表层土壤湿度和pH值对胖大海幼树幼苗更新的影响

在越南同奈天然文化自然保护区设置150个样地,运用生态学理论,采用Logitic模型和生态学统计方法,分析表层土壤湿度和pH值对胖大海幼树幼苗更新出现频率的影响.结果表明,胖大海幼树幼苗在SL1、SL2和SL3三个阶段的天然更新出现频率均与各林分胖大海的优势度、表层土壤湿度和pH值有密切关系.适合胖大海幼树幼苗更新的表层土壤湿度:SL1阶段是57.7%~78.8%,最适度是68.2%;SL2阶段是64.8%~80.7%,最适度是72.8%;SL3阶段是65%~80%,最适度是73.3%.适合胖大海幼树幼苗更新的表层土壤pH值:SL1阶段是3.5~5.7,最适度是4.6;SL2阶段是4.4~5.9,最适度是5.1;SL3阶段是5.0~6.5,最适度是5.5.胖大海的丰富度变化受表层土壤湿度和pH值2个因素的影响,其关系能够用Logit Gauss模型来表征.表层土壤湿度和pH值受森林类型影响,胖大海高优势度林分或者高稳定性林分具有更适合胖大海幼树幼苗天然更新的环境.

Effect of humidity and pH of surface soil on S. lychnophora Sapling regeneration

Sterculia lychnophora Hance has deteriorated in southeast Vietnam in recent decades due to over-exploitation. Sapling re-generation plays a vital role on sustainability and development of forest. To investigate limiting factors on S. lychnophora reforesta-tion, 150 plots were established in Dongnai Natural and Culture reserve of Vietnam. Data on humidity and pH of surface soil and ap-pearance of saplings were collected from plots and followed by statistical analysis. Sapling were divided into three grades by height, namely SL1 (<50 cm), SL2 (51-100 cm), SL3 (>100 cm and diameter at breast height <6 cm). Results showed that humidity ( W%) and pH of surface soil were related to abundancy at each phase, namely in SL1 humidity ranged from 57.7% to 78.8%, with 68.2% being the optimum humidity. For SL2 and SL3, humidity ranges were 64.8%-80.7% and 65%-80%, respectively, with 72.8%and 73.3% being the optimum humidity for SL2 and SL3. pH ranges for SL1-SL3 were 3.5 -5.7(4.6, figure in parenthesis denoted the optimum pH), 4.4 - 5.9 (5.1), 5.0 to 6.5 (5.5), respectively. Furthermore, relationships between appearance fre-quency and humidity, and pH could be presented in Logit Gauss model, respectively. To summarize, surface soil humidity and pH are important ecological factors when forest type changes. Forest having dominant species can be optimal nursary for its sapling re-generation.