Quantifying the ecosystem service of non-native weed seed predation provided by invertebrates and vertebrates in upland wheat fields converted from paddy fields

Abstract

The extent of post-dispersal weed seed predation in upland wheat fields converted from paddy fields was quantified in Shizuoka Prefecture, central Japan. We investigated the temporal variability in seed predation of Italian ryegrass (Lolium multiflorum Lam.), a non-native winter annual weed in Japan, during summer after the seed shed in both the field interior areas and boundary strips, and estimated the total seed loss due to predation during the summer. Furthermore, the contribution of invertebrates and vertebrates to seed predation was estimated by using exclosures. The total seed loss due to predation during four months (from late June to late October) in the field interior areas and boundary strips was estimated to be 35-43% (the maximum proportion of seed predation per two weeks = 27%) and 42% (25%), respectively. The seed predators in the field interior areas were vertebrates (rodents or birds) and invertebrates (crickets and ground beetles). In contrast, seed predators in the boundary strips were mainly invertebrates (crickets and ground beetles). The results of this study suggest that predators make a substantial contribution in the depletion of post-dispersal seeds of Italian ryegrass in converted paddy fields.

Postdispersal Weed Seed Predation by Crickets in a Rice Paddy Field after Irrigation Water Recedes

“…The exposed glue on the seed cards was covered in fine sand. In the first trial, seeds of L. multiflorum, which crickets consume without avoidance 9,10 , were used to appropriately evaluate the seed predation intensity at each distance from the field edge. In the second trial, seeds of E. crusgalli var.…”

“…Each control card was placed at the bottom of a cubic cage (side length: 15 cm) of metal wire mesh (mesh size: 0.25 cm 2 ), and the cage was supported 10 cm above the ground by four metal poles 9 . The upper part of each pole was lined with double-sided adhesive tape to keep seed predators out of the cage.…”

“…Postdispersal seed predation by invertebrates, including crickets and carabid beetles, is one of the main causes of weed seed mortality, and may contribute to biological weed control in farmlands 7,9,10,18,20,21,22,25 . Recently, the number of quantitative studies of activity density of invertebrate seed predators 3,5,6,18,23 , weed seed predation by invertebrates 5,6,7,18,20,21,22,23 and the impact of seed predation on weed population dynamics 22 in upland fields have increased, primarily in Europe and the United States.…”

“…Crickets and carabid beetles are important seed predators in paddy areas in Japan 9,10,11 . Crickets 11 and granivorous carabids such as Harpalus 12,13 inhabit the margins of rice paddy fields, including the paddy levees that surround the fields to retain water, during the summer crop-growing season because the field interiors are flooded with irrigation water.…”

Weed suppression by seed-eating crickets in paddy fields

“…雑草の植物体から地表に散布された種子は，その多くがコ オロギ類やゴミムシ類等の種子食動物の捕食によって失われ ることが，近年の研究で明らかになってきた (Westerman et al 2003(Westerman et al , 2005Ichihara et al 2011) 。雑草にとって種子散布は，世 代交代や分布拡大， 個体群の増減に関わる重要な過程であり， 種子捕食の強度によっては雑草個体群が強く抑制される (Zhang et al 1997;Westerman et al 2005) 。そのため種子捕食 は，雑草の生物的防除手段の一つとして，総合的雑草管理 (IWM: Integrated Weed Management)における利用が期待され ている (Westerman et al 2003(Westerman et al , 2005浅井 2011;Ichihara et al 2011Ichihara et al , 2012Ichihara et al , 2014a (Menalled et al 2000;Westerman et al 2003Westerman et al , 2005Heggenstaller et al 2006;Davis and Raghu 2010) 。一方，アジ アの水田地域での研究は極めて少ないが，最近では日本でも， 種子食者による雑草種子の低減効果を評価する取り組みが始 まった (Ichihara et al 2011(Ichihara et al , 2012(Ichihara et al , 2014a; 山下 2011) 。日本 の農地では， コオロギ類やゴミムシ類等の種子食昆虫類， げっ 歯類および鳥類が主な種子捕食者である (Ichihara et al 2011(Ichihara et al , 2014a (Zhang et al 1997;Westerman et al 2003Westerman et al , 2005Heggenstaller et al 2006;O'Rourke et al 2006;Ichihara et al 2011Ichihara et al , 2012Ichihara et al , 2014a …”