Microtopography and the Properties of Residual Peat Are Convenient Indicators for Restoration Planning of Abandoned Extracted Peatlands

The natural recovery of vegetation on abandoned peat extraction areas lasts for decades and the result of restoration succession can be unpredictable. The aim of the study was to specify environmental factors that affect the formation of the pioneer stages of mire communities and, therefore, be helpful in the prediction of the resulting ecosystem properties. We used the national inventory data from 64 milled peatlands in Estonia, distributed over the region of 300 × 200 km. This is the first national‐scale statistical evaluation of abandoned extracted peatlands. During surveys, vascular plants, bryophytes, and residual peat properties were recorded on three microtopographic forms: flats, ditch margins, and ditches. The microtopography was the main factor distinguishing the composition of plant communities on flats and ditches, while ditch margins resembled flats. The extracted indicator species suggested two successional pathways, toward fen or raised bog community. A single indicator trait—the depth of residual peat, which combines the information about peat properties (e.g. pH, ash content, and trophicity status), predicted the plant community succession in microtopographic habitats. We suggest that peatland management plans about the cost‐efficient restoration of abandoned peat mining areas should consider properties of residual peat layer as the baseline indicator: milled peatfields with thin (<2.3 m) and well‐decomposed residual peat should be restored toward fen vegetation types, whereas sites with thick (>2.3 m) and less decomposed residual peat layer should be restored toward transitional mires or raised bogs. Specific methodological suggestions are provided .     

Magnitude and drivers of plant diversity loss differ between spatial scales in Scania,Sweden 1957–2021

Questions

Changed land use, nitrogen deposition, climate change, and the spread of non-native species have repeatedly been reported as the main drivers of recent floristic changes in northern Europe. However, the relevance of the geographical scale at which floristic changes are observed is less well understood and it has only rarely been possible to quantify biodiversity loss. Therefore, we assessed changes in species richness, species composition and mean ecological indicator values (EIVs) at three nested geographic scales during two different time periods, each ca 30 years, since the mid-1900s.

Location

Two parishes in central Scania, southernmost Sweden.

Methods

We analyzed species presence/absence data from three inventories at ca 30-year intervals over 1957–2021 and three geographic scales (157 m², ca 7 km² and ca 45 km²) to document temporal trends and differences between geographic scales in terms of species richness, species composition and mean EIVs.

Results

We found shifts in species composition across all geographical scales. However, the magnitude of biodiversity loss and the main drivers of these changes were scale-dependent. At the smallest spatial scale, we saw a dramatic loss of plant biodiversity with local species richness in 2021 being only 48% of that of 1960. In contrast, at the larger geographic scales no significant changes in species richness were observed because species losses were compensated for by gains of predominantly non-native species, which made up at least 78% of the new species richness. At the smallest spatial scale, changed land use (ceased grazing/mowing and intensified forestry) appeared as the main driver, while an increasing proportion of non-native species, as well as climatic changes and increasing nitrogen loads appeared relatively more important at larger geographic scales.

Conclusion

Our results highlight the precarious situation for biodiversity in the region and at the same time the fundamental importance of geographic scale in studies of biodiversity change. Both the magnitude and drivers of changes may differ depending on the geographic scale and must be considered also when previously published studies are interpreted.     

The detection and attribution of extreme reductions in vegetation growth across the global land surface

Negative extreme anomalies in vegetation growth (NEGs) usually indicate severely impaired ecosystem services. These NEGs can result from diverse natural and anthropogenic causes, especially climate extremes (CEs). However, the relationship between NEGs and many types of CEs remains largely unknown at regional and global scales. Here, with satellite-derived vegetation index data and supporting tree-ring chronologies, we identify periods of NEGs from 1981 to 2015 across the global land surface. We find 70% of these NEGs are attributable to five types of CEs and their combinations, with compound CEs generally more detrimental than individual ones. More importantly, we find that dominant CEs for NEGs vary by biome and region. Specifically, cold and/or wet extremes dominate NEGs in temperate mountains and high latitudes, whereas soil drought and related compound extremes are primarily responsible for NEGs in wet tropical, arid and semi-arid regions. Key characteristics (e.g., the frequency, intensity and duration of CEs, and the vulnerability of vegetation) that determine the dominance of CEs are also region- and biome-dependent. For example, in the wet tropics, dominant individual CEs have both higher intensity and longer duration than non-dominant ones. However, in the dry tropics and some temperate regions, a longer CE duration is more important than higher intensity. Our work provides the first global accounting of the attribution of NEGs to diverse climatic extremes. Our analysis has important implications for developing climate-specific disaster prevention and mitigation plans among different regions of the globe in a changing climate.     

Seasonal changes in net photosynthesis rates and photosynthetic capacity in leaves of Cistus salvifolius,a European mediterranean semi-deciduous shrub

Summary During five different periods between Nov. 1982 and Aug. 1983, the diurnal patterns exhibited in photosynthetic CO₂ uptake and stomatal conductance were observed under natural conditions on twigs of Cistus salvifolius, a Mediterranean semi-deciduous shrub which retains a significant proportion of its leaves through the summer drought. During the same periods, net photosynthesis at saturating CO₂ partial pressure was measured on the same twigs as a function of irradiance at different temperatures. From these data, photosynthetic capacity, defined here as the CO₂- and light-saturated net photosynthesis rate, was obtained as a function of leaf temperature. C. salvifolius is a winter growing species, shoot growth being initiated in Nov. and continuing through May. Photosynthetic capacity was quite high in Nov., March and June, exceeding 40 mol m^-2 s^-1 at optimum temperature. In Dec., photosynthetic capacity was somewhat reduced, perhaps due to low night-time temperatures (<5°C) during the measurement period. In Aug., capacity in oversummering shoots at optimum temperature fell to less than 8 mol m^-2 s^-1, due to water trees and perhaps leaf aging. Seasonal changes in maximal photosynthetic rates under ambient conditions were similar, and like those found in co-occurring evergreen sclerophylls. Like the evergreens, Cistus demonstrated considerable stomatal control of transpirational water loss, particularly in oversummering leaves. During each measurement period except Aug. when capacity was quite low, the maximum rates of net photosynthesis measured under ambient conditions were less than half the measured photosynthetic capacities at comparable temperatures, suggesting an apparent excess nitrogen investment in the photosynthetic apparatus.     

黄土高寒区典型植被类型土壤入渗特征及其影响因素

为了研究黄土高寒区典型植被在不同坡位下土壤入渗性能差异及其影响因素,采用恒定水头法测定了不同植被类型的土壤入渗过程,并分析了土壤孔隙状况、机械组成、水稳性团聚体等与渗透速率的相关性。结果表明:(1)初渗速率和稳渗速率均表现为青海云杉>祁连圆柏>华北落叶松>荒草地,且差异性显著;同一植被类型的土壤入渗速率沿坡面向下逐渐增大,但差异性不显著;(2)对不同植被类型的土壤入渗过程模拟发现Horton模型拟合效果最好,决定系数均在0.8以上,通用经验模型拟合精度较差,决定系数在0.614—0.982之间;(3)土壤入渗性能与孔隙状况、水稳性团聚体质量分数、有机质含量均有极显著相关性;>0.25 mm团聚体质量分数是影响稳渗速率的主要决策因素;总孔隙度是影响初渗速率的最主要的决策因素,而毛管孔隙度是主要的限制因子。为高寒地区土壤入渗模拟以及植被配置等提供了科学依据。     

内蒙古高寒露天煤矿排土场植被恢复研究

探究不同恢复年限对于露天煤矿植被群落变化和植物个体生长的影响,进一步加强生态环境保护与生态修复治理措施。以内蒙古高寒露天煤矿排土场恢复4年(2018-2021年)的植物群落为研究对象,采用样方调查方法,对样地内植物群落进行调查,设置草本样方(1 m×1 m)和灌木样方(5 m×5 m),记录植物物种组成、高度及盖度等指标,计算Shannon-Wiener多样性指数、Simpon指数、Pielou均匀度指数和物种重要值。探讨不同的恢复年限植物群落变化特征和优势植物的养分吸收,为矿区人工植被恢复提供科学依据。结果表明:(1)矿区排土场植物群落物种数、生物量和群落多样性均随着恢复年限的增加而显著增加。总物种数从恢复第1年的16种增加到恢复第4年的31种,主要是由于非人工种植植物从6种增加到19种导致,特别是在恢复第2年增加显著,然后趋于平稳,这说明恢复第2年是物种增加关键的时期;(2)随着恢复年限的增加,生物量和多样性指数显著增加;矿区植被优势物种多以禾本科披碱草(Elymus dahuricus)、无芒雀麦(Bromus inermis);豆科植物苜蓿(Medicago sativa)、草木樨(Melilotus officinalis)、沙打旺(Astragalus adsurgens)、锦鸡儿(Caragana sinica);菊科植物大籽蒿(Artemisia sieversiana);十字花科油菜(Brassica napus)和胡颓子科沙棘(Hippophae rhamnoides)为主。(3)比较不同优势植物叶片、茎和根的氮(N)、磷(P)和钾(K)含量发现,草本优势种中菊科和豆科植物显著高于禾本科植物。灌木优势种中沙棘茎的N含量和P含量显著高于锦鸡儿。研究认为,在排土场植被恢复初期(4年)的物种选择上,豆科植物和菊科植物是草本植物首选的先锋物种,另外,沙棘是灌木首选的物种。     

AN ASSESSMENT OF THE POTENTIAL IMPACT OF ALIEN INVASIVE VEGETATION ON THE GEOMORPHOLOGY OF RIVER CHANNELS IN SOUTH AFRICA

Summary

Invasion of the riparian zone by alien vegetation is recognised as a serious problem in many areas of South Africa. Vegetation is a dynamic component of river channels. It is an important control variable affecting channel form whereas the flow and sediment regime influences vegetation growth. Wherever alien vegetation invades the riparian zone it can be expected that there will be some impact on the physical structure of the riparian habitat. This paper reviews the effect of riparian vegetation on channel processes and channel form and discusses the implications of the invasion of riparian zones by alien vegetation. Woody species in particular are seen as having a significant potential for inducing channel modification, whilst their removal could lead to significant channel instability and mobilisation of sediment. The need for further research into the impact of alien vegetation on the geomorphology of South African river channels is stressed.