Tropical forest systems: A hydrological approach

This paper briefly examines the importance of considering the rates and magnitudes of water movement in the hillslope-river system of a tropical rainforest catchment. It is proposed that consideration of water movement is a fundamental component in understanding the release and movement of nutrients in this environment. In any such analysis it is essential that the 'opportunity time' or 'residence time' together with the availability of weatherable minerals be considered. Three conditions are suggested to account for the low solute concentrations in stream waters, each, any or all three of which may occur. (1) If there are no soil nutrients of importance then there can be supply neither to the river nor the plants. (2) If the residence time is too short relative to the equilibriation time of the minerals, then weathering and exchange may not occur. (3) If the residence time is too long (because rate of movement is slow), the 'turnover' will be small. In this context the analogy of an overflowing cup is discussed as a possible explanation of low solute concentrations. The results presented in the paper refer to the period 6th - 26thMay 1977, from a small hillslope-river segment at Resewa Ducke, Amazonas. Measurements made included soil tension, piezometric levels, river stage, infìltration rates and wetting front movement. Using Darcy's Law, water fluxes are determined. Draw down characteristics of the piezometers and river stage have been estimated using regressions of the logarithms of both these variables against the logarithm of time. The results suggest that during the period of observation the slope is almost saturated with respect to water. Actual saturation (positive pressures) are observed to occur at the foot of the slope under all conditions and within the slope during the earliest set of observations. Results from the computation of water fluxes indicate little lateral movement, the dominant flow is at or very close to vertical. Analysis of piezometer level and river stage suggests a very close link between the two, with only limited influence from the adjacent hillslope. In conclusion it seems that during the wet season, most of the river flow is generated by rapid rise beneath the floodplain and the slope immediately adjacent to the floodplain as a direct result of rainfall infiltration and that throughflow is unimportant. This is consistent with certain aspects of the cup analogy and goes far to explain the very low solute concentration found in the water of this and similar barrancos

Corrigendum to “Identifying ancient water availability through phytolith analysis: An experimental approach” (Identifying ancient water availability through phytolith analysis: An experimental approach (2016) 73 (82–93), (S0305440316300930), (10.1016/j.jas.2016.07.006))

© 2019 The Author(s) The authors regret an error in the paper that does not affect the efficacy of the method. In the paper, we state that the ratio of phytolith forms calculated is the ratio of fixed (short) to sensitive (long) forms when in fact what is calculated is the ratio of sensitive to fixed forms. The authors would like to apologise for any confusion caused

Threats to the Soil Resource Base of Food Security in China and Europe. A report from the Sino-EU Panel on Land and Soil

To secure adequate food supply is the major challenge for humanity in the 21st century. Growing world population and its urbanization put pressure on this basic need, which is further threatened by the constant loss of fertile land. The assessment of sustainability of food supply under increasing pressure on land resources has been selected as one of the most important priority topics of the activities of Sino-EU Panel on Land and Soil (SEPLS). The Panel has performed a number of related researches and discussed the results on a scientific seminar in January 2012 in Nanjing, China. This report is an output of this seminar with a summary of the structured discussions on the below issues. 1. Urban and peri-urban development (soil sealing and loss of land functions) Urbanization and the linked spread of infrastructural development mean sealing of soil surfaces. Soil sealing is the most rapidly growing limitation for soil functions (including biomass production function) both in China and Europe. Soil sealing in China has been taking dramatic degree in the last two decades and the process is estimated to continue in the coming period as well. While urban and peri-urban development is looked as a necessity for social development, its negative effect on natural resources are inevitable. 2. Land degradation Despite the widely recognized importance of land degradation in the unsustainability of economic development and implementation of various policies to halt degradation (e.g. green for grain programme in China; cross-compliance measures in the EU), loss of land productivity by degradation is an ongoing process both in China and the EU. Major forms of soil degradation (erosion, desertification, landslides etc.) are similar in both regions. Assessment of the causes and consequences of soil degradation processes in relation to policy actions is highlighted among the priorities of the SEPLS. 3. Intensive agriculture and multi-function management of land resources Intensification and extensification in agriculture can be considered as the main changes in land use in rural areas in both EU and China. While agricultural intensification is one of the greatest threats to the soil and environment and then hampers the sustainable development of agriculture and food security. To meet this challenge, sustainable management of multi-functionality of land resources is undoubtedly an effective strategy, in which the EU has a good expertise. Bilateral exchange of the experience and knowledge benefits the sustainable management of land resources.JRC.H.5-Land Resources Managemen

Change in physical properties of ferralsols with tree planting in the Central Amazon, Brazil

We examined the effects of mixed planting of fast growing tree species with indigenous Amazon tree species and soil tillage practices on soil physical properties in a deforested site used for agricultural cultivation. The site was located in the Central Amazon and consisted of Ferralsols. Bulk density and soil hardness were compared in the mixed planting site and an area where only indigenous tree species were planted. Many roots of the fast growing trees penetrated into the profile and caused changes in soil physical properties, i.e., decreasing bulk density and hardness. When tillage practices prior to planting were combined with mixed planting, the changes in soil physical properties were enhanced and the growth of not only the planted fast growing trees but also indigenous species such as mahogany, Swietenia macrophylla, which is shade tolerant, was accelerated

Environmental risk assessments for transgenic crops producing output trait enzymes

The environmental risks from cultivating crops producing output trait enzymes can be rigorously assessed by testing conservative risk hypotheses of no harm to endpoints such as the abundance of wildlife, crop yield and the rate of degradation of crop residues in soil. These hypotheses can be tested with data from many sources, including evaluations of the agronomic performance and nutritional quality of the crop made during product development, and information from the scientific literature on the mode-of-action, taxonomic distribution and environmental fate of the enzyme. Few, if any, specific ecotoxicology or environmental fate studies are needed. The effective use of existing data means that regulatory decision-making, to which an environmental risk assessment provides essential information, is not unnecessarily complicated by evaluation of large amounts of new data that provide negligible improvement in the characterization of risk, and that may delay environmental benefits offered by transgenic crops containing output trait enzymes