光强对四种亚热带树苗生长特征影响的比较

鼎湖山亚热带森林优势树种藜蒴、荷木、黄果厚壳桂和马尾松2－3年生树苗，盆栽于16％、40％和100％的自然光下生长16个月．3种阔叶树无论在全自然光还是在弱光下均能较好地存活，遮光下的马尾松则出现不同程度的死亡．全光下的马尾松、黄果厚壳桂树苗的基径和树高生长大于遮光下的树苗．4个树种的侧枝数均随光照的减弱而下降．在不考虑新老叶更新的情况下，全光下的藜蒴、黄果厚壳桂单株叶片数大于弱光下的树苗，而荷木则相反．如果以全光下单株树苗干物质量为100％，那么在相对光照为40％和16％下生长的马尾松、黄果厚壳桂、荷木和藜蒴单株树苗的干物质量分别为57．4％和32．7％、73．8％和62．1％、78．0％和78．6％、93．9％和76．2％．不同光强下的藜蒴、荷木地上部分干物质量的变化不大，地下部分则随光照的减弱而下降，马尾松、黄果厚壳桂无论地上还是地下部分干物质量均随光强的减弱而明显减少．遮光下生长的3个阔叶树种树苗的冠根比（CRR）、叶重比（LWR）、叶面积比（LAR）和比叶面积（SLA）均高于全光下的树苗．马尾松为喜光树种，对阴生环境的适应能力极为有限；黄果厚壳桂为耐阴树种，在全光下仍然比遮光条件下生长较快．

A COMPARATIVE STUDY ON THE GROWTH RESPONSES TO LIGHT INTENSITY IN SEEDLINGS OF FOUR SUBTROPICAL TREE SPECIES

Transplanted 2 to 3-year-old seedlings of Castanopsis fissa, Schima superba,Cryptocarya concinna and Pinus massoniana from Dinghushan subtropical forest were pottedunder 16%, 40% and 100% of full sunlight for 16 months. Growth and dry masspartition at all light levels were measured. Seedlings of P. massoniana survived much betterin full sunlight than in shade, other 3 broad-leaf species survived well in both conditions.Seedling heights and diameters of P. massoniana and C concinna after transplanting for 16months were greater in full sunlight than in shade. The number of branches declined withdecreasing light intensity for all species. The number of leaves was greater in shade than infull sunlight for C.concinna and C.fissa ,but lower for S.superba ,when leaf fall was negligible. Expressed as a portion of peak dry mass at 100%, the relative whole plant drymass for species grown under 40% and 16% sunlight was 57.4% and 32.7% (P. massoniana),73. 8% and 62.1 % (C. concinna), 78.0% and 78.6% (S. superba), 93.9% and 76.2% (C.fissa), respectively. For Castanopsis fissa, Schima superba, aboveground dry mass showedlittle variation among treatments, but root dry mass declined with decreasing light intensity,while both above- and underground dry mass for Cryptocarya concinna, Pinus massonianadropped markedly with decreasing light intensity. Crown-root ratio (CRR), leaf-plant weightratio (LWR), leaf area ratio (LAR) and specific leaf area (SLA) were higher in shade thanin sunlight for all the 3 broad-leaf species. P. massoniana, a sun-loving species, had muchlimited potential in acclimating shade environment, while C. concinna was considered shadetolerant species, yet grew more rapidly in full sunlight.