Effects of selection cutting on the forest structure and species diversity of evergreen broa-leaved forest in northern Fujian, southern China

The short-term effects of selection cutting of different intensities on the forest structure and species diversity of evergreen broad-leaved forest in northern Fujian Province were investigated and analyzed. The results showed that selection cutting of low and medium intensities caused little variation in the forest structure. After cutting, the dominant species retained their leading status in the community. However, the community structure changed significantly following selection cutting of high and extra-high intensities; the status of the dominant species of the community declined dramatically. Some tree species began to disappear from the sampling plots. Except for extra-high intensity cutting, the diversity of tree species did not change significantly for the other three cutting intensities. However, the evenness of the stands was very different among the four kinds of cutting plots. For low and medium intensity selection cutting, the evenness declined slightly. For extra-high intensity selection cutting, the evenness increased to some extent, which might be due to a more even distribution of tree species after cutting. Cutting operations resulted in some adverse reactions to development of arborous species diversity of evergreen broad-leaved forest, particularly serious damage to the forest canopy. But the rational selection cuttings, which may benefit the restoration and maintenance of species diversity over a long period and may come about from the variations in environmental factors such as sunlight, temperature and humidity.     

Impact of time lags on diurnal estimates of canopy transpiration and canopy conductance from sap-flow measurements of Populus cathayana in the Qinghai–Tibetan Plateau

Recently, canopy transpiration(Ec) has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to the capacitive exchange between the transpiration stream and stem water storage. Significant errors will be introduced in canopy conductance(gc) and canopy transpiration estimation if the time lag is neglected. In this study, a cross-correlation analysis was used to quantify the time lag, and the sap flowbased transpiration was measured to parameterize Jarvistype models of gcand thus to simulate Ecof Populus cathayana using the Penman–Monteith equation. The results indicate that solar radiation(Rs) and vapor pressure deficit(VPD) are not fully coincident with sap flow and have an obvious lag effect; the sap flow lags behind Rsand precedes VPD, and there is a 1-h time shift between Ecand sap flow in the 30-min interval data set. A parameterized Jarvis-type gc model is suitable to predict P. cathayana transpiration and explains more than 80% of the variation observed in gc, and the relative error was less than 25%, which shows a preferable simulation effect. The root mean square error(RMSEs)between the predicted and measured Ecwere 1.91 9 10-3(with the time lag) and 3.12 9 10-3cm h-1(without the time lag). More importantly, Ecsimulation precision that incorporates time lag is improved by 6% compared to the results without the time lag, with the mean relative error(MRE) of only 8.32% and the mean absolute error(MAE) of1.48 9 10-3cm h-1.     

Division of ecological species groups and functional groups based on interspecific association — a case study of the tree layer in the tropical lowland rainforest of Jianfenling in Hainan Island, China

Twenty-three sample plots dominated by Vatica mangachapoi at various elevations in the tropical lowland rainforest in the Jianfengling National Nature Reserve of Hainan Island were established. The interspecific association among the 32 dominant species was analyzed and the division of ecological species groups and functional groups are discussed. The results showed that these dominant populations had an overall positive interspecific association. The species pairs with significant, positive association accounted for only about 10% of the total 496 species pairs. Most of the other species pairs showed weak association or non-association, i.e., the dominant populations investigated had relatively independent distributions. The 32 dominant species were divided into four ecological species groups and ten functional groups according to their interspecific association coefficients, based on a cluster analysis of the species. Recognition characteristics of the ten functional groups are proposed. __________ Translated from Scientia Silvae Sinicae, 2007, 43(4): 9–16 [译自: 林业科学]     

Effect of forest structure and health on the relative surface temperature captured by airborne thermal imagery – Case study in Norway Spruce-dominated stands in Southern Finland

The effect of forest structure and health on the relative surface temperature captured by airborne thermal imagery was investigated in Norway Spruce-dominated stands in Southern Finland. Airborne thermal imagery, airborne scanning light detection and ranging (LiDAR) data and 92 field-measured sample plots were acquired at the area of interest. The surface temperature correlated most negatively with the logarithm of stem volume, Lorey’s height and the logarithm of basal area at a resolution of 254?m² (9?m radius). LiDAR-derived metrics: the standard deviations of the canopy heights, canopy height (upper percentiles and maximum height) and canopy cover percentage were most strongly negatively correlated with the surface temperature. Although forest structure has an effect on the detected surface temperature, higher temperatures were detected in severely defoliated canopies and the difference was statistically significant. We also found that the surface temperature differences between the segmented canopy and the entire plot were greater in the defoliated plots, indicating that thermal images may also provide some additional information for classifying forests health status. Based on our results, the effects of forest structure on the surface temperature captured by airborne thermal imagery should be taken into account when developing forest health mapping applications using thermal imagery.     

Species composition and influencing factors of understory woody species in Robinia pseudoacacia plantations on the Loess PlateauOA

Black locust(Robinia pseudoacacia L.)plantations have contributed significantly to soil and water conservation and ecological reconstruction on China’s Loess Plateau.Understanding the impact of stand and environment on species composition of understory woody plants will improve the stability of existing black locust plantations.Ten stands were selected in second-generation black locust plantations in tableland and gully areas of the Loess Plateau.The number of understory tree species in the tabl...     

Impact of time lags on diurnal estimates of canopy transpiration and canopy conductance from sap-flow measurements of <Emphasis Type="Italic">Populus cathayana</Emphasis> in the Qinghai–Tibetan Plateau

Recently, canopy transpiration (E_c) has been often estimated by xylem sap-flow measurements. However, there is a significant time lag between sap flow measured at the base of the stem and canopy transpiration due to the capacitive exchange between the transpiration stream and stem water storage. Significant errors will be introduced in canopy conductance (g_c) and canopy transpiration estimation if the time lag is neglected. In this study, a cross-correlation analysis was used to quantify the time lag, and the sap flow-based transpiration was measured to parameterize Jarvis-type models of g_c and thus to simulate E_c of Populus cathayana using the Penman–Monteith equation. The results indicate that solar radiation (R_s) and vapor pressure deficit (VPD) are not fully coincident with sap flow and have an obvious lag effect; the sap flow lags behind R_s and precedes VPD, and there is a 1-h time shift between E_c and sap flow in the 30-min interval data set. A parameterized Jarvis-type g_c model is suitable to predict P. cathayana transpiration and explains more than 80% of the variation observed in g_c, and the relative error was less than 25%, which shows a preferable simulation effect. The root mean square error (RMSEs) between the predicted and measured E_c were 1.91 × 10^?3 (with the time lag) and 3.12 × 10^?3 cm h^?1 (without the time lag). More importantly, E_c simulation precision that incorporates time lag is improved by 6% compared to the results without the time lag, with the mean relative error (MRE) of only 8.32% and the mean absolute error (MAE) of 1.48 × 10^?3 cm h^?1.     

The dissemination of relevant information on wildlife utilization and its connection with the illegal trade in wildlifeOA

We analyzed the generation and dissemination of relevant information on wildlife utilization based on the African bush elephant(Loxodonta africana Blumenbach.),the tiger(Panthera tigris L.) and the totoaba, a species of marine fish,(Totoaba macdonaldi Gilbert) as examples,whose populations are more threatened by the illegal wildlife trade. We compared the illegal trade in wildlife with related information in order to find possible associations,searched for relevant information on major internati...