The aim of the special issue “Interactions of Forests, Climate, Water Resources, and Humans in a Changing Environment” is to present case studies on the influences of natural and human disturbances on forest water resources under a changing climate. Studies in this collection of six papers cover a wide range of geographic regions from Australia to Nigeria with spatial research scale spanning from a tree leaf, to a segment of forest road, and large basins with mixed land uses. These studies clearly show the strong interactions among forests, global climate change, water quantity and quality, and human activities at multiple scales. Understanding the underlying processes of response of natural ecosystems and society to global climate change is essential for developing actionable science-based climate change mitigation and adaptation strategies and methodologies. Future research should focus on feedbacks among forests, climate, water, and disturbances, and interactions of ecohydrologic systems, economics and policies using an integrated approach.
It has been observed, in many Mediterranean countries, that human activities-engineering works, such as large dams and reservoirs construction (hydroelectric power dams, irrigation dams and water supply dams), artificial river diversion projects, channelization, etc., may seriously affect the environmental balance of inland and coastal ecosystems (forests, wetlands, lagoons, Deltas, estuaries and coastal areas). Dam constructions and their operation has modified the natural evolution trends of coastal areas to a considerable extent and has arguably been the most important factor controlling the evolution of the Greek coastal zone in recent decades. While an important factor of the destabilization of the ecological balance is the “climate change”, the role of “climatic cycles” is not negligible. Dams and reservoirs retain vast masses of water and sediments, thus adversely affecting water resources, the seasonal hydrological and hydrogeological regimes, while this disruption of water flow and sediment transport is able to generate changes on the supply of groundwater aquifers, on the emerging coastal erosion phenomena and consequently impacts on delta evolution and coastal ecosystems. Also, the creation of artificial lakes in forest areas and deforestation, contribute to increase emissions of CO2 and other greenhouse gases and climate change. The purpose of this study is to: a. describe the main man-made interferences (engineering works) which due to their nature and position, cause changes in the natural evolution of the hydro-geomorphological processes in the deltaic coastal zone of the rivers Nestos, Acheloos, Arachthos, Louros, Spercheios, Inois and Alfeios, in Greece, b. report a synthesis of the environmental and geomorphological studies of the areas under study, c. describe the geomorphological evolution of the selected areas and d. detect and evaluate the impacts of the above mentioned anthropogenic activities and the influence of “climate change” and affect the geomorphological evolution of the Greek coast.
Aims: We evaluated the responses of tree sap flow to wind speeds in coniferous and broad-leaved plants under steady and unsteady wind conditions. Study Design: We performed sap flow and micro-meteorological measurements on two conifers, Chamaecyparis obtusa var. formosana and Araucaria cunninghamii, and three broadleaved species, Swietenia mahagoni, Michelia formosana and Plumeria acutifolia in a wind tunnel. Place and Duration of Study: Civil Engineering Department, National Central University, Zhongli, Taiwan, China, between May and July 2011. Methodology: In a wind tunnel, wind speed was increased incrementally from 0 to 2, 4, 6, and 8 m s–1, then decreased from 8 to 0 m s–1. To examine how sap flow responded to unsteady wind, we estimated the time constant of each individual for each step change in wind speed. Moreover, we examined differences in transpiration rate and leaf conductance among individuals under stable wind speeds. Results: The time constant was generally about 30 min in both conifers and broadleaved individuals. Interestingly, under steady winds, transpiration rate showed two different response patterns to increased wind speed: linear and saturated. The two patterns may be a consequence of different stomatal conductance values, but not of different leaf shapes. Conclusion: Our results suggested that neither hydraulic system nor leaf shape differences between coniferous and broad-leaved trees was an ultimate factor affecting the transient response of tree sap flux and transpiration to wind speed, and that stomatal conductance played an important role in transpiration regulation in response to wind speed.
This study assessed the determinants of Choice of Indigenous Climate Related Strategies by Smallholder Farmers in Northern Ghana using primary data obtained through community focus group discussions and household survey, and subjected to the Multinomial Logit regression model. The empirical results reveal that presence of a market, informal credit from friends and relatives, location of farmer, farmer-to-farmer extension, noticing of a decrease in rainfall and noticing an increase in temperature influence the choice of indigenous climate related strategies. There is therefore the need to improve smallholder farmers’ access to market, agricultural extension services and their awareness of changes in rainfall and temperature.
Interest in forestation is rising with increasing recognition that global changes can negatively affect plant diversity and ecosystem function. It is known that forests influence climate through physical, chemical, and biological processes and ecohydrology need substantially more research. Functional interactions among vegetation, soils, and hydrologic processes permit the trees to maintain their symbioses in the soil. However, global change affects forests and soil health, influencing the population, diversity and activities of soil microbes, including symbiotic fungal populations. Although plants are sessile organisms, selected agroforestry tree species (mycorrhizal dependent plants) can be employed in forestation to encompass environmental stresses increased by global changes. This review was done to explore current information on forest for mitigating climate change, with respect to the research results on soil microbiota and its hydrologic impacts. Thus, relevant findings related to the benefits of soil health are emphasized. Accordingly, I discuss interdisciplinary knowledge required to understand the potential of forest to mitigate climate change.
Unsealed roads and tracks are acknowledged as the major sources of sediment pollution in forested catchments. In particular, road to stream connectivity via gullied pathways as well as via diffuse overland flow can contribute to significant fine sediment inputs to forest streams. At present in the State forests of New South Wales (NSW), Australia, road drainage spacings are determined on the basis of road slope. In this study forest road surveys were conducted across seven coastal catchments near Coffs Harbour on the sub-tropical NSW mid north coast to determine connectivity between gravel roads and streams via channelised and diffuse pathways under a range of rainfall intensities. A total of 10.82 km of representative road sections was assessed, comprising 129 relief pipes and 22 mitre drains. Of the 151 drains surveyed, gullies were evident at the outlets of 26 relief pipes (20.2%) but at none of the mitre drains. Relationships previously derived between contributing road length and hillslope gradient, and between contributing area and hillslope gradient adequately predicted thresholds of gully formation at drain outlets. During lower intensity storms with average recurrence intervals of 10 years or less, less than 20% of drains are connected to streams via overland flowpaths. However, the degree of diffuse connectivity increases when contributing area takes account of table drains and cut batters, as well as with increasing rainfall intensity. We conclude that when constructing new roads or reassessing drainage on existing roads in forest environments, in addition to preventing erosion of the road surface, gully formation and connectivity with streams via diffuse overland flow should be avoided. This requires factoring in contributing area, hillslope gradient at drain outlets and distance to the nearest stream. Preventing or reducing road-to-stream connectivity is essential for reducing impacts on water quality across all land tenures.
A study to assess changes in the physical and chemical properties of soil in timber saw mill dumpsite was carried out in Abakaliki between 2007 and 2008. Results showed that soil textural class remained sandy loamy. The lowest soil bulk density of 1.34 and 1.20 g cm-3 were obtained in the unburnt dumpsite in 2007 and 2008 resulting to 12% and 20% decline in 2007 and 2008 in the unburnt dumpsite relative to cropped land. The total porosity and gravimetric moisture content was a reverse of the soil bulk density. Higher total porosity and gravimetric moisture content were obtained in the unburnt and burnt dumpsites in that order relative to the fallow and cropped land. Infiltration rate followed the same trends as total porosity of the various sites. The lowest infiltration rate 15.02 and 35.82 mmhr-1 was observed in the cropped land. The soil pH decreased with depth in the dump and non-dumpsite but became strongly acid at 30 – 60 cm and 60 – 90 cm depths. The order of soil organic matter content was unburnt dumpsite > burnt dumpsite > fallow > cropped land. The available P and exchangeable K and Ca were highest in the burnt dumpsite. Heavy metals (Zn, Cu, Fe, and Pb) increased with time in the burnt and unburnt dumpsites but decreased in the cropped land. More concentration of heavy metals was observed in the 0 – 30 cm soil depth. The relative performance of maize grown on soils of the dump and non-dumpsites showed that there was better growth in the dump sites soils. However, the concentrations of heavy metals on tissue were found to be within normal range. Therefore, long term dumping of sawmill waste can influence soil properties and productivity.
The Perdido and Wolf Bay system in Alabama, USA, is an estuarine system linking the freshwater from the Perdido and Wolf Bay watersheds and the tidal saltwater from the Gulf of Mexico through Perdido Pass, Dolphin Pass, and the Gulf Intracoastal Waterway. A three dimensional hydrodynamic model using Environmental Fluid Dynamics Code (EFDC) was developed and used to analyze complex and dynamic flow, salinity, and temperature distributions in the system. The external driving forces for the model include the river discharges from natural and urban watersheds, atmospheric winds, and astronomical tidal elevations at the open boundaries where flow exchange takes place. Simulated water surface elevation, temperature, and salinity were compared against the field data at several observation stations in 2008 and 2009 with good agreement (coefficient of determination R2 = 0.92 between the measured and the modeled water surface elevations). The calibrated EFDC model was used to examine responses of the system to high, mean, and low inflows from streams and the sea level rise in the open boundaries under climate change. The concept of the age of water was applied to understand pollutant transport in the system. The age of water reveals dynamic and complex interactions between tides from the Gulf of Mexico and inflows from the streams. The age of water is less than 20 days under the 2-year high inflows and up to 160 days under 7Q10 low inflows. Under mean inflow conditions, the age of the tracer released from Wolf Bay is 50–70 days in the lower Perdido Bay and larger than that in the upper Perdido Bay, indicating a strong interaction between tides and inflows, which results in recirculation of flow and pollutants. The age of water is projected to increase up to 60 days under estimated sea level rise scenarios.