Chin J Plant Ecol

Alpine grassland water use efficiency based on annual precipitation, growing season precipitation and growing season evapotranspiration

MI Zhao-Rong,CHEN Li-Tong,ZHANG Zhen-Hua,HE Jin-Sheng

Chin J Plan Ecolo. 2015, 39 (7): 649-660. doi:10.17521/cjpe.2015.0062

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Aims Water use efficiency (WUE) is an important parameter to understand the coupling between the water, and carbon cycles of terrestrial ecosystems. Previous studies on the grassland ecosystem WUE on the Qinghai-Xizang Plateau mainly based on annual precipitation (AP). However, vegetation water use mainly occurs in growing season. Therefore, we aimed to explore the differences of ecosystem WUE between alpine meadow and alpine steppe, and the relationships between ecosystem WUE and environmental factors from 2000 to 2010, using annual precipitation use efficiency (PUE_a), growing season precipitation use efficiency (PUE_gs), growing season water use efficiency (WUE_gs) based on AP, growing season precipitation (GSP) and growing season evapotranspiration (ET_gs) respectively. Methods Combining satellite-derived above-ground net primary productivity (ANPP), satellite-derived evapotranspiration and meteorological data from 2000 to 2010, we calculated PUE_a (ANPP / AP), PUE_gs(ANPP / GSP) and WUE_gs(ANPP / ET_gs) to find the differences of PUE_a, PUE_gs and WUE_gs between alpine meadow and alpine steppe. Moreover, we explored the relationships between PUE_a, PUE_gs or WUE_gs and precipitation (or evapotranspiration) or air temperature. Important findings We found that (1) the PUE_a and PUE_gsof alpine meadow were higher than that of alpine steppe, but there were no significant difference between WUE_gs of the two grassland types, indicating that there may be similar intrinsic water use efficiencies of the two grassland types. (2) The inter-annual variation of PUE_a and PUE_gswere similar while WUE_gs showed a larger fluctuation, implying that ET-based WUE_gs was more sensitive than precipitation-based PUE_a and PUE_gs, therefore WUE_gs is a better indicator of ecosystem water use efficiency than PUE_a or PUE_gs. (3) The PUE_a, PUE_gs and WUE_gs were negatively correlated with AP, GSP and ET_gs respectively, reflecting a consistency of the three water use efficiency measurements. In the alpine steppe, only WUE_gswas observed positively correlated with air temperature among the three measurements, but in the alpine meadow, no significant relationships between water use efficiency and air temperature was detected, suggesting that the WUE_gs of alpine steppe was more sensitive to air temperature than that of alpine meadow.

Net ecosystem exchange of CO₂ on sunny and cloudy days over a reed wetland in the Yellow River Delta, China

CHU Xiao-Jing,HAN Guang-Xuan,XING Qing-Hui,YU Jun-Bao,WU Li-Xin,LIU Hai-Fang,WANG Guang-Mei,MAO Pei-Li

Chin J Plan Ecolo. 2015, 39 (7): 661-673. doi:10.17521/cjpe.2015.0063

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Aims Clouds and aerosols change the radiation level on the land surface and indirectly alter the microclimate. Shifts in sunny and cloudy days, for example, would affect the net ecosystem exchange of CO₂ (NEE) between land surface and the atmosphere. Our objective was to analyze the influence of shifts in sunny and cloudy days on NEE, its responses to light and temperature in a reed (Phragmites australis) wetland in the Yellow River Delta, China. Methods Using the eddy covariance technique, we measured the temporal changes in NEE during the growing season over the reed wetland. We selected 12 paired-days during the measurement period following two criteria: (1) the two paired days are adjacent, with one sunny day and another cloudy day; (2) no rain event during the two days. We assumed that: (1) live biomass and leaf area index (LAI) are the same during any paired-days; (2) soil moisture has no significant difference between the two adjacent days. With these criteria, we expected that radiation condition exerted the major control on NEE. Important findings Diurnal change of NEE showed a distinct U-shaped pattern on both sunny and cloudy days, but with substantial variation in its amplitude. During the daytime, NEE on sunny days was significantly higher (p < 0.01) than that on the cloudy days (n = 12). The daytime NEE response to photosynthetically active radiation (PAR) was modeled with the rectangular hyperbolic function (Eq. (1)) for both sunny and cloudy days. There appeared a significant reduction (p < 0.01) in light-saturated NEE (A_max) on cloudy days compared to the sunny days. Similarly, there was a significant decrease (p < 0.01) in daytime ecosystem respiration (R_eco,daytime) on cloudy days as compared to that of the sunny day although there existed significant exponential relationships between R_eco,daytime and air temperature on both sunny and cloudy days. In addition, the temperature sensitivity of ecosystem respiration (Q₁₀) on cloudy days (1.9) was significantly lower than that of sunny days (5.5). Stepwise multiple regression analyses suggested that PAR and T explained 63% of the changes in NEE between sunny and cloudy days. By taking advantage of the natural shift of sunny and cloudy days without disturbance to the plant-soil system, our results indicated that cloud cover significantly reduced the absorption capacity of CO₂ in the wetland. Thus, it is necessary to take into account the shits between sunny and cloudy days on NEE when predicting the ecosystem responses to future climate in the wetland.

Effects of different sources of dissolved organic matter on soil CO₂ emission in subtropical forests

WAN Jing-Juan,GUO Jian-Fen,JI Shu-Rong,REN Wei-Ling,SI You-Tao,YANG Yu-Sheng

Chin J Plan Ecolo. 2015, 39 (7): 674-681. doi:10.17521/cjpe.2015.0064

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Aims Dissolved organic matter (DOM) is an important carbon and nutrient pool, but the effects of different sources of DOM on soil carbon cycling are less well understood. Our objective in this study was to investigate how differences in the quantity and quality of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata and Castanopsis carlesii affected soil CO₂ fluxes in a laboratory incubation experiment. Methods Mineral soils (0-10 cm) from an 11-year-old Cunninghamia lanceolata plantation in Sanming of Fujian Province, China, were incubated for 59 days after adding the DOM from fresh leaves and leaf litter of Cunninghamia lanceolata and Castanopsis carlesii. Carbon (C) mineralization during incubation was determined using CO₂ respiration method. Important findings Compared to the controls, the rates of C mineralization significantly increased by 91.5%, 12.8%, 61.0% and 113.3% on day 1, following additions of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata and Castanopsis carlesii, respectively; the magnitudes of the increases declined to 24.1%, 8.3%, 14.6% and 13.2% by day 5, indicating that addition of DOM had significant but short-term influences on soil CO₂ emission. DOM from different sources had significant effects on the cumulative CO₂ production following addition of DOM by day 31 (p < 0.05). After 59 days of incubation, the cumulative quantity of mineralized C following addition of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata was significantly greater than that from those of Castanopsis carlesii, while there was no significant difference in the cumulative CO₂ production between DOM from fresh leaves and leaf litter of the same tree species, suggesting that difference in tree species had a greater influence on C mineralization than difference in the degree of leaf decay. Addition of DOM originated from fresh leaves and leaf litter of Castanopsis carlesii resulted in increased C mineralization by 22.5% and 50.0% of C added over the course of 59 day incubation, whereas increases by additions of DOM from fresh leaves and leaf litter of Cunninghamia lanceolata were 1.76 times and 2.56 times, respectively. Thus, a single addition of different sources of DOM may lead to diverse effects on total soil carbon stocks.

Stoichiometric characteristics of plants, litter and soils in karst plant communities of Northwest Guangxi

ZENG Zhao-Xia,WANG Ke-Lin,LIU Xiao-Li,ZENG Fu-Ping,SONG Tong-Qing,PENG Wan-Xia,ZHANG Hao,DU Hu

Chin J Plan Ecolo. 2015, 39 (7): 682-693. doi:10.17521/cjpe.2015.0065

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Aims The objectives of this study were to characterize the C:N:P stoichiometry of the “plant-litter-soil” continuum and to better understand nutrient cycling and stability mechanisms in karst forest ecosystems in Southwest China. Methods Three representative forest sites were selected for each of the primary and secondary communities (28 years of natural restoration) in Northwest Guangxi, and measurements were made on carbon (C), nitrogen (N), and phosphorus (P) contents in plants, litter and soils. Important findings Compared with other regions, the plants in karst forest ecosystems had relatively lower C content and higher N content, with a lower C:N ratio in consistency with the characteristics of plants. After 28 years of natural recovery, N and P absorption in secondary forests were at a relatively stable state compared with the primary forest communities. The values of N:P ratio varied from a range of 16-19 in the primary forest communities to 17-19 in the secondary forest communities, without apparent difference in the mean vale between the two contrasting community types. Soil organic C, N and P in karst forests occurred primarily in the top 0-10 cm soil layer, at 92.0 mg·g^-1 C, 6.35 mg·g^-1 N, and 1.5 mg·g^-1 P, respectively. In contrast, the nutrient utilization efficiency and nutrient resorption rate were lower in karst forest plants than in other plant types, with karst forest plants exhibiting a relatively rapid nutrient turnover rate. The N resorption rate was lower, and the P resorption higher, in the primary forest communities than in the secondary forest communities, indicating that the higher N deficiency and lower P deficiency of the primary forest communities compared with the secondary forest communities. Determination of the C:N:P stoichiometric characteristics in the plant-litter-soil continuum in this study provides a scientific guidance for restoration of the vulnerable karst ecosystem in Southwest China.

Inversion of subtropical forest stand characteristics by integrating very high resolution imagery acquired from UAV and LiDAR point-cloud

XU Zi-Qian,CAO Lin,RUAN Hong-Hua,LI Wei-Zheng,JIANG Sheng

Chin J Plan Ecolo. 2015, 39 (7): 694-703. doi:10.17521/cjpe.2015.0066

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Aims We applied the integrated very high resolution imagery acquired from Unmanned Aerial Vehicles (UAV) and Light Detection and Ranging (LiDAR) point-loud data to estimate the stand characteristics of a naturally- regenerated forest in a subtropical area. Methods The high precision digital elevation model (DEM) of the forest was constructed base on LiDAR point-cloud and the inverse distance weighted interpolation method. The 3D point-cloud of forest canopy layer was constructed from UAV image pairs, with information from DEM height information normalization, for canopy height and density. With the above effort, we developed a prediction model to estimate Lorey’s height, stand density, basal area, and volume. Important findings The quantitative metrics generated from this study appeared very sensitive to Lorey’s height, followed by volume and basal area. Using UAV as a flexible and rapid method for generating forest canopy characteristics, combined with topographic information from high precision LiDAR data, seems a viable, rapid, inexpensive, and flexible method in canopy research.

Spatial distribution of species and influencing factors across salt marsh in southern Chongming Dongtan

DING Wen-Hui,JIANG Jun-Yan,LI Xiu-Zhen,HUANG Xing,LI Xi-Zhi,ZHOU Yun-Xuan,TANG Chen-Dong

Chin J Plan Ecolo. 2015, 39 (7): 704-716. doi:10.17521/cjpe.2015.0067

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Aims The relationship between vegetation structure and environment factors is an important subject in plant ecology. The elevation and soil salinity of the tidal flat are the important factors affecting the vegetation community. Both the elevation and salinity at our sites showed clear gradients. The aims of this study were to: (1) investigate the major species and their distributions in southern Chongming Dongtan; and (2) quantify the two factors that influence the vegetation distribution: elevation and soil salinity. Methods Based on the spatial grid sampling and the spatial interpolation in 2013, we analyzed the distribution of key species as well as their empirical relationships with the environmental factors. Important findings We found that both elevation and soil salinity were significantly different among the vegetation cohorts (p < 0.01). Along the elevation gradient, sedges distributed mainly in the low tidal zone of 2.93-4.07 m, while Gramineae species were found in the middle and high tidal flat (3.13-4.31 m). Soil salinity of the 30 cm surface in Scirpus mariqueter and Spartina alterniflora zone was around (3.2 ± 0.6) g·kg^-1, which was significantly higher than that of other groups (2.0 ± 0.3) g·kg^-1 (p < 0.01). Scirpus mariqueter, a key and pioneer species at our sites, was mainly found at elevation of 2.53-3.97 m, with 80% of the area overlapping with the habitats of Spartina alterniflora. More than 90% of the Scirpus mariqueter located in the northeast of the study area. The soil salinity of the study site was 1.6-4.5 g·kg^-1, with Scirpus mariqueter and Spartina alterniflora showed positive adaptations. Spartina alterniflora replaces Scirpus mariqueter with increasing elevation due to its high competitive ability. The total area of Scirpus mariqueter was 294 hm², with a dominant area of only 120 hm². Scirpus mariqueter occupied 15.7% of the sedge dominated area and 6.9% of the total study area, which is the least among six species (Phragmites australis, Imperata cylindrica, Spartina alterniflora, Carex scabrifolia, Scirpus triqueter and Scirpus mariqueter). It is of great challenge to restore and protect this important endemic species.

Composition and monthly dynamics of tree seedlings in a coniferous and broad-leaved mixed forest in Jiaohe, Jilin Province, China

YAO Jie,YAN Yan,ZHANG Chun-Yu,PI Tian-Hui,ZHAO Xiu-Hai

Chin J Plan Ecolo. 2015, 39 (7): 717-725. doi:10.17521/cjpe.2015.0068

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Aims The objective of this paper is to quantify the composition and dynamics of tree seedlings in the coniferous and broad-leaved mixed forest in north-eastern China. Methods We installed 224 sampling quadrats (1 m × 1 m) at the Jiaohe Experimental Forest in Jilin Province of northeastern China. All seedlings in the quadrats were tagged and measured by species. Based on three consecutive sampling from mid-June to mid-August in 2013, we studied the species composition and dynamics of tree seedlings by month. Multiple linear regression was used to quantify the relationship between seedlings and the neighboring trees with the diameter at breast height (DBH) of 1 cm. Important findings A total of 16 species were recorded. There was no significant difference in species composition between June and July, but a great variation in the seedling composition in August. From June to August 2013, 1214 out of 1722 individual seedlings survived. There were significant differences in the total number and the number of individual species in the quadrats. The death and recruitment pattern of newborn seedlings showed significant differences among species and by month. The mortality rate in June was 48.9%, which was significantly higher than that in August (28.3%). The mortality rate of perennial seedlings during the observation period was 7.34%, which was significantly less than the mortality rate of new seedlings (40.56%). We found that the recruitment rate of the dominant species in July was higher than that in August. The recruitment occurred mostly in June. Multiple linear regression was used to analyze the relationship between the seedling abundance of eight species and the number of conspecifics, as well as the sum of conspecific basal areas within 20 m distance from a station. Factors influencing seedling abundance differed among species. For Acer mono, Tilia amurensis and Abies holophylla, significant partial regression coefficients appeared positive (p = 0.006, 0.013, 0.037, respectively), indicating that the seedling abundance increased with basal area. Other species did not show this correlation.

Spatial analysis of competition in natural Phyllostachys edulis community

CHEN Yong-Gang,TANG Meng-Ping,YANG Chun-Ju,MA Tian-Wu,WANG Li

Chin J Plan Ecolo. 2015, 39 (7): 726-735. doi:10.17521/cjpe.2015.0069

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Aims Spatial analysis of competition is an effective method to understand trend, variability and distribution patterns of plant communities. The objective of this study was to improve our understanding of autocorrelation distribution, the relationship between competition intensity and density and age of Phyllostachys edulis, and the relationship between competition intensity anisotropy and the aspect of sample plots. Methods Based on data collected from natural P. edulis forest plots located in Tianmu Mountain of Zhejiang Province, we calculated Hegyi competition index in Geographic Information System (GIS). ESDA (exploratory spatial data analysis) was used to analyze the spatial distribution of the Hegyi competition index to identify the spatial distribution. Spatial semivariogram and standard deviation ellipse were used to study regionalized spatial variability of variables. Important findings The results showed that the spatial densities and the competition intensity of natural P. edulis forest was autocorrelated: Phyllostachys edulis density was higher in area of high competition intensity. The age of P. edulis was also different between areas of different competition intensities: Phyllostachys edulis was younger in plots of low competition intensity than in plots of high competition intensity. The anisotropy of the competition intensity was higher in the vertical direction than in the horizontal direction.

Dust capturing capacities of twenty-six deciduous broad-leaved trees in Beijing

FAN Shu-Xin,YAN Hai,QI Shi-Ming-Yue,BAI Wei-Lan,PI Ding-Jun,LI Xiong,DONG Li

Chin J Plan Ecolo. 2015, 39 (7): 736-745. doi:10.17521/cjpe.2015.0070

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Aims Aiming at providing basic informations on dust capturing capacity of different tree species and criterions for selecting trees in landscape design, this study selected 26 deciduous broad-leaved tree species widely used in urban landscaping in Beijing to measure the dust capturing both in field and indoor experiments. Methods The dust deposition per unit leaf area of each species was quantified by determining the mass difference before and after the treatment of blades. The dust deposition per leaf and plant were further calculated for each species. Based on the dust capturing capacity measured in three different units, cluster analysis on different tree species was carried out from distinct dimensions. Important findings Results showed that the dust capturing capacity differed significantly among tree species, and the ranking changed with measurement units selected in the experiments. For different specific evaluation focuses, choosing a diverse unit combination as clustering factor, the 26 deciduous broad-leaved tree species were broadly divided into different categories representing different dust capturing capacity level. Dust capturing capacity was closely related to the surface characteristics of leaves, the dust capturing method, the plant structure, the leaf amount of whole plant, the dust content of the environment, etc. Therefore, multiple factors should be taken into account in the assessment of dust capturing capacity of different tree species.

Variations of non-structural carbohydrate concentration of Picea meyeri at different elevations of Luya Mountain, China

WANG Biao,JIANG Yuan,WANG Ming-Chang,DONG Man-Yu,ZHANG Yi-Ping

Chin J Plan Ecolo. 2015, 39 (7): 746-752. doi:10.17521/cjpe.2015.0071

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Aims The alpine timberline is highly sensitive to environmental changes, although the mechanism controlling timberline formation is still inconclusive. Our objectives in this study were to test whether the alpine timberline formation is determined by carbon limitation or growth limitation, and explore physiological and ecological mechanisms of timberline tree species adapting to alpine environments. We examined the concentrations of the overall nonstructural carbohydrates (NSC) and tissues NSC of Picea meyeri at the end of growing season and in three elevations (low, medium and timberline) along an altitudinal gradient on the north slope of Luya Mountain, Shanxi, China. Methods We collected samples of leaf, stem and fine root tissues of P. meyeri on September 15, 2013. The total soluble sugar concentration of plant tissue was measured by an anthrone-sulfuric acid colorimetric method, and starch was extracted by a perchloric acid method. Important findings The overall NSC and tissues NSC increased significantly with elevation, suggesting that there was no carbon limitation at the alpine timberline. The NSC source and sink are all increased significantly with elevation, and there is no significant difference in the source-sink ratio among three elevations, indicating an adaptation of source-sink balances to altitudes and no restriction of carbon source activity in timberline trees. The ratio of sugar to starch in tissues showed an increasing trend with elevation, which suggests that the colder the environment was, the stronger the protective strategy adopted in plant tissues through resource investments, implying more growth limitation in trees near timberlines, The research results appear to support the “growth limit” hypothesis to some degree.

Floral morphology and pollination mechanism of Salvia liguliloba, a narrow endemic species with degraded lever-like stamens

HUANG Yan-Bo,WEI Yu-Kun,WANG Qi,XIAO Yue-E,YE Xi-Yang

Chin J Plan Ecolo. 2015, 39 (7): 753-761. doi:10.17521/cjpe.2015.0072

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Aims Diverse stamen structures and interactions with pollinators make Salvia the model plants for studying evolutionary changes in plant pollination mechanisms. The dorsal pollination mechanism of lever-like stamens has been extensively investigated as a classic example for precise interactions between plants of Salvia genus and their pollinators. However, there are many atypical lever-like structures and pollination mechanisms among Salvia species. For example, Salvia liguliloba has floral organ structures and a pollination mechanism characterized by degenerated lever-like stamens. The aim of this work was to understand the selection pressure and ecological significance of Salvia plants that have the atypical staminal level mechanism. Methods In this study, we described the morphological features of S. liguliloba, a plant species endemic to the Tianmu Mountains, and investigated its pollination ecology in detail. Various components of the flower of S. liguliloba were measured, which included the corolla, corolla tube, corolla entrance, filament, connective and pistil. Flower-visiting insects, pollinators, and the pollination process were observed and recorded by a digital video camera. Furthermore, we focused on comparing the floral organ structures and the pollination characteristics of S. liguliloba with those of S. digitaloides, which has a short-lever stamen. The relative frequency of insects, visiting time per flower, activity rate and visitation rate were measured and compared with the data from our previous study of S. digitaloides, for which the flower structure and pollination features were well concluded. Important findings Salvia liguliloba has smaller corolla length, tube width, and shorter filament and pistil than S. digitaloides (p < 0.05). The only effective pollinator was Bombus trifasciatus, and its average relative visiting frequency and the visiting time per flower were (0.959 ± 0.065) and (1.54 ± 0.60) s. The degenerated lower arm and limited moving space in the upper arm of the stamen restrict the pollinating insects from pushing the stamens in a lever-like motion. Thus, bumblebees completed pollination with the aid of their heads. Compared with the structure of the lever-like stamen and the pollination mechanism of S. digitaloides, the structural features of the floral organs of S. liguliloba make it adapt to a more specific pollinator with shorter visiting time and higher activity rate. The results suggested that the species with degraded lever-like stamens might be different from other typical Salvia species in their evolution direction and reproductive strategy.

Divergent ramet ratio affects water physiological integration in Indocalamus decorus: Activity of antioxidant system and photosynthetic pigment content

HU Jun-Jing,CHEN Shuang-Lin,GUO Zi-Wu,CHEN Wei-Jun,YANG Qing-Ping,LI Ying-Chun

Chin J Plan Ecolo. 2015, 39 (7): 762-772. doi:10.17521/cjpe.2015.0073

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Aims Physiological integration of clonal plants allows resources to transport and share among ramets to enhance plant adaptability to a dynamic habitat. Water physiological integration is an important part of physiological integration of clonal plants. Comprehensive understanding of the integration in bamboo is especially important because of the diverse ramet organizations. To provide scientific basis for effective management of water supply for bamboo forests, this study aims to explore the direction and the magnitude of ramet distribution in water physiological integration. Methods Our experiment was designed for clonal ramets of Indocalamus decorus with two levels of water content (high water potential at 90% ± 5% and low water potential at 30% ± 5%) and five ramet ratios (1:3, 1:2, 1:1, 2:1, 3:1). Each manipulation was replicated in 12 strains of ramets. We measured the antioxidant enzyme activity, content of soluble protein, malondialdehyde, and photosynthetic pigment. Important findings Water physiological integration existed in I. decorus clonal system under different water conditions, allowing water to transfer from high to low water potential ramets. With ramet ratio increase, integration intensity was enhanced, suggesting that the benefit of receptor ramet from the donor ramet increased. Water integration intensity between connected clonal ramets was high in early stage but decreased over time, which reflected that the consumption-benefit effect of donor and receptor ramets. These results indicated that ramet ratio of clonal system has a major impact on water physiological integration. We conclude that water gradient among the ramets is a potential driving force for water transport. The direction and the magnitude of physiological integration seemed determined by the status of water supply and demand in our intra-clonal system.