Short-term gas exchange responses of Betula utilis to simulated global warming in a timberline ecotone, eastern Tibetan Plateau, China

doi:10.3773/j.issn.1005-264x.2010.03.003

Abstract

Abstract:

Aims Betula utilis is an important plant in the timberline ecotone of subalpine regions, Western Sichuan China. Our objective is to determine how this species changes its photosynthetic parameters under warming conditions.

Methods We studied the responses of gas exchange to simulated global warming using the open-top chamber (OTC) method. During the 2007 growing season, microclimate data between the OTC and the control (CK) were taken at 15-min intervals with an automatic recording system. In mid-August, the gas exchange of B. utilis seedlings in the OTC and the CK was measured with the LI-6400 Portable Photosynthesis System and a 6-cm² leaf chamber. Comparisons between the OTCs and the control plots were analyzed by the Wilcoxon’s signed ranks test.

Important findings Warming significantly increased instantaneous leaf net photosynthetic rate (P_n), conductance (G_s) and transpiration (T_r) by 17.4%, 21.4% and 33.9%, respectively, and reduced leaf N concentration by 12.4%. Warming also enhanced the maximum net photosynthetic rate (P_n_max) (+19.6%), dark respiration rate (R_d) (+14.3%) and apparent quantum yield (AQY) (+7.9%), but did not influence the light compensation point (LCP) or the light saturation point (LSP) of B. utilis seedlings. Moreover, warming markedly increased the maximum rate of RuBP carboxylation (V_cmax) and rate of photosynthetic election transport (J), but there were no clear differences between treatments for triose phosphate use (TPU) and compensation CO₂ (CCP). Our results indicated that in situ experimental warming had positive effects on the gas exchange of B. utilis seedlings. These responses could be helpful for the timberline species to adapt to future global warming.

Key words: Betula utilis, ecotone in timberline, open-top chamber, P_n -C_i curve, P_n -PAR curve

XU Zhen-Feng, HU Ting-Xing, ZHANG Li, ZHANG Yuan-Bin, XIAN Jun-Ren, WANG Kai-Yun. Short-term gas exchange responses of Betula utilis to simulated global warming in a timberline ecotone, eastern Tibetan Plateau, China[J]. Chin J Plant Ecol, 2010, 34(3): 263-270.

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https://www.plant-ecology.com/EN/Y2010/V34/I3/263

Figures/Tables 5

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层次 Layer (cm)	有机质 Organic matter (g·kg^-1)	全N Total N (g·kg^-1)	全P Total P (g·kg^-1)	全K Total K (g·kg^-1)	速效N Soluble N (g·kg^-1)	速效P Soluble P (g·kg^-1)	速效K Soluble K (g·kg^-1)
0-15	180.2 ± 5.5	4.5 ± 0.8	5.5 ± 0.8	13.7 ± 0.8	154.8 ± 9.1	18.0 ± 4.4	231.7 ± 6.7
15-30	99.5 ± 3.7	4.0 ± 0.8	4.1 ± 0.5	23.0 ± 1.7	64.2 ± 7.4	13.8 ± 3.1	175.0 ± 10.5
30-47	12.6 ± 1.8	0.6 ± 0.4	0.4 ± 0.1	18.4 ± 0.9	28.7 ± 4.2	7.5 ± 2.6	118.3 ± 5.3

层次 Layer (cm)	有机质 Organic matter (g·kg^-1)	全N Total N (g·kg^-1)	全P Total P (g·kg^-1)	全K Total K (g·kg^-1)	速效N Soluble N (g·kg^-1)	速效P Soluble P (g·kg^-1)	速效K Soluble K (g·kg^-1)
0-15	180.2 ± 5.5	4.5 ± 0.8	5.5 ± 0.8	13.7 ± 0.8	154.8 ± 9.1	18.0 ± 4.4	231.7 ± 6.7
15-30	99.5 ± 3.7	4.0 ± 0.8	4.1 ± 0.5	23.0 ± 1.7	64.2 ± 7.4	13.8 ± 3.1	175.0 ± 10.5
30-47	12.6 ± 1.8	0.6 ± 0.4	0.4 ± 0.1	18.4 ± 0.9	28.7 ± 4.2	7.5 ± 2.6	118.3 ± 5.3

月份 Month	处理 Treatment	气温T_air (℃)			土壤温度T_soil (℃)
月份 Month	处理 Treatment	Mean	Max	Min	土壤温度T_soil (℃)
5	OTC	7.4 ± 1.9	11.3 ± 4.0	3.7 ± 2.3	4.7 ± 1.0
5	CK	5.0 ± 1.7	7.9 ± 3.9	2.2 ± 1.4	4.4 ± 0.7
6	OTC	12.9 ± 1.7	19.6 ± 2.9	7.9 ± 2.8	8.4 ± 1.2
6	CK	10.3 ± 1.7	16.0 ± 2.8	5.6 ± 3.1	7.8 ± 1.1
7	OTC	13.8 ± 1.7	21.0 ± 2.7	9.6 ± 2.1	10.2 ± 1.0
7	CK	10.6 ± 1.6	16.9 ± 2.8	6.5 ± 2.6	9.8 ± 0.8
8	OTC	11.7 ± 2.0	19.7 ± 3.3	7.5 ± 3.0	9.9 ± 1.1
8	CK	8.2 ± 2.4	14.2 ± 2.5	4.3 ± 3.3	9.5 ± 0.9

月份 Month	处理 Treatment	气温T_air (℃)			土壤温度T_soil (℃)
月份 Month	处理 Treatment	Mean	Max	Min	土壤温度T_soil (℃)
5	OTC	7.4 ± 1.9	11.3 ± 4.0	3.7 ± 2.3	4.7 ± 1.0
5	CK	5.0 ± 1.7	7.9 ± 3.9	2.2 ± 1.4	4.4 ± 0.7
6	OTC	12.9 ± 1.7	19.6 ± 2.9	7.9 ± 2.8	8.4 ± 1.2
6	CK	10.3 ± 1.7	16.0 ± 2.8	5.6 ± 3.1	7.8 ± 1.1
7	OTC	13.8 ± 1.7	21.0 ± 2.7	9.6 ± 2.1	10.2 ± 1.0
7	CK	10.6 ± 1.6	16.9 ± 2.8	6.5 ± 2.6	9.8 ± 0.8
8	OTC	11.7 ± 2.0	19.7 ± 3.3	7.5 ± 3.0	9.9 ± 1.1
8	CK	8.2 ± 2.4	14.2 ± 2.5	4.3 ± 3.3	9.5 ± 0.9

处理 Treatment	叶氮浓度 LN (%)	净光合速率 P_n (μmol·m^-2·s^-1)	蒸腾速率 T_r (mmol·m^-2·s^-1)	气孔导度 G_s (mmol·m^-2·s^-1)	水分利用率 WUE (mmol·mol^-1)
OTC	0.99 (0.09)^a	11.94 (0.73)^a	4.15 (0.42)^a	545.55 (14.87)^a	2.88 (0.35)^a
CK	1.13 (0.07)^b	10.17 (0.55)^b	3.42 (0.54)^b	407.46 (17.15)^b	2.97 (0.41)^a