Changes in leaf stomatal traits of different aged temperate forest stands

Stomata control carbon and water vapor exchange between the leaves and the atmosphere,thus infl uencing photosynthesis and transpiration.Combinations of forest patches with different stand ages are common in nature,however,information of which stomatal traits vary among these stands and how,remains limited.Here,seven different aged forest stands(6,14,25,36,45,55,and 100 years)were selected in typical temperate,mixed broadleaf-conifer forests of northeast China.Stomatal density,size and relative area of 624 species,including the same species in stands of different ages were selected.Stomatal density,size and relative area were distributed log-normally,differing across all species and plant functional groups.Stomatal density ranged from 4.2 to 1276.7 stomata mm^(–2),stomatal size ranged from 66.6 to 8315.7μm^(2),and stomatal relative area 0.1–93.3%.There was a significant negative relationship between density and size at the species and functional group levels,while the relative stomatal area was positively correlated with density and size.Stomatal traits of dominant species were relatively stable across different stand ages but were significantly different for herbs.The results suggest that stomatal traits remain relatively stable for dominant species in natural forests and therefore,spatial variation in stomatal traits across forest patches does not need to be incorporated in future ecological models.

Selective harvesting at rational intervals promotes carbon sequestration in temperate coniferous and broad-leaved mixed forests in China

Evidence-based selective cutting at prescribed intervals as part of good forest management can enhance the carbon sequestration capacity of the forest.The effect of forest management on carbon sequestration has,however,not been quantified.Thus,carbon content of various organs was measured for 323 tree species,247 shrub species,and233 herb species in seven temperate coniferous and broadleaved mixed forests that were subjected to selective cutting with restoration durations of 100,55,45,36,25,14,and6 years to explore dynamic changes in carbon storage.The results showed that biomass carbon allocation in different organs followed a pattern:trunk>root>branch>leaf for all forests.With longer restoration durations,more carbon accumulated in different organs and in soils.Interestingly,when the restoration duration exceeded 50 years,carbon storage in ecosystem was larger than that in primary forests with 100-year cutting intervals,suggesting that a reasonable selective cutting interval can increase forest carbon sequestration.Mean diameter at breast height(DBH)and forest carbon storage were significantly positively correlated,and carbon storage of selectively cut forests exceeded that of primary forests when the stand mean DBH exceeded 15.66 cm.Therefore,mean DBH of forests can be an indicator for combining sustainable forest management and forest carbon sequestration.Additionally,the classic coefficients of 0.45 and 0.50 used to estimate carbon sequestration underestimated values by 2.65%and overestimated by 8.16%,respectively,in comparison with the measured carbon content from different plant organs.

氮添加下温带天然林不同生活型植物叶片和细根的氮-磷分配策略

在中国北方地区迅速增加的氮沉降可能会影响植物的化学计量特征。然而,人们很少关注氮沉降对不同生活型植物(如乔木、灌木和草本)的氮(N)和磷(P)分配策略的影响。本研究评估了不同生活型植物的叶片和细根中N和P的化学计量特征及其异速生长指数在长期N添加下的响应。研究结果表明,与对照相比,在N添加处理下,灌木和草本植物叶片的N和P含量增加,而乔木叶片养分含量的变化不显著。N添加对不同生活型植物细根的N和P含量没有显著影响。对比养分在器官间的分配系数,在3种生活型植物中,N添加处理下植物会将更多的N和P分配到叶片中。此外,对比各器官中N-P的分配关系,乔木的叶片和细根的N-P分配指数与1.0没有显著差异,表现为等速生长模式。灌木和草本植物的N-P含量分配指数显著小于1.0,表现为异速生长模式。与N元素相比,高N处理使灌木和草本植物的叶片分配更多P,但是高N处理对乔木叶片N和P分配影响不显著。植物各器官的N-P分配模式表明,N添加水平改变了植物的养分分配策略,同时这种分配策略在各生活型间表现出显著差异。本研究强调了在评估森林植物的N-P分配策略时,生活型类别的重要性。

中国典型草原植被高度组合的普适性规律与区域差异

详细测定每株植物高度是精细评估草地生态系统中植物群落高度结构的重要方法,并经常用来分析草地植被生长与环境因子关系的普适性和区域差异。本研究在我国青藏高原、内蒙古高原和黄土高原,分别沿降水梯度布设了3条从草甸-草原-荒漠的典型草地生态系统样带。研究结果发现,我国3大高原的草地生态系统植被平均高度为30.38±22.44 cm,其中黄土高原最高,内蒙古高原次之,青藏高原最低。这3个高原草地生态系统的植被聚合高度分布都呈现偏正态分布(0.91,3.60),而且从青藏、内蒙古到黄土高原,该分布逐渐趋于正态(0,3)。然而,在青藏高原的草甸和荒漠生态系统中分别呈现出指数分布和均匀分布。在3大高原中,气候和土壤营养对植被平均高度解释率超过70%,然而对植被聚合高度的解释率最高仅为29%(青藏高原)。从青藏高原、内蒙古高原至黄土高原,植被平均高度对环境综合响应强度逐渐增强,具体表现为气温、降水的影响逐渐增强,而辐射、风速和营养物浓度影响逐渐减弱。我们的研究表明,正态分布是草地植被高度构建的普适性原则,而环境因素的协同作用在不同区域存在差异。

Regeneration pattern analysis of Quercus liaotungensis in a temperate forest using two-dimensional wavelet analysis

This paper introduces the two-dimensional(2D)wavelet analysis as a general interrogative technique for the detection of spatial structure in lattice data.The 2D wavelet analysis detects components of hierarchical structure and displays the locational information of the components.Patches and gaps of different spatial scales in graphical presentation of wavelet coefficients can be linked to the local ecological processes that determine patterns at stand or landscape scales.Derived from the 2D wavelet transform function,the calculation of wavelet variance can reduce the four-dimensional data of wavelet coefficients to a two-dimensional wavelet variance function and quantify the contribution of the given scale to the overall pattern.We illustrate the use of the 2D wavelet analysis by analyzing two simulated patterns and identifying the regeneration pattern of the Quercus liaotungensis in a warm temperate forest in north China.Our results indicate that the recruitment of Q.liaotungensis occurs in an overlapping area between the patch of adult and canopy gap at scales of 45m×45m–70m×70m and 20m×20m–30m×30m.The regeneration pattern of Q.liaotungensis can be mainly ascribed to a trade-off between two ecological processes:recruitment around parent trees and the physiological light requirements of seedlings and saplings.Our results provide a general portrayal of the regeneration pattern for the dispersal-limited and shade-intolerant Quercus species.We find that the two-dimensional wavelet analysis efficiently characterizes the scale-specific pattern of Q.liaotungensis at different life-history stages.