Table 1 Key parameters of allometric equations for potassium (K) density (g m^–2) in plant communities of the Tibetan Plateau.

Communities	Organs	No.	R²	P	Slope	95% CI	Intercept	95% CI
Communities	(x vs. y)	No.	R²	P	Slope	95% CI	Intercept	95% CI
Forest	D_leaf vs. D_branch^¶	169	0.46	0 < 0.001	1.19	(1.06, 1.33)	–5.42	(–8.8, –2.04)	***^,‡
	D_leaf vs. D_trunk	169	0.53	0 < 0.001	0.54	(0.49, 0.60)	1.92	(0.5, 3.35)	***
	D_leaf vs. D_root	169	0.48	0 < 0.001	0.71	(0.64, 0.80)	0.29	(–1.69, 2.26)	***
	D_branch vs. D_trunk	169	0.39	0 < 0.001	0.45	(0.40, 0.51)	4.38	(2.91, 5.86)	***
	D_branch vs. D_root	169	0.25	0 < 0.001	0.60	(0.53, 0.68)	3.54	(1.31, 5.77)	***
	D_trunk vs. D_root	169	0.34	0 < 0.001	1.32	(1.17, 1.50)	–2.26	(–4.74, 0.23)	***
Shrubland	D_leaf vs. D_branch	22	0.14	0.08	0.56	(0.37, 0.85)	2.52	(–2.53, 7.58)	**
	D_leaf vs. D_root	22	0.85	0 < 0.001	0.70	(0.59, 0.85)	0.36	(–2.11, 2.83)	***
	D_branch vs. D_root	22	0.05	0.33	1.26	(0.81, 1.96)	–2.82	(–10.75, 5.12)	ns
Grassland	D_leaf vs. D_root	466	0.63	0 < 0.001	0.67	(0.63, 0.71)	0.77	(0.48, 1.05)	***
Desert	D_leaf vs. D_root	23	0.02	0.54	1.51	(0.97, 2.33)	–1.38	(–3.56, 0.8)	ns
Total	D_leaf vs. D_branch	191	0.44	0 < 0.001	1.16	(1.04, 1.29)	–4.97	(–8.07, –1.88)	**
	D_leaf vs. D_trunk	169	0.53	0 < 0.001	0.54	(0.49, 0.60)	1.92	(0.5, 3.35)	***
	D_leaf vs. D_root	680	0.62	0 < 0.001	0.70	(0.67, 0.73)	0.62	(0.15, 1.09)	***
	D_branch vs. D_trunk	169	0.39	0 < 0.001	0.45	(0.40, 0.51)	4.38	(2.91, 5.86)	***
	D_branch vs. D_root	191	0.24	0 < 0.001	0.62	(0.54, 0.70)	3.35	(1.28, 5.43)	***
	D_trunk vs. D_root	169	0.34	0 < 0.001	1.32	(1.17, 1.50)	–2.26	(–4.74, 0.23)	***

R² coefficient of determination, CI confidence interval.
^‡ ***, ** denote significant differences between the slope of the equation and 1 at P = 0.001 and 0.01; ns, no significant difference at P = 0.05.
^¶D_leaf: leaf potassium density (g m^–2); D_branch: branch potassium density (g m^–2); D_trunk: trunk potassium density (g m^–2); D_root: root potassium density (g m^–2).
The K density of different plant organs was transformed into a log–log scale. The likelihood test was used to examine differences among different organs, and the data were analyzed using a standardized major axis and calculated using SMATR Version 2.0 (http://www.bio.mq.edu.au/ecology/SMATR/).

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