Interception Capacity Research Articles

How to Calculate Stormwater Management and Storage Capacity for Urban Green Space: Multidisciplinary Methods Used in Shanghai City

In order to relieve urban environmental problems due to stormwater runoff, approaches involving the planning of green space for sponge city construction were previously proposed. In this study, water retention characteristics of 168 green spaces are surveyed to develop estimates of stormwater retention in Shanghai City’s center, suburbs and outskirts. Multidisciplinary methods of community investigation, soil tests, artificial rainfall simulation experiments, and simulations in Autodesk storm and sanitary analysis (SSA) and storm water management model (SWMM) are used. The factors affecting the capacity of stormwater management are identified and used to calculate storage estimates. The relationships among rainfall interception capacity (RIC), runoff, soil water storage properties, and vegetative cover are analyzed, which can provide the theoretical foundation for the assessment of the water-holding capacity in urban green spaces. A criterion for the selection of low impact development (LID) techniques for the Shanghai area is developed on the basis of the data from this study.

Large spatial variations in the distributions of and factors affecting forest water retention capacity in China

Abstract The estimation of forest water retention based on observation and experimental data can be used to accurately analyze large variations in the spatial distributions of the water retention capacity across China and explore factors affecting these large spatial variations at different scales. Therefore, we reviewed the relevant peer-reviewed literature to extract water retention parameters and their influencing factors throughout China via a meta-analysis approach. Furthermore, an empirical model and path analysis were used to explore the spatial distributions of and significant factors affecting the canopy interception capacity (CIC), litter maximum water-holding capacity (LWHC), soil water storage capacity (SSC) and forest water retention capacity (WRC) at the national and basin scales. The results showed that the spatial distributions of the CIC and LWHC exhibited opposite trends in China. The average CIC values in the Pearl River Basin (PRB), Southeast Rivers Basin (SERB), Southwest Rivers Basin (SWRB) and Yangtze River Basin (YTRB) were two times higher than those in the Songhua River Basin (SHRB), Liao River Basin (LRB) and Northwest Rivers Basin (NWRB). In addition, the SSC values accounted for approximately 60–85% of the WRC values in the different basins, soil types and forest types. The average SSC values in semi-alfisol and ferralsol were 2.5 times higher than those in semi-hydromorphic soil and pedocal. Moreover, the effects of some factors such as location, terrain and canopy structure on the CIC, LWHC, SSC and WRC values were significant in only certain basins, but these effects were not significant throughout China. The indirect effects of some climatic, location and terrain factors on the CIC, LWHC, SSC and WRC values determined the total effects. These results can contribute to a better understanding of the large spatial variations in WRC and provide a scientific basis for the improvement of the forest water retention function across China.

Alfalfa canopy water interception under low-pressure sprinklers

Canopy water interception is an important factor in water use efficiency analysis and sprinkler-based fertigation technique development. In the present study, alfalfa canopy water interception and its influence factors were assessed under low wind conditions. The canopy interception capacity for three growth stages of alfalfa (S1, early vegetative stage; S2, late vegetative stage; S3, bud stage) were measured under two types of low-pressure spray sprinklers. The dynamics of canopy interception and interception ratio with irrigation depth were also observed. The total irrigation depth for all measurements was around 8 mm. A weight-based canopy interception measurement device was installed outdoors and integrated with a 20-psi sprinkler at 1 m above the canopy. The alfalfa canopy interception first increased rapidly with irrigation depth, but then stabilized and reached canopy interception capacity (Im). The minimum irrigation depths to achieve the Im values were 2 mm, 3 mm, and 4 mm at the S1, S2 and S3 stages, respectively. Im increased significantly across growth stages, and ranged from 0.46 mm to 1.49 mm. Interception ratio decreased gradually as irrigation depth increased. With an approximately 8-mm total irrigation depth, interception ratio ranged from 5.27 % to 17.59 % over all growth stages. Water application rate had no effect on Im, and Im decreased with droplet diameter. Generally, Im was higher and reached more quickly with the R3000 sprinkler compared to the D3000 sprinkler. Fresh weight, plant height, and LAI of alfalfa had significant positive correlations with canopy interception capacity, and a quadratic regression model was developed with using plant height as a factor. This study provides valuable and basic information for irrigation schedules and fertigation in alfalfa cultivation.

Simultaneous removal of phosphate and ammonium nitrogen from agricultural runoff by amending soil in lakeside zone of Karst area, Southern China

The loss of phosphorus(P) and nitrogen from agricultural non-point source(ANPS) is one of the main causes of eutrophication in rivers, lakes and reservoirs in the Karst region, southern China. The lakeside buffer zone has proven to be effective in reducing the input of ANPS pollutants. However, the interception efficiency of natural soil for P and ammonia nitrogen is insufficient to control ANPS pollution. In this study, natural zeolite(NZ), aluminium modified clay(AMC) and lanthanum modified bentonite(LaMB) were used to amend the natural soil collected in the lakeside zone of Kelan Reservoir, Guangxi, China. An experimental study was conducted to examine the dissolved inorganic P(DIP) and ammonia nitrogen removal efficiency and fixation mechanism of three amended soils under simulation conditions. The results showed that natural soil had a high fraction of clay and silt (particle size<20μm; 75.2 %), and had a high removal rate of >95 % for the DIP at the beginning of the experiment. With the intermittent input of farmland drainage, the P removal rate of natural soil from runoff decreased gradually. Compared with the control group, P removal rates of AMC- and LaMB amended soils remained at a high level within 46 days, with means of 93.6 % and 93.9 %. However, NZ amended soil has a weak interception capacity of runoff P pollutant. The chemical sequential extraction showed that AMC increased soil P capacity by forming NaOH-P and NaHCO3-P, while LaMB by forming NaOH-P, NaHCO3-P and Residual-P. In addition, LaMB amended soil can simultaneously remove ammonia from farmland runoff, with the removal rate of 89.3 %. AMC- and LaMB amended soils are proved to be potential and effective technologies for ANPS pollution control. This study provide an important basis for the treatment of ANPS pollutants and the construction of lakeside buffer zone in eutrophic watershed.

Streamflow and Sediment Declines in a Loess Hill and Gully Landform Basin Due to Climate Variability and Anthropogenic Activities

Streamflow and sediment runoff are important indicators for the changes in hydrological processes. In the context of environmental changes, decreases in both streamflow and sediment (especially in the flood season) are often observed in most of the tributaries of the middle Yellow River in China’s Loess Plateau. Understanding the effect of human activities could be useful for the management of soil and water conservation (SWC) and new constructions. In this paper, changes in streamflow and sediment during the flood season (June–September) of the 1966–2017 period in a typical loess hill and gully landform basin were analyzed. Basin-wide rainfall of the flood season decreased nonsignificantly with an average rate of −0.6 mm/flood season for the whole study period by using the trend-free pre-whitening based Mann–Kendall trend test, while the decreasing rate was weakened on the time scale. A remarkable warming trend (1985–1999) and two decreasing trends (1966–1984 and 2000–2017) were observed, and the overall increasing trend could be found in air temperature series with a rate of 0.01 °C/flood season during the study period. Statistical models were developed to describe the rainfall-runoff and rainfall-sediment processes in the pre-impact period (when the hydrological series was stationary). Furthermore, the relative effects of climate variability and human activities on hydrological changes were quantified. Results proved the dominant role of human activities (versus climate variability) on the reductions of both streamflow and sediment load. The relative contribution of human activities to streamflow decrease was 84.6% during the post-impact period 1995–2017, while the contributions were 48.8% and 80.1% for two post-impact periods (1982–1996 and 1997–2017), respectively, to the reduction of sediment load. Besides, the effect of the exclusion of anomalous streamflow or sediment events on change-point detection was also analyzed. It indicated that the anomalous events affect the detection of change points and should be given full consideration in order to decide whether to remove them in the change-point detection. Otherwise, the full series with anomalous samples will completely affect the attribution results of hydrological changes. We also suggest that large-scale SWC measures with different construction quality and operational life could intercept and relieve most floods and high sediment concentration processes, but may amplify the peaks of streamflow and sediment when the interception capacities are exceeded under the condition of extreme rainstorm events.

Liguleless1, a Conserved Gene Regulating Leaf Angle and a Target for Yield Improvement in Wheat.

A major challenge in modern agriculture is to increase crop yield with diminishing agricultural land to feed the fast-growing global population. The erect leaf phenotype is a highly desirable trait that allows for higher planting density and maximizes light interception capacity and thus increases

RETRACTED: Study on the throughfall, stemflow, and interception of two shrubs in the semiarid Loess region of China

Abstract The Loess Plateau, China, has been subject to 40 years of re-vegetation predominantly with the xerophytic shrubs Caragana korshinskii and Hippophae rhamnoides. Throughfall, stemflow, canopy interception, and water storage capacity experiments for the two shrubs were conducted from May to September during the period 2009–2013. The results showed that the throughfall percentages averaged 62.4% and 70.1% of gross rainfall for H. rhamnoides and C. korshinskii, respectively, while stemflow accounted for 2.4% and 6.7% of the gross rainfall for the two shrubs. The rainfall threshold for stemflow generation was 2.46 and 1.06 mm for H. rhamnoides and C. korshinskii, respectively. The wetting front depths for the two shrubs in the area around the stems were deeper than away from the shrubs. The averaged percentages of interception loss in H. rhamnoides and C. korshinskii were 35.2% and 23.2%. Additionally, H. rhamnoides had greater water storage capacity per leaf area for each simulated rainfall intensity (mean, 0.59 mm; range, 0.28–0.88 mm) than C. korshinskii (mean, 0.44 mm; range, 0.26–0.52 mm). Canopy water storage varied temporally with the eight simulated rainfall intensities. For all the tested rainfall intensities, H. rhamnoides could store more water per dry biomass (mean, 0.72 g−1; range, 0.39–1.06 g−1) than C. korshinskii (mean, 0.49 g−1; range, 0.31–0.69 g−1). The present study can inform re-vegetation projects, water budget analyses, and modeling efforts aimed at understanding rainfall water movement within shrub communities in the semiarid Chinese Loess Plateau, China.

Interdependent effects of climate variability and forest cover change on streamflow dynamics: a case study in the Upper Umvoti River Basin, South Africa

Streamflow dynamics are sensitive to both climate variability and land use change. However, estimating their separate and combined effects remains a research challenge. In South Africa, streamflow dynamics are important not only for irrigated agriculture but also for many rural communities that depend on streamflow for domestic water supply. In this paper, we analysed the effects of pine, wattle and eucalyptus plantation cover change vis-a-vis the effects of inter-annual climate variability on streamflow dynamics of the Upper Umvoti River in South Africa from 1994 to 2016. We modelled inter-annual variability in streamflow by precipitation, temperature and plantation cover using the Bayesian inference. We mapped plantation cover from Landsat satellite imagery. We found strong evidence for an interaction between temperature range and plantation cover net change on streamflow. Specifically, the plantation effect weakened under conditions of high-temperature range anomalies. We explain this interaction with a shift in soil water repellency and interception capacity within the plantation area under a changing temperature range, with important implications for the formation of surface runoff. Previous studies have assumed that the effects of climate variability and plantation cover change on streamflow dynamics are independent. Our results call this assumption into question. Hence, climate and land cover interdependencies should be accounted for in future statistical and process-based modelling studies.

Characterizing Maritime Snow Canopy Interception in Forested Mountains

AbstractAir temperature (Tair) plays an important role in determining how a canopy intercepts snow and apart from event size is the single most important micrometeorological variable found to adequately influence interception rates and magnitude. We present results from a 6‐year study on snow‐forest interactions. This data set reveals the central role Tair plays in how a forest intercepts snow and the need to effectively incorporate this within snow process models. Warm temperature events show a higher canopy interception efficiency (CIE) for all sites across the study period, while colder Tair events demonstrated a lower corresponding CIE. Additionally, there is a structural component of the forest itself that plays a role in the ability of canopy to intercept snow. Recognizing the physical vertical structure of a forest as nontrivial, we present a simple canopy interception model that includes a novel three‐dimensional forest metric that captures canopy complexity, Gz, combined with event size and Tair to adequately predict event‐based interception. Low complexity forests decrease interception capacity from the outset, whereas a highly complex or diverse forest increases interception potential and leads to a nonlinear increase in temperature‐based canopy interception due to more surface area able to intercept falling snow. Essentially, forest structure sets the boundary condition of the potential to intercept, while event size and Tair determines the rate or amount of interception. We develop a simple canopy snow interception model from these data and compare modeled output against three commonly used interception models in both a maritime and continental snow climate. Partitioning the relative importance of snow‐forest interactions on canopy interception will help provide the information to accurately model snow‐forest interactions and also aid in our water resources predictive capabilities now and into the future.

The influence of litter crusts on soil properties and hydrological processes in a sandy ecosystem

Abstract. Litter crusts are integral components of the water budget in terrestrial ecosystems, especially in arid areas. This innovative study is designed to quantify the ecohydrological effectiveness of litter crusts in desert ecosystems. We focus on the positive effects of litter crusts on soil water holding capacity and water interception capacity compared with biocrusts. Litter crusts significantly increased soil organic matter compared to biocrusts and bare lands, by 2.4 times and 3.8 times, respectively. Higher organic matter content resulted in increased soil porosity and decreased soil bulk density. Meanwhile, soil organic matter can help to maintain maximum infiltration rates. Litter crusts significantly increased the water infiltration rate under high water supply. Our results suggested that litter crusts significantly improve soil properties, thereby influencing hydrological processes. Litter crusts play an important role in improving hydrological effectiveness and provide a microhabitat conducive to vegetation restoration in dry sandy ecosystems.

Runoff simulation of two typical urban green land types with the Stormwater Management Model (SWMM): sensitivity analysis and calibration of runoff parameters.

The characteristics of surface runoff and the infiltration properties of urban green land are important to determine the effects of runoff reduction by low-impact development (LID) facilities. In this paper, two typical types of urban green land (lawn and shrub) in Shanghai were selected to study the runoff characteristics under eight rainfall events. The sensitivity of the runoff parameters was analyzed, and then, the optimal parameters were determined using the Stormwater Management Model (SWMM). The results showed that the interception and infiltration capacities of shrub were greater than those of lawn. The rainfall intensity and rainfall pattern were the major factors that influenced the interception and infiltration of rainwater. The threshold value that generates runoff varied across the eight rainfall events ranged from 1.6 to 28.5mm for lawn and 4.5 to 32.0mm for shrub. The maximum reduction ratios of runoff and peak flow for shrub were 52 and 57% higher than them for lawn, respectively. The parameters for shrub were more sensitive to runoff and peak flow compared with those for lawn. Under light rainfalls with a short duration, the maximum infiltration rate and depression storage were more sensitive than those under heavy rainfalls with a long duration. Antecedent dry weather period was not found to be a sensitive parameter except for the shrub under light rainfalls. The relative errors of runoff and dynamic mean runoff (60min) for lawn and shrub were within ± 9.5%. The errors of peak flow ranged between - 21 and 16.6%. The dynamic runoff characteristics and the parameters for lawn and shrub determined in this study can provide references for simulating urban runoff and planning LID areas.

Reconciling Canopy Interception Parameterization and Rainfall Forcing Frequency in the Community Land Model for Simulating Evapotranspiration of Rainforests and Oil Palm Plantations in Indonesia

AbstractBy mediating evapotranspiration processes, plant canopies play an important role in the terrestrial water cycle and regional climate. Substantial uncertainties exist in modeling canopy water interception and related hydrological processes due to rainfall forcing frequency selection and varying canopy traits. Here we design a new time interpolation method “zero” to better represent convective‐type precipitation in tropical regions. We also implement and recalibrate plant functional type‐specific interception parameters for rainforests and oil palm plantations, where oil palms express higher water interception capacity than forests, using the Community Land Model (CLM) versions 4.5 and 5.0 with CLM‐Palm embedded. Reconciling the interception scheme with realistic precipitation forcing produces more accurate canopy evaporation and transpiration for both plant functional types, which in turn improves simulated evapotranspiration and energy partitioning when benchmarked against observations from our study sites in Indonesia and an extensive literature review. Regional simulations for Sumatra and Kalimantan show that industrial oil palm plantations have 18–27% higher transpiration and 15–20% higher evapotranspiration than forests on an annual regional average basis across different ages or successional stages, even though the forests experience higher average precipitation according to reanalysis data. Our land‐only modeling results indicate that current oil palm plantations in Sumatra and Kalimantan use 15–20% more water (mean 220 mm or 20 Gt) per year compared to lowland rainforests of the same extent. The extra water use by oil palm reduces soil moisture and runoff that could affect ecosystem services such as productivity of staple crops and availability of drinking water in rural areas.

Phytochrome B enhances plant growth, biomass and grain yield in field-grown maize.

Phytochrome B (phyB) is a photosensory receptor important for the control of plant plasticity and resource partitioning. Whether phyB is required to optimize plant biomass accumulation in agricultural crops exposed to full sunlight is unknown. Here we investigated the impact of mutations in the genes that encode either phyB1 or phyB2 on plant growth and grain yield in field crops of Zea mays sown at contrasting population densities. Plants of maize inbred line France 2 wild type (WT) and the isogenic mutants lacking either phyB1 or phyB2 (phyB1 and phyB2) were cultivated in the field during two seasons. Plants were grown at two densities (9 and 30 plants m-2), irrigated and without restrictions of nutrients. Leaf and stem growth, leaf anatomy, light interception, above-ground biomass accumulation and grain yield were recorded. At high plant density, all the lines showed similar kinetics of biomass accumulation. However, compared with the WT, the phyB1 and phyB2 mutations impaired the ability to enhance plant growth in response to the additional resources available at low plant density. This effect was largely due to a reduced leaf area (fewer cells per leaf), which compromised light interception capacity. Grain yield was reduced in phyB1 plants. Maize plants grown in the field at relatively low densities require phyB1 and phyB2 to sense the light environment and optimize the use of the available resources. In the absence of either of these two light receptors, leaf expansion is compromised, imposing a limitation to the interception of photosynthetic radiation and growth. These observations suggest that genetic variability at the locus encoding phyB could offer a breeding target to improve crop growth capacity in the field.

FLOOD CONTROL STRATEGY IN SAMPANG CITY, EAST JAVA, INDONESIA

Flood always hits Sampang City every year and it causes the transportation disruption in Madura Island.The flood in Sampang City is caused by four main factors: the watershed (DAS) quality, the drainage system, the river capacity, and the tide. The flood control strategies that have been done are: the reduction of flood discharge peakand increasing the river capacity. However,these strategies have not achieved the significant results yet. Thus a new strategy is needed to solve the problem. The result of hydrography analysis shows that the discharge is dominated by the surface runoff, thus it indicates that the quality of DAS is very poor.Further, the land usage in DAS is dominated by the agricultural land such as thefarms and the rice fields. Based on these observations, a new flood control strategy by controllingthe surface runoff on agricultural land is proposed. The strategy isdescribed as the technical activities in the form of utilization of the farmland partition as the temporary storage facilities. To achieve the maximum result, it should be followed by the following activities: a) increasing the capacity of interception and infiltration by the land conservation; b) increasing the capacity of the water reservoir on the land by raising the embankment design from 30 cm to 50 cm; c) shortening the water puddle time by constructing the absorption wells. The result of the hydrological analysis shows that the new strategy is able to reduce the flood discharge peak of 20% to 67%.

Intercepted by lichens

Rainfall interception by vegetation is an underappreciated part of the terrestrial hydrological cycle. Numerical modelling shows that non-vascular plants, such as lichens, substantially increase the interception capacity of the land surface.

Rainfall interception by six urban trees in San Juan, Puerto Rico

Rainfall interception is an important part of the urban hydrological cycle. Understanding is limited about the role of urban trees and other vegetation in the interception process. This study quantified interception losses by six trees in the Caribbean coastal city of San Juan, Puerto Rico, three representing a broadleaf evergreen, and three representing a broadleaf deciduous species. Rainfall was partitioned into throughfall for 13 storms to compare the results between tree types. Total rainfall ranged from 2.9 to 72.4 mm, and storm duration spanned 1 h to several days. Six of the storms analyzed were characterized by maximum hourly intensity rainfall rates categorized as heavy (> 7.6 mm/h). Strong northeasterly winds brought rain in sustained gusts up to 35 km/h. Average interception losses totaled 19.7% for both tree types, 22.7% for the deciduous trees, and 16.7% for the evergreen trees. Throughfall exceeded 90% of total rainfall for each of the six trees on one or more occasions, and heavy intensity storms produced negative interception losses in one individual. The effect of tree type on interception was significant for storms of low and moderate intensity, but not heavy intensity. Differences in interception losses between storms of similar intensity and between the two tree types were influenced by leaf area and wind. Results suggest that individual urban tree canopies function as spatio-temporally dynamic storage reservoirs whose interception capacity can vary as micro-meteorological conditions change. These findings help advance understanding about interception processes in humid tropical urban settings.

Integrated Effects of Land Use and Topography on Streamflow Response to Precipitation in an Agriculture-Forest Dominated Northern Watershed

Based on statistical analysis, baseflow separation and wavelet analysis, this research was carried out in Shibetsu River Watershed (SRW), Eastern Hokkaido, Japan, to investigate the integrated effects of land use and topography on streamflow response to precipitation. The agriculture-dominated sub-watershed (AW) showed coupled flat topography/agriculture characteristics, the forest-dominated sub-watershed (FW) had coupled steep topography/forest characteristics, and the mixed agriculture-forested sub-watershed (AFW) had mixed flat topography/agriculture and steep topography/forest characteristics. Precipitation variability is characterized by 6-months and 1-year periods. Coupled forest land/steep topography of the FW can increase surface runoff due to forest surface soil water repellency and steep slope, and might receive more external water and higher precipitation that resulted in the highest baseflow and total streamflow compared with other sub-watersheds. Coupled forest land/steep topography can cause higher monthly streamflow variability than coupled agricultural land/flat topography. The FW streamflow is characterized by 3–4 months, 6 months, and 1-year periods. The AW streamflow is only characterized by 3–4 months and 6 months periods. Coupled agricultural land/flat topography produced similar magnitude of baseflow during snowmelt season (March–May) and rainfall season (July–September), which resulted in the losing of annual periodicity in AW streamflow. The coupled forest land/steep topography can increase synchronicity in precipitation and streamflow at annual and monthly scales than coupled agricultural land/flat topography, except in 2007 under wet antecedent conditions when pasture land has lower rainfall interception and lower surface soil infiltration capacity. The coupled forest land/steep topography can increase time lags between precipitation and streamflow compared to coupled agricultural land/flat topography.

Rainfall interception capacity of tree species used in urban afforestation

Afforestation is inserted in the urban environment and interferes directly in the surface runoff. In order to quantify the rainfall interception by tree species, an experiment was carried out in the city of Uruacu, Goias, Brazil, with the four most common tree species in the urban afforestation of the region. The species chosen were the Mangifera indica (mango tree), the Caesalpinia peltophoroides (sibipiruna tree), the Pachira aquatica (munguba tree) and the Licania tomentosa (oiti). In order to register precipitation, ten pluviographs were used. They are capable of measuring precipitation over time in terms of duration, volume, and intensity. For events with a mean cumulative precipitation of 16.7 mm, the mean values of interception found in each species were: Mangifera indica - 8.0 mm; Pachira aquatica - 7.4 mm; Licania tomentosa - 7.2 mm; and Caesalpinia peltophoroides - 4.8 mm. The research confirms the importance of studies related to the identification of the species’ individual characteristics that interfere in the rainfall interception capacity and that can consequently contribute to urban drainage actions. In addition, it proves the existence of variations of rainfall interception in relation to rainfall events and during their occurrences and emphasizes the need for a careful definition of the species that will compose the urban afforestation.

The role of silvicultural systems and forest types in preventing soil erosion processes in mountain forests: a methodological approach using cesium-137 measurements

Forests play a key role in providing protection against soil erosion. Particularly, the role of vertical forest structure in increasing rainfall interception capacity is crucial for mitigating raindrop impact and reducing splash and rill erosion. For this reason, studies on the relationships between forest structures, the past management, and the observed rates of soil loss are needed. In the last few decades, importance was given to the use of cesium-137 (137Cs) as radioactive tracer to estimate soil erosion rates. The 137Cs technique is linked to the global fallout of bomb-derived radiocesium which occurred during a period extending from the mid 1950s to the late 1970s. The 137Cs technique, providing long-term retrospective estimates, could be related to forest treatments applied during the last decades in different sites, also considering the tree species composition. This approach could be useful to compare the effect of different canopy cover and biomass on soil erosion rates related to different tree species. In the work proposed here, a study area dominated by pine and beech high forests located in the Aspromonte Mountains (Calabria, Italy) was selected. The measurements, related to forest structural traits, focusing on canopy cover and biomass, and also on management approaches and forest types, are compared with rates of soil erosion provided by 137Cs. The overall results suggest that the minimum values of soil loss are documented in areas with higher canopy cover and biomass evidencing the protective effect provided by forests against soil erosion. Also, techniques based on the use of tracers like 137Cs proved to be helpful to select the best forest management options useful to optimize the protective role of forests, with the aim to reduce erosion processes in a long-term perspective. The experiment indicates that care must be taken when new silviculture treatments are planned. These findings are in agreement with what documented by other authors in similar environments but need further studies to confirm the effectiveness of using 137Cs in different forest ecosystems.

Some climatological factors of pine in the lake toba catchment area

The article deals with climatological factors of Pine at the Lake Toba Catchment Area also called drained basin, Pinus merkusii is a plant endemic in Sumatra. A central population of Pine in North Sumatra is located in the Tapanuli region to south of Lake Toba. Junghuhn discovered the species in the mountains range of Sipirok. He provisionally named the species as Pinus sumatrana. The article presents a detail analysis of approaches to climate factors, considers rainfall, air temperature, humidity, stemflow, throughfall and Interception following calculation of regression to determine relationship between precipitation with stemflow and interception. Stemflow, it is highly significant with significance of difference between correlation coefficients and z normal distribution. Temperature and relative humidity are the important components in the climate. These components influence the evaporation process and rainfall in the catchment. Pinus merkusii has the big crown interception. Stemflow and Interception has an opposite relation. Increasing of interception capacity will decrease stemflow. This type of Pine also has rough bark however significant channels so that, it flows water even during the wet season and caused the stemflow in Pinus merkusii relatively bigger.