Trees and shrubs as a component of buffer zones: advantages and disadvantages in P-retention

Trees and shrubs are potential components for construction of buffer zones, especially for reducing phosphorus levels in soil. Woody species appear to be less efficient in capturing nutrients from overland flow, at least outside the growing season. Tree seedlings prevent effective mowing and removal of hay, which may lead to an accumulation of dead hay on the zone. Therefore woody species should mainly be used in places where yearly mowing and removal of hay is not feasible

The impact of tree crops and temperature on the timing of frugivorous bird migration

Migration has evolved to tackle temporal changes in availability of resources. Climate change has been shown to affect the migration dates of species, which raises the question of whether the variation in the timing of migration is climate or resource dependent? The relative importance of temperature and availability of food as drivers of migration behaviour during both spring and autumn seasons has been poorly studied. Here, we investigated these patterns in frugivorous and granivorous birds (hereafter frugivorous) that are assumed to postpone their autumn migration when there is plenty of food available, which may also advance upcoming spring migration. On the other hand, especially spring migration dates have been negatively connected with increasing temperatures. We tested whether the autumn and spring migration dates of eleven common frugivorous birds depended on the crop size of trees or ambient temperatures using 29 years of data in Finland. The increased crop sizes of trees delayed autumn migration dates; whereas, autumn temperature did not show a significant connection. We also observed a temporal trend towards later departure. Increasing temperature and crop sizes advanced spring arrival dates. Our results support the hypothesis that the timing of autumn migration in the frugivorous birds depends on the availability of food and is weakly connected with the variation in temperature. Importantly, crop size can have carry-over effects and affect the timing of spring arrival possibly because birds have overwintered closer to the breeding grounds after an abundant crop year.Peer reviewe

Contemporary mature forest cover does not explain the persistence of Capercaillie (Tetrao urogallus) lekking areas in Finland

Capercaillie (Tetrao urogallus) has traditionally been considered an old forest-dependent species. The lekking sites especially,were thought to be located in older forests. We studied the persistence of Capercaillie lekking areas in relation tomature forest cover at three study areas in Finland (southwestern, SW; central, CE; and northern, NO). Atotal of 381 leks were inspected twice at intervals of 10-30 years and were classified as either persisting or vacated. We defined mature forest as forest with > 152 m 3ha -1 of timber (SW and CE Finland) or > 68 m 3ha -1 of timber (NO Finland). We measured mature-forest cover within two radii around the leks (1,000 and 3,000m) using satellite image-based forest inventories, and performed logistic regression analyses on these data. We did not find significant trends between mature-forest cover and lekking-area persistence in any of the study areas. However, the proportion of mature forestsmay have already been too low to detect the significance of this factor. The only significant factor affecting the lekking-site persistence was time lag between surveys. The positive relationship between the time lag and lekking-site persistence in CE and NO Finland may be due to the partial recovery of the landscapes in terms of forest regrowth, from extensive clear-cut harvesting in the 1950s and 1960s. In SWFinland, the relationship was negative, possibly indicatingmore permanent changes in the landscape that is currently characterized by human settlements and agricultural areas. We conclude that in present-day Finland, the area covered by mature forest ismost likely too scarce to explain the lekking-area persistence ofCapercaillie. An alternative explanation is that some important structural characteristics are missing from the current mature forests

Persistence of Capercaillie (Tetrao urogallus) lekking areas depends on forest cover and fine-grain fragmentation of boreal forest landscapes

Peer reviewe

The impact of tree crops and temperature on the timing of frugivorous bird migration

Migration has evolved to tackle temporal changes in availability of resources. Climate change has been shown to affect the migration dates of species, which raises the question of whether the variation in the timing of migration is climate or resource dependent? The relative importance of temperature and availability of food as drivers of migration behaviour during both spring and autumn seasons has been poorly studied. Here, we investigated these patterns in frugivorous and granivorous birds (hereafter frugivorous) that are assumed to postpone their autumn migration when there is plenty of food available, which may also advance upcoming spring migration. On the other hand, especially spring migration dates have been negatively connected with increasing temperatures. We tested whether the autumn and spring migration dates of eleven common frugivorous birds depended on the crop size of trees or ambient temperatures using 29 years of data in Finland. The increased crop sizes of trees delayed autumn migration dates; whereas, autumn temperature did not show a significant connection. We also observed a temporal trend towards later departure. Increasing temperature and crop sizes advanced spring arrival dates. Our results support the hypothesis that the timing of autumn migration in the frugivorous birds depends on the availability of food and is weakly connected with the variation in temperature. Importantly, crop size can have carry-over effects and affect the timing of spring arrival possibly because birds have overwintered closer to the breeding grounds after an abundant crop year

Different germination success may explain lower species richness of herbaceous vegetation below non-native than native shrubs

Mechanisms by which invasive species affect native communities have been intensively studied. Invasive plants may influence other species through competition, altered ecosystem processes, or other pathways. It has been suggested that allelochemical interference is the key mechanism explaining a lower species richness of herbaceous plants below non-native than native shrubs. We studied plant recruitment from seeds sown inside and outside patches formed by Sorbaria sorbifolia, a shrub non-native to Finland, and a native shrub Rubus idaeus. Recruitment of seedlings was lower below non-native than native shrubs, in contrast to recruitment outside the shrub patches. Biotic filtering of subdominant plants was a stepwise process affected by the difference between non-native and native shrubs. Our results suggest that allelochemicals released by non-native species may be responsible for this difference. They thus give support to the hypothesis emphasizing the importance of allelopathy in the invasion of non-native plants. The slow and stepwise action of biotic filtering cautions against defining plant community membership merely based on the presence of seedlings.</p