Vertical measurements of microclimatic elements of canopy gap in tropical seasonal rain forest were conducted in fog cool and dry hot season in Xishuangbanna. Making use of these data,the daytime characteristics of temporal spatial distribution and variation of trunk surface temperature,air temperature,water vapor pressure and relative humidity in canopy gap were discussed.

In primary evergreen broad-leaved forest, the gap density was 15 per hm 2, and 56% of the gaps had an area of no more than 40m 2. The largest gap had an area of 256m 2. The canopy gap accounted for 11.1% and expended gap occupied 19 8% of land area in the forest.

3) Gap density was about 20 per hectare. The mean size of canopy gap was (69.7±45.71) m~2, and the mean size of expanded gap was (152.7±79.43) m~2. The canopy gaps and expanded gaps covered 13.9% and 30.6% of the forest area respectively.

The average area of expand gap (EG) and canopy gap (CG) were 469.42 m~2 and 181.90 m~2 respectively, the area percentage of both in the forest landscape were 28.23% and 10.49% respectively, and annual natural disturbance frequency of both were (0.672 1%) and 0.247 9% respectively.

The results showed that the area percentage of expanded gap (EG) and canopy gap (CG) in the forest landscape were 50.86% and 16.66% respectively. The natural disturbance frequency for EG and CG were 0.85%·a-1 and 0.28%·a-1 respectively, the return interval of canopy gaps was about 357a.

The results showed that the gap density was 18.5 per hm 2,and the area of canopy gap and extended gap accounted for 28.4% and 60% of total forest area,respectively.

According to our field survey data, areas of canopy gaps and expanded gaps in broadleaved Korean pine forests in Changbai Mountains accounted for 12.5% and 28.8% of total survey areas, among which gaps with canopy gap area of 20-100 m2 and expanded gap area of 80-240 m2 made up of 80.7% and 81.8% of the totals respectively.

According to our field survey data, areas of canopy gaps and expanded gaps in broadleaved Korean pine forests in Changbai Mountains accounted for 12.5% and 28.8% of total survey areas, among which gaps with canopy gap area of 20-100 m2 and expanded gap area of 80-240 m2 made up of 80.7% and 81.8% of the totals respectively.

Based on the observation on the radiation with different wavelengths in tropical seasonal rain forest canopy gap,interior of forest,and meteorological station in different seasons,the radiation characteristics of canopy gap were discussed.

Seeds under unfiltered light, which simulated the light conditions of seeds on the soil surface in a canopy gap, germinated at a constant temperature of 20°C.

Contrasted Responses of Two Understorey Species to Direct and Indirect Effects of a Canopy Gap

There were many indicator species for high understorey light levels and canopy gap centres, but none for medium or low light or closed canopy.

Four attributes were included in the PCA: final germination percentage in canopy gap, germination rate in the laboratory, and gap-and chilling-dependency indices (EGAP and STRAT, respectively).

Final percent germination was significantly enhanced under canopy gap conditions in 19 species, and significantly reduced in 11 species.

The spatial distribution of throughfall in Pinus tabulaeformis plantations in northern China demonstrated that: the amount of through-fall under a single tree increases as the distance from the increases. The maximum amount of throughfall is not always at the canopy gaps, this is because of the translocation effect of the canopy to precipitation. The amount of throughfall at a given point is positively proportional to the area that actually receives rain. Throughfall varies greatly in space, and...

The spatial distribution of throughfall in Pinus tabulaeformis plantations in northern China demonstrated that: the amount of through-fall under a single tree increases as the distance from the increases. The maximum amount of throughfall is not always at the canopy gaps, this is because of the translocation effect of the canopy to precipitation. The amount of throughfall at a given point is positively proportional to the area that actually receives rain. Throughfall varies greatly in space, and the range is from 63.8% to 125.3% of the precipitation. Spectral analysis methods were used for the analysis of the throughfall distribution series, and the results are. the spatial distribution pattern of throughfall is mainly determined by the spatial distribution pattern of the canopy structure, periodicity has been found in the series, and it is cau- used by the periodicity of the canopy structure, but it has no evident relation to the periodicity of the trees spatial pattern.

The ecological effects of canopy gap on tree species have received much attention in the study of modern forest ecology.However,because of difficulties in measuring light attenuation in canopy gap and complex structure of forest canopies.Therefore,fish-eye photography was used to determine the hemispherical canopy photographs, and a mathematical model was used to calcutate the shading effects of tree canopy around gap Through comparing the track of sun that was draw on the...

The ecological effects of canopy gap on tree species have received much attention in the study of modern forest ecology.However,because of difficulties in measuring light attenuation in canopy gap and complex structure of forest canopies.Therefore,fish-eye photography was used to determine the hemispherical canopy photographs, and a mathematical model was used to calcutate the shading effects of tree canopy around gap Through comparing the track of sun that was draw on the hemispherical canopy photograph.the light regimes in gap was determined.

The disturbance regime of small and middle scale gap in two stands of a subalpine old growth Picea Abies (spruce fir) forest around Bitahai Lake, north west corner of Yunnan Province, were examined. Canopy gaps and expanded gaps covered 19% and 41% of total land area. The mean area of gaps and expanded gaps were 44 m 2 and 139 m 2 respectively. The gaps were formed with a frequency of 0.005 to 0.007 per year, and the estimated mean gap return interval was 167 years....

The disturbance regime of small and middle scale gap in two stands of a subalpine old growth Picea Abies (spruce fir) forest around Bitahai Lake, north west corner of Yunnan Province, were examined. Canopy gaps and expanded gaps covered 19% and 41% of total land area. The mean area of gaps and expanded gaps were 44 m 2 and 139 m 2 respectively. The gaps were formed with a frequency of 0.005 to 0.007 per year, and the estimated mean gap return interval was 167 years. Most gaps (87%) had more than one gap maker (overall means: 2.9 gap makers per gap), and gap makers within a gap were often from mortality events in separated time. In all gap makers investigated snap were 60%, but uproot and died standing were 28% and 12% respectively.