Neighboring Plants Research Articles

An Index of Competition Reduces Statistical Variability and Improves Comparisons between Genotypes of Miscanthus

It is important for breeders and producers to be aware of competition effects for variety trials. We aimed at developing an index of competition to reduce statistical variability in field trials and improve comparisons between genotypes of Miscanthus. Twenty-one clones belonging to four species of Miscanthus (M. x giganteus, M. floridulus, M. sinensis, and M. sacchariflorus) planted at the same density were compared at two harvest dates during the second and third crop years. Aboveground volume was shown to be a good predictor of the aboveground biomass of the clones, and was analysed for the competition effect. The best competition index was the ground area occupied by the eight neighbour plants, among the four indices defined as covariates in the statistical models. It reduced the root mean square error of the aboveground volume by as much as 17 %, explaining up to 36 % of the residual error of the model. Our results then concerned the contribution of intragenotypic competition of Miscanthus to the variability between plants of a same clone during field trials, the relationship between competition ability and plant traits, and the comparison of genotypes regarding this competition. All clones showed negative competition sensitivities depending on harvest date, crop year, and clone. The competition effects lead to reduction in mean aboveground volume by up to 17 %. Competition sensitivities were strongly correlated with aboveground development (height and yield) in both crop years, whatever the harvest dates. In Miscanthus field trials, using a competition index may help to reduce statistical variability and improve comparisons between genotypes.

Pollinators Complicate Conservation of an Endemic Plant: Physaria obcordata (Cruciferae) in the Piceance Basin, Colorado

To the unnamed road grader operator, resident of Rangeley CO, who on May 13, 1992, idled his machine atop Calamity Ridge and jumped down to admonish us, as we collected insects from P. obcordata flowers, to use care in dealing with those plants with the small yellow flowers because “they grow nowhere else in the world but Rio Blanco Co.”: We dub thee Sir Dudley, Knight of the Twinpod, and thank you belatedly for your challenge, for your concern. Physaria obcordata is a rare endemic of western Colorado. Plants are self-incompatible; they cannot reproduce sexually unless pollinators move pollen between flowers of different genets. We found no evidence that: seed production was limited by inadequate pollination or that pollinations between near neighbor plants (inbreeding depression) or between distant plants (outbreeding depression) resulted in reduced fruit or seed set. Examples are given of the potentially devastating effect of grazing on fruit and seed production. Preliminary evidence suggests that P. obcordata can hybridize with its common congener, P. acutifolia. Only crosses with P. obcordata as pollen recipient and P. acutifolia as pollen donor seemed fertile. Primary flower-visitors of P. obcordata are ground-nesting native bees in the families Andrenidae and Halictidae. Most species visiting the flowers of P. obcordata are generalists. Only two bee species were likely mustard specialists. The only non-bee visitor of any import was a dipteran, Gonia (Tachinidae). Predictions of the distances flown by common bee visitors were made using the equations of Greenleaf et al. (2007). No bee is likely to travel more than 1 km from its nesting site to visit P. obcordata flowers and most are likely to fly distances that are significantly less. The implications of flight range estimates for gene flow between Physaria populations and for pollinator protection are discussed. Several recommendations are made for conservation of P. obcordata and its attendant bees.

Individual species–area relationships and spatial patterns of species diversity in a Great Basin, semi‐arid shrubland

Traditional biodiversity metrics operate at the level of a plant community but do not capture spatial variation in diversity from a ‘plant's‐eye view’ of a community. Recently‐developed statistics consider the spatial patterns of plants as well as the number and distribution of species in local plant neighborhoods to quantitatively assess multispecies spatial patterns from a ‘plant's‐eye view’. We used one such statistic, the individual species area relationship (ISAR), to assess spatial patterns of species diversity in a Great Basin (USA) semi‐arid shrubland through an analysis of a spatial dataset on shrub species and locations. In conjunction with appropriate null models, the ISAR blends species area relationships with second‐order spatial statistics to measure the expected species richness in local neighborhoods of variable size around the individuals of a focal species within a community. We found that, contrary to a previous analysis using more traditional methods, the community was well‐mixed with a typical shrub surrounded on average by 4.9 shrub neighbors of 2.1 species at a neighborhood scale of 1.0 m. We also found statistically significant fine‐scale variation in diversity patterns, such that neighborhoods of two species were more diverse than expected by a heterogeneous Poisson null model that accounted for larger‐scale habitat heterogeneity. However, this effect was caused by intraspecific aggregation of these species and was not due to positive interspecific association. Contrary to previous findings in other semi‐arid shrublands, our analysis suggests that the spatial pattern of the shrub community was not significantly structured by interspecific facilitation. This result supports growing evidence for balanced species patterns of adult plants in multispecies communities. Our approach may be used in other communities to describe complex multispecies spatial patterns, quantify species‐specific associations with diversity patterns, and to generate hypotheses regarding relationships between patterns and community‐structuring processes.

Neighborhood effects on seed dispersal by frugivores: testing theory with a mistletoe–marsupial system in Patagonia

The outcome of the dispersal process in zoochorous plants is largely determined by the behavior of frugivorous animals. Recent simulation studies have found that fruit removal rates and mean dispersal distances are strongly affected by fruiting plant neighborhoods. We empirically tested the effects of conspecific fruiting plant neighborhoods, crop sizes, and plant accessibility on fruit removal rates and seed dispersal distances of a mistletoe species exclusively dispersed by an arboreal marsupial in Northern Patagonia. Moreover, in this study, we overcome technical limitations in the empirical estimation of seed dispersal by using a novel 15N stable isotope enrichment technique together with Bayesian mixing models that allowed us to identify dispersed seeds from focal plants without the need of extensive genotyping. We found that, as predicted by theory, plants in denser neighborhoods had greater fruit removal and shorter mean dispersal distances than more isolated plants. Furthermore, the probability of dispersing seeds farther away decreased with neighborhood density. Larger crop sizes resulted in larger fruit removal rates and smaller probabilities of longer distance dispersal. The interplay between frugivore behavioral decisions and the spatial distribution of plants could have important consequences for plant spatial dynamics.

Unique arthropod communities on different host-plant genotypes results in greater arthropod diversity

Studies on the effect of plant-species diversity on various ecological processes has led to the study of the effects of plant-genetic diversity in the context of community genetics. Arthropod diversity can increase with plant-species or plant-genetic diversity (Wimp et al. in Ecol Lett 7:776–780, 2004). Plant diversity effects can be difficult to separate from other ecological processes, for example, complementarity. We asked three basic questions: (1) Are arthropod communities unique on different host-plant genotypes? (2) Is arthropod diversity greater when associated with greater plant-genetic diversity? (3) Are arthropod communities more closely associated with host-plant genetics than the plant neighborhood? We studied canopy arthropods on Populus fremontii trees randomly planted in a common garden. All trees were planted in a homogeneous matrix, which helped to reduce P. fremontii neighborhood effects. One sample was comprised of few P. fremontii genotypes with many clones. A second sample was comprised of many P. fremontii genotypes with few clones. A second data set was used to examine the relationships between the arthropod community with P. fremontii genetic composition and the neighborhood composition of the focal host plant. Unique arthropod communities were associated with different P. fremontii genotypes, and arthropod community diversity was greater in the sample with greater P. fremontii genotypic diversity. Arthropod community similarity was negatively correlated with P. fremontii genetic distance, but arthropod community similarity was not related to the neighborhood of the P. fremontii host plant.

Disrupting mycorrhizal mutualisms: a potential mechanism by which exotic tamarisk outcompetes native cottonwoods

The disruption of mutualisms between plants and mycorrhizal fungi is a potentially powerful mechanism by which invasives can negatively impact native species, yet our understanding of this mechanism's role in exotic species invasion is still in its infancy. Here, we provide several lines of evidence indicating that invasive tamarisk (Tamarix sp.) negatively affects native cottonwoods (Populus fremontii) by disrupting their associations with arbuscular mycorrhizal (AM) and ectomycorrhizal (EM) fungi. At a field site in the early stages of tamarisk invasion, cottonwoods with tamarisk neighbors had reduced EM colonization and altered EM fungal community composition relative to cottonwoods with native neighbors, leading to reductions in EM propagule abundance in the soil beneath tamarisk. Similarly, AM colonization of cottonwoods was reduced with a tamarisk neighbor, but there were no significant changes in AM fungal spore communities or propagule abundance. Root colonization by nonmycorrhizal fungi, including potential pathogens, was higher in cottonwoods with tamarisk neighbors. A greenhouse experiment in which AM and EM inoculation and plant neighbor were manipulated in a fully factorial design showed that cottonwoods benefited from mycorrhizas, especially EM, in terms of shoot biomass when grown with a conspecific, but shoot biomass was similar to that of nonmycorrhizal controls when cottonwoods were grown with a tamarisk neighbor. These results are partially explained by a reduction in EM but not AM colonization of cottonwoods by a tamarisk neighbor. Tamarisk neighbors negatively affected cottonwood specific leaf area, but not chlorophyll content, in the field. To pinpoint a mechanism for these changes, we measured soil chemistry in the field and the growth response of an EM fungus (Hebeloma crustuliniforme) to salt-amended media in the laboratory. Tamarisk increased both NO3- concentrations and electrical conductivity 2.5-fold beneath neighboring cottonwoods in the field. Salt-amended media did not affect the growth of H. crustuliniforme. Our findings demonstrate that a nonnative species, even in the early stages of invasion, can negatively affect a native species by disrupting its mycorrhizal symbioses. Some of these changes in mycorrhizal fungal communities may remain as legacy effects of invasives, even after their removal, and should be considered in management and restoration efforts.

O-Coumaric acid from invasive Eupatorium adenophorum is a potent phytotoxin

A phytochemical study of the invasive Eupatorium adenophorum indicated that the plant was rich in a phenolic compound o-coumaric acid (or 2-hydroxycoumaric acid). Biological investigations with the model plant Arabidopsis thaliana and crop plants showed that o-coumaric acid strongly inhibited seed germination, plant growth and root elongation, reduced the photosynthesis in old leaves, and induced the root cell death and the expression of genes related to senescence, oxidative stress, and systemic acquired resistance. The phytotoxic effects of o-coumaric acid exhibit selectivity between under- and above-ground parts of test plants and between E. adenophorum and other plants. These results indicate that o-coumaric acid is a potent toxin that might play an important role in the competition of E. adenophorum with its neighboring plants during its invasion and establishment.

Plant neighborhood influences colonization of Brassicaceae by specialist and generalist aphids

A plant's own characteristics, but also those of its neighbors, might have an impact on its probability of being colonized by herbivorous insects. A plant might be less colonized and experience associational resistance when it grows near repellent neighbors. In contrast, it might be more colonized and experience associational susceptibility near attractive neighbors. To date, mechanisms that drive associational defense are not really understood. In order to gain insights into the occurrence of associational resistance versus associational susceptibility under field conditions, we conducted an experiment to determine the influence of neighboring plants on the colonization of a focal plant by aphids. The focal plant was always Brassica oleracea. The neighbors were B. oleracea (control), B. napus, B. nigra, or Solanum lycopersicum, which represent contrasting levels of physical and chemical defenses. The focal plant, B. oleracea, was more colonized by the specialist aphid Brevicoryne brassicae, and experienced associational susceptibility when it was surrounded by B. nigra or B. napus. In contrast, B. oleracea was less colonized by the generalist aphid Myzus persicae, and experienced associational resistance when it was surrounded by S. lycopersicum, B. nigra or B. napus. Neighboring plants had no significant impact on host plant choice by the generalist aphid Macrosiphum euphorbiae. In conclusion, attraction or repulsion of the specialist aphid B. brassicae and the generalist aphid M. persicae by B. nigra, B. napus, and S. lycopersicum resulted in associational susceptibility or associational resistance for B. oleracea.

Patch size‐dependent community recovery after massive disturbance

Massive anthropogenic and climate-related disturbances are now common in ecosystems worldwide, generating widespread die-off and subsequent community recovery dominated by remnant-patch dynamics rather than open-gap dynamics. Whether communities can recover and, if so, which factors mediate recolonization rate and extent remain unresolved. Here we evaluate recolonization dynamics of southern U.S. salt marshes that experienced extensive, drought-induced die-off of the foundation species Spartina alterniflora over the previous decade. Surveys of Georgia (USA) salt marshes showed little seedling recruitment in die-off areas but persistence of Spartina particularly in large, rather than small, remnant patches. Given this natural variation in remnant patch size, we conducted field experiments to test whether key plant-controlling biotic (grazing, plant neighbor presence) and abiotic (water availability) factors differentially impact Spartina recolonization at small and large-patch scales. In the small-patch (< 1 m2) experiment in 2009, removing grazers and plant neighbors prompted dramatically higher expansion and growth of Spartina relative to controls, while adding freshwater to reduce water limitation had little effect. In contrast, large-patch (> 20 m2 borders advanced significantly over the same time period regardless of grazer or neighbor removal. We continued the large-patch experiments in 2010, a year that experienced drought, and also added freshwater or salt to borders to modify ambient drought stress; overall, borders advanced less than the previous year but significantly more where neighbors were removed or freshwater added. Thus, water availability appears to mediate Spartina recovery by fueling large-patch expansion during wet summers and intensifying interspecific competition during drought. Combined, these findings suggest ecosystems can recover from massive disturbance if remnant foundation species' patches are large enough to overcome biotic inhibition and successfully expand during periods of relaxed abiotic stress.

Morphological adaptation of a palatable plant to long-term grazing can shift interactions with an unpalatable plant from facilitative to competitive

Unpalatable plants can protect palatable neighbor plants from grazing pressure, but morphological evolution of a palatable species might change its interactions with unpalatable plants. We predicted that when a palatable species has locally adapted to grazing by expressing a dwarf phenotype that reduces grazer accessibility, the dwarf plants experience relatively more competitive effects than facilitative effects from large, well-defended, unpalatable species. We used a transplant experiment, in which both dwarf and large ecotypes of a palatable annual species, Persicaria longiseta, were transplanted outside and inside the canopy of an unpalatable nettle, Urtica thunbergiana, in a long-term deer grazing habitat of Nara Park, Japan. The dwarf ecotype of Persicaria has adapted to the grazing environments of the park by exhibiting inherently short shoots and small leaves, whereas the large ecotype is found in habitats with no grazing history. A previous common-garden study suggested that the phenotypic differences were genetically based and that phenotypic plasticity contributed little to the morphological difference. The large-phenotype of Persicaria experienced significantly increased morphological size, survival, and reproductive output under the Urtica canopy compared to outside the canopy, whereas these traits of the dwarf phenotype were reduced under the Urtica canopy compared to outside. These results indicate that the net effects of Urtica on Persicaria were positive for the large ecotype and negative for the dwarf ecotype. Thus, the morphological adaptation of a palatable species to avoid grazing altered its interactions with a large, well-defended neighbor.

Plant neighbour identity matters to belowground interactions under controlled conditions.

BackgroundRoot competition is an almost ubiquitous feature of plant communities with profound effects on their structure and composition. Far beyond the traditional view that plants interact mainly through resource depletion (exploitation competition), roots are known to be able to interact with their environment using a large variety of mechanisms that may inhibit or enhance access of other roots to the resource or affect plant growth (contest interactions). However, an extensive analysis on how these contest root interactions may affect species interaction abilities is almost lacking.Methodology/Principal FindingsIn a common garden experiment with ten perennial plant species we forced pairs of plants of the same or different species to overlap their roots and analyzed how belowground contest interactions affected plant performance, biomass allocation patterns, and competitive abilities under abundant resource supply. Our results showed that net interaction outcome ranged from negative to positive, affecting total plant mass and allocation patterns. A species could be a strong competitor against one species, weaker against another one, and even facilitator to a third species. This leads to sets of species where competitive hierarchies may be clear but also to groups where such rankings are not, suggesting that intransitive root interactions may be crucial for species coexistence.Conclusions/SignificanceThe outcome of belowground contest interactions is strongly dependent on neighbours' identity. In natural plant communities this conditional outcome may hypothetically help species to interact in non-hierarchical and intransitive networks, which in turn might promote coexistence.

Welcome to the neighbourhood: interspecific genotype by genotype interactions in Solidago influence above‐ and belowground biomass and associated communities

Intra- and interspecific plant-plant interactions are fundamental to patterns of community assembly and to the mixture effects observed in biodiversity studies. Although much research has been conducted at the species level, very little is understood about how genetic variation within and among interacting species may drive these processes. Using clones of both Solidago altissima and Solidago gigantea, we found that genotypic variation in a plant's neighbours affected both above- and belowground plant traits, and that genotype by genotype interactions between neighbouring plants impacted associated pollinator communities. The traits for which focal plant genotypic variation explained the most variation varied by plant species, whereas neighbour genotypic variation explained the most variation in coarse root biomass. Our results provide new insight into genotypic and species diversity effects in plant-neighbour interactions, the extended consequences of diversity effects, and the potential for evolution in response to competitive or to facilitative plant-neighbour interactions.

The Composite Effect of Transgenic Plant Volatiles for Acquired Immunity to Herbivory Caused by Inter-Plant Communications

A blend of volatile organic compounds (VOCs) emitted from plants induced by herbivory enables the priming of defensive responses in neighboring plants. These effects may provide insights useful for pest control achieved with transgenic-plant-emitted volatiles. We therefore investigated, under both laboratory and greenhouse conditions, the priming of defense responses in plants (lima bean and corn) by exposing them to transgenic-plant-volatiles (VOCos) including (E)-β-ocimene, emitted from transgenic tobacco plants (NtOS2) that were constitutively overexpressing (E)-β-ocimene synthase. When lima bean plants that had previously been placed downwind of NtOS2 in an open-flow tunnel were infested by spider mites, they were more defensive to spider mites and more attractive to predatory mites, in comparison to the infested plants that had been placed downwind of wild-type tobacco plants. This was similarly observed when the NtOS2-downwind maize plants were infested with Mythimna separata larvae, resulting in reduced larval growth and greater attraction of parasitic wasps (Cotesia kariyai). In a greenhouse experiment, we also found that lima bean plants (VOCos-receiver plants) placed near NtOS2 were more attractive when damaged by spider mites, in comparison to the infested plants that had been placed near the wild-type plants. More intriguingly, VOCs emitted from infested VOCos-receiver plants affected their conspecific neighboring plants to prime indirect defenses in response to herbivory. Altogether, these data suggest that transgenic-plant-emitted volatiles can enhance the ability to prime indirect defenses via both plant-plant and plant-plant-plant communications.

Table of Contents

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Sedum cools soil and can improve neighboring plant performance during water deficit on a green roof

Green roofs have the potential to function as islands of biodiversity within urban and suburban environments. However, plant diversity is constrained by the harsh environment of a green roof, especially summertime water deficit and heat stress. We hypothesized that Sedum species, which are highly tolerant of the roof-top environment, would reduce peak soil temperature and increase performance of neighboring plants during summer water deficit. To test these hypotheses, we grew focal plant species with and without Sedum on a green roof. We then monitored growth during wet periods and drought tolerance during dry periods. During a three-year experiment, S. album reduced maximum growth of neighbor plants, Agastache rupestris and Asclepias verticillata, during favorable growth conditions, but increased performance of neighbors during summer water deficit. In a second experiment, four species of Sedum were each found to decrease peak soil temperature by 5–7 °C. All species decreased total growth of neighboring Agastache ‘Black Adder’ during favorable growth conditions, but again increased performance during summer water deficit. These results suggest that the palette of green roof plants can be expanded by using Sedum species as nurse plants.

Root herbivory affects oviposition and feeding behavior of a foliar herbivore

Performance and distribution of phytophagous insects are driven by direct and indirect competitive interactions. Plant-feeding arthropods have been shown to interact indirectly through the plants’ response to herbivory. In the case of systemically induced plant responses, this interaction extends to herbivores inhabiting different parts of a plant, for example, above- and belowground herbivores. Plant-induced responses elicited by root herbivores have been shown to affect feeding and development of aboveground herbivores. However, little is known about how root feeding affects host choice behavior of aboveground herbivores, including both adult oviposition behavior and larval host acceptance. Here, we report that root feeding by the wireworm, Agriotes lineatus, influences oviposition decisions and larval leaving rate of an aboveground herbivore, Spodoptera littoralis .I n choice experiments, female S. littoralis deposited more and larger egg batches on undamaged plants when compared with wireworm-infested plants. In a larval feeding experiment, a higher percentage S. littoralis larvae moved away from the wireworm-infested plant onto a neighboring undamaged plant as compared with larvae feeding on previously undamaged plants. Larvae did not show an increased tendency to leave when feeding on plants previously exposed to conspecific larvae. Our results show that indirect interactions between belowground and aboveground herbivores extend to behavioral avoidance, both in terms of oviposition and larval feeding decisions. This allows the foliar herbivore to avoid systemic plant responses elicited by root herbivory, which likely represent reduced food quality and increased apparency toward natural enemies.

Photosynthetic Mediterranean meadow orchids feature partial mycoheterotrophy and specific mycorrhizal associations

We investigated whether four widespread, photosynthetic Mediterranean meadow orchids (Ophrys fuciflora, Anacamptis laxiflora, Orchis purpurea, and Serapias vomeracea) had either nutritional dependency on mycobionts or mycorrhizal fungal specificity. Nonphotosynthetic orchids generally engage in highly specific interactions with fungal symbionts that provide them with organic carbon. By contrast, fully photosynthetic orchids in sunny, meadow habitats have been considered to lack mycorrhizal specificity. We performed both culture-dependent and culture-independent ITS sequence analysis to identify fungi from orchid roots. By analyzing stable isotope ((13)C and (15)N) natural abundances, we also determined the degree of autotrophy and mycoheterotrophy in the four orchid species. Phylogenetic and multivariate comparisons indicated that Or. purpurea and Oph. fuciflora featured lower fungal diversity and more specific mycobiont spectra than A. laxiflora and S. vomeracea. All orchid species were significantly enriched in (15)N compared with neighboring non-orchid plants. Orchis purpurea had the most pronounced N gain from fungi and differed from the other orchids in also obtaining C from fungi. These results indicated that even in sunny Mediterranean meadows, orchids may be mycoheterotrophic, with correlated mycorrhizal fungal specificity.

Waterborne signaling primes the expression of elicitor-induced genes and buffers the oxidative responses in the brown alga Laminaria digitata.

As marine sessile organisms, seaweeds must respond efficiently to biotic and abiotic challenges in their natural environment to reduce the fitness consequences of wounds and oxidative stress. This study explores the early steps of the defense responses of a large marine brown alga (the tangle kelp Laminaria digitata) and investigates its ability to transmit a warning message to neighboring conspecifics. We compared the early responses to elicitation with oligoguluronates in laboratory-grown and harvested wild individuals of L. digitata. We followed the release of H2O2 and the concomitant production of volatile organic compounds. We also monitored the kinetics of expression of defense-related genes following the oxidative burst. Laboratory-grown algae were transplanted in kelp habitats to further evaluate their responses to elicitation after a transient immersion in natural seawater. In addition, a novel conditioning procedure was established to mimic field conditions in the laboratory. Our experiments showed that L. digitata integrates waterborne cues present in the kelp bed and/or released from elicited neighboring plants. Indeed, the exposure to elicited conspecifics changes the patterns of oxidative burst and volatile emissions and potentiates this kelp for faster induction of genes specifically regulated in response to oligoguluronates. Thus, waterborne signals shape the elicitor-induced responses of kelps through a yet unknown mechanism reminiscent of priming in land plants.

Herbivore-induced maize volatiles serve as priming cues for resistance against post-attack by the specialist armyworm Mythimna separata

Plants show a diversity of defense strategies against a wide range of herbivores. The emission of a specific blend of volatiles in response to herbivory (HIPVs – herbivore-induced plant volatiles) plays a great ecological role in indirect protection of the plants by attracting natural enemies of herbivores and priming their neighboring plants that can cause poorer foraging habitats on the ‘receiver’ plants. Maize plants showed induction of a blend of volatiles including monoterpenes, sesequiterpenes, homoterpenes, green leaf volatiles, and indole, in response to the specialist herbivore Mythimna separata. Conspecific plants placed downwind of infested maize plants showed reduced larval development after exposure to HIPVs, compared to those exposed to volatiles from uninfested plants. These findings indicate that exposure of maize plants to HIPVs primed these plants for enhanced defense responses to specialist herbivores of Poaceae.

Power generation and heat recovery Case study: a synergy project between a waste water treatment plant and a green waste composting platform

A common valorization of digester gas and composting gas increases the efficiency of the co-generator installation by 10% to 15%. In this case study, a green waste fermentation and composting platform and its neighboring waste water treatment plant (WWTP) opted for a common co-generator: about 600,000 m3 of digester gas and 1,900,000 m3/year of fermentation gas (biogas) transformed into electricity and heat. The energy content of this combined gas source is about 13,800 MW/a, out of which about 38% is transformed into electricity, about 42% is converted into heat, and 20% is lost. The electrical energy produced (600 kW) is sold to the Swiss electrical grid (Swissgrid Program) as Ökostrom, or “green power,” at a higher price than that of normal power. The heat produced (660 kWh) is used to heat the composter (60 kWh), the digester (125 kWh), and the buildings (25 kW). The excess heat (450 kWh) could also be used for a future low-temperature biosolids drying project, whose life-cycle costs would be counterbalanced by the reduction in disposal costs. This project allows for an optimal use of the energy content of biogas and digester gas. Once drying is implemented, the environmental impact will be even more beneficial with a reduction in transport and the facilitation of phosphorous recovery from dried biosolids. In this case study, the large amount of biogas produced would enable the implementation of low-temperature biosolids drying using the excess heat of the co-gen facilities. The ratio of the biogas to the digester gas production has to be at least 2.5 to 3.0 in order to produce sufficient excess heat for a low-temperature dryer. Low-temperature drying is the most ecological and sensible way of using locally produced waste-heat all year long.