林窗模型的几个基本问题的研究Ⅱ.模拟样地个数的效应

Plot number can deeply affect the result of forest gap model simulation, but which has been paid little attention and investigation. This study takes Broad-leaved Korean pine (Pinus koraiensis) forests, in Mt. Changbai of Northeastern China, for instance, and applies forest gap model NEWCOP to investigate the effects of different plot number on the result of forest gap model simulation. Our study shows that plot number can affect forest species composition, which indicates a decrease of forest community variability index with increasing simulation plot number and a trend to 0 for the index after the plot number reaching some value. Based on the result mentioned above, we conclude that the smallest area of stand for presenting the characteristics of broad-leaved korean pine forest community is 38400 ha.

土地利用变化和林业活动碳贮量变化测定与监测中的方法学问题

土地利用、土地利用变化和林业 (L U L U CF)活动是引起大气温室气体浓度上升的主要因素之一 ,评价、监测 L UL UCF活动的碳源 /汇功能还存在很大的不确定性。近年来我国在该方面开展了一些研究和测定工作 ,但研究力度还远远不够 ,研究方法还存在一些问题。针对 L U L UCF活动对碳贮量影响的测定和监测中的碳库选择、监测间隔期、样地数量以及土壤容重影响和校正等有关方法学问题进行了阐述 ,以期为我国该方面的研究和监测有所裨益。

提高林业局级森林资源监测精度建议

1990年,省森工总局要求各林业局建立林业局级森林资源监测样地体系,已有8年时间.截止目前已有半数以上的林业局完成7初设任务。在整个工作过程中,始终令笔者关注的一个问题是资源现状的抽样精度如何? 为此,笔者列举牡丹江森工林区的两个林业局1996年复测数据加以考察。

基于数理统计的苗木调查方法研究

苗木调查以数理统计为基础,以系统抽样为主,运用正态分布原理,分析调查数据。本文通过实例介绍如何确定样地数量及苗木检测株数及苗木的产量精度和质量精度的方法步骤,并说明苗木调查与苗木质量检测的区别。

Effects of Grazing Exclusion on Plant Productivity and Soil Carbon, Nitrogen Storage in Alpine Meadows in Northern Tibet, China

Grazing exclusion is widely adopted in restoring degraded alpine grasslands on the Qinghai-Tibetan Plateau. However, its effectiveness remains poorly understood. In this study, we investigated the effects of grazing exclusion on plant productivity, species diversity and soil organic carbon （SOC） and soil total nitrogen （STN） storage along a transect spanning from east to west of alpine meadows in northern Tibet, China. After six years of grazing exclusion, plant cover, aboveground biomass （AGB）, belowground biomass （BGB）, SOC and STN were increased, but species diversity indices declined. The enhancement of AGB and SOC caused by grazing exclusion was correlated positively with mean annual precipitation （MAP）. Grazing exclusion led to remarkable biomass increase of sedge species, especially Kobresia pygmaea, whereas decrease of biomass in forbs and no obvious change in grass, leguminous and noxious species. Root biomass was concentrated in the near surface layer （10 cm） after grazing exclusion. The effects of grazing exclusion on SOC storage were confined to shallow soil layer in sites with lower MAP. It is indicated that grazing exclusion is an effective measure to increase forage production and enhance soil carbon sequestration in the studied region. The effect is more efficient in sites with higher precipitation. However, the results revealed a tradeoff between vegetation restoration and ecological biodiversity. Therefore, carbon pools recover more quickly than plant biodiversity in the alpine meadows. We suggest that grazing exclusion should be combined with other measures to reconcile grassland restoration and biodiversitv conservation.

The Analysis of Coseismic Response of 4-component Borehole Strainmeters with High Sampling Rate

In this paper,we adopt the observation data of two 10Hz YRY 4-component borehole strainmeters and one 100Hz FBS-3B broadband seismometer to study the responses of their observations to the April 11,2012 MW8. 6 earthquake off the west coast of northern Sumatra,and compare the response characteristics during the coseismic stage after preprocessing of the data. We analyze the spectrum's dynamic process during the coseismic stage with the S transformation method,and discuss the spectrum's details in different seismic phases. The S transformation results of the data of seismometer and borehole strainmeter at the same station show that the coseismic spectrum evolution of the two kinds of observation are similar to each other and can be cross-referenced in indentifying the wave signals,which proves that the borehole strainmeter measurements at high frequencies are reliable.

草地资源监测样地布设方法探讨--以承德御道口牧场管理区为例

草地资源监测工作有助于及时掌握草地资源的动态变化,为政府决策和制定草地修复方案和保护措施提供依据,以实际工作过程中积累的相关经验为基础,对草地资源监测工作中样地数量的确定以及样地布设方式进行了归纳总结;以御道口牧场草地资源监测为实例进行了相关方法的应用,结果表明:采用简单随机抽样法进行样地数量测算的监测区更适合以机械均匀布点法进行样地的布设;采用典型抽样法进行样地数量测算的监测区则以典型随机布点法或线路调查布点法进行样地布设更能体现其优势性。