Upper Slope (upper + slope)

Distribution by Scientific Domains

Selected Abstracts

Positive and negative effects of livestock grazing on plant diversity of Mongolian nomadic pasturelands along a slope with soil moisture gradient

Noboru Fujita
Abstract To examine different effects of herbivorous large mammals' grazing pressure on plant diversity along a slope in a Mongolian nomadic pasture, we compared species richness, Simpson's index of diversity, and the total plant coverage of plants between protected pasture from livestock grazing and grazed pasture on the near ridge, upper slope, lower slope, foot slope and valley bottom. The species richness and Simpson's index of diversity decreased and the total coverage increased downwardly with increase in pasture soil moisture along the slope. The species richness of the protected pasture decreased, changed little, and increased on the near ridge and the upper slope, the lower slope and the foot slope, and the valley bottom, respectively. Simpson's index of diversity of the protected pasture decreased compared with the grazed pasture only on the valley bottom. The total coverage became lower in the grazed pasture. As the reason for our results, we discuss positive and negative effects of livestock grazing on the species diversity of plants. The positive effect is shown on the valley bottom, where soil moisture and plant growth becomes high with the total coverage over 100%, due to relaxing indirectly the competitive exclusion among plants due to the grazing of dominant plants. The negative effect is obtained on the near ridge and the upper slope, where the soil moisture and the plant growth are low, because of elimination of some plants from the pasture by direct grazing damage. [source]

Effects of hillslope topography on hydrological responses in a weathered granite mountain, Japan: comparison of the runoff response between the valley-head and the side slope

Masamitsu Fujimoto
Abstract To evaluate the effects of hillslope topography on storm runoff in a weathered granite mountain, discharge rate, soil pore water pressures, and water chemistry were observed on two types of hillslope: a valley-head (a concave hillslope) and a side slope (a planar hillslope). Hydrological responses on the valley-head and side slope reflected their respective topographic characteristics and varied with the rainfall magnitude. During small rainfall events (<35 mm), runoff from the side slope occurred rapidly relative to the valley-head. The valley-head showed little response in storm runoff. As rainfall amounts increased (35,60 mm), the valley-head yielded a higher flow relative to the side slope. For large rainfall events (>60 mm), runoff from both hillslopes increased with rainfall, although that from the valley-head was larger than that from the side slope. The differences in the runoff responses were caused by differences in the roles of lower-slope soils and the convergence of the hillslope. During small rainfall events, the side slope could store little water; in contrast, all rainwater could be stored in the soils at the valley-head hollow. As the amount of rainfall increased, the subsurface saturated area of the valley-head extended from the bottom to the upper portion of the slope, with the contributions of transient groundwater via lateral preferential flowpaths due to the high concentration of subsurface water. Conversely, saturated subsurface flow did not contribute to runoff responses, and the subsurface saturated area at the side slope did not extend to the upper slope for the same storm size. During large rainfall events, expansion of the subsurface saturated area was observed in both hillslopes. Thus, differences in the concentration of subsurface water, reflecting hillslope topography, may create differences in the extension of the subsurface saturated area, as well as variability in runoff responses. Copyright 2007 John Wiley & Sons, Ltd. [source]

Population structure, age and growth of macrourid fish from the upper slope of the Eastern-Central Mediterranean

G. D'Onghia
Hymenocephalus italicus, Nezumia sclerorhynchus and Coelorhynchus coelorhynchus were found in 80, 75 and 69% of trawl hauls carried out between 250 and 750 m on the upper slope of the Ionian Sea. The abundance of H. italicus and N. sclerorhynchus increased with depth while in C. coelorhynchus the highest densities were observed in the uppermost 500 m. In all three grenadiers the average size increased with depth. The populations had a multimodal sizefrequency distribution. In H. italicus adults were generally more represented in the population and the abundance of juveniles varied with seasons. In N. sclerorhynchus and mostly in C. coelorhynchus the bulk of the population was generally made up of small individuals the year round. In N. sclerorhynchus a seasonal pattern was shown in the depth distribution of juveniles. The sex ratio was in favour of females in larger specimens and in each bathymetric stratum. Seasonal growth was detected in the otoliths of the three species. Maximum ages were around 9 years in H. italicus and N. sclerorhynchus; 8 years in C. coelorhynchus. Although some differences have been detected in the population ecology of the three species, they are characterized by a prolonged recruitment during the year, slow growth, longevity and delayed maturity. [source]

Rhythmic diel movements of pandalid shrimps in the western Mediterranean continental shelf and upper slope

J. Aguzzi
Abstract In marine ecosystems, information on diel rhythmic movements of species is of importance to characterize temporal changes in the community structure. In this sense, patterns of bottom trawl catches of the pandalid caridean shrimps Chlorotocus crassicornis, Plesionika gigliolii and Plesionika martia were analysed, as a proxy of the timing and duration of their presence on the seabed, close to the autumn equinox (October) and the summer solstice (June) on the continental shelf (100 m) and the upper slope (400 m). The size structure of catches was also studied for each species to assess the possible occurrence of a modulation of rhythmic movements during ontogeny. Data showed marked diel patterns of catchability on the bottom in association with light intensity cycles in both sampling seasons and depths. Chlorotocus crassicornis on the shelf showed nocturnal peaks in catches. On the slope, Pl. gigliolii showed mainly a higher catchability at dusk and dawn, whereas the catchability of Pl. martia was mainly higher during the day time. Juveniles and adults of Pl. gigliolii and Pl. martia showed ontogenetic differences in their occurrence patterns. This phenomenon is discussed by comparing the reported catchability patterns with those of some prey species that also show rhythmic behaviour in association with the day,night cycle. [source]

Nutrient losses from rain-fed bench terraced cultivation systems in high rainfall areas of the mid-hills of Nepal

G. P. Acharya
Abstract Between the elevations of 1000 and 2000,m in the mid-hills of Nepal, over 12 million people subsist on land-holdings of less than 05,ha. These farmers have limited access to commercial inputs such as fertilisers and are reliant on organic manures for soil fertility maintenance. Participatory research was conducted with farmers on bari land (upper slope rain-fed crop terraces) in the hill community of Landruk (bench terraces 0,5 slope, 3000,3500,mm annual rainfall, which aimed to develop soil and water management interventions that controlled erosion without resulting in high leaching, and so were effective in minimising total nutrient losses. Interventions tested were the control of water movement through diversion of run-on and planting fodder grasses on terrace risers on bench terraces. The interventions were effective in reducing soil loss from the bari land in comparison with existing farmer practices, but no effect was observed on nutrient losses in solution form through runoff and leaching. Losses of NO3 -N in leachate ranged from 173 to 997,kg,ha,1,yr,1, but only 07 to 56,kg,ha,1,yr,1 in runoff. The overall nutrient balance suggests that the system is not sustainable. Fertility is heavily dependent on livestock inputs and if the current trends of declining livestock numbers due to labour constraints continue, further losses in productivity can be expected. However, farmers are interested in interventions that tie ecosystem services with productivity enhancement and farmers' priorities should be used as entry points for promoting interventions that are system compatible and harness niche opportunities. Copyright 2007 John Wiley & Sons, Ltd. [source]

Spatial and temporal variation of fire regimes in a mixed conifer forest landscape, Southern Cascades, California, USA

R. Matthew Beaty
Aim In this study, we evaluated the fire-forest mosaic of a mixed conifer forest landscape by testing the hypothesis that pre-fire suppression fire regime parameters vary with species composition (tree species), and environment (i.e. slope aspect, slope position, elevation). Location Our study was conducted in the 1587 ha Cub Creek Research Natural Area (CCRNA), Lassen National Forest, CA, USA. Methods We quantified the return interval, seasonal occurrence, size, rotation period, and severity of fires using dendroecology. Results Slope aspect, potential soil moisture, forest composition, and fire regime parameters in our study area co-vary. Median composite and point fire return intervals (FRI) were longest on higher, cooler, more mesic, north-facing (NF) slopes covered with white fir (Abies concolor), Douglas fir (Pseudotsuga menziesii),white fir, and red fir (A. magnifica),white fir forests, shortest on the dry, south-facing (SF) slopes covered with ponderosa pine (Pinus ponderosa),white fir forests and intermediate on west-facing slopes dominated by white fir,sugar pine (P. lambertiana),incense cedar (Libocedrus decurrens) forests. The spatial pattern for length of fire rotation (FR) was the same as that for FRI. Fires in CCRNA mixed conifer forests occurred mainly (90%) in the dormant season. Size of burns in CCRNA mixed conifer forests were generally small (mean=106 ha), however, during certain drought years widespread fires burned across fuel breaks and spread throughout the watershed. Fire severity was mainly high on upper slopes, low on lower slopes and moderate and low severity on middle slopes. Patterns of fire severity also varied with slope aspect. Fire frequency decreased dramatically in CCRNA after 1905. Conclusions In CCRNA, fire regime parameters [e.g. FRI, fire extent, FR, fire severity] varied widely with species composition, slope aspect and slope position. There was also temporal variation in fire extent with the most widespread fires occurring during drought years. The important contributions of topography and climate to variation in the fire regime indicates that exogenous factors play a key role in shaping the fire-forest structure mosaic and that the fire-forest structure mosaic is more variable, less predictable and less stable than previously thought. Finally, some characteristics of the fire regime (i.e. fire severity, season of burn) in CCRNA are different than those described for other mixed conifer forests and this suggests that there are geographical differences in mixed conifer fire regimes along the Pacific slope. [source]

Water-Yield Reduction After Afforestation and Related Processes in the Semiarid Liupan Mountains, Northwest China,

Yanhui Wang
Abstract:, The increase of coverage of forest/vegetation is imperative to improve the environment in dry-land areas of China, especially for protecting soil against serious erosion and sandstorms. However, inherent severe water shortages, drought stresses, and increasing water use competition greatly restrict the reforestation. Notably, the water-yield reduction after afforestation generates intense debate about the correct approach to afforestation and forest management in dry-land areas. However, most studies on water-yield reduction of forests have been at catchment scales, and there are few studies of the response of total evapotranspiration (ET) and its partitioning to vegetation structure change. This motivates us to learn the linkage between hydrological processes and vegetation structure in slope ecosystems. Therefore, an ecohydrological study was carried out by measuring the individual items of water balance on sloping plots covered by different vegetation types in the semiarid Liupan Mountains of northwest China. The ratio of precipitation consumed as ET was about 60% for grassland, 93% for shrubs, and >95% for forestland. Thus, the water yield was very low, site-specific, and sensitive to vegetation change. Conversion of grassland to forest decreased the annual water yield from slope by 50-100 mm. In certain periods, the plantations at lower slopes even consumed the runon from upper slopes. Reducing the density of forests and shrubs by thinning was not an efficient approach to minimize water use. Leaf area index was a better indicator than plant density to relate ET to vegetation structure and to evaluate the soil water carrying capacity for vegetation (i.e., the maximum amount of vegetation that can be supported by the available soil water for an extended time). Selecting proper vegetation types and plant species, based on site soil water condition, may be more effective than the forest density regulation to minimize water-yield reduction by vegetation coverage increase and notably by reforestation. Finally, the focuses in future research to improve the forest-water relations in dry-land areas are recommended as follows: vegetation growth dynamics driven by environment especially water conditions, coupling of ecological and hydrological processes, further development of distributed ecohydrological models, quantitative relation of eco-water quota of ecosystems with vegetation structures, multi-scaled evaluation of soil water carrying capacity for vegetation, and the development of widely applicable decision support tools. [source]

The distribution of heath balds in the Great Smoky Mountains, North Carolina and Tennessee

Peter S. White
White (1982). Abstract. We used remote sensing and a geographic information system to model the distribution of evergreen shrub communities, called ,heath balds', in the Great Smoky Mountains, North Carolina and Tennessee, USA. The 421 heath balds averaged 1.8 ha in size and covered 0.3% of the landscape. They reached their greatest importance on upper slopes (92% had relative slope positions > 80), convex topography (82% occurred on sites with a curvature greater than 2.6), and elevations between 1100 and 1600 m (94% of the balds). Although heath balds were found in old-growth watersheds, the two watersheds with the greatest number of balds burned extensively after logging in the early 1900s. Bald occurrence was positively correlated with burned sites, old growth condition, and a highly acidic rock type. Heath balds showed a striking geographic pattern, with 88.1% of the area of this community found in six watersheds comprising only 35.4% of the study area. Despite similar topography, geology, and history, the eleven other watersheds had only 11.9% of the bald area while comprising 64.4% of the study area. Multivariate models showed that this community occurs on only 0.4 to 9.0% of the seemingly appropriate sites. Once established, this shrub community, with its dense evergreen canopy and thick leaf litter, is resistant to tree invasion. Both forest and shrub communities are stable on sites that are seemingly ideal for heath bald occurrence. [source]