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41.
The mangrove-fringed Klang Strait, Malaysia, retains approximately 65 billion penaeid prawn larvae annually prior to their settlement in coastal nursery grounds. This phenomenon appears to be due principally to tidal currents and lateral trapping in mangrove-fringed channels, the wind playing an insignificant role. 相似文献
42.
L. Alpízar Professor H. W. Fassbender Coordinator J. Heuveldop Professor H. Fölster G. Enríquez 《Agroforestry Systems》1986,4(3):175-189
The agroforestry systems of cacao (Theobroma cacao) under laurel (Cordia alliodora) and cacao under poro (Erythrina poeppigiana) were studied at CATIE, Turrialba, Costa Rica. An inventory was taken of the organic matter and nutrients (N, P, K, Ca, and Mg) separating the species into their compartments (leaves, branches, trunks and roots). Studies of the litter and of the mineral soil (0–45 cm) yielded these results:
Patterns of nutrient accumulation are discussed in relation to the characteristics of these agroforestry systems. 相似文献
43.
J. Heuveldop H. W. Fassbender L. Alpízar G. Enríquez H. Fölster 《Agroforestry Systems》1988,6(1-3):37-48
During 7 years (1979–1985) cacao harvests (beans and husks) have been recorded for the agroforestry systems ofTheobroma cacao underCordia alliodora andErythrina poeppigiana shade trees. The mean oven dry cacao yields were 626 and 712 kg.ha−1.a−1 cocoa beans underC. alliodora andE. poeppigiana respectively. Harvests have gradually increased over the years and the plantation has now reached maturity.
Annual extraction of N, P, K, Ca and Mg in fruits, which is relatively small, was calculated on the basis of chemical analyses.
The following average values were found (kg.ha−1.a−1):
At the age of 8 years, theC. alliodora trees have reached 26.7 cm diameter (DBH) and 14.0 m in height. Mean annual growth (from age 5 to 7) is 14.6 m3.ha−1.a−1.
Natural plant residue production has been measured for 4 years (Nov. 1981–Oct. 1985). UnderE. poeppigiana it has reached a value of 8.91 t.ha−1.a−1 and underC. alliodora 7.07 t.ha−1.a−1. The shade trees have contributed 57 and 47% respectively. Transference and decomposition rates are high and important in
the nutrient cycles.
The nutrient content of the litter was analysed and corresponding average yearly transfers were (kg.ha−1.a−1):
For part I see Vol. 4, No. 3, 1986.
Agroforestry Project, CATIE/GTZ (Tropical Agricultural Research and Training Center/Gesselschaft für Technische Zusammenarbeit),
Turrialba, Costa Rica 相似文献
44.
Gin Swen Ham Elise Lahaye Massimiliano Rosso Aurelie Moulins Ellen Hines Paola Tepsich 《水产资源保护:海洋与淡水生态系统》2021,31(8):2257-2277
- Mediterranean fin whales aggregating in the Pelagos Sanctuary in summer to feed are exposed to vessel collision risk, particularly from high-speed ferries.
- This study developed models to predict summer fin whale distribution using a generalized additive model (GAM) and MaxEnt, with the aim of providing a tool to identify potential high whale–ferry collision risk areas along ferry routes within the Pelagos Sanctuary during summertime.
- Models were trained using sightings data collected in the summer months of 2009–2018 on board ferries crossing the central area of the Pelagos Sanctuary. Environmental predictors were bathymetry and mean sea surface chlorophyll concentration of the annual spring bloom period.
- The predictive ability of GAM and MaxEnt was assessed using existing knowledge of summer fin whale distribution in the region. GAM (deviance explained = 20.2%) predictions matched documented distributions more closely than that of MaxEnt, with highest predicted fin whale occurrence in deep offshore waters (>2000 m) encompassing the central north-western and western regions, and in the south-eastern region, consistent with known fin whale habitats within the Pelagos Sanctuary. Inter-annual variability was evident, influencing collision risk areas.
- Collision risk was estimated as a function of the overlap between the predicted probability of fin whale occurrence and ferry density estimated from Automated Identification System data. Ferry routes that cross the northern and eastern regions of the Pelagos Sanctuary presented relatively higher collision risk.
- Areas with changes in risk intensity between the years were temporally and spatially dynamic: some appeared intermittently throughout the study period while others persisted over consecutive years or recurred in different years.
- Due to the vastness of the Pelagos Sanctuary, vessel speed reduction maybe a more practical measure to manage collision risk than re-routing shipping lanes. A combination of Seasonal Management Areas and Dynamic Management Areas approaches could be adopted for high-risk areas.
45.
Modelling the transport of particles in the North Sea with reference to sandeel larvae 总被引:2,自引:0,他引:2
The transport of particles representing sandeel larvae in the North Sea is simulated with a three-dimensional circulation model for the years 1976 to 1990. A great year-to-year variability in drift patterns is demonstrated. The results may explain some of the observed differences in recruitment between the main sandeel areas in the North Sea. In the northern sandeel area it seems that strong year classes are unlikely if the retention due to unfavourable currents is poor, and that a high retention in the summer may favour a good year class. In the southern sandeel area no clear coupling between year class strength and larval drift is found, possibly because the retention always seems large enough for a potentially good year class. For more quantitative use of such models in relation to sandeel recruitment, more biological knowledge is obviously needed on larval vertical distribution and timing of sandeel hatching and settling. 相似文献
46.
J. Sales M. Skřivan M. Englmaierová 《Journal of animal physiology and animal nutrition》2014,98(6):1054-1059
Mathematical modelling of the relationships between mineral inputs and outputs would enable the prediction of mineral requirements of poultry under a wide range of conditions. To establish the feasibility of possible modelling of mineral requirements, the current study aimed to describe the individual mineral concentrations of whole bodies of quail over the life cycle from hatching to 70 days of age. Quail were reared indoors without any restrictions that could limit growth. Sampling of birds (n = 6–18) was carried out at 0, 3, 7, 14, 21, 35, 49 and 70 days after hatching. Freeze‐dried samples of whole bodies (digestive contents removed) were analysed for ash, and macrominerals (calcium, magnesium, phosphorus, potassium, sodium) and microminerals (copper, iron, manganese, nickel, selenium, zinc). Ash concentration followed a curvilinear trend, with a maximum of 101.7 g/kg dry matter at 32.77 days. Individual mineral concentrations, expressed as a proportion of ash, were fluctuating over time, with the most prominent changes at 3 days and again at either 14 or 21 days. Dissimilar patterns in individual mineral concentrations resulted that ratios between minerals followed inconsistent patterns over time. Although mineral contents in absolute quantities can be described through modelling over the entire life cycle of the bird, it can be concluded that variable concentrations of individual minerals could complicate further model development. 相似文献
47.
An Erratum has been published for this article in Aquatic Conservation: Marine and Freshwater Ecosystems 12(2), 2002 577
- 1. This research extends techniques of predictive mapping from their application in terrestrial environments to marine landscapes by investigating the relationship between seagrass and hydrodynamics in Core Sound, North Carolina, USA.
- 2. An empirically derived logistic multiple regression model and a Boolean logic suitability model were used to produce several predictive map products, including: susceptibility of seagrasses to storms, probability of seagrass cover, and suitability of areas for restoration of seagrasses. A visual comparison between these maps and conventional seagrass polygon maps allows for a discussion of ‘field’ versus ‘object’ mapping, and the ramifications for management based on different cartographic techniques.
- 3. The predictive method used here showed that only a small portion (19%) of the seagrass bed in the study area would be expected to have a high probability of seagrass coverage. The majority of the seagrass habitat in the study area was predicted to have less than 50% probability of seagrass cover. In addition, 16% of the nearly 2000 ha of seagrass within the study area were predicted to be highly susceptible to acute storm events. Moreover, using a conservative set of site selection criteria, only 7% of the study area encompassed by seagrass habitat was predicted to have a high probability of successful restoration if injured.
- 4. This method provides for an inexpensive way to scale‐up from high‐resolution data to a coarser scale that is often required for conservation and management.
48.
E. Chakwizira J. M. de Ruiter A. L. Fletcher E. D. Meenken 《Grass and Forage Science》2014,69(1):182-190
Establishing the radiation‐use efficiency (RUE) of forage brassica crops will aid our understanding of their photosynthetic performance. The concept of RUE has been developed for cereals and legumes, but there is limited information for forage brassica crops. Three experiments defining the influence of different sowing dates on ‘Gruner’ kale (Brassica oleracea acephala L.) dry matter production were conducted at Hastings (Hawkes Bay) and Lincoln (Canterbury) in New Zealand between 2002 and 2009. These trials were also evaluated for radiation interception and RUE. Delayed sowing increased RUE in two out of three experiments across sites: from 1·93 g MJ?1 photosynthetically active radiation (PAR) for December‐sown crops to 2·72 g MJ?1 PAR (P < 0·001) for January‐sown crops at Hastings and from 1·50 for September‐sown crops to 2·00 g MJ?1 PAR (P < 0·001) for November‐sown crops at Lincoln. The different sowing dates and years of experimentation provided a range of mean temperatures (from 13 to 16°C) during the vegetative period. Across years and sowing dates, RUE was strongly correlated with mean temperature (R2 = 0·81) and sowing date (R2 = 0·64), but weakly correlated with season length (R2 = 0·11) and dry matter (R2 = 0·002). There was also a strong correlation (R2 = 0·83) between sowing date and mean temperature. The increase in RUE with delayed sowing was therefore mainly attributed to increased mean temperatures. Radiation‐use efficiency increased at about 0·41 g MJ?1 for each 1°C increase from 13 to 16°C. 相似文献
49.
Maxine P. Piggott Samuel C. Banks Ben T. Broadhurst Christopher J. Fulton Mark Lintermans 《水产资源保护:海洋与淡水生态系统》2021,31(1):173-184
- Detecting rare species is often a necessity for conservation and management, yet challenging for many field survey methods. Environmental DNA (eDNA) is a highly promising solution that has been shown to outperform many established survey methods.
- Macquarie perch (Macquaria australasica) is an endangered native species that has declined significantly in range and abundance. Detection of M. australasica was compared with an abundant alien fish species (Oncorhynchus mykiss) using eDNA and three conventional survey methods: gill nets, electrofishing and fyke nets.
- eDNA occupancy estimates for both fish species were compared using four different models to investigate what effect these differences have on false positives and false negatives for the rare and common fish species. These models used unadjusted eDNA detections in water samples, eDNA detections that have been screened using a limit of detection method to remove potential false positives, eDNA data supplemented with a second survey method, or eDNA data augmented with sequencing of positive polymerase chain reaction replicates.
- eDNA surveying as a single detection method was found to be more efficient and sensitive compared with each capture method separately and combined. Occupancy estimates for the common and rare species did not vary significantly between the four site occupancy-detection models, suggesting that supplementary data may not have as much effect on occupancy estimates compared with other approaches such as temporal or spatial sampling.
- We conclude that eDNA outperforms the three established survey methods for both a rare and common freshwater fish species. Although there was no significant effect of augmenting eDNA survey methods with other survey data, additional data may improve confidence in detection, and provide confirmatory evidence for unexpected or new detections of a species.
50.
M. Worth Pugh Gary Pandolfi Thomas Franklin Michael M. Gangloff 《水产资源保护:海洋与淡水生态系统》2021,31(3):494-503
- Freshwater communities are threatened by the conversion of natural landscapes for urban and agricultural purposes. Changes to land use may disrupt stream nutrient and geomorphological processes and reduce water quality, increase sedimentation, and decrease habitat heterogeneity eventually leading to species loss and decreases in ecosystem productivity. Endemic species are frequently at greater risk of habitat-mediated fragmentation and extirpation due to their constrained distributions.
- The Kanawha darter (Etheostoma kanawhae) is an understudied fish endemic to the New River Drainage in North Carolina and Virginia, USA. To investigate the potential effect(s) of land-use change on Kanawha darters, naïve occupancy was modelled using instream habitat characteristics and upstream forest cover.
- Generalized linear models revealed that instream habitat and forest cover are reliable predictors of Kanawha darter site occupancy. Specifically, models demonstrated that occupancy increased in reaches with reduced stream width, velocity, and bedrock substrate but higher concentrations of coarse woody material. Kanawha darter occupancy was also positively associated with the extent of forest cover in upstream catchments.
- Although Kanawha darters are not currently considered imperilled, most populations occurred in isolated reaches separated by large sections of unoccupied habitat. Continuing ex-urban development in riparian zones is likely to be the primary threat to Kanawha darters and other endemic species in this catchment. Resource managers and stakeholders should preserve forest cover in headwaters and occupied tributaries and protect or restore riparian zones along the main-stem South and North Forks of the New River to preserve high-quality habitat and enhance connectivity among isolated Kanawha darter populations.
- As human populations in montane regions continue to grow, there is a need to understand how land-use change affects endemic freshwater species. This study further supports the importance of retaining forest cover as an effective strategy for protecting and restoring populations of endemic fishes in high-gradient streams.