密度对四季竹叶片C、N、P化学计量和养分重吸收特征的影响

Effects of stand density on Oligostachyum lubricum leaf carbon, nitrogen, and phosphorus stoichiometry and nutrient resorption

以四季竹纯林为对象,研究了4种密度(D1:24600～29800株·hm-2;D2:37500～42600株·hm-2;D3:46500～52800株·hm-2;D4:76500～85500株·hm-2)下1～3年生立竹的成熟叶和凋萎叶的C、N、P化学计量特征及养分重吸收规律.结果表明:随竹林密度的增大,成熟叶C、N、P含量和凋萎叶C、P含量总体下降,凋萎叶N含量先升高后降低,D4密度时成熟叶C含量急剧下降;叶片C/N和C/P呈升高趋势,N/P先升高后降低.D3、D4密度的叶片N、P养分利用效率显著高于D1、D2密度;叶片N、P重吸收率分别呈先降后升和持续升高的趋势.D1～D3密度的成熟叶N/P为16.24～19.37,四季竹生长受P的限制,促进叶片建成,种群生长旺盛.D4密度的成熟叶N/P为13.42～15.74,N限制作用增强,叶片凋萎脱落,种群生长受到抑制.四季竹通过调节叶片的C、N、P含量及其化学计量比,提高了N、P利用效率及重吸收能力,以适应高密度下环境资源的激烈竞争.在本试验条件下,D3密度是四季竹适宜的经营密度.

Taking pure Oligostachyum lubricum forest as test object, this paper studied the matured and withered leaves carbon （C）, nitrogen （N） , and phosphorus （P） stoichiometry and N and P resorption patterns of 1-3 years old stands at the densities of 24600-29800 stem·hm^-2 （ D1 ）, 37500-42600 stem·hm^-2（ D2 ） ,. 46500 - 52800 stem·hm^-2 （ D3 ）, and 76500 - 85500 stem·hm^-2 （D4）. With increasing stand density, the matured leaves C, N, and P contents and withered leaves C and P contents had an overall decrease, the withered leaves N content decreased after an initial increase, and the matured leaves C content at density D4 decreased dramatically. The leaf C/N and C/P ratio increased with increasing stand density, whereas the leaf N/P ratio in- creased first but decreased then. At stand densities D3 and D4, the leaf N and P utilization efficien- cies were significantly higher than those at D~ and D2. With increasing stand density, theleaf N re- sorption capacity increased after an initial decrease, while the leaf P resorption capacity increased steadily. At stand densities D1 -D3, the matured leaves N/P ratio was 16.24-19.37, suggesting that the P limitation occurred, leaf establishment increased, and population increase and expansion enhanced. At density D4, the matured leaves N/P ratio was 13.42-15.74, implying that the N limitation strengthened, leaf withering and defoliation increased, and population increase inhibited. All the results indicated that O. lubricum could regulate its leaf C, N and P contents and stoichiom- etry and enhance the leaf N and P utilization efficiency and resorption capacity to adapt to the severe competition of environment resources at high stand density. In our experimental condition, 46500- 52800 stem·hm^-2 could be the appropriate stand density for 0. lubricum management.