求翻译：目前国内外养分研究主要集中在森林受限制养分、养分损失、枯落物分解和森林C平衡问题上，对森林土壤养分的研究极为活跃。是什么意思？

At home and abroad the nutrient research mainly concentrated in the restricted forest nutrient, litter decomposition, nutrient loss and forest c on the issue of balance, extremely active research on forest soil nutrients.