Forest Leaf Litter Decomposition As Affected By Soils And Plant Growth

Litter decomposition accounts for an important status in cycles of materials, as not only relates to mineral nutrients cycles which are essential for plant nutrition, but also relates to carbon cycle that influences the greenhouse effect. Datum ago concerned litter decomposition mostly put stress on the microbes and soil animals, etc, while researches about the effect of soil and plant growth/living roots on litter decomposition were few. In this topic, that whether living roots have acceleration to litter decomposition and soils from south and north have obviously difference on the decomposition, as well as the dynamic of litter decomposition and the changes of organic and inorganic components will be investigated.This study was conducted in glasshouse of China Agricultural University(CAU), litter-bag and root-bag were used to study the dynamic of leaf litter decomposition and the effects of soil, exogenous nutrient application and plant growth on leaf litter decomposition.In litter-bag approach, the fresh leaf litters from wildwood and secondary forest of Xishuangbanna Botanical Garden wre mixed, and soils of 0~2.5cm and 2.5~7.5cm depth were sampled from the same places, as well as from plantation forest of Beijing BaiWang Mountain, litter-bag (1mm mesh) with 20 g leaf litter was put into soils of pots, wich were divided into planted and unplanted treatments, including two sub-experiments: ( 1 ) The unapplied nutrition experiment of 90 days showed that: ? the remains and the content of C and cellulose of leaf litter was gradually reduced as process of experiment, while lignin content only reduced a little; (2) the concentration of nutrients such as N, P, Ca, Mg, Mn, B increased and K, Fe decreased. (3) The topsoil of secondary forest was the most advantageous for leaf litter decomposition and the subsoil of wildwood was the lowest. Apart that plantation forest in Beijing was inverse, the ratios of leaf litter decomposition in topsoil were bigger than that in subsoil. (4) Living roots relatively restrained the decomposition of leaf litter compared with the controls. (II) The applied nutrition experiment of 120 days showed that: (1)changes of organic and inorganic components of leaf litter ware similar with experiment ( I ), yet relatively to experiment ( I ), the supply of nutrition speeded up the decomposition of organic components in leaf litter which was put into the planted soils and delayed that in unplanted soils, and hastened the accumulation or release of mineral nutrients in decomposing leaf litter. (2) Compared with experiment ( I ), that had the fastest speed of leaf litter decomposition wasn't the topsoil of secondary forest but the topsoil of Beijing plantation, and the slowest was still the subsoil of wildwood.(3) the effect of plant growth on leaf litter decomposition was same with experiment ( I ).The site and treatments of root-bag method were the same with litter-bag method, the differences were: leaf litter was sampled from Beijing plantation forest, grinded and sifted with lmm mesh, then 200 g leaf litter were put into root-bag with 40um mesh. The root-bag open on the top which can sow plant was implanted in soil; soil from the test-field of CAU was the topsoil of 0~10cm depth. The results showed that: except that the content of lignin increased a little, the concentration of Fe increased and Mn decreased, the changes of other components of leaf litter showed the similar dynamics as that inlitter-bag method. The action of plant showed that: in unapplied nutrition experiment of 90 days, plant growth accelerated the decomposition of leaf litter compare with controls; in applied nutrition experiment of 120 days, the influence of plant growth on decomposition changed from planted > control to control > planted.The compare of the ninety weight loss datum of litter-bag and root-bag educed that: (1) in planted soils, those treatments which were supplied nutrition restrained decomposition; (3) while in unplanted soils, those supplied nutrition accelerated decomposition of leaf litter.Some chemical properti...