随年龄自然稀疏

natural thinning thinning people afflicted by a natural disaster age AGE flower thinning row thinning thinning limits universal thinning preliminary thinning released thinning tension thinning children by age group population composition by age population by age group character classification by age natural regeneration by seeds sex ratio by age groups point location by natural landmarks Bone age studies by X-ray Poisoning by natural blood or blood product