1月の公開セミナー

水田農業の集約化に伴い、食糧生産の効率が向上した一方、生物多様性の減少が報告されている。集約化の影響は、種によって異なる可能性があり、その程度や原因を明らかにすることは、効率的な保全対策を進めるうえで重要な知見となるだろう。本研究は茨城県霞ケ浦南岸の水田地帯において、主要な脊椎動物である鳥類（チュウサギ）、魚類（ドジョウ）、カエル類を対象として、圃場整備が個体数および空間分布に与える影響を評価した。本セミナーではその結果について報告する。

昆虫の性フェロモンは、香りにまつわる天然化合物の中でも、最も顕著で観察しやすい機能性を発揮するもののひとつであろう。カイコをはじめとするガ類のメスが生産・放出する性フェロモンは、数メートル以上離れたオスにも作用することはよく知られるところである。一方で、コナカイガラムシ科の昆虫が、ガ類と同様に誘引活性の強い性フェロモンを利用していることはあまり知られていない。コナカイガラムシはカメムシやアブラムシと同じ半翅目に属する小型の昆虫であり、植物の幹や根、果実等に寄生し、主として師管液を吸汁する。メスは幼虫から成虫に至るまで大きく姿を変えることなく幼形成熟し、寿命は長いが翅を持たず、移動性に乏しい。これに対し、オスは幼虫から蛹を経て成虫となる完全変態型の生活環を有する。オス成虫は翅を持ち、飛ぶことができるが、体の大きさはメスの1/10程度しかなく、極めて脆弱である。しかも口器が退化しており、摂食・吸水しないため、長くても数日程度しか生きられない。このような奇妙な雌雄二型の特性から、コナカイガラムシの配偶においては、メス成虫が自らの居場所を的確にオス成虫に伝え、効率的にナビゲートする必要がある。性フェロモンはそのツールとして重要な役割を担っている。

コナカイガラムシを含むカイガラムシの仲間は植物に寄生するため、農業生産においてしばしば深刻な被害をもたらす。近年、日本国内でも被害が急増しており、害虫管理・植物保護の視点からも重要なターゲットである。今回のセミナーでは、コナカイガラムシの性フェロモンの構造や機能の多様性と、害虫防除技術への応用の可能性を紹介する。

Agriculture utilizes regional water resources as well as local resources such as temperature, rainfall, solar energy. While many studies assessed the impacts of climate change on agriculture, there are few studies accounting for dynamical interactions between water resources and crop production. This study proposes an integrated model for assessing both crop productivity and agricultural water resources at a large scale. The integrated model was consisting of five sub-models for the following processes: land surface, crop growth, river routing, reservoir operation, and anthropogenic water withdrawal. I will introduce the model description, and then discuss mainly about the reproducibility of crop yield and water balance at the Songhua river watershed in Northeast China, which has extensive crop land in China including semi-arid climatic areas.

This research project integrally implements dynamical and statistical downscalings and developments of simulation technologies for climate change adaptations (CCA). They are essential for planning strategic estimations and policies for climate change of Kochi Prefecture that is located in the western part of Japan and has complicated topography and various land use. In Kochi Pref., we have serious vulnerabilities to typhoon and heavy rain, and their economic structures strongly depend on the primary industries. We apply the SD methods, first, to obtain detailed climate change scenarios on the river and coastal basins and we also develop the method for stochastic rainfall level. Secondly, we use the climate change scenarios to adaptive simulation technologies for agriculture and water resources/environments, and finally we present local countermeasure options to climate change impact assessments, adaptive strategy, and environmental policy scenarios in Kochi.

With a growing global population and a changing climate, the need to examine the relationship between weather and crop production in global scale is increasingly important. Previous statistical analyses of historical global data on past crop yields and climate conditions have revealed the relationship between weather and crop yield in global scale. However, for simple statistical model, it is difficult to include complex interaction among climate factors or to consider non-linear responses to daily changes of weather condition. On the other hand, it is also difficult to apply process based models of crop growth to global scale prediction of crop production because of the lack of the knowledge about parameter values for each special grid. Here, we propose a synthesis approach in which the key parameters of a process based crop model are statistically estimated by Bayesian statistics using global crop yield data set. This approach should compensate the weak points of both simple statistic approach and the process-based-model approach and enable us to predict the future global crop productivity　more precisely.

The investigation of network dynamics is a major issue in various studies including systems biology, climate system, plant community and so on. One of the essential steps in a dynamics investigation is the parameter estimation in the model that expresses underline phenomena. Recently, a new approach has been proposed for parameter optimization by using differential elimination, to estimate kinetic parameter values of differential eauation system with a high degree of accuracy. I review some articles on the differential elimination method and outline the mathematical foundation, Groebnar basis and Buchberger's algorithm.