Stemflow is a spatially localized point input of precipitation and solutes at the plant stem and is of hydrological and ecological significance in forested and agricultural ecosystems. The purpose of ...this review is to: (1) critically evaluate our current understanding of stemflow; (2) identify gaps in our present knowledge of stemflow; and (3) stimulate further research in areas where present knowledge is weak. The review begins by analyzing stemflow drainage and nutrient inputs under diverse vegetal cover. Stemflow inputs are then examined as a function of meteorological conditions, seasonality, interspecific and intraspecific differences among and within species, canopy structure, spatiality, and atmospheric pollutants in urban environments. Stemflow modeling studies are also reviewed and evaluated. Stemflow yield and chemistry are the result of the interaction of the many complex variables listed. By analyzing each separately, it may be possible to isolate their individual affects on stemflow production and chemistry. A comprehensive understanding of each influencing factor would enable the accurate modeling of stemflow water and nutrient inputs into agricultural and forest soils which may result in the optimization of timber and crop harvests.
Some areas where present knowledge is particularly weak are: (1) stemflow production and nutrient transfers in northern boreal forests (aspen, birch, conifers) and desert cacti; (2) chemical enrichment of stemflow from live trees charred by forest fires; (3) stemflow yield and nutrient inputs during the winter season; (4) intraspecific variation in stemflow production and chemistry; (5) stemflow chemistry from standing dead trees; (6) influence of canopy structure on stemflow chemistry; (7) understory stemflow generation and nutrient transfer; and (8) stemflow enrichment associated with insect infestations.
•Stemflow was monitored for 5years for tree species of contrasting physical traits.•Funneling ratios in subcanopy trees exhibit higher rainfall scavenging efficiency.•Interspecific stemflow response ...varies with canopy leaf phase and seasonality.•Multivariate analysis shows differences in stemflow response to storm variables.•More stemflow studies are necessary to model diverse subcanopy hydrologic response.
Stemflow is an important subcanopy flux that delivers enriched rainfall to soils immediately surrounding a tree. Stemflow volume represents the quantity of this hydrologic flux while funneling ratio (FR) represents the efficiency with which individual trees scavenge water during rainfall events. Stemflow hydrology and storm meteorological characteristics were monitored from 2007 through 2012 to determine the interspecific differences in stemflow flux with a focus on FR efficiency. The objective of this study was to examine the influence of tree species and size on stemflow FR, determine how seasonality affects stemflow FR, and quantify the role of storm meteorological conditions on stemflow FR. The results presented in this paper build upon 2years of previous hydrologic research from the Fair Hill, MD field site, which strengthen previous findings via larger storm sample size and highlight more complex stemflow hydrologic relationships than originally assumed. Specifically, this study has demonstrated (1) the efficiency with which smaller trees gain access to rainfall via higher FR than larger trees, (2) the FR variability of F. grandifolia induced by the species’ ease of generating stemflow under many storm conditions, and (3) the necessity of many years of hydrometeorological sampling to capture long-term rainfall characteristics and trends. The efficiency of smaller trees to preferentially funnel water to their tree base has implications for forests undergoing change. Forest disturbance and subsequent regrowth is dominated by smaller trees, but additional research is necessary to understand how saplings compete among one another to gain access to stemflow and how this may be influenced by changing climates and forest composition.
Storm events dominate riverine loads of dissolved organic carbon (DOC) and nitrate and are expected to increase in frequency and intensity in many regions due to climate change. We deployed three ...high‐frequency (15 min) in situ absorbance spectrophotometers to monitor DOC and nitrate concentration for 126 storms in three watersheds with agricultural, urban, and forested land use/land cover. We examined intrastorm hysteresis and the influences of seasonality, storm size, and dominant land use/land cover on storm DOC and nitrate loads. DOC hysteresis was generally anticlockwise at all sites, indicating distal and plentiful sources for all three streams despite varied DOC character and sources. Nitrate hysteresis was generally clockwise for urban and forested sites, but anticlockwise for the agricultural site, indicating an exhaustible, proximal source of nitrate in the urban and forested sites, and more distal and plentiful sources of nitrate in the agricultural site. The agricultural site had significantly higher storm nitrate yield per water yield and higher storm DOC yield per water yield than the urban or forested sites. Seasonal effects were important for storm nitrate yield in all three watersheds and farm management practices likely caused complex interactions with seasonality at the agricultural site. Hysteresis indices did not improve predictions of storm nitrate yields at any site. We discuss key lessons from using high‐frequency in situ optical sensors.
Key Points
An improved hysteresis index revealed remarkable variation in storm dynamics for 126 storms in watersheds with varied land use/land cover
Seasonality influenced storm nitrate loading; interactions between farm practices and seasonal dynamics were captured by sensors
Sites had generally anticlockwise storm hysteresis for DOC, though storm nitrate hysteresis direction varied by land use/land cover
Stemflow has distinguishable effects on the hydrology and biogeochemistry of wooded ecosystems. Nonetheless, it is a relatively poorly understood hydrologic process. No known studies have ...investigated the temporal variability of stemflow volume at 5-min intervals in a beech-yellow poplar forest of eastern North America. The aim of this research is to compare the temporal variability of stemflow generation by
Fagus grandifolia Ehrh. (American beech) and
Liriodendron tulipifera L. (yellow poplar) in relation to tree species and size. Employing a dense network of tipping-bucket stemflow gages interfaced with a datalogger, a 5
min stemflow yield database was assembled and analyzed to better discern how stemflow production varies (temporally) with tree species and size. Results indicate that both tree species and size have detectable effects on the temporal variability of stemflow yield. Observational data, scientific analysis, and correspondence analysis reveals that stemflow yield: (1) is more similar within than between the two tree species with differences likely being attributable to differences in bark texture and water storage capacity; (2) tree size affects stemflow yield within species; (3) rain event characteristics affect stemflow yield; and (4) stemflow yield for particular trees and rain events is the result of a complex set of interactions among tree species, tree size, and meteorological conditions. These results suggest that the temporal variation in stemflow yield from co-occurring forest trees may play a significant role in subsurface drainage of wooded ecosystems during rain events.
The purpose of the study was to: (1) test if normative bark water storage capacities differed significantly among three co-occurring deciduous tree species; and (2) examine the extent to which ...stemflow production and resulting solute inputs in temperate deciduous forests are affected by bark water storage capacity. Normative bark water storage capacities were determined for:
Betula lenta L. (sweet birch),
Carya glabra Mill. (pignut hickory), and
Quercus rubra L. (northern red oak). Using the computed normative bark water storage capacities, previously published allometric equations relating tree diameter to aboveground woody surface area, and stemflow yield and chemistry data from ten precipitation events, the influence of bark water storage capacity on stemflow production and solute inputs was examined. Results demonstrated normative bark water storage capacities differed significantly among the tree species examined.
Quercus rubra was found to hold the most water and
B. lenta the least. For a 30 cm diameter tree, normative bark water storage capacities ranged from approximately 100 l for
B. lenta to 250 l for
Q. rubra. Despite a higher normative bark water storage capacity,
Q. rubra was computed to have the largest stemflow solute inputs. Differences in stemflow quantities as well as solute inputs were attributable to interspecific variation in bark morphology and branching architecture, characteristics that affect amount of storage and detention times. Bark water storage capacity is linked with the geoecology of temperate deciduous forests because stemflow volume and solute inputs are partly determined by bark water storage capacity.
Synoptic classification is a methodology that represents diverse atmospheric variables and allows researchers to relate large-scale atmospheric circulation patterns to regional- and small-scale ...terrestrial processes. Synoptic classification has often been applied to questions concerning the surface environment. However, full applicability has been under-utilized to date, especially in disciplines such as hydroclimatology, which are intimately linked to atmospheric inputs. This paper aims to (1) outline the development of a daily synoptic calendar for the Mid-Atlantic (USA), (2) define seasonal synoptic patterns occurring in the region, and (3) provide hydroclimatological examples whereby the cascading response of precipitation characteristics, soil moisture, and streamflow are explained by synoptic classification. Together, achievement of these objectives serves as a guide for development and use of a synoptic calendar for hydroclimatological studies. In total 22 unique synoptic types were identified, derived from a combination of 12 types occurring in the winter (DJF), 13 in spring (MAM), 9 in summer (JJA), and 11 in autumn (SON). This includes six low pressure systems, four high pressure systems, one cold front, three north/northwest flow regimes, three south/southwest flow regimes, and five weakly defined regimes. Pairwise comparisons indicated that 84.3 % had significantly different rainfall magnitudes, 86.4 % had different rainfall durations, and 84.7 % had different rainfall intensities. The largest precipitation-producing classifications were not restricted to low pressure systems, but rather to patterns with access to moisture sources from the Atlantic Ocean and easterly (on-shore) winds, which transport moisture inland. These same classifications resulted in comparable rates of soil moisture recharge and streamflow discharge, illustrating the applicability of synoptic classification for a range of hydroclimatological research objectives.
The volumetric quantity and biogeochemical quality of throughfall and stemflow in forested ecosystems are influenced by biological characteristics as well environmental and storm meteorological ...conditions. Previous attempts at connecting forest water and nutrient cycles to storm characteristics have focused on individual meteorological variables, but we propose a unified approach by examining the storm system in its entirety. In this study, we use methods from synoptic climatology to distinguish sub-canopy biogeochemical fluxes between storm events to understand the response of forest ecosystems to daily weather patterns. For solute inputs tied to atmospheric deposition (NH₄⁺, NO⁻, SO₄²⁻, Na⁺, Cl⁻), stagnant air masses resulted in high inputs in rainfall (273.42, 81.81, 52.30, 156.99, 128.70 µmol L⁻¹), throughfall (355.05, 130.66, 83.24, 239.55, 261.32 µmol L⁻¹), and stemflow (338.34, 182.75, 153.74, 125.75, 272.88 µmol L⁻¹). For inputs tied to canopy exchange (DOC, K⁺, Ca¹⁺, Mg²⁺), a clear distinction was observed between throughfall and stemflow pathways. The largest throughfall concentrations were in the Great Lakes Low (1794.80, 352.96, 72.75, 74.37 µmol L⁻¹) while the largest stemflow concentrations were in the Weak Upper Trough (3681.78, 497.34, 82.36, 72.46 µmol L⁻¹). Stemflow leaching is likely derived from a larger reservoir of leachable cations in the tree canopy than throughfall, with stemflow fluxes maximized during synoptic types with greater rainfall amounts and throughfall fluxes diluted. For flux-based enrichment ratios, water volume, storm magnitude, antecedent dry period, and seasonality were important factors, further illustrating the influence of synoptic characteristics on wash-off, leaching and, ultimately, dilution processes within the canopy.
Compared with the phyllosphere, bacteria inhabiting bark surfaces are inadequately understood. Based on a preliminary pilot study, our work suggests that microbial populations vary across tree bark ...surfaces and may differ in relation to surrounding land use. Initial results suggest that stemflow, the water that flows along the bark surface, actively moves bacterial communities across a tree. These preliminary findings underscore the need for further study of niche microbial populations to determine whether there are connections between the biodiversity of microbiomes inhabiting corticular surfaces, land use, and hydrology.
In autumn, the dissolved organic matter (DOM) contribution of leaf litter leachate to streams in forested watersheds changes as trees undergo resorption, senescence, and leaf abscission. Despite its ...biogeochemical importance, little work has investigated how leaf litter leachate DOM changes throughout autumn and how any changes might differ interspecifically and intraspecifically. Since climate change is expected to cause vegetation migration, it is necessary to learn how changes in forest composition could affect DOM inputs via leaf litter leachate. We examined changes in leaf litter leachate fluorescent DOM (FDOM) from American beech (Fagus grandifolia Ehrh.) leaves in Maryland, Rhode Island, Vermont, and North Carolina and from yellow poplar (Liriodendron tulipifera L.) leaves from Maryland. FDOM in leachate samples was characterized by excitation‐emission matrices (EEMs). A six‐component parallel factor analysis (PARAFAC) model was created to identify components that accounted for the majority of the variation in the data set. Self‐organizing maps (SOM) compared the PARAFAC component proportions of leachate samples. Phenophase and species exerted much stronger influence on the determination of a sample's SOM placement than geographic origin. As expected, FDOM from all trees transitioned from more protein‐like components to more humic‐like components with senescence. Percent greenness of sampled leaves and the proportion of tyrosine‐like component 1 were found to be significantly different between the two genetic beech clusters, suggesting differences in photosynthesis and resorption. Our results highlight the need to account for interspecific and intraspecific variations in leaf litter leachate FDOM throughout autumn when examining the influence of allochthonous inputs to streams.
Key Points
Parallel factor analysis components of all leaf litter leachates shifted from more protein‐like to more humic‐like with senescence
Phenophase and species had a greater influence on the fluorescent dissolved organic matter than the geographic origin of beech trees
Behavior of the tyrosine‐like component differed significantly between two beech genetic clusters, suggesting differences in resorption
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