[Show abstract][Hide abstract] ABSTRACT: Alien plant invasions usually cause economic and ecological losses. Currently, exotic plants have already appeared in the understory of mountain forests that are subjected to relatively less human disturbance and are often thought of as a safe shelter for most native plants. This study aims to explore invasions patterns and underlying mechanisms in the understory of Chinese mountain forests. Sixty-three quadrats of 20 m × 30 m were systematically set up along the elevation gradient on Mount Tai and Mount Lao, Shandong Province, China. We examined the variation in alien and native plant richness and composition along the elevation gradient to explore the invasion mechanisms of alien species in mountain forests and analyzed the relationship between alien species richness and environment factors (human disturbance, slope, aspect and canopy density) in both mountains. In contrast to native plants, which presented two different richness patterns along the elevation gradient on Mount Tai and Mount Lao, alien species richness presented a consistent decreasing tendency with increasing elevation, suggesting that mechanisms driving native and alien species richness may be different. While native plants had many specialists at high altitudes and presented an obvious change of chorological groups along the elevation gradient, most alien species distributed in high altitude areas also occurred at lower elevations. All findings indicated that the invasion process in mountain forests is from great majority of alien species that are introduced at low altitude, successively filtered out by worsening climatic conditions and decreasing anthropogenic propagule pressures along the elevation gradient, and a subset of this community spreads upward to high altitude areas. Plots with high exotic species richness where generally subject to high levels of human disturbance. We conclude that approaches of monitoring and managing alien plant species should focus on low elevation areas of mountain forests to prevent invasions of high elevation areas.
[Show abstract][Hide abstract] ABSTRACT: Recurrent water level fluctuation and submergence of plants are common in riparian zones. Our study objectives were to test the independent and interactive effects of submergence level and fluctuation frequency on a globally important riparian invasive plant, Alternanthera philoxeroides. To this end, we conducted a greenhouse experiment, in which ramets of the plants, obtained from a wetland in China, were treated with four fluctuation frequencies (0, 3, 6, and 12 cycles over a 96-day experimental period) under three water levels (0, 10, and 30 cm). We found that effects of fluctuation frequency were non-significant, negative, and positive under water levels of 0, 10 and 30 cm, respectively. As fluctuation frequency increased, the effects of increasing water level decreased significantly. When water levels were high, A. philoxeroides allocated greater biomass to shoot production probably in order to elongate and escape from submergence. However, as fluctuation frequency increased, biomass investment in roots and leaves also increased, probably in order to maximize nutrient absorption and photosynthesis, respectively. These results suggest that water level fluctuation may alleviate the effects of submergence on A. philoxeroides. In addition, A. philoxeroides showed significant phenotypic plasticity, adjusting its functional traits, such as number of nodes and leaves per stem, as well as stem diameter and pith cavity diameter, according to recurrent water level fluctuation. We conclude that A. philoxeroides may perform better in shallow water zones under conditions of disturbance that include recurrent water level fluctuation. This ability to adapt to disturbance likely promotes its growth and invasion in disturbed habitats.
PLoS ONE 06/2015; 10(6):e0129549. DOI:10.1371/journal.pone.0129549 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The plasticity response of Quercus variabilis and Quercus mongolica seedlings to combined nitrogen (N) deposition and drought stress was evaluated, and their performance in natural niche overlaps was predicted. Seedlings in a greenhouse were exposed to four N deposition levels (0, 4, 8, and 20 g N m−2 year−1) and two water levels (80 and 50 % field-water capacity). Plant traits associated with growth, biomass production, leaf physiology, and morphology were determined. Results showed that drought stress inhibited seedling performance, altered leaf morphology, and decreased fluorescence parameters in both species. By contrast increased N supply had beneficial effects on the nutritional status and activity of the PSII complex. The two species showed similar responses to drought stress. Contrary to the effects in Q. mongolica, N deposition promoted leaf N concentration, PSII activity, leaf chlorophyll contents, and final growth of Q. variabilis under well-watered conditions. Thus, Q. variabilis was more sensitive to N deposition than Q. mongolica. However, excessive N supply (20 g N m−2 year−1) did not exert any positive effects on the two species. Among the observed plasticity of the plant traits, plant growth was the most plastic, and leaf morphology was the least plastic. Therefore, drought stress played a primary role at the whole-plant level, but N supply significantly alleviated the adverse effects of drought stress on plant physiology. A critical N deposition load around 20 g N m−2 year−1 may exist for oak seedlings, which may more adversely affect Q. variabilis than Q. mongolica.
Acta Physiologiae Plantarum 06/2015; 37(6). DOI:10.1007/s11738-015-1853-4 · 1.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background and aims Increasing atmospheric nitrogen (N) deposition and biological invasion have become major concerns with global environmental change. This study aimed to determine the effects of an exotic species on a native one under increasing N deposition. Methods We conducted a greenhouse experiment in which the exotic species Robinia pseudoacacia and the native species Quercus acutissima were grown inmixture and monocultures under four levels of simulated N deposition (0, 3, 6, 12 g m(-2) year(-1)). After 12 weeks of treatment, plant growth, leaf physiological traits and soil chemical properties were determined. Results With its strong capability for nutrient absorption and carbon assimilation, R. pseudoacacia dominated in competition. R. pseudoacacia reduced the growth of Q. acutissima, but the relative competition index decreased with increasing N deposition. At the end of the experiment, the soil available phosphorus (P) in mixture was significantly lower than that in the monoculture of Q. acutissima, while the soil available N in the two cultivations did not show obvious differences. Conclusions Increased N deposition alleviated the competitive effects of R. pseudoacacia on Q. acutissima. In the future, besides N, increased P availability should also be considered in the interaction between the two species.
Plant and Soil 12/2014; 385(1-2):63-75. DOI:10.1007/s11104-014-2227-1 · 2.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Background and aims
Anthropogenic nitrogen (N) and phosphorus (P) input has changed the relative importance of nutrient elements. This study aimed to examine the effects of different nutrient conditions on the interaction between exotic and native plants.
We conducted a greenhouse experiment with a native species Quercus acutissima Carr. and an exotic species Rhus typhina L. grown in monocultures or mixtures, under three N:P ratios (5, 15 and 45 corresponding to N-limited, basic N and P supply and P-limited conditions, respectively). After 12 weeks of treatment, traits related to biomass allocation, leaf physiology and nutrient absorption were determined.
R. typhina was dominant under competition, with a high capacity for carbon assimilation and nutrient absorption, and the dominance was unaffected by increasing N:P ratios. R. typhina invested more photosynthate in leaves and more nutrients in the photosynthetic apparatus, enabling high biomass production. Q. acutissima invested more photosynthate in roots and more nutrients in leaf persistence at the expense of reduced carbon assimilation capacity.
Different trade-offs in biomass and nutrient allocation of the two species is an important reason for their distinct performances under competition and helps R. typhina to maintain dominance under different nutrient conditions.
Plant and Soil 11/2013; 372(1-2). DOI:10.1007/s11104-013-1748-3 · 2.95 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Light and soil moisture availability are two important abiotic factors influencing plant growth in an agroforestry system. Different soil moisture and light treatments were applied to examine the combined impact of drought and shade on the morphological plasticity of Vitex negundo var. heterophylla (Chinese chastetree) and Ziziphus jujuba var. spinosa (Spine jujube). We found that the interaction of light and soil moisture was orthogonal in the two species. V. negundo captured irradiance efficiently with relatively long petiole and petiolule, while Z. jujuba maintained higher branches to absorb light than V. negundo. Compared to the seedlings under full sunlight, the palmately compound leaves of V. negundo under low light showed larger specific leaf area (SLA), lower ratio of leaflet length to width and higher leaf mass ratio (leaf biomass to total biomass); in contrast, the simple leaves of Z. jujuba under low light showed larger SLA and ratio of leaf length to petiole length. In both species, drought reduced the branch number, mean internode length of stem, and increased root mass ratio (root biomass to total biomass), but leaf morphology showed little variation to the decreased soil moisture. Between the two species, V. negundo is more shade-tolerant, while Z. jujuba is more drought-tolerant. In an alley cropping system, the spacing can be smaller in the V. negundo-crop system than the Z. jujuba-crop system when soil moisture is adequate. However, the V. negundo-crop system should be managed with more caution under the soil moisture limited conditions.
Agroforestry Systems 04/2012; 87(2). DOI:10.1007/s10457-012-9562-0 · 1.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Acer buergerianum Miq. (Trident maple) is a native species of China with a large distribution, but exist in small population. Water and light are two important factors limiting plant growth and are crucial in the framework of forest regeneration. However, there is no consensus on how shade interacts with drought. Four hypotheses in the recent literature variously predict that shade will have a stronger, weaker or equal impact on seedlings under drought stress. This study investigated the interactive responses of A. buergerianum to light and water focusing on seedling growth, leaf morphology and biomass partitioning by performing a growth experiment in pots with different water supply regimes [15, 35, 55, 75, 95 % of field capacity (FC)] combined with two light regimes (10 and 66 % of full sunlight). After 123 days treatment, the results showed that shade greatly reduced growth and biomass, in contrast enhancing the amount of chlorophyll, the amount of water in the leaves, and the specific leaf area. Drought reduced growth, biomass, and the bulk of the leaves. Most leaf traits and biomass characteristics had strong interactions in their responses to light and water treatments. Allometric analysis revealed that water and light had no effects on root to shoot ratios, main root to lateral root ratios, and root mass ratios. Shade alleviated the negative impact of drought. A. buergerianum successfully adapted to the various light and water conditions. We recommend a water supply above 15 % FC to keep the seedlings vigorous, under both sunlight conditions.
Acta Physiologiae Plantarum 04/2012; 35(4). DOI:10.1007/s11738-012-1154-0 · 1.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Competition plays an important role in the replacement of native species by alien plants. A greenhouse experiment was conducted to investigate whether the competition pattern of alien Robinia pseudoacacia L. and native Quercus acutissima Carr. is affected by soil sterilization. Physiological traits, such as gas-exchange parameters and chlorophyll (Chl) content, and growth traits, such as the biomass accumulation of the two species, were examined in natural soil or in soil sterilized with benomyl. The results show that native Q. acutissima inhibits the growth of R. pseudoacacia in natural soil. When the two plants coexisted and competed under sterilization treatment, R. pseudoacacia was less inhibited by Q. acutissima and the competition of R. pseudoacacia decreased the growth of Q. acutissima in terms of biomass, Chl a, Chl b, total Chl, and Chl a/b. These results suggest that soil sterilization benefits the growth of R. pseudoacacia and changes the competition pattern by the changed soil biota. Soil sterilization increased the biomass of root nodules, which ultimately benefits the growth of R. pseudoacacia and root nodule bacteria may be important in the dispersal and invasion process of nitrogen-fixing alien plants such as R. pseudoacacia.
[Show abstract][Hide abstract] ABSTRACT: Water is a main factor limiting plant growth. Integrative responses of leaf traits and whole plant growth to drought will
provide implications to vegetation restoration. This study investigated the drought responses of Vitex negundo L. var. heterophylla (Franch.) Rehd. with a focus on leaf morphology and physiology, seedling growth and biomass partitioning. Potted 1-year-old
seedlings were subjected to four water supply regimes [75, 55, 35 and 15% field capacity (FC)], served as control, mild water
stress, moderate water stress and severe water stress. Leaf morphological traits varied to reduce the distance of water transfer
under water stress and leaflets were dispersed with drought. Net photosynthetic rate decreased significantly under water stress:
stomatal closure was the dominant limitation at mild and moderate drought, while metabolic impairment was dominant at severe
drought. The physiological impairment at severe drought could also be detected from the relative lower water use efficiency
and non-photochemical quenching to moderate water stress. Total biomass of well-watered plants was more than twice that at
moderate water deficit and nearly ten times that at severe water deficit. In summary, V. negundo var. heterophylla had adaptation mechanism to water deficit even in the most serious condition, but different strategies were adopted. Seedlings
invested more photosynthate to roots at mild and moderate drought while more photosynthate to leaves at severe drought. A
nearly stagnant seedling growth and a sharp decline of total biomass were the survival strategy at severe water stress, which
was not favorable to vegetation restoration. Water supply above 15% FC is recommended for the seedlings to vegetation restoration.
KeywordsChlorophyll fluorescence-Cut-leaf chaste tree-Leaf traits-Photosynthesis-Relative growth rate-Vegetation restoration
Acta Physiologiae Plantarum 09/2010; 32(5):839-848. DOI:10.1007/s11738-010-0468-z · 1.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Leaf morphological, physiological and biochemical characteristics of Robinia pseudoacacia L. seedlings were studied under different stress conditions. The plants were subjected to drought and shade stress for one
month. Leaf inclination, chlorophyll fluorescence and chlorophyll content were measured at the first day (short-term stress)
and at the end of the stress period (long-term stress) and in the recovery period. Leaf inclination was affected mainly by
light; a low level of irradiance caused leaves to be arranged horizontally. Diurnal rhythmicity was lost after the long-term
stress, but resumed, in part, in the recovery period. Drought stress caused leaves to tilt more obviously and decreased damage
to the photosystem. Sun avoiding movement in a single leaf and sun tracking movement in the whole plant coexisted. Significant
physiological changes occurred under different conditions of light. Increased energy dissipation and light capture were the
main responses to high and low level of irradiance, respectively, and these were reflected by changes of chlorophyll fluorescence
and chlorophyll content. Phenotypic plasticity in the leaflet enhanced the protective response to stress. These adaptive mechanisms
may explain better survival of R. pseudoacacia seedlings in the understory, especially during the drought periods, and made it to be the preponderant reforestation species
in Shandong Province of China.
Acta Physiologiae Plantarum 05/2009; 31(3):553-563. DOI:10.1007/s11738-008-0265-0 · 1.58 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: This paper presents a case study on structure design and establishment of database application system for alien species in
Shandong Province, integrating with Geographic Information System, computer network, and database technology to the research
of alien species. The modules of alien species database, including classified data input, statistics and analysis, species
pictures and distribution maps, and out date input, were approached by Visual Studio.net 2003 and Microsoft SQL server 2000.
The alien species information contains the information of classification, species distinction characteristics, biological
characteristics, original area, distribution area, the entering fashion and route, invasion time, invasion reason, interaction
with the endemic species, growth state, danger state and spatial information, i.e. distribution map. Based on the above bases,
several models including application, checking, modifying, printing, adding and returning models were developed. Furthermore,
through the establishment of index tables and index maps, we can also spatially query the data like picture, text and GIS
map data. This research established the technological platform of sharing information about scientific resource of alien species
in Shandong Province, offering the basis for the dynamic inquiry of alien species, the warning technology of prevention and
the fast reaction system. The database application system possessed the principles of good practicability, friendly user interface
and convenient usage. It can supply full and accurate information inquiry services of alien species for the users and provide
functions of dynamically managing the database for the administrator.
Journal of Forestry Research 03/2007; 18(1):11-16. DOI:10.1007/s11676-007-0002-3