首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   6篇
  免费   0篇
林业   1篇
  1篇
综合类   1篇
水产渔业   1篇
园艺   2篇
  2019年   1篇
  2015年   1篇
  2012年   1篇
  2011年   1篇
  2009年   1篇
  1987年   1篇
排序方式: 共有6条查询结果,搜索用时 15 毫秒
1
1.
The integrated modelling of coupled socio-ecological systems in land-change science requires innovative model concepts capable of grasping the interrelations between socioeconomic and natural components. Here, we discuss the integrated socio-ecological model SERD (Simulation of Ecological Compatibility of Regional Development) that was developed for the municipality of Reichraming in Upper Austria in a participative 2-year process involving local stakeholders. SERD includes three main components: (1) an agent-based actors module that simulates decisions of farmsteads, the municipal administration and other important actors; (2) a spatially explicit (GIS based) land-use module that simulates land-use change at the level of individual parcels of land and (3) an integrated socio-ecological stock-flow module that simulates carbon and nitrogen flows through both socioeconomic and ecological system compartments. We report on outcomes of a scenario analysis that outlines possible future trajectories depending on both external (e.g. agricultural subsidies and prices) and internal (e.g. innovation, willingness to co-operate) factors. We find that both external and internal factors can affect the behaviour of the integrated system considerably. Local and regional policies are found to be able to counteract adverse global socioeconomic conditions to some extent, but not to reverse the trend altogether. We also find strong interdependencies between socioeconomic and ecological components of the system. Fully evaluating these interdependencies is, however, not possible at the local scale alone and will require explicit consideration of higher-level effects in future research.  相似文献   
2.
In primates, certain areas of the frontal cortex play a role in guiding movements toward visual or auditory objects in space. The projections from auditory centers to the frontal cortex of the bat Pteronotus parnellii were examined because echolocating bats utilize auditory cues to guide their movements in space. An area in the frontal cortex receives a direct projection from a division of the auditory thalamus, the suprageniculate nucleus, which in turn receives input from the anterolateral peri-olivary nucleus, an auditory center in the medulla. This pathway to the frontal cortex bypasses the main auditory centers in the midbrain and cortex and could involve as few as four neurons between the cochlea and the frontal cortex. The auditory cortex is also a major source of input to the frontal cortex. This area of the frontal cortex may link the auditory and motor systems by its projections to the superior colliculus.  相似文献   
3.
Nontargeted 400 MHz (13)C and (1)H nuclear magnetic resonance (NMR) spectroscopy was used in the context of food surveillance to reveal Pinus species whose nuts cause taste disturbance following their consumption, the so-called pine nut syndrome (PNS). Using principal component analysis, three groups of pine nuts were distinguished. PNS-causing products were found in only one of the groups, which however also included some normal products. Sensory analysis was still required to confirm PNS, but NMR allowed the sorting of 53% of 57 samples, which belong to the two groups not containing PNS species. Furthermore, soft independent modeling of class analogy was able to classify the samples between the three groups. NMR spectroscopy was judged as suitable for the screening of pine nuts for PNS. This process may be advantageous as a means of importation control that will allow the identification of samples suitable for direct clearance and those that require further sensory analysis.  相似文献   
4.
Context

Varying altitudes and aspects within small distances are typically found in mountainous areas. Such a complex topography complicates the accurate quantification of forest C dynamics at larger scales.

Objectives

We determined the effects of altitude and aspect on forest C cycling in a typical, mountainous catchment in the Northern Limestone Alps.

Methods

Forest C pools and fluxes were measured along two altitudinal gradients (650–900 m a.s.l.) at south-west (SW) and north-east (NE) facing slopes. Net ecosystem production (NEP) was estimated using a biometric approach combining field measurements of aboveground biomass and soil CO2 efflux (SR) with allometric functions, root:shoot ratios and empirical SR modeling.

Results

NEP was higher at the SW facing slope (6.60?±?3.01 t C ha?1  year?1), when compared to the NE facing slope (4.36?±?2.61 t C ha?1 year?1). SR was higher at the SW facing slope too, balancing out any difference in NEP between aspects (NE: 1.30?±?3.23 t C ha?1 year?1, SW: 1.65?±?3.34 t C ha?1 year?1). Soil organic C stocks significantly decreased with altitude. Forest NPP and NEP did not show clear altitudinal trends within the catchment.

Conclusions

Under current climate conditions, altitude and aspect adversely affect C sequestering and releasing processes, resulting in a relatively uniform forest NEP in the catchment. Hence, including detailed climatic and soil conditions, which are driven by altitude and aspect, will unlikely improve forest NEP estimates at the scale of the studied catchment. In a future climate, however, shifts in temperature and precipitation may disproportionally affect forest C cycling at the southward slopes through increased water limitation.

  相似文献   
5.
Abstract – Passive integrated transponder tags have been successfully applied in Cottus spp. and have enabled researchers to gather more information about the movement patterns of individual fish in the wild. In two succeeding years during springtime, a portable antenna was used to determine diel movements of bullhead (Cottus perifretum). In 2007, bullhead (N = 26) moved significantly farther distances at night (mean, 0.42 m·h?1) and dawn (mean, 0.35 m·h?1) than during daytime (mean, 0.11 m·h?1; mixed model, P < 0.001, respectively; P = 0.001), which may be due to foraging activities for Gammarus spp. Irrespective of diel period, smaller fish covered significantly longer distances (P = 0.001). In 2008, similar diel movement patterns were observed, but the differentiation between daytime (mean, 0.12 m·h?1) and night periods (mean, 0.18 m·h?1) was not significant (mixed model, P = 0.087; N = 49 bullhead). It is discussed that longer tracking intervals used in 2008 (three times per 24‐h instead of every two hours) were not suitable to detect the sheer magnitude of distances covered during a diel period. It is shown that this may be due to ‘site fidelity’ of some individuals: after swimming several metres at night, they returned to the exact location they previously occupied during daytime. In 2008, sex and body size were not related to diel movement. The present study is the first to present a quantitative differentiation between diel distances covered in a Cottus spp.  相似文献   
6.
1
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号