Table 6. Changes associative words by period.

Classification	1	2	3	4	5	6	7	8	9	10
The 1st period (2001∼2005)	Word A	species	vegetation	diversity	forest	structure	diversity	species	community	forest	forest
	Word B	diversity	structure	community	vegetation	species	species	correlation	structure	community	structure
	Strength	40	16	15	13	13	11	11	11	11	10
The 2nd period (2006∼2010)	Word A	species	urban	management	naturalization	forest	endemic	plant	species	eco-trail	plant
	Word B	diversity	tourism	plan	plant	resources	plant	naturalization	correlation	interpretation	rare
	Strength	10	7	6	5	4	4	4	3	3	3
The 3rd period (2011∼2015)	Word A	climate	species	vegetation	forest	national	forest	species	diversity	forest	North Korea
	Word B	habitat	diversity	structure	ecosystem	park	kindergarten	diversity	index	kindergarten	South Korea
	Strength	36	20	17	10	8	7	7	7	6	6
The 4th period (2016∼2020)	Word A	climate	forest	naturalization	Vascular	species	importance	plant	forest	rare	species
	Word B	habitat	healing	plant	plant	diversity	value	naturalization	management	plant	distribution
	Strength	47	25	24	21	13	12	11	9	8	8
Total	Word A	climate	species	naturalization	vegetation	forest	forest	importance	rare	endemic	plant
	Word B	habitat	diversity	plant	structure	vegetation	healing	value	plant	plant	naturalization
	Strength	85	81	46	42	37	29	27	25	25	23