Effects of the lack of forest management on spatiotemporal dynamics of a subalpine Pinus cembra forest

Knowledge about the stand structure and dynamics of subalpine forests is crucial to preserve their multifunctionality. In the present study, we reconstructed the spatiotemporal dynamics of a subalpine Pinus cembra forest in the eastern Italian Alps in response to natural disturbances and forest management. We adopted a concurrent point pattern, dendroecological and growth dominance (GD) analysis. We mapped and measured all trees of Pinus cembra and Larix decidua in a 1?ha plot. We analyzed intra- and interspecific spatial patterns and spatial autocorrelation of tree size and age. We explored establishment dynamics and shifts in competition by analyzing growth suppression/release patterns and GD trends. Results showed a clumped, uneven-aged, multilayered structure where pine was dominant. The synergic action of ecological and human-induced factors is discussed to explain the prevalence of pine over time. Spatial pattern and autocorrelation analyses suggest a different colonization strategy of the two species, in which pine established after small-scale perturbations and experienced a stronger inter- and intra-specific competition. The interruption of tree establishment and shift in GD toward large trees resulting from the lack of forest management are the most important findings of this research. This highlights the importance of an active management to avoid the homogenization of the forest structure that is generally associated with a reduction in biodiversity and protective ability of forests.     

Soil properties and tree growth at medieval ridge and furrow sites in Brandenburg,northeastern Germany

Background

Ridge and furrow (RIFU) systems and associated soils are a widespread legacy of medieval agriculture, are archives of historical land use, and might affect recent ecosystems. Open questions about RIFU formation and potential legacy effects still exist, especially related to physical soil properties.

Aims

Our aims were (1) to characterize the soil properties of RIFU soils and (2) to compare the drought sensitivity and the growth resistance in extremely dry years of trees growing on ridges and furrows, respectively.

Methods

We studied soil physical (bulk density, saturated soil hydraulic conductivity, and texture) and chemical (soil pH, soil organic matter, and nitrogen content) properties and the climate sensitivity of tree growth on RIFU systems for three study sites in Prignitz, Germany.

Results

RIFU systems showed a high spatial heterogeneity of soil stratigraphy due to ridge construction and increased accumulation of soil moisture and organic matter in furrows due to post-abandonment pedogenesis. Slight spatial differences in soil physical properties were found, with increased air capacity in ridge soils and higher available water contents in furrow soils. No differences in drought sensitivity were observed for trees growing on ridges and furrows, except for a wet site, where trees in furrows showed a higher sensitivity. Resistance in dry years tended to be similar or increase from furrows to ridges.

Conclusions

The results reflect a spatial differentiation of stratigraphy and post-abandonment pedogenesis on abandoned RIFU systems and suggest an adaption to different moisture conditions through RIFU construction. Differences in drought sensitivity of tree growth with relative land surface could only be detected for one of the three sites, where trees were found to be less drought sensitive on ridges.     

A refined view on the “Green lie”: Forest structure and composition succeeding early twentieth century selective logging in SE Norway

Abstract

Logging exceeded growth and timber trees were sparse in Norwegian forests in the early 1900s. Still, the forest canopy was lush green and characterised by large tree-crowns. This situation was referred to as the “Green lie” and was advocated by foresters throughout Scandinavia as an argument in favour of forestry practices based on clear-felling. Here we examine effects of past selective loggings on forest structure and composition in a spruce forest landscape using dendroecology and historical records. Our results show that forests that were selectively logged up to the early 1900s could be structurally heterogeneous with multi-layered canopies, varying degree of openness and continuous presence of old trees across different spatial scales. Because the past forests were not clear-felled, a diverse forest structure in terms of tree species composition and age and diameter distribution was maintained over time, which could enable forest-dwelling species to persist during the early phase following the loggings in the past. This is in sharp contrast to the situation in most modern managed forest landscapes in Scandinavia. A better understanding of the link between loggings in the past- and present-day forest structure and diversity will contribute to rewarding discussions on forestry methods for the future.     

峨眉山不同海拔冷杉径向生长对气候变化的响应

【目的】研究峨眉山不同海拔冷杉Abies fabri径向生长对气候变化的响应规律。【方法】以冷杉为研究对象,用树轮生态学的方法对峨眉山不同海拔的冷杉进行年轮采样、处理与分析,比较不同海拔冷杉径向生长特征及其与各气候因子之间的关系。【结果】年表统计数据表明,4个年表均具有较高的可靠性,可以用于树木生长与气候关系的研究。不同海拔冷杉径向生长与气候的关系具有明显的海拔差异,海拔2 400 m处冷杉径向生长与当年7月的温度呈显著正相关;海拔2 800 m处冷杉径向生长与当年4-9月的帕尔默干旱指数(PDSI)呈显著正相关;海拔2 900 m处冷杉径向生长与前一年9月和当年4月的温度呈显著负相关,与当年1-9月的PDSI均呈显著正相关;海拔3 000 m处冷杉径向生长和当年3-4月温度呈显著负相关,与当年6-7月的PDSI和当年4月平均相对湿度呈显著正相关。【结论】峨眉山高海拔的冷杉包含有更多的环境信息,对气候变化的响应也更为敏感;高海拔区域冷杉径向生长受到水分的强烈限制,而低海拔区域冷杉径向生长主要受温度影响;冷杉衰亡与气候因子的变化密切相关,随着区域气候的变暖,高海拔地区冷杉可能会进一步衰退。该研究揭示了峨眉山不同海拔冷杉生长动态及其对气候变化响应的敏感性差异,为全球气候变化背景下冷杉林的保护与适应性管理提供科学参考。     

树轮生态学研究进展

树轮生态学是现代树轮年代学的重要分支,在全球气候变化引起的资源、环境等压力日益增大的今天,越来越显示出树轮生态学研究的理论和现实意义。文中简要概述了树轮分析在森林干扰、群落动态、森林结构、林分更新方式以及高山林线研究方面的进展。树轮生态学将对我国树木个体生长情况和群落动态的研究,虫灾、火灾、风灾和森林动态的关系以及森林管理相关的研究发挥重要作用。