To evaluate the optimum area of semi-natural grassland to maintain maximum butterfly and avian species richness in Japan, digitalized grid data of butterfly and avian distribution, as well as vegetation distribution, throughout the country were used. After obtaining logistic regression models explaining the probabilities of occurrence of each species with semi-natural grassland area and latitude as variables, the optimum value was calculated. The expected maximum species richness of butterflies in the country was the highest in the case of about 40 square kilometers of semi-natural grassland per 100 square kilometers, though the value varied somewhat with latitude. The expected maximum species richness of birds was the highest in the case of about 60 square kilometers of semi-natural grassland per 100 square kilometers. This study showed that the decrease in semi-natural grassland in Japan has resulted in far from ideal conditions for many species

Kohyama, K.

Sasaki, H.

Shoji, A.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings XIX International Grassland Congress Optimum Area of Semi-Natural Grassland to Maintain Maximum Butterfly and Avian Species Richness in Japan A. Shoji National Grassland Research Institute, Japan K. Kohyama National Grassland Research Institute, Japan H. Sasaki National Grassland Research Institute, Japan Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/19/23/6 This collection is currently under construction. The XIX International Grassland Congress took place in São Pedro, São Paulo, Brazil from February 11 through February 21, 2001. Proceedings published by Fundacao de Estudos Agrarios Luiz de Queiroz This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. ID # 23-06OPTIMUM AREA OF SEMI-NATURAL GRASSLAND TO MAINTAIN MAXIMUMBUTTERFLY AND AVIAN SPECIES RICHNESS IN JAPANA. Shoji, K. Kohyama and H. SasakiNational Grassland Research Institute, Nishinasuno, Tochigi 329-2793, JapanAbstractTo evaluate the optimum area of semi-natural grassland to maintain maximumbutterfly and avian species richness in Japan, digitalized grid data of butterfly and aviandistribution, as well as vegetation distribution, throughout the country were used. Afterobtaining logistic regression models explaining the probabilities of occurrence of each specieswith semi-natural grassland area and latitude as variables, the optimum value was calculated.The expected maximum species richness of butterflies in the country was the highest in thecase of about 40 square kilometers of semi-natural grassland per 100 square kilometers,though the value varied somewhat with latitude. The expected maximum species richness ofbirds was the highest in the case of about 60 square kilometers of semi-natural grassland per100 square kilometers. This study showed that the decrease in semi-natural grassland in Japanhas resulted in far from ideal conditions for many species.Keywords: Birds, butterflies, digitalized grid data, logistic regression analysis, optimum area,semi-natural grassland, species richnessIntroductionSemi-natural grassland accounted for more than 10% of the total land area of Japanin the early part of the 20th century (Himiyama at al., 1991). However, by 1990 such land,including temporary grassland such as clear-cut and abandoned cropland, had diminished to3.3% of the country's total land area (Environment Agency, 1994) as a result of theindustrialization of agriculture and animal husbandry in rural areas.Semi-natural grassland is very important as the habitat of many grassland-dependentspecies, especially in countries such as Japan that are dominated by forest communities as theclimax of vegetational succession. The decrease in semi-natural grassland is one of thereasons that many grassland-dependent plant species (about 90) are included in the Red List(Environment Agency, 1997). However, for butterfly and avian species, it has not beenclarified whether the decrease in semi-natural grassland is desirable or not, and the optimumarea of semi-natural grassland has not yet been determined.Using digitalized grid data provided by the Environment Agency, this study clarified(1) which butterfly and avian species decrease or increase with increasing area of semi-naturalgrassland, or have the optimum area of semi-natural grassland in their habitat, and (2) theoptimum area of grassland to maximize species richness.Material and MethodsDigitalized grid data on butterfly, avian, and vegetation distribution, provided by theEnvironment Agency and based on the National Survey on the Natural Environment, wasused to calculate the optimum area of semi-natural grassland to maintain maximum butterflyand avian species richness.For butterflies, a distribution survey of the whole country was conducted for twoyears from 1989, as a part of the Animal Distribution Survey (All-Species Survey) of the 4thNational Survey on the Natural Environment by the Environment Agency. For birds, the sametype of survey was conducted in 1978 as the nationwide breeding bird survey of the 2ndNational Survey on the Natural Environment. All of the distribution data consisted of codenumbers for species present in every 2nd Section (about 10 km X 10 km) of the Grid SquareSystem, which uses lines of longitude and latitude to divide the whole country intorectangular sections (Administrative Management Agency, 1973).The vegetation data was recorded as precisely classified community code numberdominant in the center area of every 3rd Section (about 1 km X 1 km, divided section of the2nd Area Section into 10 X 10 parts of equal length and breadth) of the Grid Square System.The vegetation data obtained after the 4th survey conducted around 1990 was used forbutterfly analyses, and for avian analyses, combined vegetation data of the 2nd and the 3rdsurveys, both of which were conducted around 1980, was used.The enumerations composed of butterfly and avian species code numbers wereconverted into sets of presence/absence (1/0) data for each species every 2nd Section. Fromeach set of vegetation data, the 3rd Section occupied by semi-natural grassland (Zoysia-type,Miscanthus-type and Sasa-type grassland) that might be maintained by means of agriculturalactivities were extracted, and the area of semi-natural grassland was calculated every 2ndSection. Then, the data sets composed of the area of semi-natural grassland every 2nd Sectionwere generated.To explain the probabilities of occurrence for each butterfly and avian species byarea of semi-natural grassland and latitude, multiple logistic regression analyses wereconducted. Logistic regression is a special case of the generalized linear model, and can beused even if the errors are not normally distributed and have no constant variance, instead ofordinary least-squares regression (ter Braak & Looman, 1995). The selection of significantexplanatory variables from among four variables (linear and quadratic terms for grasslandarea and latitude, as including the quadratic terms in the regression equation enables theGaussian curves to be obtained and the optimum values to be calculated) through the stepwiseprocedure and the estimation of parameters using the maximum likelihood principle wereperformed.All the calculated probabilities of occurrence for each species were summedseparately for butterflies and birds in order to calculate the optimum area of semi-naturalgrassland to maintain maximum expected butterfly and avian species richness. Because of thenondifferentiability of the cumulative formula, the optimum values were evaluated afterdrawing the expected species richness curves to the grassland area at each latitude.The analyses were conducted using the statistical software SAS (SAS Institute Inc.,1994).Results and DiscussionSignificant equations accounting for the probabilities of occurrence of 225 species ofbutterflies and 212 species of birds were obtained. The probabilities of occurrence of 18butterfly species increased with increasing area of semi-natural grassland, 69 species had theoptimum area of grassland, the probabilities of occurrence of 42 species decreased withincrease in the grassland area, and 96 species were not significantly regressed with thegrassland area but only with latitude, or had a constant probability of occurrence.For birds, the probabilities of occurrence of 23 species increased with increasing areaof semi-natural grassland, 39 species had the optimum area of grassland, the probabilities ofoccurrence of 20 species decreased with increase in the grassland area, and 130 species werenot significantly regressed with the grassland area but only with latitude, or had a constantprobability of occurrence.The cumulative value of all the probabilities of occurrence of butterflies, whichmeans the expected species richness of butterflies, was largest in the 2nd Sections containingabout 40 square kilometers of semi-natural grassland, although slight latitudinal differenceswere recognized and the value was largest in the 2nd Sections having no semi-naturalgrassland at high latitude (Fig. 1). The reason appeared to be that the Sasa-type grasslandwhich is dominant in Hokkaido, the most northerly main island, has little floristic diversity.The expected avian species richness was largest in the 2nd Sections containing about60 square kilometers of semi-natural grassland, although slight latitudinal differences wererecognized (Fig. 2).In most areas of Japan, agricultural activities are indispensable for maintenance ofsemi-natural grassland to prevent vegetational succession. However, after the period of rapideconomic growth in the latter half of the 1950s, the industrialization of agriculture and animalhusbandry in rural areas caused the conversion of some semi-natural grassland into highlyproductive artificial grassland composed of introduced species, and dependence on importedforage resulted in disuse or forestation of a large area of semi-natural grassland.This study showed that maximum expected values of species richness of butterfliesand birds could be maintained if semi-natural grassland occupied an area much larger than itdoes at present. Decrease in semi-natural grassland implies far from ideal conditions for manyspecies. Reuse of semi-natural grassland might be the only way to improve the national foodself-sufficiency ratio while increasing the nation's biodiversity.ReferencesAdministrative Management Agency (1973). The Grid Square System and Grid Codes forStatistical Use. Administrative Management Agency Announcement, 143. Tokyo.Environment Agency (1994). Report of the fourth vegetation survey. 390 pp. Tokyo.Environment Agency (1997). Red List of Threatened Plants of Japan. Tokyo.Himiyama, Y., Iwagami M. and Inoue E. (1991). Reconstruction of land use of Japan circa1900-1920. Reports of the Taisetsuzan Institute of Science, 26: 55-63 Hokkaido University ofEducation, Asahikawa.SAS Institute Inc. (1989). SAS/STAT user's guide, version 6, fourth edition, 943 pp. SASInstitute Inc., Cary, NC.ter Braak, C.F.J. and Looman, C.W.N. (1995). Regression. Pages 29-77 in R. H. G.Jongman, C. F. J. ter Braak & O. F. R. van Tongeren eds. Data Analysis in Community andLandscape Ecology (New ed.), Cambridge University Press, Cambridge.Figure 1 – Effects of semi-natural grassland on expected butterflies species richnessFigure 2 – Effects of semi-natural grassland on expected birds species richness.

Optimum Area of Semi-Natural Grassland to Maintain Maximum Butterfly and Avian Species Richness in Japan

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Optimum Area of Semi-Natural Grassland to Maintain Maximum Butterfly and Avian Species Richness in Japan

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