Study on the effect of submerged plants on the stability of karst carbon sink

doi:10.13745/j.esf.sf.2024.2.9

Abstract

Abstract:

Karst carbon sinks are an important means of achieving carbon neutrality, and their stability is a key scientific issue that needs to be addressed. Approximately 45% of annual photosynthesis on Earth occurs in aquatic environments, yet how submerged plants in karst areas affect the stability of karst carbon sinks remains unknown. This study focused on submerged plants in three karst rivers. We employed quadrat sampling, pH-drift technology, and elemental stoichiometry to qualitatively and quantitatively examine the effects of submerged plants on the stability of karst carbon sinks. Our results showed that there were 8, 5, and 7 species of submerged plants in the ZDR, CTR, and HXR, respectively. The Shannon-Wiener diversity index and Simpson dominance index ranked as ZDR>HXR>CTR. In the three karst rivers, Vallisneria natans, Ottelia acuminata, Potamogeton wrightii, and Hydrilla verticillata were the dominant species, all of which had the ability to utilize $\mathrm{HCO}_{3}^{-}$. The annual carbon sequestration rates of submerged plants in the ZDR, HXR, and CTR were 8.56×10³ g·m^-2·a^-1, 4.83×10³ g·m^-2·a^-1, and 3.88×10³ g·m^-2·a^-1, respectively, with an average of 5.76×10³ g·m^-2·a^-1, which are 37.65 and 40.56 times higher than those of grasslands and man-made forests, respectively. The higher the diversity of submerged plants in rivers, the higher the carbon sequestration. Overall, submerged plants play a crucial carbon pump role in karst aquatic ecosystems, thereby enhancing the stability of karst carbon sink.

Key words: karst carbon sink, carbon sequestration by submerged plants, plant diversity, dominant species of plants, river types

CLC Number:

X173

SUN Caiyun, ZHENG Bingqing, LI Jun, FU Hongming, SUN Rongqing, LIU Honghao, LIAO Zuying, JIANG Hongsheng, WU Zhenbin, XIA Shibin, WANG Pei. Study on the effect of submerged plants on the stability of karst carbon sink[J]. Earth Science Frontiers, 2024, 31(5): 430-439.

Figures/Tables 8

Fig.1 Map of sampling sites

Table 1 Physical and chemical indicators of water bodies in three rivers

采样点	温度/℃	pH	电导率/ (μS·cm^-1)	Ca²⁺浓度/ (mg·L^-1)	$HCO 3 -$ 浓度/ (mmol·L^-1)	水流速度/ (m·s^-1)	水深/m	透明度/m
ZDR	19.8~21.5	7.3~8.4	376~389	76~80	3.8~4.1	0.04~0.78	0.3~1.8	0.3~1.8
CTR	26.0~26.3	7.4~8.1	233~244	40~44	2.1~2.2	0.12~0.38	0.5~2.3	0.5~1.6
HXR	19.7~22.8	7.2~8.3	321~330	67~70	3.1~3.4	0.04~0.80	0.5~2.2	0.5~1.6

Table 1 Physical and chemical indicators of water bodies in three rivers

采样点	温度/℃	pH	电导率/ (μS·cm^-1)	Ca²⁺浓度/ (mg·L^-1)	$HCO 3 -$ 浓度/ (mmol·L^-1)	水流速度/ (m·s^-1)	水深/m	透明度/m
ZDR	19.8~21.5	7.3~8.4	376~389	76~80	3.8~4.1	0.04~0.78	0.3~1.8	0.3~1.8
CTR	26.0~26.3	7.4~8.1	233~244	40~44	2.1~2.2	0.12~0.38	0.5~2.3	0.5~1.6
HXR	19.7~22.8	7.2~8.3	321~330	67~70	3.1~3.4	0.04~0.80	0.5~2.2	0.5~1.6

Table 2 Plant types in different rivers

科名	种名	拉丁名	河流
科名	种名	拉丁名	ZDR	CTR	HXR
水鳖科 Hydrocharitaceae	苦草	Vallisneria natans (Lour.)	√	√	√
	黑藻	Hydrilla verticillata (L. f.)	√	√	√
	海菜花	Ottelia acuminata	√	—	√
眼子菜科 Potamogetonaceae	竹叶眼子菜	Potamogeton wrightii Morong	√	√	√
	微齿眼子菜	Potamogeton maackianus	√	—	—
	眼子菜	Potamogeton distinctus	√	—	—
	菹草	Potamogeton crispus L.	—	√	—
小二仙草科 Haloragaceae	狐尾藻	Myriophyllum verticillatum L.	√	√	√
轮藻科 Characeae	轮藻	Chara braunii Gmel.	√	—	√
金鱼藻科 Ceratophyllaceae	金鱼藻	Ceratophyllum demersumL.	—	—	√

Fig.2 Dominance, mean biomass of submerged plants in three rivers

Fig.3 Species diversity indices in the three rivers H, D, and J represent three species diversity indices: Shannon-Wiener diversity index, Simpson dominance index, and Pielou evenness index.

Fig.4 pH-drift experiments

Fig.5 Carbon content of four dominant species of submerged plants

Table 3 Average biomass and carbon content of the dominant submerged plant species

植物种类	平均生物量/(kg·m^-2)			TC含量/%
植物种类	ZDR	CTR	HXR	TC含量/%
V.natans	7.61	1.20	4.82	36
H.verticillata	2.20	5.32	1.86	34
P.wrightii	4.75	4.13	0.85	39
O.acuminata	8.75	0.00	5.80	37

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