茂兰喀斯特地区原始林凋落物量动态与养分归还

Dynamics of Litterfall and Nutrient Recycling in Virgin Forest in Maolan Karst Region

于2007年9月至2008年8月对茂兰喀斯特地区原始林凋落物进行观测,分析了凋落物总量、组分(叶、枝、繁殖器官和其他)凋落量和各组分不同养分含量的月动态变化及养分归还量。结果表明,凋落物月动态变化表现为常绿落叶阔叶混交林一般具有的双峰模式,凋落高峰出现在9至次年1月和4月;年凋落物量为6.9 t·hm-2,其中叶、枝、繁殖器官和其他组分的年凋落物量分别占年凋落物总量的71.0%、15.9%、1.5%和11.6%;凋落物各养分含量以C、Ca和N为主,无明显的月动态规律,养分年归还量由大到小依次为C、Ca、N、Mg、K和P,此与一般非喀斯特地区森林(由大到小依次为C、N、Ca、K、Mg和P)不同;凋落物各组分养分元素含量存在差异,凋落枝N、Mg、P和K含量较低,其他组分C、N、P和Mg含量较高,繁殖器官C、N和Ca含量较低;凋落物中Ca和Mg含量以及Ca和Mg年归还量远高于一般非喀斯特地区森林;K含量及K年归还量低于非喀斯特地区,说明该地区K的缺乏可能制约着喀斯特地区植被的生长。

Litterfall is metabolic product of a forest during its growth,and plays an important role in recycling of matter and energy. In this study,based on the observations of litterfall in a virgin forest in the Maolan Karst region,southwest China during the preiod from September 2007 to August 2008,analysis was done for monthly dynamics of total litterfall,amount of each component( leaves,branches,reproductive organs and others) of the litterfall,nutrient contents in each fraction and amount of nutrient recycled. Results show that evergreen and deciduous broad-leaved mixed forest displayed two peaks in monthly variation of litterfall,appearing in September-January and April. The annual litterfall was 6. 9 t·hm- 2,of which with leaves,branches,reproductive organs,and others accounted for 71.0%,15.9%,1.5%,and11. 6%,respectively. Nutrients in the litters were mainly C,Ca and N,which did not have any apparent law in monthly dynamics. Annual nutrients recycled with litterfall exhibited a decreasing order of: C > Ca > N > Mg > K > P,which differing from the one(C > N > Ca > K > Mg > P) in forests in non-Karst regions. Nutrient contents varied from fraction to fraction of the litterfall. Branches were relatively low in N,Mg,P and K,while the other fractions were relatively high in C,N,P and Mg,and reproductive organs were relatively low in C,N and Ca. The Ca and Mg contents in the litterfall and the amounts of Ca and Mg recycled were much higher than those in common forests in non-Karst regions,while the K content in the litterfall and K amount recycled was lower in the former than in the latter,suggesting that K deficiency is probably the major factor limiting growth of the vegetation in karst regions.