川西北不同沙化程度草地植物功能性状及其驱动因子

摘要

Plant functional traits, defined as morpho-physio-phenological traits which impact fitness indirectly via their effects on plant growth, reproduction and survival, which have been a hot topic of ecological and plant research in recent years.To elucidate the driving factors behind plant functional traits, especially in desertification grassland, we explored how variation in topography and soil characteristics affected plant functional traits in different desertification grassland including non-desertification grassland, light-desertification grassland, middle-desertification grassland and heavy-desertification grassland in Northwest Sichuan.The results showed that: (1) plant community succession presented the pattern of "hygrophyte-mesophyte-xerophyte" with the aggravation of desertification degree.(2) The plant height and coverage decreased with the aggravation of desertification degree, and species richness and dominant species changed greatly.Moreover, leaf thickness (LT), specific leaf area (SLA), leaf density (LD), specific root length (SRL), root density (RD), leaf nitrogen (LN), leaf phosphorus (LP), root nitrogen (RN), root phosphorus (RP) decreased with the aggravation of desertification degree.(3) Non-desertification grassland had the highest plant functional traits with the higher efficiency of resource utilization.SLA had the higher variation (250.53), and LT had the lower variation (9.56), while RD, SLA, RN, RP, LD had the larger variation, then LT had a higher plant functional traits conservation.(4) RN had a strong correlation with plant functional traits, and SLA had a negative correlation with LD and positive correlation with RN.SRL had a significantly negative correlation with LN (P<0.01), and negative correlation with RN (P<0.05).(5) Stepwise regression analysis showed that plant functional traits had strong correlations with soil factors, which we can determine plant functional traits by soil factors.(6) Based on the grey correlation degree analysis, we can conclude that elevation was the most influential topographic factor on SLA, SRL, RD, LN, RP;while LT, LD, RN was affected by slope aspect;and LP was affected by slope position.Redundancy analysis showed that elevation and soil pH were the main driving factors to affect plant functional traits.%以川西北不同沙化程度草地典型群落为研究对象,分析了不同沙化程度草地(未沙化草地、轻度沙化草地、中度沙化草地、重度沙化草地)植物功能性状之间的关系及其与地形和土壤因子的相关性,并对不同沙化程度草地植物功能性状进行了比较.结果发现:(1)从未沙化草地到重度沙化草地变化过程中,植物群落呈现出"湿生-中生-旱生"的演替格局,植物群落高度、盖度和物种丰富度随着沙化程度加剧而逐渐降低.(2)叶厚度(LT)、比叶面积(SLA)、叶组织密度(LD)、比根长(SRL)、根组织密度(RD)、叶氮含量(LN)、叶磷含量(LP)、根氮含量(RN)、根磷含量(RP)随着草地沙化程度的增加而降低.(3)未沙化地草本植物的植物功能性状最大,对资源的利用效率很高,其中SLA极差值最大(250.53),LT极差值最小(9.56),RD、SLA、RN、RP和LD具有较高的变异性,LT具有较低的变异系数,其保守性最高.(4)RN与所有的叶性状均有不同程度的相关性;SLA与LD呈极显著负相关关系,与RN呈显著正相关关系;SRL与LN呈极显著负相关关系,与RN呈显著负相关关系;LN与RN呈显著正相关关系.(5)逐步回归分析表明,功能性状与土壤因子间具有一定明显的相关性,可以通过土壤因子的定量分析来确定地上植物功能性状的变化趋势及可变范围.(6)灰色关联度分析发现,SLA、SRL、RD、LN、RP受海拔的影响较大,LT、LD、RN受坡向的影响最大,坡位对LP影响最大.研究表明,地形因子中海拔对植物功能性状影响较大,土壤因子中pH值对植物功能性状影响较大.