与物种多样性有关的长白落叶松人工林生物量

Biomass of Larix olgensis plantations based on species diversity analyses in Heilongjiang,China

对不同龄组长白落叶松(Larix olgensis)人工林群落的物种多样性和生物量及二者关系研究分析。结果表明:1)随林龄增大,群落物种组成结构和多样性特征发生了很大变化。物种更迭现象明显,春榆等阔叶树重要值上升,长白落叶松优势地位逐渐下降,植被类型向针阔混交林演替。群落Sorensen相似性指数降低,Shannon-Winner多样性指数呈"S"型曲线增长,Pielou均匀度指数呈反"S"型曲线下降,Margalef丰富度指数呈单峰曲线增长趋势;2)随林龄增大,群落生物量"S"型曲线增长趋势明显,分配序列为:乔木层>木质物残体层>灌木层>草本层,占群落生物量比例分别为82.41%、15.10%、1.69%和0.81%。长白落叶松生物量占据主导地位,但所占比例持续下降,属于衰退型种群,而春榆等阔叶树比例上升。林下植被层中,草本的主导地位逐渐丧失,灌木取而代之,生物量所占比例明显升高。地表木质物残体生物量比例缓慢下降;3)群落中物种多样性测度指标与生物量之间单调线性增长的关系明显,Shannon多样性指数较之Pielou均匀度指数更适合作群落生物量度量指标,生物量与Margalef丰富度指数无明显相关性。

Understanding the relationship between community diversity and biomass is important for restoring the structure of a community. Larix olgensisis an important forest type in northeastern China and plantations of Larix olgensiscover largeareas, but a strong need exists for studies comparing species diversity and productivity in this community. The relationships between diversity and productivity are difficult to measure because the complex, dynamic situations in plantations make diversity indices and the characteristics of the various layers of biomass of different age groups and community structures difficult to analyze. Our objective was to study the indicatorsof diversity and biomass as well asto study the interactions between diversity and biomass in L. olgensis plantations, at a forest farm in Yichun, Heilongjiang Province, China. We calculated community diversity by several indices such as Sorensen＇s similarity, Shannon-Wiener, Pielou evenness and Margalef richness indices. Sampling harvest and statistical estimation methods were used to analyze the biomass of three layers： arbor （L. olgensis and other trees）, understory vegetation （shrubs and herbs）, and woody debris （fine woody debris, coarse woody debris and residual woody debris piles） in ten L. olgensis forest stands. These stands included areas with different successional stages such as immature, young, mid-aged, near-mature and mature; two rectangular plots were randomly established in each stand for the collection of survey data. All survey data from these plots were collected simultaneously. Space-for-time substitution, community structure, species diversity, and biomass distribution were all analyzed independently in stands of different ages; in addition, dynamics trends of these forest characteristics were simulated with allometric regression. Our research indicated that over time, 1） species composition and biodiversity characteristics of the community changed significantly. The importance value of Ulmus pumila L. initially increased rapidly and the dominance of L. olgensis declined, indicating the community was in the process of secondary succession from coniferous to conifer-broadleaf forest. Sorensen similarity index declined, the Shannon-Wiener index showed an ＂S＂ curve growth trend, but the Pielouindex showed reverse ＂S＂ curve with a downward trend, and the Margalef index showed a＂hump-shaped＂ trend. 2） Biomass of the community showed an ＂S＂ curve growth trend with the arbor,woody debris, shrub and herb layers contributing 82.41%, 15.10%,1.69% and 0.81% of the biomass, respectively.Initially, L. olgensis dominated in plantations, but the proportion of L. olgensis within the community continued to decline over time until the population itself declined. The shrub layer will replace the herb layer＇s dominant position in the understory layer and the proportion of woody debris slowly declined. 3） Analysis results showed that the diversity indices were linearly correlated to biomass; the Shannon-Wiener index was better suited than the Pielou index for measuring the regression; the relationship between the Margalef index and biomass was not clear. In this paper, we analyzed internal and external relationships of species diversity and biomass of L. olgensis plantations thoroughly at different stages. In particular, under specific habitat conditions,both diversity and biomass were undergoing dynamic changes, which had great significance in the use of spatial resources and to the sustainable health and stable development of the community. Thus, we concluded possible curvilinear relations of species diversity and biomass would supply scientific evidence of forest ecosystem recovery and restructuring as well as provide useful information related to plantation management.