<h4>Associations with symbiotic fungi</h4>
<p>
As all Dipterocarpaceae, <i>Shorea</i> makes symbiotic associations with “higher fungi” (able to produce large fruiting bodies or mushrooms). This kind of  association is called “ectomycorrhiza”. “Ecto-” means “external”, “-myco-” means “fungus” and “-rhiza” means root. Ectomycorrhizas are characterized by a fungal mycelium (mass of fungal filaments) forming a thin mantle around root tips with fungal filaments penetrating between the external root cells but never inside. This association benefits both to the fungus and the tree.  The fungus receives sugar the tree produces by photosynthesis and, in return, the tree benefits from water and nutrients supplied by the fungus. Indeed, since fungal filaments are very thin, they reach water stored in tiny pores of the soil that are not accessible to the tree roots and root hairs. Not all mushrooms are able to form ectomycorhizas, many species are only saprophytes (as for example the oyster mushroom or shiitake) that feed on non-living organic matter such as dead leaves and branches. Numerous mushrooms of ectomycorrhizal species in Malaysian dipterocarp forests belong to the Russulaceae, Boletaceae and Amanitaceae families. If some ectomycorrhizal fungi are poisonous, some are known belonging to the finest and most expensive edible fungi. For example the Italian white truffle (<i>Tuber magnatum</i>) and the fine quality Japanese Matsutake (<i>Tricholoma matsutake</i>) may reach receptively $7500/kg an $1000/kg on the market.  If all trees of the northern temperate hemisphere are ectomycorrhizal, the association is also well represented in the Southeast Asian lowlands with the Dipterocarpaceae family and within the Southeast Asian montane forests that are the center of diversity of the Fagaceae (family including oaks, chestnuts and beeches). On another hand, in American and African tropical forests ectomycorrhizal tree species are scarce.<br />

Symbiotic association between fungi and plant roots are present in more than 80% of plant species (including grasses, strawberries…) but those are mainly of another type called “arbuscular mycorrhizas” that involve microscopic fungi producing soil-borne spore sacs of less than 0.5mm with    filaments (no mycelium) penetrating inside of the plant root cells 
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<h4>Interactions between wood decomposers and ectomycorrhizas</h4>
<p>
Large saprophytic fungi play a key role in forest ecosystems as they are able to degrade wood and produce humus. These below-ground decomposers can become quite large (sometime exceeding 10 meters). Their shapes are visible above ground when they produce fruit bodies or mushrooms. Those are often aligned or in a ring-shape (“fairy rings”). These figures are due to the fact that the underground fungus can only grow towards a zone where it can find food (new organic matter such as cellulose or lignin contained in dead plant parts) and never backwards towards a zone where available resources has already been consumed. This growth pattern forms rings in homogeneous environments and are more dislocated and deformed in heterogeneous conditions. The fungus may also become deadlocked and die if it cannot progress towards a zone with available organic matter or if it looses a competition for space with another growing fungus.  Another feature of these large decomposers is that they are able to displace and bring with them nutrients (nitrogen, phosphorus, sulfur…) to zones where it is needed. For example within a dead tree log where there is otherwise only carbon, oxygen and hydrogen (the elements forming wood) available to the fungi. For the fungus to develop within such log it needs to import nutrients in order to build proteins and enzymes for wood digestion and biochemical processes. Once a deadlocked fungus dies, it releases all the nutrients it accumulated to the profit of other decomposers or mycorrhizal fungi associated to plants. In this context of spatial changes of nutrients and food availability, large ectomycorhizal fungi become “game changers” as they can survive on a given place as long as they can secure a root link with a canopy tree able to provide them with photosynthetic carbohydrates. Ectomycorrhizal fungi also return nutrients to their associated canopy tree instead of translocating them and releasing them in other places. However, the role of ectomycorrhizal fungi in the complex ecology of the Southeast Asian rainforests is widely unknown and many hypotheses are remaining speculations. A puzzling question is  how an association that benefits both to the fungi and the trees not lead ectomycorrhizal trees to out-compete all non-ectomycorrhizal trees as it could have been the case in the forests of the northern temperate hemisphere. An interesting hypothesis could be that seedlings of Dipterocarpaceae are unable to associate with ectomycorrhizal networks supported by canopy trees as in the dim forest understorey they would not have much photosynthetic carbohydrates to share with a fungal partner. On another hand, they could have a fitness advantage establishing in areas where large deadlocked saprophytes are releasing nutrients. A spatial competition between ectomycorrhizal and saprophytic fungal networks would then explain that ectomycorrhizal seedlings would rather regenerate away from ectomycorrhizal canopy trees. Such hypothesis would concord with an equilibrium between the number and spatial distributions of ectomycorrhizal and non-ectomycorrhizal canopy trees as well as with the winged seeds of the Dipterocarpaceae as a adaptation in favor to a regeneration away from ectomycorrhizal networks supported by canopy trees. These ecological processes of species coexistence may explain how the Dipterocarpaceae forests are the grandest formations the earth has ever witnessed with a biodiversity equivalent to that of the Amazon but with an overall taller canopy and unique regeneration capacities compatible with shelter sylviculture systems as in northern temperate regions. 
</p>

<h4>General flowering and mast fruiting</h4>
<p>
A spectacular characteristic of Malaysia’s aseasonal (without seasons) forests are major flowering and fruiting events in which up to 88% of the canopy species, and almost all Dipterocarpaceae will flower, often after several years of sterility. During general flowering, canopy changes from green to yellow and the forest floor is carpeted by millions of tiny corollas. A few months after it is a carpet of fruits that covers the forest floor followed by seedlings. If general flowering or masting is known in other temperate and tropical regions, it is unrivaled by the scale and intensity in the aseasonal dipterocarp forests. Flowering of dipterocarps is often described as either ‘general’ (synchro-
nized and extensive flowering of many species and individuals at supra-annual intervals) or ‘isolated’
(occasional flowering of relatively few species and individuals in non-general flowering years). Flowering events do, in fact, fall along a continuum between these two extremes, both in the proportion of flowering species and intensity of flowering. A hypothesis explaining the advantage of  general flowering and mast fruiting is “predator satiation”.  It relies on the assumption that mast fruiting events generate far more seeds than predators can consume, while long intervals of food scarcity between mast events make reduces the predators populations.
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<h4>Pollination</h4>
<p>
In Malaysian aseasonal rainforests, <i>Shorea</i> tends to reproduce in general flowering events. Individual flowers open in the early evening and throughout the following night. They start wilting during the course of the next day. At night, flowers emit a strong sweet scent but produce little or no nectar. This attracts mainly thrips (mostly 1 mm long insects feeding on flower parts) , beetles, and to a lesser extent bugs that contribute to the pollination. With some exceptions such as <i>Shorea ovalis </i> that produces nectar and is bee-pollinated, Malaysian <i> Shorea </i> species are pollinated by insects that are not specialized for the collection of nectar. <br /> This trend is inverted in more seasonal forests zones where <i> Shorea </i> species tend to flower during the day and attract mainly bees. 
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Shorea sp (Dipterocarpaceae)