图2. 氮(N)和磷(P)添加对森林树木生长及生产力影响的案例研究全球分布图。图中的横线表示基于纬度划分的不同气候区的森林分布界限, 包括热带森林(23.5° S-23.5° N)、北方森林(46°-66° N)和温带森林(介于热带和北方森林的纬度之间)。
N表示该研究中只有N添加; P表示该研究中只有P添加; N, P表示该研究中有单独的N和单独的P添加; N, P, NP表明该研究中包含单独的N、单独的P和N、P共同添加。该图使用ArcGIS 10.2.2绘制。

Fig. 2. Global distribution of case studies investigating the effects of nitrogen (N) and/or phosphorus (P) addition on tree growth and productivity in forest ecosystems. The horizontal lines in the figure indicate the distribution boundaries of forests in different climatic regions based on latitude, including tropical forest (23.5° S-23.5° N), boreal forest (46°-66° N), and temperate forest (between the tropical and boreal latitudes).
N represents only N addition in the case study; P represents only P addition in the case study; N, P represent only N and only P addition in the case study; N, P, NP represents only N, only P and N plus P addition in the case study. This map was drawn using the software ArcGIS 10.2.2.