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植物功能性状是植物在形态学、生理学以及物候学等方面的综合特征,可以表现植物生态学策略,决定植物对环境的反馈,进而影响物种共存规律[1]和生态系统特性[2]。目前,叶片功能性状的研究主要集中在成年植株功能性状之间的关系[3]以及不同植物种的叶片功能性状沿不同环境梯度的变化上[4]。近年研究表明种内性状的变异在乔木物种中占据重要地位[5-6],并且其通常取决于环境[7]和空间尺度的长度[8]。木本植物叶片性状个体发育变化情况可以反映植物的生存策略,植物个体可根据自身生活史策略需要改变叶片性状以适应植株尺寸大小[9-10]。植物比叶面积(specific leaf area, SLA)直接决定植物种群的表现数量(例如,生长、繁殖以及死亡率)、耐阴性以及其生态策略[11-12]。植株最大高度可预测外界资源的变化情况,尤其对光的变化反应敏感[13]。近年来,基于性状的研究方法已扩展至认识和预测群落和生态系统结构、动态以及功能等领域[14-17]。土壤元素是森林群落中重要的非生物因子,通过塑造叶片性状间接影响植物生长与抗逆性,进而驱动植物生态对策的变化[18]。有研究表明,林冠层和亚林冠层叶性状的趋异会随着土壤元素含量的增高而增大。与此相反,低土壤元素含量可能会通过限制林窗内更新植物个体的最大生长率来阻碍森林群落更新生态位的趋异性,这同时也限制了共存物种(叶)性状趋异的潜在可能性[20]。相较土壤元素的绝对含量,其有效性更能直接影响植物功能性状,其中,土壤有效磷含量就在很大程度上决定了区域[18]及全球尺度上的[19]SLA数值大小。
干热河谷属生态脆弱区,土壤侵蚀严重[21-23],南亚热带立体气候使该区域高温、干旱、蒸发量大。该区域植物物种虽较为稀少,但却分布着有“巴蜀三宝”之称的攀枝花苏铁(Cycas panzhihuaensis)种群,位于攀枝花市西区的四川攀枝花苏铁国家级自然保护区保护中心聚集着欧亚大陆自然分布最北且株数最多的天然苏铁林。国内干热河谷森林群落主要分布在云南和四川两省[24],目前对干热河谷森林群落的研究主要集中在云南省干热河谷群落结构[25]、植物生物量[26]、生物多样性[27-28]、植物对土壤养分和水分的利用[29]等方面。针对功能性状方面的研究还较鲜见,而功能性状与土壤元素关系的研究更是尚未起步。通过分析攀枝花苏铁种群主要功能性状(叶面积、比叶面积、植株高度、叶片干重)的空间异质性及其与土壤有效养分的关系,以期较为全面地掌握干热河谷次生稀树灌木林内攀枝花苏铁种群主要功能性状现状及其变化规律,旨在为干热河谷稀树灌木林乃至整个干热河谷生态系统的演替和生物多样性维持机制的研究奠定植物功能性状方面的基础。
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干热河谷次生稀树灌木林攀枝花苏铁种群LA、LDMC、SLA以及取样地海拔高度、AK以及pH等存在显著差异,但攀枝花苏铁种群最大植株高度(PHMAX)、取样地AN及AK并无显著差异(见表1),这可能由干热河谷次生稀树灌木林尚处于该区域植物群落演替初期阶段导致,较低的群落郁闭度使群落内攀枝花苏铁种群各植株尚未达到光胁迫而产生垂直结构的生态位分化,从而导致植株高度差异性较小。但LA、LDMC、SLA的显著差异不仅说明攀枝花苏铁种群所处微环境的异质性程度较高,也间接表明干热河谷次生稀树灌木林正向高阶演替阶段(干热河谷次生常绿针阔叶混交林)演替。
项目
Items干热河谷次生稀树灌木林
Secondary savanna shrub forest of the dry-hot valleyPHMAX X[14]2 = 3.453; P = 0.178 > 0.05 LA X[14]2 = 85.206; P = 0.001 < 0.01 LDMC X[14]2 = 112.692; P = 0.000 < 0.01 SLA X[14]2 = 54.482; P = 0.000 < 0.01 Al X[14]2 = 79.000; P = 0.006 < 0.01 AN X[14]2 = 23.168; P = 0.081 > 0.05 AP X[14]2 = 12.419; P = 0.647 > 0.05 AK X[14]2 = 29.238; P = 0.015 < 0.05 pH X[14]2 = 36.756; P = 0.001 < 0.01 Table 1. Comparison of main functional traits and soil available nutrients of Cycas panzhihuaensis among 1~15 plots in secondary savanna shrub forest of the dry-hot valley1)
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干热河谷次生稀树灌木林攀枝花苏铁种群取样样方分布特点表现为对土壤环境条件的偏好不尽相同(见图1-A)。取样样方数对AN、AP、AK及pH的响应程度均较大,其中,以AK和pH对影响程度最大,但海拔高度(Al)的影响相对较小,这说明干热河谷次生稀树灌木林群落内生态位分化尚未形成,也证明了群落内土壤有效养分存在异质性(见表1)。攀枝花苏铁种群各主要功能性状间和各土壤有效养分间均呈现显著的相关作用(表2),LA、SLA及LDMC等功能性状与AN、AP、AK均呈较为微弱的正相关(图1-B, 表2),表明AN、AP、AK对LA、SLA及LDMC均存在不同程度地影响,也说明土壤有效养分是影响攀枝花苏铁种群主要功能性状分异的关键因子。
Figure 1. Ordination diagrams for RDA of main functional traits of Cycas panzhihuaensis, available soil nutrients and each plots (Fig.1-A indicates environmental factors and each plots; Fig.1-B indicates main functional traits of Cycas panzhihuaensis and environmental factors. AN stands for soil available nitrogen, AP stands for soil available phosphorus, AK stands for soil available potassium, pH stands for soil pondus Hydrogenii, Al represents altitude, LA represents leaf area, SLA represents specific leaf area, LDMC represents leaf dry matter content, PHMAX represents plant maximum height.)
Al PHMAX SLA LDMC LA pH AK AP AN Al − −0.071 −0.142 0.030 −0.134 0.271* 0.026 −0.041 0.039 PHMAX −0.071 − 0.022 0.048 0.520** 0.020 0.088 0.131 0.074 SLA −0.142 0.022 − −0.560** 0.312** −0.089 0.001 0.005 0.022 LDMC 0.030 0.048 −0.560** − 0.573** −0.018 0.007 0.013 0.008 LA −0.134 0.520** 0.312** 0.573** − −0.070 0.038 0.037 0.006 pH 0.271* 0.020 −0.089 −0.018 −0.070 − 0.137 0.043 0.173 AK 0.026 0.088 0.001 0.007 0.038 0.137 − 0.844** 0.909** AP −0.041 0.131 0.005 0.013 0.037 0.043 0.844** − 0.892** AN 0.039 0.074 0.022 0.008 0.006 0.173 0.909** 0.892** − Table 2. Partial correlation analysis of each main functional traits and soil nutrients of Cycas panzhihuaensis in secondary savanna shrub forest of the arid-hot valley1)
Response of Main Functional Traits of Cycas panzhihuaensis to Soil Available Nutrients: A Case Study of Cycas panzhihuaensis National Nature Reserve in Sichuan Province
doi: 10.12172/202211230002
- Received Date: 2022-11-23
- Available Online: 2023-04-07
- Publish Date: 2023-10-25
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Key words:
- Functional traits /
- Soil available nutrients /
- Cycas panzhihuaensis population /
- Secondary savanna shrub forest in dry-hot valley /
- Cycas panzhihuaensis National Nature Reserve
Abstract: In order to understand the distribution characteristics of main functional traits of Cycas panzhihuaensis and its response to soil available nutrients, 15 permanent sample plots (10 m × 10 m) were established in the secondary savanna shrub forest of dry-hot valley in Panzhihua Cycas panzhihuaensis National Nature Reserve, Sichuan Province. The main functional traits like plant maximum height (PHMAX), area of a leaf (LA), specific leaf area (SLA), and leaf dry-matter content (LDMC) and soil available nutrients like available nitrogen (AN), available phosphorus (AP), and available potassium (AK) of Cycas panzhihuaensis population in the sample plots were collected, and the distribution of main functional traits and soil available nutrients among plots and their relationships were analyzed by Kruskal-Wallis test and multivariate statistical. The results showed that there were significant difference in LA, LDMC, SLA, Al, AK, and pH among different plots, but not in PHMAX, AN, and AP. Soil available potassium (AK) and pH had the greatest influence on the distribution of Cycas Panzhihua population. There was a significant correlation between the main functional traits of Cycas panzhihuaensis population and the available nutrients in soil, and the functional traits such as LA, SLA and LDMC were weakly positively correlated with AN, AP and AK. The differentiation of main functional traits of Cycas panzhihuaensis population was due to the heterogeneous distribution of soil available nutrients. The common restriction mechanism of AN, AP and AK was the main survival pressure of Cycas panzhihuaensis population at local small scale in the forest community during current succession stage. However, with the progress of forest succession, AN and AP might play more important roles than AK on growth and development of Cycas panzhihuaensis.