Water In Forests Research Articles

Baird’s Tapir (Tapirus bairdii) avoid human settlements and roads while searching for water in community-owned forests from the Calakmul region

Baird’s Tapir (Tapirus bairdii) avoid human settlements and roads while searching for water in community-owned forests from the Calakmul region

Carbon‐Water Tradeoffs in Old‐Growth and Young Forests of the Pacific Northwest

AbstractDespite much interest in relationships among carbon and water in forests, few studies assess how carbon accumulation scales with water use in forested watersheds with varied histories. This study quantified tree growth, water use efficiency, and carbon‐water tradeoffs of young versus mature/old‐growth forest in three small (13–22 ha) watersheds in the H.J. Andrews Experimental Forest, Oregon, USA. To quantify and scale carbon‐water tradeoffs from trees to watersheds, tree‐ring records and greenness and wetness indices from remote sensing were combined with long‐term vegetation, climate, and streamflow data from young forest watersheds (trees ∼45 years of age) and from a mature/old‐growth forest watershed (trees 150–500 years of age). Biomass production was closely related to water use; water use efficiency (basal area increment per unit of evapotranspiration) was lower; and carbon‐water tradeoffs were steeper in young forest plantations compared with old‐growth forest for which the tree growth record begins in the 1850s. Greenness and wetness indices from Landsat imagery were not significant predictors of streamflow or tree growth over the period 1984 to 2017, and soil C and N did not differ significantly among watersheds. Multiple lines of evidence show that mature and old‐growth forest watersheds store and accumulate more carbon, are more drought resistant, and better sustain water availability compared to young forests. These results provide a basis for reconstructions and predictions that are potentially broadly applicable, because first‐order watersheds occupy 80%–90% of large river basins and study watersheds are representative of forest history in the Pacific Northwest region.

Temporal dynamics of stomatal regulation and carbon- and water-related traits for a native tree species in low subtropical China.

Stomata are pivotal in modulating water and carbon processes within plants. However, our understanding of the temporal dynamics of water- and carbon-related traits, as influenced by stomatal behavior, remains limited. Here, we explore how stomatal regulation behavior and water- and carbon-related traits vary with changing environments by examining the seasonal variations in these traits of the native tree species Schima superba in low subtropical China. In February, April, and July of 2022, a series of water- and carbon-related traits were measured in the leaves and stems. The results showed that S. superba exhibited isohydric behavior in February when the soil dried out and vapor pressure deficit (VPD) was lower but anisohydric behavior in April and July when the soil was wetter and VPD was higher. In February, NSC and their components increased, and a relatively large contribution of soluble sugars to the change in NSC was observed. In the branches and phloem, NSC and their components displayed a relatively high monthly variability, suggesting their role in maintaining carbon balance within the trees. Conversely, the NSC in the leaves demonstrated minimal monthly variability. The specific leaf area, as well as the concentration of nitrogen (N) and phosphorus (P) per unit mass in leaves and the cumulative stem water release, exhibited a decrease with a reduction in soil water potential. Interestingly, the hydraulic conductivity remained consistent throughout this process. Furthermore, the relatively low monthly growth rate observed in February could suggest a carbon sink limitation. In conclusion, the increased NSC and decreased water status of S. superba under relatively stressed soil conditions indicated a trade-off between water and carbon storage. Our findings enhance our comprehension of the dynamics and regulation of water and carbon status in forests, thereby advancing the development of plant carbon and water process models under climate change scenarios.

The Importance of Enterococci in the Monitoring of Fecal Pollution in River Water in Forests and Urban Areas

The aim of this study was to determine the spatial distribution of enterococci as indicators of fecal pollution in river water in forest reserves and urban areas. The biodiversity, multidrug resistance, and virulence of enterococci were monitored using conventional and molecular methods, including fluorescence in situ hybridization (FISH). Enterococcal (ENT) counts determined via the FISH method were several thousand times higher than those determined by the culture-based method. This observation points to the abundance of viable but non-culturable (VBNC) bacteria that are often more toxic. Water from the river source was characterized by the lowest number of multidrug-resistant and virulent enterococcal strains. The abundance of the analyzed bacteria was highest (more than 50% of the strains) in the area where treated wastewater was evacuated to the river. Statistical analysis confirmed the presence of relationships between these environments. Pathogenic enterococci, which are not effectively eliminated during wastewater treatment, spread in the river continuum, thus posing a health threat to humans and animals. A combination of conventional and molecular techniques for the identification of bacteria supports a rapid and reliable assessment of pollution sources in the examined environment and the implementation of protective measures.

The Effect of Urbanization on The Stand Structure of A Mangrove Forest in Likas Bay, Sabah Malaysia

The aims of this study were to determine the effect of urbanization on species composition, change to stand structure and tree species on the mangrove stand between the housing development and the river. Two (2) plots were established, with five (5) subplots each measuring 10m x 10m. Simpson’s Index, Shannon-Weiner Index, Shannon evenness and Important Value Index (IVI) were used to determine the diversity and abundance of tree species. There are 4 species found in both plots which are Avicennia alba, Avicennia marina, Rhizophora mucronata and Rhizophora apiculata. The most abundant species is the R. apiculata with an IVI of 86.99 percent (%). The Simpson’s Index value calculated for the forest was 0.75, while the value for the Shannon-Weiner (H’) was 1.38. This indicates the area has low diversity in mangrove trees. The Shannon evenness (E) was 0.99. This means the area is completely covered in standing trees. In this study, the stand structure was measured using tree Diameter at Breast Height (DBH), height and crown size. The data indicates that mangrove trees approaching the housing developments experienced a steady decrease in DBH, height, and crown size. Trees in the middle of the forest had the largest DBH and height. The DBH and height of trees approaching the river steadily decreased but had larger crowns compared to the other subplots. Whereas, water quality and the presence of sediments were two other additional aspects used to measure the impact of housing developments on mangrove forests. Urbanization projects do not leave any noticeable impact on the clearness of water in mangrove forests, but does for sediments. As a conclusion, urbanization project such as housing development do leave an impact on mangrove forests in the Likas bay, Malaysia. More future studies will shed more light on how housing developments impact mangrove forests

Trading wood for water and carbon in peatland forests? Rewetting is worth more than wood production

While traditional forest management systems aim at maximizing timber production, sustainable forest management focuses on the multiple benefits of entire forest landscapes. The latter is now at the top of policy agendas. This calls for learning through evaluation to support the implementation of policies aiming towards multi-functional forest landscapes. The aim of this study is to quantify the economic trade-offs among natural, current, and re-wetted peatland forests using seven indicators, viz. drainage maintenance, rewetting, water retention, wood production, and three types of carbon sequestration as economic indicators. We discuss ways to adapt to and mitigate effect of forest draining on climate change toward securing multi-functional forest landscapes. The cost benefit analysis showed that in a potential natural state, Lithuania's peatland forests would deliver an economic benefit of ∼€176.1 million annually. In contrast, compared to natural peatland forests, the drainage of peatland forests for wood production has caused a loss of ∼€309 million annually. In comparison, peatland forest rewetting is estimated to increase the economic value by ∼€170 million annually. This study shows that satisfying different ecosystem services is a balancing act, and that a focus on wood production has resulted in net losses when foregone values of water storage and carbon sequestration are considered. Valuation of different sets of ecosystems service benefits and disservices must be assessed, and can be used as a tool towards creating, implementing and monitoring consequences of policies on both sustainability and biodiversity.

Regulation of Water Resources to Guarantee the Right to Availability of Water in the Karst Area of Maros-Pangkep, South Sulawesi, Indonesia

The Decree of the Minister of Forestry of the Republic of Indonesia, Number SK 398/Menhut-II/2004, dated October 18, 2004, converted the Maros Pangkep karst area to the Bantimurung-Bulusaraung National Park (Babul National Park). Karst and Babul National Park depend on rainwater absorbed by subsurface rivers. Babul National Park has integrated water management, although water supply and security are still threats. This study analyzes the harmonization and synergy of water policy with community requirements in the Maros-Pangkep Karst area, where residents rely largely on underground rivers. This study utilizes empirical legal research. (1) The Babul National Park manager distinguishes between the use of water as mass and as energy, and the surrounding community must seek for a permit for the latter. In the implementation process, the permission did not fully comply with the existing standards, notably the Minister of Environment and Forestry Number P.18/MENLHK/SETJEN/KUM.1/4/2019 governing the use of water and energy in wildlife sanctuaries, National Parks, Grand Forests, and Nature Tourism Parks. (2) Because legal enforcement hasn’t deterred forest destroyers, this will undermine forest conservation and the importance of forests in water management.

Rainfall interception measurements and modeling in a semiarid evergreen spruce (Picea crassifolia) forest

Rainfall interception is a critical source of water in arid and semiarid mountain forests. Interception loss (I) in mountain forests determines the ecohydrological function of a watershed, and this is particularly important in arid and semi-arid regions that rely on runoff yield to balance human and ecosystem water needs. Here, we measured gross rainfall (P), throughfall (Tf), and stemflow (Sf) from May 2020 to September 2021, and leaf area index (LAI), canopy structural parameters, and meteorological data within a Picea crassifolia (P. crassifolia) forest in the Qilian Mountains of northwestern China. Throughfall and canopy interception accounted for 56.4 and 35.2% of the 745.5 mm cumulative rainfall input during the two growing seasons, respectively. Stemflow of up to 13.6% of total rainfall events occurred when the amount of P > 30 mm, and canopy storage capacity (S) was 2.0 mm. Based on the parameters derived from a regression equation between Tf vs. P and a trial-and-error calibration scheme, three of the physical models, the Návar, reformulated Gash, and Liu, performed very well both for event-based (NSE > 0.8) and total-based (NSE > 0.92) I; a larger deviation was found during large rainfall events, especially for the reformulated Gash model. These results indicated that the power Návar and the reformulated Liu model are best for event-based and total-based I modeling, respectively, in spruce forests in this semi-arid region.

Pollution-Induced Changes in the Composition of Atmospheric Deposition and Soil Waters in Coniferous Forests at the Northern Tree Line

This study examines the dynamics of the composition of atmospheric precipitation and soil water in coniferous forests under the influence of atmospheric emissions from the Severonickel Copper–Nickel Smelter in Russia’s Murmansk region. We studied dwarf shrub-green moss spruce forests and lichen-shrub pine forests, the most common in the boreal zone. Our results showed a significant intra- (below and between the crowns) and inter-biogeocenotic (spruce and pine forests) variation in the composition of atmospheric precipitation and soil water in forests exposed to air pollution. The concentrations of main pollutants in atmospheric fallout and soil water are tens (sulfates) and hundreds (heavy metals) times higher than in the background areas and typically higher below the crowns. The long-term dynamics (between 1999 and 2020) of the composition of atmospheric fallout and soil water in coniferous forests in the background areas and defoliating forests demonstrates a significant increase in nickel concentrations in recent years. This may be due to an increase in nickel concentrations in aerosols propagating over considerable distances. In pollution-induced sparse forests, a trend was found toward a decrease in the concentration of pollutants, which may indicate a decrease in the fallout of pollutants in the composition of larger particles close to the smelter.

Spatio‐temporal variation in deep soil water use patterns of overstorey and understorey layers in subtropical plantations predicts community assembly

Abstract Deep soil water utilization allows plants to cope with drought stress. However, little is known about the roles of the understorey layers in driving spatio‐temporal variations of deep soil water in forests and how the patterns of deep soil water use among life‐forms contribute to community assembly processes. We assessed the spatio‐temporal patterns and determinants of deep water utilization of tree, shrub and herb layers in subtropical coniferous plantations and investigated associations between deep water use parameters and dominance and richness of understorey vegetation. We found that the understorey layer had a higher reliance on deep soil water in the dry season, a larger seasonal plasticity of deep soil water uptake, but lower spatial variability in deep soil water utilization than the tree layer. We showed that greater reliance of the tree layer on deep soil water was associated with decreased shrub layer diversity, whereas greater reliance of the shrub layer on deep water was associated with increased herb layer diversity. Synthesis. Our results highlight the roles of understorey layers in driving the temporal dynamics of deep soil water in forests and improve our understanding of how deep soil water use patterns among life‐forms shape community assembly in forests.

Functionally dissimilar neighbours increase tree water use efficiency through enhancement of leaf phosphorus concentration

Abstract Water use efficiency (WUE) is central to the global cycles of water and carbon. However, whether increasing tree diversity in forests can increase WUE remains poorly understood because the variation in WUE may result from multiple mechanisms acting concurrently. Disentangling their relative importance represents a major challenge. Here, we conducted a forest biodiversity experiment in subtropical China to assess the effects of neighbouring tree diversity on the foliar WUE of Cunninghamia lanceolata, a widespread tree plantation species in China. We measured foliar δ13C as a proxy for the change in intrinsic WUE. To disentangle the relative importance of water and nutrient‐mediated mechanisms in altering WUE, we determined foliar nutrient concentrations and foliar δ18O. Foliar δ18O was used as a surrogate for stomatal conductance and is known to be related to plant water use. Foliar WUE of focal trees increased with specific root length and leaf nitrogen content dissimilarities between focal trees and neighbours. The positive neighbourhood dissimilarity effect on foliar WUE was stronger under a more shaded neighbourhood. Foliar P concentration increased with neighbourhood specific root length dissimilarity. However, neither neighbourhood trait dissimilarities nor species richness significantly affect foliar δ18O. Results from structural equation model suggested that neighbourhood dissimilarity in specific root length indirectly enhanced foliar WUE and tree growth of focal trees via increasing foliar P concentration. Synthesis. Our results demonstrate the potential role of neighbourhood trait dissimilarity in modulating tree WUE in species‐rich communities. Our finding implies that the functional diversity of tree species at the local neighbourhood level has a fundamental ability to control water and nutrient cycles in forests.

Study of microplastics pollution in sediments and organisms in mangrove forests: A review

Microplastics (MP) are an emerging and lesser-known pollutant that has attracted the attention of researchers around the world in recent decades. Size of PM is smaller than 5 mm and can be entered in different ways into marine environments like mangrove forests and interfere with the health of the environment and organisms. The present study reviews 53 studies in the field of microplastics in different parts (sediments and organisms) of mangrove forests. About 26% of the 53 studies was published in 2020. In most studies, MP particles were categorized based on the shape, color, size, and polymer genus. The number of microplastics per kilogram of mangrove sediments has been reported as 1.22–6390. The effect of sediment texture on the frequency of microplastic particles and the relationship between sediment pH and MP abundance were also discussed. The fiber and bright color PMs were more common in living organisms (mollusks, crustaceans, and fish). The PM particles with different genus (polypropylene, polyethylene, polystyrene, and polyethylene terephthalate) were reported for sediment samples. In sediments with smaller sizes and lower pH, microplastics have been detected more frequently. It was reported that sediments and roots of mangrove forests act as livestock and retain microplastics for a long time. The highest concentration of MP in different parts of mangrove forests (sediment and organisms) has been reported for China. Few reports were observed on microplastics in water in mangrove forests. Also, the concentration of microplastics in sediments and organisms in mangrove forests exposed to fishing, coastal tourism, urban, and industrial wastewater was higher than those in pristine areas. It is necessary to conduct comprehensive studies to monitor, control, and evaluate the MP pollution in sediments and various organisms in mangrove forests worldwide.

Different drought responses of stem water relations and radial increments in Larix principis-rupprechtii and Picea meyeri in a montane mixed forest

The heterogeneous responses of mixed forests to climate change are integral to the promotion of the resilience and resistance of forest ecosystems, yet the hydraulic and growth sensitivity of mixed tree species to environmental drivers remain largely unexplored. In this study, stem radial variations in larch (Larix principis-rupprechtii) and spruce (Picea meyeri) were monitored using high-resolution point dendrometers over six years (2014–2019) in a mixed coniferous stand in semi-humid China. The extracted hourly tree water deficit-induced stem shrinkage (TWD) and stem radial increment (SRI) were compared between tree species and among years, and the species-specific responses of the daily maximum TWD and cumulative SRI to environmental variables were fitted by linear mixed models. Averagely, larch had a lower TWD and greater SRI rate than spruce in all six growing seasons. The interspecific differences in the TWD (length, magnitude, and intensity) were significant in dry years, while significant differences in the SRI rates were in wet years. The SRI rate of larch showed a more rapid decrease than that of spruce with increasing intensity of TWD. Furthermore, the TWD of both species was mainly regulated by vapor pressure deficit (VPD) and soil water content (SWC). The TWD of larch had a stronger and earlier response to VPD, while TWD of spruce was more affected by SWC (10 cm depth). The daily SRI of larch was more significantly related to all the measured environmental variables, indicating a more sensitive response to environmental drivers than that of spruce. We identified a shift in competitive advantage from sensitive L. principis-rupprechtii to conservative P. meyeri under extreme drought conditions, providing deep insights into species‐specific water and carbon dynamics in mixed forests.

Large Seasonal and Habitat Differences in Methane Ebullition on the Amazon Floodplain

AbstractTropical floodplains are an important source of methane (CH4) to the atmosphere, and ebullitive fluxes are likely to be important. We report direct measurements of CH4 ebullition in common habitats on the Amazon floodplain over two years based on floating chambers that allowed detection of bubbles, and submerged bubble traps. Ebullition was highly variable in space and time. Of the 840 floating chamber measurements (equivalent to 8,690 min of 10‐min deployments), 22% captured bubbles. Ebullitive CH4 fluxes, measured using bubble traps deployed for a total of approximately 230 days, ranged from 0 to 109 mmol CH4 m−2 d−1, with a mean of 4.4 mmol CH4 m−2 d−1. During falling water, a hydroacoustic echosounder detected bubbles in 24% of the 70‐m segments over 34 km. Ebullitive flux increased as the water level fell faster during falling water periods. In flooded forests, highest ebullitive fluxes occurred during falling water, while in open water and herbaceous plant habitats, higher ebullitive fluxes were measured during low water periods. The contribution of diffusive plus ebullitive CH4 flux represented by ebullition varied from 1% (high and rising water in open water of the lake) to 93% (falling water in flooded forests) based on bubble traps. Combining ebullitive and diffusive fluxes among habitats in relation to variations in water depth and areal coverage of aquatic habitats provides the basis for improved floodplain‐wide estimates of CH4 evasion.

Legacy Effects Following Fire on Surface Energy, Water and Carbon Fluxes in Mature Amazonian Forests

AbstractThe ongoing deforestation process in Amazonia has led to intensified forest fires in the region, particularly in Brazil, after more than a decade of effective forest conservation policy. This study aims to investigate the recovery of two mature sub‐montane ombrophile Amazonian forests affected by fire in terms of energy, water and carbon fluxes utilizing remote sensing (MODIS) and climate reanalysis data (GLDAS). These two forest plots, mainly composed of Manilkara spp. (Maçaranduba), Protium spp. (Breu) (∼30 m), Bertholletia excelsa (Castanheira) and Dinizia excelsa Ducke (Angelim‐Pedra) (∼50 m), occupy areas of 100.5 and 122.1 km2 and were subject to fire on the same day, on September 12, 2010. The fire significantly increased land surface temperature (0.8°C) and air temperature (1.2°C) in the forests over a 3 years interval. However, the forests showed an ability to recover their original states in terms of coupling between the carbon and water cycles comparing the 3‐year periods before and after the fires. Results from a wavelet analysis showed an intensification in annual and seasonal fluctuations, and in some cases (e.g., daily net radiation and evapotrasnspiration) sub‐annual fluctuation. We interpreted these changes to be consistent with overall intensification of the coupling of energy balance components and drivers imposed by climate and solar cycle seasonality, as well as faster time scale changes, consistent with a shift toward greater forest openness and consequent reduction in the interception of incoming solar radiation by the canopy.

The Multiscale TROPIcal CatchmentS critical zone observatory M‐TROPICS dataset III: Hydro‐geochemical monitoring of the Mule Hole catchment, south India

AbstractDespite the importance of tropical ecosystems for climate regulation, biodiversity, water and nutrient cycles, only a few Critical Zone Observatories (CZOs) are located in the tropics. Among these, most are in humid climates, while very few data exist for semi‐arid and sub‐humid climates, due to the difficulty of estimating hydro‐geochemical balances in catchments with ephemeral streams. We contribute to fill this gap by presenting a meteorological and hydro‐geochemical dataset acquired at the Mule Hole catchment (4.1 km2), a pristine dry deciduous forest located in a biosphere reserve in south India. The dataset consists of time series of variables related to (i) meteorology, including rainfall, air temperature, relative humidity, wind speed and direction, and global radiation, (ii) hydrology, including water level and discharge at the catchment outlet, (iii) hydrogeology, including manual (monthly) and/or automated (from 15 min to hourly) groundwater levels in nine piezometers and (iv) geochemistry, including suspended sediment content in the stream and chemical composition of rainfall (event based), groundwater (monthly sampling) and stream water (storm events, 15 min to hourly frequency with an automatic sampler). The time series extend from 2003 to 2019. Measurement errors are minimized by frequent calibration of sensors and quality checks, both in the field and in the laboratory. Despite these precautions, several data gaps exist, due to occasional access restriction to the site and instrument destruction by wildlife. Results show that large seasonal and interannual variations of climatic conditions were reflected in the large variations of stream flow and groundwater recharge, as well as in water chemical composition. Notably, they reveal a long‐term evolution of groundwater storage, suggesting hydrogeological cycles on a decadal scale. This dataset, alone or in combination with other data, has already allowed to better understand water and element cycling in tropical dry forests, and the role of forest diversity on biogeochemical cycles. As tropical ecosystems are underrepresented by Critical Zone Observatories, we expect this data note to be valuable for the global scientific community.

Estimation of Surface Canopy Water in Pacific Northwest Forests by Fusing Radar, Lidar, and Meteorological Data

Surface Canopy Water (SCW) is the intercepted rain water that resides within the tree canopy and plays a significant role in the hydrological cycle. Challenges arise in measuring SCW in remote areas using traditional ground-based techniques. Remote sensing in the radio spectrum has the potential to overcome the challenges where traditional modelling approaches face difficulties. In this study, we aim at estimating the SCW by fusing information extracted from the radar imagery acquired with the Sentinel-1 constellation, aerial laser scanning, and meteorological data. To describe the change of radar backscatter with moisture, we focused on six forest stands in the H.J. Andrews experimental forest in central Oregon, as well as four clear cut areas and one golf course, over the summers of 2015–2017. We found significant relationships when we executed the analysis on radar images in which individual tree crowns were delineated from lidar, as opposed to SCW estimated from individual pixel backscatter. Significant differences occur in the mean backscatter between radar images taken during rain vs. dry periods (no rain for >1 h), but these effects only last for roughly 30 min after the end of a rain event. We developed a predictive model for SCW using the radar images acquired at dawn, and proved the capability of space-based radar systems to provide information for estimation of the canopy moisture under conditions of fresh rainfall during the dry season.

Dissolved organic carbon and physicochemical variables of peat water in tropical peat swamp forests

Degradation of peatlands in Indonesia has been caused by fires, drainage, and deforestation of peat swamp forests. Fires release carbon dioxide (CO2) intensively but occasionally, whereas drainage enhances CO2 emission from the soil and dissolves organic carbon (DOC) leaching through peat water flow. DOC was affected not only by peat degradation but also by the physicochemical variables of peat water. A study on DOC and physicochemical variables of peat water to investigate the effects of drainage and fires has been conducted in three tropical peat swamp forests of Central Kalimantan. They were a relatively intact peat swamp forest with little drainage (UF), a drained peat swamp forest (DF), and a drained, burnt peat swamp forest (DB). The DOC concentration was analyzed using a total organic carbon (TOC) analyzer, while physicochemical variables, including electrical conductivity (EC), pH, and inorganic nitrogen were measured using EC meter, pH meter, and ion analyzer, respectively. Research results showed that the highest DOC concentration was measured in DF, whereas the lowest DOC concentration was in DB. DOC was resulted from peat decomposition due to low pH, low C/N, and high EC conditions. These results indicate that DOC leaching through peat water flow may occur by drainage rather than fires.

Comparisons of flux-based stemflow enrichment ratios for two Quercus spp. within the megalopolis of the eastern USA

Throughfall and stemflow serve as two important transport mechanisms for water and solutes in urban forests, though these fluxes are seldom quantified within cities. This study is the first to utilize two flux-based enrichment ratios for stemflow to characterize spatial patterns in water and solute distribution in urban forest fragments. Using event-based, in situ sampling, this study quantified stemflow enrichment for Quercus rubra (northern red oak) and Quercus alba (white oak) trees relative to open precipitation (EP,B) and throughfall (ET,B) per unit trunk basal area for dissolved Ca, K, Mg, Mn, NO3-N, and S. The study investigated variability in nutrient enrichment at the fragment, municipal, and regional scales. Among all solutes, observations for EP,B and ET,B for Q. rubra and Q. alba were generally lowest for Mg and highest for Mn and K. Significant intra-urban variability in stemflow enrichment was limited to EP,B of K and ET,B of Ca (p < 0.05), while trans-regional variability in stemflow enrichment consistently indicated higher EP,B and ET,B in more highly developed portions of the study region. At the fragment scale, EP,B and ET,B for Q. rubra was consistently higher than for Q. alba, with variability in these observations significant for all solutes. For example, interspecific variability in EP,B was greatest for K, where median values ranged from 2.8 ± 29.7 in Q. alba to 87.1 ± 97.1 in Q. rubra. While observations for ET,B were generally lower than those for EP,B, observations for Q. rubra also consistently exceeded those for Q. alba, with median values for K ranging from 1.5 ± 0.5 to 21.9 ± 3.1 for Q. alba and Q. rubra, respectively. Findings were likely driven by variability in biophysical characteristics between the two species (e.g., bark morphology). Further, findings indicate that species heterogeneity within the urban forest contributes to significant variability in nutrient (and possibly pollutant) transport and fate via throughfall and stemflow below the canopy, with subsequent impacts on urban forest biogeochemistry.

Effects of stand variables on stemflow and surface runoff in pine-oak forests in northern Mexico

The flow of water in temperate forests depends on the amount of precipitation, type of soil, topographic features, and forest cover, among other factors. Unlike the first three, forest cover can be modified by silvicultural treatments, the effects of which manifest in the quality and quantity of water, as well as in the transport of sediments and soil nutrients. The objective of this study was to analyze the effect of some stand variables on surface runoff and stemflow in pine-oak forests of northern Mexico. The stand variables included tree diameter at breast height, basal area, canopy cover, and volume. They were collected in eight 0.1-ha circular plots, measured in 2016 and re-measured in 2018. Nonlinear quantile regression was used to determine the best-fit relationships between the variables. Results indicated that surface runoff was most closely and inversely related to basal area. Stemflow was related to diameter at breast height, while showing no statistical significance. A stemflow funneling ratio did show an inverse, statistically-significant relationship with diameter at breast height. These results can help determine best forest management regimes compatible with the quantity and quality of water fluxes in this type of ecosystem.