Chlorantraniliprole application differentially affects adult emergence of Sympetrum dragonflies in rice paddy fields

Paddy and Water Environment - Rice paddy fields are important habitat for many dragonfly species. In Japan, populations of dragonflies inhabiting rice paddies, in particular Sympetrum (Odonata:...     

Conservation and contingent valuation of farming landscape amenities by visitors: A case study of terraced paddy fields in Central Japan

The contingent valuation method was used with a payment card approach to estimate visitors’ willingness to pay (WTP) to conserve a traditional agricultural landscape of terraced paddy fields in coastal rural Japan. Eighty percent of participants indicated their WTP toward a conservation fund, with estimated mean and median WTP of JPY 953.5 (~?USD $8.99) and JPY 456.4 (~?USD $4.30) per visit per person. Personal income and proximity to residence both positively influenced WTP amount; visitors’ attachment to land and loyalty were positively associated with their willingness to pay for landscape conservation. Actual conservation costs are currently mostly funded by the public municipal budget (56%) and urban volunteers (43%), but government funding sources are declining and becoming unreliable. These findings suggest that visitor donations may supplement existing funding sources for the conservation of terraced paddy field landscapes. However, farmer successors are needed for farm management to sustain traditional farming and rural communities, since a living farm and a vigorous community are essential for rural tourism.     

Endangered crayfish in northern Japan: Distribution, abundance and microhabitat specificity in relation to stream and riparian environment

Japan’s only native crayfish species Cambaroides japonicus has been declining dramatically in the past few decades. For the purpose of conservation planning, twenty-two coastal streams were surveyed to investigate summer distributions of crayfish in relation to stream and riparian environment. Classification and regression trees were used to predict the occurrence and abundance of crayfish. The classification tree model with stream variables as predictors showed that crayfish would occur in swift or high gradient streams (correct classification rate = 91%). Within those streams, however, crayfish only inhabited depositional microhabitats, in which the areas are limited in availability. Crayfish were not found in gentle, low gradient streams containing abundant depositional microhabitats. This paradoxical distribution pattern was attributed to availability of boulder substrates in swift or high gradient streams. The regression tree model indicated that crayfish abundance was determined primarily by the percentage of boulder substrates and the presence of fish (observed vs. predicted r = 0.64).The classification tree model using only riparian variables indicated that the total woody plant (mainly broadleaf species) density followed by the percentage of early successional species such as alder and willow determined the splits of the tree model (correct classification rate = 95%). A leaf processing experiment on 10 riparian plant species suggested that crayfish preferred high nitrogen (or low C/N) leaves.These results suggest that swift or high gradient fishless streams associated with abundant cover in dense broadleaf forest serve conservation areas for this endangered crayfish, and that consideration of riparian composition may facilitate conservation efforts.     

Size-dependent impacts of invasive alien crayfish on a littoral marsh community

The invasive signal crayfish (Pacifastacus leniusculus) may undergo ontogenetic diet shifts with increasing size, but the consequences of crayfish size-structure changes for aquatic food webs are little known. We evaluated size-dependent impacts of signal crayfish on a littoral marsh food web using in-situ enclosures in a northern Japanese marsh. During the 60-day experiment, large crayfish (<30 mm orbital carapace length) rapidly eliminated submerged macrophytes through mechanical destruction while the comparable impacts of small crayfish (>30 mm) appeared after more time had passed. Benthic algal biomass was reduced in the presence of large crayfish but was affected little by small crayfish, suggesting that large crayfish were significant bioturbators. On the other hand, total invertebrate biomass was reduced while total invertebrate density was enhanced in the presence of both crayfish size classes. Potential crayfish impacts on invertebrates are: (1) predation on large vulnerable taxa such as Trichoptera and predatory invertebrates, (2) mechanical destruction of macrophytes, thereby reducing microhabitats for invertebrates, (3) heightened emigration of invertebrates in response to bioturbation and/or (4) predation or competition release on small invertebrates as a result of crayfish reducing their predators/competitors. Invertebrate taxa richness was nearly halved in the presence of large crayfish, probably reflecting reductions of rare taxa. Overall, functional roles of signal crayfish as omnivores and ecosystem engineers remained similar during the ontogenetic stage but the magnitude and rate of crayfish impacts intensified with increasing crayfish size. Thus, removal of large invasive crayfish alone may reduce detrimental impacts on aquatic biodiversity.     

Correction to: Chlorantraniliprole application differentially affects adult emergence of Sympetrum dragonflies in rice paddy fields

Paddy and Water Environment -