Effect Of Forest Cover Research Articles

Fruit biomass availability along a forest cover gradient

AbstractHabitat loss is the main driver of the current high rate of species extinction, particularly in tropical forests. Understanding the factors associated with biodiversity loss, such as the extinction of species interactions and ecological functions, is an urgent priority. Here, our aim was to evaluate how landscape‐scale forest cover influences fruit biomass comparing different tree functional groups. We sampled 20 forest fragments located within landscapes with forest cover ranging from 2 to 93 percent in the Atlantic forest of southern Bahia, Brazil. In each fragment, we established five plots of 25 × 4 m and carried out phenological observations on fleshy fruit throughout 1 year on all trees ≥5 cm dbh. We estimated fruit availability by direct counting of all fruits and derived fruit biomass from this count. We used spatial mixed linear models to evaluate the effects of forest cover on species richness, abundance, and fruit biomass. Our results indicated that forest cover was the main explanatory variable and negatively influenced the total richness and abundance of zoochoric and shade‐tolerant but not shade‐intolerant species. A linear model best explained variations in richness and abundance of total and shade‐tolerant species. We also found that forest cover was positively correlated with the fruit biomass produced by all species and by the shade‐tolerant assemblages, with linear models best explaining both relationships. The loss of shade‐tolerant species and the lower fruit production in fragments with lower landscape‐scale forest cover may have implications for the maintenance of frugivore, seed dispersal service, and plant recruitment.

Plantation or natural recovery? Relative contribution of planted and natural pine forests to the maintenance of regional bird diversity along ecological gradients in Southern Europe

Forest plantations are increasingly used as tools to restore local biodiversity. Measures aimed at making plantations more complex and similar to natural forests to preserve biodiversity are still under debate. In this paper, we compare the role of natural and planted Pinus spp. for the maintenance of regional forest bird diversity along large-scale ecological gradients in Southern Europe. We modelled the relative contribution of the extent of either natural or planted pine forests to explain the richness of pine-dwelling forest birds in 3950 sample units (10km×10km cells) in peninsular Spain after controlling for the potential effects of geographical variables, environmental factors, surrounding land-uses, forest cover and vegetation structure within pine forests. Planted pine forests maintained less pine-dwelling forest bird species than did natural pine forests after controlling for confounding variables and structural differences. Such differences may be due to the time lags involved in forest bird community assembly. Regional and local drivers explaining the regional bird species richness varied among pine species, either natural or planted. Management recommendations to increase bird diversity should not be based on just mimicking natural pine forest structure as quickly as possible. Rather, specific practices should be developed locally together with the maintenance of unexploited natural stands for both reference and conservation of the results of the temporal component of community assembly.

Hydrological response of an afforested catchment in a Mediterranean humid mountain area: a comparative study with a natural forest

AbstractThe effects of afforestation on water resources are still controversial. The aim of this paper is to (i) analyse the hydrological response of an afforested area in the Central Pyrenees and (ii) compare the hydrological response of an afforested area with the response observed in a natural undisturbed forest. The Araguás catchment was cultivated until the 1950s, and then afforested with pines in an effort to control the active degradation processes. The hydrological response was variable and complex, because the discharge was generated by a combination of distinct runoff processes. The hydrological response showed that (i) afforestation produced moderate peak discharges, stormflows and recession limbs, and long rising limbs; (ii) no one single variable was able to explain the hydrological response: rainfall volume and intensity did not explain the hydrological response and antecedent rainfall and initial discharge (indicating antecedent moisture conditions) did play an important role; (iii) seasonal differences were observed suggesting different runoff generating processes; and (iv) the effect of forest cover on peak discharges became less important as the size of the hydrological event increased. The stormflow coefficient showed a clear seasonal pattern with an alternation between a wet period, when the catchment was hydrologically responsive, and a dry summer period when the catchment rarely responded to any event, and two transitional periods (wetting and drying). Compared with a natural forest, the afforested area recorded greater flows and peak discharges, faster response times and shorter recession limbs. Afforestation reduces the water yield and the number of floods compared with non‐vegetated areas and abandoned lands. Copyright © 2016 John Wiley & Sons, Ltd.

Differential effect of landscape structure on the large-scale dispersal of co-occurring bird-dispersed trees

Seed dispersal enables plants to reach favorable sites for population renewal or expansion far from conspecifics. However, the ability of plants to respond to habitat heterogeneity at large spatial scale is strongly mediated by seed dispersal vectors, e.g. animals, which usually restrict seed deposition to sites with specific environmental conditions, and at short distances from source plants. This spatial constraint, together with the technical difficulties of following the movement of seeds in the wild, makes the estimation of plant response to large-scale heterogeneity a challenge. Here, we applied an isotope-based technique to track bird-mediated seed dispersal of two co-occurring tree species in eight replicated landscapes in the Cantabrian Range (N Spain): the hawthorn Crataegus monogyna and the holly Ilex aquifolium. These species bear very similar fruits, partially overlap in the timing of fruit production, and their seeds are dispersed by the same species of frugivorous birds. Thus we expected that landscape structure, as represented by the amount of forest cover in the landscape, would affect the large-scale seed dispersal of neighboring individuals of C. monogyna and I. aquifolium in a similar fashion. Contrary to our expectation though, the effects of forest cover on the dispersal patterns of co-occurring hawthorn and holly were opposite: high forest cover in the landscape decreased large-scale dispersal for hawthorn, but enhanced it for holly. Our results suggest that small differences in the traits of plant and frugivore species, such as phenology patterns, can interact with the distribution of adult plants to generate strong differences in the response to landscape structure through seed dispersal, even for neighboring trees belonging to different species.

Which landscape size best predicts the influence of forest cover on restoration success? A global meta‐analysis on the scale of effect

Summary Landscape context is a strong predictor of species persistence, abundance and distribution, yet its influence on the success of ecological restoration remains unclear. Thus, a primary question arises: which landscape size best predicts the effects of forest cover on restoration success? To answer this question, we conducted a global meta‐analysis for biodiversity (mammals, birds, invertebrates, herpetofauna and plants) and measures of vegetation structure (cover, density, height, biomass and litter). Response ratios were calculated for comparisons between reference (e.g. old‐growth forest) and disturbed sites (degraded or restored). Using an information‐theoretic approach, mean response ratio (restoration success) and response ratio variance (restoration predictability) within each study landscape were regressed against the percentage of overall (summed forest cover) and contiguous (summed pixels of ≥60% forest cover) forest within eight different buffer sizes of radius 5–200 km (at 1‐km resolution). We included 247 studies encompassing 196 study landscapes and 4360 quantitative comparisons. The best buffer (landscape) size varied for the following: (i) overall and contiguous forest cover, (ii) biodiversity and vegetation structure and (iii) mean response ratio and response ratio variance. Only plant biodiversity was influenced by overall forest cover (buffer size of 5, 10 and 200 km radii), while plants (10 and 200 km radii), mammals (5, 10 and 50–200 km radii), invertebrates (5 and 10 km radii), cover (5 km radii), height (5 km radii) and litter (100 km radii) were influenced by contiguous forest cover. Overall, mean response ratio and response ratio variance were positively and negatively nonlinearly related with both overall and contiguous forest cover, respectively. We reveal for the first time a clear pattern of increasing restoration success and decreasing uncertainty as contiguous forest cover increases. We also indicate preliminary recommended buffer sizes for investigating landscape restoration effects on biodiversity and vegetation structure. However, the coarse grain and variability in the data mean the optimal landscape size may not have been detected; thus, further research is needed. Synthesis and applications. When setting targets for ecological restoration, policymakers and restoration practitioners should account for the following: (i) the landscape context, particularly the amount of contiguous habitat up to 10 km around a disturbed site, and (ii) the uncertainty in restoration success, as it increases when contiguous forest cover falls below about 50%.

An Effective Method for Snow-Cover Mapping of Dense Coniferous Forests in the Upper Heihe River Basin Using Landsat Operational Land Imager Data

The Normalized Difference Snow Index (NDSI) is an effective index for snow-cover mapping at large scales, but in forested regions the identification accuracy for snow using the NDSI is low because of forest cover effects. In this study, typical evergreen coniferous forest zones on Qilian Mountain in the Upper Heihe River Basin (UHRB) were chosen as example regions. By analyzing the spectral signature of snow-covered and snow-free evergreen coniferous forests with Landsat Operational Land Imager (OLI) data, a novel spectral band ratio using near-infrared (NIR) and shortwave infrared (SWIR) bands, defined as (ρnir − ρswir)/(ρnir + ρswir), is proposed. Our research shows that this band ratio, named the normalized difference forest snow index (NDFSI), can be used to effectively distinguish snow-covered evergreen coniferous forests from snow-free evergreen coniferous forests in UHRB.

Contrasting Soil Thermal Regimes in the Forest-Tundra Transition Near Nadym, West Siberia, Russia

Permafrost and varying land surface properties greatly complicate modelling of the thermal response of Arctic soils to climate change. The forest-tundra transition near Nadym in west Siberia provides an excellent study area in which to examine the contrasting thermal properties of soils in a forested ecosystem without permafrost and peatlands with permafrost. We investigated the effects of forest shading, snow cover and variable organic soil horizons in three common ecosystems of the forest-tundra transition zone. Based on the year-round temperature profile data, the most informative annual parameters were: (1) the sum of positive average daily temperatures at depths of 10 and 20 cm; (2) the maximum penetration depth of temperatures above 10 °C; and (3) the number of days with temperatures below 0 °C at a depth of 20 cm. The insulative effect of snow cover in winter was at least twice that of the shading and cooling effect of vegetation in summer. In areas with shallow permafrost, the presence of a thick organic horizon, with an extremely low thermal diffusivity, creates a very steep temperature gradient that limits heat penetration to the top of the permafrost in summer. Copyright © 2015 John Wiley & Sons, Ltd.

Geochemistry of organic-rich river waters in Amazonia: Insights on weathering processes of intertropical cratonic terrain

In this study, eight organic-rich rivers that flow through the Brazilian craton in the southwestern Amazon rainforest are investigated. This investigation is the first of its type in this area and focuses on the effects of lithology, long-term weathering, thick soils, forest cover and hydrological period on the dissolved load compositions in rivers draining cratonic terrain. The major dissolved ion concentrations, alkalinity (TAlk), SiO2, trace element concentrations, and Sr isotope contents in the water were determined between April 2009 and January 2010. In addition, the isotopic values of oxygen and hydrogen were determined between 2011 and 2013. Overall, the river water is highly dilute and dominated by the major dissolved elements TAlk, SiO2 and K+ and the major dissolved trace elements Al, Fe, Ba, Mn, P, Zn and Sr, which exhibit large temporal and spatial variability and are closely correlated with the silicatic bedrock and hydrology. Additionally, rainwater and recycled water vapor and the size of the basin contribute to the geochemistry of the waters. The total weathering flux estimated from our results is 2–4 t km−2.yr−1, which is one of the lowest fluxes in the world. The CO2 consumption rate is approximately 21–61 103 mol km−2 yr−1, which is higher than expected given the stability of the felsic to basic igneous and metamorphic to siliciclastic basement rocks and the thick tropical soil cover. Thus, weathering of the cratonic terrain under intertropical humid conditions is still an important consumer of CO2.

Forest fragmentation in the Argentine Chaco: recruitment and population patterns of dominant tree species

The forest in the Central Argentine Chaco has been dramatically fragmented and persists only as isolated patches in an agricultural matrix. In this study, we evaluated the effects of fragmentation on total density, recruitment, and size-class structure of its dominant tree species, a key issue, although little explored, for forest conservation in the region. We particularly analyzed the effects of fragment size and forest cover at landscape level on seven of the most important tree species of the forest. Our results suggest that forest cover at landscape level is more important than fragment size to explain the population patterns of the main tree species. Fragment size was relevant in only one species, Cordia americana, whereas forest cover resulted relevant in five species. The size-class structure of Schinopsis balansae, one of the dominant species of the upper stratum, appeared to be affected in landscapes with less forest cover, showing lower densities of the smaller classes. Our results show that for the conservation of the forest it would be important to increase their protection degree against the expansion of agriculture, attempting to preserve as much of the forest as possible, to promote the forest cover at landscape level and give relevance even to the smallest fragments.

Diurnal Human Activity and Introduced Species Affect Occurrence of Carnivores in a Human-Dominated Landscape.

Diurnal human activity and domestic dogs in agro-forestry mosaics should theoretically modify the diurnal habitat use patterns of native carnivores, with these effects being scale-dependent. We combined intensive camera trapping data with Bayesian occurrence probability models to evaluate both diurnal and nocturnal patterns of space use by carnivores in a mosaic of land-use types in southern Chile. A total of eight carnivores species were recorded, including human-introduced dogs. During the day the most frequently detected species were the culpeo fox and the cougar. Conversely, during the night, the kodkod and chilla fox were the most detected species. The best supported models showed that native carnivores responded differently to landscape attributes and dogs depending on both the time of day as well as the spatial scale of landscape attributes. The positive effect of native forest cover at 250m and 500 m radius buffers was stronger during the night for the Darwin's fox and cougar. Road density at 250m scale negatively affected the diurnal occurrence of Darwin´s fox, whereas at 500m scale roads had a stronger negative effect on the diurnal occurrence of Darwin´s foxes and cougars. A positive effect of road density on dog occurrence was evidenced during both night and day. Patch size had a positive effect on cougar occurrence during night whereas it affected negatively the occurrence of culpeo foxes and skunks during day. Dog occurrence had a negative effect on Darwin's fox occurrence during day-time and night-time, whereas its negative effect on the occurrence of cougar was evidenced only during day-time. Carnivore occurrences were not influenced by the proximity to a conservation area. Our results provided support for the hypothesis that diurnal changes to carnivore occurrence were associated with human and dog activity. Landscape planning in our study area should be focused in reducing both the levels of diurnal human activity in native forest remnants and the dispersion rates of dogs into these habitats.

Turnover in bee species composition and functional trait distributions between seasons in a tropical agricultural landscape

A comprehensive understanding of how spatial variation across landscapes regulates local abundances and species richness also needs to consider possible temporal changes in such relationships. In many tropical areas, the contrast between dry and rainy season is pronounced and the types and distributions of the main floral resources differ (herbs vs trees). This shift in resources could result in different pollinator abundances, species richness and trait compositions between seasons, as well as in how these components are spatially distributed. We compared the bee species composition between dry and rainy season in an agricultural mosaic landscape in southwestern Ethiopia, and analyzed it in relation to forest cover. We sampled bees for 67 days in the dry season and 86 days in the rainy season with pan and vane traps in 28 homegardens covering a gradient from low to high tree cover in the surrounding area. We found a clear shift in species composition between seasons, with more small bee species and more below-ground nesting bees in the rainy season compared to the dry season. The distribution of height at which the bees were foraging shifted between seasons with a higher proportion of the bees foraging at tree level in the dry season. Bee abundance and richness were generally positively affected by higher forest cover surrounding the homegardens, but there were no clear interaction effects between seasons, in contrast to our hypothesis. The clear turnover in species composition between seasons and the positive effect of forest cover show that mechanisms acting both at spatial and temporal scales are important in regulating local bee communities.

Seed dispersal limitations shift over time in tropical forest restoration.

Past studies have shown that tropical forest regeneration on degraded farmlands is initially limited by lack of seed dispersal, but few studies have tracked changes in abundance and composition of seed rain past the first few years after land abandonment. We measured seed rain for 12 months in 10 6-9-year-old restoration sites and five mature, reference forests in southern Costa Rica in order to learn (1) if seed rain limitation persists past the first few years of regeneration; (2) how restoration treatments influence seed community structure and composition; and (3) whether seed rain limitation is contingent on landscape context. Each restoration site contained three 0.25-ha treatment plots: (1) a naturally regenerating control, (2) tree islands, and (3) a mixed-species tree plantation. Sites spanned a deforestation gradient with 9-89% forest area within 500 m around the treatment plots. Contrary to previous studies, we found that tree seeds were abundant and ubiquitous across all treatment plots (585.1 ± 142.0 seeds · m(-2) · yr(-1) [mean ± SE]), indicating that lack of seed rain ceased to limit forest regeneration within the first decade of recovery. Pioneer trees and shrubs comprised the vast majority of seeds, but compositional differences between restoration sites and reference forests were driven by rarer, large-seeded species. Large, animal-dispersed tree seeds were more abundant in tree islands (4.6 ± 2.9 seeds · m(-2) · yr(-1)) and plantations (5.8 ± 3.0 seeds · m(-2) · yr(-1)) than control plots (0.2 ± 0.1 seeds · m(-2) · yr(-1)), contributing to greater tree species richness in actively restored plots. Planted tree species accounted for < 1% of seeds. We found little evidence for landscape forest cover effects on seed rain, consistent with previous studies. We conclude that seed rain limitation shifted from an initial, complete lack of tree seeds to a specific limitation on large-seeded, mature forest species over the first decade. Although total seed abundance was equal among restoration treatments, tree plantations and tree islands continued to diversify seed rain communities compared to naturally regenerating controls. Compositional differences between regenerating plots and mature forests suggest that large-seeded tree species are appropriate candidates for enrichment planting.

Disentangling habitat use by frugivorous birds: Constant interactive effects of forest cover and fruit availability

Frugivorous animals contribute to forest regeneration, but the provision of this ecosystem service is spatially filtered by the environmental factors limiting frugivore habitat use. Understanding how this filter acts in real-world landscapes is crucial for better predicting how habitat degradation impacts on seed dispersal services. Fruits and forest cover are main determinants of habitat use by frugivorous birds. The degree of spatial segregation between these habitat features would be expected to determine a trade-off for frugivores between finding food and being safe. Nevertheless, little is known about how such a trade-off may finally affect frugivore habitat use. We studied frugivorous bird habitat use in a landscape representing a gradient of forest loss and fragmentation in the Cantabrian Range (N Spain). For four years we evaluated the spatial patterns of the abundances of frugivorous birds, fruits, and forest cover. Both fruits and forest cover influenced bird habitat use in each year. However, we also found a consistent across-years interaction between the effects of forest cover and fruits. In each study year fruit tracking by frugivores increased in landscape sectors presenting sparce forest cover and vice versa, but that intense search for food or shelter weakened in those areas with dense forest cover and abundant fruits respectively. The simultaneous consideration of the different environmental factors limiting frugivore habitat use revealed long-term, complex landscape effects, which are expected to cascade into fine-grained variability of the spatial patterns of seed rain.

Differential barrier and corridor effects of power lines, roads and rivers on moose (Alces alces) movements

Building new power lines is required to satisfy increasing demands for the transmission of electricity, and at the same time the road network is expanding. To provide guidelines for the routing of new power lines and roads, it is essential to test whether linear features deter or attract movements of animals in different landscape settings. Using GPS relocation data from 151 moose (Alces alces L.) in central Norway, we tested for barrier and corridor effects of roads, power lines and rivers and accounted for forest cover, the topographical orientation of linear features and the placement of other nearby linear features. We predicted step selection probabilities for different movement options at varying distances from linear features and linear feature combinations. Barrier and corridor effects of linear features altered moose movements, although effects were minor compared to the effects of topography and forest cover. Moose did not avoid crossing power lines, unless the placement of power lines along contour lines impeded movements across them. In contrast, moose avoided crossing of roads and rivers in forests. Moose more likely moved along linear features when getting closer to linear features. Barrier and corridor effects were higher for road/river combinations compared to single linear features. Likewise, the barrier and corridor effects were higher for road/power line combinations, but not power line/river combinations compared to single linear features, when moose were close to the edge of those features. The inconsistent pattern could be due to the low sample size. We found indications of higher disturbance potential of roads compared to power lines and rivers. Managing vegetation in power line rights‐of‐way to provide abundant browse could counteract possible disturbance, while wildlife overpasses could mitigate road fragmentation effects.

Mathematical model analyses on the effects of global temperature and forest cover on seasonal rainfalls: A Northern Thailand case study

Summary In this work, an empirical mathematical model representing the relationship between global temperature, forest cover and seasonal rainfalls is constructed and validated using global temperature data for the years 1973–2010, Northern Thailand’s forest area data for 1973–2008, and seasonal rainfall data for 1973–2011. The coefficient correlations of the model and the corresponding data are 0.8902, 0.9739 and 0.9751 respectively. Although there are some approximations and assumptions made throughout the analyses, statistical tests confirm that the proposed model can be used to predict the amount of rainfalls in the region. A case study on how government reforestation policy affects seasonal rainfalls is analyzed using the model modified to a solvable form. Three possible scenarios are created to predict possible outcomes of said policy. The results obtained show that under all scenarios, rainfalls increase in all seasons. Moreover, forest cover increase leads to more rainfall in the summer yet results in less rainfall in the other two seasons. The model can be modified and applied to predict rainfalls in other regions with similar topography and the climate after some statistical tests.

Are Forest Attitudes Shaped by the Extent and Characteristics of Forests in the Local Landscape?

Forest policy is increasingly accounting for public attitudes and preferences. However, attitudes vary across the population and are linked to the characteristics of individuals and their relationship to forests. This study examines whether the extent, ownership, and composition of forests in respondents’ localities influence their expressed attitudes and rankings of forest outputs from a household survey. Forest cover in a 5-km buffer surrounding respondents was identified using a geographic information system (GIS) and the effects of forest cover and other key respondent variables were tested using ordered logit models. The results suggest that forest cover does influence attitudes and that the nature of the effects differs based on composition and ownership. A division in attitudes was also identified between members of farming households and urban areas. In addition to describing the potential formation of attitudes, the results highlight the trade-off between commercial and noncommercial management that may be required to improve attitudes toward forestry.

Stream flow regime of springs in the Mantiqueira Mountain Range region, Minas Gerais State

The stream flow regime of four springs located in the Mantiqueira Mountain Range region (MG) was evaluated and correlated to the respective recharge area, relief characteristics, land cover and physical and hydrologic soil characteristics. The streamflow regime was characterized by monitoring of discharges, calculating the surface runoff and specific discharge and by modeling the discharge over the recession period using the Maillet method. As all recharge areas have similar relief the effect of it on the streamflow was not possible to identify. Analysis included determining the effect of drainage area size, soil characteristics and land cover on the indicators of the streamflow regime. Size of the recharge area had a positive influence on the indicators mean discharge and surface runoff volume and on the regulation of the streamflow regime (springs L4 and L1). The spring under the smallest area of influence provided the worst results for the above mentioned indicators (spring L3). The effect of forest cover (natural and planted), associated with soil characteristics, was evidenced by the indicators surface runoff (in depth) and specific yield, both independent of the recharge area size (springs L4 and L2). The interaction of area size, soil characteristics and forest cover (natural and planted) provided the best results for all indicators of streamflow regime in the springs studied in the Mantiqueira Mountain Range (spring L4).

Forests in a water limited world under climate change

The debate on ecological and climatic benefits of planted forests at the sensitive dry edge of the closed forest belt (i.e. at the ‘xeric limits’) is still unresolved. Forests sequester atmospheric carbon dioxide, accumulate biomass, control water erosion and dust storms, reduce river sedimentation, and mitigate small floods. However, planting trees in areas previously dominated by grassland or cropland can dramatically alter the energy and water balances at multiple scales. The forest/grassland transition zone is especially vulnerable to projected drastic temperature and precipitation shifts and growing extremes due to its high ecohydrological sensitivity. We investigated some of the relevant aspects of the ecological and climatic role of forests and potential impacts of climate change at the dryland margins of the temperate-continental zone using case studies from China, the United States and SE Europe (Hungary). We found that, contrary to popular expectations, the effects of forest cover on regional climate might be limited and the influence of forestation on water resources might be negative. Planted forests generally reduce stream flow and lower groundwater table level because of higher water use than previous land cover types. Increased evaporation potential due to global warming and/or extreme drought events is likely to reduce areas that are appropriate for tree growth and forest establishment. Ecologically conscious forest management and forestation planning should be adjusted to the local, projected hydrologic and climatic conditions, and should also consider non-forest alternative land uses.

Cyanophytes and chlorophytes versus raphidophytes in humic lakes with different catchment basins

The aim of the study was to evaluate the effects of coniferous forest cover in the catchment basin and relative catchment area (catchment area to lake volume ratio) on phytoplankton composition in humic lakes. The study was carried out in 11 small and shallow lakes situated in the West Polesie region (Eastern Poland). The lakes were divided with respect to forest cover in their catchment basins into two groups: high forest cover — HFC (more than 60%) and low forest cover — LFC (less than 60%). The study showed that both, land use in the catchments (proportion of forests) and the relative catchment area determined physicochemical and biological parameters in the lakes. The high relative catchment area affects their high productivity expressed by high chlorophyll a concentration and low water visibility. The lakes of the LFC group had low water colour as well as high concentration of total phosphorus (Ptot), reaction (pH), and conductivity of water and a large number of cyanophytes and chlorophytes. The dominant species, e.g., Planktolyngbya limnetica, Limnothrix planctonica, Planktothrix agardhii, Coenococcus planctonicus, were characteristic of high trophic status. In the lakes of the HFC group, Ptot, pH, conductivity of water and the contribution of cyanophytes and chlorophytes was considerably lower, whereas the water colour and the number of raphidophytes represented by Gonyostomum semen was high. The large number of raphidophytes and the small amount of chlorophytes and cyanophytes in the lakes of the HFC group indicated the lake naturalness.

Scale effects and variability of forest–water yield relationships on the Loess Plateau, China

The relationship between forests and water yield on the Loess Plateau is a concern to forest hydrologists and local governments. Most research indicates that forests reduce runoff but the degree of reduction is different at different sites. Data on precipitation, runoff depth, evapotranspiration and forest cover were collected for 67 watersheds through synthesizing published literature. Results suggest that afforestation on sparsely vegetated catchments reduces runoff and that this effect decreased with increasing forest cover. Annual runoff coefficients fluctuate around 4.1%. Catchment scales influence the relationship between percent forest and runoff coefficient. We believe that afforestation–water yield relationships are variable. Large-scale watersheds may have a relatively high buffering capacity that masks forest cover effects on runoff because of a number of interacting factors. Results from this research will support the implementation of large-scale afforestation programs on the Loess Plateau.