Stem Flow Rate Research Articles

Importance of stemflow to soil water replenishment in a montane forest of Popa Mountain Park, Myanmar

Stemflow (SF), rainwater that reach the ground by flowing down along the branches and trunk, is important in maintaining soil water content (SWC) and recharging groundwater in a forest. This study aims to investigate the importance of SF to soil water replenishment in a montane forest. Measurements of gross rainfall, SF at 9 trees, SWC at two different points for two soil depths and infiltration rates at the two points were carried out in Popa Mountain Park (PMP) in 2019. SF rates in PMP were high ranging from 4.0% to 18.8% of total gross rainfall. Mean SWC near the tree were 18.5% at 5 cm depth and 21.7% at 15 cm depth, respectively, while those outside the canopy area were 11.4% and 9.0%, respectively. SWC near the tree were significantly higher for both soil depths. Similarly, significant higher infiltration rate was found near the tree. Near the tree, infiltration rate exceeded the amounts of individual rain events helped to store more rainwater as SWC in deeper soil layers. In PMP, thus, vegetative cover particularly forested areas are expected to have hydrological advantages in restoring rainwater through a large amount of infiltrated SF into the soil.

Importance of forest stand structures for gross rainfall partitioning on China’s Loess Plateau

Large-scale ecological restoration in the arid and semi-arid Loess Plateau region of northern China is challenged by the intensifying water stress due to the changes in precipitation regimes. Although the importance of Gross Precipitation Partitioning (GRP) has been well recognized in forest hydrology, especially in dry areas, the processes are not understood because site- or region-specific factors complicate the accurate quantifications. This study integrates meta-analysis and field observation to compare patterns of GRP in forest stands that had different origins (plantations vs. native forests) and tree species (deciduous vs. evergreen) compositions. We aimed at quantifying the dominant biotic and abiotic factors controlling each of the GRP components to form empirical relationships between the GRP components and the influencing factors via the Boosted Regression Trees (BRT) model. We found a convergence in the GRP components among the examined stands that have diverse tree species and origins. Our results indicated that, unlike stem flow (SF) and canopy interception (Ic), the throughfall (TF) did not differ between natural and plantation stands. Meanwhile, from the perspective of species composition, the broadleaf forest stands had significantly higher SF rates than the coniferous stands. We found that stand structures exerted limited influence on TF, but significantly affected SF and Ic. We hypothesized that the residence time of the GRP components was important in explaining the matrix of influencing factors. The cumulative influences of stand structure factors played a more important role than species in most conditions. Based on the most influential factors (cumulative explanatory power > 70 %) selected from the BRT model, we successfully built a general formula to represent the GRP processes across the diverse forest stands in the Loess Plateau. Our study provides insights into the underlying mechanism of GRP for developing more realistic forest hydrological models. An improved understanding of GRP and better models are important for guiding large scale reforestation efforts that account for hydrological processes across stand species and origins.

Factors influencing maize stemflow in western Liaoning, China

AbstractStemflow (SF) is an important source of water for maize (Zea mays L.) growing in arid areas, and is very important for agricultural water management. However, the results of previous studies in different regions are quite different. There is also a lack of in‐depth research on the SF process of maize at each growth stage. The purpose of this study was to analyze the effects of rainfall characteristics and maize morphology on SF during the entire maize‐growing period, quantify the stemflow rate (SR) in western Liaoning, analyze the differences in the maize SF process during different growing periods, and establish a multiple regression model for the different growth stages to predict SF. The results showed that the SR in the study area was 12.62%–43.44% during the 28 rainfall events from 2015 to 2016, and the mean SR was 32.80%. The mean SR during the jointing, tasseling, and mature stages were 24.10%, 42.72%, and 35.37%, respectively. SF generally increases with increased precipitation, and with an increase in the leaf area index, but the effects of various factors on SF differed between the early (jointing) and later stages (tasseling and maturity) of maize growth. A multiple regression model of the different growth stages was established to better predict SF in the research region. This study is significant as it improves local farmland water cycle theory and improves the efficiency of irrigation water. In the next step, the effects of leaf angle and canopy coverage warrant further investigation.

Effects of fire on interception loss in a coniferous and broadleaved mixed forest

Interception loss is a crucial part of the hydrological cycle and can influence the water and energy balance between the soil surface and atmosphere. Fire alters forest structure and then can immediately modify hydrological factors that influence interception loss. We monitored and simulated canopy rainfall partitioning responses to fire were monitored in a coniferous and broadleaved mixed forest. The results showed that fire had significant impacts on the process of gross rainfall partitioning. Fire enhanced throughfall rate from 71.1% to 77.9%, but reduced interception loss rate from 22.3% to 19.8% and reduced stemflow rate from 6.6% to 2.3%. Our analysis showed that the revised Gash model can accurately predict interception loss and other rainfall fractions in the burned forest. The fire altered the proportions of interception loss components and their sensitivity to model parameters. However, the dominant components of interception loss were still attributed to evaporation from the water-saturated canopy during and after storms. Moreover, the predicted interception loss was still highly sensitive to changes in canopy cover, rain intensity, and evaporation rate. These findings provide useful information for evaluating post-fire changes in forest canopy water budgets and for predicting rainfall partitioning in response to climate change.

Water Demand Pattern and Irrigation Decision-Making Support Model for Drip-Irrigated Tomato Crop in a Solar Greenhouse

The knowledge of crop water requirements is critical for agricultural water conservation, especially for accurate irrigation decision making in the greenhouse. Investigating the water demand pattern of the tomato in the solar greenhouse environment and constructing an appropriate irrigation decision-making model are urgently needed to improve irrigation water use efficiency. We designed four irrigation-level treatments: 100% ET0 (T1), 85% ET0 (T2), 70% ET0 (T3), and 55% ET0 (T4), and conducted a two-vegetation-season tomato planting trial under drip irrigation conditions in a solar greenhouse. The Pearson’s correlation coefficient method analyzed the intrinsic linkage and influence between soil–crop–environment and tomatoes’ water demand patterns. Indicators suitable for irrigation decision making in greenhouse tomatoes were selected, and regression functions were constructed for environmental and crop physiological parameters by combining path analysis and multiple regression methods. Finally, a fusion irrigation decision-making model was constructed by introducing a distance function in the Dempster–Shafer (D–S) theory primary probability assignment (BPA) synthesis algorithm and combining it with a triangular affiliation function. The results showed that: (1) the soil coefficient of variation was shallow > middle > deep, and tomatoes absorbed water mainly in the 0–60 cm soil layer; (2) the crop stem flow rate, net photosynthetic rate, and transpiration rate were positively correlated with irrigation water and had the highest correlation with net radiation, relative humidity, and relative humidity, with correlation coefficients of 0.9441, 0.9441, and 0.7679, respectively; (3) the constructed decision model had a significantly lower value of uncertainty than other methods, while the highest decision value could reach over 0.99, which achieved the best decision accuracy compared to other algorithms.

Satellite-Enabled Internet of Remote Things Network Transmits Field Data from the Most Remote Areas of the Tibetan Plateau.

In this article, we employed a satellite-enabled Internet of Remote Things (IoRT) network as a promising solution to retrieve data in the most remote areas of interest, where public networks are absent. This article presents a system network based on the satellite-enabled IoRT, a new paradigm that defines a network where each environmental monitoring device can autonomously establish a network with a remote data center. The Xingyun satellite constellation was employed for data retrieval on the Tibetan Plateau (TP). The monitoring system was mainly composed of a ground Internet of Things (IoT) terminal that was built with satellite transceivers, environmental monitoring devices, and system software. We deployed five of these newly developed terminals in harsh areas to monitor environmental variables, and accordingly, air temperature and relative humidity, precipitation, snow depth, land surface temperature, tree stemflow rate, and photosynthetically active radiation were retrieved with the satellite-enabled IoRT network. Field experiments were conducted to evaluate the performance of the proposed system network, and the results indicated that the average time delay with and without the packet creation mode reached 32 and 32.7 s, respectively, and the average packet loss rate with and without the packet creation mode reached 5.63% and 4.48%, respectively. The successful implementation of the satellite-enabled IoRT network for the rapid retrieval of monitoring data in remote glacier, forestland, and canyon areas at very high altitudes on the TP provides an entirely new and revolutionary data retrieval means for backhauling data from remote areas of interest.

Canopy interception and water harvesting function of shrubs in urban green spaces of semi-humid region and their influencing factors

In the semi-humid region, developing innovative water conservation urban green space design and facilitating urban greening projects from high water consumption to water conservation are hot topics in research and practice. Using the simulated rainfall method, we explored the water interception and collection functions and their influencing factors of six shrub species (Ligustrum ×vicaryi, Euonymus japonicas, Buxus sinica var. parvifolia, Photinia ×fraseri, Juniperus chinensis and Platycladus orientalis) in urban green space in the semi-humid region. The results showed that canopy interception and water harvesting were two stages in hydrological processes. The canopy interception of coniferous shrubs was high, while their stemflow was low. When the rainfall intensity increased, throughfall rates and stem-flow rates of all shrub species increased significantly, while the interception rate relatively decreased. The throughfall and stem-flow rates of broad-leaved shrubs were significantly higher than those of coniferous shrubs. The canopy interception was significantly lower in broad-leaved shrub species than in coniferous ones. At the center of canopy projection, the throughfall rate was the lowest. The leaf area index (LAI) and throughfall rate decreased gradually from the center of the canopy projection area. When the rainfall intensity was small, the throughfall rate at the center of canopy projection area was low, and thus the interception rate and the stem-flow rate were higher. When the rainfall intensity was more elevated, throughfall at the center of canopy projection area was large, and thus the interception rate and the stem-flow rate were low. With increasing rainfall intensity, the funnel-shaped water collection system tended to shrink due to the increases of throughfall rate at the edge of canopy. Rainfall intensity and LAI were the most critical factors affecting water harvesting function. Planting broad-leaved shrubs under the forest may be more effective in water harvesting than planting coniferous shrubs.

Stemflow infiltration areas into forest soils around American beech (Fagus grandifolia Ehrh.) trees

AbstractThe size of stemflow infiltration areas around the boles of trees is currently a topic of interest and debate within the hydrologic community. There is a gap in our knowledge of stemflow infiltration areas in many wooded ecosystems and a need for more than the few studies that have examined stemflow infiltration areas directly. Hence, this field study was specifically undertaken to mitigate the existing data gap by providing direct measurements of stemflow infiltration areas from high stemflow‐producing American beech (Fagus grandifolia Ehrh.) trees. Different stemflow rates (290, 72 and 31 L h−1) were simulated using dye‐infused stemflow and the areas of stemflow infiltration around four trees determined by measuring the areal extent of dye on the soil surface. Our results revealed that stemflow infiltration areas ranged from 0.0035 to 0.0951 m2 tree−1. The mean basal area funnelling ratio was 46.5 ± 1.8, whereas the funnelling ratios per unit infiltration areas, , were between 32.0 and 258.4. Despite intentionally high stemflow rates, chosen to compensate for the high infiltration capacities of forest soils, these results reinforce the fact that stemflow is an extremely localized input in natural forests. Thus, these results, even if specific to F. grandifolia within a particular forest and soil type, support a growing body of work indicating that stemflow infiltration areas are usually <1 m2, and often much smaller, in natural forests. Moreover, the high values of provide further evidence indicating that stemflow inputs are important for the development of hot spots in near‐trunk soils.

Stemflow generation as influenced by sugarcane canopy development.

Rainfall is generally partitioned into throughfall, stemflow, and interception in ecosystems. Stemflow variability can affect the hydrology, ecology, and soil chemistry patterns. However, the influence of canopy structure and rainfall characteristics on stemflow production in sugarcane plantations which are important for renewable energy production remain poorly understood. By using funnels attached to the sugarcane stems, the present study determined the stemflow amount during the period of sugarcane growth and its relationship with plant development. Approximately, 14% of gross rainfall reached the soil as stemflow, and the funneling ratios was 60. In general, it was observed a positive relationship between stemflow rates with both leaf area index and plant height. This was attributed to an increasing number of acute branching angles of the sugarcane leaves as well as high stem tillering and density. However, at the end of growth cycle, stemflow rate was lower than in previous periods which can be attributed to changes in sugarcane canopy such as stems inclination and lodging, reducing the effectiveness of water conveyance along the stem. Our study showed the need to include stemflow to better understand the hydrology of sugarcane plantations.

Water source and transmission in Haloxylon ammodendron in the desert margin of the Manas River Basin, China

Abstract Analysis of water source and moisture transfer characteristics of desert plants is of great significance for ecological restoration in arid areas. In this study, the water source utilized by the desert plant, Haloxylon ammodendron, was analysed using the stable isotope technique, and the water transportation characteristics were obtained based on the proportional heat balance method under different weather conditions. The results showed that (1) before raining, the moisture of H. ammodendron mainly relied on groundwater (the average contribution rate was 34.14%) and on soil water located at a depth of 120–180 cm (the average contribution rate was 29.87%). After the rain, H. ammodendron mainly absorbed soil water from a depth of 60–120 cm (the average contribution rate was 33.19%) and groundwater (the average contribution rate was 30.67%); (2) the stem flow of H. ammodendron showed an obvious diurnal variation, showing a “midday rest” phenomenon. The stem flow showed a peak value, and in sunny days, it was ~2 fold higher than that in cloudy days. (3) The stem flow rate of H. ammodendron varied regularly overtime as follows: August > July > September > June > May, and the meteorological factors affecting its stem flow were solar radiation (0.826) > atmospheric temperature (0.598) > humidity (-0.573). The results provide basic support for the ecological conservation of the desert plant H. ammodendron, while also having important implications for ecological restoration in arid regions.

Quantification of Stemflow in Three Isolated Shrub Species in an Urban Environment

As precipitation falls on to vegetation, it is partitioned into throughfall, vapor and stemflow. The stemflow component is frequently neglected in water budgeting for trees and shrubs due to its presumed small volume and limited research. Studies of stemflow in shrub species are especially rare. This study focuses on stemflow in shrubs and specifically examines its relationship to plant morphology and meteorological factors. Two individuals of three species, Prunus laurocerasus (common name ‘Otto Luyken'), Hydrangea quercifolia (common name ‘Alice’), and Itea virginica (common name ‘Little Henry’), were studied in an outdoor experiment in Philadelphia, PA during the 2015 growing season. Stemflow was collected using aluminum collars which had been attached to individual branches of each plant. Vinyl tubing conveyed the stemflow from the collars into collection bottles which were weighed after rain events. To relate stemflow to plant morphology, the vertical projected canopy area of each collared branch, branch attachment angle, stem circumference, and direction of collar were evaluated. To relate stemflow to meteorological conditions, the research also quantified rain depth, rain intensity, rain event duration, wind speed, wind direction, temperature, relative humidity, gust speed, and date and time of storm. The importance of each of these independent variables were studied using a forward stepwise linear regression. Stemflow averaged 7.6% of total incident rainfall on the canopy area of the monitored stems, with values ranging from 0% to 58% by branch and storm event. Species-specific averages were found to be 11.4%, 7.0%, and 4.4% for P. laurocerasus, H. quercifolia, and I. virginica, respectively. The results suggest a significant variation in stemflow by species. Statistical analysis determined that between 55% and 79% of the observed variation in stemflow can be explained by the regression model variables and gust speed and projected canopy area were determined to be significant across all regression models. Stemflow rates appear to be impacted by both inter-plant and local climate factors; however, additional research is needed to further refine the understanding of stem flow and canopy water budgeting.

Effect of biotic and abiotic factors on inter- and intra-event variability in stemflow rates in oak and pine stands in a Mediterranean mountain area

Stemflow, despite being a small proportion of gross rainfall, is an important and understudied flux of water in forested areas. Recent studies have highlighted its complexity and relative importance for understanding soil and groundwater recharge. Stemflow dynamics offer an insight into how rain water is stored and released from the stems of trees to the soil. Past attempts have been made to understand the variability of stemflow under different types of vegetation, but rather few studies have focused on the combined influence of biotic and abiotic factors on inter and intra-storm stemflow variability, and none in Mediterranean climates. This study presents stemflow data collected at high temporal resolution for two species with contrasting canopies and bark characteristics: Quercus pubescens Willd. (downy oak) and Pinus sylvestris L. (Scots pine) in the Vallcebre research catchments (NE of Spain, 42° 12′N, 1° 49′E). The main objective was to understand how the interaction of biotic and abiotic factors affected stemflow dynamics. Mean stemflow production was low for both species (∼1% of incident rainfall) and increased with rainfall amount. However, the magnitude of the response depended on the combination of multiple biotic and abiotic factors. Both species produced similar stemflow volumes and the largest differences were found among trees of the same species. The combined analysis of biotic and abiotic factors showed that funneling ratios and stemflow dynamics were highly influenced by the interaction of rainfall intensity and tree size.

Effects of drought stress and subsequent rewatering on major physiological parameters of spring maize during the key growth periods

For deeply understanding water consumption characteristics and disaster-causing mechanism of spring maize under drought stress, continuous no-water complementing for 40 days and subsequent rewatering treatments were conducted in jointing (T1) and tasseling (T2) stages of spring maize 'Danyu 39'. In the meantime, leaf and root water potential, main variables associated with photosynthesis including net photosynthetic rate (Pn), transpiration rate (Tr), stomatal conduc-tance (gs), intercellular CO2 concentration(Ci) and stem flow rate (SF) were dynamically observed and the characteristics of their responses to drought and subsequent rehydration were investigated. The results indicated that leaf and root water potential, both presenting logarithm relationships with soil water content, decreased due to suffering from drought stress in different growth stages and the response of the former lagged behind that of the latter. At the same time, the response of leaf (root) water potential to drought stress in tasseling stage was earlier (later) than in jointing stage. For the response of rewatering, leaf water potential for the treatment T1(T2) was (not) able to recover to a certain extent, and could not reach the normal condition, while water potential of root was more responsive and closer to the normal level than that of leaf for the treatment T1. Furthermore, Pn and Tr responded more quickly to the treatment T2 than to the treatment T1. For subsequent rewatering after the treatment T1(T2), both Pn and Tr restored rapidly (slowly) with the former exceeding (returning) and the later being (not) able to reach normal level. Meanwhile, the response of Tr was faster than that of Pn to the treatment T1 and they responded simultaneously to the treatment T2. The response of gs agreed with Pn to drought stress. Change trend of Ci for the treatment T1(T2) was consistent (opposite) with that of Pn. In addition, SFs for various drought treatments and their daily maximums decreased and appeared ahead of time to different extents, respectively. At the same time, the response of SF to drought stress was more sensitive for the treatment T2 than for T1 and on a clear day than on a cloudy day, but the sensibility of SF declined after drought reached a certain level. Besides, SFs for both the treatment T1 and T2 increased as a result of rewatering after drought and the increase for the treatment T1 was larger than that for the treatment T2.

Influences of Rainfall Intensity and Leaf Area on Corn Stemflow: Development of a Model

As an important pathway for movement of rainfall or sprinkler irrigation water through a crop canopy to the ground, stemflow is of great significance for utilization efficiency of sprinkler irrigation water and for crop growth. In this study, under simulated indoor artificial rainfall, the stemflow rates (SF) of corn plants (Zea mays) in different corn growth stages (V4 stage ∼ VT stage) under different rainfall intensities (I) were observed, and the relationships among stemflow, leaf area (LA), and I were analyzed. Based on these results, stemflow models were developed. The results showed that for all corn growth stages, the average SF of a single corn plant was about 55.69 mL/min, accounting for 45% of total rainfall. SF increased as a power function of corn LA and I, and the percentage of stemflow in total rainfall increased as a power function of corn LA. Theoretical, semi‐empirical, and empirical models of corn SF and stemflow proportion (SR) of total rainfall were established by analyzing the relationships among LA, I, and stemflow. All three models were used to estimate SF and SR in different corn growth stages and achieved desired accuracy. The semi‐empirical and empirical models were more accurate in predicting and simulating corn SF, but the calculation and application of the semi‐empirical model was relatively simpler. The empirical model of SR enabled a more accurate calculation of the percentage of stemflow in total rainfall.

Characters related to higher starch accumulation in cassava storage roots.

Cassava (Manihot esculenta) is valued mainly for high content starch in its roots. Our understanding of mechanisms promoting high starch accumulation in the roots is, however, still very limited. Two field-grown cassava cultivars, Huanan 124(H124) with low root starch and Fuxuan 01(F01) with high root starch, were characterised comparatively at four main growth stages. Changes in key sugars in the leaves, stems and roots seemed not to be strongly associated with the final amount of starch accumulated in the roots. However, when compared with H124, F01 exhibited a more compact arrangement of xylem vascular bundles in the leaf axils, much less callose around the phloem sieve plates in the stems, higher starch synthesis-related enzymatic activity but lower amylase activity in the roots, more significantly up-regulated expression of related genes, and a much higher stem flow rate (SFR). In conclusion, higher starch accumulation in the roots results from the concurrent effects of powerful stem transport capacity highlighted by higher SFR, high starch synthesis but low starch degradation in the roots, and high expression of sugar transporter genes in the stems. A model of high starch accumulation in cassava roots was therefore proposed and discussed.

Stem flow of seed-maize under alternate furrow irrigation and double-row ridge planting in an arid region of Northwest China

Maize is widely planted throughout the world and has the highest yield of all the cereal crops. The arid region of Northwest China has become the largest base for seed-maize production, but water shortage is the bottleneck for its long-term sustainability. Investigating the transpiration of seed-maize plants will offer valuable information for suitable planting and irrigation strategies in this arid area. In this study, stem flow was measured using a heat balance method under alternate furrow irrigation and double-row ridge planting. Meteorological factors, soil water content (θ), soil temperature (Ts) and leaf area (LA) were also monitored during 2012 and 2013. The diurnal stem flow and seasonal dynamics of maize plants in the zones of south side female parent (SFP), north side female parent (NFP) and male parent (MP) were investigated. The order of stem flow rate was: SFP>MP>NFP. The relationships between stem flow and influential factors during three growth stages at different time scales were analyzed. On an hourly scale, solar radiation (Rs) was the main driving factor of stem flow. The influence of air temperature (Ta) during the maturity stage was significantly higher than in other periods. On a daily scale, Rs was the main driving factor of stem flow during the heading stage. During the filling growth stage, the main driving factor of NFP and MP stem flow was RH and Ts, respectively. However, during the maturity stage, the environmental factors had no significant influence on seed-maize stem flow. For different seed-maize plants, the main influential factors were different in each of the three growing seasons. Therefore, we identified them to accurately model the FP and MP stem flow and applied precision irrigation under alternate partial root-zone furrow irrigation to analyze major factors affecting stem flow in different scales.

Tree traits and meteorological factors influencing the initiation and rate of stemflow from isolated deciduous trees

AbstractTree canopy processes affect the volume and biogeochemistry of inputs to the hydrological cycle in cities. From June 2012 to November 2013, we studied stemflow production from 37 isolated deciduous park trees in a semi‐arid climate dominated by small precipitation events. To clarify the effects of canopy traits on stemflow metrics, we analysed branch angles, bark relief (one component of roughness), tree size, canopy and wood cover fraction, median leaf size, and branch and leader counts. High branch angles contributed to stemflow production in both single‐leader and multi‐leader trees. While bark relief was negatively correlated with stemflow rates in multi‐leader trees, it was positively correlated with rates for single‐leader trees, possibly reflecting the conducive role of linear furrows once bark of single‐leader trees is saturated. The association between numerous leaders, low stemflow initiation thresholds, and high rates deserves further study. Among meteorological variables, rain depth was strongly correlated with stemflow yields; rainfall inclination angle and wind speed were positively correlated with yields, while total intra‐storm break duration and vapour pressure deficit were inversely related. For rain depths <3 mm, greater stemflow was generally associated with leafless canopies. In support of integrated stormwater management, our results can inform climate‐sensitive selection and siting of urban trees with traits that tend to either promote or minimize stemflow, depending on infiltration potential. Copyright © 2015 John Wiley & Sons, Ltd.

Stemflow of water on maize and its influencing factors

Stemflow is important for analyzing soil water dynamics and plant growth in regions with limited rainfall. The objective of this study was to determine the amount of stemflow in relation to plant and rainfall properties. In this study, stemflow was measured using a high water adsorption sheet method during the period of maize plant height growth approximately from 100cm to 230cm when the leaf area index increases from 1.0 to 4.5. There were 28 rainfall events with rainfall amounts for each event ranging from 0.4 to 12.6mm and rainfall intensities ranging from 0.4 to 35mm/h. The results show that stemflow increased with increasing total rainfall and leaf area index but decreased with increasing rainfall intensity. Throughout a maize season, stemflow amounts ranged from 10 to 70mm when the total rainfall amounts ranged from 30 to 135mm, with a mean stemflow rate of 0.42. These results may help farmers in irrigation scheduling of maize under surface-mulching conditions in arid region.

Effect of strip thinning on rainfall interception in a Japanese cypress plantation

Summary We examined the effect of strip thinning on rainfall interception (Ei) in a 32-year-old Japanese cypress plantation in central Japan. Strip thinning was conducted in the catchment in October 2011; that removed 50% of the stems. The gross precipitation (Pg), throughfall (TF) and stemflow (SF) were monitored in a 12-m × 13-m plot before and after thinning. Ei was calculated as the difference between Pg and the sum of TF and SF. The interception processes were illustrated using the revised Gash model with quantifying interception parameters. The results showed that the Gash model successfully predicted Ei on a rainy-season basis in both pre- and post-thinning periods. Thinning altered the interception components whereas the largest part during and after rainfall accounted for similar proportion in both periods. Additionally, after thinning, the annual TF rate was increased from 61.4% to 73.0%, whereas the annual SF rate was decreased from 9.8% to 6.1%, and the annual Ei rate was decreased from 28.7% to 20.8%. The summarized findings of previous studies indicate that the degree of decline in the Ei caused by thinning is related to Pg and the thinning ratio. These results provide useful information for understanding the changes in interception processes induced by thinning, and for acquiring a more accurate forecast of the effects of forest management practices on water resources in the watershed. The response in rainfall partitioning to strip thinning can also help us to acquire an integrated understanding of the changes in canopy water balance under different forest practices.

보통형 콤바인 부착용 유채 예취장치 개발 (III) - 유채 기계 수확 손실 절감을 위한 요인 구명 -

Field test was conducted to investigate primary factors reducing rapeseed harvesting using a reciprocating cutter-bar of combine. The results showed that the correlation between crop moisture content and yield loss had a U-type, which indicated that the yield reduction increased at too high and too low crop moisture contents. The proper ranges of crop moisture contents were 27<TEX>${\sim}$</TEX>35%, 21<TEX>${\sim}$</TEX>56%, and 62<TEX>${\sim}$</TEX>73% in case of grain, pod and stem, respectively. Crop moisture content was negatively correlated with header loss, but positively correlated with threshing loss. In contrary, stem moisture content showed positive correlations with total loss, threshing loss and separation loss. Working speed was positively correlated with header loss. Total flow rate, pod flow rate and stem flow rate were highly correlated with threshing loss and separation loss. However, grain flow rate did not show any correlation with total loss. According to the principal component analysis, two principal components were derived as components with eigenvalues greater than 1.0. The contribution rates of the first and the second components were 52.7% and 38.9%, which accounted for 91.6% of total variance. As a contributive factor influencing total loss of rapeseed mechanical harvesting, a crop moisture content factor was greater than a crop flow rate factor. The stepwise multiple regression analysis for total loss was conducted using crop moisture content factor, crop flow rate factor and coefficient. However, the model did not show any correlation among independent and dependent factors (<TEX>$R^2$</TEX>=0.060).