In Chinese forestry policy,
四旁 specifically means the four 'sides' suitable for planting trees:
村旁 (next to villages),
宅旁 (next to homes),
路旁 (next to roads), and
水旁 (next to water). The slogan
四旁植树 (sipang zhishu) was a major mass campaign in 20th-century rural greening.