基于野外调查和同质种植园实验的芦苇植物功能性状变异研究

研究表型可塑性和遗传变异在植物表型分化中的相对作用,有助于预测全球环境变化下的植物群落组成和生态系统功能的变化。芦苇（Phragmites australis）是全球性广布的草本植物,种内变异丰富,在我国西北和东部均存在多个分化稳定的生态型,但中国芦苇在更大尺度上的表型研究还非常匮乏。将位于黄河上游的宁夏平原和黄河下游的黄河三角洲作为研究区域,通过野外调查和同质种植园实验对芦苇自然种群的植物功能性状变异进行观测。结果表明,无论在野外还是同质种植园,黄河三角洲芦苇的基径、叶长和叶宽均显著大于宁夏平原芦苇,说明两个地区的芦苇种群之间存在着受遗传决定的表型分化,这可能与两个地区间的降水等气候差异有关。在野外,宁夏芦苇的株高和叶厚显著大于黄河三角洲芦苇,但在同质园中差异消失或相反,说明株高、叶厚受环境影响较大,表型可塑性也是芦苇适应环境变化的重要机制。在同质种植园中,宁夏平原芦苇的叶片氮磷含量较低,但株数却显著多于黄河三角洲芦苇,反映了不同地区芦苇之间存在不同的适应策略,宁夏平原芦苇更偏向于高扩散率的杂草策略,而黄河三角洲芦苇更偏向于竞争策略。此外,宁夏平原芦苇的株高、叶长两个性状以及基径-比叶面积相关性在野外和同质园两个环境中存在一致性,表明了性状变异和权衡策略的遗传稳定性。综上,位于黄河上下游的芦苇种群间存在着适应性分化,这是表型可塑性和遗传变异共同作用的结果,不同来源芦苇对全球变化下的多重环境因子的响应还需要进一步研究。     

同期生长在种源地与异地同质园刨花楠叶性状分析

为辨别环境变化与遗传因素对植物叶片主要功能性状的影响,以同期生长在4种源地母树林下及异地同质园的1.5年生刨花楠苗木为研究对象,对其叶片表型及养分性状进行对比分析。结果显示：(1)刨花楠叶面积、叶厚、叶干物质含量等叶片表型性状受遗传与环境因素共同影响;叶片碳(C)含量受遗传因素调控,环境对其影响较小;叶片氮、磷(N、P)含量主要受环境因素影响;(2)不同种源刨花楠比叶面积、叶厚、叶干物质含量、叶形指数等性状变异系数较大(8.85%—37.03%),其中江西遂川种源变异系数相对较大,而湖南茶陵种源则相对较小,各种源都倾向于通过调节比叶面积、叶厚、叶片氮磷含量等性状以适应生境变化;(3)种源地与同质园刨花楠的比叶面积虽均与叶厚呈显著负相关,但同质园刨花楠比叶面积与叶形指数呈显著正相关,与叶片氮含量无明显相关,而种源地刨花楠比叶面积则与叶形指数无明显相关,与叶片氮含量则呈显著负相关;(4)不同种源苗木叶性状指标在种源地与同质园间存在不同的协调与权衡,体现了植物在不同生境下的适应策略。其中湖南茶陵种源在两种生境下都具有更保守的资源获取策略,而江西安福种源对环境变化则更为敏感,资源获取策略更为灵...     

Do rock endemic and widespread plant species differ under the Leaf–Height–Seed plant ecology strategy scheme?

Westoby (1998) proposed the Leaf–Height–Seed (L–H–S) scheme, i.e. the use of three functional traits, specific leaf area (SLA), plant canopy height and seed mass, to describe plant ecological strategies. In this study, we examine whether endemic species from cliffs and rocky outcrops can be discriminated in a regional Mediterranean flora according to these three traits. First, we conducted a comparison across 13 pairs of rock endemic species and widespread congeners. Second, we performed a canonical discriminant analysis to compare the position in the L–H–S volume of these 13 pairs of endemic and widespread congeners with that of 35 phylogenetically unrelated widespread species taken from the same regional flora. Our results show that rock endemic species only differ from their widespread congeners in their smaller stature. However, when compared with the 35 unrelated widespread species, endemic species are discriminated by higher SLA and taller stature, and thus are not close to the stress‐tolerant pole of ecological strategies (small stature, low SLA), as hypothesized in the literature.     

Environmental factors covary with plant diversity–productivity relationships among Chinese grassland sites

Aim Our objective was to document the general relationship between plant species richness (SR) and above‐ground net primary productivity (ANPP) at different spatial scales and the environmental influence on this relationship. Location Temperate and alpine grasslands of China. Methods We investigated SR and ANPP at 321 field sites (1355 plots) across the widely distributed temperate and alpine grasslands of China. Ordinary least squares (OLS) regressions were used to test SR–ANPP relationships among site means. Plot‐level data of SR and ANPP were analysed with general linear models (GLMs) and the correlation between SR and ANPP was decomposed into covariance components to test the influence of climatic variables, region, vegetation type and remaining variation among sites on SR, ANPP and their relationship. Results We found positive linear relationships between SR and ANPP among sites in both the alpine and temperate grassland regions and in different grassland vegetation types of these biomes. Environmental gradients such as growing‐season precipitation affected both SR and ANPP in parallel. However, after removing the among‐site environmental variation, residual SR and ANPP were no longer correlated at the pooled within‐site level. Main conclusions The positive SR–ANPP relationship across large‐scale environmental gradients among sites was most likely the result of climatic variables influencing SR and ANPP in parallel. Our results suggest that in China's natural grasslands there is no direct relationship between SR and ANPP, presumably because the pool of available species for local community assembly is large, in contrast to experiments where species pools are artificially reduced.     

Comparison of defence and performance traits between one widespread clone and native populations in a major invasive plant species

Aim

The success of invasive species in their introduced range is often assumed to result from evolutionary changes in defence and growth traits, or as a response to more favourable conditions. The latter is assumed particularly for species exhibiting low, or even no, sexual reproduction in the introduced range.

Location and Methods

Here, we compared Japanese (native range) and French (introduced range) populations of Fallopia japonica under common growth conditions in a glasshouse. We measured height, aboveground and belowground mass, stem stiffness, leaf toughness and secondary metabolites found in hydroalcoholic extracts of rhizomes of F. japonica, as well as the competitive response of Rubus caesius (a co‐occurring native species in the invaded range) in the presence of F. japonica from both ranges.

Results

Aboveground biomass, height, stem stiffness and composition of secondary metabolites were not significantly different between the two ranges, showing that increased aboveground vigour observed in situ in France is probably the result of a plastic response following the release of abiotic or biotic constraints from the native range. On the other hand, belowground mass, effect on R. caesius, and leaf toughness were all higher in French populations, suggesting increases in competitive ability and defence mechanisms. These differences between France and Japan may be explained either by post‐introduction evolution or by the introduction in Europe, in nineteenth century, of an exceptionally vigorous clone (pre‐adaptation).

Main conclusions

Our results provide evidence that the high vigour of this major invasive species in its introduced range is probably due to both a response to more favourable conditions and rapid evolution.

     

Trait‐based analysis of decline in plant species ranges during the 20th century: a regional comparison between the UK and Estonia

Although the distribution ranges and abundance of many plant species have declined dramatically in recent decades, detailed analysis of these changes and their cause have only become possible following the publication of second‐ and third‐generation national distribution atlases. Decline can now be compared both between species and in different parts of species' ranges. We extracted data from distribution atlases to compare range persistence of 736 plant species common to both the UK and Estonia between survey periods encompassing almost the same years (1969 and 1999 in the UK and 1970 and 2004 in Estonia). We determined which traits were most closely associated with variation in species persistence, whether these were the same in each country, and the extent to which they explained differences in persistence between the countries. Mean range size declined less in Estonia than in the UK (24.3% vs. 30.3%). One‐third of species in Estonia (239) maintained >90% of their distribution range compared with one‐fifth (141) in the UK. In Estonia, 99 species lost >50% of their range compared with 127 species in the UK. Persistence was very positively related to original range in both countries. Major differences in species persistence between the studied countries were primarily determined by biogeographic (affiliation to floristic element) and ecoevolutionary (plant strategy) factors. In contrast, within‐country persistence was most strongly determined by tolerance of anthropogenic activities. Decline of species in the families Orchidaceae and Potamogetonaceae was significantly greater in the UK than in Estonia. Almost all of the 736 common and native European plant species in our study are currently declining in their range due to pressure from anthropogenic activities. Those species with low tolerance of human activity, with biotic pollination vectors and in the families referred to above are the most vulnerable, especially where human population density is high.     

Suites of root traits differ between annual and perennial species growing in the field

Here, we tested whether root traits associated with resource acquisition and conservation differed between life histories (annuals, perennials) and families (Fabaceae, Asteraceae and Poaceae). Root topology, morphology, chemistry and mycorrhizal colonization were measured on whole root systems of 18 field-grown herbaceous species grown and harvested in central Argentina. Annuals differed from perennials in several root traits important in resource uptake and conservation. They exhibited higher specific root length (SRL), root nitrogen concentration (RNC) and mycorrhizal colonization but had lower root tissue density (RTD) than perennials. They did not differ in topology or construction cost. These differences were consistent among families. Families differed only in a few root traits known to be strongly associated with certain lineages such as topology and nitrogen concentration. There was a strong parallel between root traits and analogous leaf traits described in the literature for annuals and perennials. Our results suggest the existence at the root level of an acquisitive vs conservative syndrome consistent among families similar to that previously reported for above-ground traits.     

Trait‐based approach confirms the importance of propagule limitation and assembly rules in old‐field restoration

Community assembly theory is suggested as a guiding principle for ecological restoration to help understand the mechanisms that structure biological communities and identify where restoration interventions are needed. We studied three hypotheses related to propagule limitation, stress‐dominance, and limiting similarity concepts in community assembly in a restoration field experiment with a trait‐based null model approach. The experiment aimed to assist the recovery of sand grassland on former arable land in the Kiskunság, Pannonian biogeographic region, Europe. Treatments included initial seeding of five grassland species, carbon amendment, low‐intensity mowing, and combinations in 1 m by 1 m plots in three old fields from 2003 to 2008. The distribution of 10 individual plant traits was compared to the null model and the effect of time and treatments were tested with linear mixed effect models. Initial seeding had the most visible impact on species and trait composition confirming propagule limitation in grassland recovery. Reducing nutrient availability through carbon amendment strengthened trait convergence for length of flowering as expected based on the stress‐dominance hypothesis. Mowing changed trait divergence to convergence for plant height with a strengthening impact with time, supporting our hypothesis of increasing dominance of limiting similarity with time. Our results support the idea that community assembly is simultaneously influenced by propagule limitation and multiple trait‐based processes that act through different traits. The limited impact of manipulating environmental filtering and limiting similarity compared to seeding, however, supports the view that only targeting the dispersal and environmental filters in parallel would improve restoration outcome.     

沙质草地植物功能性状对放牧、增水、氮添加及其耦合效应的响应机制

人类活动和气候变化对陆地生态系统结构和功能的影响日益明显。在中国半干旱草原区,植物功能性状对这些变化的响应机制仍不是很清楚。以科尔沁沙质草地植物群落功能性状（CWM_trait）、一年生和多年生植物平均功能性状为研究对象,开展非生长季放牧、增水、氮添加及其耦合效应的模拟控制试验,于2016年8月中旬在沙质草地开展了植物功能性状的调查及测定,主要包括植物高度、比叶面积（specific leaf area,SLA）、叶片干物质含量（leaf dry matter content,LDMC）、叶片氮含量（leaf nitrogen content,LNC）和叶片碳同位素（leaf carbon isotopes,δ¹³C）。结果表明：氮添加显著提高了CWM_height和CWM_LNC（P<0.05）,降低了CWM_LDMC（P<0.05）,同时放牧和增水的耦合效应对CWM_SLA具有显著影响（P<0.05）;放牧显著降低了一年生植物的平均高度（P<0.05）,氮添加显著提高了一年生植物的平均高度、LNC和δ¹³C （P<0.05）;氮添加显著提高了多年生植物的平均SLA、LNC和δ¹³C （P<0.05）,同时放牧和增水的耦合效应对多年生植物的平均SLA和LDMC具有显著影响（P<0.05）。主成分分析表明,放牧促进了植物群落和多年生植物SLA与LDMC、LNC和δ¹³C之间的负相关关系,增水促进了植物群落和多年生植物高度与SLA之间的正相关关系以及LDMC、LNC和δ¹³C之间的正相关关系,说明多年生植物在调控沙质草地植物群落响应外界干扰时具有较强的主导性作用。非生长季放牧、生长季禁牧有利于沙质草地的可持续发展和管理,增水能够减缓放牧压力对于草地植物的影响,氮添加有利于植物同化δ¹³C,并提高植物叶片的水分利用效率。     

Functional and performance comparisons of invasive Hieracium lepidulum and co‐occurring species in New Zealand

Abstract One of the key environmental factors affecting plant species abundance, including that of invasive exotics, is nutrient resource availability. Plant functional response to nutrient availability, and what this tells us about plant interactions with associated species, may therefore give us clues about underlying processes related to plant abundance and invasion. Patterns of abundance of Hieracium lepidulum, a European herbaceous invader of subalpine New Zealand, appear to be related to soil fertility/nutrient availability, however, abundance may be influenced by other factors including disturbance. In this study we compare H. lepidulum and field co‐occurring species for growth performance across artificial nutrient concentration gradients, for relative competitiveness and for response to disturbance, to construct a functional profile of the species. Hieracium lepidulum was found to be significantly different in its functional response to nutrient concentration gradients. Hieracium lepidulum had high relative growth rate, high yield and root plasticity in response to nutrient concentration dilution, relatively low absolute yield, low competitive yield and a positive response to clipping disturbance relative to other species. Based on overall functional response to nutrient concentration gradients, compared with other species found at the same field sites, we hypothesize that H. lepidulum invasion is not related to competitive domination. Relatively low tolerance of nutrient dilution leads us to predict that H. lepidulum is likely to be restricted from invading low fertility sites, including sites within alpine vegetation or where intact high biomass plant communities are found. Positive response to clipping disturbance and relatively high nutrient requirement, despite poor competitive performance, leads us to predict that H. lepidulum may respond to selective grazing disturbance of associated vegetation. These results are discussed in relation to published observations of H. lepidulum in New Zealand and possible tests for the hypotheses raised here.