南黄海不同粒度表层沉积物中可转化氮与环境因子的关系

南黄海不同粒度表层沉积物中可转化氮的形成与释放受环境因子的驱动作用各不相同,上覆水体的温度、盐度、pH值、DO的含量以及NH4^ 和NO3^-的含量都对其有一定的影响．其中DO是不同形态的氮形成与释放最显著的影响因素,这是因为上覆水体中DO的含量愈高,扩散进入表层沉积物中的O2就愈多,沉积物处于相对氧化的环境中,有机质的矿化作用较易进行,致使无机形态氮的含量相对较高,而有机形态氮的含量相对较低,所以其与可转化有机形态氮呈负相关,而与可转化无机形态氮呈正相关．温度与中、细粒度沉积物中的SOEF-N的含量呈显著正相关,可能是因为温度的升高加快了海洋底栖生物的生长发育,使生物排泄物和死亡残体增多,尽管温度的升高加快了沉积物中有机质的矿化分解,但由于中、细粒度沉积物堆积紧密,对温度的响应不明显,致使SOEF-N的含量随温度的升高而升高．上覆水体中的NH;和NO3^-分别与中、细粒度沉积物中的SAEF-N和SOEF-N的含量呈正相关,说明上覆水体中的NH4^ 和NO3^-主要来自于沉积物中SAEF-N和SOEF-N的形成与释放．另外,粗粒度沉积物中不同形态的氮对环境的响应较中、细粒度沉积物中的强．     

秦岭南部地区农业气候资源的变化及其对油菜的影响

秦岭南部地区地形及气候条件复杂,作为油菜主要种植区之一,研究其农业气候资源的变化特征及其对油菜的影响,可以为该区有效利用农业气候资源、合理安排农事活动提高油菜生产提供实践参考。以1960~2014年秦岭南部33个站点的逐日气象数据和近25a各省市统计年鉴资料,通过滑动平均、线性倾向估计、灰色关联分析等方法,研究秦岭南部农业气候资源的时空变化特征及对油菜产量的影响。结果表明:(1)近55a来,秦岭南部地区油菜生长季内平均气温和≥5℃积温呈上升趋势,平均速率分别为0.2、29.3℃/10 a,冻害指数、降水量、开花期降水量和相对湿度与日照时数都呈减少趋势,平均每10 a分别减少0.3、14.8 mm、1.4 mm、0.6%、32.2 h。(2)近55a来研究区油菜生长季内平均气温与≥5℃积温的多年平均空间分布都表现为由西南向东北方向递减,冻害指数的空间变化与二者相反,表明越冬期极端最低气温值在空间上由西南向东北逐渐减小;其水资源指标多年平均空间分布由南向北递减,日照时数则由西南向东北递增。(3)1960~2014年秦岭南部油菜生长季内平均气温与≥5℃积温在空间上均呈极显著的增加趋势,研究区西部变化幅度较小,东部变化幅度较大,冻害指数的空间变化趋势与二者相同;水资源与日照时数在空间上均呈极显著的减少趋势,只有少数站点表现为极显著的增加趋势,而日照时数在研究区东部变化幅度相对较大,其余区域变化幅度相对较小。总体上,平均气温和≥5℃积温高值区的变化幅度小,低值区变化幅度大,其他指标与之相反。(4)近25a来秦岭南部油菜气候产量呈不明显的上升趋势,平均速率为3.79 kg/(a·hm~2),其空间变化幅度差异大,且大部分站点的变化趋势均不显著;由关联度得作用于各区域油菜气候产量的主要影响因子存在差异。各农业气候资源指标的变化幅度越大,对油菜单产的可能影响相对较大。     

The effects of disturbance based management on the dynamics of Mediterranean vegetation: A hierarchical and spatially explicit modeling approach

The eastern Mediterranean region has been subjected to intensive human disturbance in the past 10,000 years, mainly in the forms of agro-pastoral activities such as grazing, shrub clearing, and prescribed burning. This disturbance history resulted in the formation of highly heterogeneous landscapes, characterized by high biodiversity. Recent changes in human activities have resulted in a decrease of landscape heterogeneity, leading to decreasing biodiversity and increasing fire risk. To conserve heterogeneity, land managers apply disturbance based management practices, using the same activities that created and maintained landscape heterogeneity in the past. However, the long-term and large-scale outcomes of these disturbances are often unknown, due to the complex response of Mediterranean vegetation to disturbance. Here we report on a spatially explicit, hybrid, and spatially hierarchical ecological model developed by us. The model attempts to predict the outcome of various disturbance based management activities on the long-term spatio-temporal dynamics of five common Mediterranean vegetation types. The model uses a spatially explicit state and transition formulation, with continuous transition functions. Model simulations were conducted on a Mediterranean landscape in Northern Israel, incorporating various disturbance practices that are common in the region. Simulation results highlight the potential of disturbance based management as a tool for conserving landscape heterogeneity, as well as the complex interactions between disturbances and the spatial structure of the landscape in Mediterranean regions.     

Zooplankton population model coupled to a biogeochemical model of the North Western Mediterranean Sea ecosystem

A stage structured population (SSP) model based on Fennel's [Fennel, W., 2001. Modelling copepods with links to circulation models. Journal of Plankton Research, 23, 1217–1232] equations is applied to Centropages typicus (Kröyer), a dominant copepod species of the North Western Mediterranean Sea (NWMS) and a prey of small pelagic fish. The model considers five groups of stages and development rates are represented by a mechanistic formulation depending on individual specific growth in each stage. Individual growth is calculated from the individual energy budget depending on food availability and temperature.     

Bridging biogeochemical and food web models for an End-to-End representation of marine ecosystem dynamics: The Venice lagoon case study

The simultaneous accounting of effects of natural and anthropogenic changes within a common framework calls for the development of new comprehensive tools capable of integrating biological processes that span a huge range of scales, from viruses to fishes, in addition to their interactions with physical–chemical environmental properties, i.e. End-to-End models.     

Gas-phase and aerosol chemistry interactions in South Europe and the Mediterranean region

The atmospheric chemical composition is affected by the interaction mechanisms among gases and particulate matter through a wide range of chemical reactions that can occur with the aid of particulate matter (e.g. particles act as reacting or absorbing surfaces) or be influenced by the presence of particulate matter in the atmosphere (photochemical reactions). Physical and chemical processes are also bonded in an interactive way that often leads to the influence of the radiation budget, cloud physics and the warming or cooling of the lower atmospheric levels. The Euro-Mediterranean region is a key-sensitive area due to the unique climatic and air quality characteristics associated with the regional climatic patterns, geomorphology (land and water contrast) and coexistence of pollutants from different origin. Focusing on this region, the gas-aerosol interactions are studied using state-of-the-art atmospheric and chemical transport modeling tools following the necessary development in the chemical transport model CAMx. Sensitivity and large-scale simulations have shown significant responses of the modeling system to the inclusion of natural species emissions, the direct shading effect of dust particles on photochemical processes and the formation of new types of aerosols through heterogeneous uptake of gases on dust particles. Including such interactions in the chemical transport model often led to the improvement of the model performance compared with available measurements in the region.     

Vertical fluxes of aromatic and aliphatic hydrocarbons in the Northwestern Mediterranean Sea

Aliphatic and aromatic hydrocarbon fluxes were measured in time series sediment trap samples at 200 m and at 1000 m depths in the open Northwestern Mediterranean Sea, from December 2000 to July 2002. Averaged fluxes of n-alkanes, UCM and T-PAH₃₅ were 2.96 ± 2.60 μg m⁻² d⁻¹, 64 ± 60 μg m⁻² d⁻¹ and 0.68 ± 0.59 μg m⁻² d⁻¹, respectively. Molecular compositions of both hydrocarbon classes showed a contamination in petrogenic hydrocarbons well above the background levels of such an open site, whereas pyrolytic hydrocarbons stand in the range of other open Mediterranean locations. Fluxes displayed ample interannual and seasonal variabilities, mainly related to mass flux variation while concentration evolutions trigger secondary changes in pollutant fluxes. High lithogenic flux events exported particles with a larger pollutant load than biogenic particles formed during the spring bloom and during the summer. Sinking hydrocarbons were efficiently transported from 200 m to 1000 m.     

Effects of nitrogen deposition and soil fertility on cover and physiology of Cladonia foliacea (Huds.) Willd., a lichen of biological soil crusts from Mediterranean Spain

We are fertilizing a thicket with 0, 10, 20 and 50 kg nitrogen (N) ha⁻¹ yr⁻¹ in central Spain. Here we report changes in cover, pigments, pigment ratios and FvFm of the N-tolerant, terricolous, lichen Cladonia foliacea after 1-2 y adding N in order to study its potential as biomarker of atmospheric pollution. Cover tended to increase. Pigments increased with fertilization independently of the dose supplied but only significantly with soil nitrate as covariate. β-carotene/chlorophylls increased with 20-50 kg N ha⁻¹ yr⁻¹ (over the background) and neoxanthin/chlorophylls also increased with N. (Neoxanthin+lutein)/carotene decreased with N when nitrate and pH seasonalities were used as covariates. FvFm showed a critical load above 40 kg N ha⁻¹ yr⁻¹. Water-stress, iron and copper also explained variables of lichen physiology. We conclude that this tolerant lichen could be used as biomarker and that responses to N are complex in heterogeneous Mediterranean-type landscapes.     

Effects of spatial and temporal scales on cultural services valuation

The monetary valuation of ecosystem services has proved to be a powerful tool for influencing management decisions, as it can be used to quantify the relative importance of various ecosystem functions. However, these valuation methods are rarely implemented with adequate care; in particular, they do not consider spatial and temporal variations in the services offered and demanded. This paper examines the effect of heterogeneity on the valuation of cultural services offered by the Doñana natural protected area in Spain. We apply the zonal travel cost method at various spatial scales, and the individual travel cost method at various temporal scales. We conclude that economic valuation techniques must account for spatial and temporal heterogeneity if they are to provide accurate and realistic information.     

Dynamic emergy evaluation of a fish farm rearing process

The environmental sustainability of a fish farm rearing process was examined by means of emergy analysis. Many emergy analyses integrate data for a whole year smoothing short term variations and sometimes losing meaningful information (aliasing). For this reason we developed a model for an instantaneous emergy evaluation in an aquacultural system so that transformities, efficiency and effort spent at each moment during the fish rearing activity could be calculated. By means of the model and dynamic emergy calculations it is possible to recognize step by step the importance of the various emergy contributions and verify where and when to modify the system to move toward optimum production of a sustainable product. By the application of the model we confirmed that the emergy trends in a fish farm installation follow wide oscillations during a year due to variations in both internal and external emergy contributions. Among the fluxes considered, those due to the introduction of fingerlings represented the highest contributions to the total emergy budget. Thus, to improve the sustainability of the analyzed system the amount, frequency and timing of these fluxes must be carefully considered. For this purpose, a comparison between two different fry introduction schedules was performed to evaluate differences in the efficiency of the rearing process.