荒漠植物功能性状及其多样性对土壤水盐变化的响应

Responses of plant functional trait and diversity to soil water and salinity changes in desert ecosystem

植物功能性状及其多样性对环境变化的响应研究有助于揭示极端环境下植物适应策略和群落构建机制。通过实地调查和实验分析,研究艾比湖荒漠植物形态、生理和化学等8个功能性状的特征,并从多维性状和一维性状角度揭示功能多样性对土壤水分和盐分变化的响应规律。结果表明:高水盐环境下(SW1),(1)群落加权株高、叶绿素含量(SPAD)及叶片碳(C)和钙(Ca)含量显著高于低水盐环境,叶片氮(N)、磷(P)、硫(S)含量在不同水盐环境间无显著差异。(2)SW1环境下,沿乔木-小乔木-灌木-草本层次,上层生活型植物性状值普遍高于下层植物,其中灌木叶片仅N、钾(K)含量显著高于草本;沿该生活型层次植物性状呈趋同变化。(3)低水盐环境下(SW2),乔木叶片性状差异特征与SW1相似;小乔木叶片C、N含量分别显著高于和低于灌木及草本;相比于草本,灌木SPAD、S含量显著高,K含量显著低,株高、C、N、P含量差异不显著;SW2环境下各生活型植物性状呈趋同变化。(4)SW1环境下多维功能丰富度、功能离散度显著高于SW2环境,但均匀度无显著差异。(5)一维功能均匀度在不同水盐环境间均无显著差异,但化学性状的均匀度总体高于植物株高;高水盐环境下叶片N、S和Ca的功能分异指数显著高于低水盐环境。研究为掌握胁迫环境下的植物适应策略和荒漠植被恢复提供参考。

Exploring the response of plant functional trait to environmental variations is essential to elucidate the adaptation mechanism and community assembly of desert plants under extreme environmental conditions, and more importantly to formulate strategies to protect and restore desert ecosystem. However, previous studies are mostly large scale, and only a few studies have focused on the effects of soil water and salinity on desert plant functional trait and diversity at fine scale. It is known that, even at fine scales, environmental variables (e.g., soil variables) can actually be heterogeneous and affect plant. Therefore, in the present study, we aimed to analyze (1) how morphological, physiological, and chemical functional traits of desert plant, and functional richness, evenness, and dispersion indexes respond to varied soil water and salinity and (2) what community assembly process did functional diversity revealed in different soil water and salinity environment? Three transects were set at 5-km intervals perpendicular to the northern bank of the Aqikesu River in the Ebinur Lake Wetland Nature Reserve (ELWNR). At each transect, the soil gradually changed from saline to sandy soil with the increase in distance from the river. Ten to twelve plots (10×10 m2) were set at an interval of 500 m in each transect. A total of 32 plots were set across the three transects. The geographic data (longitude, latitude, and altitude), number of species, plant abundance (number of individuals of each species), and height of each individual sampled in each plot were recorded. The chlorophyll content (SPAD) was measured by SPAD502, and soil volumetric water content (SVWC) at a depth of 12 cm was measured by time domain reflectometry before sampling. The leaf and soil samples were then collected for further investigation. Based on the investigation and analysis, responses of one morphological (height), one physiological (SPAD) and six chemical functional traits (leaf carbon (C), nitrogen (N), phosphorus (P), sulfur (S), potassium (K), and calcium (Ca) content), and response of multidimensional and single dimensional functional diversities to soil water and salinity were explored. The results showed the following.(1) The community weighted mean height, SPAD, and leaf C and Ca content in high soil water and salinity sites (SW1) were significantly higher than those in low soil water and salinity sites (SW2). The leaf N, P, and S content had no significant differences across the two sites.(2) In SW1 sites, the plant functional trait differences generally decreased along the tree-small tree-shrub-herb life form level, with only leaf N and K content exhibiting significant difference between shrub and herb. Furthermore, plant functional trait showed convergence along the life form level.(3) In SW2 sites, functional trait differences in trees were similar to those in the SW1;the leaf C and N content were significantly higher than those in shrubs and herbs. Furthermore, the SPAD and leaf S content of shrubs were significantly higher than those in herbs, whilst, the leaf K content of shrubs was lower than that in herbs. The height, and leaf C, N, and P content exhibited no significant differences between shrubs and herbs. The plant functional traits among life forms in SW2 site presented a trend of convergence.(4) The multidimensional functional richness (FAD2) and functional divergence (Rao) in SW1 sites were higher than those in SW2 sites, whilst, the functional evenness showed no difference.(5) All single dimensional functional evenness showed no difference between high and low soil water content and salinity;however, functional evenness of chemical trait was generally higher than that of plant height. Furthermore, functional logarithmic variance (FDvar) of leaf N, S, and Ca in SW1 was significantly higher than that of SW2. The study provides references to understand the adaption mechanism of plants subjected to extreme environments and to recover desert plants.