Kei Uchida

Biodiversity declines due to abandonment and intensification of agricultural lands: patterns and mechanisms

Declines in plants and herbivorous insects due to land use abandonment and intensification have been studied in agricultural areas worldwide. We tested four hypotheses, which were complementary rather than mutually exclusive, to understand the mechanisms driving biodiversity declines due to abandonment and intensification. These predict that biodiversity decline is caused by a decline in resource diversity, changes in disturbance regime, surrounding landscape conversion, and a decrease in biomass production. We compared plant richness and butterfly and orthopteran richness and diversity among three land use types in seminatural grasslands: abandoned, traditional, and intensified terraces. Then, we examined effects of changes in resource (plant) richness, frequency of disturbance (mowing), and surrounding landscapes on butterfly and orthopteran diversity to understand the mechanisms driving decline after land abandonment and intensification. Plant and herbivore richness and diversity were significantly lower in abandoned and intensified grasslands than in traditional grasslands. This trend was consistent throughout the seasons in both years of the study. Changes in mowing frequency and surrounding landscape explained plant richness declines as a consequence of land abandonment and intensification. Declines in herbivorous insects were explained by plant richness declines and changes in mowing frequency, but not by landscape changes. Plant and herbivore richness were maximized at an intermediate mowing frequency (approximately twice per year), which is typical practice on traditional terraces. This is the first report demonstrating that the intermediate disturbance hypothesis explained well the biodiversity declines in agricultural ecosystems. The richness and diversity responses of herbivore functional groups to plant richness, mowing frequency, and surrounding landscapes were generally inconsistent with predictions. We found significant trends in which butterfly and orthopteran species with low abundance in traditional terraces were lost in abandoned and/or intensive terraces. This may suggest that the number of individuals of most herbivorous species decreased randomly with respect to life-history traits following a decline in plant richness after changes in disturbance frequency. This study demonstrates that declines in herbivorous insects can be explained by multiple factors, and provides a unified explanation for biodiversity declines in both abandoned and intensified use of agricultural lands, which have often been studied separately.

Land abandonment and intensification diminish spatial and temporal β-diversity of grassland plants and herbivorous insects within paddy terraces

Summary 1. Although traditional land-use and management practices are known to enhance environmental heterogeneity in agricultural lands, loss of heterogeneity resulting from recent land-use changes can lead to spatiotemporal b-diversity losses (biotic homogenization). However, patterns and causes of b-diversity loss, especially at a within-field scale, have remained unexplored. 2. We examined b-diversity declines in plants, butterflies and orthopterans resulting from land abandonment and intensification in semi-natural grasslands on paddy margins at a within-field scale in relation to changes in disturbance frequency and surrounding landscapes by surveying eight abandoned, thirteen traditional and ten intensive paddy terraces. Three indices, the additive partitioning of species richness (badd) and the turnover (btu) and nestedness (bne) components of Jaccard dissimilarity of plants and herbivores, were used to evaluate different aspects of b-diversity. We hypothesized that biotic homogenization due to abandonment and intensification would be expressed as low spatiotemporal badd and btu, low spatial bne and high temporal bne. 3. The spatial and temporal badd of plants and herbivores were higher in traditional terraces than in others. Changes in mowing frequency caused direct declines in butterfly badd and indirectly decreased herbivore badd through diminished plant badd in abandoned and intensified terraces. 4. Neighbouring forests increased plant spatial and butterfly temporal badd and btu. Abandoned terraces had higher orthopteran spatial and plant temporal btu than traditional terraces. Mowing frequency generally did not influence spatial and temporal btu of plants and herbivores. In intensive terraces, temporal bne of plants were higher than in traditional terraces, suggesting dominance by plant species sharing similar phenologies. 5. Synthesis and applications. These results suggest that traditional mowing practices are essential for maintaining plant and herbivore badd, and consequently, species pools within terraces. The higher spatial or temporal species turnover of plants and orthopterans in abandoned terraces and higher temporal plant nestedness in intensive than in traditional terraces were not due to increases in species pools within terraces. Because within-terrace environmental heterogeneity is thought to remain in abandoned and intensive terraces, we recommend reduction in mowing frequency in intensive terraces and reintroduction of mowing in abandoned terraces for biodiversity restoration.

Patterns of plant diversity loss and species turnover resulting from land abandonment and intensification in semi-natural grasslands

Land-use changes cause biodiversity loss in semi-natural ecosystems worldwide. Biotic homogenization has led to biodiversity loss, mainly through declines in species composition turnover. Elucidating patterns of turnover in species composition could enhance our understanding of how anthropogenic activities affect community assembly. Here, we focused on whether the decreasing patterns in plant diversity and turnover of species composition resulting from land-use change vary in two regions. We estimated the species diversity and composition of semi-natural grasslands surrounding paddy fields in satoyama landscapes. We examined the differences in species diversity and composition across three land-use types (abandoned, traditional, and intensified) in two regions (Hyogo and Niigata Prefectures, Japan), which were characterized by different climatic conditions. We then assessed alpha-, beta-, and gamma-diversity to compare the patterns of diversity losses in the two regions as a result of land-use changes. In each region, gamma-diversity was consistently higher in the traditional sites compared to abandoned or intensified sites. The analyses revealed that most of the beta-diversity in traditional sites differed significantly from those of abandoned and intensified sites in both regions. However, the beta-diversity of total and perennial species did not differ between traditional and abandoned sites in the Hyogo region. We noted that the beta-diversity of total and perennial species in intensified sites was much lower than that in the traditional sites of the Niigata region. Overall, the patterns of alpha- and gamma-diversity loss were similar in both study regions. Although the biotic homogenization was caused by intensified land-use in the Niigata region, this hypothesis did not completely explain the loss of biodiversity in the abandoned sites in the Hyogo region. The present study contributes to the growing body of work investigating changes in biodiversity as a result of both biotic homogenization and differentiation in semi-natural ecosystems. Conservationists and policy makers should focus on patterns of species composition responded to land-use changes that continue to increase worldwide.

Fertilising semi‐natural grasslands may cause long‐term negative effects on both biodiversity and ecosystem stability

Recently, the use of nutrientrich residues from bioenergy production (digestate) and intensive husbandry (slurry) for fertilising traditionally managed grasslands has gained increased attention (e.g. Duffková, Hejcman, & Libichová, 2015; Duffková & Libichová, 2013; Hensgen, Bühle, & Wachendorf, 2016; Kováčiková, Vargová, & Jančová, 2013). Hensgen et al. (2016) used lowdose nutrient applications (i.e. 25–54 kg N ha−1 year−1, 2–5 kg P ha−1 year−1 and 20–51 kg K ha−1 year−1 for 5 years) in seminatural grasslands to maintain productivity and claimed that these applications did not result in a loss of species richness during the 5year study. Similar shortterm experiments by Duffková and Libichová (2013) and Duffková et al. (2015) came to similar conclusions: lowdose cattle slurry application (i.e. 0–240 kg N ha−1 year−1 and 0–240 kg N ha−1 year−1, 0–40 kg P ha−1 year−1 and 0–180 kg K ha−1 year−1 for 6 years, respectively) increases the herbage yield without affecting the diversity in a speciesrich grassland. The use or recommendation of new intensive management strategies in seminatural grasslands is complicated. Such complexity is typical in ecosystems with high biodiversity and conservation values (e.g. Veen, Jefferson, de Smidt, & Van der Straaten, 2009). Generally, fertilisation decreases plant diversity and changes the species composition (Bobbink, Hornung, & Roelofs, 1998; Borer et al., 2014; De Schrijver Received: 18 September 2017 | Accepted: 22 January 2018 DOI: 10.1111/1365-2664.13129

Towards a Common Toolbox for Rarity: A Response to Violle et al.

In a recent review, Violle et al. [1] presented the concept of functional rarity along with ways to quantify it by combining species functional traits and abundance information. Classifying species according to their rarity will improve conservation strategies, and the ideas by Violle et al. [1] are a timely step forward in this direction. Building on these solid bases is certainly advisable, although there is room for improvement in the scope and in the methods proposed. We stress here some points to help advancing this approach into a more general and flexible tool.

Rediscovery of Celes akitanus (Orthoptera: Acrididae) from semi-natural grasslands in Japan

Celes akitanus was rediscovered in semi‐natural grasslands in Japan. This species is one of the most endangered insects in Japan; most local populations were thought to be extinct. Reliable records of this rare species had been obtained only from Yamagata, Niigata, Tokyo and Nagano Prefectures. We compared the morphology of the holotype of Oedipoda akitana (=C. akitanus) and newly collected specimens and found that they matched with each other. The species was redescribed based on the holotype and new specimens. A molecular phylogenetic analysis involving other acridid species indicated that our samples were practically identical to C. akitanus from China. We conclude that the specimens we collected are C. akitanus, which has been rediscovered in Japan after about 30 years. Because the discovered populations were restricted to narrow and scattered areas, conservation of these populations should be a high priority. Population monitoring and habitat assessment are required. Because C. akitanus and many other endangered species are found in the grassland areas, these habitats should be protected and maintained.

Historical changes in grassland area determined the demography of semi-natural grassland butterflies in Japan

Semi-natural grassland areas expanded worldwide several thousand years ago following an increase in anthropogenic activities. However, semi-natural grassland habitat areas have been declining in recent decades due to changes in landuse, which have caused a loss of grassland biodiversity. Reconstructing historical and recent demographic changes in semi-natural grassland species will help clarify the factors affecting their population decline. Here we quantified past and recent demographic histories of Melitaea ambigua (Lepidoptera; Nymphalidae), an endangered grassland butterfly species in Japan. We examined changes in demography over the past 10,000 years based on 1378 bp of mitochondrial COI gene. We then examined changes in its genetic diversity and structure during the last 30 years using nine microsatellite DNA markers. The effective population size of M. ambigua increased about 3000–6000 years ago. In contrast, the genetic diversity and effective population sizes of many populations significantly declined from the 1980s to 2010s, which is consistent with a recent decline in the species population size. Our data suggest that the M. ambigua demography can be traced to changes in area covered by semi-natural grasslands throughout the Holocene.

Biodiversity Has Been Maintained with Intermediate Disturbance in Traditional Agricultural Lands

Richness and diversity of plant and herbivorous insect species were significantly lower in abandoned and intensified grasslands than in traditional grasslands. This trend was consistent throughout the seasons in 2011 and 2012. Changes in mowing frequency and surrounding landscape due to land abandonment and intensification explained plant richness declines around paddy terraces. Declines in herbivorous insects were well explained by plant richness declines and changes in mowing frequency. Plant and herbivore richness were maximized at an intermediate mowing frequency (about twice per year), which is a typical practice on traditional terraces.