Indicators of environmentally sound land use in the humid tropics: The potential roles of expert opinion,knowledge engineering and knowledge discovery

Despite abundant literature on indicators for sustainable resource management, practical tools to help local users to apply its general concepts at a local to regional level are scarce. This means that decisions over land evaluation and land use at a local level are often not based on the formal application of indicators or decision support systems for environmentally sound management but instead on the opinion of local expertise, for instance forest managers, cattle breeders, farmers and/or academics. This is particularly seen to be the case in the tropics where access to modern communication and information technologies is restricted.As the opinions of experts are often based on and influenced by personal experience, intuition, heuristics and bias, their evaluations and decision are often unclear to the non-expert working at a local level. In order to make their reasoning more comprehensible to the non-expert, the ecological condition of 176 plots in the tropical Southeast of Mexico were evaluated by experts on soil fertility, forest management, cattle breeding and agriculture. With the assistance of a knowledge engineer (one who converts expert knowledge and reasoning into a model), these expert opinions and reasoning were then translated into a formal computer model.As an alternative approach we applied a knowledge discovery technique, namely the induction of regression trees and automatically developed models using the expert evaluations as training data. Where knowledge engineering was tedious and time consuming, regression models could be rapidly generated. Moreover, the correspondence between regression trees and expert opinions was considerably higher than the correspondence between expert opinion and their own models. The regression trees used less explicative variables than the models generated by the experts. The minimisation of sampling effort due to variable space reduction means that the application of regression tree induction has a high potential for a rapid development of indicators for narrowly defined ecological assessments, needed for decision making on a local or regional scale.     

A Multi-Criteria Index for Ecological Evaluation of Tropical Agriculture in Southeastern Mexico

The aim of this study was to generate an easy to use index to evaluate the ecological state of agricultural land from a sustainability perspective. We selected environmental indicators, such as the use of organic soil amendments (green manure) versus chemical fertilizers, plant biodiversity (including crop associations), variables which characterize soil conservation of conventional agricultural systems, pesticide use, method and frequency of tillage. We monitored the ecological state of 52 agricultural plots to test the performance of the index. The variables were hierarchically aggregated with simple mathematical algorithms, if-then rules, and rule-based fuzzy models, yielding the final multi-criteria index with values from 0 (worst) to 1 (best conditions). We validated the model through independent evaluation by experts, and we obtained a linear regression with an r² = 0.61 (p = 2.4e-06, d.f. = 49) between index output and the experts’ evaluation.     

The response of soil microorganisms and roots to elevated CO2 and temperature in a terrestrial model ecosystem

We investigate the response of soil microorganisms to atmospheric CO2 and temperature change within model terrestrial ecosystems in the Ecotron. The model communities consisted of four plant species (Cardamine hirsuta, Poa annua, Senecio vulgaris, Spergula arvensis), four herbivorous insect species (two aphids, a leaf-miner, and a whitefly) and their parasitoids, snails, earthworms, woodlice, soil-dwelling Collembola (springtails), nematodes and soil microorganisms (bacteria, fungi, mycorrhizae and Protista). In two successive experiments, the effects of elevated temperature (ambient plus 2 °C) at both ambient and elevated CO2 conditions (ambient plus 200 ppm) were investigated. A 40:60 sand:Surrey loam mixture with relatively low nutrient levels was used. Each experiment ran for 9 months and soil microbial biomass (Cmic and Nmic), soil microbial community (fungal and bacterial phospholipid fatty acids), basal respiration, and enzymes involved in the carbon cycling (xylanase, trehalase) were measured at depths of 0–2, 0–10 and 10–20 cm. In addition, root biomass and tissue C:N ratio were determined to provide information on the amount and quality of substrates for microbial growth.Elevated temperature under both ambient and elevated CO2 did not show consistent treatment effects. Elevation of air temperature at ambient CO2 induced an increase in Cmic of the 0–10 cm layer, while at elevated CO2 total phospholipid fatty acids (PLFA) increased after the third generation. The metabolic quotient qCO2 decreased at elevated temperature in the ambient CO2 run. Xylanase and trehalase showed no changes in both runs. Root biomass and C:N ratio were not influenced by elevated temperature in ambient CO2. In elevated CO2, however, elevated temperature reduced root biomass in the 0–10 cm and 30–40 cm layers and increased N content of roots in the deeper layers. The different response of root biomass and C:N ratio to elevated temperature may be caused by differences in the dynamics of root decomposition and/or in allocation patterns to coarse or fine roots (i.e. storage vs. resource capture functions). Overall, our data suggests that in soils of low nutrient availability, the effects of climate change on the soil microbial community and processes are likely to be minimal and largely unpredicatable.     

The role of microarthropods in terrestrial decomposition: a meta-analysis of 40 years of litterbag studies

Litterbags have been utilized in soil ecology for about 50 years. They are useful because they confine organic material and thus enable the study of decomposition dynamics (mass loss and/or nutrient loss through time, colonization by soil biota) in situ, i.e. under field conditions. Researchers can easily restrict or permit access to certain size classes of soil fauna to determine their contribution to litter mass loss by choosing adequate mesh size or applying specific biocides. In particular, the mesofauna has received much attention since it comprises two very abundant and diverse microarthropod groups, the Collembola (springtails) and Acari (mites). We comprehensively searched the literature from the mid‐1960s to the end of 2005 for reports on litterbag experiments investigating the role of microarthropods in terrestrial decomposition. Thirty papers reporting 101 experiments satisfied our selection criteria and were included in the database. Our meta‐analysis revealed that microarthropods have a moderate but significant effect on mass loss. We discuss in detail the interactions of the microarthropod effect with study characteristics such as experimental design (e.g. number of bags, duration of experiment), type of exposed organic matter, climatic zone and land use of the study site. No publication bias was detected; however, we noticed a significant decrease in the microarthropod effect with publication year, indicating that, in the first decades of litterbag use, soil zoologists may have studied “promising” sites with a higher a priori probability of positive microarthropod effects on litter mass loss. A general weakness is that the treatments differ not only with respect to the presence or absence of microarthropods, but also with regard to mesh size (small to exclude microarthropods, wide to permit their access) or presence (to exclude microarthropods) and absence (to permit their access) of an insecticide. Consequently, the difference between the decomposition rates in the treatments is not a pure microarthropod effect but will be influenced by the additive effects of mesh size and insecticide. The relative contribution of the “true” microarthropod effect remains unknown without additional treatments controlling for the differential mesh size/insecticide effect. A meta‐analysis including only those studies using different mesh size and for which the data were corrected by subtracting an estimated mesh size effect based on data from the literature yielded a significantly negative microarthropod effect on litter decomposition. These results cast doubt on the widely accepted hypothesis that microarthropods generally exert a positive effect on litter mass loss. We conclude that after 40 years of litterbag studies our knowledge on the role of microarthropods in litter mass loss remains limited and that the inclusion of a third treatment in future studies is a promising way to retain litterbags as a meaningful tool of soil biological studies.     

Impact of faunal complexity on nutrient supply in field mesocosms from a spruce forest soil

A field study in an acidic spruce forest soil using soil mesocosms was conducted to investigate the effects of mesofauna and macrofauna on exchangeable cations, organic matter content, base saturation, and Ca-lactate extractable nutrients. In the field, intact soil monoliths were taken from the ground, defaunated by deep-freezing and wrapped in nets of various mesh-sizes to control immigration of different faunal size classes. The monoliths were then replanted in the field. Three types of treatments for the mesocosms were prepared: (1) microbiota only, (2) microbiota and mesofauna, (3) microbiota, mesofauna, and macrofauna (=complex fauna). After eight months the mesocosms and unmanipulated control plots (treatment 4) were destructively sampled and submitted to chemical analysis. Generally, the exchangeable base cations and Mn²⁺ showed higher contents with increasing faunal complexity, whereas the exchangeable acidic cations of Fe³⁺ and Al³⁺ decreased in the monoliths with complex fauna. These effects were significant for K⁺, Mg²⁺ and Mn²⁺ in the L/F-layer and for Ca²⁺, Mn²⁺, Al³⁺ and Fe³⁺ in the H-layer. As a possible explanation a rise of ion-binding sites in the course of enhanced humification processes is discussed.In the L/F-layer base cations showed higher concentrations in the monoliths with complex fauna as compared to the control plot, which contained intact roots. This might be due to nutrient uptake by roots in the control plot or enhanced mineralization in the monoliths with complex fauna, where roots had been cut.     

Temporal dynamics of bird community composition: an analysis of baseline conditions from long-term data

Numerous anthropogenic activities threaten the biodiversity found on earth. Because all ecological communities constantly experience temporal turnover due to natural processes, it is important to distinguish between change due to anthropogenic impact and the underlying natural rate of change. In this study, we used data sets on breeding bird communities that covered at least 20 consecutive years, from a variety of terrestrial ecosystems, to address two main questions. (1) How fast does the composition of bird communities change over time, and can we identify a baseline of natural change that distinguishes primeval systems from systems experiencing varying degrees of human impact? (2) How do patterns of temporal variation in composition vary among bird communities in ecosystems with different anthropogenic impacts? Time lag analysis (TLA) showed a pattern of increasing rate of temporal compositional change from large-scale primeval systems to disturbed and protected systems to distinctly successional systems. TLA slopes of <0.04 were typical for breeding bird communities with natural turnover, while communities subjected to anthropogenic impact were characterised by TLA slopes of >0.04. Most of the temporal variability of breeding bird communities was explained by slow changes occurring over decades, regardless of the intensity of human impact. In most of the time series, medium- and short-wave periodicity was not detected, with the exception of breeding bird communities subjected to periodic pulses (e.g. caterpillar outbreaks causing food resource peaks).     

Large-scale changes in community composition: determining land use and climate change signals

Human land use and climate change are regarded as the main driving forces of present-day and future species extinction. They may potentially lead to a profound reorganisation of the composition and structure of natural communities throughout the world. However, studies that explicitly investigate both forms of impact--land use and climate change--are uncommon. Here, we quantify community change of Dutch breeding bird communities over the past 25 years using time lag analysis. We evaluate the chronological sequence of the community temperature index (CTI) which reflects community response to temperature increase (increasing CTI indicates an increase in relative abundance of more southerly species), and the temporal trend of the community specialisation index (CSI) which reflects community response to land use change (declining CSI indicates an increase of generalist species). We show that the breeding bird fauna underwent distinct directional change accompanied by significant changes both in CTI and CSI which suggests a causal connection between climate and land use change and bird community change. The assemblages of particular breeding habitats neither changed at the same speed and nor were they equally affected by climate versus land use changes. In the rapidly changing farmland community, CTI and CSI both declined slightly. In contrast, CTI increased in the more slowly changing forest and heath communities, while CSI remained stable. Coastal assemblages experienced both an increase in CTI and a decline in CSI. Wetland birds experienced the fastest community change of all breeding habitat assemblages but neither CTI nor CSI showed a significant trend. Overall, our results suggest that the interaction between climate and land use changes differs between habitats, and that comparing trends in CSI and CTI may be useful in tracking the impact of each determinant.     

Ecological indicators of habitat and biodiversity in a Neotropical landscape: multitaxonomic perspective

Ecological indicators of habitat and biodiversity in a Neotropical landscape: multitaxonomic perspective. The use of indicator species to characterize specific ecological areas is of high importance in conservation/restoration biology. The objective of this study was to identify indicator species of diverse taxa that characterize different landscape units, and to better understand how management alters species composition. We identified two ecomosaics, tropical rain forest and the agricultural matrix, each one comprised of four landscape units. The taxonomic groups studied included birds (highly mobile), butterflies (moderately mobile), terrestrial gastropods (less mobile) and trees (sessile). Sampling efficiency for both ecomosaics was > or = 86%. We found 50 mollusks, 74 butterflies, 218 birds and 172 tree species, for a total of 514 species. Using ordination and cluster analysis, we distinguished three habitat types in the landscape: tropical rainforest, secondary vegetation and pastures with scattered trees and live fences. The InVal (> or = 50%) method identified 107 indicator species, including 45 tree species, 38 birds, 14 butterflies and 10 gastropods. Of these, 35 trees, 10 birds, four butterflies and eight gastropods were forest indicators. Additionally, 10, 28, 10 and two species, respectively per group, were characteristic of the agricultural matrix. Our results revealed a pattern of diversity decrease of indicator species along the rainforest-secondary forest-pasture gradient. In the forest, the gastropods Carychium exiguum, Coelocentrum turris, Glyphyalinia aff. indentata y Helicina oweniana were significantly correlated (p < 0.05) with 90% of the other groups of flora and fauna indicator species. These findings suggest that gastropods may be good indicators of forest habitat quality and biodiversity. The secondary vegetation is an intermediate disturbance phase that fosters high diversity in the agricultural matrix. We exemplify a multitaxa approach, including mesofauna, for ecological monitoring of agricultural landscapes.     

Bird communities in rainforest fragments: guild responses to habitat variables in Tabasco,Mexico

The effects of habitat loss and fragmentation in tropical forests are difficult to separate, as they usually occur concurrently. In the state park La Sierra, in Tabasco, Mexico, the rainforest is being cleared for pasture, and fragments are being used by local inhabitants. This study examined the response of bird feeding guilds to habitat characteristics, including human disturbance, in five fragments of different sizes (1 ∼ 4,500 ha, 2 ∼ 150 ha, and 2 ∼ 80 ha). Using point count observations, 125 species were recorded and were grouped into 11 feeding guilds. As expected, the largest fragment had higher species richness and abundances than the smaller fragments. However, five habitat features differed significantly among fragment sizes, including tree density, the number of tree stumps and the number of trails. Thus the larger fragment was also less disturbed. Fragment size alone was significant only for scavenger species richness, and for the abundance of bark gleaning insectivores and insectivore/nectarivores. Raptors were more diverse and abundant in the large fragment and less disturbed sites. Arboreal frugivores and bark or foliage gleaning insectivores, depended on higher trees and less disturbed sites. A better understanding of the mechanisms that affect persistence is essential for the planning of conservation actions.     

Impact of elevated atmospheric CO2 concentration on soil microbial biomass and activity in a complex, weedy field model ecosystem

Although soil organisms play an essential role in the cycling of elements in terrestrial ecosystems, little is known of the impact of increasing atmospheric CO₂ concentrations on soil microbial processes. We determined microbial biomass and activity in the soil of multitrophic model ecosystems housed in the Ecotron (NERC Centre for Population Biology, Ascot, UK) under two atmospheric CO₂ concentrations (ambient vs. ambient + 200 ppm). The model communities consist of four annual plant species which naturally co-occur in weedy fields and disturbed ground throughout southern England, together with their herbivores, parasitoids and soil biota. At the end of two experimental runs lasting 9 and 4.5 months, respectively, root dry weight and quality showed contradictory responses to elevated CO₂ concentrations, probably as a consequence of the different time-periods (and hence number of plant generations) in the two experiments. Despite significant root responses no differences in microbial biomass could be detected. Effects of CO₂ concentration on microbial activity were also negligible. Specific enzymes (protease and xylanase) showed a significant decrease in activity in one of the experimental runs. This could be related to the higher C:N ratio of root tissue. We compare the results with data from the literature and conclude that the response of complex communities cannot be predicted on the basis of oversimplified experimental set-ups.