Impact of Climate on Agriculture and Forestry in Europe

Temperature, incoming solar radiation, water and nutrient availability are the main factors that generally determine agriculture production. Biological systems are based primarily on photosynthesis, and thus dependent on incoming radiation. The potential for production determined by the radiation is greatly modified by temperature and rainfall. The main effect of temperature is to control the duration of the growth period (Long and Woodward, 1988). Moreover, also other processes linked with the accumulation of dry matter (leaf area expansion, photosynthesis, respiration, evapotranspiration, etc.) are affected by temperature. Rainfall and soil water availability may affect the duration of growth through leaf area duration and the photosynthetic efficiency through stomatal closure.

Also, animal behaviour and production are affected by these factors. These like man are homoeotherms, thus they have a comfort zone within which the climatic factors produce no stress on metabolism. When ambient heating exceeds or is insufficient to maintain temperature within this zone, cold and heat stresses are produced. These stresses may be mediated by low temperatures, precipitation and high wind speeds, or by high temperatures and droughts, respectively. Both stresses cause lower food and higher water intake, which results in lower general performance (Fuquay, 1989). Moreover climatic factors have indirect effects on animal production (loss in weight and condition) via decreases in quality and quantity of forage.

These general climatic constraints on agricultural production are modified by local climatic constraints. In Northern countries the length of growing season, late spring and early autumn frost and solar radiation availability are typical climatic constraints. In these environments the duration of the growing season (frost or snow-free period) limits the productivity of crops. For example, in Germany the growing season is 1-3 months longer than in Scandinavian countries (Mela, 1996). The short growing season is the main cause of the lower cereal grain yields in the

Nordic countries. Moreover, night frosts in the late spring or early autumn increase the agricultural risk in these environments.

The wet conditions along the Atlantic coast and in the mountainous regions causing cold and rainy summers, limit the availability of solar radiation and cause yield and quality losses of many arable crops. This is the main reason for the low cereal area on the British Isles and Alpine countries compared with other regions.

In the Mediterranean countries cereal yields are limited by water availability, heat stress and short duration of the grain filling period. Cereals are therefore less important in this region. Permanent crops (olive, grapevine, fruit trees, etc.) are important here. These crops are affected by extreme weather events (such as hail and storms) which can reduce or completely destroy yield. Irrigation is important for crop production in many Mediterranean countries due to high evapotranspiration and restricted rainfall.

The continental climate of eastern Europe (from central Poland and eastwards), causing drier conditions and greater amplitude of the annual temperature cycle, limits the range of crops that can be grown. The most productive regions in Europe in terms of climate and soils are located in the great European plain stretching from Southeast England through France, Benelux and Germany into Poland. There are additional lowland regions, e.g. Hungarian plains, where equally favourable conditions are available.

The range of European forests is limited primarily by climate, either through moisture availability or through temperature (both absolute amounts and seasonal distributions) (Berninger, 1997). Some forests (particularly in the North) are also nutrient-limited. The structure and composition of many forests is further influenced by the natural disturbance regime (fire, insects, wind-throw, etc.). Most European forests are managed for one or several purposes, such as timber production, water resources, or recreation. This management has reduced forest area or strongly modified forest structure in most of Europe, and presently existing forests often consist of species that are different from those that would occur naturally.

Examining in detail the influence of climate on European forests, the existing south-north climate gradient implies decreasing temperature and increasing humidity with decreasing water limitation and increasing temperature limitation for forests. Whilst, on the west-east climate gradient, the maritime climate turns to the continental one with decreasing humidity and increasing water limitation for forests. In line with these gradients over Europe, and as has been already reported previously, the forests may be divided into Boreal forests (boreal zone), Atlantic forests (humid temperate forests), Continental forests (dry temperate forests) and Mediterranean forests.

In the Boreal forest, the growth and productivity are manly limited by winter temperatures that determine the length of the growing season through the duration of snow cover and soil frost. In Atlantic forests, strong winds play an important role in determining the forest productivity through their effects on evapotranspiration and then water availability. In the southern parts of the Atlantic forests, in the Continental and Mediterranean forests the summer precipitations are the main constraint factor of forest growth and productivity through their role in determining the frequency of droughts.

0 0

Post a comment