广西沿海红海榄造林的宜林临界线

2004年8月—2005年8月,在广西英罗湾滩涂上建造8个高程梯度(320~390cm,相邻梯级间高度差10cm)的试验平台,研究全日潮海区潮汐淹水胁迫对红海榄幼苗生长和生理指标的影响.结果表明:小高程(320~330cm)生境对红海榄幼苗茎高生长有微弱促进作用,340cm以上高程组幼苗茎高随滩涂高程增加而增大.中等高程(350~370cm)有利于幼苗茎节数的增长.滩涂高程越低,幼苗叶数、叶面积和叶保存率越低.小高程组幼苗叶片叶绿素a受损明显,叶绿素b则受损相对较轻;叶绿素a/b值随滩涂高程降低而减少.长时间淹水诱导使根系中SOD活性上升,叶片中则表现为中等高程组酶活性较低.叶片和根系中POD活性均随高程降低而增加.淹水胁迫使红海榄幼苗各器官及全株的生物量降低;随着淹水程度加大,新生器官生物量分配比例由叶向茎转移.随着高程降低,幼苗存活率从88.9%降至40.0%,但370cm以上高程组存活率均在80%以上.建议将当地平均海面线作为广西沿海红海榄胚轴造林的宜林临界线.

Critical tidal level for forestation with hypocotyls of Rhizophora stylosa Griff along Guangxi coast of China

From August 2004 to August 2005, three replicated experimental platforms were constructed in a section of tidal flat in Yingluo Bay of Guangxi to study the growth and physiological responses of Rhizophora stylosa Griff seedlings to the waterlogging stress of tide in diurnal tide zone. A total of eight tidal flat elevation (TFE) treatments, i.e., 320 cm, 330 cm, 340 cm, 350 cm, 360 cm, 370 cm, 380 cm and 390 cm above Yellow Sea Datum (YSD), were created on each platform. The results showed that lower TFEs (320-330 cm YSD) slightly increased the stem height of 1-year old seedlings, while higher TFFs (>340 cm YSD) increased the seedlings growth significantly. Moderate TFEs (350-370 cm YSD) favored the development of knots. Leaf number, leaf conservation rate, and leaf area per seedling all decreased dramatically with decreasing TFE. Lower TFEs had a larger damage to Chl a, but Chl b was less affected. The Chl a/b ratio decreased with decreasing TFE. Prolonged waterlogging induced a higher SOD activity in root, while moderate TFE inhibited the SOD activity in leaf. The POD activity in root and leaf increased with decreasing TFE. Waterlogging stress decreased the biomass of individual organs and whole seedling. With increasing waterlogging, the biomass partitioning in 1-year old seedlings increased from leaf to stem. The survival rate decreased sharply from 88.9% to 40.0% as TFE decreased, while more than 80% of the seedlings could survive at the TFE being 370 cm YSD and above. It was proposed that the local mean sea level could be adopted as the critical tidal level for the forestation with hypocotyls of R. stylosa along the Guangxi coast.