和18 d,油菜幼苗植株DMAR均上升,均在50 mmol/L Cl- 处理时达到最大值;不同浓度Cl- 处理9 d,Chl含量有先上升后下降的趋势,在100 mmol/L Cl- 处理时达到最大值,处理18 d,Chl含量依次下降。Cl- 处理能显著提高叶片中的Cl- 含量。除了在处理18 d后的Ci外,25～100 mmol/L Cl- 处理下,油菜叶片均能维持较高的Pn、Gs、Ci和Tr,200 mmol/L Cl- 处理9 d和18 d,油菜叶片Pn、Gs、Ci和Tr均显著下降。随着Cl- 浓度的增加,WUE呈现先降后升,在9 d处理后,随着Cl- 浓度的增加,油菜Ls也呈现先升后降,而在18 d处理后,随着Cl- 浓度的增加,Ls逐渐显著上升。上述结果表明,外施低量氯（Cl- 25~100 mmol/L）显著提高或者维持油菜幼苗的光合作用和蒸腾作用,促进油菜幼苗的生长;而高氯（200 mmol/L Cl-）条件下显著降低其光合作用和蒸腾作用,抑制其生长,且抑制油菜幼苗光合的主要是气孔因素。相关性分析还表明,植株DMAR、Pn、Ci、Tr、Gs之间均有显著的正相关性,而Pn与WUE之间存在极显著的负相关。     

Effects of carbon additions on iron reduction and phosphorus availability in a humid tropical forest soil

In the highly weathered soils of humid tropical forests, iron (Fe) plays a key role in ecosystem biogeochemical cycling through its interactions with carbon (C) and phosphorus (P). We used a laboratory study to explore the role of C quantity and quality in Fe reduction and associated P mobilization in tropical forest soils. Soils were incubated under an ambient atmosphere headspace (room air) with multiple levels of leaf litter leachate or acetate additions. Net Fe reduction occurred in all the treatments and at every time point. The more complex mixture of organic compounds in leaf litter leachate stimulated Fe reduction as much acetate, an easily fermentable C source. At the end of the experiment, Fe reduction was generally greater with higher C additions than in the low C additions and controls. The microbial biomass P had increased significantly suggesting rapid microbial uptake of P liberated from Fe. This occurred without increases in the available (NaHCO₃) P pool. The immobilization of P by microbes during the incubation provides a P conservation mechanism in these soils with fluctuating redox potential, and may ultimately stimulate more C cycling in these highly productive ecosystems. Iron cycling appears to be an important source of P for the biota and can contribute significantly to C oxidation in upland tropical forest soils.     

毛乌素沙地农业生态系统优化模式研究

在分析毛乌素沙地环境背景与系统结构缺陷和功能缺陷的基础上,按照沙地农业生态系统模式优化必须从产业结构调整出发进行系统功能整合的思路,以沙地生态恢复、生态工程、资源高效利用及农业产业互补理论为指导,提出毛乌素沙地农业生态系统功能的有效化,必须协调处理好系统内的农业与畜牧业、农业与林业、农业与能源开发工业等的关系,构建防护型生态结构、节水型种植结构、稳定型畜牧结构和效益型农业产业结构为中心内容的沙地脆弱性农业生态系统优化模式体系.并指出注重系统模式之间互补、协调与整合尤为重要.     

喀纳斯景区山地草甸不同退化阶段群落共有种的生态化学计量特征研究

通过在新疆喀纳斯景区山地草甸群落中对不同退化阶段4个典型样点进行样方调查与采样,结合室内分析,探究了不同退化阶段山地草甸群落共有植物及土壤的碳(C)、氮(N)、磷(P)化学计量特征及其内在联系,揭示了山地草甸生态系统养分循环规律和系统稳定机制。研究结果表明,1) 3种群落共有植物的重要值、盖度、密度和生物量都随着草地的退化加剧而上升,平均高度和叶绿素相对含量随着退化的加剧而降低。2) 随着草地退化程度的增加,群落共有种C、N、P含量均下降,草甸早熟禾C∶N则先降低后升高,其余2种共有种均上升;群落Ⅰ中3种共有植物叶片的N∶P都在14和16之间,剩余3个群落中,草甸早熟禾叶片N∶P高于16,而千叶蓍和短柄苔草叶片的N∶P均小于14。3)叶绿素相对含量与植物的N含量呈显著的正相关,植物盖度与其化学计量比的相关性不显著,植物的高度、密度、生物量与其化学计量比相关性的显著性取决于物种和生境。4)土壤的C、N、P含量均影响植物的C、N、P含量,呈显著的线性正相关。喀纳斯景区未退化阶段的植物生长受N、P双重元素的限制或者均不受限,退化阶段的植物生长主要受N的限制。因此,喀纳斯景区山地草甸土壤生态化学特征对退化山地草甸的植被恢复有着重要影响。     

茶花新品种‘玫玉’耐盐性初探

以2年生茶花新品种‘玫玉’盆栽苗为材料,设置0、50、100、200、400 mmol·L^-1NaCl的盐浓度进行盐胁迫试验,研究盐胁迫对茶花的相对生长量、盐害情况及光合特性的影响。结果表明,随着NaCl浓度的提高,茶花幼苗新梢的生长受到了抑制,且浓度越高,抑制作用越明显,50 mmol·L^-1 NaCl处理后植株的相对生长量与其他3个处理存在显著性差异（p<0.05）;盐害指数和盐害率则随着盐浓度的增加而增加,其中50 mmol·L^-1 NaCl处理的植株在处理28 d后,相对生长量为65%,盐害指数为22.2%,植株生长状况良好,且慢慢适应了低盐环境。茶花的光合速率（P_n）、蒸腾速率（T_r）以及气孔导度（G_s）均随NaCl浓度的提高而降低,并与CK存在显著差异;NaCl胁迫下,气孔限制因素在50 mmol·L^-1 NaCl胁迫时起主导作用,而在100、200、400 mmol·L^-1 NaCl胁迫时,气孔限制因素和非气孔限制因素共同起作用。     

The impact of former agriculture on habitat conditions and distribution patterns of ancient woodland plant species in recent black alder (Alnus glutinosa (L.) Gaertn.) woods in south-western Poland

Little is known about the influence of former agricultural use of soils on the forest recovery process in post-agricultural black alder (Alnus glutinosa) woods – the most fertile and the wettest forest habitats among the European temperate forest types. Thus, studies focusing on edaphic, hydrological and light conditions responsible for colonization mechanisms present in such woodlands adjoining ancient ones were undertaken in south-western Poland. In the 16 m² quadrats of the 33 transects laid out perpendicularly across the ancient-recent forest boundary, data were collected on herb layer composition, chemical soil properties, as well as illumination level. Additionally, groundwater level in the spring months was recorded in piezometers. The number and cover of true woodland herbs were higher in ancient woods, regardless of forest type. Soils in ancient woodlands reached higher levels of Al³⁺, K⁺, cation exchange capacity (CEC), available K, P, and organic C, whereas their pH was lower. The illumination level of the forest floor was greater in recent woods. Linear regression showed that recent wood age had a negative effect on pH and base cations, but positive on Fe²⁺, Ca²⁺, available P and Mg, CEC, and on C and N contents. CCA results showed that woodland age, pH, humus type, groundwater level, available Mg and K were always among those variables having the highest contribution in explaining the distribution pattern of woodland species in recent woods. Total N and available P contents were always higher in ancient woodland soils than in recent, and their content grew with time. Thus, they cannot be treated as indicators of former agricultural use of recent alder wood soils. Urtica dioica, Poa trivialis and Galium aparine, the three competitive herbs, avoided sites with a high level of groundwater, combined with poor illumination level. In order to create the best possible conditions allowing for effective forest recovery in habitats of such high fertility, it is essential to maintain a good water regime and shade in the forest floor. This in turn reduces the competitive exclusion of woodland flora by the aggressive herbs and facilitates the immigration of typical woodland herbs.     

Carbon and Nitrogen Amendments Lead to Differential Growth of Bacterial and Fungal Communities in a High-pH Soil

Microbial growth in soil is mostly limited by lack of carbon (C). However, adding fresh, C-rich litter can induce nitrogen (N) limitation. We studied the effect of alleviating C and N limitation in high-pH (> 8) soils, soils expected to favor bacterial over fungal growth. Nitrogen limitation was induced by incubating soils amended with C-rich substrate (starch or straw) for 4 weeks. Limiting nutrients and the effects of alleviating limitation were then studied by adding C (as glucose) or N (as NH₄NO₃) and measuring microbial growth and respiration after 4 d. In non-amended, C-limited soils, adding C but not N increased both microbial respiration and bacterial growth. In N-limited, substrate-amended soils, adding C increased respiration, whereas adding N increased both microbial respiration and growth. Inducing N limitation by amending with straw was most easily detected in increased fungal growth after the addition of N, whereas with starch, only bacterial growth responded to alleviating N limitation. Compared to earlier results using a low-pH soil, the effect of substrate used to induce N limitation was more important than pH for inducing bacterial or fungal growth after alleviating N limitation. Furthermore, we found no evidence that alleviating N limitation resulted in decreased respiration concomitant with increased microbial growth in soil, suggesting no drastic changes in C use efficiency.