桂西北喀斯特区原生林与次生林凋落物及养分归还特征比较

森林凋落物是森林生态系统的重要组成成分,其养分归还量在一定程度上决定着土壤养分有效性的高低。在土层浅薄且土被很不连续的我国喀斯特区域进行凋落物生物量及养分归还研究对我们更深刻地了解该区养分循环具有至关重要的意义。本文比较分析了桂西北喀斯特区3种原生林与3种次生林的全年凋落物量、组成、月凋落物量动态及养分归还量与动态。结果表明,圆果化香(Platycarya longipes Wu)、大叶蚊母树(Distylium Sieb.et Zucc.)与青檀(Pteroceltis tatarinowii Maxim.)3种原生林的年凋落物总量分别为2342.16,4057.99和1834.36kg·hm-2,而圆叶乌桕(Sapium rotundifolium Hemsl.)、八角枫(Alangium chinense(Lour.) Harms)和黄荆(Vitex negundo L.)3种次生林的年凋落物总量分别为3192.82,3284.26,2469.90kg·hm-2,除大叶蚊母树外,次生林年凋落物总量大于原生林。凋落物的组成中,叶凋落生物量均占总凋落物量的80%左右,甚至更高,而圆叶乌桕、八角枫和黄荆3种次生林群落的叶凋落物量占总凋落物量的百分比大于圆果化香、大叶蚊母树以及青檀3种原生林。凋落物的养分归还量的月动态与凋落物量的月动态一致,原生林呈"U"形曲线,而次生林则呈"W"形曲线。原生林和次生林凋落物的年养分归还量均为C﹥N﹥K﹥P,且次生林的C、N、P养分的归还量大于原生林。

Comparison of litterfall and nutrients return properties of primary and secon-dary forest ecosystems, the karst region of Northwest Guangxi

Litterfall was the important component of forest ecosystems, and the availability of soil nutrients depends on how much the litterfall nutrients return. The research of litterfall biomass and nutrients return rate was most valuable for us to realize the nutri-ents cycle in the discontinuous soil layer region, karst area of China. This paper investigated the yearly total litterfall biomass, litter-fall composition and monthly dynamic, nutrients return rates and dynamics of 3 primary forests comparing to 3 secondary forests. Results find that, leaf litter composes about 80% of the total litteffall biomass in both primary and secondary forests, and even more. Total yearly litteffail of Round-fruited Dye-tree, Large-leaved Distylium and Wing-hackberry primary forests was 2 342.16, 4 057.99 and 1 834.36 kg·hm~(-2), respectively, and was 3 192.82, 3 284.26, 2469.90 kg·hm~(-2), respectively in three secondary forests of Round-leaved Tallow-tree, Chinese Alangium and Negundo Chaste-tree. Total litterfall mass of secondary forests was larger than those of the primary forests except for Large-leaved Distylium. The nutrients return monthly dynamic fits the litterfall dynamic well, the primary forests was "U" shape from Nov. 2007 to Nov. 2008, while the secondary forest was "W" pattern. Nutrients return rates and quantity of C, N, K, P showed the order of C>N>K>P both in three primary and three secondary forests, and the nutrients return rate and quantity of C, N, P in secondary forests were faster and larger than those of primary forests.