Clay minerals as a soil potassium reservoir: observation and quantification through X-ray diffraction

Potassium (K) is a major element for plant growth. The K⁺ ions fixed in soil 2:1 clay mineral interlayers contribute to plant K nutrition. Such clay minerals are most often the majority in temperate soils. Field and laboratory observations based on X-ray diffraction techniques suggest that 2:1 clay minerals behave as a K reservoir. The present work investigated this idea through data from a replicated long term fertilization experiment which allowed one to address the following questions: (1) Do fertilization treatments induce some modifications (as seen from X-ray diffraction measurements) on soil 2:1 clay mineralogy? (2) Are soil 2:1 clay mineral modifications related to soil K budget in the different plots? (3) Do fertilizer treatments modify clay Al, Si, Mg, Fe or K elemental content? (4) Are clay mineral modifications related to clay K content modifications? (5) Are clay mineral changes related to clay Al, Si, Mg or Fe content as well as those of K content? Our results showed that K fertilization treatments considered in the context of soil K budget are very significantly related to 2:1 soil clay mineralogy and clay K content. The 2:1 clay mineral modifications observed through X-ray measurements were quantitatively correlated with chemically analyzed clay K content. Clay K content modifications are independent from clay Al, Si, Mg or Fe contents. These results show that the soil chemical environment can modify interlayer site occupations (illite content) which suggests that high level accumulation of potassium can occur without any modification of the clay sheet structure. This study therefore validates the view of 2:1 clay minerals as a K reservoir easily quantifiable through X-ray observations.     

Birds as indicators of wetland status and change in the North Rupununi,Guyana

In financially and human capacity poor countries, there is an important need to monitor the status of resource rich ecosystems in the face of growing extractive activities in simple and inexpensive ways. In this study we explore the potential of using birds as indicators of ecosystem change in the wetland systems of the North Rupununi, Guyana, where local communities rely heavily on wetland resources for their subsistence activities. This is done by (1) assessing what environmental factors determine bird communities at different spatial and temporal scales; and (2) identifying indicator groups and/or species for ecosystem status. We surveyed 31 wetland sites over 2 years, taking monthly recordings of both the environmental features of waterbodies using a modified version of the River Habitat Survey and bird species counts. Using multivariate analyses, we found that large-scale habitat type, namely forest and savanna, and waterbody type, namely pond or main river channel, were the main factors affecting bird species distribution. At the smaller scale, habitat features around the waterbody and seasonality become important factors. We were able to identify lists of bird species associated with different waterbody types, and we present this as a checklist for future monitoring. We hope these findings can be integrated into the adaptive management and sustainable livelihood goals of the local stakeholders through linking monitoring with tourism and local school curriculum activities.     

A metabolic view of the diversity-stability relationship

A theoretical analysis of the “portfolio effect” expressed in metabolic terms indicates that the coefficient of variation of total biomass in the ecosystem is influenced by three factors: metabolic diversity, total population size and organism biomass (body mass). The contribution of these factors to ecosystem stability depends on the power scaling of population size to its temporal variance: the Tilman's z. In natural populations, 1<z<2 both from a theoretical and an empirical background, and so a higher metabolic diversity, a larger population size and a bigger body mass are expected to increase ecosystem stability. The maximization of any of these factors will enhance ecosystem stability both at ecological (successional) and evolutionary timescales, which could explain a number of trends observed in ecosystems and in the history of life.     

Analysis and management of multiple ecosystem services within a social-ecological context

The assessment of ecosystem services (ESS) requires approaches that are capable to deal with the complexity of social-ecological systems (SES). A new viewpoint is proposed, in which the social-ecological perspective of Ostrom’s SES framework is used to describe the flow of ESS, through the identification of the social and ecological elements involved. Two types of ESS flow emerge from this analysis, depending on the way in which the elements of ESS supply (resource system and resource units) and demand (actors) interact: (i) a “direct flow type” in which the resource units deliver the ESS through some specific ecological functions (e.g. wetlands providing carbon sequestration), and (ii) a “mediated flow type” in which the resource units become themselves the ESS when “used” by means of human activities (e.g. fish harvested through fishing activities). The identification of activities is crucial to understand the interactions between ESS, because of the feedbacks they produce on the ecosystem functioning and thus on the provision of the same or other ESS. In addition, these feedbacks can depend on temporal aspects of ESS provision. On these regards, a hypothesis is proposed according to which a time lag can exist between the ESS supply-side and flow in human-modified SES. Altogether, this social-ecological analysis of ESS can contribute to focus the management strategies on the control of impacting activities and on the maintenance of those processes which underpin ESS’ provision, thus contributing to the implementation of an ecosystem-based management of SES. These aspects are discussed in the light of the Venice lagoon example.     

植物过程对土壤有机碳含量的影响

从全球和生态系统角度,综述了植物过程对土壤有机碳含量的影响和可能的作用机理,揭示了植物过程对土壤有机碳的源和汇的影响及对土壤有机碳的动态影响,讨论了植物过程对土壤有机碳影响研究的任务和发展前景,及减少土壤表层向空气呼出CO₂的数量、维持现时的生态平衡的途径,指出了植物过程影响土壤有机碳的研究方向和有待解决的问题.增加植物生物量,可以增加土壤有机碳贮量.     

Using business names as an indicator of oysters’ cultural value

Business names, as recorded by state tax departments, offer a possible indicator of cultural ecosystem services provided by nearby natural resources. Using oysters in the Chesapeake Bay as an example, we process spatial and quantitative analyses that can potentially identify cultural value for integration into monitoring efforts that aim to incorporate a variety of ecosystem services. Businesses named directly after oysters provide a useful lens to capture the many reasons people value oysters culturally, but also provide an easy aggregate indicator that could potentially be added to regular regional monitoring programs in order to factor in cultural value to adaptive management policies.     

Developing and quantifying indicators of organic farming using analytic hierarchy process

Although regulations and criteria relating to organic farming are clearly defined by the relevant agencies, especially by IFOAM, some have been overshadowed by attention to others and have lost their significance over time. The aim of this study was to develop and quantify organic farming indicators to determine the relative importance of each. The desired indicators were collected during a literature review of scientific resources about the principles of organic farming. These indices were classified into four categories and their weights were determined through interviews with experts on organic agriculture, including university professors, agroecology students, Ministry of Agriculture experts, organic farming inspectors and organic farmers. The analytic hierarchy process (AHP) was used for this purpose. The results showed that pest and disease management, yield, soil nutrient management, water consumption rate, chemical fertilizer consumption rate and the use of transgenic materials having weights of 0.16, 0.098, 0.096, 0.08, 0.071 and 0.059, respectively, and are the most important indicators for development and assessment of organic farming. In this as well as similar studies, the weight of indicators associated with consumption of chemical fertilizers and pesticides were relatively high. This indicates the importance of rules related to the use of chemicals in organic farming; however, each index has a certain weight and none can be overlooked. All indicators should be considered as an inseparable set and all should be used in the development of organic farming. The results of this study can be useful for both inspection bodies and organic farmers. Farmers can reduce the risks associated with transitioning to organic farming and minimize the probability of failure by monitoring these indicators in their fields.     

Developing a regional diatom index for assessment and monitoring of freshwater streams in sub-tropical Australia

The use of borrowed indices to assess stream health has limitations and research suggests a need to develop more reliable regionally based indices that are sensitive to the relationship between taxa and environmental conditions. Implementing this is challenging in the Southern Hemisphere given the scarcity of diatom indices, specifically in sub-tropical areas. The purpose of this study was to develop a regionally based diatom index to assess freshwater lotic systems in sub-tropical eastern Australia and compare the results with borrowed indices to derive meaningful inferences on river health. A total of 119 epilithic diatom and water samples were collected during 2014–2015 from the Richmond River Catchment in Northern NSW Australia. Statistical analysis indicated that total phosphorus (TP) and total nitrogen (TN) were strong variables influencing the data set and subsequently TP was chosen as a nutrient proxy for the index. Analysis of diatoms resulted in TP sensitivity values (1–5) being assigned to 105 species with relative abundance of >1% in the data set. These species were used to calculate the Richmond River Diatom Index (RRDI) for 45 sites within the Catchment. The index effectively scored sites along the environmental gradient with sites in the upper catchment generally scoring lower (healthier) than the mid and lower catchment sites. The index compared positively with both the Diatom Species Index for Australian Rivers (DSIAR) (r = 0.76) and the Trophic Diatom Index (TDI) (r = 0.65). Further research is suggested to test the RRDI on independent sites in neighbouring catchments and develop class boundaries from the RRDI so that the index can be readily used by water managers to assess and monitor freshwater systems in sub-tropical Australia.