Clonal Growth and Sexual Reproduction Characteristics and Influencing Factors of Schoenoplectus tabernaemontani in Yunnan Plateau Lakes

ZHAO Piao¹², LIU Zhenya¹², WANG Na¹², NIU Mengying³, AI Jing⁴, XIAO Derong⁵⁶, WANG Hang¹²*

¹Yunnan Key Laboratory of Plateau Wetland Conservation, Restoration and Ecological Services, Southwest Forestry University, Kunming 650224, China
²National Plateau Wetlands Research Center/College of Wetlands, Southwest Forestry University, Kunming 650224, China
³College of Life Sciences, Southwest Forestry University, Kunming 650224, China
⁴Sugarcane Research Institute of Yunnan Academy of Agricultural Sciences, Kaiyuan 661600, Yunnan, China
⁵College of Life and Environmental Sciences, Wenzhou University, Wenzhou 325035, Zhejiang, China
⁶National and Local Joint Engineering Research Center of Ecological Treatment Technology for Urban Water Pollution, Wenzhou University, Wenzhou 325035, Zhejiang, China

Abstract: The response of plant growth and reproduction to future climate change has attracted widespread attention. To understand the spatial distribution patterns of clonal growth and sexual reproduction parameters in emergent plants and the pathways through which environmental factors influence plant reproduction, this study utilized the three-dimensional topography of the Yunnan Plateau to investigate geographical variations in clonal growth and sexual reproduction of the common emergent plant Schoenoplectus tabernaemontani across six lakes, employing a space-for-time substitution approach. The results showed that: (1) Clonal growth parameters including density, plant height, and basal diameter, as well as reproductive parameters such as seed setting ratio, spike biomass, spike investment ratio, seed production, and number of active seeds differed significantly across geographic space (P < 0.05), whereas above-ground biomass showed no significant differences. (2) Parameters including density, plant height, seed setting ratio, spike biomass, and spike investment ratio exhibited significant zonal distribution patterns along latitude, longitude, and altitude gradients. Specifically, density increased with increasing latitude and altitude but decreased with increasing longitude; conversely, plant height, seed setting ratio, spike biomass, and spike investment ratio decreased with increasing latitude and altitude but increased gradually with increasing longitude. (3) Mean temperatures of warm and cold months, soil total nitrogen, and soil total phosphorus were key factors affecting clonal growth (density and height), with warm month mean temperature having the greatest influence. Mean annual precipitation and soil organic carbon were key factors affecting sexual reproduction, with mean annual precipitation having the greatest influence. The study further demonstrated that climatic factors (warm month mean temperature, cold month mean temperature, and mean annual precipitation) are the primary drivers of growth and reproduction in the littoral zone emergent plant S. tabernaemontani in Yunnan Plateau lakes.

Keywords: emergent plant; lakeside zone; reproductive strategy; climate change; plateau lakes

Introduction

Plant growth and reproduction are essential pathways for population maintenance and dispersal, and are highly sensitive to environmental changes that subsequently affect ecosystem structure and function (Sherry et al., 2007). The response of plant growth and reproduction to future climate change has garnered extensive attention (Roa-Fuentes et al., 2012; Wang et al., 2018b). Littoral zone plants in plateau lakes are particularly sensitive to climate change (Liu et al., 2017), making it crucial to investigate how these plants respond to environmental factors to scientifically assess potential impacts of future climate change on plateau lake ecosystems.

Topographic factors (latitude, longitude, altitude), climate (precipitation, temperature), and soil nutrients all influence plant growth and reproduction (Gao & Liu, 2018; Gong et al., 2019; Zhang et al., 2019). Altitude is a dominant factor affecting plant growth and reproduction (Körner, 2007), with plant phenology (Walker et al., 2014) and leaf functional traits (Jiang & Ma, 2015) closely related to elevation. As altitude increases, plant biomass increases (Li, 2015) while plant height decreases (Mao et al., 2018; Liu et al., 2016) and individual size becomes smaller (Méndez & Traveset, 2003), accompanied by increased reproductive investment (Fabbro & Körner, 2004). Beyond altitude, plant height shows a hump-shaped relationship with latitude, peaking at mid-latitudes (Liu et al., 2016), though some studies indicate plant height decreases with increasing latitude (Moles et al., 2009). Due to geographic variation, plant habitats differ substantially. Previous research shows that temperature increases can either promote (Day et al., 2008; Li et al., 2014), inhibit (De et al., 2008; Kreyling et al., 2008), or have no significant effect (Dukes et al., 2005; Bloor et al., 2010) on clonal growth, while clearly promoting sexual reproduction (Wang et al., 2018a; Xiao et al., 2019). Increased precipitation can cause stomatal closure and reduced photosynthetic rates, inhibiting clonal growth (Körner, 2007), though other studies suggest precipitation increases can promote clonal growth (Roa-Fuentes et al., 2012). Enhanced soil nutrients can promote individual plant growth (Nasto et al., 2019) and increase seed yield (Wang et al., 2021). Generally, plant growth and reproduction are influenced by climatic factors at large scales (Svenning & Sandel, 2013) and by altitude gradients at regional scales such as mountains (Tang & Fang, 2004). In low-altitude areas, soil nutrients more significantly affect plant growth and reproduction, whereas temperature becomes more important at high altitudes (Sang, 2009). Thus, studying plant growth and reproductive strategies in response to environmental change represents a hot topic in ecological research, though current findings remain uncertain.

Yunnan Province features extremely complex and diverse topography, with the Hengduan Mountains in the northwest and the Yunnan-Guizhou Plateau in the east, exhibiting a maximum vertical elevation difference of 6,663.6 m. The spatial variation in environmental factors such as topography, climate, and soil is pronounced, creating unique geological, vegetation, and three-dimensional climate characteristics (Yang & Li, 2010). As critical components of the ecological barrier in the Yunnan Plateau, lakes exhibit typical "mountain-littoral-basin" ecological features, playing irreplaceable roles in biodiversity conservation and endemism while being highly sensitive to environmental change (Xiao et al., 2019). Emergent plants are important components of littoral zones in Yunnan Plateau lakes, forming the foundation of plateau lake ecological structure and function. Schoenoplectus tabernaemontani is a common species distributed across six plateau lakes including Napahai, Luguhu, Lashihai, Dianchi, Qiluhu, and Yilonghu (Yang & Li, 2010), with clonal growth and sexual reproduction serving as important pathways for maintaining population spatial distribution and dispersal. Therefore, studying how S. tabernaemontani responds to environmental factors across different geographic spaces can effectively illustrate adaptation strategies of littoral zone emergent plants to future climate change.

This study utilized the three-dimensional topography and unique climate of Yunnan to select six different plateau lakes, using the common emergent plant S. tabernaemontani as a research focus. We examined differences in clonal growth parameters (density, height, basal diameter, above-ground biomass) and sexual reproduction parameters (seed setting ratio, spike biomass, spike investment ratio, seed yield per unit area, number of active seeds per unit area) across different regions, and analyzed correlations between environmental factors (geographic location, climate, soil, and water) and plant growth and reproduction indicators. The study aimed to address three scientific questions: (1) Do growth and reproduction characteristics of the plateau lake emergent plant S. tabernaemontani show geographic distribution differences? (2) Do these characteristics exhibit latitudinal, longitudinal, and altitudinal zonation patterns? (3) What impacts do environmental changes resulting from geographic spatial differences have on plant clonal growth and sexual reproduction, and what is the magnitude of these impacts? Answering these questions will lay a foundation for understanding the response mechanisms of plateau lakes to future climate change.

1.1 Study Area

This study selected six lakes as research sites: Napahai, Luguhu, Lashihai, Dianchi, Qiluhu, and Yilonghu. Napahai, Luguhu, and Lashihai are located in the northwestern Yunnan Plateau, representing hotspots for biodiversity and endemism conservation in this region, with Napahai and Lashihai designated as internationally important wetlands. Dianchi, Qiluhu, and Yilonghu are situated in the central Yunnan Plateau, serving as ecological barriers for sustainable socio-economic development of the central Yunnan urban agglomeration and representing key areas for aquatic ecological security and biodiversity conservation. The six lakes span substantial topographic differences, with geographic locations ranging from 99.66–102.77°E and 23.67–27.85°N, altitudes between 1,412–3,260 m, longitudinal and latitudinal spans of 3.11° and 4.18° respectively, and an elevation difference of 1,848 m. Due to differences in geographic location, the lakes exhibit distinct environmental conditions.

1.2 Sample Collection

During August–October 2020, we established 3–6 1 m × 1 m quadrats in typical S. tabernaemontani distribution areas in the littoral zones of Napahai, Luguhu, Lashihai, Dianchi, Qiluhu, and Yilonghu. Specifically, we established 6 quadrats in Napahai, 4 in Luguhu, 3 in Lashihai, 3 in Dianchi, 3 in Qiluhu, and 4 in Yilonghu, totaling 23 quadrats. In the field, we measured total plant number and spike number in each quadrat, and selected 10 mature spiked plants to measure plant height and basal diameter using a vernier caliper with 0.01 mm precision. Spiked plants were clipped and brought back to the laboratory for measurement of spike morphology, biomass, and seed activity parameters. Using the harvest method, we collected above-ground plants from 25 cm × 25 cm subplots within each quadrat for determination of above-ground biomass. GPS was used to record latitude, longitude, and altitude of each quadrat. Surface soil samples (0–10 cm) were collected from each quadrat using a depth peat corer (Eijkelkamp, Netherlands), sealed in ziplock bags, and brought back to the laboratory for physicochemical analysis. Water samples were also collected in 500 mL plastic bottles for laboratory analysis of relevant physicochemical indicators.

1.3.1 Determination of Above-Ground Biomass and Sexual Reproduction Indicators

Using the oven-drying method, harvested plant samples were dried at 65 °C to constant weight for above-ground biomass determination. In the laboratory, spike length of 10 S. tabernaemontani plants from each quadrat was measured with a 0.1 cm precision ruler, and the number of spikelets and seeds per spike were recorded. Seed setting ratio was calculated as (number of fruiting plants/total number of plants) × 100%, and seed yield as (seeds/m² = average seeds per plant × fruiting plants per m²). After air-drying the bagged plants, spike biomass and plant biomass were measured separately to calculate the sexual reproduction biomass investment ratio: spike investment ratio = (spike biomass/plant biomass) × 100%. Finally, seeds from each quadrat were mixed thoroughly, and 200 seeds per quadrat were selected in three replicates. After physical removal of seed coats, seeds were longitudinally sectioned along the embryo side with a scalpel and stained in 1% tetrazolium phosphate buffer at (30 ± 1) °C for 24 h. Seed viability was observed under 10× magnification based on staining patterns. Seeds with main embryo structures stained bright red, or with only the radicle tip 2/3 unstained while other parts stained normally, were considered viable. Active seed number per unit area was calculated as: active seeds = seed yield × (stained seeds/total stained seeds × 100%).

1.3.2 Determination of Soil and Water Environmental Indicators

Soil organic carbon (SOC) content was determined using the acid washing method (Tang et al., 2018). Soil total nitrogen (STN) and total phosphorus (STP) were measured using H₂SO₄-H₂O₂ digestion. Water total nitrogen (WTN) and total phosphorus (WTP) were analyzed using a continuous flow analyzer (SEAL Analytical AA3, Germany). Climate parameters including mean annual temperature (MAT), maximum temperature of the warmest month (WMT), minimum temperature of the coldest month (CMT), and mean annual precipitation (MAP) were obtained from global grid data (precision: 0.16° × 0.16°; http://www.paleo.bris.ac.uk/) for each sampling site. Environmental parameters of soil and water at the littoral zones of each lake are presented in Table 1.

Table 1 Characteristics of geographic, climatic, soil, and water factors at each sampling site

Sampling site Geographic location Climate factor Soil factor Water factor Longitude (°E) Latitude (°N) Altitude (m) WMT (°C) Napahai 99.66 27.85 3260 11.6e Luguhu 100.78 27.71 2690 13.0d Lashihai 100.15 26.90 2440 15.3c Dianchi 102.77 24.84 1886 16.1b Qiluhu 102.97 24.09 1412 18.5a Yilonghu 102.52 23.67 1412 20.8b

Note: Different lowercase letters within the same column indicate significant differences (P < 0.05).

1.4 Data Processing

SPSS 19.0 software was used for one-way ANOVA on growth and reproduction indicators including density, height, basal diameter, above-ground biomass, seed setting ratio, spike biomass, spike investment ratio, seed yield per unit area, and active seed number per unit area across different regions, with significance level set at α = 0.05. Pearson correlation analysis was employed to examine relationships between S. tabernaemontani growth and reproduction indicators and climatic, soil, and hydrological factors. Stepwise regression analysis was further used to screen key factors affecting growth and reproduction characteristics. Path analysis of key influencing factors was conducted using the Agricolae package in R 4.01 software to investigate pathways and contribution rates of these factors to plant growth and reproduction.

Results

2.1 Spatial Differences in Growth and Reproduction

Except for above-ground biomass, S. tabernaemontani growth and reproduction parameters differed significantly across geographic space (P < 0.05). Density was highest in Napahai (853 ± 99 plants·m⁻²) and lowest in Dianchi (256 ± 43 plants·m⁻²), with significant differences among sampling sites (P < 0.05). Plant height was highest in Yilonghu (209 ± 28 cm) and lowest in Napahai (128 ± 5 cm), showing highly significant differences among sites (P < 0.001). Basal diameter was greatest in Yilonghu (13.3 ± 0.5 mm) and smallest in Lashihai (6.4 ± 1.4 mm), with highly significant differences (P < 0.001). Seed setting ratio peaked in Yilonghu (71% ± 6%) and was lowest in Napahai (35% ± 6%), with highly significant differences (P < 0.01). Spike biomass was highest in Yilonghu (457 ± 390 g·m⁻²) and lowest in Lashihai (46 ± 17 g·m⁻²), with significant differences (P < 0.05). Spike investment ratio was greatest in Yilonghu (13.9% ± 3.9%) and lowest in Napahai (2.2% ± 1.3%), with highly significant differences (P < 0.001). Seed yield per unit area was highest in Luguhu (18.0 × 10⁴ ± 6.6 × 10⁴ seeds·m⁻²) and lowest in Dianchi (3.8 × 10⁴ ± 0.6 × 10⁴ seeds·m⁻²), with significant differences (P < 0.05). Active seed number per unit area was highest in Luguhu (16.0 × 10⁴ ± 7.1 × 10⁴ seeds·m⁻²) and lowest in Dianchi (2.7 × 10⁴ ± 0.3 × 10⁴ seeds·m⁻²), showing highly significant differences (P < 0.01).

Table 2 Clonal growth and sexual reproduction parameters of Schoenoplectus tabernaemontani in different Yunnan Plateau lakes

Parameter Napahai Luguhu Lashihai Dianchi Qiluhu Yilonghu F value Density (plant·m⁻²) 853 ± 99a 748 ± 233ab 453 ± 24bc 256 ± 43c 581 ± 266b 540 ± 237b 6.101** Height (cm) 128 ± 5b 206 ± 15a 135 ± 19b 155 ± 32b 199 ± 32a 209 ± 28a 12.488*** Diameter (mm) 11.7 ± 1.0a 11.4 ± 1.4a 6.4 ± 1.4c 9.4 ± 1.6b 13.2 ± 0.9a 13.3 ± 0.5a 17.470*** Above-ground biomass (g·m⁻²) 2786 ± 972a 3069 ± 1195a 690 ± 175b 1976 ± 1204a 2769 ± 502a 2960 ± 1657a 2.786 Seed setting ratio (%) 35 ± 6c 54 ± 16b 48 ± 8bc 58 ± 6ab 56 ± 1ab 71 ± 6a 7.631** Spike biomass (g·m⁻²) 127 ± 64b 50 ± 22b 46 ± 17b 54 ± 22b 220 ± 94ab 457 ± 390a 3.544* Spike investment ratio (%) 2.2 ± 1.3c 4.0 ± 0.4c 6.7 ± 1.6bc 3.0 ± 1.4c 7.8 ± 2.4b 13.9 ± 3.9a 17.686*** Seed production (10⁴ seeds·m⁻²) 7.0 ± 1.7b 18.0 ± 6.6a 10.0 ± 0.9b 3.8 ± 0.6b 11.0 ± 8.7ab 13.0 ± 6.0ab 4.086* Active seed (10⁴ seeds·m⁻²) 1.8 ± 0.9b 16.0 ± 7.1a 9.0 ± 1.0ab 2.7 ± 0.3b 9.5 ± 7.3ab 11.0 ± 5.3a 6.012**

Note: Different lowercase letters in the same row indicate significant differences (P < 0.05). * indicates P < 0.05; ** indicates P < 0.01; *** indicates P < 0.001.

2.2 Spatial Distribution Patterns of Growth and Reproduction

S. tabernaemontani growth and reproduction indicators showed regular patterns along geographic gradients (Fig. 1). Plant density decreased with increasing longitude (Fig. 1A), while plant height, seed setting ratio, spike biomass, and spike investment ratio increased with longitude (Fig. 1D, G, J, M). Density increased with increasing latitude (Fig. 1B), whereas plant height, seed setting ratio, spike biomass, and spike investment ratio decreased with latitude (Fig. 1E, H, K, N). Similarly, density increased with altitude (Fig. 1C), while plant height, seed setting ratio, spike biomass, and spike investment ratio decreased with altitude (Fig. 1F, I, L, O).

Figure 1 Changes in growth and reproduction of Schoenoplectus tabernaemontani in lakes along geographic gradients on the Yunnan Plateau. * indicates P < 0.05; ** indicates P < 0.01; *** indicates P < 0.001.

2.3 Factors Influencing Growth and Reproduction and Their Pathways

Plant density showed extremely significant positive correlations with above-ground biomass and seed yield (P < 0.01). Plant height was significantly positively correlated with spike biomass, seed yield, and active seed number (P < 0.05) and extremely significantly positively correlated with spike investment ratio (P < 0.01). Basal diameter was significantly positively correlated with spike biomass (P < 0.05). Above-ground biomass was extremely significantly positively correlated with spike biomass and seed yield (P < 0.01) and significantly positively correlated with active seed number (P < 0.05) (Table 3).

Table 3 Pearson correlations between growth and reproduction indexes of Schoenoplectus tabernaemontani

Plant parameter Density Height Diameter Above-ground biomass Seed setting ratio Spike biomass Spike investment ratio Seed production Active seed Density 1 0.640** 0.507* 0.546** Height 1 0.518* 0.545** 0.526** 0.802** 0.435* 0.427* Diameter 1 0.637** 0.470* 0.571** 0.511* Above-ground biomass 1 0.602** 0.533** 0.563** 0.555** Seed setting ratio 1 0.571** 0.846** 0.447* 0.508* Spike biomass 1 0.846** 0.563** 0.555** Spike investment ratio 1 0.447* 0.508* Seed production 1 0.961** Active seed 1

Note: * indicates P < 0.05; ** indicates P < 0.01.

Growth and reproduction indicators showed significant correlations with regional climate and soil factors but not with lake water factors (Table 4). Density was extremely significantly negatively correlated with mean annual temperature, warm month mean temperature, cold month mean temperature, and mean annual precipitation (P < 0.01), extremely significantly positively correlated with soil total nitrogen (P < 0.01), and significantly positively correlated with soil total phosphorus (P < 0.05). Plant height was extremely significantly positively correlated with mean annual temperature, warm month mean temperature, cold month mean temperature, and mean annual precipitation (P < 0.01). Basal diameter and above-ground biomass showed no significant correlations with environmental factors (P > 0.05). Seed setting ratio was extremely significantly positively correlated with mean annual temperature, warm month mean temperature, cold month mean temperature, and mean annual precipitation (P < 0.01), and extremely significantly negatively correlated with soil total nitrogen (P < 0.01). Spike biomass and spike investment ratio were significantly positively correlated with mean annual temperature, warm month mean temperature, cold month mean temperature, and mean annual precipitation (P < 0.05). Seed yield and active seed number per unit area showed no significant correlations with environmental factors (P > 0.05).

Table 4 Pearson correlations between growth and reproduction indexes of Schoenoplectus tabernaemontani and climate, soil, and water factors

Plant parameter Climate factor Soil factor Water factor MAT WMT CMT Density -0.572** -0.571** -0.578** Height 0.613** 0.624** 0.598** Diameter Above-ground biomass Seed setting ratio 0.794** 0.799** 0.795** Spike biomass 0.536** 0.538** 0.531** Spike investment ratio 0.758** 0.758** 0.758** Seed production Active seed

As shown in Fig. 2, warm month mean temperature, cold month mean temperature, soil total nitrogen, and soil total phosphorus were key factors affecting clonal growth. Soil total nitrogen was the primary factor influencing density, with a path coefficient of 0.59 and contribution of 35%. Warm month mean temperature, cold month mean temperature, and soil total phosphorus were the main factors affecting plant height, with path coefficients of 0.74, -0.67, and 0.04 respectively, contributing over 90% to height variation (Fig. 2A). Soil organic carbon and mean annual precipitation were key factors affecting sexual reproduction parameters. Mean annual precipitation directly influenced seed setting ratio, spike biomass, and spike investment ratio, with path coefficients of 0.81, 0.56, and 0.82 respectively. Soil organic carbon directly affected spike investment ratio with a path coefficient of 0.32. Mean annual precipitation contributed 66% and 31% to seed setting ratio and spike biomass respectively, while mean annual precipitation and soil organic carbon together contributed 78% to spike investment ratio (Fig. 2B).

Figure 2 Relational graphs of path analysis linking growth and reproductive characteristics of Schoenoplectus tabernaemontani with key factors in Yunnan Plateau lakes. Figure A shows influencing factors and pathways for growth characteristics; Figure B shows influencing factors and pathways for sexual reproduction characteristics. Standardized path coefficients are shown beside arrows, red numbers indicate explanatory degrees, solid lines represent positive relationships, and dashed lines represent negative relationships. * indicates P < 0.05; ** indicates P < 0.01; *** indicates P < 0.001. D = Density; H = Height; SSR = Seed setting ratio; SB = Spike biomass; SIR = Spike investment ratio; STP = Soil total phosphorus; STN = Soil total nitrogen; WMT = Maximum temperature of the warmest month; CMT = Minimum temperature of the coldest month; MAP = Mean annual precipitation; SOC = Soil organic carbon.

Discussion and Conclusions

Plant growth and reproductive traits reflect strategies for resource utilization and adaptation (Chen et al., 2014). This study found substantial spatial differences in clonal growth (except above-ground biomass) and sexual reproduction parameters of S. tabernaemontani, representing the combined effects of climate, soil, and water factors in their respective lakes and reflecting plant responses to different environmental conditions. These results align with previous studies on growth traits of Xanthoceras sorbifolium and seed reproduction of S. tabernaemontani (Zhang et al., 2019; Wang et al., 2018b). However, the lack of significant differences in above-ground biomass across sites suggests that littoral zone plant biomass is not affected by geographic environmental conditions, consistent with the law of constant final yield.

Changes in plant traits such as height represent long-term adaptation to climatic conditions (Wright et al., 2005). This study found that S. tabernaemontani in northwestern Yunnan had smaller individuals, with sexual reproduction characteristics showing significant latitudinal and altitudinal zonation patterns closely related to water-heat conditions. Typically, low temperatures at high latitudes and altitudes inhibit root water and nutrient uptake, while high UV radiation reduces resource use efficiency, limiting plant growth (He et al., 2002; Peñuelas et al., 2009; Körner, 2006). From central to northwestern Yunnan, spike growth parameters gradually decreased. In high-altitude, high-latitude areas, low temperatures shorten the growing season and reduce carbon accumulation, causing plants to decrease biomass production in all parts (Méndez & Traveset, 2003; Wang et al., 2018b). Consequently, energy allocated to seed reproduction decreases with increasing altitude and latitude, leading to reduced spike growth and seed yield. This may be the primary reason for the zonal distribution patterns of S. tabernaemontani growth and reproduction characteristics along latitude, longitude, and altitude gradients.

Clonal growth and sexual reproduction are two important aspects of plant life history strategies. Relationships among different traits under varying environmental conditions reflect functional linkages. This study found close relationships between clonal growth and sexual reproduction in S. tabernaemontani. Sexual reproduction characteristics showed strong dependence on individual plant size. Plant height and basal diameter are closely related to light capture capacity, resistance to mechanical damage, and support capacity for reproductive organs. Taller plants can extend to obtain more light but have weaker resistance to mechanical damage, while larger basal diameters enhance mechanical resistance and support thicker vascular structures (Sun et al., 2016), promoting both growth and sexual reproduction. Studies have also shown that larger individual plants produce more seeds and greater total seed weight (Susko & Lovett-Doust, 1998), as larger individuals acquire more total resources and can allocate more to sexual reproduction.

Plant height in this study was closely related to temperature factors, indicating that clonal growth of S. tabernaemontani is primarily temperature-driven. Elevated temperatures can enhance photosynthetic efficiency, inhibit respiration, and promote growth. Higher temperatures also extend the growing season, accelerate organic matter decomposition and soil mineralization, and improve nutrient use efficiency (Yang et al., 2010), thereby promoting vegetative growth and carbon accumulation (Day et al., 2008). These findings align with studies on rhizome length changes under warming conditions (Li et al., 2014). Research using OTC warming techniques on the arctic species Carex bigelowii also demonstrated that temperature increases enhance plant height (Stenström et al., 1997). However, some studies have found inhibitory effects of temperature increases on clonal growth (De et al., 2008), possibly due to negative effects of intense resource competition under abiotic stress conditions. Additionally, this study found that S. tabernaemontani in lakes with higher precipitation showed greater sexual reproduction investment, while water nitrogen and phosphorus content had no significant effects, suggesting that abundant precipitation can promote sexual reproduction in emergent plants, likely related to effects of precipitation on flooding conditions in littoral zones. Given the special habitat of emergent plants, water—one of the three key elements of wetland ecosystems—includes both quantity and quality aspects. For Yunnan Plateau lakes, runoff is primarily supplied by precipitation (Yang & Li, 2010). The flowering and fruiting period of S. tabernaemontani is June–September, coinciding with Yunnan's rainy season (May–October), which shows a decreasing trend from south to north (with increasing latitude) (Yan et al., 2018), altering littoral zone water levels. Previous studies have shown that zero ground water level is unfavorable for S. tabernaemontani growth (Zhao et al., 2015), and that Typha shows increased sexual reproduction proportion with increasing water depth within 0–0.5 m (Sorrell et al., 2012). This study also found that soil nutrient content importantly affected plant growth and reproduction, with soil nitrogen having greater influence on clonal growth because plants primarily obtain nutrients from soil. Nitrogen promotes cell division and expansion, increasing leaf area for photosynthesis and thus promoting clonal growth, consistent with studies on soil nutrient effects on plant growth (Nasto et al., 2019). Path analysis revealed that the contribution to plant clonal growth and sexual reproduction characteristics followed the pattern: climatic factors > soil factors > water factors. This indicates that in Yunnan Plateau lakes, regional climatic factors (warm month mean temperature, cold month mean temperature, and mean annual precipitation) are the primary environmental factors affecting growth and reproduction of littoral zone plant S. tabernaemontani, while soil nutrients have significant effects. The influence of aquatic environmental factors on plateau lake plant reproduction characteristics under future environmental changes requires further investigation.

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