A test on Ellenberg indicator values in the Mediterranean evergreen woods (Quercetea ilicis)

The consistency and reliability of Ellenberg’s indicator values (Eiv) as ecological descriptors of the Mediterranean evergreen vegetation ascribed to the phytosociological class Quercetea ilicis have been checked on a set of 859 phytosociological relevés × 699 species. Diagnostic species were identified through a Twinspan analysis and their Eiv analyzed and related to the following independent variables: (1) annual mean temperatures, (2) annual rainfall. The results provided interesting insights to disentangle the current syntaxonomical framework at the alliance level demonstrating the usefulness of ecological indicator values to test the efficiency and predictivity of the phytosociological classification

How robust are community-based plant bioindicators? Empirical testing of the relationship between Ellenberg values and direct environmental measures in woodland communities

There are several community-based bioindicator systems that use species presence or abundance data as proxies for environmental variables. One example is the Ellenberg system, whereby vegetation data are used to estimate environmental soil conditions. Despite widespread use of Ellenberg values in ecological research, the correlation between bioindicated values and actual values is often an implicit assumption rather than based on empirical evidence. Here, we correlate unadjusted and UK-adjusted Ellenberg values for soil moisture, pH, and nitrate in relation to direct environmental measures for 50 woodland sites in the UK, which were subject to repeat sampling. Our results show the accuracy of Ellenberg values is parameter specific; pH values were a good proxy for direct environmental measures but this was not true for soil moisture, when relationships were weak and non-significant. For nitrates, there were important seasonal differences, with a strong positive logarithmic relationship in the spring but a non-significant (and negative) correlation in summer. The UK-adjusted values were better than, or equivalent to, Ellenberg’s original ones, which had been quantified originally for Central Europe, in all cases. Somewhat surprisingly, unweighted values correlated with direct environmental measures better than did abundance-weighted ones. This suggests that the presence of rare plants can be highly important in accurate quantification of soil parameters and we recommend using an unweighted approach. However, site profiles created only using rare plants were inferior to profiles based on the whole plant community and thus cannot be used in isolation. We conclude that, for pH and nitrates, the Ellenberg system provides a useful estimate of actual conditions, but recalibration of moisture values should be considered along with the effect of seasonality on the efficacy of the system

‘Friendship is a slow ripening fruit’: an agency perspective on water, values and infrastructure

This paper argues that human and material agents co-shape ‘morality’. Water systems will be discussed in more detail. Artefacts (technologies) relate humans and their worlds, but the specifics of this relationship become meaningful only within specific actor-networks. As such, the material influences the moral decisions of humans. Examples from the larger Mesopotamian area, on both state-led and community-managed water systems, are discussed to show that these result from activities of individuals, households and groups manipulating water fluxes in short time periods of hours and days. Analysis of these daily activities, and especially of how the material acts, offers options for archaeologists to trace morality in action.Water Resource

Contextualising seasonal climate forecasts by integrating local knowledge on drought in Malawi

Droughts and changing rainfall patterns due to natural climate variability and climate change, threaten the livelihoods of Malawi’s smallholder farmers, who constitute 80% of the population. Provision of seasonal climate forecasts (SCFs) is one means to potentially increase the resilience of rainfed farming to drought by informing farmers in their agricultural decisions. Local knowledge can play an important role in improving the value of SCFs, by making the forecast better-suited to the local environment and decision-making. This study explores whether the contextual relevance of the information provided in SCFs can be improved through the integration of farmers’ local knowledge in three districts in central and southern Malawi. A forecast threshold model is established that uses meteorological indicators before the rainy season as predictors of dry conditions during that season. Local knowledge informs our selection of the meteorological indicators as potential predictors. Verification of forecasts made with this model shows that meteorological indicators based on local knowledge have a predictive value for forecasting dry conditions in the rainy season. The forecast skill differs per location, with increased skill in the Southern Highlands climate zone. In addition, the local knowledge indicators show increased predictive value in forecasting locally relevant dry conditions, in comparison to the currently-used El Niño-Southern Oscillation (ENSO) indicators. We argue that the inclusion of local knowledge in the current drought information system of Malawi may improve the SCFs for farmers. We show that it is possible to capture local knowledge using observed station and climate reanalysis data. Our approach could benefit National Meteorological and Hydrological Services in the development of relevant climate services and support drought-risk reduction by humanitarian actors

The drop that makes a vase overflow: Understanding Maya society through daily water management

Water is an important key to understand Maya society, especially water availability within a context of climatic changes. Increasing drought would have pushed the Maya water systems into collapse. This paper studies the Maya water systems from an action‐oriented perspective, in order to understand what challenges the Maya had to overcome when dealing with water. The systems found at Tikal serve as main example, allowing comparisons with other Maya sites. In this analysis, hydraulic‐ and agent‐based elements are combined in a model to investigate the performance of the water system within extreme weather conditions and changing human agency. The results suggest that the Tikal water system was able to cope with most of the extreme situations. Furthermore, model results allow proposing that the Maya did not anticipate on short‐term changes in external conditions. Generally, in Tikal surpluses of water may have been as important as shortages of water. The extensive system of drains and canals present at Tikal may have been built to move water from the center of the city rather than to supply water to lower situated reservoirs during the dry season. Such a water‐removal system could be less centrally orientated and organized than is often argued. This could also mean that organizational structures of water systems of different city centers (Tikal, Calakmul, and Caracol) were more similar than usually assumed.Water Resource