TEMPERATURE-DEPENDENT DEGRADATION OF SOIL ORGANIC MATTER IN FARMLANDS AND PASTURES.

To determine the rates of soil organic matter degradation in farmlands and pastures and their temperature dependency, soil samples collected in Aomori, Japan, were sieved and incubated at different temperatures (10, 20 and 30°C) for 700 d, with amounts of respired CO2 being measured during the incubation period. Results were analysed using a three-compartment model (active, intermediate and resistant compartment), and the decomposition rates of the two labile compartments were approximated using an exponential decay function. The Arrhenius equation was applied to the decay function rate constant to obtain rate constants at the examined temperatures.

On the relationships between leaf-litter lignin and net primary productivity in tropical rain forests.

We investigated if tropical rainforest trees produced more-lignified leaves in less productive environments using forests on Mount Kinabalu, Borneo. Our investigation was based on two earlier suggestions that slower litter decomposition occurs under less productive forests and that trees under resource limitation invest a large amount of carbon as lignin as a defense substance to minimize the loss from herbivores. When nine forests at different altitudes (700-3100 m) and soil conditions (derived from sedimentary or ultrabasic rocks) but with the same gentle relief position were compared, the concentrations of leaf-litter lignin were positively correlated with litterfall rates and leaf-litter nitrogen concentrations.

Warming effects on growth, production, and vegetation structure of alpine shrubs: a five-year experiment in northern Japan.

Warming effects on shoot growth, production, reproductive activity, and vegetation structure of alpine shrubs were measured over 5 years in a mid-latitude alpine fellfield in northern Japan. Open-top chambers (OTC) increased the daily mean air-temperature by 1.5-2.

Leaf phenology, seasonal changes in leaf quality and herbivory pattern of Sanguisorba tenuifolia at different altitudes.

Leaf demography, seasonal changes in leaf quality and leaf-beetle herbivory of a herbaceous perennial plant, Sanguisorba tenuifolia, were compared between low- and high-elevation sites. Leaf nitrogen concentration was higher and leaf mass per area (LMA) was lower at the higher site than at the lower one. At the lower site, with a long growth period, plants produced many leaf cohorts and leaves emerged throughout the growing season.