Koenraad Van Meerbeek

Energy potential for combustion and anaerobic digestion of biomass from low-input high-diversity systems in conservation areas.

In this study, we assessed the potential for bioenergy production of Low‐Input High‐Diversity (LIHD) systems in temperate West‐European conservation areas. A wide range of seminatural ecosystems (wet and dry grasslands, marshes, tall‐herb vegetation and heathlands) was sampled. Because LIHD biomass is often scattered and discontinuously available, we only considered the potential for anaerobic digestion and combustion. Both technologies are suitable for decentralized biomass utilization. The gross energy yield showed a promising range between 46–277 GJ per hectare per mowing cycle (MC). The energy efficiency of the anaerobic digestion process was rather low (10–30%) with a methane energy yield of 5.5–35.5 GJ ha−1 MC−1, experimentally determined by batch digestion tests. The water content, functional group composition and biochemical composition (hemicellulose, cellulose, lignin and Kjeldahl nitrogen) of the biomass were analyzed to assess the suitability of different valorization pathways. On the basis of the results, we were able to propose recommendations regarding the appropriate conversion techniques. Biomass from plant communities with ‘late’ harvest dates (August–October) or a high fraction of woody species like heathland and dune slacks, is best valorized through combustion, while herbaceous biomass of ‘early’ harvested grasslands (June–July) and tall‐herb vegetation can better be digested. The main advantages of the production of bioenergy from LIHD biomass originating from conservation management are the minimization of the competition with food production and its potential to reconcile renewable energy policies and biodiversity goals.

Impact of land-use intensity on the conservation of functional and phylogenetic diversity in temperate semi-natural plant communities

The earth is facing a worldwide decline in biodiversity, with land-use change identified as one of the most important drivers. There is evidence that the loss of diversity has a significant impact on ecosystem functioning. Earlier research focused on species richness, but more recent, functional and phylogenetic diversity came into the picture as the stronger determinants of ecosystem processes. The effects of increasing land-use intensity on functional (FD) and phylogenetic diversity (PD), however, are still poorly understood. We studied how FD and PD are affected by land-use intensity in temperate plant communities. Our results show that land-use intensity has a clear impact on species richness, but also affects functional and phylogenetic diversity. Intensive agricultural areas fail to support high and sustainable levels of functional and phylogenetic diversity. These results highlight the need for the protection of biodiversity in nature reserves and the conservation of areas with extensive agricultural practices. Because species richness may influence the measures of functional and phylogenetic diversity, we compared the observed FD and PD values with random values generated with a matrix-swap null model. The observed discrepancy between species loss and the loss of FD and PD calls for an integrated approach to biodiversity conservation, in which the different components of biodiversity are considered together.

Assessing top- and subsoil organic carbon stocks of Low-Input High-Diversity systems using soil and vegetation characteristics

The soil organic carbon (SOC) stock is an important indicator in ecosystem service assessments. Even though a considerable fraction of the total stock is stored in the subsoil, current assessments often consider the topsoil only. Furthermore, mapping efforts are hampered by the limited spatial density of these topsoil measurements. The aim of this study was to assess the SOC stock in the upper 100cm of soil in 30,556ha of Low-Input High-Diversity systems, such as nature reserves, in Flanders (Belgium) and compare this estimate with the stock found in the topsoil (upper 15cm). To this end, we combined depth extrapolation of 139 measurements limited to the topsoil with four digital soil mapping techniques: multiple linear regression, boosted regression trees, artificial neural networks and least-squares support vector machines. Particular attention was given to vegetation characteristics as predictors. For both the stock in the upper 15cm and 100cm, a boosted regression trees approach was most informative as it resulted in the lowest cross-validation errors and provided insights in the relative importance of predictors. The predictors of the stock in the upper 100cm were soil type, groundwater level, clay fraction and community weighted mean (CWM) and variance (CWV) of plant height. These predictors, together with the CWM of specific leaf area, aboveground biomass production, CWV and CWM of rooting depth, terrain slope, CWM of mycorrhizal associations and species diversity also explained the topsoil stock. Our total stock estimates show that focusing on the topsoil (1.63Tg OC) only considers 36% of the stock in the upper 100cm (4.53Tg OC). Given the magnitude of subsoil OC and its dependency on typical ecosystem characteristics, it should not be neglected in regional ecosystem service assessments.

Effects of biodiversity loss and restoration scenarios on tree-related ecosystem services

ABSTRACT In landscapes worldwide, trees in forests and agricultural lands have important ecological functions. Their loss may have important consequences for the delivery of ecosystem services (ES) to local communities, even if individual trees have low conservation values. This study explores the effect of land use and land use change on the provisioning of tree-related ES in a mixed Afromontane landscape in Ethiopia. First, we mapped the current distribution of tree-related ES using indicator ES, which represent the most characteristic ES for different land use types. More ES were characteristic for indigenous forest and agroforest, compared to exotic forest, cropland, and rangeland. A scenario analysis was conducted on the effect of tree species loss and restoration (RES) on ES. Two ES indices, ES diversity and ES multifunctionality, were used to evaluate the ES supply. The different behavior of the two ES indices in the species loss scenarios suggests that rare species have distinct traits that provide specific ES, which could not be compensated by the remaining common species. In tree species-poor landscapes, local communities prefer multifunctional tree species and these keep the diversity of ES supply high. Overall, our findings demonstrate that future conservation and restoration programs in mixed landscapes should both protect a large diversity of tree species, including rare tree species, and promote multifunctional keyston species to ensure a long-term and diverse ES supply. EDITED BY Edmundo Barrios

Causing confusion in the debate about the transition toward a more plant-based diet

White and Hall (1) recently assessed the contribution of animal-based agriculture to greenhouse gas emissions (GHGE) and nutrient provision of the United States society. Unfortunately, their study provides a misleading message. Reducing animal-based food is needed to meet climate goals and future global food demands (2). Hence, it is important to assess impacts of dietary changes. However, to be useful, assessments—or at least their interpretations—need to be realistic. By only discussing a situation without animal-based agriculture, White and Hall (1) neglect a wide spectrum of diets. Importantly, their conclusions implicitly assume linear trends between current diet and an animal-free scenario (Fig. 1 A ). The literature, however, provides evidence for nonlinear relationships with an optimum for GHGE reduction and nutritional capacity at intermediate levels of animal-based agriculture (Fig. 1 B ). Important scenarios to explore in future research include sustainable food production with a varied plant-based diet, a vegetarian diet, and the implementation … [↵][1]1To whom correspondence should be addressed. Email: koenraad.vanmeerbeek{at}bios.au.dk. [1]: #xref-corresp-1-1

Tree diversity mitigates defoliation after a drought-induced tipping point

Understanding the processes that underlie drought-related tree vitality loss is essential for anticipating future forest dynamics, and for developing management plans aiming at increasing the resilience of forests to climate change. Forest vitality has been continuously monitored in Europe since the acid rain alert in the 1980s, and the intensive monitoring plots of ICP Forests offer the opportunity to investigate the effects of air pollution and climate change on forest condition. By making use of over 100 long-term monitoring plots, where crown defoliation has been assessed extensively since 1990, we discovered a progressive shift from a negative to a positive effect of species richness on forest health. The observed tipping point in the balance of net interactions, from competition to facilitation, has never been reported from real ecosystems outside experimental conditions; and the strong temporal consistency of our observations with increasing drought stress emphasizes its climate change relevance. Furthermore, we show that higher species diversity has reduced the severity of defoliation in the long term. Our results confirm the greater resilience of diverse forests to future climate change-induced stress. More generally, they add to an accumulating body of evidence on the large potential of tree species mixtures to face manifold disturbances in a changing world.