Dipterocarpaceae: forest fires and forest recovery

 One of the serious problems Indonesia is facing today is deforestation. Forests have been playing a very important role in Indonesia as the main natural resources for the economic growth of the country. Large areas of tropical forests, worldwide considered to be among the richest in plant diversity, have been lost in recent years mainly due to inappropriate logging, illegal logging, shifting cultivation, and forest fires. The negative repercussions of these activities are felt from an economical as well as from an ecological point of view.Time and again, Indonesia has experienced severe droughts often resulting in large forest fires. The fires used to occur only sporadically but now occur regularly every approx. 4 years in the area, with the largest and most destructive ones so far taking place in 1997-98. This climatic phenomenon was linked to a particularly pronounced El Niño Southern-Oscillation (ENSO), combined with numerous fires closely connected with human activities.'Dipterocarpaceae: Forest fires and forest recovery' discusses a comprehensive ecological understanding of fires, an overview of forest dynamics after fires, and the restoration strategies of the forest. Planting materials are reviewed in terms of their genetic diversity and their growth in different soil substrates, with various mycorrhizal inoculations and levels of light. The present publication is the last in a series adding information to the earlier projects conducted by Smits (1994), Yasman (1995), Hatta (1999) and Omon (2002).Microclimatic conditions change considerably after forest fires. The burned forest was characterized by elevated levels of light intensity and heat, and significantly reduced levels of humidity. After the fires, the natural dynamics of forest, in terms of regeneration of plants and butterfly communities, was set back to an earlier development phase where there were no more trees, only 2.5% of saplings survived and all saplings shorter than 5 m died. The butterfly community in the burned area had high densities of pioneer species associated with disturbed habitats. Burning caused a significant shift in the forest butterfly community. There was a highly significant variation in sapling and seedling density, diameter, and species richness between burned and unburned forest. Even though sapling height was significantly greater in burned than in unburned forest, there was no significant difference between their growth in both forests. The growth of both saplings and seedlings was completely unaffected by any edge effect in both forest types. The species richness, density and height of seedlings were significantly greater in unburned forest but their growth was significantly greater in burned forest. The diverse seedling community of unburned forest was replaced by a species-poor community of pioneers dominated by Euphorbiaceae.Dipterocarp forests can recover from fire impact if the damage is not too extensive and the fires are not recurrent, but their natural recovery is too slow to make it economically interesting, and therefore foresters try to restore the desired state of high forest as soon as possible. Their measures are based on the fact that similar microclimatic conditions in both forest types were reached within two years, so assisted recovery can be implemented soon in the burned area by introducing valuable climax tree species i.e dipterocarp species, before they would arrive spontaneously.Such operations require seedlings. Key issues for the management of dipterocarp stock plants in the nurseries included genetic diversity of the seedlings, choice and preparation of appropriate potting mixes, species-soil original matching, nursery hygiene and mycorrhizal inoculation. Cuttings grown in sandy loam showed a stronger and faster growth than the cuttings in sandy clay loam and loam. The higher sand fraction in the soil provided a good aeration for mycorrhizae and plants roots. Pasteurised soil media increased the growth of seedlings in the nursery. It is assumed that composition, acidity, moisture content and heat of the rooting media can be combined in a treatment optimising the conditions for both root development and root colonisation by fungi, thus increasing the quality and quantity of seedlings produced. It was found that interactions between so many factors lead to a highly complex situation, far from easy to control.S. leprosula proved to be very homogeneous as expressed from the similarities in frequencies of the band patterns. The similarity was relatively high between eastern, central and western Kalimantan populations but the nearer the geographic distance the more similar the populations.The initial inoculation supported S. leprosula to start growing in the greenhouse. In the established dipterocarp nursery, the spores of mycorrhizal fungi inoculated seedlings easily and freely. In 15 months in the greenhouse, all seedlings were colonised by these mycorrhizal weed fungi. Laccaria sp. was the most common one, followed by Thelephora sp. , Riessiella sp. and Inocybe sp . After 12 months in the field, the species composition of mycorrhizal fungi involved in root colonisation changed again. Inocybe sp . was still there, with two new other species being most abundant, namely Amanita sp. and Scleroderma sp. Even though the growth of S. leprosula seedlings in the nursery was supported by initial inoculation, in the field, no initial inoculation seedlings showed a stronger growth because they benefited more from the late stage fungi infecting the plants at the planting location.When dipterocarps are used, the key to success for a dipterocarp planting is species choice and light control. Selecting species suited to the local soil and site conditions is essential. Light control should correspond to the light requirements of a species during its growing stages, so planting methods should reflect site conditions and growth characteristics of the species. S. leprosula is a light-demanding species at the early stage, 60 to 73% (relative light intensity) for seedlings and 74 to 100% for saplings.The assisted recovery of pure Imperata cylindrica areas after fires is accelerated using mixed plantations composed of indigenous fast-growing pioneer tree species, i.e Peronema canescens that offer suitable conditions for the establishment of indigenous dipterocarp species. In circumstances without stress by fire, a young P. canescens tree has a well-developed monopodial trunk with a light canopy so that the light intensity under this species is very high or not much lower than in the open site. This shade condition (semi-closed) is not very suitable for S. leprosula seedlings when under-planted under this species. The capacity of P. canescens after fires to reiterate abundantly ('traumatic reiteration') and converge architecturally from Scarrone's model to a physiognomy resembling Leeuwenberg's model provided more favourable environmental conditions for S. leprosula to grow under the canopy of these trees (closed stand). Within almost three years, S. leprosula saplings in a closed stand and in a semi-open area reached a height of 281 to 283 cm and a diameter of 33 to 34 mm, whereas in the open area and under the semi-closed canopy of. P. canescens they were only 165 to 193 cm high and 22 to 27 mm in diameter.Long-term survival of a species depends on its ability to adapt to environmental change. Adaptability is a two-sided process. It rests on the optimal match between a genotype (organism) and its direct environment (ecosystem patch or 'eco-unit'). It is important to understand the reaction of the plants, so as to select genotypes adapted and adaptable to environmental stress in new environments. For this reason, next to the taxonomical data of S. leprosula , the architectural model and its reiteration are also described in this book.In Chapter 7 an overview is provided of the fire and forest regeneration issues with special reference to the Dipterocarpaceae and Shorea leprosula . Much practical information is provided on conditions for a successful regeneration of Dipterocarpaceae. It is concluded that the Dipterocarpaceae have become a threatened plant family and that safeguarding the genetic diversity of Shorea leprosula is highly urgent. If Dipterocarpaceae are to survive, the issue of fires must be resolved and dealt with.