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Evaluation of litterfall production is important for understanding nutrient cycling, forest growth, successional pathways, and interactions with environmental variables in forest ecosystems. Litterfall was intensively studied during the period of 1982–2001 in two subtropical monsoon vegetation gradients in the Dinghushan Biosphere Reserve, Guangdong Province, China. The two gradients include: (1) a successional gradient composed of pine forest (PF), mixed pine and broadleaved forest (MF) and monsoon evergreen broadleaved forest (BF), and (2) an altitudinal gradient composed of Baiyunci ravine rain forest (BRF), Qingyunci ravine rain forest (QRF), BF and mountainous evergreen broadleaved forest (MMF). Mean annual litterfall production was 356, 861 and 849 g m−2 for PF, MF and BF of the successional gradient, and 1016, 1061, 849 and 489 g m−2 for BRF, QRF, BF and MMF of the altitudinal gradient, respectively. As expected, mean annual litterfall of the pioneer forest PF was the lowest, but rapidly increased over the observation period while those in other forests were relatively stable, confirming that forest litterfall production is closely related to successional stages and growth patterns. Leaf proportions of total litterfall in PF, MF, BF, BRF, QRF and MMF were 76.4%, 68.4%, 56.8%, 55.7%, 57.6% and 69.2%, respectively, which were consistent with the results from studies in other evergreen broadleaved forests. Our analysis on litterfall monthly distributions indicated that litterfall production was much higher during the period of April to September compared to other months for all studied forest types. Although there were significant impacts of some climate variables (maximum and effective temperatures) on litterfall production in some of the studied forests, the mechanisms of how climate factors (temperature and rainfall) interactively affect litterfall await further study.

To investigate the impact of human disturbance and subsequent recovery on soil nitrogen processes, nitrogen availability during different seasons and at two soil depths in disturbed, rehabilitated and mature forests in tropical China was estimated using the ion exchange resin (IER) bag method. Soil total mineral N (NH4+N+NO3−N) varied significantly depending on forest and season. Overall, total mineral N concentrations ranked as follows: rehabilitated>mature>disturbed (forest); and spring>fall>winter>summer (season). Of the total mineral N, NH4+N was the major form in all forests (about 50–95%) with its proportion varying depending on forest and season. The correlation between NH4+N and NO3−N was strongest in the mature forest, followed by the rehabilitated forest and by the disturbed forest. Harvesting understory and litter had significant effects on soil N—mineral N was higher in treatment plots (more disturbed) than in control plots (relatively less disturbed). Although mineral nitrogen is produced, fewer plants and low microbial activity lead to low uptake and low immobilization resulting in greater N leaching losses in treatment plots. The results of this study suggest that over the period of 50 year or so, successful rehabilitation of soil N availability on severely degraded lands is possible, however, as long as harvesting of understory and litter continues in the degraded forest, this rate and level of recovery is unlikely to be realized.

The effects of litter and understory harvesting by local people on the nutrient cycle in a pine forest in Dinghushan Biosphere Reserve (DHSBR) of subtropical China were studied by quantifying nutrient distribution, recycling, and loss in the ecosystem. The total nutrient standing stocks were estimated to be 2066 kg ha-' for N, 282 kg ha-' for P, 541 kg ha-' for K, 491 kg ha-' for Ca, and 151 kg ha-' for Mg. Most of these nutrients were contained in the top 10 cm of soil (72 to 94%). The total quantity of nutrients in the production of litterfall and understory were: 43.5 kg ha-' yr-' for N, 1.7 kg ha-' yr-' for P, 16.1 kg ha-' yr-' for K, 10.9 kg ha-' yr-' for Ca, and 2.7 kg ha-' yr-' for Mg. The harvest practice removed substantial quantities of these nutrients, 44 to 73 percent of the amount in litter and understory production, a rate that appeared to exceed most nutrient inputs from atmospheric deposition. In addition to the direct removal of nutrients, the harvest practice also reduced the active soil organic matter pool thus reducing nutrient mineralization and soil nutrient availability. An alternative system of tree harvest and replanting, combined with litter removal only, was proposed that reduced by one-third or more the present nutrient removals.

A common practice by rural people in China is to harvest litter and understory from forests to meet their fuel needs. Our study was to determine the impact of this practice, occurring for over 40 yr, on the storages and flows of organic matter in a native pine forest in the Dinghushan Biosphere Reserve. This forest was established to rehabilitate severely degraded lands, and trees were not allowed to be harvested but understory plants and litter were harvested. Despite the initial condition of the site, its relatively young state, and the continued removal of understory plants and litter, there was total of 45 plant species in the study site. The total standing stock of organic matter was 135 Mg ha-' with about 60 percent in the trees and 28 percent in the top 10 cm of soil. Understory and litter, the two components harvested, were about 4 percent of the total standing stock. Total aboveground biomass production was 8.4 Mg ha-' yr- , with about 45 percent contributed by the understory. The average annual amount of litter and understory harvested (3.3 Mg ha-') was 55 percent of the annual production. Compared with adjacent similar-aged broadleaf and mixed pine-broadleaf forests and other tropical pine forests where organic materials were not harvested, our site had less structural complexity and was cycling organic matter more slowly than its potential. Harvesting the net production of trees, with a replanting program, coupled with litter removal only provided the same quantity of organic matter, but was proposed as a more efficient method of fuel production because it would allow the soil organic matter, soil fertility, and tree regeneration to improve, while at the same time provide a higher quality fuel and reduce the time expended by women in fuel gathering.