Impacts of Rapid Urbanization on Carbon Fixing and Oxygen Production of Vegetation in the Pearl River Delta
Impacts of Rapid Urbanization on Carbon Fixing and Oxygen Production of Vegetation in the Pearl River Delta
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发表时间：
2006
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通讯作者：
Yan‐jing Chen;D. Guan;Peart
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作者：
Yan‐jing Chen;D. Guan;Peart
珠江三角洲面积4.17 ×10~ 4km ~2，人口4078.06×10~ 4km ~ 2珠江三角洲是我国典型的城市化地区，有28个城市，434个城镇，城镇间平均距离不足10 km。近20年来，珠江三角洲是我国和世界上城市化最快的地区。城市化是我国城市化的重要组成部分，也是我国城市化进程中的一个重要环节。土地利用变化的影响因素，由于植被破坏等原因对生态环境产生影响。然而，很少有研究关注土地利用变化对生态环境的影响，通过估算生物量和净初级生产力（NPP）的损失来研究植被的快速城市化。NPP的损失对碳固定和氧气生产有影响。森林的树木生物量是由树干体积估计的。以广州流溪河森林为例，估算了林下植被的生物量.森林的NPP与森林的生物量、生长状况和林龄有关，因此，森林的NPP可用NPP与生物量的关系式估算.灌木林、疏林地、果园和草地的生物量和NPP可用其区域平均值估算.根据经济产量和相对经济系数计算作物的生物量，用生物量乘以多种作物指数计算所有作物的NPP，用生物量计算碳含量，系数为0.45。珠江三角洲土地利用随着城市化的快速发展而发生变化，耕地面积减少，居民点和工业用地面积增加，林地面积减少，耕地面积减少，居民点和工业用地面积增加。1990 ~ 2000年，耕地、疏林灌丛和草地面积分别减少304578 hm 2、77093 hm 2和604 hm 2;由于珠江三角洲城市扩展占用了大量的生态用地，10年内耕地、疏林灌丛和草地的“流失”面积达28.78%，珠江三角洲生态系统碳氧平衡能力下降8.68%，固定CO_2量减少4000137 t/a，产生O_2量减少2909200 t/a，碳氧平衡能力下降10.00%，碳氧平衡能力下降10.00%，固定CO_2量减少1000137 t/a，产生O_2量减少2909200 t/a东莞市是城市化最快的城市之一，10年间，东莞市居民点、工业用地和交通基础设施面积分别增加了1.12倍和1.4倍，植被面积减少了25.35%，其中耕地、果园、森林、疏林地和灌丛，东莞市的生物量和NPP分别减少了1213961 t和471419 t/a，各植被类型的生物量和NPP均呈下降趋势，耕地、果园、林地、林地、草地、草地的生物量和NPP分别减少了21370 hm 2、13214 hm 2、6979 hm 2、473 hm 2和41 hm 2，疏林地、灌丛、草地分别减少143 820、313 172、747 213、9 346 410、249 815 t/a、121 569、94 573、5 150 312 t/a，植被的固碳和产氧能力降低了26.76%结果表明，植被固碳产氧能力降低2/3以广州市为例，研究了城市土地利用变化对城市土地利用的影响对生态环境的影响不容忽视。
The Pearl River Delta which has an area of 4.17 ×10~4 km~2 and a population of 4078.06×10~4 is a typical urbanizing area in China.There are 28 cites and 434 towns and the mean distance between the towns is less than 10 km.The Pearl River Delta has been the most rapidly urbanizing area in China and the world for the last 20 years.Urbanization is an important factor for land use change, which has an impact on the eco-environment due to vegetation destruction etc.However,very few studies focus on the impact of land use change on the eco-environment by estimating the loss of biomass and net primary production(NPP) of vegetation due to rapid urbanization.The loss of NPP has implications for carbon fixing and oxygen production.The tree biomass of forest was estimated from tree trunk volume.The biomass of undergrowth in forests was estimated based upon a case study of the Liuxihe forests of Guangzhou.The NPP of forest is related to biomass,condition and age of forest.Therefore,the NPP of forest was estimated by formulae relating NPP and biomass.The biomass and NPP of shrubland,sparse woodland,orchard and pasture were estimated by their mean values for the region. The biomass of a given crop was calculated by economic production and a relative economic coefficient.The NPP of all crops was estimated from biomass times multiple crop indices.Carbon content is calculated from biomass using a factor of 0.45.Land use has been changed with rapid urbanization in the Pearl River Delta.The area of cultivated land has decreased and the area of residential and industrial land has increased.Woodland,pasture and unused land has also decreased, and area of transport infrastructure,orchard and water bodies increased.The area of cultivated land,sparse woodland shrubland,and pasture decreased by 304 578 hm~2,77 093 hm~2 and 604 hm~2 respectively from 1990 to 2000,because large amounts of ecological land were used for urban expansion in the Pearl River Delta.The 'lost' areas of cultivated land,sparse woodland shrubland,and pasture in 10 the year period were equal to 28.78%,30.15% and 38.57% respectively of those in 1990.The regional vegetation area was decreased by 8.00%.The ability for a balance of carbon and oxygen for the ecosystem of the Pearl River Delta was decreased by 8.68%.The amount of CO_2 fixed and O_2 production decreased by 4 000 137 t/a and 2 909 200t/a respectively.Dongguan was one of the most rapidly urbanizing cities.Its area of residential industrial land and transport infrastructure increased by 1.12 times and 1.4 times respectively in 10 years.Vegetation area in Dongguan was decreased by 25.35%,of which cultivated land,orchard,forest, sparse woodland and shrubland,and pasture decreased by 21370 hm~2,13214 hm~2,6979 hm~2,473 hm~2 and 41 hm~2 respectively.The biomass and NPP of Dongguan decreased by 1213961 t and 471419 t/a,respectively.The biomass and NPP of various vegetation types declined.The biomass and NPP of cultivated land,orchard,forest,sparse woodland and shrubland,and pasture decreased by 143 820,313 172,747 213, 9 346,410 and 249 815 t/a,121 569,94 573,5 150,312 t/a,respectively.Carbon fixing and oxygen production of vegetation were decreased by 26.76%.It was shown that the ability of vegetation to fix carbon and produce oxygen would be reduced by 2/3 if the suburban area had been changed to an urban area according to a case study in urban Guangzhou.The study indicates that the impacts of land use change on the eco-environment cannot be neglected or ignored.