Gao Qiong, Yu Mei
Department of Environmental Sciences and Institute for Tropical Ecosystem Studies, University of Puerto Rico, Rio Piedras, San Juan, PR, United States of America.
PLoS One. 2014 Nov 19;9(11):e113140. doi: 10.1371/journal.pone.0113140. eCollection 2014.
Despite the overall trend of worldwide deforestation over recent decades, reforestation has also been found and is expected in developing countries undergoing fast urbanization and agriculture abandonment. The consequences of reforestation on landscape patterns are seldom addressed in the literature, despite their importance in evaluating biodiversity and ecosystem functions. By analyzing long-term land cover changes in Puerto Rico, a rapidly reforested (6 to 42% during 1940-2000) and urbanized tropical island, we detected significantly different patterns of fragmentation and underlying mechanisms among forests, urban areas, and wetlands. Forest fragmentation is often associated with deforestation. However, we also found significant fragmentation during reforestation. Urban sprawl and suburb development have a dominant impact on forest fragmentation. Reforestation mostly occurs along forest edges, while significant deforestation occurs in forest interiors. The deforestation process has a much stronger impact on forest fragmentation than the reforestation process due to their different spatial configurations. In contrast, despite the strong interference of coastal urbanization, wetland aggregation has occurred due to the effective implementation of laws/regulations for wetland protection. The peak forest fragmentation shifted toward rural areas, indicating progressively more fragmentation in forest interiors. This shift is synchronous with the accelerated urban sprawl as indicated by the accelerated shift of the peak fragmentation index of urban cover toward rural areas, i.e., 1.37% yr-1 in 1977-1991 versus 2.17% yr-1 in 1991-2000. Based on the expected global urbanization and the regional forest transition from deforested to reforested, the fragmented forests and aggregated wetlands in this study highlight possible forest fragmentation processes during reforestation in an assessment of biodiversity and functions and suggest effective laws/regulations in land planning to reduce future fragmentation.
尽管近几十年来全球森林砍伐呈总体趋势，但在快速城市化和农业废弃的发展中国家也发现了重新造林现象，并且预计会继续出现。尽管重新造林对景观格局的影响在评估生物多样性和生态系统功能方面具有重要意义，但相关文献中很少涉及。通过分析波多黎各（一个迅速重新造林的热带岛屿，1940 - 2000年期间重新造林率为6%至42%）长期的土地覆盖变化，我们发现森林、城市地区和湿地之间的破碎化模式及潜在机制存在显著差异。森林破碎化通常与森林砍伐有关。然而，我们也发现在重新造林过程中也存在显著的破碎化现象。城市扩张和郊区发展对森林破碎化具有主导影响。重新造林大多发生在森林边缘，而大量森林砍伐则发生在森林内部。由于森林砍伐和重新造林过程的空间配置不同，森林砍伐过程对森林破碎化的影响比重新造林过程要强得多。相比之下，尽管沿海城市化干扰强烈，但由于湿地保护法律法规的有效实施，湿地出现了聚集现象。森林破碎化峰值向农村地区转移，表明森林内部的破碎化程度逐渐增加。这种转移与城市扩张加速同步，如城市覆盖破碎化指数峰值向农村地区的加速转移所示，即19照77 - 1991年为1.37%/年，而1991 - 2000年为2.17%/年。基于预期的全球城市化以及区域森林从砍伐森林到重新造林的转变，本研究中破碎化的森林和聚集的湿地突出了重新造林过程中在生物多样性和功能评估方面可能出现的森林破碎化过程，并建议在土地规划中制定有效的法律法规以减少未来的破碎化。
