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Forests, Water and People in the Humid Tropics: Past, Present and Future Hydrological Research for Integrated Land and Water Management
This volume is a comprehensive review of the hydrological and physiological functioning of tropical rain forests, the environmental impacts of their disturbance and conversion to other land uses, and optimum strategies for managing them. It will be invaluable for specialists, managers and practitioners, scientists and advanced students.
eBook
The water absorbability of beech (Fagus sylvatica l.) and fir (Abies alba mill.) organic matter in the forest floor
The organic horizons of forest soils are characterised by double capillarity: between particles and inside them. It has been hypothesized that the time required to fill the internal capillarity of organic particles depends on their botanical origin and the degree of their decomposition. The aim of the present study is to determine the time of water absorption by organic matter that is part of the Ol and Ofh horizons of selected beech (Fagus sylvatica L.) and fir (Abies alba Mill.) stands. The present research on water absorbability lasted for 14 days and consisted in measuring the absorption time in organic particles from the moment of immersion of an air-dry sample in water until the particles soaked in water exceeded the density of 1.0 g·cm-3.  It was found that in fir organic matter the time of water absorption decreases with the advancement of decomposition. In beech stands, progressing decomposition processes result in a longer water absorption time. The dynamics of water absorption of organic matter indicates that no single rainfall is able to entirely fill the internal capillarity of organic particles, whereby the organic horizons of forest soils can maintain the ability to retain water even in long-term rainfall.
Journal Article
Forests and Water Yield: A Synthesis of Disturbance Effects on Streamflow and Snowpack in Western Coniferous Forests
Abstract
Abstract
In coniferous western forests, recent widespread tree mortality provided opportunities to test the long-held theory that forest cover loss increases water yield. We reviewed 78 studies of hydrologic response to standing-replacing (severe wildfire, harvest) or nonstand-replacing (drought, insects, low-severity wildfire) disturbances, and reassessed the question: Does water yield or snowpack increase after forest disturbance? Collective results indicate that postdisturbance streamflow and snowpack may increase, not change, or even decrease, and illuminate factors that may help improve predictability of hydrologic response to disturbance. Contrary to the expectation that tree mortality reduces evapotranspiration, making more water available as runoff, postdisturbance evapotranspiration sometimes increased—particularly following nonstand-replacing disturbance—because of (a) increased evaporation resulting from higher subcanopy radiation, and (b) increased transpiration resulting from rapid postdisturbance growth. Postdisturbance hydrologic response depends on vegetation structure, climate, and topography, and new hypotheses continue to be formulated and tested in this rapidly evolving discipline.
Journal Article
Patterns and Dynamics of Dissolved Organic Carbon (DOC) in Boreal Streams: The Role of Processes, Connectivity, and Scaling
We bring together three decades of research from a boreal catchment to facilitate an improved mechanistic understanding of surface water dissolved organic carbon (DOC) regulation across multiple scales. The Krycklan Catchment Study encompasses 15 monitored nested research catchments, ranging from 3 to 6900 ha in size, as well as a set of monitored transects of forested and wetland soils. We show that in small homogenous catchments, hydrological functioning provides a first order control on the temporal variability of stream water DOC. In larger, more heterogeneous catchments, stream water DOC dynamics are regulated by the combined effect of hydrological mechanisms and the proportion of major landscape elements, such as wetland and forested areas. As a consequence, streams with heterogeneous catchments undergo a temporal switch in the DOC source. In a typical boreal catchment covered by 10-20% wetlands, DOC originates predominantly from wetland sources during low flow conditions. During high flow, the major source of DOC is from forested areas of the catchment. We demonstrate that by connecting knowledge about DOC sources in the landscape with detailed hydrological process understanding, an improved representation of stream water DOC regulation can be provided. The purpose of this study is to serve as a framework for appreciating the role of regulating mechanisms, connectivity and scaling for understanding the pattern and dynamics of surface water DOC across complex landscapes. The results from this study suggest that the sensitivity of stream water DOC in the boreal landscape ultimately depends on changes within individual landscape elements, the proportion and connectivity of these affected landscape elements, and how these changes are propagated downstream.
Journal Article
A review of climate-change impact and adaptation studies for the water sector in Thailand
Thailand plays a central economic and policy-making role in Southeast Asia. Although climate change adaptation is being mainstreamed in Thailand, a well-organized overview of the impacts of climate change and potential adaptation measures has been unavailable to date. Here we present a comprehensive review of climate-change impact studies that focused on the Thai water sector, based on a literature review of six sub-sectors: riverine hydrology, sediment erosion, coastal erosion, forest hydrology, agricultural hydrology, and urban hydrology. Our review examined the long-term availability of observational data, historical changes, projected changes in key variables, and the availability of economic assessments and their implications for adaptation actions. Although some basic hydrometeorological variables have been well monitored, specific historical changes due to climate change have seldom been detected. Furthermore, although numerous future projections have been proposed, the likely changes due to climate change remain unclear due to a general lack of systematic multi-model and multi-scenario assessments and limited spatiotemporal coverage of the study area. Several gaps in the research were identified, and ten research recommendations are presented. While the information contained herein contributes to state-of-the-art knowledge on the impact of climate change on the water sector in Thailand, it will also benefit other countries on the Indochina Peninsula with a similar climate.
Journal Article
Event controlled DOC export from forested watersheds
We performed a meta-data analysis to investigate the importance of event based fluxes to DOC export from forested watersheds. A total of 30 small eastern United States forested watersheds with no wetland component, with a total of 5,176 DOC and accompanying discharge measurements were used in this analysis. There is a clear increase in DOC concentration during hydrologic events (storms and snow melt) that follows a power relationship. We estimate that 86% of DOC is exported during events. The majority (70%) of this event based DOC flux occurs during the rising hydrograph and during large events. Events with a discharge greater than 1.38 cm day⁻¹ make up only 4.8% of the annual hydrograph, yet are responsible for 57% of annual DOC flux. The relationship between event discharge and both DOC concentration and flux is also regulated by temperature and antecedent conditions, with a larger response in both fluxes and concentrations to events during warmer periods and periods where the preceding discharge was low. The temperature relationship also shows seasonality indicating a potential link to the size or reactivity of watershed OM pools. The 86% of DOC lost during events represents a conservative estimate of the amount of allochthonous forested DOC transported laterally to streams. Future research on watershed cycling of DOC should take into account the importance of events in regulating the transport of DOC to downstream ecosystems, determine the relative importance of abiotic versus biotic processes for the temperature regulation of event-associated DOC fluxes, and elucidate the interactions between processes that respond to climate on event versus longer time scales.
Journal Article
Hydrologic effects of a changing forest landscape
Of all the outputs of forests, water may be the most important. Streamflow from forests provides two-thirds of the nation's clean water supply. Removing forest cover accelerates the rate that precipitation becomes streamflow; therefore, in some areas, cutting trees causes a temporary increase in the volume of water flowing downstream. This effect has spurred political pressure to cut trees to increase water supply, especially in western states where population is rising. However, cutting trees for water gains is not sustainable: increases in flow rate and volume are typically short-lived, and the practice can ultimately degrade water quality and increase vulnerability to flooding. Forest hydrology, the study of how water flows through forests, can help illuminate the connections between forests and water, but it must advance if it is to deal with today's complexities, including climate change, wildfires, and changing patterns of development and ownership. This book identifies actions that scientists, forest and water managers, and citizens can take to help sustain water resources from forests.
eBook
Forests, water, and people in the humid Tropics : past, present, and future hydrological research for intergrated land and water management
Forests, Water and People in the Humid Tropics is a comprehensive review of the hydrological and physiological functioning of tropical rain forests, the environmental impacts of their disturbance and conversion to other land uses, and optimum strategies for managing them. The book brings together leading specialists in such diverse fields as tropical anthropology and human geography, environmental economics, climatology and meteorology, hydrology, geomorphology, plant and aquatic ecology, forestry and conservation agronomy. The editors have supplemented the individual contributions with invaluable overviews of the main sections and provide key pointers for future research. Specialists will find authenticated detail in chapters written by experts on a whole range of people-water-land use issues, managers and practitioners will learn more about the implications of ongoing and planned forest conversion, while scientists and students will appreciate a unique review of the literature.
eBook
Widespread Increase of Tree Mortality Rates in the Western United States
Persistent changes in tree mortality rates can alter forest structure, composition, and ecosystem services such as carbon sequestration. Our analyses of longitudinal data from unmanaged old forests in the western United States showed that background (noncatastrophic) mortality rates have increased rapidly in recent decades, with doubling periods ranging from 17 to 29 years among regions. Increases were also pervasive across elevations, tree sizes, dominant genera, and past fire histories. Forest density and basal area declined slightly, which suggests that increasing mortality was not caused by endogenous increases in competition. Because mortality increased in small trees, the overall increase in mortality rates cannot be attributed solely to aging of large trees. Regional warming and consequent increases in water deficits are likely contributors to the increases in tree mortality rates.
Journal Article