Water Interception Research Articles

Suppression of transpiration due to cloud immersion in a seasonally dry Mexican weeping pine plantation

Cloud immersion affects the water budget of fog-affected forests not only by introducing an additional source of water (via cloud water interception by the canopy), but also by suppressing plant transpiration. The latter effect is often overlooked and not routinely quantified, restricting a complete understanding of the net hydrological effect of cloud immersion and the possible consequences of projected reductions in cloud immersion under drier and warmer climates in tropical montane regions in the coming decades. This paper describes an approach to quantify the suppression of stand-level tree transpiration (Et) due to cloud immersion using measurements of sapflow, fog occurrence (visibility), leaf wetness, and near-surface climate. Estimates of fog-induced Et suppression in a 10-year-old Pinus patula plantation in the montane cloud belt of central Veracruz, Mexico, are presented for two contrasting dry seasons and a wet season. Fog occurred for 32% of the total study period, although showing pronounced seasonal variation (e.g. 44% during the second dry season). When fog occurred it was accompanied by rainfall during three quarters of the total time. Although the canopy was wet for almost a third of the time, fog-induced canopy wetness constituted only a very small portion of this total (2%). Relative to sunny conditions, Et was suppressed by 90±7% under conditions of dense fog versus 83±7% under light fog and 78±10% during overcast conditions. Quantification of the potential change in annual Et associated with two scenarios for future cloud immersion at the study site revealed that: (i) when all fog occurrence is replaced by overcast conditions, mean annual Et (645±50mm) is likely to increase by only 2±1%; and (ii) when sunny conditions replace all foggy conditions, the likely increase in annual Et is 17±3%. As the rise in the regional lifting condensation level is likely to be on the order of only a couple of hundred meters and will probably result in a shift to overcast rather than clear-sky conditions, the present results suggest that the corresponding impact on Et may be relatively small. Consequently, a climate change-related reduction in dry-season precipitation, through the associated potential reductions in soil water reserves, presents a more worrisome prospect for plant–water relations and water yield from headwater catchments than diminishing cloud immersion alone. The present results highlight the need for better projections of climate change-related alterations in cloud cover and immersion, as well as rainfall patterns for tropical montane regions.

Study on original ecological tridimensional slope vegetation

No matter from the perspective of slope protection, landscape effect and construction cost, or from the perspective of ecological benefit, the development of original ecological tridimensional vegetation has become the inevitable trend for slope vegetation in pursuit of protecting ecological condition, decreasing soil erosion, maintaining ecological balance and beautifying environment of slope. The concept of original ecological tridimensional slope vegetation is proposed in this paper, and the original ecological tridimensional slope vegetation is studied through theoretical analysis and experiments. Specifically, the mechanical effect of slope vegetation in reinforcing the cohesion and shear strength of soil mass is firstly discussed, and then experiments are performed to study the water interception and containing function of slope under various vegetation conditions. Moreover, the relation between soil moisture and cohesion, the relation between root distribution density and cohesion, and the relation between root distribution density and soil shear strength are also studied based on experiments. Finally, based on field observation, the soil erosion states of slope under various vegetation conditions are comparatively studied. It is found that the original ecological tridimensional slope, which combines grass, shrub and tree, can generate comprehensive slope protection effects, and hence strengthen the slope protection ability and bring multiple slope protection benefits. Thereby, the theoretical foundation for developing original ecological tridimensional slope vegetation is established.

The atmospheric water as a triggering factor for earthquakes in the central Virginia seismic zone

Even though central Virginia is far from the nearest plate boundaries, the region is well-known for minor-to-moderate shocks, which have occurred frequently since at least the eighteenth century. Many of its people have experienced small earthquakes, while infrequent larger ones have caused damage. The largest destructive earthquake (magnitude 5.8) in this seismic zone was recorded in August 2011. Smaller earthquakes that cause little or no damage are felt each year or two. It is difficult to link the earthquakes of this zone to known small faults which are numerous, deeply buried and do not show up at the surface. The mean earthquake depth since 1960 is 6.7 km. On the other hand, central Virginia is a big collector and transporter of precipitation water, which flows to the Atlantic Ocean through the James River and its tributaries. There are about 2,000 abandoned mining sites in Virginia with underground openings that can facilitate the interception and conveyance of surface water. This paper presents evidence that seismic activity in certain zones can be associated clearly with the hydrological effects of abundant precipitation. Such effects can increase tectonic stress, which surpasses the marginal amount when an earthquake occurs. We analyze the cross-correlation between precipitation or water discharge in the rivers and earthquake occurrence in the central Virginia seismic zone. This correlation is examined both over a long-term span (57–92 years) and with regard to individual cases in which earthquakes have followed the occurrence of intense hydrological phenomena such as torrential rainfall or hurricanes. As we probe for a correlation between earthquake time series for central Virginia and the monthly precipitation series at hydrometeorological stations located in the zone, we observe that the best cross-correlation is obtained for a time period of 3 months. The same time period applies to certain historical earthquakes that were preceded by large amounts of precipitation. These results support the hydroseismicity hypothesis, which points to the role of water in the generation of intraplate seismicity.

Wind and gravity mechanical effects on leaf inclination angles

In a tree, the distribution of leaf inclination angles plays an important role in photosynthesis and water interception. We investigate here the effect of mechanical deformations of leaves due to wind or their own weight on this distribution. First, the specific role of the geometry of the tree is identified and shown to be weak, using models of idealized tree and tools of statistical mechanics. Then the deformation of individual leaves under gravity or wind is quantified experimentally. New dimensionless parameters are proposed, and used in simple models of these deformations. By combining models of tree geometry and models of leaf deformation, we explore the role of all mechanical parameters on the Leaf Inclination Angle Distributions. These are found to have a significant influence, which is exemplified finally in computations of direct light interception by idealized trees.

Patterns in Residential Urban Forest Structure Along a Synthetic Urbanization Gradient

The environmental sciences increasingly need to understand the ecological effects of urbanization. This is especially true for the urban forest, a major component of the urban environment that is relied on to provide ecosystem services such as air pollution removal and storm water interception. The urbanization gradient is a popular organizing concept for assessing ecological response to varying urbanization intensity, and recent methodological improvements have moved beyond simple distance-based gradients to more sophisticated synthetic gradients based on urbanization indicators such as population density and impervious surface intensity. Although these synthetic gradients provide a more complete picture of urbanization than any one indicator alone can provide, it is unclear how synthetic gradients relate to ecological structure. In this study, we collected field data on urban forest structure from 150 residential properties over a 40-km transect in Minnesota's Twin Cities metropolitan area. We then applied factor analysis to a set of nineteen urbanization indicators and extracted two primary urbanization trends strongly related to distance from the urban core and residential neighborhood density, respectively. We related the synthetic gradient to urban forest structure using polynomial regression models. The synthetic gradient explained nine of the fourteen urban forest structural variables assessed and improved on a simple distance-based gradient by explaining patterns in tree canopy cover. Our findings demonstrate the need to consider the effects of secondary urbanization trends on ecological structure. These results support the continued application of synthetic gradient approaches to understanding the relationships between urbanization and ecological structure.

A loess landslide induced by excavation and rainfall

The initiation of loess landslides is a common engineering problem during the construction of the expressway or other engineering works in the Loess Plateau of China. The engineers and researchers should devote themselves to the prevention of the initiation of loess landslides. This study focused on a loess landslide which was induced during the construction of an expressway in Shanxi Province of China. The stabilities of the loess hillside slope before and after excavation were analyzed using limit equilibrium analysis method and the strength reduction finite element method, respectively. The analysis results indicated that the loess hillside slope, before excavation, was stable under both natural state and rainfall conditions. The collapse of the loess hillside slope, or the initiation of loess landslides, after having been excavated, was induced by excavation and rainfall. The integrated stabilization method including four parts was used to stabilize the loess landslide. The four parts were a reinforced concrete piles row, a rubble concrete retaining wall, alteration of slope geometry, and interception and drainage of water. The initiation of the loess landslide might be evitable if it was given enough attention before excavation; thus, the problem of loess landslides should be paid big attention during the survey and design of the engineering works, not only during the construction.

极端干旱区多枝柽柳幼苗对人工水分干扰的形态及生理响应

PDF HTML阅读 XML下载 导出引用 引用提醒 极端干旱区多枝柽柳幼苗对人工水分干扰的形态及生理响应 DOI: 10.5846/stxb201305091000 作者: 作者单位: 新疆师范大学生命科学学院,新疆师范大学生命科学学院,荒漠与绿洲生态国家重点实验室,新疆师范大学生命科学学院,新疆师范大学生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(41261103);新疆维吾尔自治区自然科学基金资助项目(2012211B18) The morphological and physiological responses of Tamarix ramosissima seedling to different irrigation methods in the extremely arid area Author: Affiliation: Xinjiang Normal University,,,, Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:在塔里木河下游断流河道人工生态输水的大背景下,多枝柽柳(Tamarix ramosissima )作为当地优势物种,其更新恢复研究对下游荒漠河岸林的恢复尤为重要。通过研究多枝柽柳幼苗形态、水分和光合生理对不同灌溉处理的响应,分析不同人工水分干扰模式对柽柳幼苗生长发育的影响。实验设计了侧渗分层(LSI)和地表灌溉(AGI)两种给水方式,以及高灌(W1,50 L/株)、中灌(W2,25 L/株)、低灌(W3,12.5 L/株)3 个给水水平,并在整个生长季定期监测幼苗的形态参数变化、生物量、水势和光合速率。结果显示:(1)侧渗分层灌溉方式对幼苗基径、株高、冠幅以及前期生长速率都有促进作用;(2)在侧渗分层灌溉高灌下,幼苗地下及总生物量都显著高于地表灌溉(P < 0.05),且地表灌溉下根冠比(R/S:Root shoot ratio)明显高于侧渗分层灌溉;(3)侧渗分层灌溉下,幼苗茎水势高于地表漫灌,且在中灌和低灌下达到显著水平(P < 0.05),表明侧渗分层灌溉下幼苗的水分吸收效率更高;(4)在侧渗分层高灌及中灌下,实际光化学光量子产量值高于地表灌溉处理,并在高灌时差异极显著(P < 0.01)。研究表明,侧渗分层灌溉方式对多枝柽柳幼苗早期生长及水分和光合生理都具有显著促进作用。 Abstract:Water shortages are not only the main limiting factor of plant survival and growth in many habitats, but also are the direct cause for vegetation degradation in arid regions. The lower reaches of Tarim River are located in an extremely arid climate in northwestern China. The vegetation structure along the river banks of the lower reaches of the Tarim River is relatively simple, with only a few plant species present. Major plant species include such trees as Populus euphratica and shrubs such as Tamarix ramosissima, and Tamarix hispida. During the past 50 years, intense human activities effects in this region have led to the nearly complete interception of water in 321 km of the watercourse in the lower reaches of the Tarim River; as a result, the groundwater table has dropped considerably and natural vegetation which depends on that groundwater has become severely degraded. To preserve the endangered desert river bank forest vegetation and restore the damaged ecological system, an Ecological Water Conveyance Project was initiated in 2000. Artificially planting native dominant plant species including Tamarix spp. to initiate rapid rehabilitation of the plant community has become an important research subject in this area. However, the increased river flow from this project has produced very limited results in increasing both the amount of intermittent water flow in the river and in raising the downstream ground water table. As a result, the water demands of the T. ramosissima seedlings in the early growth stage could not be met. Therefore, irrigating field transplanted seedlings during the early stage of growth has been very important. T. ramosissima was once widely distributed in the desert plains and in the sandy and alkaline lands in northwestern China. It was also a dominant shrub in the desert riparian forest in the lower reaches of the Tarim River and played a key role in ecological rehabilitation and maintenance of the stability of the riparian forest in this area. The objective of this study was to test the growth and physiological responses of T. ramosissima seedling to different irrigation methods, i.e. layered side irrigation (LSI) and aboveground irrigation (AGI), using three water levels, i.e. high (W1, 50 L plant-1 repetition-1), medium (W2, 25 L plant-1 repetition-1) and low (W3, 12.5 L plant-1 repetition-1) water levels. The results showed that LSI increased basal diameter, stem length, crown width and growth rate of the seedling; LSI also increased soil moisture under the same water level conditions when compared with the AGI method. LSI significantly increased belowground biomass, total biomass and the root shoot ratio (R/S) of the seedling under W1 (P < 0.05). LSI significantly increased stem water potential under W1 and W2 (P < 0.05). The findings show that LSI can be used to increase water use efficiency of the seedlings. LSI increased photochemical quantum yield of PSⅡ in the light (Yield) of the seedlings under W1 and W2, and this increase was statistically significant under W1 (P < 0.05). Our results suggest that LSI caused rapid and large amounts of growth and biomass production in T. ramosissima seedlings, as well as had a valuable positive effect on water potential and photosynthesis which benefited the seedling's survival rates during the early stage of growth. 参考文献 相似文献 引证文献

Cloud water interception in the temperate laurel forest of Madeira Island

A cloud belt frequently forms on the windward side of Madeira Island, between 800 and 1600 m a.s.l., as a result of adiabatic cooling of the northeastern trade winds that are forced upward. Temperate laurel forest is the most common vegetation inside that cloud belt altitudinal range. Cloud water interception was estimated by comparing precipitation and throughfall during a hydrological year. It totalled 200 mm (8% of rainfall) during 65 days (3 mm d−1) and seems to constitute a larger fraction of water input during drier months. Multiple linear regression between gauge standard deviation and throughfall throughout rain events shows that cloud interception is common before the onset of rainfall. Its role in the ecohydrology of laurel forest and in the island's hydrology should be acknowledged. Further studies on this issue should be a priority in order to better understand these dynamics and provide tools for the correct management of this protected forest and the island's groundwater resources. Editor Z.W. Kundzewicz Citation Figueira, C., Menezes de Sequeira, M., Vasconcelos, R., and Prada, S., 2013. Cloud water interception in the temperate laurel forest of Madeira Island. Hydrological Sciences Journal, 58 (1), 1–10.

TOPOLOGY EXTRACTION USING DEPTH FIRST SEARCH ON VOXEL REPRESENTATIONS OF TREE POINT CLOUDS

Abstract. The three-dimensional reconstruction of the vegetation structure is a requirement for the analysis of interaction between biosphere and atmosphere. Information about the 3D structure of plants enables the modeling of crucial processes, like water interception or absorption of light. Terrestrial laser scanners have proven to be a valuable tool to rapidly and accurately capture the geometry of plants as point clouds, which provide the foundation for analyzing their structure. Based on a very dense but unstructured, noisy point cloud, we have presented a method to extract the topology of a tree in form of a tree graph, demonstrated on a test set of single birches. In a first step we have applied a variation of the Circular Hough Transform to detect a set of 3D points, which represent the tree trunk. Subsequently, the point cloud is transformed onto a voxel space and filtered to a connected component representation of only the main object. In the second step, the residual voxels are interpreted as a connected graph and the Depth First Search algorithm is employed to retrieve the topology of the scanned tree.

SENSITIVITY ANALYSIS OF BIOME-BGC MODEL FOR DRY TROPICAL FORESTS OF VINDHYAN HIGHLANDS, INDIA

Abstract. A process-based model BIOME-BGC was run for sensitivity analysis to see the effect of ecophysiological parameters on net primary production (NPP) of dry tropical forest of India. The sensitivity test reveals that the forest NPP was highly sensitive to the following ecophysiological parameters: Canopy light extinction coefficient (k), Canopy average specific leaf area (SLA), New stem C : New leaf C (SC:LC), Maximum stomatal conductance (gs,max), C:N of fine roots (C:Nfr), All-sided to projected leaf area ratio and Canopy water interception coefficient (Wint). Therefore, these parameters need more precision and attention during estimation and observation in the field studies.

Study of Ecological Restoration Technique for Dam’s Downstream River

To solve the ecological deterioration problems of the medium and small reservoirs’ downstream areas caused by water interception, the ecological restoration technique for dam’s downstream area is studied in this paper. Based on the investigation and analysis of the current ecological environment of a medium and small reservoirs’ downstream area in Qingyuan county of Liaoning, the downstream minimum ecological flow, with which the ecological environment of downstream can connect to that of upstream, is calculated. In the way of drawing water above the dam and building underground dam, the minimum ecological flow for the ecological environment of the downstream area will be able to reach a level where the continuity of the ecological environment is maintained. Consequently the aquatic habitats and stream ecological environment of the dam’s downstream channel can be improved and recovered.

Leaching of Three Imidazolinone Herbicides during Sprinkler Irrigation

Some imidazolinone herbicides have been shown to be mobile in soil, raising concern about their possible movement to ground water. Three imidazolinone herbicides (imazamethabenz-methyl, 497 g ha(-1); imazethapyr, 14.7 g ha(-1); and imazamox, 14.7 g ha(-1)) commonly used in crop production on the Canadian prairies were applied to a tile-drained field to assess their susceptibility to leach when subjected to sprinkler irrigation using a center pivot. Tile-drain flow began when the water table rose above tile-drain depth, and peak flow rates corresponded to the greatest depths of ground water above the tile drains. Interception of irrigation water by the tile drains in each quadrant of the field varied from ∼11 to 20% of the water applied. Under a worst-case scenario in which irrigation began the day after herbicide application and irrigation water was applied at 25 mm d(-1) for 12 d, there was evidence of preferential flow of all three herbicides and hydrolysis of imazamethabenz-methyl to imazamethabenz in the initial samples of tile-drain effluent. In subsequent samples, concentrations (analysis by LC-MS-MS) of the summation of imazamethabenz-methyl (25-24,000 ng L(-1)) plus its hydrolysis product imazamethabenz (63-26,500 ng L(-1)) greatly exceeded those of imazethapyr (<13-1260 ng L) and imazamox (19-599 ng L(-1)), thus reflecting relative application rates. In contrast, estimates of total transport of each herbicide from the root zone, which varied in each quadrant and ranged from 0.06 to 2.3% for imazamethabenz-methyl plus imazamethabenz, 0.71 to 3.1% for imazethapyr, and 0.61 to 2.8% for imazamox, did not reflect application rates. In shallow ground water (piezometer samples), there was inconsistent and infrequent detection all four compounds. With the frequency and amount of rainfall typically encountered in the prairie region of Canada, contamination of shallow ground water with detectable concentrations of the three imidazolinone herbicides would be unlikely.

A Probe on the Planning and Construction of Country Park: A Case Study on Gualv Lake Park, Guangzhou Metropolis

Country Park’s limiting the disorganized spread of urban space is one of the important components of the green space system, and is also one of the most popular construction activities in many metropolises in China. But at present, there are still many problems regarding the theoretical planning and its practical applications. This paper selected “Gualv Lake Park” beside “Zengcheng”, a county-level city, as a case which used landscape planning and combined impound water and sewage interception project systems. The park is a “demonstration area” with the four traits of “nature, simple, low-cost and ecology”. When the first phase was implemented, the park shows its virtues through service functions for ecological systems and flood control. Finally we find that in-depth study of characteristic construction processes is very helpful for understanding rules of Country Park planning, and significant for the protection policy of land- use.

Quantification of cloud water interception along the windward slope of Santa Cruz Island, Galapagos (Ecuador)

The Galapagos Archipelago is nearly devoid of freshwater resources, but during six months of the year, a fog layer covers the windward slopes of the main islands. In order to investigate the hydrological importance of this phenomenon, a monitoring network was set up on Santa Cruz Island, at the center of the archipelago. Meteorological parameters were monitored together with throughfall and stemflow at two stations: a first in a secondary forest at the lowest fringe of the fog layer (400ma.s.l.), and a second in shrub lands of the Galapagos National Park, at the center of the fog layer (650ma.s.l.). Cloud water interception was quantified from the wet canopy water budget, based on a modified Rutter-type canopy interception model. This methodology allowed the estimation of fog interception for short time intervals (15min) and avoided the subjective separation into individual rainfall events. Fog was found to be a negligible water input at the lower site, but was estimated at 26±16% of incident rainfall at the higher site. Wind was shown to enhance fog interception, but this alone could not explain the difference in fog catch between the two sites. Higher liquid water content and more frequent fog occurrence contributed to the difference as well. This study highlights that the presence of fog may induce a marked increase of net precipitation, but this effect is restricted to the summit areas exposed to winds, located in the center of the cloud belt.

Land cover effects on groundwater recharge in the tropics: ecohydrologic mechanisms

ABSTRACTManaging groundwater recharge to ensure sufficient water supply is a growing concern for many communities. We explore land cover effects on recharge processes and rate in Hawai'i, where precipitation on the mountain slopes of leeward Hawai'i Island recharges the aquifer that is the sole source of water for coastal communities. Applying a water balance, we quantify the influences of native forest and cattle pasture on recharge using measurements of precipitation and the drivers of evapotranspiration taken over 18 months. Surface runoff is negligible in these highly permeable basalt watersheds, simplifying fluxes into and out of the recharge area. On the basis of our analysis of measured fluxes, groundwater recharge is 96% of rainfall in pasture, 87% of above‐canopy rainfall in open forest, and 106% of above‐canopy rainfall in dense forest. Differences in recharge among vegetation types result largely from direct interception of cloud water by native Hawaiian forest. The majority of rainfall occurs in infrequent, large storms, so water moves quickly beyond plant rooting depth, limiting its availability for evapotranspiration. Potential evapotranspiration is low, as its drivers are modest and constant throughout the year. Existing estimates of submarine groundwater discharge support our conclusion that the rainfall‐to‐recharge ratio is close to one for all sites. Identifying primary influences on the recharge‐to‐rainfall ratio is key to predicting the types of changes that will have substantial effects on recharge. In any tropical setting with young, porous substrates, precipitation is likely to play a dominant role in the magnitude and variability of groundwater recharge; here, land‐use changes that affect local precipitation, such as an increase in fog interception, will play a larger role than vegetation shifts that affect evapotranspiration. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Cloud water interception in the high altitude tree heath forest (Erica arborea L.) of Paul da Serra Massif (Madeira, Portugal)

AbstractCloud water interception (CWI) occurs when cloud droplets are blown against the forest canopy, where they are retained on the vegetation surface, forming larger water droplets that drip into the forest floor. CWI was measured from 1 October 1997 to 30 September 1999, on a first‐line tree heath (Erica arborea), at Bica da Cana, Madeira Island. Rainfall was corrected for wind‐loss effect and compared with throughfall and other climatological normals. The CWI depletion rate along a forest stand transect was also analysed during three distinct fog events in 2008. Cloud water was 28 mm day−1, corresponding to 68% of total throughfall and 190% of the gross precipitation. Cloud water correlates directly with monthly normals of fog days and wind speed and correlates inversely with the monthly air temperature normal. CWI has an exponential correlation with monthly relative humidity normal. Cloud water capture depletion along the stand shows a logarithmic decrease. Although a forest stand does not directly relate to a first‐line tree heath, this study shows that CWI is a frequent phenomenon in the Paul da Serra massif. Restoration and protection of high altitude ecosystems in Madeira should be a priority, not only for biodiversity, ecological and economical purposes but also for its role in regional water resources. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Water balances of old-growth and regenerating montane cloud forests in central Veracruz, Mexico

► We compare the catchment water budgets of old-growth and regenerating cloud forests. ► Water use was higher in the mature forest mainly because of greater water canopy storage capacity. ► Streamflow was greater in the regenerating forest due to lower rainfall interception. ► Storm runoff was low in both forest attributed to the high permeability of the soils. ► We conclude that 20 years of forest growth is sufficient to restore the original hydrology. This paper compares the water budgets of two adjacent micro-catchments covered by mature (MAT) and 20-year-old secondary (SEC) lower montane cloud forests, respectively, in central Veracruz, Mexico over a 2-year period. Rainfall ( P ) and streamflow ( Q ) were measured continuously, whereas dry canopy evaporation (transpiration E t ), wet canopy evaporation (rainfall interception I ), and cloud water interception ( CWI ) were quantified using a combination of field measurements and modeling. Mean annual P was 3467 mm, of which typically 80% fell during the wet season (May–October). Fog interception occurred exclusively during the dry season (November–April), and was ⩽2% of annual P for both forests. Rainfall interception loss was dominated by post-event evaporation of intercepted water rather than by within-event evaporation. Therefore, the higher overall I (i.e. including CWI ) by the MAT (16% of P vs. 8% for the SEC) reflects a higher canopy storage capacity, related in turn to higher leaf area index and greater epiphyte biomass. Annual E t totals derived from sapflow measurements were nearly equal for the MAT and SEC (∼790 mm each). Total annual water yield calculated as P minus ( E t + I ) was somewhat higher for the SEC (2441 mm) than for the MAT (2077 mm), and mainly reflects the difference in I . Mean annual Q was also higher for the SEC (1527 mm) than for the MAT (1338 mm), and consisted mostly of baseflow (∼90%). Baseflow recession rates were nearly equal between the two forests, as were stormflow coefficients (4% and 5% for MAT and SEC, respectively). The very low runoff response to rainfall is attributed to the high infiltration and water retention capacities of the volcanic soils throughout the ∼2 m deep profile. The water budget results indicate that ∼875 and 700 mm year −1 leave the SEC and MAT as deep groundwater leakage, which is considered plausible given the fractured geology in the study area. It is concluded that 20 years of natural regeneration following cloud forest disturbance in central-eastern Mexico is capable of producing near-original hydrological behavior.

Canopy water balance of windward and leeward Hawaiian cloud forests on Haleakalā, Maui, Hawai'i

AbstractThe contribution of intercepted cloud water to precipitation at windward and leeward cloud forest sites on the slopes of Haleakalā, Maui was assessed using two approaches. Canopy water balance estimates based on meteorological monitoring were compared with interpretations of fog screen measurements collected over a 2‐year period at each location. The annual incident rainfall was 973 mm at the leeward site (Auwahi) and 2550 mm at the windward site (Waikamoi). At the leeward, dry forest site, throughfall was less than rainfall (87%), and, at the windward, wet forest site, throughfall exceeded rainfall (122%). Cloud water interception estimated from canopy water balance was 166 mm year−1 at Auwahi and 1212 mm year−1 at Waikamoi. Annual fog screen measurements of cloud water flux, corrected for wind‐blown rainfall, were 132 and 3017 mm for the dry and wet sites respectively. Event totals of cloud water flux based on fog screen measurements were poorly correlated with event cloud water interception totals derived from the canopy water balance. Hence, the use of fixed planar fog screens to estimate cloud water interception is not recommended. At the wet windward site, cloud water interception made up 32% of the total precipitation, adding to the already substantial amount of rainfall. At the leeward dry site, cloud water interception was 15% of the total precipitation. Vegetation at the dry site, where trees are more exposed and isolated, was more efficient at intercepting the available cloud water than at the rainy site, but events were less frequent, shorter in duration and lower in intensity. A large proportion of intercepted cloud water, 74% and 83%, respectively for the two sites, was estimated to become throughfall, thus adding significantly to soil water at both sites. Published in 2010 by John Wiley &amp; Sons, Ltd.

Rainfall partitioning and cloud water interception in native forest and invaded forest in Hawai'i Volcanoes National Park

AbstractIn many Hawaiian forests, including cloud forests, native plant communities are being displaced by invasive tree species, possibly affecting rainfall partitioning and direct harvesting of cloud droplets by vegetation. In this study, the hydrological impacts of invasive species are examined, using measurements of rainfall (RF), throughfall (TF) and stemflow (SF), and estimation of wet‐canopy evaporation and cloud water interception (CWI) by the canopy water balance approach in both native Metrosideros polymorpha‐dominated and invaded, Psidium cattleianum‐dominated forests within Hawai'i Volcanoes National Park (HAVO). Canopy water storage capacity was found to be more than twice as great at the native site (1·86 mm) compared to the invaded site (0·85 mm). Annual RF, CWI, TF and SF were 3233, 1188, 3700 and 261 mm, respectively, for the native site; and 3735, 734, 3033 and 1091 mm, respectively, for the invaded site. Net RF (TF + SF) was 123 and 110% of RF, respectively, at the two sites. Annual evaporation of water from the wet canopy was also greater at the native site (464 mm) than at the invaded site (347 mm). Low canopy water storage capacity and the exceptionally high SF total at the invaded site are related to morphological characteristics and high stem density of the invasive P. cattleianum tree, which favour efficient transport of intercepted water to the ground via the stems. Despite its more peripheral location near the edge of the orographic cloud, CWI at the native site was higher. The characteristics of the native M. polymorpha tree may facilitate more effective harvesting of cloud water droplets, enhancing CWI at the site. Species invasion results in a lower proportion of RF reaching the forest floor (110 vs 123%) and becoming available for groundwater recharge, suggesting that invasion by P. cattleianum may have significant negative effects on Hawai'i's aquatic ecosystems and water resources. Copyright © 2010 John Wiley &amp; Sons, Ltd.

A 50th anniversary reassessment of the seminal ‘L ana'i fog drip study’ in Hawai'i

AbstractDuring the 1950s, the Pineapple Research Institute (PRI) in Hawai'i launched one of the first, and still widely cited, quantitative studies of direct cloud water interception (CWI) and its contribution to throughfall (TF) (‘fog drip’) under Cook Pine trees (Araucaria columnaris) on a trade‐wind exposed, mountain ridge on the island of Lāna'i. That study concluded that fog drip under a tree canopy supplemented rainfall (RF) (average 1270 mm year−1) by 762 mm or 60%, even after throughfall was corrected for presumed non‐vertical rainfall also intercepted by the tree. A resurvey of fog drip in the upper Lāna'i watershed was undertaken in 2006–2008. Open‐site automated weather stations were paired with throughfall, stemflow and soil moisture measurements for adjacent Araucaria trees. For upper ridge sites, these results indicate fog drip rates beneath individual Araucaria trees to be substantially greater than found in the earlier study. Fully exposed trees in the frequently cloud‐immersed summit region collected annualized fog drip totals of 901–2883 mm, representing 181–462% of measured rainfall. The increased fog drip may be largely attributed to: (i) a more robust estimate of the indirect (non‐vertical) rainfall contribution; (ii) the increased fog‐capturing capacity of the Araucaria trees which had a height of ∼10 m in the 1950s versus ∼20 m during this study and (iii) the presence of atmospheric conditions favouring much increased CWI at higher ridge elevations (921–1021 m.a.s.l.) compared to the site of the original PRI study at 838 m. The fog drip values reported here are (much) higher than those measured in most other tropical montane cloud forest studies, and reflect the unique site conditions associated with fully exposed isolated trees on a knife‐edged ridge. Copyright © 2010 John Wiley &amp; Sons, Ltd.