Pine Drying in Kashmir

Pine drying in a serious ecological concern in Kashmir especially with the increasing impact of climate change. This can potentially impact the loss of carbon sink, reduced biodiversity, increase in forest fires besides loss of soil and nutrients through erosion. Very recently a conspicuous change in coloration of Pine trees has been witnessed across the forests of Kashmir. The affected forest patches are, however, dominated by Pinus wallichiana (Himalayan Blue Pine) with Cedrusdeodara (Himalayan Cedar or Deodar) in the mixed form. It is notable that such incidences of pre-mature needle browning have been observed in Pine trees rather than Deodar coexisting in the same forest.

Once we hear about such incidences there are several thoughts that instantly arise without bothering to have a look at the visual symptoms. These may include root rot, leaf blight or any biological infestation of fungus or insect. However the prevailing climatic conditions from past few years has a different story to tell correlating the problem with consistently low precipitation especially in the winter season. During winter the entire region is supposed to receive adequate snowfall owing to the western disturbances. The accumulated snow with gradual melting acts as a perennial source of moisture available over a considerable period. The consistent decrease in snowfall during the peak winter periods has led to overall deficit in snow reserves leading to prolonged dryness in the region.

The problem get further aggravated by the fact that pine tree sheds copious amounts of pine needles, which due to its toxicity is neither consumed by animals nor decomposed by microbes to convert it into humus and soil. Any amount of rain is not enough to replenish this moisture deficit as the accumulated needles create an impermeable plastic sheet accelerating runoff while impacting the infiltration process.

Furthermore, conifer species in general originate from harsh xeric or cold habitats are characterised by drought resistance adopting a slow growth strategy with small tracheids, low specific leaf area and long leaf lifespan. However, this drought tolerance character is better adapted in Cedar than in Pine due to its anatomical and morphological features. Pinu swallichiana with its longer needle length 12–18 cm is longer than Cedrus deodara (2.5 to 5 cm) maximize photosynthesis. Additionally it has higher number of resin canals (6-8 per needle) that provides protection from herbivory and environmental stress.

However in Cedrus deodara, shorter and stiffer needles reduce water loss in drier environments. Fewer resin canals in Cedar (2-5 per needle) indicate better water conservation. Understanding root system of both the species suggest that P. wallichiana's shallower root system may lead to quicker depletion of surface soil moisture, potentially affecting groundwater recharge. In contrast, C. deodara's deeper roots allow access to subsoil moisture, which may contribute to better soil water retention and recharge.

Canopy structure and interception supports the concept of differential water recharging abilities under the two dominant canopy stands. P. Wallichiana has a dense needle canopy, leading to higher interception of rainfall. A significant portion of intercepted water evaporates before reaching the soil. C. deodara has relatively open needle arrangements, allowing more precipitation to penetrate through to the soil.

In view of such observations, the prevalent Pine drying may indicate winter burn due to drought stress evident from dry winter spells from past few years. The observations that can further support this conclusion is when the browning is first noticeable in top branches as a measure towards rationing water due to limited uptake.  Existence of drought stress is further supported by the fact that Pinus walliahiana is a moderate to low drought tolerant species with moderate depth root system compared to Cedrus deodara which is a highly drought tolerant species due to deep and extensive root system. Further the needles in Cedurus deodara lose less moisture comparatively being thicker and waxy than Pinus wallichinana.

Drought stressed Pinus wallichiana patches have the ability to recover after optimum precipitation only if the severity of damage is mild to moderate and if favourable moisture conditions continue in the forthcoming season. Needle regrowth may take several months or even a year in severely impacted trees. If the symptoms persist even after the rainfall/new growing season, the trees are unlikely to recover. A team from SKUAST-K recently undertook a diagnostic visit to different forest locations impacted by this problem. A detailed research paper about the research finding will be published in a reputed journal soon. A general awareness regarding the problem is of paramount importance in view of the prevailing climate change. It becomes our collective responsibility to mitigate its impact by reducing personal carbon footprints.

The author is head Division of Natural Resource Management, Faculty of Forestry, SKUAST-K