Summary1. Insect herbivory may have not only negative but also positive plant-mediated effects on other insect herbivores. We investigated plant-mediated effects of the stem gall midge Rabdophaga rigidae on other insect herbivores through regrowth response of the willow Salix eriocarpa. 2. Gall initiation on current-year shoots stimulated the development of lateral shoots, followed by a secondary leaf flush. Lateral shoots and upper leaves on galled shoots were less tough and had a higher water and nitrogen content. 3. Colonization rates by the aphid Aphis farinosa were significantly higher on galled shoots than on ungalled shoots, because this aphid frequently colonized lateral shoots. 4. Adults of two leaf beetles, Plagiodera versicolora and Smaragdina semiaurantiaca , were more abundant on galled than on ungalled shoots; they preferentially fed on young leaves produced during the secondary leaf flush. 5. Gall initiation positively affected aphids and leaf beetles by enhancing the availability of food resources as a result of the regrowth responses of S. eriocarpa . This indicates that the regrowth responses of plants to insect herbivory provide an important mechanism responsible for positive effects on other insect herbivores.

Temperature affects a cascade of ecological processes and functions of forests. With future higher global temperatures being inevitable it is critical to understand and predict how forest ecosystems and tree species will respond. This paper reviews experimental warming studies in boreal and temperate forests or tree species beyond the direct effects of higher temperature on plant ecophysiology by scaling up to forest level responses and considering the indirect effects of higher temperature. In direct response to higher temperature (1) leaves emerged earlier and senesced later, resulting in a longer growing season (2) the abundance of herbivorous insects increased and their performance was enhanced and (3) soil nitrogen mineralization and leaf litter decomposition were accelerated. Besides these generalizations across species, plant ecophysiological traits were highly species-specific. Moreover, we showed that the effect of temperature on photosynthesis is strongly dependent on the position of the leaf or plant within the forest (canopy or understory) and the time of the year. Indirect effects of higher temperature included among others higher carbon storage in trees due to increased soil nitrogen availability and changes in insect performance due to alterations in plant ecophysiological traits. Unfortunately only a few studies extrapolated results to forest ecosystem level and considered the indirect effects of higher temperature. Thus more intensive, long-term studies are needed to further confirm the emerging trends shown in this review. Experimental warming studies provide us with a useful tool to examine the cascade of ecological processes in forest ecosystems that will change with future higher temperature.

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Summary 1.Following the passing of a typhoon over central Japan in late August 2001, a largescale flood occurred owing to the heavy precipitation. Willow trees on the banks of the Yasu River were badly damaged. In the following year, we examined the effects of the flood on the regrowth response of a willow, Salix eriocarpa (Franch), and its subsequent effects on the densities of a leaf beetle, Plagiodera versicolora (Laicharting), and its predators. 2. We used 10 randomly selected pairs of heavily and lightly damaged trees. Field observations showed that the number of sprouting shoots was significantly greater on heavily damaged trees than on lightly damaged trees. The sprouts continued to grow until August, producing lateral shoots and leaves. 3. The numbers of leaf beetles at all developmental stages (egg, larva, pupa and adult) significantly increased on heavily damaged trees as compared to numbers on lightly damaged trees. Adults of the leaf beetle aggregated predominantly on sprouting shoots throughout the growing season. 4. As a result of the increase in the number of leaf beetles, leaf herbivory on heavily damaged trees was significantly greater than on lightly damaged trees. 5. Two arthropod predators, the larvae of the ladybird Aiolocaria hexaspilota (Hope) and the web-building spider Agelena opulenta (L. Koch), also increased significantly on heavily damaged trees. These findings indicate that the flood caused by the typhoon initiated bottom-up cascading effects from the willow to arthropod predators through herbivorous insects by increased foliage sprouting.

This data paper reports tree census data collected in a network of 34 forest sites in Japan. This is the largest forest data set freely available in Japan to date. The network is a part of the Monitoring Sites 1000 Project launched by the Ministry of the Environment, Japan. It covers subarctic to subtropical climate zones and the four major forest types in Japan. Forty-two permanent plots, usually 1 ha in size, were established in old-growth or secondary natural forests. Censuses of woody species ‡15 cm girth at breast height were conducted every year or once during 2004 to 2009. The data provide species abundance, survivorship and stem girth growth of 52,534 individuals of 334 tree and liana species. The censuses adopted common census protocol, which provide good opportunities for meta-analyses and comparative studies among forests. The data have been used for ecological studies as well as for the biodiversity reports published by the Ministry of the Environment.

T. 2006. Trunk cutting initiates bottom-up cascades in a tri-trophic system: sprouting increases biodiversity of herbivorous and predaceous arthropods on willows. Á/ Oikos 113: 259 Á/268.We examined the effects of trunk cutting on the regrowth responses of two dominant willow species, Salix eriocarpa and S. gilgiana , and the subsequent effects on the community structure (abundance and species richness) of herbivorous and predaceous arthropods. We studied ten randomly selected pairs of cut and uncut (control) trees of each willow species. Field observations showed that when the trunks were cut, shoots sprouted from the base and developed rapidly. These shoots continued to grow until July, producing lateral shoots and leaves, whereas current-year shoots on uncut trees essentially stopped growing by April. In July, the upper leaves of cut trees were less tough and had a greater water and nitrogen content than leaves of uncut trees. Leaf consumption and abundance and species richness of both herbivorous and predaceous arthropods were significantly greater on cut trees than on uncut trees in both willow species. Overall, trunk cutting resulted in at least a two-fold increase in both relative abundance and species richness within the arthropod community on the willow species. We concluded that the severe physical damage caused by trunk cutting greatly increased the biodiversity of herbivorous and predaceous arthropods through bottom-up cascading effects.

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