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991.
Stervins Alexis Luis G. García-Montero Ana J. Hernández Antonio García-Abril Jesús Pastor 《Agroforestry Systems》2010,79(3):381-391
In the jaragua-bahoruco-enriquillo biosphere reserve, located on the southern border between the Dominican Republic and Haiti,
there are depressed rural areas with soils with high content in Cadmium and other heavy metals which originate naturally in
the geological substrate. Data from 80 soils and an inventory of 76 plantations (coffee and kidney bean were used) to design
a GIS (geographic information systems) tool which integrated statistical multivariate methods, soil parameters including heavy
metal content into models of land planning, agricultural development, forests and protection of the health of the area’s inhabitants
and the natural environment. This GIS tool is based on raster models of an open source, which use combination and reclassification
operations based on the maps, geostatistical methods (Kriging), statistical analyses external to the GIS, and cartography
of limiting and excluding particular factors for crops (including heavy metal soil content). The GIS tool developed discriminates
extreme situations in sustainable agroforestry planning in contaminated rural areas of the Caribbean, Central America and
other tropical regions. 相似文献
992.
Data on tree biomass are essential for understanding the forest carbon cycle and plant adaptations to the environment. We determined biomass accumulation and allometric relationships in the partitioning of biomass between aboveground woody biomass, leaves and roots in Nothofagus antarctica. We measured above- and belowground biomass of N. antarctica trees across different ages (5–220 years) and crown classes (dominant, codominant, intermediate and suppressed) in three site qualities. The biomass allocation patterns were studied by fitting allometric functions in biomass partitioning between leaves (ML), stem and branches (MS) and roots (MR). These patterns were tested for all pooled data and according to site quality and crown classes. Biomass accumulation varied with crown class and site quality. The root component represented 26–72% of the total biomass depending on age and site. N. antarctica scaling exponents for the relationships MLvs. MS, MAvs. MR, and MSvs. MR were close to those predicted by the allometric biomass partitioning model. However, when biomass allocation was analyzed by site quality the scaling exponents varied following the optimal partitioning theory which states that plants should allocate more biomass to the part of the plant that acquires the most limiting resource. In contrast, the crown class effect on biomass partitioning was almost negligible. In conclusion, to obtain accurate estimations of biomass in N. antarctica trees the allometric approach appears as an useful tool but the site quality should be taken into consideration. 相似文献
993.
Luis Carlos Jovellar Lacambra Alfredo Blanco Andray Fernando Santos Francés 《European Journal of Forest Research》2010,129(1):111-117
This study reports a parametric approach to the climatic and edaphoclimatic potential distribution of the cork oak (Quercus suber L.) in central-western Spain together with an analysis of the influence of the maximum soil water holding capacity (WHC)
on such potential distribution. To these ends, we employed 12 climatic and 2 edaphoclimatic parameters of eco-physiological
influence derived from the current distribution of cork oaks. The climatic and edaphoclimatic parameters elaborated for two
extreme WHC values (50 and 250 mm) are calculated for the whole study area and are mapped by means of a digital elevation
model and a geographic information system. The results point to an important climatic potential area for high soil WHC values
but there is also a remarkable dependence on this latter parameter, mainly in the Duero basin, since the limits of the climatic
potential area are reduced strongly as WHC decreases. We deduce certain other conclusions as regards the importance of this
variable in the potential distribution of species and in forestation and reforestation projects using this species. 相似文献
994.
Martin-Flores M Mercure-McKenzie TM Campoy L Erb HN Ludders JW Gleed RD 《American journal of veterinary research》2010,71(12):1407-1412
995.
996.
997.
Jose Manuel Álvarez-Martínez Jetse J. Stoorvogel Susana Suárez-Seoane Estanislao de Luis Calabuig 《Landscape Ecology》2010,25(9):1385-1404
In this study we developed a methodology aimed at improving the assessment of inter-annual land cover dynamics from hard classified
remotely sensed data in heterogeneous and resilient landscapes. The methodology is implemented for the Spanish Natural Park
of Sierra de Ancares, where human interference during the last century has resulted in the destruction and fragmentation of
the original land cover. We ran supervised classifications, with a maximum likelihood algorithm (Maxlike), on a temporal series
of Landsat images (1991–2005), followed by an uncertainty assessment using fuzzy classifications and confusion indices (CIs).
This allowed us to show how much (and where) of the resulting maps contained a substantial amount of error, distinguishing
data that might be useful to measure land change from data that are not particularly useful when applying a post-classification
comparison methodology. In this way, we can detect true changes not skewed by the effects of uncertainty. Even if patterns
of change were always coherent amongst years, they were more realistic after reducing uncertainty, in spite of a substantial
decrease in the number of available pixels (i.e. unmasked by the method). We then computed land cover dynamics by means of
a model specifically designed to determine the frequency of disturbances (mainly fire events) and the vegetation recovery
time during the study period. Model outputs showed correlated landscape patterns at a broad scale and provided useful results
to explore land cover change from pattern to process. 相似文献
998.
Larval and post‐larval growth,spat production and off‐bottom cultivation of the smooth venus clam Chionista fluctifraga 下载免费PDF全文
Ariaana Castillo‐Durán Francisco Hoyos‐Chairez José A Arreola‐Lizárraga Luis Martínez‐Córdova Jorge Chávez‐Villalba 《Aquaculture Research》2016,47(9):2851-2860
Harvesting practices of the clam Chionista fluctifraga show a decline in commercial size and densities, but no strategies have been developed to maintain clam beds. Aquaculture represents an alternative for preserving this resource. Adult clams from commercial grounds were used as broodstock. Conditioning, induction of spawning, cultivation of larvae, settlement of eyed larvae and nursing of postlarvae were performed in the hatchery for producing spat. Larvae and postlarvae were used to measure increase in shell height and data were fitted to exponential growth models. Spat were placed in floating trays and maintained in off‐bottom cultivation for 9 months. Samples of clams and tissues were collected monthly to measure absolute growth, shell height increase and a condition index. Larvae, postlarvae and juveniles showed exponential growth patterns. Mean shell height increased about 0.030 mm day?1 during larval and post‐larval stages and 0.049 mm day?1 during field cultivation. Pediveligers (height 215 ± 83 μm) entered metamorphosis at days 9–13 after fertilization, and postlarvae reached 3011.7 ± 325.5 μm (height) at day 60. After field cultivation, survival was about 95%; juvenile shell height was 20.6 ± 2.2 mm, and total weight was 5.3 ± 0.7 g. Growth rates were superior to natural conditions and the condition index was high throughout the study. Our results show that spat of C. fluctifraga can be produced in the hatchery, and that field production can be maintained in off‐bottom trays until reaching commercial size. Aquaculture activities for this species need to be established and evaluated. 相似文献
999.
The effect of photoperiod and feeding frequency on larval of the Amazonian ornamental fish Pyrrhulina brevis (Steindachner, 1876) 下载免费PDF全文
Galileu Crovatto Veras Marcos Ferreira Brabo Joel Artur Dias Higo Andrade Abe Zélia Maria Pimentel Nunes Luis David Solis Murgas 《Aquaculture Research》2016,47(3):797-803
This study aimed to evaluate the performance of Pyrrhulina larvae, Pyrrhulina brevis, under different photoperiods and feeding frequencies. A completely randomized design was used, with four replicates in a 5 × 2 factorial, with five photoperiods (6L:18D, 12L:12D, 16L:8D, 20L:4D, 24L:0D) and two feeding frequencies (two or four times a day). Four hundred larvae with an initial length of 4.6 ± 0.09 mm were randomly distributed in 40, 1‐L containers at a density of 10 larvae/L. Feeding was performed with Artemia nauplii in the ratio of 150 Artemia nauplii/larva/feeding. After 15 days, all larvae were euthanized for measurements of length (mm), final weight (mg), survival rate (%) and larvae uniformity in weight an length (%). The data were subjected to analysis of variance and subsequently, in case of significance, a Tukey test was performed to compare means. There was no interaction between photoperiod and feeding frequency on studied variables (P > 0.05). Likewise, there was no influence of feed rate on the same variables (P > 0.05). There was only influence of photoperiod, where the larvae subjected to longest photoperiods (24L:0D and 20L:4D) showed improved weight and length (P < 0.05). Therefore, a photoperiod of 20L:4E, with feeding twice a day is recommended. 相似文献
1000.
Luis Fernando Beux 《Journal Of Applied Aquaculture》2013,25(3):184-199
ABSTRACT The aim of the present study was to evaluate the survival and growth of larvae (L) of pintado, Pseudoplatystoma corruscans, fed different Artemia sp. proportions: 50, 200, 350, 500, 650, 800, and 950 Artemia nauplii per larva per day, in a complete randomized design. Water salinity was 1.7%, and larviculture lasted for a period of 15 days, which was divided into three individual 5-day trials. Larvae were stocked at a density of 15 per liter and kept in the dark. The concentrations of un-ionized ammonia-N and nitrite-N were directly proportional to the increase in prey density (P < 0.05). Regression analysis showed increased survival and growth rates up to 200, 350, and 500 nauplii/L/day, for the first, second, and third trials, respectively. These results indicate that larval food intake is related to ontogenetic development stage. 相似文献