Comparison Of Above And Belowground Organs Litter Decomposition In Two Soil Substrates

Litter and its decomposition are crucial processes of carbon and nutrient cycles and substantially affect forest regeneration and species diversity of soil microorganisms. Interspecific variation in decomposition of litter that derived from various organs, such as roots, leaves, and woody debris, has been cumulative researched in the past decade. In addition, plant functional traits are widely utilized to predict such variation in plant litter decomposition. Due to the difference of resource conditions in diverse ecosystems, plants form different ecological strategies for metabolization and nutrient acquisition and thereby vary in plant functional traits. Previous studies have shown that plant litter decomposability is correlated with ecological strategy in several ecosystems. In the long process of carbon and nutrient exchange and recycle, plants coordinate traits of the above and belowground organs to adapt to climate and resource conditions of the growth region. However, the consequences of such coordination for correlation between different organs’litter decomposability across species is less known. Therefore, our aim is to investigate the relationship between ecological strategy and litter decomposability in mid-subtropical areas, and understand links between above and belowground ecosystem.We analyze the litter decomposition of above and belowground organs after one year and two years of incubation by using the litter-bag method. We collected litter materials from various plant organs (fine roots and coarse roots, twigs, leaves) from two contrasting sites, one being a limestone area that has low moisture content and soil nutrient, and the other is a sandstone area which is dominated by evergreen board-leaved forest. Each organ types of the same species were collected from more than three trees. Then we placed these litters, in litterbags, to decompose in two kinds of incubation substrates (sandstone and limestone) in a common site (106°24’E,29°49’N) for two years of incubation. Litter bags with leaves and twigs were placed on the surface of the soil, roots materials were placed at15cm depth in the soil. All litter bags in the incubation bed were non-overlapping. Litter mass loss after one and two years of incubation was expressed by the negative exponential function of Olson to calculate litter decomposability (K). Subsamples of initial and harvested litter were ground and analyzed for carbon, nitrogen, calcium, potassium, magnesium, and manganese.Our results show as follow:1. Litter decomposability is differs significantly between across organs. Decomposability of fine roots and coarse roots is greater than that of leaves, and twigs decay slowest. Litter decomposability of different organs is positively correlated across species, i.e. species with high leaves decomposability also show relatively high decomposability of other tissues. Moreover, a comparison of decomposability of plants of two life forms that were collected from the two sampling areas and incubated in two substrates, shows that litter from evergreen plants decomposes significantly slower (P<0.05) than that of deciduous plant across all organs (except for fine twigs). The differences in decomposability of plant organs of evergreen plants and deciduous plants were constant across sampling areas and incubation substrates.2. Nutrient concentration shows significant difference in litter and among various organs. Litter nutrient concentrations from high to low arranged in order of C, Ca, K, N, Mg, P, and Mn. Carbon concentration is the highest in litter with average value467.102g/kg, and phosphorus concentration is the lowest in litter major element with average value0.455g/kg. Among four litter organ types, we find that N concentration and K concentration of leaves are higher than that of roots; twigs have the lowest value in these two element. The Ca concentration in litter from high to low are as follow: leaves>twigs>roots. P concentration is lowest in Twigs, whereas Mn concentration is highest in leaves. Litter mass loss is significant positively correlated with initial N, P, K, and Mg concentrations. However, it is significant negatively correlated with initial C concentration. After one year decay, nutrient changes are different among various litter types. It comes out that nutrient changes of twigs are higher than that of other organ litter, except C and Mn. And leaves Mn changes are significant higher than other litters. It shows no difference of nutrient changes between fine roots and coarse roots. Litter mass loss increase with nutrient changes of C, K, and Mg. to analysis the correlation of nutrient change between pairs of plant organs across species, the slope of coarse roots-leaves K concentration and fine roots-leaves litter Mn concentration are approximate equal to1.3. Litter decomposabilities differ in two sampling areas and two soil substrates. Fine roots and coarse roots from Haishi Park decompose faster than that from Jinyun Mountain, while decomposition rate of twigs and leaves have no difference between two sampling areas. Both one year date and two years date show same results. After one year decomposition, twigs and leaves decompose differently between soil substrates, and litter decompose faster in sandstone substrate than that in limestone substrate. Litter decomposes two years plays same as one year. Further with comparison of litter decomposabilities of one organ type from same sampling areas in two incubation substrates, the result shows that both Haishi Park and Jinyun Mountain leaves have higher decomposabilities in sandstone substrate than that in limestone substrate, twigs collected from Jinyun Mountain decompose faster in sandstone substrate comparing to limestone substrate. Other organ litters have no difference in sandstone and limestone substrates. P concentration of Haishi Park plant litter is significantly higher than Jinyun Mountain. Among four mental element content (include K、Ca、Mg、Mn), litter from Haishi Park has higher mental concentration than Jinyun Mountain, except Mn.Plant species show positive connection in litter decomposability and nutrient changes across organs. The strategy by which plants use resources shows proportional related among different organs traits. This implies that plant ecological strategy and litter decomposability are linked by plant functional traits, which improves our understanding relationships among plants, soil, and litter.