森林管理对东北次生林植被碳密度及其分配的影响

以东北东部山区4种管理梯度下相同演替年龄的森林群落为研究对象,包括天然次生林（WB）及在其冠下人工更新红松（Pinus koraiensis）的混交林（MA）,并对MA进行透光抚育形成的择伐红松林（SK）和对SK适时疏伐形成的疏伐红松林（KT）,其管理程度依次增强。采用样地清查结合异速生长方程法量化植被碳密度（VC）及其各组分碳密度;测定多样性、针阔比等群落特征和土壤氮、磷等养分特征,探究森林管理对植被碳密度的影响。结果表明：演替先锋优势种（PI）、演替后期优势种（LT）和林下植被层（UC）的碳密度在4种管理措施间存在显著差异,其中,LT由WB的9.39 t/hm²增加到KT的107.02 t/hm²。但是,伴生种的碳密度在4种管理措施间差异不显著,其碳密度波动范围为8.41—14.89 t/hm²。VC随森林管理强度显著提升,其波动范围为96.34—135.40 t/hm²,VC年平均增长量波动范围为1.50—2.11 t hm^-2 a^-1,且在管理措施间存在显著差异。PI、LT和UC占植被总碳密度的比例在4种管理措施间存在显著差异,其中PI的占比随着上述管理措施逐渐降低,而LT的占比显著升高（由WB的14.0%提升到KT的82.2%）;植被残体与活体生物量碳密度之比以及地下与地上的生物量碳密度之比在4种管理措施间均存在显著差异,其比值的波动范围依次分别为0.05—0.13和0.24—0.30。乔木层碳密度与树种多样性存在显著负相关,而林下植被层碳密度与树种多样性呈显著正相关。并且VC与土壤氮储量、磷储量无显著相关性。这表明,在同一气候条件下,群落特征和树种组成是决定植被碳密度分异的重要因素,并且通过提升后期优势种占比的积极森林管理提升了东北次生林植被的碳密度和碳固持能力。     

面向生态系统服务的森林生态系统经营:现状、挑战与展望

森林生态系统是地球陆地生态系统的主体,它具有很高的生物生产力和生物量以及丰富的生物多样性,对全球生态系统和人类经济社会发展起着至关重要和无可替代的作用。伴随着人口的不断增长和经济社会的迅猛发展,对森林资源和森林生态系统服务的需求不断高涨,而且人类对森林资源价值的认识也发生了很大程度的改变。推进森林资源可持续经营,增加森林总量、提高森林质量、增强生态功能,已成为中国林业可持续发展乃至推进中国生态文明建设和建设美丽中国的战略任务。本文全面综述了森林生态系统经营发展历程,分析了森林生态系统经营的现状和存在问题,在此基础上,提出整合基于生态系统管理与满足现代人类福祉对森林多重需求的新的森林生态系统经营理念,面向生态系统服务的森林生态系统经营理念是未来的发展趋势。森林经营发展战略表现为:1)从单纯的森林面积数量扩张,转变到提高单位面积的森林生产力和森林质量;2)从单一追求木材生产逐步转变为多目标经营,将森林林产品单一的经营目标转变为广泛的生态、经济和社会等多目标经营;3)森林经营重点从林分水平转变为森林景观的经营,强调森林景观的时空异质性和动态变化,权衡和协同多种生态系统的服务功能,倡导森林景观的多样性和连通性,提高森林与其它土地利用模式镶嵌构成的复合景观的可持续性和稳定性,增强森林生态系统对气候变化影响的适应能力;4)森林生态系统经营将从依赖传统经验的主观决策转变为信息化、数字化和智能化的决策,发展森林生态系统经营决策支持系统和森林景观恢复与空间经营规划系统。     

森林管理的生态效应研究进展

森林管理是实现森林生产效益最大化的主要措施,是增加碳吸收以减缓气候变暖的关键手段,是调节区域水文循环的有效途径,是保护地以外实现生物多样性保护目标的重要补充。然而,追求单一生产功能的传统森林管理弱化了其他生态功能,并对森林景观结构和生物多样性产生负面影响。全球80%以上森林由于人类活动呈现不同程度退化进而影响人类福祉,森林管理需要优化以追求多维生态功能的协同共赢。当前,对于森林管理的生态效应仍有较多争论或未形成明确认识,可持续森林管理能否取得额外的气候效益仍有待确认,森林管理如何影响不同区域的水文生态功能仍未形成明确认识,不同类型森林管理或多或少、或正面或负面影响栖息地及不同种类生物多样性的强度和方向不明确。因此,森林管理的生态效应是一个值得深入探索的问题,未来需要深入量化不同管理措施对气候变化缓解、水文循环调节、生物多样性保护乃至提供其他生态功能的作用,将维持或提升生态功能及生物多样性作为可持续森林管理的一个重要目标,通过优化森林管理策略开展森林提质增效以获得最大收益。     

How do trees respond to species mixing in experimental compared to observational studies?

For decades, ecologists have investigated the effects of tree species diversity on tree productivity at different scales and with different approaches ranging from observational to experimental study designs. Using data from five European national forest inventories (16,773 plots), six tree species diversity experiments (584 plots), and six networks of comparative plots (169 plots), we tested whether tree species growth responses to species mixing are consistent and therefore transferrable between those different research approaches. Our results confirm the general positive effect of tree species mixing on species growth (16% on average) but we found no consistency in species‐specific responses to mixing between any of the three approaches, even after restricting comparisons to only those plots that shared similar mixtures compositions and forest types. These findings highlight the necessity to consider results from different research approaches when selecting species mixtures that should maximize positive forest biodiversity and functioning relationships.     

Structural characteristics and aboveground biomass of old‐growth spruce–fir stands in the eastern Carpathian mountains,Ukraine

Abstract

Temperate old‐growth forests are known to have ecological characteristics distinct from younger forests, but these have been poorly described for the remaining old‐growth Picea abies–Abies alba forests in the eastern Carpathian mountains. In addition, recent studies suggest that old‐growth forests may be more significant carbon sinks than previously recognized. This has stimulated interest in quantifying aboveground carbon stocks in primary forest systems. We investigated the structural attributes and aboveground biomass in two remnant old‐growth spruce–fir stands and compared these against a primary (never logged) mature reference stand. Our sites were located in the Gorgany Nature Reserve in western Ukraine. Overstory data were collected using variable radius plots; coarse woody debris was sampled along line intercept transects. Differences among sites were assessed using non‐parametric statistical analyses. Goodness‐of‐fit tests were used to evaluate the form of diameter distributions. The results strongly supported the hypothesis that old‐growth temperate spruce–fir forests have greater structural complexity compared to mature forests, including higher densities of large trees, more complex horizontal structure, and elevated aboveground biomass. The late‐successional sites we sampled exhibited rotated sigmoid diameter distributions; these may reflect natural disturbance dynamics. Old‐growth Carpathian spruce–fir forests store on average approximately 155–165 Mg ha^?1 of carbon in aboveground tree parts alone. This is approximately 50% higher than mature stands. Given the scarcity of primary spruce–fir forests in the Carpathian region, remaining stands have high conservation value, both as habitat for late‐successional species and as carbon storage reservoirs.     

陕北农民对退耕还林的意愿评价

为了解生态修复政策对陕北地区社会经济的影响,2007年通过参与性农户调查方法,研究退耕还林项目对陕北居民生计的影响以及由于生态项目实施引起的农民态度的变化.结果表明：农民接受退耕还林补偿政策,但只有极少数人乐意植树(8.9%)、种草(2.2%). 尽管19.1%的农户表示他们的生计受到了项目的负面影响,63.8%的农户表示支持退耕还林项目,但是高达37.2%的农户表示项目结束后会再次垦荒种粮.由此可见,退耕还林项目恢复的植被在项目结束后有可能被重新开垦为农田,该项目获得的环境成果面临被再次破坏的风险.因此,给予合理的补偿来减少农民经济损失、通过技术进步提高单位土地面积产出、通过技术培训使农村剩余劳动力转移出来是环境修复项目成功的重要保证.     

Is it getting hot in here? Adjustment of hydraulic parameters in six boreal and temperate tree species after 5 years of warming

Global temperatures (T) are rising, and for many plant species, their physiological response to this change has not been well characterized. In particular, how hydraulic parameters may change has only been examined experimentally for a few species. To address this, we measured characteristics of the hydraulic architecture of six species growing in ambient T and ambient +3.4 °C T plots in two experimentally warmed forest sites in Minnesota. These sites are at the temperate–boreal ecotone, and we measured three species from each forest type. We hypothesized that relative to boreal species, temperate species near their northern range border would increase xylem conduit diameters when grown under elevated T. We also predicted a continuum of responses among wood types, with conduit diameter increases correlating with increases in the complexity of wood structure. Finally, we predicted that increases in conduit diameter and specific hydraulic conductivity would positively affect photosynthetic rates and growth. Our results generally supported our hypotheses, and conduit diameter increased under elevated T across all species, although this pattern was driven predominantly by three species. Two of these species were temperate angiosperms, but one was a boreal conifer, contrary to predictions. We observed positive relationships between the change in specific hydraulic conductivity and both photosynthetic rate (P = 0.080) and growth (P = 0.012). Our results indicate that species differ in their ability to adjust hydraulically to increases in T. Specifically, species with more complex xylem anatomy, particularly those individuals growing near the cooler edge of their range, appeared to be better able to increase conduit diameters and specific hydraulic conductivity, which permitted increases in photosynthesis and growth. Our data support results that indicate individual's ability to physiologically adjust is related to their location within their species range, and highlight that some wood types may adjust more easily than others.     

中国东北地区阔叶红松林与兴安落叶松林的碳通量特征及其影响因子比较

北半球中高纬度的森林生态系统在全球碳循环过程中扮演着非常重要的角色。基于中国东北地区阔叶红松林与兴安落叶松林2007年和2008年2a生长季的涡度相关通量资料及气象观测资料,比较分析了两类生态系统的碳通量特征及其环境控制因子。结果表明:研究期间,阔叶红松林与兴安落叶松林都表现为碳吸收,强度分别为199gCm-2(阔叶红松林2a生长季平均值)与49gCm-2(兴安落叶松林2008年生长季);阔叶红松林碳吸收强度在生长季的大部分时段都大于兴安落叶松林。半小时尺度上,两类生态系统的呼吸作用均与10cm土壤温度呈显著的指数相关,兴安落叶松林生态系统呼吸的温度敏感性(Q10=3.44)显著大于阔叶红松林(Q10=1.90);日尺度上,阔叶红松林与兴安落叶松林碳释放/吸收的转变临界温度为10℃左右。研究期间,兴安落叶松林生态系统的水分利用效率高于阔叶红松林生态系统。