红树植物秋茄根系固氮微生物群落的稳定性和复杂性及其关键影响因子研究

doi:10.11978/2025123

Abstract

Abstract:

The root-associated diazotrophs of the mangrove species Kandelia obovata exhibit remarkable species richness, which are integral to nitrogen cycling within mangrove ecosystems. However, their ecological adaptation mechanisms remain inadequately understood. In this study, we collected 75 samples each of root endosphere, rhizosphere, and bulk soil from a mangrove nature reserve in Leizhou, South China. Based on high-throughput sequencing and molecular ecological approaches, we investigated the composition, diversity, complexity, and stability of diazotrophs across these three compartments of K. obovata, as well as their main influencing factors. The results showed that Alphaproteobacteria, Deltaproteobacteria, and Gammaproteobacteria were the dominant species in the mangrove root-associated diazotrophs, with Alphaproteobacteria having the highest abundance in the root endosphere (54.9%), significantly higher than that in the rhizosphere (37.5%) and bulk soil (29.1%). α-diversity analysis revealed that the Shannon index was the highest in the bulk soil and the lowest in the rhizosphere (P<0.05). NMDS (Non-metric Multidimensional Scaling) and ANOSIM (Analysis of Similarities) analyses (r=0.659, P<0.001) confirmed significant differences in community structure among the three compartments. Notably, the diazotrophs in the rhizosphere of K. obovata exhibit the lowest α-diversity but highest community stability. Co-occurrence network analysis indicated that diazotrophs network in the rhizosphere was the most robust, the bulk soil network had the highest connectivity, while the endorhizosphere was the most complex yet the most fragile. Spearman correlation analysis demonstrated region-specific effects of environmental factors on complexity and stability: salinity and $ \mathrm{NH}_{4}^{+}-\mathrm{N} $ jointly drove complexity in the bulk soil and rhizosphere, while $ \mathrm{NO}_{3}^{-}-\mathrm{N} $ mainly influenced stability in bulk soil. In the rhizosphere, complexity was significantly negatively correlated with TS and $ \mathrm{NO}_{2}^{-}-\mathrm{N} $, while stability showed significant positive correlation with salinity. This study enhances the understanding of the mechanisms governing the maintenance of complexity and stability of diazotrophs within mangrove ecosystems, holding significant implications for the restoration and conservation of mangrove ecosystems in similar coastal wetlands.

Key words: diazotrophic communities, root-associated zones, mangrove ecosystem, co-occurrence network, complexity, stability

CLC Number:

X172

QI Feng, DENG Xiaojie, GUAN Yongpeng, ZHOU Shengyao, HE Qing, RAJAPAKSHALAGE Thashikala Nethmini, LI Nan, JIANG Gonglingxia, CHEN Qingxiang, LEI Xinyue, HOU Qinghua, HUANG Laizhen, LI Xiaolei, WEI Qiaoyan. Study on the stability and complexity of diazotrophic communities and key driving factors in the root-associated zones of the mangrove plant Kandelia obovata[J].Journal of Tropical Oceanography, 2026, 45(3): 153-163.

Figures/Tables 7

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References 46

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环境因子	Shannon指数
环境因子	非根际(BS)	根(R)	根际(RS)
氧化还原电位ORP/mV	0.68^***	0.1	-0.35
pH	0.08	0.29	-0.49^*
温度/℃	-0.63^***	-0.88^***	0.78^***
盐度/‰	0.35	-0.49^*	0.29
总硫TS/%	-0.14	0.29	0.1
硫酸盐 $\mathrm{SO}_{4}^{2-}$/(mg·g^-1)	-0.02	0.1	0.2
总磷TP/(mg·g^-1)	-0.04	-0.69^***	0.59^**
磷酸盐 $\mathrm{PO}_{4}^{3-}$/(mg·g^-1)	0.04	0.69^***	-0.59^**
总氮TN/%	0.8^***	0.15	-0.4^*
总碳 TC/%	0.35	0.1	0.05
总有机碳 TOC/%	-0.08	-0.29	0.49^*
亚硝态氮 $\mathrm{NO}_{2}^{-}-\mathrm{N}$/(μmol·L^-1)	-0.67^***	-0.39	0.69^***
硝态氮 $\mathrm{NO}_{3}^{-}-\mathrm{N}$/(μmol·L^-1)	-0.45^*	-0.69^***	0.59^**
氨氮 $ \mathrm{NH}_{4}^{+}-\mathrm{N}$/(μmol·L^-1)	0.18	-0.69^***	0.49^*

参数	非根际(BS)	根内(R)	根际(RS)
节点数(nodes number)	104	90	98
边数(edges number)	1444	1471	764
平均度(average degree)	27.769	32.689	15.592
平均路径长度(average path length)	2.187	1.974	2.368
网络直径(graph diameter)	5	6	5
网络密度(graph density)	0.27	0.367	0.161
平均聚类系数(average clustering coefficient)	0.702	0.721	0.59
模块化(modularity)	0.281	0.16	0.478
正相关比例(positive correlation)	0.962	0.967	0.67

环境因子	BS		R		RS
环境因子	复杂性	稳定性	复杂性	稳定性	复杂性	稳定性
ORP/mV	0.3	0.56	0.35	0.36	-0.6^**	0.31
pH	-0.59^**	0.2	0.29	0.5	0.59^**	-0.6
温度/℃	0.29	-0.9^*	0.1	-0.8	0	0.3
盐度/‰	0.98^***	-0.4	0.49^*	-0.3	-0.78^***	1^***
TS/%	-0.1	0.3	-0.69^***	-0.1	-0.1	-0.1
$ \mathrm{SO}_{4}^{2-}$/(mg·g^-1)	0.29	0	-0.39	-0.2	-0.29	0.3
TP/(mg·g^-1)	0.88^***	-0.7	0.29	-0.6	-0.59^**	0.9^*
PO₄^3-/(mg·g^-1)	-0.88^***	0.7	-0.29	0.6	0.59^**	-0.9^*
TN/%	0.7^***	0.21	0.65^***	0.41	-0.65^***	0.72
TC/%	0.55^**	0.21	-0.15	-0.05	-0.65^***	0.56
TOC/%	0.59^**	-0.2	-0.29	-0.5	-0.59^**	0.6
$ \mathrm{NO}_{2}^{-}-\mathrm{N}$/(μmol·L^-1)	-0.2	0.1	-0.88^***	-0.7	-0.2	-0.2
$ \mathrm{NO}_{3}^{-}-\mathrm{N}$/(μmol·L^-1)	0.39	-1^***	0.29	-0.6	0.1	0.4
$ \mathrm{NH}_{4}^{+}-\mathrm{N}$/(μmol·L^-1)	0.88^***	-0.3	0.29	-0.5	-0.88^***	0.9^*

Study on the stability and complexity of diazotrophic communities and key driving factors in the root-associated zones of the mangrove plant Kandelia obovata

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