Seed Germination and Storage of Woody Species in the Lower Subtropical Forest

The dimension, water content and germination of the seeds from 90 woody species in the lower subtropical forest were analyzed in this study. Out of 90 species, germination analysis was performed in 45 species (in which there were enough germinating individuals), and the effect of storage of seed and fruit on germination of seed was studied in 41 species (in which there were enough seeds and germinating individuals). Most of the species began to germinate within 60 d. Hypogeal species had longer dormancy than epigeal species. Dormancy of fleshy seeds and seeds in pulpy fruit was also longer than that of dry seeds. There were no significant differences in length of dormancy (LD, days from sowing to germination) between fleshy seeds ripening in summer and those ripening in winter and spring, and between big seeds and small seeds. Seeds in pulpy fruit or fleshy seeds had more germination than the dry seeds ( P <0.05), however, percentage germination was not significantly correlated with water content of fresh seeds. Water loss in the seeds could obviously affect percentage germination, especially during the early three days when the seeds were laid open in air in the laboratory. When water content of the seeds decreased to about 20% (fresh weight basis), percentage germination became very low, this happened when the seeds were laid open in air for 10-14 d. Percentage germination decreased with the length of storing in refrigerator ((4±1) ℃), but it was not markedly affected for one month's storage, with a decrease by 8.3% in comparison with the fresh seeds, and it was greatly affected by storing for more than three months, with values decreasing by 37%, 63%, and 81% for three months', six months' and 12 months' storage respectively. Difference in percentage germination as well as in LD was not significant for most lots after different storing periods between big seeds and small seeds, between fruit storage and seed storage, and between seeds in pulpy fruits or fleshy seeds and dry seeds.

浅谈公路交通噪声及降噪措施

在分析公路交通噪声影响和来源的基础上,提出通过设置声屏障、建造减噪路面和种埴林带等方式来降低噪声,并强调要根据公路工程的实际情况来选择最佳降噪方案。

Enrichment planting in a logged-over tropical mixed deciduous forest of Laos

Enrichment planting is commonly used for increasing the density of desired tree species in secondary forests often characterized by a prevalence of low commercial species. The objectives of the study were to identify the optimal enrichment planting method vis-à-vis gap and line planting, and to evaluate the performance of two dipterocarps （Vatica cinerea and Dipterocarpus alatus） and three legumes （Afzelia xylocarpa, Pterocarpus macrocarpus, Dalbergia cochinchinensis） planted in logged-over mixed deciduous forest of Laos. The enrichment planting trial was arranged in a randomized complete block design with seven replica-tions. Survival, height and diameter were measured seven years after planting and subjected to analysis of variance. Survival rate of planted seedlings did not vary between enrichment planting （p 0.05）. However, diameter and height growth was favored more in gaps than in planting lines. This was related to rapid canopy closure in both gaps and lines, albeit more remarkable in planting lines. Significant inter-species varia-tion was detected for survival rate, height and diameter. The shade-tolerant dipterocarps had better survival and growth than the light-demanding leguminous species （p 0.0001）. The size class distribution of individuals was irregular, accentuating uneven light condition in the understory. Given the difficulty to maintain constant line width and even light condi-tion, the cost of annual clean operation and the rigid geometric patterns of planting lines, the use of logged-over gaps for enrichment planting is recommended. Dipterocarpus alatus and V. cinerea are recommended for enrichment planting in mixed deciduous forests. A. xylocarpa, D. cochi-chinensis and P. macrocarpus can be planted in wider gaps, lines and open sites as plantation of mixed species or under canopy of young swidden forests.

Impact of anthropogenic disturbance on species diversity and vegetation structure of a lowland tropical rainforest of eastern Himalaya, India

Impact of anthropogenic disturbance on species diversity and vegetation structure of a lowland tropical rainforest was studied in the foothills of Eastern Himalaya, India. Tree species richness,density, basal area and the diversity indices were found significantly(P<0.05) decreased with the increasing level of disturbances whereas, shrub density, basal area and herb density significantly increased with increasing disturbance level. In case of shrubs, Simpson's dominance index significantly(P<0.007) increased along the disturbance gradient,whereas Pielou's evenness index significantly(P<0.005) decreased with an increasing level of disturbance. Shannon-Weiner diversity index for herbs significantly(P<0.016) increased with increasing disturbance whereas, Simpson's dominance index was significantly(P<0.013) declined along the disturbance gradient. Results revealed that10-50 cm dbh classes constituted the highest stem density, and highest basal area was recorded in the >100 cm dbh class in all three sites. Density of the matured trees decreased with increasing DBH whereas, tree basal area tended to increase with increasing DBH in all three sites. Tree species richness was highest in the lower DBH classes.62.07% of the total tree species regenerated in the largely undisturbed site followed by 50% in the mildly disturbed and 26.32% in the highly disturbed site.The overall regeneration condition was found to be good in the largely undisturbed site. Mildly disturbed site exhibited fair regeneration and so was in the highly disturbed site. Discernable variations in species composition, diversity, regeneration and tree population structure revealed the impact of anthropogenic disturbances on rainforest vegetation dynamics. Higher degree of disturbance was furtherly found not only affecting species diversity but also promoting the growth of invasive weed species.Dominance of Hydnocarpus kurzii and Crypteronia paniculata in the highly disturbed site also indicated that these less-valued timber species may benefit from the vegetation mosaic produced by the disturbance; so differences in abundance of these species may be useful for bio-indication. Furthermore,present study suggests the need of adequate biodiversity conservation measures and adaptation of sustainable forest management approaches in disturbed areas of lowland tropical rainforest in the foothills of eastern Himalaya, India.