## 5 Conclusions  
From the perspective of urban expansion, NPP was used to discover the spatiotemporal pattern variation of urban carbon storage and its driving mechanisms. To achieve this purpose, the current study replaced complex physiological parameters in the ecological models with a comparison between the effects of weather variations and LULC changes on NPP. An evaluation based on this method can not only identify the entire trend of weather variations and natural ecosystems, but it also estimates the NPP response to different effect patterns caused by urbanisation. Future work should further explore  
\begin{table}
\begin{tabular}{l c c c c c c c c} \hline \hline  & \multicolumn{4}{c}{**2001–2003**} & \multicolumn{4}{c}{**2003–2006**} \\ \hline  & \multicolumn{2}{c}{**NPP-Temperature**} & \multicolumn{2}{c}{**NPP-Precipitation**} & \multicolumn{2}{c}{**NPP-Temperature**} & \multicolumn{2}{c}{**NPP-Precipitation**} \\ \cline{2-9}  & **Average** & **SD (*)** & **Average** & **SD** & **Average** & **SD** & **Average** & **SD** \\ \hline Central Area & \(0.13\) & \(0.55\) & \(-0.19\) & \(0.55\) & \(0.74\) & \(0.33\) & \(-0.63\) & \(0.36\) \\ Suburb & \(0.19\) & \(0.45\) & \(-0.27\) & \(0.46\) & \(0.84\) & \(0.25\) & \(-0.85\) & \(0.14\) \\ Exurb & \(0.18\) & \(0.68\) & \(-0.21\) & \(0.67\) & \(0.34\) & \(0.47\) & \(-0.63\) & \(0.38\) \\ \hline \hline \end{tabular} Note: SD (*) is the standard deviation.  
\end{table}
Table 4: Correlations between NPP and temperature and precipitation.  
Figure 7: Annual average temperature and total precipitation in Guangzhou from 2000 to 2007.  
how conversion of LULC can determine intensity and magnitude of the effects. The next step will be further assessment in relation to LULC change with ability for GHG reduction in urban areas, based on the study conclusions:  
During the fast urban expansion and adjustment period, the NPP mean value reached 331.5 g\(\cdot\)C\(\cdot\)m\({}^{-2}\)\(\cdot\)a\({}^{-1}\) in 2001, 366.3 g\(\cdot\)C\(\cdot\)m\({}^{-2}\)\(\cdot\)a\({}^{-1}\) in 2003 and changed to 273.2 g\(\cdot\)C\(\cdot\)m\({}^{-2}\)\(\cdot\)a\({}^{-1}\) in 2006. The spatiotemporal pattern of NPP variations was distinct in the central area, suburb and exurb, which was caused by both effects with different intensities. Combined with the NPP variation response, the four intensity categories were divided into three driving patterns, including the interactive influences of both effects (effect intensity \(<\)25% or \(>\)85%), effects dominated by weather variations (effect intensity of 25%-40%) and effects dominated by LULC changes (effect intensity of 40%-85%). The previous two patterns mainly led to a slight and common fluctuation in the central urban and the suburb; while the third pattern was the main driving force causing the fast reduction of NPP in some areas of the suburb and exurb. Importantly, this study revealed that the conversion from grassland, shrubland and forest cover to urban areas and croplands corresponds to a change from high-NPP coverage to low-NPP coverage. So, the conversion case strengthened human disturbance and ultimately led to fast degradation of carbon stocks ability. The total decreased NPP was about \(167\times 10^{6}\) g\(\cdot\)C during this fast urbanization period.  
This work was supported by the National Natural Science Foundation of China (No. 41101152, No. 40901090), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, the talents introduced into Universities Foundation of Guangdong Province of China,the China Scholarship Council (CSC) funding 2013, and the universities disciplinary and special construction funds of Guangdong Province Foundation (C10092), the Scientific Research Foundation of Graduate School of South China Normal University.  
The authors declare no conflict of interest.