Vascular plant species count in a wet forest in the Chocó area on the Pacific coast of Colombia

The total number of vascular plant species was counted and growth form distribution was studied in the Chocó area on the Pacific coast of Colombia, in two transects 400×10m and ten transects 2×50m, for a total sampled area of 0.9ha. The species count of the ten transects (442 species in 0.1ha) appears to be the highest number of species recorded with this methodology. There were 970 species for the total area (0.9ha). Ninety to ninety-five percent of the species were under 10cm dbh and 70–86% under 2.5cm dbh, epiphytes and small trees and treelets 10cm dbh being the most diverse growth forms. The most species-rich families and genera were those represented by herbaceous plants and treelets. Individuals were counted only in the ten 2 × 50 m transects (0.1 ha), where 4459 individuals were found. Palms and ferns were the most abundant growth forms. Arguments are presented against the way diversity is usually measured. Recommendations are made to include other growth forms besides trees when assessing alpha diversity for conservation purposes.     

Increased performance of Cirsium arvense from the invasive range

The Evolution of Increased Competitive Ability (EICA) hypothesis suggests that plants from the invasive range should perform better than plants of the same species from the native range. To properly test this, we need to compare growth of plants from the two ranges in a common environment. Ideally, all the natural enemies should be excluded, to make sure that the differences are not due to different response of plants from the two ranges to the natural enemies. We used the above design to examine the difference in growth and reproduction in Cirsium arvense plants from the invasive (North America) and native range (Europe). To account for possible differences within the ranges, we used plants from two regions, separated by at least 1000 km, in each range. Because the higher performance of species from the invasive range can be caused by their higher ability to acquire resources we compared growth of the plants in two different nutrient levels. The results indicate that plants from the invasive range are larger in most size parameters as well as parameters more closely related to fitness. For aboveground biomass, the response of plants from the invasive range to nutrient addition was weaker than that of plants from the native range and the difference between the ranges was stronger in the nutrient poor substrate. The results are in agreement with the EICA hypothesis and suggest that plants from the invasive range have higher ability to use resources and are thus able to perform well also in nutrient poor conditions.     

Climate-related differences in the dominance of submerged macrophytes in shallow lakes

It has been suggested that shallow lakes in warm climates have a higher probability of being turbid, rather than macrophyte dominated, compared with lakes in cooler climates, but little field evidence exists to evaluate this hypothesis. We analyzed data from 782 lake years in different climate zones in North America, South America, and Europe. We tested if systematic differences exist in the relationship between the abundance of submerged macrophytes and environmental factors such as lake depth and nutrient levels. In the pooled dataset the proportion of lakes with substantial submerged macrophyte coverage (> 30% of the lake area) decreased in a sigmoidal way with increasing total phosphorus (TP) concentration, falling most steeply between 0.05 and 0.2 mg L⁻¹. Substantial submerged macrophyte coverage was also rare in lakes with total nitrogen (TN) concentrations above 1–2 mg L⁻¹, except for lakes with very low TP concentrations where macrophytes remain abundant until higher TN concentrations. The deviance reduction of logistic regression models predicting macrophyte coverage from nutrients and water depth was generally low, and notably lowest in tropical and subtropical regions (Brazil, Uruguay, and Florida), suggesting that macrophyte coverage was strongly influenced by other factors. The maximum TP concentration allowing substantial submerged macrophyte coverage was clearly higher in cold regions with more frost days. This is in agreement with other studies which found a large influence of ice cover duration on shallow lakes' ecology through partial fish kills that may improve light conditions for submerged macrophytes by cascading effects on periphyton and phytoplankton. Our findings suggest that, in regions where climatic warming is projected to lead to fewer frost days, macrophyte cover will decrease unless the nutrient levels are lowered.     

海南省国家重点保护野生植物分布特征及所依托植被类型研究（附表）

为揭示海南省国家重点保护野生植物的分布状况及生境特征,该文基于2021版《国家重点保护野生植物名录》,通过数据整理和野外调查等方法,对海南省国家重点保护野生植物的分布特征及所依托植被类型开展研究.结果表明:(1)海南省分布的国家重点保护野生植物共53科83属173种,在全国各省(区、市)中物种数位列第五,物种密度排在首位(基于当前公布的国家重点保护野生植物数据).(2)海南省19个市(县)行政区均有国家重点保护野生植物分布,中部及南部市(县)分布的物种数远大于北部市(县),其中物种丰富度最大的为昌江黎族自治县(75种),物种密度最高的为陵水黎族自治县(0.604 5 ind.·km-2);海南省国家重点保护野生植物的物种数在海拔(altitude,Alt)范围为0～1 867 m的9个区间(梯度值200 m)内均有分布,并随着海拔的升高呈微降-骤升-缓降的趋势,物种数最多的海拔区间为800 m≤Alt＜1 000 m及1 000m Alt＜1 200 m,均有81种,最少的海拔区间为1 600 m≤Alt＜1 867 m,仅9种.(3)海南省国家重点保护野生植物生境复杂,共依托于11种植被类型,物种丰富度最高的为低地雨林(114种),其次是山地雨林(105种),最低的是半红树林(1种);物种受干扰程度最大的植被类型是淡水湿生草丛,其次是低地雨林,最小的是山地云雾林.该研究结果为海南省国家重点保护野生植物的保护和利用提供了科学参考.