The emergy indices for the evaluation of system's sustainable development ability were studied. Results indicated that the emergy indices are simplified and merged, and a new emergy index for sustainable development (EISD) is deduced. Employing EISD, two cases are conducted. The first one is to compare three different dike-pond agro-ecological engineering modes, which are: melon-melon-cabbage-four domestic fishes (mode Ⅰ), melon-melon-cabbage-pig-four domestic fishes (mode Ⅱ) and melon-melon-cabbage-pig-four domestic fishes combined with Siniperca chuatsi B. (mode Ⅲ). The result is that the EISD of mode Ⅰis 0.53. Mode Ⅱ's EISD is 5.26 times of mode Ⅰ, and mode Ⅲ's EISD is 6.83 times of mode Ⅰ. The second one is to evaluate the development of Zhongshan City, Pearl Delta, during 1996 to 2000. The result indicated that the EISD of Zhongshan had appreciably declined from 1996 to 1998, and quickly improved from 1998 to 2000, partly because of its environment protection and product construction. Both of the two cases studies showed that EISD can assessment the sustainable development ability more roundly, with the consideration of environmental impact and social2economic effect at the same time.

The emergy indices for the evaluation of system's sustainable development ability were studied. Results indicated that the emergy indices are simplified and merged, and a new emergy index for sustainable development (EISD) is deduced. Employing EISD, two cases are conducted. The first one is to compare three different dike-pond-agro-ecological engineering modes, which are: melon-melon-cabbage-four domestic fishes (mode Ⅰ), melon-melon-cabbage-pig-four domestic fishes (mode Ⅱ) and melon-melon-cabbage-pig-four domestic fishes combined with Siniperca chuatsi B. (mode Ⅲ). The result is that the EISD of mode Ⅰis 0.53. Mode Ⅱ's EISD is 5.26 times of mode Ⅰ, and mode Ⅲ's EISD is 6.83 times of mode Ⅰ. The second one is to evaluate the development of Zhongshan City, Pearl Delta, during 1996 to 2000. The result indicated that the EISD of Zhongshan had appreciably declined from 1996 to 1998, and quickly improved from 1998 to 2000, partly because of its environment protection and product construction. Both of the two cases studies showed that EISD can assessment the sustainable development ability more roundly, with the consideration of environmental impact and social-economic effect at the same time.

The environmental effect of degraded ecosystem's vegetation restoration in low subtropical China was studied. Results indicated that the vegetation recovery on degraded lands significantly ameliorates surrounding environment, increases species diversity, improves soil structure, raises soil fertility, enhances productivity, and promotes regional agricultural production and social economic development dramatically. Through the combining engineering and biological measures, the restoration of degraded ecosystem in low subtropical area is possible and economical. The restoration experience in Xiaoliang, Wuhua and other sites are valuable for other degraded subtropical area was introduced.

Species-abundance (SA) pattern is one of the most fundamental aspects of biological community structure, providing important information regarding species richness, species-area relation and succession. To better describe the SA distribution (SAD) in a community, based on the widely used lognormal (LN) distribution model with exp (−x2) roll-off on Preston's octave scale, this study proposed two additional models, logCauchy (LC) and log-sech (LS), respectively with roll-offs of simple x−2 and e−x. The estimation of the theoretical total number of species in the whole community, S*, including very rare species not yet collected in sample, was derived from the left-truncation of each distribution. We fitted these three models by Levenberg-Marquardt nonlinear regression and measured the model fit to the data using coefficient of determination of regression, parameters' t-test and distribution's Kolmogorov-Smirnov (KS) test. Examining the SA data from six forest communities (five in lower subtropics and one in tropics), we found that: (1) on a log scale, all three models that are bell-shaped and left-truncated statistically adequately fitted the observed SADs, and the LC and LS did better than the LN; (2) from each model and for each community the S* values estimated by the integral and summation methods were almost equal, allowing us to estimate S* using a simple integral formula and to estimate its asymptotic confidence internals by regression of a transformed model containing it; (3) following the order of LC, LS, and LN, the fitted distributions became lower in the peak, less concave in the side, and shorter in the tail, and overall the LC tended to overestimate, the LN tended to underestimate, while the LS was intermediate but slightly tended to underestimate, the observed SADs (particularly the number of common species in the right tail); (4) the six communities had some similar structural properties such as following similar distribution models, having a common modal octave and a similar proportion of common species. We suggested that what follows the LN distribution should follow (or better follow) the LC and LS, and that the LC, LS and LN distributions represent a "sequential distribution set" in which one can find a best fit to the observed SAD.