子午岭辽东栎种群更新机制研究

【作者】 郭华；

【导师】 王孝安；

【作者基本信息】 陕西师范大学 ， 生态学， 2011， 博士

【摘要】 黄土高原子午岭林区的人工林存在物种组成单一、自然更新差、乡土树种难以自然侵入等生态学问题,影响着该地区植被的正常恢复和物种多样性的维持以及森林生态系统服务功能。如何促进乡土树种向人工林入侵,以改善人工林群落结构,加速其演替进程,是植被恢复工作亟待解决的课题。因此深入研究乡土树种的更新机制,尤其是在人工林下定居过程中的限制因素则显得必要而迫切。辽东栎(Quercus wutaishanica)是暖温带落叶阔叶林地带性植被类型的主要树种,作为子午岭林区的主要乡土树种和气候顶极群落的建群种,其幼苗的补充更新影响着森林群落的结构及物种组成,对该地区的人工林改造意义重大。本研究将群落学调查、野外控制性播种实验和室内栽培实验相结合,通过对幼苗空间分布、生长状况及微生境指标的监测,对辽东栎在不同生境(油松(Pinus tabulaeformis)林、辽东栎林、撂荒地)中的幼苗补充过程展开研究,旨在确定其在不同生境中的补充限制类型,筛选幼苗定居过程中的关键生态因子,进而揭示辽东栎在本地区的更新机理,探讨黄土高原人工林向气候顶极群落演替的可能性,从而为“补充限制理论”提供新的实验证据,为黄土高原人工林的合理化改造提供科学理论依据。本文围绕辽东栎种群的更新问题,对不同生境中辽东栎实生幼苗及微生境的空间异质性、幼苗在不同生境及不同生态因子作用下的定居过程、生物量分配、生化它感作用等进行了研究,得到以下结果：1)辽东栎幼苗为子午岭林区乔木更新层中的优势物种。通过对子午岭林区植被的全面普查,发现在本地区所有乔木树种中,辽东栎幼苗出现频率较高,在全区各种森林群落中均有分布,但其密度在不同群落中存在较大变异性。2)在辽东栎林和人工油松林林下,辽东栎幼苗空间分布格局均呈聚集型,但聚集尺度和相关微生境因子存在较大差异。应用变异函数分析辽东栎林及人工油松林中的辽东栎幼苗空间分布数据,结果显示：在辽东栎林中,幼苗在1-5.94 m范围内存在空间自相关性;人工油松林中,幼苗在1-1.94m范围内存在空间自相关性。应用前向选择法、DCCA排序等方法筛选14个环境因子,结果表明：栎林下,对辽东栎幼苗空间分布贡献较大的为枯落物厚度(LT)、土壤速效钾(K)含量、土壤温度(T)；油松林下,对辽东栎幼苗空间分布贡献较大的为土壤湿度(H)、土壤酸碱度(pH)、土壤有机质(O)。3)通过对野外播种实验建立的辽东栎幼苗同生群为期三年的监测,编制了动态生命表并进行了生存分析。结果表明：①在三种生境(辽东栎林、人工油松林、灌草丛)中,辽东栎幼苗存活曲线大致呈Deevey-Ⅱ型,幼苗在郁闭的森林生境中存活率显著高于灌草丛群落。②森林生境中,辽东栎幼苗在出苗后第三年春季出现死亡高峰期,幼苗平均生命期望值为23个月。③灌草丛生境中,辽东栎幼苗在出苗后第二年春季出现死亡高峰期,幼苗平均生命期望值为15个月。4)在三种典型生境(辽东栎林、人工油松林、灌草丛)中,设置3因素(种子、干扰、遮荫)两水平的播种实验。结果表明：①辽东栎种群的补充更新受到了种子可用性和微生境可用性的双重限制；②郁闭林冠下,枯落物是导致微生境限制的主要因素之,灌木对辽东栎幼苗的补充无显著影响；③灌草丛生境中各种处理方式均不能增加幼苗的补充量,表明辽东栎无法在开阔生境(强光照、干旱)中定居。④根据幼苗生长指标判断,在三种生境中,人工油松林林下是辽东栎幼苗早期生长的最佳场所。5)室内栽培实验显示：①在第一生长季中,辽东栎根系的生长分为两个主要阶段,播种后60-90 d内是其快速生长期。②子叶干重随幼苗发育持续下降,出苗90 d后,子叶干重不再下降；③叶干重在出苗后持续增长,而茎干重在出苗90 d后不再增长。④光合作用固定的能量在出苗后第一年8、9月份开始向地下根系转移。⑤枯落物厚度对辽东栎出苗量产生显著影响,3 cm枯落物覆盖厚度为最佳条件；5 cm厚度将对出苗量产生明显抑制作用,在此条件下最终成活幼苗的子叶干重明显下降,可能对后期幼苗定居过程产生不利影响。⑥高浓度(1：10)的油松林林下枯落物浸提液对辽东栎幼苗建成有不利影响,主要表现在对幼苗高度和地上、地下生物量的抑制效应,但对整体出苗量并无显著影响。综上所述,辽东栎作为子午岭林区乡土树种中的优势物种,其实生幼苗具备在人工油松林等郁闭森林生境中成功定居的能力,且在油松林下表现出了较好的生长状态。人工油松林生境中,辽东栎种群的更新受到种子和微生境可用性的双重限制,缺乏种源和较厚的枯落层是造成其在此生境中更新困难的主要限制因素。建议在人工油松林改造时,对林下枯落层进行扰动,并保留林中灌木层和下木层保持生境具备一定的遮荫条件,以促进辽东栎种群的实生更新。更多还原

【Abstract】 The ecosystem function of plantation in Mt. Ziwuling, the Loess Plateau, was impaired because of lower species diversity, native woody species colonization obstacle, and recruitment handicap. How to accelerate the native woody species colonizing towards plantation in order to improve community structure and increase succession, was a very important project in restoration ecology. So, it’s necessary to study the recruitment of native woody species, especially the limitation factors in establishmnet. Liaodong oak (Quercus wutaishanica) is the main native woody species and the dominant species of the climatic climax community in Mt. Ziwuling. In this study, three methods, including community investigation, field seeds sowing experiment and lab planting experiment, were used to research the seedling recruitment of Liaodong oak in three typical habites (Pinus tabulaeformis plantation, Liaodong oak forest, and grassland) by supervising the seedling growth and microsite factors. The main aims were to confirm the recruitment limitation type and to select the key ecological limitation factors during seedlings establishment. Moreover, the recruitment mechanism of Liaodong oak population will be unclosed, and the probability of plantation successing to climate climax community was discussed. This study will supply the new proof to recruitment limitation theory, and will be the gist of the plantation restoration in the Loess Plateau.In this paper, the biomass allocation in seedling development, the seedling and microsite spatial heterogeneity, and the recruitment of seedlings in different ecological factors and habitats were researched, and the main results of were summed up as follows.1. The seedling of Liaodong oak was the dominant species in the woody seedlings layer in the Ziwuling forest region. The vegetation in Mt. Ziwuling forest region was investgated comprehensively, and it was observed that the Liaodong oak seedlings distributed in all of the forest communities in this region and had higher frequency, but the density was largely variant in different community.2. The Liaodong oak seedlings spatial pattern were both the clumped type in conifer plantation and oak forest, but there were significant difference in clumped scale and correlated microsite factors. Semivariogram analysis showed that, in oak forest, the data of seedlings was spatial autocorrelated in 1-5.94 m range, and the data of seedlings was spatial autocorrelated in 1-1.94 m range in the conifer forest. Using forward selection method and DCCA, some main factors were selected. In oak forest, they were litter thickness (LT), soil available kalium (K) and soil temperature (T). In conifer forest, they were soil humidity (H), soil pH (pH) and soil organism (O).3. The dynamic life table was builted according to the Liaodong oak seedling growth data in three years. The results showed that:1) The survival curve of the seedlings cohort in three habits tended to be the type Deevey -Ⅱ. The seedlings survival probability in closed forest canopy was higher than it in opened grassland.2) In the forests, the seedlings death climax presented in the spring of the third year after seedling emergence, and the expected life span was 23 monthes.3) In the grassland, the seedlings death climax presented in the spring of the second year after seedling emergence, and the expected life span was 15 monthes.4. The relative influence of seed and microsite availability in the seedling emergence and recruitment of Liaodong oak was examined by seed sowing experiments, which were performed in three typical stands (conifer plantation, Liaodong oak forest and grassland). A seed augmentation experiment was performed in an oak forest and a conifer plantation, and a seed introduction experiment was carried out in the grassland. Three main factors were considered:seed addition, disturbance and shrub cover. The seedling number and growth in every plot were recorded continuously over 3 years. GLM multivariate was used to analyze the relationships between seedling emergence-recruitment and the explanatory variables in every stand. The results showed that:1) The recruitment of Liaodong oak was limited by seed and microsite availability in this region.2) In closed forest, litter was one of the factors leading to microsite limitation, and shrub cover did not affect the recruitment of Liaodong oak in the three stands.3) In the grassland, no treatments improved recruitment, indicating that the grassland was not suitable for seedling recruitment because of intense light and soil drought.4) In the conifer forest, more recruited seedlings, and lower herbivory on seedling leaves, as well as thicker stem basal diameters, indicated that the P. tabulaeformis plantation was safer for Liaodong oak seedling establishment.5. The results of lab planting experiments showed that:1) There were two stage of Liaodong oak seedlings root developing. The first rapid stage was present in 60 or 90 days after seeds sowing.2) The dry weight of cotyledon was still decreased in whole seedling growth progress, but it was stoped after seedlings emergence 90 days.3) The leaves dry weight continuously increased, but the stem dry weight was stop increasing after seedlings emergence 90 days.4) The energy from photosynthesis was translated to roots in Augest or September, so the damage frome animal or insect would negatively affected the seedling survival.5) The litter thickness was significant affected the oak seedling emergence, and 3 cm litter thickness was the best suit condition. In 5 cm litter thichness, the dry weight of cotyledon, which still keeped in seedlings, was decreased significantly, and it would be disbennifit for the seedling establishment in future.6) The higher concentration conifer litter extracted liquid (1:10) was disadvantage for oak seedling establishment. It constrained the seedling height and the total dry weight, but was not decreased the seedlings emergence.Drawing a conclusion, Liaodong oak had the ability of establishing in conifer forest, and the seedling growthed well in the environment. The Liaodong oak population recruitment will be limited by seed and mirosite availability in conifer plantation. The limited factor for recruitment was seed source and litter layer in community. The lower light intensity in closed forest would not negatively affect the seedling in early development. So, during the P. tabulaeformis plantation alteration, disturbing the litter layer and reserving the shrubs and underwood to keep shady will be benefit for Liaodong oak regeneration by seeds.更多还原