Effect of Long-term Experimental Warming on the Nutritional Quality of Alpine Meadows in the Northern Tibet

doi:10.5814/j.issn.1674-764x.2020.05.009

Abstract

Abstract:

The nutritional quality of grasslands is closely related to recruitment of young and population dynamics of livestock and wild herbivores. However, the response of nutritional quality to climate warming has not been fully understood in the alpine meadow on the Tibetan Plateau, especially in the Northern Tibet. Here, we investigated the effect of experimental warming ( beginning in 2008) on nutritional quality in three alpine meadows (site A: 4313 m, B: 4513 m and C: 4693 m) in the Northern Tibet. Crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), crude ash (Ash), ether extract (EE) and water-soluble carbohydrate (WSC) were examined in 2018-2019. Experimental warming only increased the content of CP by 27.25%, ADF by 89.93% and NDF by 41.20%, but it decreased the content of Ash by 57.76% in 2019 at site B. The contents of CP and WSC both increased with soil moisture (SM). The content of CP decreased with vapor pressure deficit (VPD). The combined effect of SM and VPD was greater than air temperature (T_a) in controlling the variations of the CP content, ADF content and nutritional quality. Compared to T_a, VPD explained more of the variation in NDF and Ash content. All of these findings suggest that warming effects on nutritional quality may vary with site and year, and water availability may have a stronger effect on the nutritional quality than temperature in the alpine meadow of the Northern Tibet.

Key words: acid detergent fiber, crude ash, crude protein, ether extract, neutral detergent fiber, water-soluble carbohydrate

SUN Wei, LI Shaowei, ZHANG Yangjian, FU Gang. Effect of Long-term Experimental Warming on the Nutritional Quality of Alpine Meadows in the Northern Tibet[J]. Journal of Resources and Ecology, 2020, 11(5): 516-524.

Figures/Tables 9

Table 1 Annual mean temperature (AT) and precipitation (AP), and growing season (June-September) temperature (GST) and precipitation (GSP) in 1963-2019, 2018 and 2019 in the Damxung County, Lhasa City, Tibet, China

Year	AT (℃)	AP (mm)	GST (℃)	GSP (mm)
1963-2019	1.96±0.80	476.36±96.69	10.02±0.62	400.45±86.83
2018	2.67	667.00	10.82	589.10
2019	3.08	426.20	11.14	372.40

Table 2 Repeated analysis of variance for the main and interactive effects of experimental warming (W) and measurement year on soil temperature (Ts), soil moisture (SM), air temperature (Ta) and vapor pressure deficit (VPD)

Site Model		T_s		SM		T_a		VPD
Site Model		F	P	F	P	F	P	F	P
A	W	25.01	0.007	1.22	0.331	0.95	0.385	0.14	0.731
	Y	12.11	0.025	1.60	0.275	0.09	0.774	5.29	0.083
	W×Y	0.02	0.891	0.11	0.753	0.02	0.897	0.79	0.425
B	W	215.52	<0.001	3.41	0.139	4.33	0.106	17.07	0.014
	Y	5.00	0.089	6.62	0.062	0.42	0.554	81.01	0.001
	W×Y	1.93	0.237	0.00	0.952	0.02	0.883	2.90	0.164
C	W	43.26	0.003	1.78	0.253	10.09	0.034	149.08	<0.001
	Y	0.19	0.683	14.93	0.018	0.15	0.718	379.35	<0.001
	W×Y	5.49	0.079	1.21	0.334	1.10	0.355	25.49	0.007

Fig. 1 Comparisons of (a) soil temperature (Ts), (b) soil moisture (SM), (c) air temperature (Ta) and (d) vapor pressure deficit (VPD) between non-warming and warming treatments at sites A, B and C in 2018 and 2019 Note: * indicates P<0.05.

Table 3 Repeated analysis of variance for the main and interactive effects of experimental warming (W) and measurement year on the content of crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), crude ash (Ash), ether extract (EE) and water-soluble carbohydrate (WSC)

Site Model		CP		ADF		NDF		Ash		EE		WSC
Site Model		F	P	F	P	F	P	F	P	F	P	F	P
A	W	2.40	0.197	6.71	0.061	0.15	0.716	0.25	0.645	0.01	0.919	0.11	0.761
	Y	32.37	0.005	5.86	0.073	8.59	0.043	3.86	0.121	2.75	0.172	1.36	0.308
	W×Y	0.85	0.410	2.29	0.205	0.05	0.841	0.03	0.870	2.12	0.220	0.21	0.670
B	W	79.22	0.001	4.99	0.089	23.00	0.009	24.52	0.008	5.73	0.075	0.85	0.409
	Y	24.56	0.008	1.61	0.273	15.18	0.018	0.65	0.467	0.44	0.545	10.49	0.032
	W×Y	0.00	0.975	0.08	0.793	2.38	0.198	2.78	0.171	1.07	0.360	9.33	0.038
C	W	0.21	0.668	3.98	0.117	0.77	0.429	1.14	0.346	0.06	0.813	0.79	0.423
	Y	77.38	0.001	17.92	0.013	41.27	0.003	1.00	0.373	0.53	0.506	1.38	0.306
	W×Y	4.21	0.109	0.01	0.926	1.33	0.313	2.96	0.161	0.64	0.470	0.18	0.690

Fig. 2 Comparisons of (a) crude protein (CP), (b) acid detergent fiber (ADF), (c) neutral detergent fiber (NDF), (d) crude ash (Ash), (e) ether extract (EE) and (f) water-soluble carbohydrate (WSC) between non-warming and warming treatments at sites A, B and C in 2018 and 2019 Note: * indicates P<0.05.

Fig. 3 Nonmetric multidimensional scaling (NMDS) analysis of the nutritional quality Note: Legend abbreviations: ANW18: site A of non-warming treatment in 2018; AW18: site A of warming treatment in 2018; BNW18: site B of non- warming treatment in 2018; BW18: site B of warming treatment in 2018; CNW18: site C of non-warming treatment in 2018; CW18: site C of warming treatment in 2018; ANW19: site A of non-warming treatment in 2019; AW19: site A of warming treatment in 2019; BNW19: site B of non-warming treatment in 2019; BW19: site B of warming treatment in 2019; CNW19: site C of non-warming treatment in 2019; CW19: site C of warming treatment in 2019.

Table 4 The permutational multivariate analysis of variance of experimental warming (W), measurement year (Y) and measurement site (S) on nutritional quality

Model	F	P
W	4.59	0.028
Y	21.71	0.001
S	1.52	0.231
W×Y	1.75	0.173
W×S	0.76	0.542
Y×S	1.51	0.214
W×Y×S	1.29	0.287

Fig. 4 Univariate regression analysis between the contents of (a) crude protein (CP) and soil moisture (SM), (b) CP and vapor pressure deficit (VPD), and (c) water-soluble carbohydrate (WSC) and SM

Fig. 5 Variation partitioning analysis (VPA), showing the shared and exclusive effects of soil moisture (SM), air temperature (Ta) and vapor pressure deficit (VPD) on (a) crude protein (CP), (b) acid detergent fiber (ADF), (c) neutral detergent fiber (NDF), (d) crude ash (Ash), and (e) the nutritional quality Note: The fractions of unexplained variation are not illustrated.

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